CBlniPiiLBDOTi 3S'37ilinil6l|)h SI. CHICAGO, CORNELL UNIVERSITY. THE Bosnian ^. Wlixm^v IDibiravg THE GIFT OF ROSWELL P. FLOWER FOR THE USE OF THE N. Y. STATE VETERINARY COLLEGE. 1897 Cornell University Ubrary QP 34.B47 Text-book of Physiology, general ^^^^^^ 3 1924 001 038 763 All books are subject to recall after two weeks. Olln/Kroch Library DATE DUE IntedibiA- Coin PRINTED IN U.S.A The original of tliis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924001038763 TEXT-BOOK OF PHYSIOLOGY. TEXT-BOOK PHYSIOLOGY, lK;t^\ GENERAL, SPECIAL, AND PRACTIOAL>% v^v '''' JOHN HUGHES BENNETT, M.D., F.R.S.E., PBOFESBOB OF THE INSTITUTES OF UEBICINE OB PHTBIOLOGY, AND 8ENI0B PBOFESSOB OF CLINICAL UEBIOINB IN THE VNITEBSIT7 OF EDINBUBa]^ ; Late President of fcha Medioo-Chirurgioal Society of Edinburgh ; Honorary Member and Emeritus President of the Royal Medical Society of Edinburgh, Fellow or Member of various Scientific Societies in London, Dublin, St. Andrews, New York, Philadelphia. Boston, Paris, Brussels, Vienna, Berlin, St. Petersburg, Jena, Stockholm, Athens, Bada-Pesth, Copenhagen, Amsterdam, etc., etc. WITH TWENTY-ONE PHOTO-LITHOORAPHIG PLATES. A^^ .:-'^^' PH ila.de lph ia: J. B. LIPPINCOTT & CO. 18 7 3. QP Wo I H^ PREFACE. 'KING ih.6 winter session 1841-42, I, for tlie first time, ire a course of lectures on Histology, in Edinburgh, and I following year, Mr Qiiekett gave a similar course in ttdon. In- 1848, when appointed to the chair of th6 Stitutes of Medicine in this University, I hegan to teach ysiology systematically, and have dote so every winter ce then, while the lectures on Histology were delivered [y in summer. In 1862, I was enabled to institute irses of instruction in Praptical Physiology, as they are present taught both during the winter and summer sions, having obtained at that time a new laboratory, nished with aU the modern instruments of precision jossary for the purpose. [n 1858, under thetitle of " Outlines of Physiology," I blished an extension of the article I contributed to the t edition of the EnoyeloptBdia Britannica. The rapid laustion of a large edition of this little work, demon- ated the great demand that existed for a short treatise the subject. But I have hitherto hesitated to write a ;t-book, apprehensive that the extensive field, theoretical I practical, now occupied by the science, would render I work too bulky. Thus a knowledge of analytical ;anic chemistry and of practical physics is at present nitted to be essential for comprehending and manipu- ing the instruments which in recent times have so largely isted in advancing the subject — a knowledge not re- vi PREFACE. quired in the medical curriculum. In yielding, therefore, at leijgth to the earnest and repeated, requests of my classes to furnish them with a hook that would aid their studies, it has to be seen how far the attempt to condense in this yolume so comprehensive a science will satisfy the expec- tations and meet the requirements of the physiological student. The illustrative plates contain figures which have been chosen simply on the score of what has appeared to me their utility. Like the text, they are compressed into the smallest possible space, and have been produced by photo- lithography, in order to diminish cost. Some of them, in consequence, although sufficiently characteristic, may not be so perfect as good woodcuts, but the latter would have seriously increased the price of the book. I have to thank my assistant, Dr McKendrick, for the valuable aid he has rendered me throughout the progress of the work, but more especially in the sections on the Physical Properties of the Tissues, on Practical Chemical Physiology, and X)n Practical Experimental Physiology, which were entirely written by him. J. Hughes Benitett. Edinburgh, November 5. 187^. CONTENTS. PAGE INTRODUCTION .1 PAR,T I. GENERAL PHYSIOLOGY. 1. CHEMISTRY OF THE TISSUES.— Chemical elements ; compound radi- cles ; proximate principles. 1. The albuminous principles ; albuminates, albuminoids, albuminous derivatives. 2. The fatty principles and their allies ; the true fats, glycerin, origin^f fat, amyloid substances and sugars, acids related to sugar. 3. The mineral principles ; gases, free acids, salts, metals, water. 4. Pigmentary principles ; melanin, the colouring mat- ters of the blood, of the bile, of the urine, . . . . .2 2. GENERAL HISTOLOGY.— 1. The molecular elements of the tissues; physical and vital laws of molecular coalescence and disintegration. 2. Cell elements ; cell theories. 3. Fibrous elements ; function of non-con- tractile and contractile fibres. 4. Tubular elements, including cartilage ' and bone ; general conclusion as to the molecular theory of organisation, 35 3. PHYSICAL AND VITAL PROPERTIES OF THE TISSUES.-General physical properties ; molecular, mechanical, hydrostatic and bydrody- namic, pneumatic properties ; properties relating to heat, to acoustics, to optics, to magnetism, to electricity ; electrical fishes ; electricity in the animal tissues ; vital properties of the tissues ; difierentiation in growth, contractility, sensibility, mental acts ; relation of the physical to the vital forces, .*......... 105 ON LIFE OR VITALITY, 184 PART II. SPECIAL PHYSIOLOGY. NUTRITION.— Aliment ; mastication ; insalivation ; deglutition ; diges- tion in the stomach ; digestion in the intestines ; digestive fluids ; chylifi- cation and sanguification ; leucocythsemia ; circulation of the blood, respiration; absorption and the secondary digestion; animal heat; excretion by various organs ; from the lungs, from the liver, from the kidney, from the skin, from the intestines ; general results of the excre- tory process ; abnormal nutrition, ...... 187 viu CONTENTS. PAGE 2' INNERVATION.— Structural arrangement of the nervoua system j- gen- eral functions of the nervous system ; laws regulating morbid actions of the nervous system; special functions of the nervous system; of the cerebrum, cerebellum, corpora striata and optic thalami, corpora quadri- gemina,^ pons varolii and medulla oblongata, spinal cord, cerebro-spinal nerves, sympathetic nerves; special senses; smell, taste, touch, sight or vision, hearing, sense of weight or a muscular sense ; voice and speech ; sleep, dreams, somnambulism, monoideism ; abnormal innervation, . 282 3. REPRODUCTION.— 1. Homogenesis. Production and discharge of germs ; . fecundation of germs ; changes in the ovum which follow fecundation ; changes in the uterus which follow f ecimdation ; lactation. 2. Partheno- genesis ; natural selection ; sexual selection. 3. Heterogenesis ; history ; development of infusoria; histological proof; nature of dust; chemical experiments ; abnormal reproduction, ..... 372 ON DEATH.— By syncope, by asphyxia, by coma, .... 441 PART III. PRACTICAL PHYSIOLOGY. 1. PRACTICAL CHEMICAL PHYSIOLOGY.— General qualitative examina- tion of an animal fluid ; analysis of special animal fluids ; of the blood, of chyle^ of lymph, o! saliva, of gastric juice, of bile, of urine ; volumetric analysis ; examination of sugar by the saccharimeter ; clinical examina- tion of the urine ; analysis of the fseces ; analysis of special animal solids ; of muscle, of white fibrous tissue, of yellow elastic tissue, of teeth, of car- tilage and bone, of the nervous system, of the liver, . . . 444 2. PRACTICAL HISTOLOGICAL PHYSIOLOGY. -History of the micro- scope ; optical principles ; construction of the microscope ; mechanical and "optical parts; test objects; mensuration and demonstration; how to observe with the microscope ; mode of conducting the course ; preparation of the tissues ; staining the tissues ; injection of the tissues ; preservation of the tissues, ....... 496 3. PRACTICAL EXPERIMENTAL PHYSIOLOGY—Experiments on the muscular system ; apparatus ; experiments on contractility, on the evo- lution of plectricity by muscles, on the effects of muscular irritation ; experiments on nerve, on Pfluger*s law of contraction, to determine the rapidity of the nerve current ; experiments on the circulation, on the pulse, to measure the rapidity of th&- circulation ; to measure blodd pres- sure ; experiments on respiration; experiments on sight or vision, mea- surements of the curvature of the cornea and lens by the ophthalmometer, the ophthalmoscope ; experiments on hearing, of combination, summation, and difference tones, Helmholtz and Apunn's apparatus ; experiments on voice, Muller and Apunn's apparatus, the laryngoscope, . . . 525 INDEX, ... 581 ERRATA, ... .... 605 INTEODUCTION. Physiology is that science which treats of the phenomena ob- served in living beings.' Of these, such as occur in plants are now taught by the Professor of Botany, and such as distinguish the lower animals are comprehended in the lectures of the Professor of Zoology. By Physiology, therefore, at present, is generally understood a knowledge of the functions of the human body — in other words, human physiology ; whatever facts, how- ever, throw light upon this last branch of the subject, observed in any of the kingdoms of nature, are made available for the pui-pose. The student, after obtaining a certain knowledge of Anatomy — ^which teaches us the structure and relations of the parts of the body, as determined by dissection — should, in the first instance, study the chemical, histological, and physico- vital phenomena presented by the tissues of which the organism is composed. This has taught us that all function is dependent upon the alterations and actions upon one another of the ultimate molecules — chemical and histological — of which these tissues are made up, and that the sum of the forces they evolve, constitutes vitality. He should next pay attention to the special physiology of organs, which, according to the functions they subserve, are arranged into the three groups of Nutrition, Innervation, and Reproduction. Lastly, he should exercise himself in the methods and in the use of the instruments which have become so necessary for clearly comprehending and making additions to the truths of physiological science. This branch of the subject I have for many years taught in the Laboratory of this University under the name of Practical Physiology. PART I. GENERAL PHYSIOLOGY. General Physiology comprehends, 1st, the Chemistry; 2d, the Histology; and, 3d, the Physical and Vital properties of the Tissues, — ^with the consideration of what is understood by life or vitality. CHEMISTRY OF THE TISSUES. At one time it was supposed that the peculiar character of the chemical compounds formed in living bodies was due to the action of a mysterious force, termed vital .force, but later re- searches have shewn that many of those compounds may be produced in the laboratory, either by the direct combination of their elements, or by chemical changes produced in inorganic compounds. For example, cyanogen gas (CaN) is a compound of carbon and nitrogen, and may be formed by the direct union of its elements. This, combined with ammcfluum, forms cyanate of ammonium, and by a molecujar transformation of the elements of the latter, urea, a well known organic substance excreted by the kidneys, is formed. Thus : — CNNH4O = COH4NJ Ammon. Cyanate, Urea. In like manner, a large number of organic compounds, known as alcohols, aldehydes, acids, ethers, amines, &c., may be prepared from hydrocarbons, such as marsh gas and ethylene. But although many of the proximate principles of animals may be prepared artificially by ordinary chemical actions without the CHEMICAL ELEMENTS. 3 agency of a vital force, we cannot for a moment suppose that chemistry alone will ever succeed in producing even the simplest plant or animal. Chemical Elements. As there have lately been changes in the chemical doctrines concerning atojna, and their symbols, relative weights, and powers, it is necessary before we enter upon a detailed examina- tion of the chemistry of the body, to e'xplain certain terms often employed. 1. By an "element" is meant matter which by no known chemical means can be resolved into two or more heterogeneous substances. For example, it is at present impossible to split oxygen or hydrogen into any other substances — hence they are called elements. 2. iisi " atom " is the smallest amount of a chemical element which can exist in a compound. An atom is never found in a free state. An atom of hydrogen is represented by the symbol H. 3. A chemical " molecule " is a combination of two or more atoms, and the atoms may be atoms of the same or of different substances. A molecule can exist by itself. A simple molecule, made up of two atoms of the same element, is seen in the case of a molecule of hydrogen = HH. A molecule of hydrochloric acid is made up of a combination of an atom of hydrogen with an atom of chlorine = HCl. The limits up to which the number of atoms in a molecule may increase are at present unknown. According to Dr Thiidicum,* a molecule of hsematocrystallin, the principal in- gredient of the blood corpuscles, is represented by the formula CmHseoNistFe SsOiTv, representing 1895 atoms. It is remarkable that by the law of condensation, if these 1895 atoms could be brought into the gaseous state, they would occupy two volumes, the same space as would be filled by a molecule of watery vapour containing three atoms. The elementary chepiical substances at present known in nature are sixty-five in number. Of these thirteen are non- metaUic, and fifty-two are metaUic. Only twenty out of this number enter into the composition of organized beings, namely, Ncn-metallie Elements — Oxygen, hydrogen, carbon, nitrogen, * Tenth Report of Medical Officer of Privy Council, 1867. Appendix, No. 7, Dr Thudicmn's Beport. 4 CHEMICAL ELEMENTS. phosphorus, sulphur, chlorine, fluorine, '. iodine, bromine, and silicon ; Metcdlio Elements — ^Potassium, sodium, calcium, mag- nesium, aluminium, iron, manganese, copper, and lead. Of these twenty elements, the most essential are oxygen, hydrogen, carbon, and nitrogen, which may be regarded as the basis of all organic matter. Oxygen, the most abundant of aJl the elements, is an essential, constituent of all living organisms, independently of its existence in the water of the tissues. Myd/rogem also exists in the water of the tissues, of which it' forms one-ninth by weight, and it is found in almost all organic matters. Ga/rhon is the characteristic element of organic bodies ; so much so, that when any substance exposed to heat on a piece of platinum foil becomes blackened or charred, from the separation of carbon, it is known to be of organic origin. Carbon is associated with oxygen and hydrogen to form many of the simpler organic compounds. Nitrogen. In more highly organised substances such as albu- • min, fibrin, and casein, nitrogen is superadded. Free nitrogen is said to be found in the air bladders of fish, and in other cavities of the animal body. • Phosphorus is found in the urine (where it was first discovered), in blood, and in the proximate principles, albumin and fibrin, which enter so largely iuto the composition of all the soft tissues. It also exists largely itt nervous tissue, and in bone, where, in combination with lime, it forms tribasic phosphate of calcium, the chief mineral constituent of that important structure. Stdphwr is necessary to the constitution of albumin, fibrin, and casein, and it exists in the taurin of bile, and the cystiu of urine. It also forms sulphate^ in combination with oxygen and various bases. ChloriTie exists chiefly in combination with sodium and potas- sium, forming chlorides of sodium and potassium — ^the former being a most important constituent of aU. animals. Fluorine has been found in very sniaU quantity in the ash of blood, mUk, and bone. Iodine and Bromine have been found in the secretions of per- sons taking cod liver oU, or in the habit of eating marine plants and animals, all of which contain these substances. Silicon,, in form of silicic acid, is seldom absent from the ash COMPOUND RADICLES. 5 of organic matters, though it exists in very smail quantity According to Gorup Besanez, it forms a constituent of feathers and of hair. Potasdv/m-salts enter largely into the composition of the body forming essential constituents of many organs and fluids, as foi instance, flesh and milk. They are derived chiefly from th« vegetable kingdom. Sodiwm in combination with chlorine, sulphuric, phosphoric carbonic, and various organic acids, exists in every tissue of the body. CaLcvwm, exists iu the bones of animals, as carbonate and phosphate, and it also combines with organic acids. Magnm/mm in the form of carbonate and phosphate, is found in flesh, blood, milk, urine, &c. Iron is one of the most important elements of the body, as i1 forms about seven per cent, of haematin, the red colouring mattei of the blood corpuscles. AlMminivm, Mangcmese, Copper, and Lead, are only 09casion- ally found in the tissues, and their presence may be accounted f 01 by some peculiarities in the chemical nature of the food used It has also been suggested that the copper and lead, rarely me1 with, may have been derived from the apparatus made use ol in the chemical research. Compound Eabiclbs. — Numerous hypotheses have been ad- vanced to explain how the twenty elementary substances abovs mentioned combine to form the tissues of a living being. Before the days of Dumas and Liebig, the opinion generallj held was, that the elements oxygen, hydrogen, nitrogen, and carbon, combined to form ternary and quaternary compounds which made up the tissues and fluids of the body. M. Baspail taught that oxygen and hydrogen first united tc form water, which, entering into combination with carbon formed a ternary compound. In the same manner, nitrogei entered into the composition of the tissues, through the agencj of an ammoniacal salt, and the union of this salt with wate] formed nitrogenised organic matter. The next theory was that of Liebig, which has been termec the theory of compound radicles. Among the numerous sub stances derived from the organs of an animal, groups are found the members of which exhibit a close analogy with each pther 6 COMPOUND RADICLES. both in chemical constitution and in the decompositions they undergo. For example, each member of the following series of alcohols, contains an atom of carbon, and two atoms of hydrogen, less than the one immediately above it. Wood spirit, CH4O. Ethylic alcohol, C^HeO. Propylic alcohol, CjHsO. Butylic alcohol, CJSioO. Each of these compounds is evidently analogous to wood spirit, but contains an additional number of multiples of the hydrocarbon CHj, and the group forms what chemists term a homologous series. By various chemical processes, each alcohol yields an ether, an aldehyde, an acid, &c., and these derived compounds form a heterologous series. Liebig explains this similarity existing between members of such a homologous series, by the hypothesis that in each of them there is a certain group of elements, which he terms the radicle of the series — the radicle of the fiboye series being methyl (CHs). Thus wood spirit is the hydrated oxide of methyl (CH5HO). The ether derived from wood spirit, is the oxide of the radicle (CH8)20. A radicle may be simple or compound. The radicles of inorganic chemistry are Usually simple ; those of organic chemistry are complex ; but in either case, the radicle plays the part of a base and discharges a function analogous to that of potassium and its salts. In carrying these general views into detail, M. Bumas made the beautiful, generalisation, that an animal should be regarded, in a chemical point of view, as an apparatus of combustion, which incessantly returns %o the atmosphere carbonaceous' matters in the shape of carbonic acid (CO2), hydrogen as a constituent of water (HjO), and free nitrogen in the form of ammonium oxide (NHjO). In short, from the animal kingdoni as a whole, there is constantly given off carbonic acid, watery vapour, and nitrogen. Vegetables, on the other hand, absorb and fix these substances, retaining the carbon and hydro- gen, and setting free the oxygen. They also abstract nitrogen directly from the air, or indirectly from ammonium oxide, or nitric acid. Vegetables, for the most part, f orin organic matter under the influence of solar light. They pass ready formed, as food into the bodies of animals, which, during their life, or after their death, restore them to the atmosphere from which they PROXIMATE PRINCIPLES. 7 were originally derived. Thus the animal kingdom is an ap- paratus of combustion, the vegetable kingdom an apparatus of reduction ; the one produces the elements which the other con- sumes ; so that, in the language of Dumas, they ajre the " off- spring of the air." They come from the atmosphere, and return to it again. The various mineral matters which enter into the constitution of living beings, exhibit the same dependence which animals have upon vegetables, and these, again, upon inorganic matter, They simply pass through living beings, as it were, to serve certain important purposes in the scheme of life. Let us take lime and sulphur as examples. Eain water, loaded with the carbonic acid of the air, falls upon calcareous hills, and carbonate of hme, in a state of solution, enters rivers, and is by then carried to the ocean, where it is seized upon by millions o: animals, and converted into their external skeletons or shells The water of rivers and springs also is absorbed by plants, ane drank by animals ; and so lime enters into their substance, ane is converted into various salts of that base, such as oxalates tartrates, phosphates, &c. Phosphate of lime is the principa element of the bones, besides entering more or less into thi constitution of the other tissues of the superior animals, whicl are continually excreting, as well as assimilating it. Lastly, 01 their death, t^e lime is dispersed in various ways ; even th bones crumble to pieces ; and so the mineral returns to the soil from whence it came. Sulphur passes from one region t another, in a similar manner, from the' sea, which contain sulphur in large quantities, to the atmosphere, thence to, the soi and thence to plants and animals, from 'Whence agam it return to the bosom of the ocean. > ) 1 , Vi ' These incessant exchanges between the soil or atmosphert plants, and animals, constitute the theory known as the cherip cal balance of organic nature." ' > i ' PROXIMATE PRINCIPlkS. The various elements above enumerated arrange themselve under the influence of chemico- vital laws, to /o^iwhat are terme " Proximate principles." A proximate principle, ktricstly speal ing, is any substance, whether simple or compound, which exisi under its own form in the animal solid or fluid, and which ca 8 ALBUMINOUS PRINCIPLES. be extracted by means whicli do not alter or destroy its chemical properties. For example, tricalcic phosphate is a proximate pria- ciple of bone ; but phosphoric acid is not so, since it does not exist as such in bony tissue, but is produced only after the decomposf-i tion of the tricalcic phosphate ; still less phosphorus, which is obtained only by decomposing the phosphoric acid by the action of charcoal. The chemical proximate principles, which are of such para- moimt importance, in constituting the substance of the body, may be divided into four groups — ^namely, 1st. the albuminous ; 2d. the fatty ; 3d. the mineral ; and, 4th. the pigmentary principles. AU these are more or less associated together in every texture and fluid, but some abound in one, and others in another, giving to each peculiar characters. 1. The AiBUMiNOTJS Priitciples. The albuminous principles are divided into, 1st. Albuminates ; 2d. Albuminoids ; and, 3d. Albuminous derivatives. Albuminates. — Mulder supposes that all the albuminates contain the same radicle Ci8"H27N406, which he terms protein, combined with small quantities of sulphur and phosphorus. 1. Albwmin. — Composition in 100 parts — C53"3,H7'1,!N'15"7, 022-l,Sl'8 (Lieberkuhn). Various chemists have found a very smaJl proportion of phosphorus in albumin. According to Mulder, albumin is a' compound t)f protein and a hypothetical substance termed sulphamide — V ' , 5Ci8HAQ.+Ni,H4S=C„Hi„NjffiSOa,. ^J/ti -, ^ Protein.^ ^ ^^idpharriide. Albumin. Albumin forms the white of eggs, where it exists as albuminate of spdiuins, an(| it occurs in (large quantity in all the animal fluids which icontribute to nutrition. It is also found in most of the animal solids.^ It does not occur in the body in a free state, but is always associate'd, ^th an alkaline base forming an alkaline albuminate^ It exiks {in two forms — soluble and insoluble albumin — ^the former being easily converted into the latter by the a^ejicy of beat^ ^Hn the familiar example of boiUng an egg ; but it is doubtful if albumin is ever present in .the living body in its insoluble state. Nearly all acids precipitate it from its solutionis. ■ Nitric acid ALBUMINOUS PRINCIPLES. 9 does this so readily, that it is used as a test of the presence of soluble albumin. When boiled with hydrochloric acid, ammonium chloride, leucin, tyrosin, and other substances are formed. It is insoluble in alcohol and ether. It is pre- cipitated by corrosive sublimate and potassium ferrocyanide. When distilled with manganese protoxide, and sulphuric acid, it is decomposed into acetic, propionic, butyric, and benzoic aldehydes, with the corresponding acids. Two modifications of albumin, derived from pathological fluids, have been described, — paralbumin and metalbumin, — ^the former being not com- pletely precipitated by heat, and the latter not being thrown down by potassium ferrocyanide. This substance is of the greatest physiological importance. The egg of a bird contains hardly any other nitrogenous com- pound except albumin, the yolb containing, in addition, a yeUow fat, with traces of iron and other organic matters. Yet we see in the process of incubation, during , which no foreign matter except atmospheric air can be introduced, or can take any part in the development of the animal, that feathers, claws, blood corpuscles, cellular tissue, and vessels are produced. 2. F'ibnn. — Composition in 100 parts— C52-7,H6-9,N15-4, 023*5,S1'2 (Mulder). Albumin may be converted into fibrin by oxidation, as may be shewn by passing a stream of oxygen through defibrinated serum, when the albumin in the latter is con- verted into fibrin, and separates in thirty-six hours in small clots. It is completely insoluble in cold water, in alcohol, and in ether. Kbrin is present in the body in a fluid state. It is found in small quantity in the blood (about 2'55 per cent.), lymph, and chyle. A variety of it, contained in sohd muscular flesh, has been termed syntonin. Lehmann supposes it is formed in the organism from albumin, by the latter taking up oxygen. Until lately, fibrin was supposed to have the property of coagulating spontaneously, but recent researches by Dr Schmidt of Dorpat shew that its coagulation is due to^ the action upon it of another substance termed fibrino-plastic substance or globulin, a protein substance nearly related to albumin. The presence of air hastens the action. 3. Casern. — Composition in 100 parts— C53-8,H7-0,N15-1, 022-6,Sl (Moleschott). These numbers agree closely with the analyses of albumin, except that less sulphur is present in casein. It is slightly soluble in water, and it differs from albumin in the lo ALBUMINOUS PRINCIPLES. solution not being coagulable by heat. It is precipitated by all acids, except carbonic acidj and is redissolved in excess. It is also precipitated by all earthy and metallic salts, and by potassium ferrocyanide. Casein constitutes the eWef ingredient in the milk of the mammalia. It has also been found in very small quantity in morbid bUe, in the fluid of ceUulax tissue, in flesh-juice, and in the small intestine of the human foetus. It constitutes the envelope which surrounds the globxdes of oil or butter which float in milk. Eennet, which is an infusion of the mucous membrane of the fourth stomach of young calves, readily ' coagulates casein, the cause of this peculiar action being unknown. 4. Myosin. — This substance constitutes the gelatinous mass obtained by squeezing pulverised flesh from which all blood has been removed. The fluid part of muscle, or muscle-plasma, consists of myosin, or muscle-clot, and muscle-serum. Myosin gives the usual albuminoid reactions. It differs from blood fibrin in coagulating in a gelatinous mass, — not forming molecular fibres, as wiU be described in referring to the fibrous elements of the tissues. When myosin is dissolved in dilute acid, it becomes converted into another nearly allied substance, syntonin. Syn- tonin is insoluble in solution of sodium chloride, but in a ten per cent, solution of this salt, myosin is readily soluble. Syntonin is, 'however, not a special product of muscle, as it may be prepared by acting upon any albuminoid with hydrochloric acid. • 5. OldbnMn or CrystalUn. — Composition in 100 parttf^ C54-5,H6-9,N16-5,O20-9,Sl-2 (Punke). This albuminous sub- stance is found in the crystalliae lens of the eye, and, according to some chemists, in the blood corpuscles. It forms a yellowish transparent mass when extracted from the lens by ether and alcohol. It is precipitated by all acids, including carbonic acid, and is redissolved by passing a stream of oxygen through it. According to Valenciennes and Frtoy, the crystalline lens of fishes contains a substance called phaconin. The AiBUMiNoiDS constitute another group of substances nearly related to the albuminates, and no doubt derived from them. They are such bodies as Gelatin, Chondrin, Elastic stuff, or Elastin, Mucin, Pyin, Pepsin, and Ptalyin. 1. Oelatin. — Composition in 100 parts — C50-9,H7'2,N18'3 O and S23'6 (Gorup Besanez). It is obtained by boiling animal membranes, skin, tendons, &c., or by macerating bone in dilute ALBUMINOUS PRINCIPLES. ii hydrochloric acid. When allowed to cool, it becomes a semi-solid, tremulous jelly, and if allowed to dry, it becomes elastic, vitreous, brittle, and hard. It is not precipitated by any acid except taimic acid. Though nearly allied to the protein compounds, it differs from them, and hence it has been found that animals fed exclusively on this substance die of starvation, as nutritive blood cannot be formed from it. 2. Chondrin. — Composition in 100 parts — C49"5,H7'1,N14'4, O and S28'9 (Gorup Besanez). This substance nearly resembles gelatin. It may be obtained by boiling permanent cartilage, such a* those of the ribs or larynx. It is, when dry, a homy, hard, diaphanous substsmce. Solutions of it give a precipitate with all acids, alum, alumiuium sulphate, plumbic acetate, and ferric sulphate, — thus diflfering in a remarkable manner from gelatin. 3. Elagtin. —Composition in 100 parts— C55-65,H7-41,N17-74, O19'20 (Tilanus). This is found in ordinary yellow elastic tissue, of which it forms the chemical basis. It contains no sulphur. It is quite insoluble in boiling water, thus differing from white fibrous tissue, which yields gelatin on boiling. 4. Mudn. — Composition in 100 parts— C52-4,H7-0,N12-8, 027'8 (Scherer). This is the most important chemical constituent ' of mucus, the secretion of mucous membranes. Dilute acetic acid and mineral acid precipitate it. Heat produces no coagu- lation. 5. Pyira.— Composition in 100 parts— C51-69,H6-64,N15-09, 026'58 (Gorup Besanez). It is a constituent of pus, a patholo- gical product the result of diseased actions of the animal body. It resembles mucin in its general characters, but differs in being precipitated by mercuric chloride. 6. Pspsm.- Composition in 100 parts— C56-7,H5-6,N21-1, 016'5 (Vogel). The active principle of the gastric juice is a ferment which acts powerfully on all proteiu bodies, forming derivatives which have received the name of peptones. It is prepared in great purity by treating an infusion of the glandular layer of the stomach with dilute tribasic phosphoric acid. Lime water is added, and the precipitate of calcic phosphate, along with the pepsin, is collected and treated with dilute hydrochloric acid. Having been again precipitated by lime water, the deposit " is dissolved in dilute acid. To this second solution, a solution of cholestrin is slowly added, and the cholestrin, with the 12 ALBUMINOUS PRINCIPLES. pepsin entangled in it, is treated with ether. The ether dis- solves out the cholestrin, and the remaining liquid is filtered. The filtrate contains the pepsin, with gives no precipitate with mineral acids, tannin, or mercuric chloride. Pepsin is most active in a dilute acid solution at the temperature of the human body. It is found in the urine, and Briicke found it in flesh. 7. Ptycdin. — This albuminous substance is the supposed fer- ment of the sahva. It contains sulphur. According to some physiological chemists, it converts starch, glycogen, &c., into sugar, by causing them to combine with water. 8. Protagon ot: Mydin. — This substance is distantly related to the albuminous substances above described. It is the chief constituent of nervous tissue, and is the parent of cerebrin, cerebric acid, &c. It may be extracted from brain-substance by ether .and alcohol ; but it is easier obtained from yolk of egg by the same reagents. When purified and well washed, it is a white substance, crystallising in acicular bundles. Its com- position according to Liebreich, its discoverer, is CueHanNi POiffi. Eegarding the histological importance of this substance, see Molecular elements of the Tissues. 9. Quinoidine. — Another substance, named animal quinoidine, was discovered by JBenoe Jones and Dupr6, in all animal tissues, especially in the crystalline lens. It resembles quinine in its chemical characters and optical properties. ALBnMiNOUS Derivatives. — The albuminous principles above described, undergo a disintegrating process in the tissues, and the result of this process is the formation of a number of com- pounds, which are excreted frbm the body. They are — • 1. Glycocholic Add. -^ CjeHuNOe. In combination with sodium, this acid exists in large quantity in the bile. When obtained pure from ox bile, it crystallizes in bulky masses of white slender needles. It is not very soluble in hot or cold water, but is easily soluble in alcohol and ether. It turns the plane of polarization to the right. 2. Twwocholic Add. — CaeHjsNSO,. This acid exists as a sodium salt in the bile of most animals, along with glycochoKc acid ; but in the bile of the dog it occurs free from the latter. It occurs as very fine silky needles, which, when exposed to the air, rapidly change into an amorphous transparent mass. It ALBUMINOUS PRINCIPLES. 13 differs from glycocholic by containing sulphur, and by being eagHy soluble in water. 3. TJric Acid. — Q^^^^ This very important acid occurs ia smaU proportion in the urine of man. It is always to be found in the juices of the spleen, liver, lungs, and brain. It exists, in excess in gout, and in various forms of bodily derangement, attended by the formation of urinary calculi. It may be easily extracted from the urine of serpents, or from guano. When anhydrous, it forms small white crystalline scales, but with a little water of crystallization, it forms large crystals. It is very nearly insoluble in water. When heated dry it decomposes into hydrocyanic acid, cyanuric acid, anmionium cyanate, urea, and ammonium carbonate. Under the microscope, it presents various crystalline forms, as found in urine, but they are generally rhombs with the obtuse angles rounded off, and occasionally dumb-bell crystals. TJric acid is a product of the incomplete oxidation of the tissues. Its most remarkable characteristic, is the readiness with which it is acted on by all oxidising agents. In this way, numerous definite compounds are produced, the chief being alloxan, aUoxantin, allantoin, and murexide. The relation existing between these substances, will be apparent on studying their chemical f ormulse. Uric acid, . . . . . Q,^^^^^ Alloxan, AUoxantin, Allantoin, Murexide, CS^HA+SHjO. CsNeHA. When uric acid is subjected to the action of an oxidising agent, in the presence of water, it gives up two of its atoms of hydrogen to the oxidising agent, while the remainder, termed dehydtiric acid, reacts with water, to form mesoxaJic acid and urea. Thus — . CbNiH A+01i,4-4 H,0 = CsHA+a CN2H4O+2 HCl. XTric acid. Chlorine. Water. Mesoxalic acid. Urea. Hydrochloric acid. Those two atoms of urea are, however, formed at two suc- cessive stages of the process, the first of which result in the formation of alloxan, and the second in its decomposition. Thus— CsN^HA+SHsO = CiNjHA + CN^H^O. Dehyduric acid. Water. Alloxan. Crea. CiNjHA +2 H2O = CaHA + CNsHiO. Alloxan. Water. Mesoxalic acid. Urea. 14 ALBUMINOUS PRINCIPLES. Hy removing two atoms of hydrogen from mesoxalic acid or alloxaa, other acids are fonned. The numerous bodies which have been in this manner obtained from uric acid, upwa,rds of forty in number, may, according to Odling,* who has paid much attention to this intricate subject, be classified into, 1. Simple non-nitrogenous acids, such as mesoxaUo acid ; 2. Bodies containing a residue of the acid, along with one residue of urea, or mon-ureides, such as alloxan ; and, 3. Bodies containing a residue of the acid plus twcT residues of urea, or the di-ureides, such as uric acid. " Hydrated uric acid differs in composition from two atoms of urea by the addition of tiiree atoms of carbonic oxide CO, capable of oxida- tion into carbonic anhydride COa, and by that oxidation of generating a certain amount of heat, or its equivalent of motion. 2 HaO + C5N4H4OS + 03= 3 CO2 2 CNjH^Oa. Water. Uric a^id. Oxygen. Carbonic Urea, anhydride. " Hence uric acid must be considered to result from an incomplete oxidation of nitrogenous tissue, whereby, in addition to urea, carbonic oxide is produced, instead of carbonic anhy- / dride." Eeptiles, whose motions are sluggish and temperature slow, excrete carbonic. oxide in the form of uric acid, or urate of ammonia ; while mammals excrete perfectly burned carbonic anhydride. In the urine, uric acid is found in combination with ammonium and sodium. For crystals of uric acid and various tirates, see Plate I., figs. 1, 2, 3, and 4, and description of plate. 4. Urea. COH4N2. — This substance is found in the urine of all mammals, especially in that of flesh eaters. It is also found in smaller quantity in the urine of birds and reptiles, and in the renal secretion of some animals of the lower orders. In a state of health, it exists in very minute quantity in the blood of man and of other animals, and it occurs occasionally in the perspiration, in the amniotic fluid, and even in the tissues. About 30 per cent, of the solid matter of the vitreous humour of the eye consists of urea. Considered chemically, it is isomericwith ammonium cyanate (CNNH4O) and with carbamide (N3(CO)"H4), and it may be formed spontaneously by the transposition of the molecules of the former substance. The ammoniacal odour of * Lectures on Animal Chemistry, delivered at the Royal College of Physicians. - By WUliam Odling, M.B., P.E.S., &c. London. 1866. ALBUMINOUS PRINCIPLES. i5 decomposing urine is due to caxbonate of anunoma, produced by the combiaation of water with urea, thus ; — COH4N2 + 2H2O = (NH^^COj Urea. Water, Ammonium carb. Urea is formed as a product of the decomposition of many complex organic substances such as creatin, uric acid, allantoin, &c. Its presence in the body is due to the trans- formation of the tissues under the influence of the oxygen of the air absorbed in the lungs, and it is the last term in the series of the retrograde metamorphoses. When obtained pure, urea usually crystallizes in long flat prisms without terminal faces, but in certain circumstances it forms quadratic prisms terminated by octahedral faces. It tastes like saltpetre, dissolves in its own weight of cold water, veiy readily in hot water, easily in ajcohol, but is nearly insoluble in. ether. Urea forms three sets of compounds : 1, with acids ; 2, with oxides and salts ; and 3, various substitution derivatives called compound ureas. The most characteristic salt is the nitrate (COH4N2.HNOS) which appears even in dilute solutions of urea, on the addition of a drop of nitric acid, in the form of rhombic or hexagonal plates, the acute angle of which, as measured by the goniometer = 82°. The appearance of this salt affords an excellent test for detecting the presence of urea in any fluid. The most important compound of urea with a salt is with mercuric nitrate, and Liebig's process for the volumetric estimation of urea is based on the precipita- bUity of urea by mercuric nitrate, forming a compound, the com- position of which is represented by the formula COHiNj 2 HgO. 5. Hvppwric Acid. CsHsNOj (PI. I. fig. 5). — This acid exists in very small quantity in the urine of man, but it is found abundant in that of herbivorous animals. According to Dr Bence Jones, the urine of a healthy man contains from 0.03 to 0.04 per cent, of this substance. When benzoic acid is taken internally, hippuric acid speedily appears in the urine. This acid forms colourless transparent prisms, often of considerable size. , 6. Inodnic Acid. CsHgNjOs (?) — It is doubtful whether this acid, first isolated by Liebig, really exists as such in the body, but it is undoubtedly one of the derivatives of the albuminous group. It was found in the mother Kquor of the preparation of creatin from flesh-juice, and appeared as an un- crystallisable substance, very soluble in water, and having a flavour of broth. 1 6 ALBUMINOUS PRINCIPLES. 7. Xanthin or Xcmthic OaAde. CsHjN^O. — This body occurs in a species of urinary calculus, and, according to Scherer, it is a normal constituent of the 'human body. It differs from uric acid only by one atom of oxygen, uric acid having Oj whUe xanthic oxide contains only Oj. It may be prepared arti- ficially from uric acid, from guanin, from muscular flesh, and from urine. It is a white scaly substance,' nearly insoluble in water, and insoluble in alcohol and ether. 8. Mypoxanthin or Sa/rein. C5H4N4O. — This substance is a weak organic base, existing in muscle^juice, and only in small quantity. A substance very similar to it has been found in human urine, but chemists are not agreed whether this substance is really sarcin or guanin. It is obtained from the mother liquor in the preparation of creatin, and is a white crystalline powder. 9. Cystin or Gystio Oxide. CaNH^SO^.— (PL I. fig. 6.)— This organic base is found in a very rare form of urinary calcu- lus occurring in men and dogs, and when separated, is seen to be a yellowish, shining, confusedly crystaUine substance, tasteless, neutral, insoluble in alcohol and water. It is remarkable for containing sulphur. 10. Taurin. CjHyNSOa (PI. I. fig. 7 a).— This remarkable substance was first obtained from oxbile and hence its name : from tawv^, a buU. It results from the transformation of taurocholic acid under the influence of acids and alkalies. C2eH«NSO;+H,0=C2H7NS03-J-C2,H4A Taurocholic acid. Water. Taurin. Cliolic acid. Fresh bile is clarified from mucus by the addition of an acid, and filtered ; boiled with hydrochloric acid ; the decanted liquor evaporated nearly to dryness on the water bath, and the mother liquor extracted with alcohol. The liquid on cooling, yields taurin in the form of six-sided prisms, terminated by four and six-sided pyramids like those of common quartz. It has a cool taste, is soluble in water, but insoluble in alcohol and ether. It is remarkable for containing more than 25 per cent. ' of sulphur. When burned, fumes of sulphurous anhydride are evolved. Tauria is nearly related to isthionate' pf ammonium, one molecule of this substance, minus a molecule of water, yield- ing a molecule of taurin. It is never found in the free state in healthy bUe, or in any other secretion. 11. AUantmn. CANA- — (PI- I- Pig- 8.)— This substance is one of the derivatives of uric acid, and may be artificially pre- ALBUMINOUS PRINCIPLES. 17 pared from it. It exists in the amniotic and allantoic fluids, and when isolated, is found to present the form of shining colourless prisma, very soluble in water, and also in alcohol. 12. Tyromi. C9H11NO3 (PI. I. fig. 9). — This substance occurs ready formed, and always accompanied by leucin, in the liver and blood of the hepatic vein in certain states of liver-diaorder ; and it has also been discovered in the spleen and pancreas. Occa- sionally it is found in the urine, and it may T^sult fi-om the decomposition of any albuminoid substance under the action of adds, alkalies, or putrefactive changes. Artificially, it has been prepared from casein, from horn,, and from cochineal. It crystallises from aqueous soluticais in stellate groups of long slender needles, having a beautiful silky lustre, soluble in watery in alcohol, but not in ether. It forms definite conipounds with acids and alkalies, and there are several derivatives of more interest to the chemist than to the physiologist. 13. Leadn. CsHisNOs (PI. I. fig. 10).— First discovered in old cheese, leucin has since been found, associated with tyrosin, in the liver in certain forms of disease of that organ. It also occurs in the lung-tissue, in the thyroid and thymus glands, and especially in the pancreas. It may be obtained by the action of sulphuric acid upon gelatin, muscular flesh, legumin, wool, white of egg, horn, &o. ; and when purified, it presents the appearance of soft nacreous scales, somewhat resembling cholestrin-. When found in urine, it forms yellow-coloured balls. (See PL I. fig. 10.) It is sparingly soluble in cold, but readily in hot water ; sparingly in alcohol, and insoluble in ether. It fQrms definite compounds with acids and bases. 14. Olyeodn or Qlycocol. CjHsKOj. — This substance is some- times called sugar of gelatin, on account of its sweetish taste, and its being produced by the action of caustic alkalies on gelatin or meat. It exists in glycochohc acid, one of the bile acids, which, when acted on by an alkali, is resolved into glycocin and choUc acid. CaiH«N08 + HjO = CANOs, -f C^A Glycocholic acid. Water. Glycocin. Cholic acid. It may also be obtained from hippuric acid. It crystallises readily in flattened prisms or aggregated plates. It is sparingly soluble in water, slightly soluble in hydrated alcohol, insoluble in ether. It differs from taurin in being sweet instead of bitter, and in not containing any sulphur. B 1 8 FATTY PRINCIPLES. 15. Crmtin. C4H9NA (PI- I- % 11).— This important sub- stance is nearly allied to creatinin, differing from it only by the elements of water. It has not yet been settled whether or not creatin, as such, exists in the body, or whether it results from the decomposition of creatinin ia the process of preparation. These two substances may be easily converted one into the other, the action of acids changing creatia into creatinin, while the action of alkalies, creatinin into creatin. Liebig and Dessaignes are both of opinion that the creatin of muscular flesh is produced by the decomposition of creatinin. It has been found in the urine, in the blood, and, by Stadeler, in the brains of pigeons and dogs. It may be prepared by making an aqueous extract of beef, evaporating in vacuo, exhausting the residue with alcohol, and the alcohol evaporated tiU the creatin crystallises, out. Anhydrous creatin is an opaqufe white mass, inodorous, some- what bitter, neutral. The hydrate of creatin is in the form of dear prisms. It is soluble in water and alcohol, but not in ether. According to Strecker, creatin may be regarded chemically as a compound of cyanamide (i. e., urea min/M water) and sarcosin. It is a very weak base. 16. Creatinin. C^HyNsO (PL I. fig. 12). — This substance exists in the urine to the amount of 0'5 per cent., in muscular flesh, and , in blood. It may be extracted from any of these substances, and also by the action of strong mineral acids on creatin. It occurs in the form of colourless prisms. It tinges reddened litmus paper blue, and is soluble in water and in alcohol. 2. The Fatty Principles and their Allies. The fatty principles are divided into, 1. True fats ; 2. Amy- loid substances and sugars ; and, 3. Acids related to sugar. 1. True Pats. — The term fat was originally applied to all substances containing carbon, hydrogen, and a small amount of oxygen, which form oily liquids or greasy soKds, leave a permanent stain on paper, burn with a bright flame with little or no soot, are insoluble iu water, but soluble in alcohol and ether. The re- searches of Chevreul,* however, shewed that fatty substances may be subdivided into (1) non-saponifiable fats; (2) saponifiable fats ; and' (3) fatty acids or soap acids. He shewed that certain * Chevreul, " Becherches sur les corps gras d'origine animale." Paris, 1823. PA TTY PRINCIPLES. 19 fats (the non-saponifiable) undergo no change when boiled with alkalies, while others (the saponifiable) formed soaps when treated with aqueous alkalies or with certain heavy metallic oxides. The formation of a soap when a saponifiable fat is treated with an alkali or metallic oxide is called saponification and consists of the resolution of the fat into two products, viz., First, a fatty acid which combines with the alkali and forms the soap ; and, secondly, almost invariably, the substance called glycerin, a sweetish, clear, transparent fluid. These researches have since been confirmed and extended by those of Berthelot.* A fat is a body of the type of three atoms of water condensed to one, thus — in which three of the atoms of hydrogen are replaced by the triatomic radicle glyceryl, ajid three others by three atoms of any fatty acid radicle. Tristeariuj for example, a fat abounding, in beef and mutton suet, has this formula — ( (CJbHssO) ) 3 monatomic atoms of stearyl . < (CisHssO) f (-, ((C„Hs.O)("=-, 1 triatomic atom of glyceryl . (C, H5) ; 1. The rimb-SaponifioMe Fats are cholestrin and seroHn. These substances remain perfectly unaltered after prolonged boU- ing with solution of caustic potash (KHO). (a) Cholestrin. CjeH^O (PI. I. fig. 13). — This fatty substance sometimes constitutes nearly the entire bulk of human gall stones. It has been found in the bile, in the blood, in the brain, in the yoke of egg, and in certain morbid products of the human body. It is readily prepared by crystallising pulverised biliary calculi from boiling alcohol It is white, inodorous, tasteless, insoluble in water, readily soluble in hot alcohol, from which it is deposited in beautiful soft nacreous laminae. It forms compound ethers when heated with acetic, butyric or stearic acids, shewing that it partakes of the nature of an alcohol. (6) Serolin. — Boudet gave this name to a fat which he ob- tained by the action of ether upon dried blood serum. It is, according to this chemist, amorphous, but Verdeil and Marcet state that it crystallises in nacreous laminae. Some chemists * Berthelot, " Chemie oi:ganique fondle sur la synth^e." 20 FATTY PRINCIPLES. consider this substance to be merely a mixture of several fats of different melting points. 2. The SaponificMe Fats are very numerous, but the most important are stearin, margarin, and olein. When boiled with an alkali they are decomposed into an acid which, uniting with the alkali, forms a soap, glycerin being set free and rising to the surface. Considered chemically, they are the compound ethers of the triatomic alcohol glycerin, hence they have received the name of glycerides. a. Stetwin is ,a white crystalUsable fat (Plate I. flg. 14), con- stituting the chief part of fat, soluble in about seven times its I weight of boiling alcohol, and much more freely in hot ether. It exists in three modifications, differing from each other in the fusing point. These are termed monostearin, distearin, and tristearin. They are ethers formed from glycerin, by the re- placement of one, two, or the whole of the atoms of the typical hydrogen of glycerin, by the monatomic radicle stearyl (CigHgjO.) Monostearin. Disteajln. Tristearin. (C3H5) )^ ,(C,K,) ) (C3H,) Cisl^sOjOs 2(Ci8:^50)^03 3(Ci8H350) ^03 Among the numerous decompositions of stearin, the most in- teresting, from a physiological point of view, is that discovered by Bernard, namely, that stearin, mixed with pancreatic juice, yields an emulsion in which all the stearin is resolved into stearic acid and glycerin. b. Margarin. CgiHio^Og (Plate I. fig. 15).— This substance constitutes one of the solid ingredients of human fat. "When extracted by boiling alcohol, it cr3fBtallises in pearly scales or clusters formed of needles, which are fusible at about 47° C. Various chemists have isolated from fat a substance resembling this, and it is now generally believed that margarin is not a simple fat, but a mixture of palmitic and stearic acids. No ethers corresponding to the stearic ethers, already mentioned have yet been obtained. c. OZem.— Pure olein is colourless, and is a fiuid even at freez- ing point. When exposed to the air, it is resenoid in appearance. Chevreul prepared it by boiling human fat in a flask, filtering after leaving the solution for twenty-four hours, concentrating adding' water, which separates the olein, exposing the product to •cold, and separating the liquid from the solid portion by pressure. Eesembling stearin, it occurs in three modifications, which are FATTY PRINCIPLES. ethers of glycerin, in which one or more of the tj^ical atoms of hydrogen are replaced by the radicle oleyl Ifi^^^^O) as follows: — Monolein. ^ Diolein. Trioleiu. (C3H5 ) (C3H6) ) (C3H,) ' (CisH330)j03 2(Ci8H330) JO3 3(Ci8H330)| o.. 3. The Fatty Acids. — These bodies are obtained chiefly by the saponification of saponifiable fats. They combine with bases to form salts, and may be separated therefrom in their original state by stronger acids. Stearic and palmitic acids may be taken as the type of one series of the fatty acids in which the general formula is G^^^ ; oleic acid is the type of a second series, the general formula of which is CnH2n:_202. A third series, having the general formula, G^2a-^0^, may be obtained by the oxidation of the two preceding groups — oxalic acid being an example. The following ia a list of these fatty acids, arranged in the three groups just indicated: — Stearic AM Grow. Oleic Acid Cfroiip. Oxalic Acid Growp. CnH^A C„H2„-A CA.-^0, Formic . C Hj Oj Oxalic . Cg Hg O4 Acetic . . Ca H4 O2 1 Malonic O3 H^ O4 Propionic Cs.Hj Oj Acrylic . C3 H^ O2 Succinic C4 Hg O4 Butyric . C4 Hj Oj Lipic . CjH^Oi Valeric . C5 HioOj Angelic . C5 Hg O2 Adipic Cg H10O4 Caproic . Cj HijOj ' ' Pimelic C, H12O4 OEnanthylic C, H14O2 Suberic Cg H14O4 Caprylic . Cg HijOa Anchoic Og Hig04 Pelargonic C9 HigOj Sebaic . CioHigOj Eutic . . CioHjoOa Laurie. . Cx2H2402 Myristic . Ci4H,80, Pahnitic . CieHgaOa PhysetoleicCieHjjOj Stearic . CigHjjOg Oleic . CigHgjOa Aiachidic. C2oH4„02 Cerotic . C27H54O2 Melissic . CjoHeoOa a. The Stearic Series of Fatty Adda. Formic acid — CHjOj-^has been found in the blood, in the 22 FATTY PRINCIPLES. urine, in the fluid of the spleen, in muscle-juice, and in the pej spiration. 2. Acetic acrid — C2H4O2 — probably exists in several of the an: mal secretions, but it usually results from the decomposition an oxidation of organic bodies. 3. Butyric acid — C^HgOj— is found, in perspiration, in muscle juice, and, in combination with glycerin, in butter. Whe: butter becomes rancid, it has a peculiar odour, produced by fre butyric acid. It is a pure, colourless, transparent liquid. 4. Valeric ouyid — Qfiyf)2 — is a frequent product of the oxida tion of fats, and of the putrefaction of albuminous substances. 5. Caproic (CjHijOj), Gaprylic (CgHigOg), and Rutic (C10H20OJ adds exist in butter in combination with glycerin. 6. Palmitic ^add — CijHjgOj — ^is universally distributed in th fats of the animal kingdom, and has been obtained by Chevrei] by the saponification of human fat. 7. Stearic acid — Ci8H3g02 — is the most important of the fatt; acids of the group to which it gives its name. It was discoverei by Chevreul as a constituent of the solid fats, especially in bee and mutton suet, but it is also to be found in butter, in humai fat, in the fat of the goose, serpents, &c. It may be prepared b; the saponification with soda-ley of beef or mutton suet, decom posing the soap with water and dilute sulphuric acid, and dis solving the acid in hot alcohol. When allowed to crystallis from such a solution, it falls as nacreous laminae or needles, i tasteless, inodorous, and is distinctly acid. It forms stearate with bases, substitution compounds with chlorine and bromine and a series of ethers. 8. Propionic, (Enanthylic, Pda/rgonic, Lawric, Myristic, Ara chidic, Cerotic, and Melissic adds have never been found in th human body. 6. The Oleic Series of Fatty Adds. Oleic add — C18H34O2 — is the most important member of thi series. It is difficult to isolate it owing to its tendency to com bine with oxygen. It is obtained by saponifying the non-dryinj oils, such as almond oil, and solid fats. It crystaUises from ai alcoholic solution in dazzling white needles. c. The Oxalic Add Series. Oxalic acid forms the lowest, and sebaic acid the highest, tern of this group. FATTY PRINCIPLES, 23 1. Oxalic add — CjHjO^ — ^in combination with calcium as cal- cium oxalate (CaCjO^), is often found in the urine, in urinary deposits, and calculi, in the allantoic fluid, and in the mucus of the gaU bladder. It occurs in the form of square-based, octa- hedral crystals, and occasionally in the form of dumb-bells. (Plate I. fig. 17.) Eecent researches have shewn that oxalic acid is nearly related, in chemical constitution, to many of the derivatives of uric acid already noticed.. Many of these bodies may be regarded as amides (or ammonia substitution compounds) of oxalic acid — ^being derived from two or more molecules of oxalic acid by addition of ammonia and abstraction of water. As these processes may indicate what takes place in the living body, a few examples are here given. 2C2HA + 2NH3 — 4H2O = Cfi^-Nfii Oxalic acid. Ammonia. Water. Alloxan. On introducing a molecule of another acid, we have decom- positions like the following: — C^HA + CO2 + 2NH3 — 3H2O = C3H2N2O3 Oxalic acid. Carbonic. Ammonia. Water. Farabanic acid. Anhydride. 2C2H2O4 -1- CHA -I- 4NH3 — VH2O = C5H4N4O3 Oxalic acid. Formic acid. Ammonia. Water. Uric acid. C3H2O4 -1- CH A + CO2 + 4NH3 — 5H2O = C^HeNA Oxalic acid. Formic acid. Carbonic. Ammonia. Water. Allantoin. Anhydride. 2. Adipic acid has been prepared by the action of nitric acid ' upon suet. None of the other acids of this series have been found in the human body. ' The fatty acids are physiologically important, 1st, On account of their adhesive afRnities ; 2d, by developing heat in conse- quence of their property of oxidising at a low temperature, forming caxbonic acid and water, which, if too abimdant, are readily removed from the system ; and, 3d, by their power of conducting heat. Although we daily consume a large amount of these acids, yet they are not excreted as such, nor do they form fats. Gltceein. CgHgOj. — ^This is the other substajice which is produced in the process of saponification. It does not exist ready formed in fats, but is produced from them, together with a fatty 'acid, by addition of the elements of water. Glycerin is really a triatomic alcohol, and bears the same relation to the fats, stearin and olein, &c.j as alcohol bears to the compound 24 FATTY PRINCIPLES. ethers, one, two, or three of the atoms of hydrogen being re- placeable by acid radicles, producing fatty or oUy compounds. It is an uncrystaUisable,i syrupy liquid, — colourless, inodorous, sweet, neutral. It dissolves in water, in alcohol, and in chloro- form, but not in ether. Obigibt of tat. — The origin of fat in animal bodies has given rise to considerable discussion. 1st, It may enter the body ready formed in the food, whether animal or vegetable ; 2d,' Animals seem to have the power of transforming various substances into fat. Geese fed on grain become fat, bees form wax, 'a species, of fat, from flowers. Thus, says Liebig, the herbs and roots con- sumed by the cow contain no butter ; in the hay^and fodder of oxen, no beef -suet exists ; and no hog's lard can be found in the potatoes given to swine. The masses of fat found in the bodies of these animals are formed in their organism, and this, accord- ing to Liebig, takes place by non-nitrogenous substances yielding up their oxygen. Dumas, however, states that the Indian com or maize on which a goose is fed contains 9 per cent, of fat, and on calculating the quarttity consumed, he found more fat in it than was sufficient to explain the increased weight of the goose. These conclusions were confirmed by the careful and extensive observations of Boussingault. Liebig, however, to support his position, made several very ingenious experiments upon swine. He says that three pigs, to be fattened in thirteen weeks, require 1000 lbs. of pease, and 6825 lbs. of boiled potatoes. These contain together 26 lbs. of fat, — 21 lb. in the pease, aiid 5 lb. in the potatoes. One fattened pig gives on an average 50 to 55 lbs. of fat ; that is, the three together, 150 to 165 lbs. Each animal, before being fattened, contains, on an average, 18 lbs. of fat ; that is, 54 lbs. for the three. If to these 54 lbs. we add 26 lbs. from the food, we get 80 lbs ; and if we substract these from 150 lbs. to 165 lbs., there is a remainder of 70 to 85 lbs. of fat produced from the starch, &c., contained in the food. These experiments have been confirmed by the more recent researches of Messrs Lawes and Gilbert,* who found that, in fattening pigs, for every 100 parts of fat in the food, the animals stored up from 400 to 450 parts of fat in their bodies. The origin of fat, therefore, in the living body is threefold, — 1st, It is derived ready formed from plants ; 2d, It is formed in the absence of oxygen, or where * Lawes and Gilbert. Pfti!o»()ji7i. Tram. 1869, p. 543. FA TTY PRINCIPLES. 25 oxygen js deficient, by the deoxidation of starch, gum, and sugar, which thus supplies the oxygen wanted; and, 3d, By decomposition of the albuminous compounds, the actual character of which is not yet clearly ascertaiaedi 2. Amyloid Substances and Sugars. — The non-nitrogenous substances which, by yielding up oxygen, become transformed into fatty compounds, or are nearly related in chemical com-, position to fatty compounds, are as follows : — Glycogen, stanch, and the different varieties of sugar. 1. Glycogen. C^^f)^. — Animal starch, animal dextrin, hepatiu. This substance, isomeric with starch, occurs in the liver and in the placenta, and is believed to enter largely into the composition of the tissues of the embryo, it occurs in three forms, of which one, of the formula CgHioOj, is powdery, two others, C^HijOj and CjHuOy, are gummy. It is easily prepared by making a decoction of fresh liver, filtering, and precipitating the filtrate with alcohol of 38 to 40 per cent. When dried, it is a white, mealy powder, neutral, inodorous, and tastes like starch. It pdlarizes to the right four times more intensely than dextrose sugar. Iodine colours it violet or bright brown-red, seldom pure blue. All re-agents which transform starch into sugar similarly affect glycogen, and the sugar so produced is identical with grape sugar. The ferments of the saliva, liver, and pancreas readily effect this transformation. The important physiological relations of this substance, as discovered by the labours of Bernard, Pavy, M'Donnell, Harley, &c., will be fuUy considered when treating of the functions of the liver. 2. Starch. CgHmOj. — True starch is now known to exist as a constituent of the human body. (Busk, Carter.) Many of the granvd.es, however, termed corpora wm/ylacem, found in the brain, spinal cord, liver, spleen, kidneys, and mucous membranes, though resembling starch corpuscles in form, do not give a blue reaction with iodine, even with the addition of a little sulphuric acid, and differ from it in chemical composition. To such bodies I have for a long time given the name of wmyloid. Starch is of great physiological importance, inasmuch as it constitutes a large proportion of human food. Infusions of almost any of the animal tissues, and saliva, and pancreatic juice, readily convert it into sugar. 3. Sugwrs. — Under this name are included a number of 26 FA Try PRINCIPLES. organic compounds, whicli are soluble in water, crystallisable, have a sweet taste, neutral reaction, and in a state of solution rotate the plane of vibration of a ray of polarised light. Those of interest to the physiologist are,' a. Saccharose, or cane sugar ; 6. Lactose, or milk sugar; c. Glucose, or grape sugar ; and, d. Inosite, or muscle sugar. a. Saccha/rose, or Game Suga/r. CiaHjjOu. — This substance is not found in the animal body, but it is widely diflfnsed in the vegetable kingdom, and forms an important element in the food of man. It crystallises in large monoclinic prisms, is soluble in water, insoluble in alcohol and ether, and the aqueous solution turns the ray of polarised light to the right. 6. Lactose, or Milk Suga/r. CijHgjOji. — This sugar is found only in the milk of the mammalia. It may be obtained from mUk by precipitating the casein by acid or rennet, filtering, and evaporating the whey to the crystallising point. It occurs as hemihedric trimetric crystals, and the aqueous solution turns the plane of polarised light to the right. It differs from cane sugar in crystaUine form. c. Qiuoose, or Cfrape Suga/r. Diabetic suga/r, sugar of mine, &c., CgHi208+H20- — This substance exists in the hver, in the amniotic and allantoic fluids, in the blood, in the chyle, and in eggs. In the disease called diabetes this sugar is found in the urine often to the amount of 8 or 10 per cent. ; and according to Bence Jones it exists in minute quantity even in healthy urine. Compounds of glucose are likewise found in the animal body* When gelatin, hyaline cartilage, and rib-cartUage are boiled with hydrochloric acid, large quantities of glucose are obtained. It may be obtained by evaporating the urine of diabetic patients, and may be purified by re-crystaUisation from a solution in boiling alcohol. From an aqueous solution it is deposited in white, opaque, gramilar, hemispherical masses, consisting of the hydrate, CgHijOj+HjO. ; but from nearly absolute alcohol it is 6btained as anhydrous, microscopic, sharply defined needles. It is less soluble in water than cane sugar, and it rotates the plane of polarised light 53'2° to the right. It gives a dark brown colour with liquor potassse (Moore's test), and has the power of imme- diately reducing cuprous oxide from an alkaline solution of cupric sulphate (Trommer's test). Its quantitative estimation is made by the amount of cuprous oxide thrown down from a known measure of potassio-tartrate of copper CFehling's test). The MINERAL PRINCIPLES. 27 potasaio-tartrate of copper, made alkaline by the addition of a little liqu,or potaasse, is heated to boiling in a capsule, and the liquid containing sugar is dropped in until the copper solution acquires a pale straw colour by the separation of red cuprous oxide. d. Inosite, or Muscle Sugar. CjHigOj (PI. I. fig. 16). — ^This substance, isomeric with glucose, exists in the muscular suV stance of the heart, in the lungs, kidney, liver, and spleen. It is best prepared from the muscle of the heart. It crystallises in tabidar plates, or oblique prisms, or right rhombic prisms, con- taining two atoms of water of crystallisation. Inosite has a sweet taste, and no rotatory power, differing in the latter respect from the other sugars. 3. Acids related to Sugar. — Nearly allied to the starch and sugar group of compoiinds just described are the two substances known as lactic and sarcolactic acids, the former eidsting in sour milk, the latter in muscle-juice. , 1. Lactic acid. C^S^O^, — This acid is the result of a peculiar fermentation, the lactic acid fermentation, of various kinds of sugar, preceding the butyric acid fermentation. The change of mUk sugar into lactic acid is shewn by the following equation : — Ci2H220ii 4- HgO = 4C3HJO3 Milk sugrar. Water. Lactic acid. 2. 8a/rcolactic add. — When this acid was discovered by BerzeUus in the juice of muscular flesh, he imagined it to be identical with the lactic acid of sour mUk, but Liebig shewed 19iat though the acids are hardly to be distinguished, their cal- cium and zinc salts exhibit marked distinctions. This acid gives the acid reaction exhibited by muscle after it has been fatigued by contractions induced in any way. 3. The. Mineral Principles. The mineral or inorganic principles found in the human body may be classified as follows : — 1. Gases. — Oxygen, (O) and nitrogen, (N) exist in a free state in the blood and in the urine. Hydrogen, (H) is never found in a free state, but exists in water, and in light carburetted hydrogen (CH4). Light carburetted hydrogen (CH4) has been found along with other gases in the flatus from the intestinal canal. 28 MINERAL PRINCIPLES. 2. Free Acids. — Carbonic add (COj), or as it is now called, carbonic anhydride, exists in both venous and arterial blood, especially in the latter. Sidphwric acid (H2SO4) does not exist free in the body, but forms sulphates, which may be either neutral or acid, by com- bining with various bases. Silicic add (SiOj) has been found in several tissues. MyefroeMoricadd (HCl) occursinafree state in the gastric juice. 3. Salts. — 1. Oarbcmates.^Sodium carbonate (Na,2CO3-|-10H2O) and potassiimi ca/rbonate (K2CO3) exist ia urine, and probably in the blood and tissues. Ammonivm, ca/rbonate (NH4HCO3) is said to be found in expired air, but as a normal product, its presence is doubtful. Caldvm, ca/rbonate (CaCOa) exists in the bones and teeth, and it also occurs as a urinary sediment. In the uripe of man it is very rare^ but is common in that of the horse, where it forms peculiar globular bodies, identical with the artificial calculi made by Mr Bainey, which will be described ia treating of the molecular elements of the tissues. Magnedwn ca/rbonate (MgCOs) also exists in bones, teeth, and urine. 2. Chlorides. — The chlorides of sodium (NaCl) anApotasdum (KCl) exist in large quantity in all the solids and fluids of the body. Sodium chloride is the more abundant of the two. Potas- sium chloride is found chiefly in muscle- juice. Ammwmiwm, chloride (NH4CI) is found in the saliva, in tears, and in the urine. 3. Oxalates. — The oxalate of caldwm (CaC204) is found in the urine in certain states of the system. ■ It forms octahedral crystals and dumb-beUs (PI. I. fig. 17). 4. Fluorides. — Fluoride of Caldum (Ca!Fl) exists in small quantity in bones, in teeth, and in the blood. It is found chiefly in enamel, which owes its great hardness to this salt. 5. Phosphates. — The phosphates of sodium, are found in all the solids and fluids of the body. They are three in number, the basicCNasPOi+lSHjO), the neutral (Na2HPOi+12H20),and the acid (NaH2P044-H20)- They exist largely ia the blood,' and recent investigations shew that in the process of respiration they carry the carbonic acid, in a loose state of combination, from the tissues to the lungs, there to be eliminated. In like manner, the basic phosphate of potasdwm (^^0^-\-l^'Kfii), the neutral (K2H:P04+12H20), and the' acid (KHjPO^-t-HaO) are found in every part of the body. The neutral, or ixUhami phosphate of MINERAL PRINCIPLES. 2< calaium, (CaaSPOJ forms the chief part of the earthy matte of bone. It exists in considerable quantity in teeth, and i found in all the solids and fluids of the body. The phosplMte q wagnemMm (HMgP04+7H20), exists in the blood, in th urine, and generally, though to a comparatively small amouni in the tissues. The ammonia-magnesic phosphate (MgNH^PO +6H2O) is frequently met with as a constituent of urinar calculi, and is always formed during the alkaline fermentation urine. It occurs as large, transparent, rhombic prisms, but it i sometimes peniform or feathery in its appearance (PI. I. fig. 18] 6. Sulphates. — ^The sulphates of soMum, (NajSO^+lOHjO), 'potasnwm, (KjSOj) , and of calcvwm, {GsSO^ , are found everywhere specially in the blood and urine. Svlphate of calavmn exist largely in bone. 7. 8vlphooyanides. — The sidphoeyamide of potassiwm (KCNS is found only in the saliva, and in very small quantity. 4. MbtaIjS. — The presence of iron, manganese, copper, am lead have been already noticed (p. 5). The state of combinatio: in which these metals exist in the body is quite unknown. C these, iron is the most important. The mineral ingredients above described enter the body c man in his food and drink. They all exist, more or less, in th ordinary articles of food ; and even pure water, the natural drin of man, contains many of them in a state of solution. Fc instance, if a man were to consume two lbs. of potatoes and tw lbs. of bread daily, no less than half an ounce of solid tribasi phosphate of calcium would enter his system in twenty-fou hours. The salts are chiefly excreted by the kidneys and alvin evacuations, but every secretion contains more or less of then so that it is possible to judge of the amount of mineral mattt which enters the frame from the quantity which leaves it. The are given oflF by the emunctories in proportion to the amour introduced, so that a healthy state of the economy is preservec Some mineral substances pass through the body and appear i the urine unchanged, such as the alkaline carbonates, sulphate nitrates, phosphates, borates, chlorates, silicates, &c. ; whU others are changed, such as salts of ammonia, which may be coi verted into nitrates. The neutral salts of the organic acids ai converted into carbonates. 30 PIGMENT A R V PRINCIPLES. Irregularities of food must modify the amount of mineral matter taken into the system. These mineral matters are usually soluble, but only to a certain esstent. If then they be in excess, so that the natural fluid containing them is more than saturated, they are partly precipitated and give rise to concretions. A diminution of the fluid of the secretion would of course produce the same result. Occasionally, insoluble salts are formed, which are deposited from one or other of the excretions, an example of which is seen in the octahedral crystals of oxalate of lime found in the urine. 5. Water (HjO) forms 70 per cent, of the whole body. It is an important constituent of all the solids and fluids. It is chiefly derived from without, in the food or drink, but a small quantity is formed within the body by the oxidation of the hydrogen of organic compounds. 4. Pigmentary Principles. In animals, colour depends on two circumstances : first, the deposition of pigment ; and, second, on purely optical phenomena, originating in peculiarity of structure. Of some insects, as the cochineal-insect. Coccus casc a young horse's tooth, these nucleated bodies may be seen i the margin of the crusta petrosa, uniting with its substance i form bone (PI. V. fig. 12). When, moreover, we compare tl concentric rings and laminae surrounding the Haversian canaJ with the like arrangement existing in calculi and all concretion there can be little doubt that the mineral deposits in bone ai in no small degree, connected with the molecular law of aggri gation. Many years ago I discovered that the pellicle whic forms on the surface of lime-water presents the appearan( represented (PL II. fig. 7), and closely resembles pavemei epithelium. It is evidently caused by the nucleated calcareoi concretions becoming flattened, and adhering at their edges, i the same manner that epidermic cells do. Other facts of great importance have in recent years bee discovered, having relation to the physical condition of viscoi matter in the animal body. Of these may be mentioned — ■" 1. The discovery by Graham of the facility with which salii limpid solutions pass through membranes, whereas those i gum, dextrin, gelatin, albuminous substances, &c., pass throng with great difficulty, or not at aU. The former he name crystalloids, the latter colloids. 2. The discovery by myself of the manner the numeroi hyaline or diaphanous bodies, so common in morbid product are produced.f A glutinous matter forms within the substanc of cells, which, under indicates the direction of the current. -Pole. — Neutral Point. h 1- Pole. 174 ANIMAL ELECTRICITY. 1- Pole. - Neutral Point. nerve, being much lowered, the stimulus is so weak that the muscle does not contract. %d. Feeble downward current. — Closed, Contraction ; Opened, Eest (Pfluger). On closing, a_ large portion of the nerve next the muscle, a, passes into the cathelectro- tonic state, the nerve is stimulated, and contraction of the muscle is the result ; but, on opening, a small portion of the nerve, at a distance from the muscle, 6, passes from the anelectrotonic state, and the stimulation is so weak that the muscle does not contract. But, as already men- tioned, p. 172, many physiologists have contraction only on opening and none on closing, a result which is not explained by Pflilger's law. The discrepancy probably arises from the great difficulty of graduat- ing the strength of the current 3rf. and 4 irpora striata, optin thala/mi, corpora quadrigemina, cerebellum,, ons Varolii, medulla oblongata, and medulla spinalis. In this 'ay we have a cranial and a vertebral portion of the spinal cord. In the cerebrum, or brain proper, the gray or ganglionic ;ructure is external to the white or tubular. It presents on le surface numerous anfraotuosities, whereby a large quan- ^ty of matter is capable of being contained in a small space, his crumpled-up sheet of gray substance has been appropriately STRUCTURAL ARRANGEMENT. 283 called the hemispherical ganglion (Solly). In the cranial por- tion of the spinal cord, the gray matter exists in masses, consti- tuting a chain of ganglia at the base of the encephalon, more or less connected with each other, as weU as mth the white matter of the brain proper above, and the vertebral portion of the cord below. In this last part of the nervous system, the gray matter is internal to the white, and on a transverse section presents the form of the letter X, having two posterior and two anterior comua, — an arrangement which allows the white substance to be distributed in the form of nerves to aU parts of the frame. The white tubular structure of the vertebral portion of the cord is divided by the anterior and posterior horns of gray matter, together with the anterior and posterior sulci, into three divi- sions or columns on each side. On tracing these upwards into the medulla oblongata, the anterior and middle ones may be seen to decussate only at that place with each other, whilst the posterior columns decussate through the whole extent of the cord. (See Plate XV. fig. 11, and Plate XVI. figs. 1 and 2.). On tracing the columns upwards into the cerebral lobes, we observe that the anterior or pyramidal tracts send off a bundle of tubes, which passes below the olivary body, and is lost in the cerebellum (Arciform band of Solly). The principal portion of the tract passes through the corpus' striatum, and anterior por- tion of the optic thalamus, and is ultimately lost in the white substance of the cerebral hemispheres. The middle column or olivary tract, may be traced through the substance of the qpiic thalamus and corpora. quadrigemina, to be in like manner lost in the cerebral hemispheres. The posterior column, or restiform tract, passes almost entirely to the cerebellum. In addition to the diverging tubules in the cerebral hemi- spheres which may be traced from, below upwards, connecting the hemispherical ganglion with the structures below, the brain proper also possesses bands of transverse tubules, constituting the commissures connecting the two hemispheres of the brain together, as well as longitudinal ones connecting the anterior with the posterior lobes. In the spinal cord it results, from the investigations of Lockhart Clarke, that there is a communica- tion between the various bundles of tubes throughout its whole extent — 1st, Between the anterior and posterior spinal! roots ; 2d, Between the two lateral columns of gray matter j 3d, 284 THE NERVOUS SYSTEM. Between these and the brain above ; and 4th, Between these and the nerves below. (See Plate XVI. figs. 1 and 2.) It is now also determined that many of the tubes in the nerves may- be traced directly into the gray substance of the cord, and terminate there — a fact orginally stated by Grainger, but confirmed by Budge and KBlliker. These observations, indeed, demonstrate that the numerous actions hitherto called rejUas are truly direct, and are carried on by a series of nervous tubules running in different direc- tions. There can be no doubt that they pass and operate through the cord ; and hence the term diaslaltic proposed by Marshall HaU instead of reflex, is in every way more appropriate. General Functions op the Nbrvotts System. The great difference in structure existing between the gray and white matter of the nervous system would, d, priori, lead to the supposition that they, performed separate functions. The theory aX present /entertained on this point is, that while the gray matter eliminates or evolves nervous force or energy, the white matter conducts to and from this ganglionic structure the influences which are sent or originate there. Not that the white matter is wholly without power of originating influences, because irritating the trunks, and especially the extremities of nerves, not only causes the transmission, but excites the influ- ence which is transmitted. But that the function of the white matter is essentially that of conductivik/. The brain proper furnishes the conditions necessary for the manifestation of the intellectual faculties properly so-called, of the emotions and passions, of volition, and is essential to sensa- tion. That the evolution of the power especially connected with mind is dependent on the hemispherical ganglion, is rendered probable by ii.e following facts ; — 1. In the animal kingdom generally, a correspondenoe is observed between the quantity of gray matter, depth of convolutions, and the sagacity of the animal. 2. At birth, the gray matter of the cerebrum is very defective ; so much so, indeed, that the convolutions are, as it were, in the first stage of their formation, being only marked out by superficial fissures almost confined to the surface of the brain.. As the cineritious substance increases, the intel- ligence becomes developed 3. The results of experiments by GENERAL FUNCTIONS. 285 MonreDB, Rolando, Hertwig, and others have shewn that, on slicing away the brain, the animal becomes more dull and stupid in proportion to the quantity of cortical substance removed. 4. Clinical observation points out, that in those cases in which the disease has been afterwards found to commence at the circumference of the brain, and proceed towards the centre, the mental faculties are affected ^sJ; whereas in those diseases which commence at the central parts of the organ, and proceed toward the circumference, they are affected laat. The white tubular matter of the brain proper serves, by means of the diverging fibres, to conduct the influences originat- ing in the hemispherical ganglion to the nerves of the head and trunk, whilst they also conduct the influence of impressions made on the trunk, in an inverse manner, up to the cerebral convolutions. The other transverse and longitudinal fibres which connect together the two hemispheres, and various parts of the hemispherical ganglion, are probably subservient to that combination of the mental faculties which characterises thought. The spinal cord, both in its cranial and vertebral portions, furnishes the conditions necessary for combined movements ; and that the nervous power necessary for this purpose depends upon the gray matter, is rendered probable by the following facts: — Ist, Its universal connection with all motor nerves. 2d, Its increased quantity in those portions of the spinal cord from whence issue large nervous trunks. 3d, Its collection in masses at the origin of such nerves in the lower animals as furnish peculiar organs requiring a large quantity of nervous power, as in the Triglia volitans, Rata torpedo, SUv/rus, &c. 4th, Clinical observation points out that, in cases where the central portion of the cord is affected previous to the external portion, an individual retains the sensibility of, and power of moving, the limbs, but wants the power to stand, walk, or keep himself erect, especially when the eyes are shut; whereas, when diseases commence in the meninges of the cord, or externally, pain, twitchings, spasms, numbness, or paralysis, are the first • ■ symptoms present, dependent on lesion of the white conducting matter. The white matter of the cord acts as a conductor, in the same manner that it does in the brain proper ; and there can be no doubt that the influence arising from impressions is carried 286 THE NERVOUS SYSTEM. not only along the fibres, formerly noticed, which connect th brain and two portions of the spinal cord together, but alon those more recently discovered, which decussate or anastomos in the cord itself (Brown S^qnard), and are connected with th ganglionic cells of the gray matter. The nerves of the body consist, for the most part, of nerv« tubes running in parallel lines. Yet some contain ganglioni eoipuscles, as the olfactory and the ultimate expansion of th optic and auditory nerves ; whilst the sympathetic nerve cor tains in various places not only ganglia, but gelatinous fla fibres. The posterior roots of the spinal nerves possess a gar glion, the function of which is quite unknown. These roots ai connected with the posterior horn of gray matter in the core while the anterior roots are connected with the anterior homi As regards function, the nerves may be considered as — Is Nerves of special sensation, such as the olfactory, optic, audi tory, part of the glosso-pharyngeal and lingual branch of th fifth. 2d, Nerves of common sensation, such as the greate portion of the fifth, and part of the glosso-pharyngeal. 3e Nerves of motion, such as the third, fourth, lesser divisioii' c the fifth, sixth, facial, or ;portU> dura of the seventh, and th hypo-glossal. 4th, Senso-motory or mixed nerves, such as th pneumo-gastric, third division of the fifth, and the spins nerves. 5th, Sympathetic nerves, including the nnmerou ganglionic nerves of the head, thorax, and abdomen. Thes govern the exeito-motory, excito-nutrient, excito-secretoiy^ am vaso-motor acts of the internal viscera and organs of sense. It is very probable that some nerves may have other propei ties than those now referred to, which may be peculiar to pai ticular tubules. Thus Brpwn Sdqttard considers the influence arising from tickling, temperature, and pain to be in thei character distinctive, and to be conveyed by peculiar nerve tubes. Sensibility. — ^AU nerves are endowed with a peculiar vita property called sensibility, inherent in their structure, by virtu • of which they may be excited on the application of appropriat stimuli, so as to transmit the influence of the impressions the^ receive to or from the brain, spinal cord, or certain ganglia, tha may be considered as nervous centres. {See p. 179.) The nerve of special sensation convey to their nervous centres the influenc of impressions caused by odoriferous bodies, by light, sounc GENERAL FUNCTIONS. 287 and by sapid substances. The nerves of common sensation convey to their nervous centres the influence of impressions caused by mechanical or chemical substances. The nerves of motion caxry from the nervous centres the influence of impres- sions, whether psychical or physical (Todd). The mixed nerves carry the influence of stimuli both to and from, combining in themselves sensory and motor filaments. Although the sympathetic nerves also undoubtedly carry the influences of impressions, the direction of these cannot be ascertained, from their numerous anastomoses, as well as from the ganglia scattered over them, all of which act as minute nervous centres. But there are cases where certain psychical stimuli (as the emotions) act on organs through these nerves, and where cer- tain diseases (as colic, gallstones, &c.) excite through them sensations of pS,in. Rapidity of the nerve current. — This problem has engaged the attention of physiologists for one hundred and fifty years, but has only recently been solved, through the labours of Hebnholz, who, by applying the principle of PouUlet's chronoscope, ulti- mately constructed a myoffraphion, by which we are enabled to measure the velocity of the nerve current. (See Plate XX. fig. 1.) Instead of being inconceivably swift, as Miiller sup- posed, it now admits of demonstration to be in the frog from 26 to '30 yards in a second. (See Practical Physiology.) This, when compared with the rapidity with which electricity (464,000,000 yards), light (300,000,000), sound (3,485), or even a cannon ball (552 yards in a second) travels, is comparatively trifling. It is diminished by a low temperature (Helmholz), and by the electrotonic state (Von Bezold), and is increased in the motor nerves as the nerve approaches the muscle (Munk). A modification of the apparatus has enabled Schelske and Jaager to determine the time required for sensation and a subsequent act of volition. In one set of experiments, a person on receiving a slight electrical shock on the right side, immedi- ately moved a spring key with his right hand, and on receiving a shock on the left side, moved another key with his left hand ; and he knew beforehand on which side he was going to be stimulated, and therefore would have to answer. In another set of experiments, the side was not known beforehand, and the person, after having received the shock, had first to consider which side had been struck, and with which hand accordingly 288 THE NERVOUS SYSTEM. lie had to act. The mean time occupied in the first case was equal to -205 sec. in the second to -272 see. So that the differ- ence of -067 was obviously the time spent in the operation of the brain, required in the second, and not required in the first case. Hirsh determined that the difference in answering by the volition signal from sensations given through the eye was equal to -077 of a second, and through the ear -149 of a second. " It thus appears that ' quick as thought ' is, after aR, not so very quick."* ^ Sensation may be defined to be the eoneciousness of an impres- sion; and that it may take place, it is necessary, — 1st, That a stimulus should be applied to a sensiti+^e nerve, which produces an impression ; 2d, That, in consequence of this impression, a something should be generated we designate an influence, -which influence is conducted along the nerve to the hemispherical ganglion ; 3d, On arriving there, it calls into action that faculty of the mind called consciousness or perception, and sensation is the result. It follows that sensation may be lost by any circumstance which destroys the sensibility of the nerve to impressions ; which impedes the process of conducting the influence generated by these impressions ; or, lastly, which renders the mind unconscious of them. Illustrations of how sensation may be affected in all these ways must be familiar to every one, from circumstances influencing the xQtimate extremity of a nerve, as on exposing the foot to cold ; from injury to the spinal cord, by which the communication with the brain is cut off ; or from the mind being inattentive, excited, or suspended. The independent endowment of nerves is remarkably well illustrated by the fact, that whatever be the stimulus which calls their sensibility into action, the same result is occasioned. Mechanical, chemical, galvanic, or other physieal stimuli, when applied to the course or to the extremities of a nerve, cause the very same results as may originate from suggestive ideas, per- verted imagination, or other psychical stimuli. Thus a chemicfil irritant, galvanism, or pricking and pinching a nerve of motion, •will cause convulsion or spasms of the muscles to which it is distributed. The same stimuli applied to a nerve of common sensation will cause pain, to the optic nerve flashes of light, to * Sir Du .Bois Eeymond's Lecture at the Koyal Institution of Great Brit&iD, April 13. 1866. LA WS REGULA TING MORBID A CTION. 289 the auditory nerve ringing sounds, and to the tip of the tongue peculiar tastes. Again, we have had abundant opportunities of -witnessing the fact, that suggestive ideas, or stimuli origin- ating in the mind, induce similar effects on the muscles, give rise to pain or insensibility, and cause perversion of all the special senses. (See " Mono-ideism.") Motirni is accomplished through the agency of muscles, -which are endowed with a peculiar vital property called contracliliiy (see p. 177), in the same way that nerve is endowed with the property of sensibility. Contractility may be called into action altogether independent of the nerves (HaUer), but may also be excited by physical or psychical stimuli, operating through the nerves. Phydcal stimuli (as pricking, pinching, galvanism, &c.), applied to the extremities or course of a nerve, may cause con- vulsions of the parts to which the motor filaments are distri- buted directly, or they may induce combined movements in other parts of the body diaslaltieally (Marshall Hall),— that is, through the spinal cord. In this latter case the following series of actions take place : — 1st, The influence of the impression is conducted to the spinal cord by the? afferent or esodic filaments which enter the gi-ay matter. 2d, A motor influence is trans- mitted outwards by one or more efferent or exodic nerves. 3d, This stimulates the contractility of the muscles to which the latter are distributed, and motion is the result. Lastly, Con- tractility may be called into action by psychical stimuli or mental acts, — such as by the will and by certain emotions. Integrity of the muscular structure alone is necessary for contractile movements ; but there must be also integrity of the spinal cord, for diastaltic or reflex movements ; and of the brain proper, for voluntary or emotional movements. Thus, then, we may consider that the brain acting alone fur- nishes the conditions necessary for intelligence ; that the spinal cord furnishes the conditions essential for the co-operative movements necessary to the vital functions ; and that the brain, spinal cord, and nerves, acting together, furnish the conditions necessary for voluntary motion, and for sensation. Laws rboulatins Morbid Actioits of the Nervous Ststem. 1. The peculiarity of the cranial circulation, previously de- scribed (p. 220), shews how general or local congestions may occasion the most -violent effects, -without giving rise to struc- 290 THE NERVOUS SYSTEM. tural lesion, or increasing the amount of fluid within the cran- ium. Thus all the symptoms of apoplexy followed hy death may take place, and on post-mortem, examination no change in the brain or its membranes be found. Such cases were called by Abercrombie, dmple apopleicy. A young person receives distressing inteUigenoe, and faints — that is, loses consciousness, sensation, and volition. This depends on weakness of the heart, causing venous cerebral congestion. The most violent convul- sions and passions, associated or not with disorder of the mental functions, such as epilepsy, hydrophobia, tetanus, &c., leave no trace of their existence, and are often attributable to con- gestions, which, by increasing blood pressure in some parts of the cerebrum, and diminishing it in others, ofiers the only explanation of such phenomena. 2. All the functions of the nervous system may he increased, perverted, or destroyed, according to the degree of stimulus or dis- ease operating on its various parts. — Thus, as a general rule, it may be said that a slight stimulus produces increased or per- verted action ; whilst the same stimulus, long continued or much augmented, causes loss of function. AU the various stimuli, whether mechanical, chemical, electrical, or psychical, produce the same effects, and in different degrees. Circumstances influencing the heart's action, stimulating drinks or food, act in 'a like manner. Thus, if we take the efiects of alcoholic drink for the purpose of illustration, we observe that, as regards combined movements, a slight amount causes increased vigour and activity in the muscular system. As the stimulus aug- ments in intensity, we see irregular movements occasioned, staggering, and loss of control over the limbs.' Lastly, when the stimulus is excessive, there is complete inability to move ; and the power of doing so is temporarily annihilated. With regard to sensibility and sensation, we observe oephalagia, ting- ling, and heat of skin, tinnitus aurium, confusion of vision, muscce volitantes, double sight, and lastly, complete insensibiUty and coma. As regards intelligence, we observe at first rapid flow of 'ideas, then confusion of mind, delirium, and, lastly, sopor and perfect unconsciousness. In the same manner, pressure, mechanical irritation, and the various organic dis- eases, produce augmented, perverted, or diminished function, according to the intensity of the stimulus applied, or amount of structure destroyed. LA WS REGULATING. MORBID ACTION. 291 Then it has been shewn that excess or diminution of stimu- lus, too much or too little blood, very violent or very weak cardiac contractions, and plethora or extreme exhaustion, will, so far as the nervous functions are concerned, produce similar alterations of motion, sensation, and intelligence. Excessive hsemorrhage causes muscular weakness, convulsions, and loss of motor power, perversions of all the sensations, and, lastly, un- consciousness from syncope. Hence the general strength of the frame cannot be judged of by the nervous symptoms, although the treatment of these wUl be altogether different, according as the individual is robust or weak, has a full or small pulse, &c. These similar effects on the nervous centres, from apparently such opposite exciting causes, can only be explained by the peculiarity of the circulation previously noticed. A change of circulation within the cranium takes place, and whether arte- rial or venous congestion occurs, pressure on some portion of the organ is equally the result. The importance of paying attention to this point in the treatment must be obvious. 3. 2%e seat of the disease in the nervous system influences the nature of the phenomena or symptoms produced. — As a general rule, it may be stated, that disease or injury of one side of the encephalon especially influences the opposite side of the body. It is said that some very striking exceptions have occurred to this rule ; but these, at any rate, are remarkably rare. Be- sides, it is probable that, inasmuch as extensive organic disease, if occurring slowly, may exist without producing symptoms ; whilst it is certain most important symptoms may be occa- sioned without organic disease, even these few exceptional cases are really not opposed to the general law. Then, as a general rule, it may be said that diseases of the brain proper are more especially connected with perversion and alteration of the in- telligence ; whilst diseases of the cranial portion of the spinal cord and base of the cranium are more particularly evinced by alterations of sensation and motion. In the vertebral portion of the cord, the intensity of pain and of spasm, or want of con- ducting power, necessary to sensation and voluntary motion, indicates the amount to which the motor and sensitive fibres are affected. Further than this we can scarcely generalise with prudence. The fatality of lesions affecting various parts of the nervous centres varies greatly. Thus the hemispheres may be exten- . 292 THE NERVOUS SYSTEM. sively diseased, often without injury to life, or even permanent alteration of function. Convulsions and paralysis are the com- mon results of disease of the ganglia in the cramial portion of the cord. The same results from lesion of the pom Varolii. But if the medulla oblongata, where the eighth pair originates, be affegted, or injury to this centre itself occur, it is almost always immediately fatal. 4. The rapidity or slowness with which the lesion occurs injl/ur ences the phenomena or symptoms produced.- — It may be said, as a general rule, that a small lesion — ^f or instance, a small hsemor- rhagic extravasation — occurring suddenly, and with force, pro- duces, even in the same situation, more violent effects than a very extensive organic disease which comes on slowly. This, however, will depend much upon the seat of the lesion. Very extraordinary cases are on record where large portions of the nervous centres have been much disorganised without pro- ducing anything like such violent symptoms as have been occasioned at other times by a small extravasation in the same place. Here, again, the nature of the circulation within the cranium offers the only explanation^ for the encephalon must undergo a certain amount of pressure, if no time be allowed for it to adapt itself to a foreign body ; whereas any lesion coming on slowly, enables the amount of blood in the vessels to be diminished according to circumstances, whereby pressure is avoided. 5. The various lesions and injwies of the nervous system pro- duce phenomena sir/iUar in kind. — The injuries which may be in- flicted on the nervous system, as weU as the morbid appearances discovered after death, are various. Tor instance, there may be an extravasation of blood, exudation of lymph, a softening, a cancerous tumour, or tubercular deposit, and yet they give rise to the same nervous phenoinena,- and are modified only by the circumstances formerly mentioned, of degree, seat, sudden- ness, &c. Certain nervous phenomena also are of a paroxysmal character, whilst the lesions supposed to contain them are stationary or slowly increasing. It follows that the effects can- not be ascribed to the nature of the lesions, but to something which they all have in common ; and this apparently, may con- sist of — 1st, Pressure, with or without organic change ; 2d, More or less destruction or disorganisation of nervous texture. Further, when we consider that the same nervous symptoms SPECIAL FUNCTIONS. 293 arise from irregularities in the circulation ; from increased as well as diminished action ; sometimes when no appreciable change is found, as well as when disorganisation has occurred ; the theory of local congestion to explain functional alterations of the nervous centres seems the most consistent with known facts. That such local congestions do frequently occur during life without leaving traces detectable after death, is certain ; whilst the occurrence of molecular changes, or other hypothe- tical conditions which have been supposed to exist, have never yet been shewn to take place under any circumstances. The following aphorisms will be found useful in endeavour- ing to reason correctly on the functions of the nervous system : 1. The brain proper is that portion of the encephalon situated above and to the outside of the corpus calloswm. 2. The spinal cord is divided into a cranial and vertebral portion. 3. The gray matter evolves, and the white conducts, nervous power. 4. Contractility is the property peculiar to fibrous texture, whereby it is capable of shortening its fibres. Motion is of three kinds — contractile, dependent on muscle ; diastaltic, de- pendent on muscle, nerve, and spinal cord ; volvnta/ry, depend- ent on mliscle, nerve, spinal cord, and brain. 5. Sensibility is the property peculiar to nervous texture, whereby it is capable of receiving impressions and of trans- mitting the influences they produce. Sensation \a^e conscious- ness of such impressions. Special ruNCTioNs of the Nbrvoits System. On proceeding to determine more closely what are the special functions of the individual parts of the nervous system, we should never forget that the various ways in which they have been investigated have led to opposing results, and that such is the excessive difiiculty of the inquiry, that we should be espe- cially on our guard against specious hypotheses and unfounded theories. Anatomy,' human and comparative — and more espe- cially histology — ^have furnished us with many valuable facts ; but it is not easy to determine what are the nervous gangU^i or other parts in the lower animals which correspond with what exists in man ; whilst erroneous interpretations as to the habits 294 THE NERVOUS SYSTEM. and motions of these creatures are too readily formed. Again, in making experiments on animals, it is often impossible to ascertain how far the shock of the operation, the flow of blood, or the destruction of other parts may vitiate the results. Lastly, an observation of the effects of disease often leaves us in doubt how far the organic mischief extends, and what phe- nomena may be rightly attributed to it, and what to the con- gestion of the blood vessels which accompany it. This last, however, is by far the most important means of research open to us ; and if to the result of pathological observation, a similar one is obtained from well-performed experiments, our views derived from either wiU be confirmed. If to this, histology reveals connections in structure that will warrant and bear out such conclusions, we may consider that every proof is given which conviction requires. It should be remembered, therefore, that such is the fallacy inherent in each individual method of research that little dependence can be placed upon it, and that at least two of these must be united to give probability to any given theory. The results of these four different methods of in- vestigation must be kno*n in order to draw correct conclusions. Cbrbbkum. Histological results. — On carefully examining a thin vertical section of the cerebral lobes prepared after the manner of Lock- hart Clarke, and steeped in carmine, the white substance in the adult may be seen to be composed wholly of nerve tubes.' These become more and more minute as they reach the 'gray matter of the convolutions, and are gradually lost in it. The layer of gray matter consists of a finely molecular substance, in which are imbedded minute nerve cells, varying in shape and size as they are traced from the circumference inwards. Externally, the cells are small, and associated with granules and naked nuclei. Internally,' they are largSr, circular, oval, and especially of a triangular form, sending off processes continuous with the nerve tubes. (See Plate XV. fig. 1.) Experimental resvlts. — The experiments of Flourens, Hertwig, Longet, and others, have shewn that on removing the cerebral lobes from birds, the mental faculties, including, of course, con- sciousness and volitioh, and therefore sensation and voluntary motion, are abolished, while the creature can stand when put on its legs, fly when thrown into the air, and walk when pushed. CEREBRUM. 295 Hertwig has kept pigeons in this condition for three months, deglutition and all other reflex acts being perfect, the mental faculties only absent. Longet and Dalton have recently main- tained that sensation may exist without the cerebral lobes. The former says, when the cerebrum was removed from a pigeon, and a light suddenly brought near its eyes, there was contraction of the jiupU, and even winking. Further, when a rotatory motion was given to the candle at such a distance that no heat could operate,, the pigeon made a similar movement with its head. Bat of these facts I would observe that the pupil will contract on the application of light when the eye has been cut out .of the head, and a sunflower foUows the course of the sun. It cannot, therefore, be said that under such circum- stances the eye and the flower possess sensation or can see. Dalton's description of what occurs after removal of the cere- brum is as follows : — " The effect of this mutilation is simply to plunge the animal into a state of profound stupor, in which he is almost entirely inattentive to surrounding objects. The bird remains sitting motionless upon his perch or standing upon the ground, with the eyes closed and the head sunk between the shoulders. (See Plate XV. fig. 3.) The plumage is smooth and glossy, but is uniformly expanded by a kind of erection of the feathers, so that the body appears somewhat pufied out, and larger than natural. Occasionally the bird opens its eyes with a vacant stare, stretches its neck, perhaps shakes its bill once or twice, or smooths down the feathers upon its shoulders, and then relapses into its former apathetic condition. This state of immobility, however, is not accompanied by the loss of sight, of hearing, or of ordinary sensibility. All these functions remain, as well as that of voluntary motion. If a pistol be discharged behind the back of the animal, he at once opens his eyes, moves his head half round, and gives evident signs of having heard the report ; but he immediately becomes quiet again, and pays no further attention to it. Sight is also retained, since the bird will sometimes fix its eye on a particular object, and watch it for several seconds together. Ordinary sensation also remains after removal of the hemispheres, together with voluntary mo- tion. If the foot be pinched with a pair of forceps, the bird becomes partially aroused, moves uneasily once or twice from side to side, and is evidently annoyed at the irritation." From these observed facts, which are strictly accurate, Dal- 296 THE N^RKOUS SYSTEM. ton concludes that " the animal is still capable, after removal of the hemispheres, of receiving sensations from external objects. But these sensations appear to make upon him no lasting im- pression. He is incapable of connecting with his perceptions any distinct succession of his ideas. • He hears, for example, the report of a pistol, but he is not alarmed by it ; for the, sound, though distinctly enough perceived, does not suggest any idea of danger or injury. There is accordingly no power of forming '. mental associations, nor of perceiving the relation between ex- ternal, objects. The memory, more particularly, is altogether destroyed, and the recollection of sensations is not retained from one moment to another. The limbs and muscles are stiU under the "coiitrol of the will, but the will itself is inactive, because apparently it lacks its usual mental stimulus and direction." I think the facts may be interpreted differently and more correctly. The turning round of the animal's head on the ex- plosion of a pistol, and many other movements, may be alto- gether reflex, dependent on irritations communicated to the cranial portion of the spinal cord through the tympanum. Again, that the pigeon should open its eyes with a vacant stare, or apparently fix them on an object, is no proof of sight. We constantly do these things ourselves with the brain entire, and see nothing. Lastly, that the limbs and muscles are under the control of the will, while the will is inactive, appears to be con- tradictory language. One of the most active operations of the will is to direct motion ; and to say of a bird which flies away on the production of the slightest noise in health, but does not move on the discharge of a pistol, that in the latter case its limbs and muscles are still under the control of the will, appears to be a most unfounded conclusion. The truth evidently is, that there is no will, no sensation in such a case, any more than, there is in, a sensitive plant, which shrinks on being touched, but which surely cannot be said to exercise either the one mental faculty or the other. Pathological results. — The general results of pathological and clinical observation confirm those obtained by experiment. Thus disease of the membranes, especially meningitis over the hemispheres, occasion delirium, which passes into coma. If it be limited to the base or medulla oblongata, it causes convulsions and paralysis, or lesions of motion. Many remarkable cases of injury the human brain has sus- CEREBRUM. 297 taiaed have been published, which shew that the hemispheres are ■ in themselves insensible. If laniversally diseased, the result has been, as in the lower animals, complete loss of mind, volition, and sensation. The same occurs if general pressure is applied, as in cases of fracture of the cranium with depression of bone. Many examples, however, are known where partial destruction of, or pressure on, the cerebral lobes has not perma- nently injured the intelligence. Thus, 1. A gun exploded iu the hands of a man, set. 22, and a piece of iron entered the frontal bone, and destroyed a considerable portion of hoik an- terior and cerebral lobes. From this injury he recovered with- out any perceptible injury of mind.* 2. A boy, set. 11, was kicked by a horse, so as to occasion fracture of the os fromtia, and pultaceous softening of both anterior lobes, as was proved by post-mortem examination. He lived forty-three days after the accident, and was perfectly intelligent up to one hour of his death.f 3. An artist had spectral illusions and blindness for years, but was quite intelligent till he was seized with apoplexy, of which he died. Both anterior lobes of the brain were de- stroyed by a mass of hydatid cysts.J 4. A wig maker, »t. 60, was very loquacious, but otherwise perfectly intelligent, and died suddenly in the Charity Hospital of Paris. On post-mor- tem examination, both anterior lobes of the brain were the seat of a schirrous tumour. § Thus partial destruction of a considerable portion of the cere- bral lobes does not necessarily destroy intelligence, nor does partial destruction of the white matter necessarily interfere with its conducting properties. Then there are many cases of large chronic abscesses or of pultaceous softenings in the white matter of one or both cerebral lobes, in which there has been no paralysis, and no impairment of sensation nor voluntary motion. In all such cases, some of the conducting tubules have escaped the morbid action, and have been sufficient to maintain the transmitting power. In no case, however, where the entire gray matter of the convolutions nor of the white matter of the hemispheres have been destroyed, has the intelligence or con- ducting power remained uninjured. * Edinb. Med. and Surg. Journal, vol. xliii. p. 292. f American Medical Intelligencer. April 1. 1837. j Medico-Chirurgieal Review, vol. xxiv. p. 202. § Bulletin de TAcad^mie de Medicine, vol. xxx. p. 799, 1865, , h 298 THE NERVOUS SYSTEM. There can be no doubt that the relation between the mole- cular, nuclear, and cell elements of the hemispherical ganglion, as the instrument of mind, must be most important ; and yet I am not acquainted with any one, who, having first qualified himself for the task by a prolonged and careful study of histo- logy, has investigated, on a sufficiently extensive scaje, the brain in cases of insanity. Psychologists content themselves with repeating well-known clinical observations, with the ordinary! morbid anatomy or density of the brain, and with the meta- physical speculations which have been pushed as far as, if not further than, human iutellect can carry them. Need we feel surprised that the true pathology of insanity is unknown ? What we desiderate is a careful scrutiny of the organ. Hitherto the difficulties of such an investigation have been insurmount- able, in consequein'ce of our imperfect methods of research. But let any one possessing a competent knowledge of histology, and the use of our best microscopes, with the opportunities our large asylums oifer, only now dedicate himself to the task, and he may be assured, that while extending the bounds of science, he will certainly obtain an amount of fame and honour that few can hope to arrive at. The molecules on which muscular con- tractility depends are, as we have seen, visible molecules, and so I believe are those in the hemispherical ganglion, so essen- tially connected with the functions of the brain. From the various facts now known, I think it may be con- cluded that the cortical substance of the cerebral lobes furnishes those coMitions which are necessary for thought, including all mental . operations, sensation and volition. Further than this we are not warranted in going, for the facts which establish these great conclusions entirely negative, as we shall see, all those theories which have been advanced having for their object a localisation of the different faculties into which the mind has beep arbitrarily divided. Thi Mental Faculties. — When, we endeavour to determine these, and separate the reasoning powers from instinctive ac- tions, the difficulty of the inquiry seems at first to be over- whelming. To analyse the intricate combinations of our own minds is a difficult task ; but how much more laborious is it to study the variations in the minds of others, and to investigate the habits of the countless tribes of animals with the view of distinguishing which depend on reason, and which on blind THE MENTAL FACULTIES. 299 instinct ! The attempts of metaphysicians in this direction are not satisfactory. At the commencement of the present century, Dugald Stewart considered the mental faculties to be Con- sciousness, Perception, Attention, Conception, Abstraction, Association of Ideas, Memory, Imagination, and Judgment or Beasoning. To these he added the Affections, Desires, Self- love, and the Moral Faculty. His successor in this University, Dr Thomas Brown, divided Mental Phenomena (1822) into two great divisions, viz., the external affections and iatemal affections. The external com- prehend all our sensations, and the internal are divided into two branches, the one intellectual, the other emotional. Under the intellectual states we have simple and relative suggestions, and under emotional states we have all the passions and desires. This classification is more comprehensive than that of Stewart's, recognising, as it does, however dimly, the necessity of conjoin- ing physiological facts with metaphysics. In recent times it has been maintaiued that the study of mind ought not to be considered as a branch, of transcendental philo- sophy, but as a positive science, called Psychology ; and those who have thus cultivated it, instead of multiplying the mental faculties, have contracted them under three heads, viz., Intel- lect, Sensation, and Volition. The various modes of consider- ing and applying these faculties by ScheUing, Hegel, and others ia Germany, by Eoyer CoUard, Cousin, and others in Prance, and by Hamilton, Mill, Bain, MorreU, Maudesley, and others in this country, constitute a wide field of knDwledge, which occupies two chairs in this University imder the names of Moral Philo- sophy and Logic. I can only briefly give a summary of the results. (Por the relation existing between mind and brain, see p. 180.) At present, then, we may conveniently consider that the mental faculties are of three kinds— 1st, Purely intellectual — ^we think ; 2d, The sensations — we feel; 3d, Volition — ^we wiU, we determine. 1. Intellect. — Of the intellectual faculties there is a general or predominant one, viz.. Consciousness. It is the ego or idea of our own existence,, and which, influenced in various ways, causes the other mental faculties. Thus, if directed to the present, it is Perc^tion; if. it recals the past, it is Memory ; if it suggests the ideal, it is Imagination; if applied to thought synthetically, it is Qeneralization — if analytically, it is Reason- ,oo THE NERVOUS SYSTEM. ng ; if it originate ideas intuitively, it is Original Concept ion, 2. The Sensations are of two kinds, physical and mental ; that 3, we can feel pain or pleasure from physical agents or from aental operations. The physical sensations are Touch, Taste, imell, Searing, Sight, and the Muscular sense, or sense of weight. Che mental sensations are ffope, Fear, Grief, Pride, Love, hatred, Desire, Aversion, Joy, Sorrow, Despair, Audacity, Cov/r- ige, &c. To these may be added Self-love, or Vanity, and the iordl Pacvlty — a feeling of being right or wrong. 3. Volition. — Sensation, as we have previously seen, is the lonsciousness of an impression, and the same relation that the nfluence has to consciousness volition has to sensation. To rill, there must be an object, physical or mental. Thus will, iirected to the muscles, causes voluntary motion ; if to sensation, ittention ; if to thought, abstraction, or concentration of ideas. Phrenology. — Gall and Spurzheim have divided mind into thirty-three' faculties, to which Mr Combe added two more, making thirty-five in all. These are^ — 1st, Amativeness'; 2d, Philoprogenitiveness, or love of offspring ; 3d, Conoentrativeness, 3r the power of continuing impressions and ideas ; 4th, Adhe- nveness, or the desire to attach ourselves to persons or objects ; 5th, Combativeness, or the inclination to fight and be embroiled in contentions ; 6th, Destructiweness, or the desire of destroying life ; 7th, Construciiveness, or a disposition to apply onesel|' to the mechanical arts ; 8th, Covetousness, or the desire to covet, to amass, or acquire ; 9th, Secretiveness, to conceal ; 10th, Self- Esteem, or self-love ; 11th, Love of Approbation, or the pleasure we derive from the commendations' we receive from others ; 12th, Cautiousness ; 13th, Benevolence, or meekness and gentle-r ness of disposition ; 14th, Veneration, by which we worship the Deity and material objects ; 15th., ITope; 16th, Ideality, oi the poetical disposition ; 17th, the faculty of Conscientiousness, or of justice and equality ; 18th, Determinativeness, or firmness of character or purpose ; 19th, Individ^ullity, or the power we pos- sess of knowing external things ; 20th, Form, by which we take cognisance of the forms of external objects ; 21st, Size, that power which seizes hold of dimensions ; 22d, Weight, that faculty by which we estimate weight, density, resistance, &c. ; 23d, Colour, the faculty of perceiving colours ; 24th, Space or Lo- cality, the' power of local memory ; S5th, Order, or a love Qf , THE MENTAL FACULTIES. Sbt melliodical arrangement ; 26th, Time, or the faculty which enters into speculations on duration ; 27th, Nv/mber, or the power of calculation ; 28th, Twum, or the perception of musical tone ; 29th, Language, the faculty by which we learn artificial signs ; 30th, Comparison, by which we recognise differences, analogies, similitudes, &c. ; 31st, Canmality, that power which directs our attention to the causes of things ; 32d, Wit, the faculty of jesting, raillery, Blocking, &c. ; 33d, Imitation, the power of imitating sounds, gestures, manners, &c. These are the several faculties of mind laid down by Drs Gall and Spurz- heim ; but to this catalogue Mr Combe has added two others, — 34th, Wonder, or that which relates to the marvellous, super- natural, &c. ; and 35th, Evmtwality, or that which takes cog-' uisance of changes, events, and active phenomena. The objections to this division of the mental faculties are, — 1st, Its complexity ; and according to the phrenological system, one faculty is considerably influenced by others ; so that com- pound characters may be easily manufactured at wiU, and thus numerous sources of fallacy thrown open. 2dj It is redundant in some faculties, and deficient in others. It is redundant, for instance, in having two organs for Form and Size, forComba- tiveuess and Destructiveness, for Causality and Concentrative- ness. Each of these two, if not identical, are, at all events, closely allied. It is deficient in having no such faculties as Memory, Eeasoning, and Judgment, which every man is con- scious he possesses. But it is said that every organ has a power of remembering, reasoning, and judging ; so that there are other faculties which govern or attend upon all the thirty-five organs. There are also obvious deficiencies in the propensities or instincts ; for mankind not only love, steal, fight, kill, secrete^ and build, but run, swim, walk, talk, sing, learn, and so on, which have no place in the phrenological system. Perhaps there is no instinct so Strong in man and animals as that of self- preservation, and yet this has no organ ascribed tq it by the phrenologists. As a philosophical and metaphysical system of the mental faculties, therefore, the classifications of Stewart and Brown seem to us greatly superior, especially in all the higher properties of the intellect ; although, so far as the instincts and passions are concerned, they are, perhaps, inferior. Thfi individual mental faculties cannot be localised. — If our knowledge of what the faculties of the mind really arie, and 302 THE NERVOUS SYSTEM. how they should be divided, is so imperfect, it may appear unnecessary to attempt to determine in what part of the brain each is situated. As might be expected, all such eflforts have failed. That the brain furnishes the conditions necessary for ;the evolution and manifestation of mind, we have seen, is estab- lished ; and that the gray matter originates, whUst the white matter conducts, the influences generated, we have also shewn to be highly probable. But we have no facts which point out that Memory, Consciousness, Judgment, Reasoning, or similar faculties belong to one part of the cerebral convolutions more than to another. GaU and his followers have localised all the thirty-five faculties into which they have divided the mind. He observed that certain individuals who displayed mental powers, moral feelings, or particular propensities, had a fulness Dr prominence in a certain part of the anterior, middle, or posterior third of the cranium. By paying attention to the principal characteristics of remarkable men, and the living tiabits of animals, he found that this fulness or prominence coincided in a number of cases ; and he concluded from this that the function of brain which existed below the prominence was the organ' giving rise to the characteristic faculty. He then sought to confirm his theory by anatomy, physiology, Mid pathology ; and he and his disciples have accumulated an immense number of these coincidences, which they believe sufficient to establish the phrenological theory. But, proceeding on the- principles which the phrenologists ihemselves have laid down, it is easy to shew that the excep- ;ions are as numerous as the coincidences ; whilst the other nodes of inquiry to which we have alluded, — namely, anatomy, ;he results of experiments on living animals, and the observa- aons of the symptoms of disease as compared with the appear- mces presented after death, — not only give, no support, but are iirectly opposed to the views of Gall. Thus some remarkable skulls in the Museum of the University of Edinburgh are, on ;he principles of the phrenologists themselves, entirely opposed ;o their doctrines. Of these, among many, we would point to he, skulls of Burke (Plate XV. fig. 5), Pep6 (Fig. 6), and Saggart (Fig. 7), — all three remarkable murderers, with Dct itructiveness small ; and the last a most dexterous thief, with Acquisitiveness small. The flattened appearance of the organ )f Destructiveness in these skulls contrasts remarkably with CEREBELLUM. 303 the ordinary type of Saxon skull (Kg. 8). Anatomy proves that, while the lower vertebrate animals possess the anterior and middle lobes of the brain well developed, which are said to 1 be the seat of the intellectual faculties and moral sentiments, they are deficient in those parts where Love of Offspring, Adhe- siveness, Destructiveness, and Combativeness are found, — ^facts wholly incompatible with the theory of Gall. In the same manner, the great majority of facts derived from, physiological and pathological research give no support to phrenology. We have previously, seen how several cases prove that both ante-' rior lobes of the brain, where the phrenologists have placed the higher mental faculties, may be completely destroyed without affecting the intellect. (See p. 297.) Although, therefore, this doctrine is unquestionably founded upon a large number of data, it cannot lay claim to a correct localisation of the mental faculties in any way superior to other systems, which, like those of Camper and Lavater, have been advanced by ingenious men, have excited attention for a season, and been ultimately aban- doned as inconsistent with the present state of our knowledge. The names of Gall, Spurzheim, and Combe, notwithstanding, ought ever to be registered among those whose labours have greatly contributed to advance our knowledge of the physiology of the braiu. Cerebellum. Histological resvlts. — The ganglionic surface of the cerebellum is structurally altogether imlike that of the cerebrum. On looking at a well-made vertical section of the former, prepared after the method of Lockhart Clarke, and steeped in carmine, under a magnifying power of 25 diameters, the fine tubular substance in the centre is seen to be bounded externally by a granular layer, outside which is a row of nerve cells with branched processes gradually terminating towards the margin of the exterior layer, which is finely molecular. On increasing the magnifying power to 250 diameters, we see more distinctly the relation of these various parts to one another, and recognise in the interior of each granule an included rounded body. (See Plate XV. fig. 2.) According to Gerlach,' these corpuscles are united to one another by a slender filament, which he has 'figured in a hypothetical diagram. Although such an appear- ance as he has imagined cannot be discovered in the natural 304 THE NERVOUS SYSTEM. structure, I have seen the tubes running between the granules, a,nd traded them to the external margin of the granular layer. The external layer is the structure which demands the greatest attention. (Kg. 2, a.) It is composed essentially of a finely molecular mass, containing numerous capillaries derived from the vessels of the meninges. Large ganglionic cells external to the granular layer send off branching processes towards the circumference, which are gradually lost as they proceed out- wards. Both in the external, as well as in the internal layers, the basis of the texture is evidently, molecukn — a fact which hitherto has received far too little attention. Experimental results. — If the cerebellum be removed gradu- lUy from a pigeon in successive slices, there is progressive cir- cumscription of the locomotive actions. On taking away only the upper layer there is some weakness and a hesitation in its jait. When the sections have reached the middle of the organ, the animal staggers much, and assists itself in walking with its wings. The sections being continued further, it is no longer *ble to pteserve its equilibrium without the assistance of its wings and tail ; its attempts to fly or walk resemble the fruit- less efforts of a nestling, and the slightest touch knocks it over. A.t last, when the whole cerebellum is. removed, it cannot sup- port itself even with the aid of its wings and tail ; it makes sdolent efforts to rise, but only rolls up and down ; then, fatigued with struggling, it remains for a few seconds at rest on its back or abdomen, and then again commences its vain struggles to rise and walk. Yet aU the while its sight and hearing are perfect. The slightest noise, threat, or stimulus, at once renews its contortions, which have not the slightest ap- pearance of convulsions. (Plate XV. fig. 4.) These effects, first described by Flourens, have been confirmed by all experi- menters, and occur in all animals. The results contrast very strongly with those of the much more severe operation of re- moving the cerebral lobes. " Take two pigeons/' says Longet ; ■' from one remove completely the cerebral lobes, and. from the other only half the cerebellum ; the next day the first will be firm upon its feet, the second will exhibit the unsteady and uncertain gait of drunkenness." These facts induced Flourens to consider the cerebellum as the co-ordinator of motion, in which view he Was supported by the late Dr Todd and others. Foville, on the other hand, CEREBELLUM. 305 ' supposed it to be the seat of sensation, and argued that, as it is by means of this function that we regulate muscular motion, so, when it is destroyed, the faculty of perceiving the move- ments being lost, we cannot answer for their precision or dura- tion. That it should be the seat of sensation generally is disproved by the fact that the animal is evidently conscious of impressions after its removal ; but that it should be the organ of that peculiar sense, which has been variously called " mus- cular sense," " sense of resistance," and " sense of weight," is very probable. Accordingly we find that Professor Lussana, of Parma, has brought together all the arguments which exist as to this matter, along with numerous original observations, confirmatory of the view that the cerebellum does indeed regu- late motion, but in consequence of its being the seat of the muscular sense.* It has been suggested by Carpenter and Dunn that the cor- pus dentatum in the cerebeUimi is the ganglion which is connected with this sense, a view rendered improbable by Brown S^quard's analysis of cases where the organ was diseased. I submit that the function is seated in the external layers of grey matter rather than in the corpus dentatum — a theory to which the same objections do not apply. Miud frequently remains when portions of the hemispherical ganglion are in- jured, although we know of no instance in which, where the whole of it has been diseased, intellect has been preserved. So the co-ordinating motor power may remain when parts only of the cerebellar leaflets are destroyed, but is certainly lost when the whole gray matter is diseased. That the cerebellum, there- fore, is connected with a special sense, through which it influ- ences the co-ordinate action of the muscles, is a doctrine worthy the attention -of physiologists. Its external layers of grey mat- ter, constituting a complex ganglionic structure, has probably the same relation to the muscular sense as the hemispherical ganglion has to sensation in general. Pathologioal results. — Diseases of the cerebellum, such as extravasations of blood into its substance,, softenings, tumours, tubercular deposits, although they generally have as a symptom paralysis or convulsions, these are often well marked, and are very violent from apparently trifling lesions, and are as often slight when the whole or greater portion of the organ has been * Joum. de Physiologic. Tom. vi. 1863. 3o6 THE NERVOUS SYSTEM, completely disorganised. The result of pathological inquiry throws no light upon any of the proposed functions of the cere- bellum. In two remarkable oases where it was atrophied,* although there were epileptic and other convulsions, co-ordina- tion of motion existed in the intervals. According to Gall, the cerebellum is the seat of the sexual instinct. This was not only present but excessive in both the cases referred to, shewing that diminution in the size of the organ did not produce diminu- tion of the alleged function. In a singular cranium in our University Museum, the prominence over the organ of amative- Qess is remarkable (Plate XV. fig. 9), but on dissection the serebellum was found to be normal, the enlargement being 3aused by thickening of the bone, and great distension of the Toroular Herophili. Corpora Striata and Optic Thalami. These parts of the encephalon consist of masses of ganglionic matter differently arranged, connected with the spinal cord below and the cerebrum above. The corpus striatum is in front of the optic thalamus, but a portion of its substance »oes backwards and over it. This intimate relation of the two ganglia renders it difficult to experiment upon one without in- juring the other. In the same way, disease of one is liable to Muence the other, and in either case hemiple^a on the opposite dde of the body is the general result. It follows that as yet we dave no means of determining with certainty the functions of 3ach ganglion, although it is probable that the corpora striata ire connected with voluntary combined movements, and the aptic thalami with sensation and with the sense of sight, but aot exclusively so. Dr Todd says of these bodies : — " The corpora striata and interior horns are centres of motion ; the optic thalami and posterior horns are centres of sensation. The anterior pyi'amids jonnect the former ; the olivary columns, and perhaps some abres of the anterior pyramids, the latter." He further argues ' that the intimate connection of sensation and motion, whereby sensation becomes a frequent exciter of motion, and voluntary motion is always, in a state of health, attended with sensation, would d, priori lead us to look for the respective centres of these * By Oombette, CnivTeilhier's Anat. Patholog. Liv. xv. Plate V. ; by Hyde Sal- ter, l^ans. of Lond. Patholog. Soc, vol. iv. p. 31. CORPORA QUADRIGEMINA. 307 two great 'faculties, not only in juxtaposition, but in union, at least as intimate as that which exists between the corpus stria- tum and optic thalamus, or between the anterior and the posterior horns of the spinal gray matter." That motion and sensation are intimately connected with these bodies, there can be no doubt, but that volition or sensation resj^des in them, or have their centres there, is opposed to all we know of the nature of volition and sensation, as well as to the facts connected with the cerebral lobes previously noticed. (See pp. 296, 297.) Corpora Quadrigbmina. These ganglia, from their intimate connection with the optic nerves, have also been called optic tubercles, and been supposed to have some special relation to the sense of vision. Flourens determined that destruction of these on one side was followed by loss of sight on the opposite side, and that their removal on both sides deprived the animal of vision, without affecting the locomotive or intellectual powers, and leaving aU sensibility, except to light, unaffected. Their total removal also paralysed both irides. Similar results have followed disease of these bodies, but it must be remembered that like effects have folr lowed lesions of the optic tracts, of the thalami, of the cerebel- lum, and indeed of other parts of the brain and medulla oblongata. We cannot, therefore, suppose them to be exclusive centres of the sense of vision, or of those movements in the / irides which are so necessary to sight, as Flourens supposed. Rotatory and other convulsive moviments. — When injuries of these tubercles are deep, so as to reach the medulla oblongata, with which they are intimately connected, general convulsive movements are produced. If the injury is only on one side, the opposite side of the body only is affected. ^ Sometiiii^ the animal rolls round its body towards the injWed side. Simuap turnings were produced by Magendie oa cutting across -^he prus oerebellij but were much quicker, the animal often making sixty revolutions in a minute. On puncturing the corpora quadri- gemina and the pons Varolii with a pin, on the left side, Browii Sdquard found that the right eye was convulse(^, while the other was normal. There was also turning similar to what is often seen practised in the manSffe. The animal moves sideways, and describes a circle, with its body forming; part of its radius, the head at the circumference, and the tail towards the centre of 3o8 THE NERVOUS- SYSTEM. Ehe circle. According to Magendie, certain injuries to the qerebellum cause the animal to push itself backwards, whilst injuries to the corpora striata oblige it to rush forwards. Turn- ing movements have been induced by Mourens, after injuring the semicircular canals of the ear in birds. Longet has caused them in pigeons, by evacuating the humour of the eye. Similar convulsions have occasionally been observed in man as the result of disease, especially at the commencement of epileptic attacks. These remarkable movements, therefore, are probably Mcasioned by irritations and injuries which, by producing para- lysis in some muscles, and convulsive contractions in others, oblige the animal to move in certain directions. Vertigo and partial blindness, however caused, may assist in their production. Pons Vakolii and Medulla Oblongata, These portions of the encephalon possess the same function as the spinal cord, with the addition of being more essential to life, on account of their being the centres (especially the latter) svhich furnish the necessary power for maintaining the co-ordi- aate movements of respiration and deglutition. It is by arrest- ing respiration, and paralysing the functions of the important srgans to which the vagi nerves are distributed, that sudden injury to the medidla ohlongata proves so rapidly fatal. iHere also jccurs that decussation of the anterior and middle columns of the cord to which is attributable the crossed action of lesions in the cerebral lobes — apoplectic extravasations, Softenings, &c., in the right cerebral hemisphere, causing hemiplegia of the left ride, and vice versa. Destruction of the medulla oblongata in the hands of all ex- perimeiiters ' has caused sudden death, but removal of the sntire brain and crpjiiial portion of the cord above this centre iocs not do, so. The "Vertebral portion of the cord below may ilso be remoVedAip to^hfe origin of the phrenic nerve, without iestruCtion, to life. In amphibia these two experiments have bpen combined, and yet the animal will continue to breathe, and iife be mafti^t^ine^d.. But when the medulla oblongata is in* inred, respiration aid liffe at once cease. Hence the humane sfforts of the hangman in this country to cause dislocation of the first or second (C^vical vertebra, So as to cause immediate Jeath. , ' THE SPINAL CORD. 309 The Spinal Cord. Histological remits. — The spinal cord has two portions — a cranial and a vertebral. The former consists of a chain of gan- glia more or less connected with one another, as well as with the cerebrum above and the vertebral part of the cord below ; the latter is composed of two lateral halves divided by an ante- rior and posterior fissure. Each lateral half is subdivided into three columns — an anterior, middle, and posterior — by the two comua of the central mass of gray matter, in which are numerous multipolar ganglionic cells. Through the centre runs the spinal canal, lined with columnar epithelium. The white matter of the lateral columns is composed of tubes, which, as shewn by Lockhart Clarke, on being traced inwards frdm the spinal nerves, join the ganglionic cells in the gray matter, and, through them, keep up a communication — 1st, with the opposite lateral columns ; 2d, with the cerebrum ; and 3d, with the anterior and , posterior roots of the nerves. (Plate XVI. fig. 2.) A transverse ' section of the tubes of the cord, shewing the axis cylinder, and white substance of Schwann, is given Plate V. figs. 21, 22. The, multipolar cells, which embedded in molecular matter, constitute the gray substance of the cord, are similar to the one repre- sented Plate III. fig. 28, e. JSxperimental results. — --Sir Charles Bell distinctly proved by experiment that the anterior roots of the spinal nerves were motor, and that the posterior roots were sensitive. On dividing the former in a living animal, voluntary motion of the parts to which it was distributed was lost ; on dividing the latter, pricking or injury to those parts caused no sensation. On irri- tating the lower cut end of the anterior root, convulsion was produced ; on irritating the upper end of the posterior root, pain. He also made the discovery that certain cerebral nerves were motor throughout their course, while others were wholly sensitive. These he called nerves of motion and of sensation, and when the two were combined in a single nerve, it was called a mixed nerve or senso-motory. His dissections led him to con- clude that the-Tnotor nerves and motor roots of the spinal nerves were connected with the anterior column of the spinal cord, whilst the nerves of sensation and posterior roots of the spinal nerves were continuous with the posterior columns. He himself never experimented on the cord, but those who have 310 THE NERVOUS SYSTEM. done so, especially Longet and Van Been, were induced to con- clude that division of the anterioi' and posterior columns respec- tively, induced paralysis of motion and sensation ; and irritating them occasioned convulsion and pain. In these experiments, however, not only the anterior and posterior columns, but the middle columns and gray cornua were injured. Stilling divided the anterior column down to the gray matter, without causing paralysis of motion, and Brown Sdquard, on dividing the post- erior column only, which he did with a knife made for the purpose, found sensibility in the lower extremities, and pain, on irritation, to be increased. In either case, to cause paralysis of motion or of sensation, it was necessary to extend the incision into the grey matter. If two sections be made, however, midway between neighbouring spinal nerve roots, then conduction between the parts above and below the sections is cut oflF. (See Plate XV. fig. 12, c?.) The explanation of this is to be found in the course taken by the nerve tubes, as shewn by Lockhart Clarke, which so diverge from one another, on passing into the cord, that no one transverse section of the column can iivide them, although two at a certain distance from one an- ather may (Fig. 12, i). In the same manner, two incisions, at right angles to one another, dividing the white substance and jrey matter, completely destroy the power of transmission (Fig. 12, 6). Thus histological research and experimental investigar tion support one another, and the two have now demonstrated that the conducting nerve tubes of the spinal roots of the nerves jommunicate through the gray matter of the cord, not only with the brain and the two sides of the body, but with each other. These facts have served also to explain more fuUy the nature of those actions variously denominated automatic, reflex, and iiastaltic, for the true knowledge of which we are indebted to the labours of Marshall HaU. It is now clear that the influences 3xcited by irritation of nerves run continuously through the 3ord in certain directions, now communicating with muscles to produce spasms, and now with the glands and vessels to produce secretion and vaso-motor action, and this without any necessary 3onnection with the brain, and, therefore, without sensation. Reflex or diastaltio ac^iore*.— Numerous combined muscular ictions may go on independent of volition or sensation, and even s^hen the brain is removed. These depend on influences origin- iting in physical irritations applied to an ineide9t nerve, which REFLEX A CTIONS. 3 1 1 are conducted through the spinal cord, and from it by excident nerves to the muscles, the contractility of -which is thereby ex- cited. The character of these movements gave rise to the idea that they were connected with sensation, and indicated pain. Thus, decapitated animals may be seen to struggle exactly as they would do were the brain entire. They appear to avoid the particular injury, push the irritating instrument away with their paws, and vsrithe as if in agony ; so that it is exceedingly diflScult for a spectator to convince himself that they are not suflFering, and that such motions are not connected with sensa- tion. But we have previously seen, and the slightest analysis of our own sensations and mental operations will soon convince us, that sensation is the consciousness of an impression. If, then, the same sensitive and motor phenomena are produced inde- pendently of brain as when it is present, we must either believe that consciousness resides in the spinal marrow, and that, there- fore, they are connected with sensation, or that it resides in the brain, in which case they must be independent of sensation. The former was the notion of Whytt, Haller, Le GaUois, Pro- chjiska, and others, who connected these spinal movements with a so-called sensorium commime. Indeed, there is but one of these vfriters who reasoned correctly on this point, viz.. Sir Gil- bert Blane, who says, referring to a decapitated animal, " When the head is cut off, its irritability remains, as appears by the motion of the ears when pricked or touched by a hot wire, and as the extremities are also irritable, it will not be said that con- sciousness ajid sensation exist in two separated portions of the same body, Nor can it be admitted that sensibility and con- sciousness may remain in the head after separation ; for, if mere compression of the carotid arteries abolishes sensation and thought, by interrupting the circulation in the brain, how much more must the superior violence of decapitation have this effect." But, whilst Sir Gilbert Blane had a clear idea that these motions were independent of consciousness, he had no notion of their reflex character. On the other hand, this reflex function did occur to Prochaska, who, ■ however, connected it with a sensoriwm commune, a term used by Descartes, Haller, Whytt, and others, to express the seat of sensation, which was placed by various writers in different parts of the nervous sys- tem. It was Dr Marshall Hall who first clearly separated these functions from cerebral or mental acts, and placed them alto- 312 THE NERVOUS SYSTEM. gether in the spinal cord. He pointed out that they were inde-r pendent of mind, and, therefore, not connected with sensation. He classified them by themselves, under the name of reflex, sxcito-motory, or diastaltic actions ; described the laws by which they are governed, and their universal application to the pathology and diagnosis of disease. We have previously seen (p. 289) that all such actions require a centre with incident and sxcident nerves communicating with it, although the exact rela- tion of these, as explanatory of individual diaktaltic movements, lias not yet been determined. As examples of diastaltic, or purely spinal motions, may be snnmerated, — 1st, Those constantly going on in the eyelids when any object approaches them, as in winking, in which case the incident nerve is the palpebral branch of the fifth, and the jxcident the orbicular branch of the seventh pair of nerves.i 2d, The closwre of the larynx in every act of deglutition, and in, 3very effort to vomit, and as occurs on the contact of a drop of water or a crumb of bread, &c., when the incident nerve is the superior, and the excident the inferior laryngeal. 3d, Thev irarious movements associated in the act of respiration, in which the incident nerves are the sensitive portions of the fifth pair, 3f the pneumo-gastric and spinal nerves ; while the excident are the spinal accessory and motor branches of the intercostal iiaphragmatic, and lower spinal. 4th, The different actions issociated in the act of deglutition, including those that occur in the pharynx, oesophagus, and the cardiac orifice of the stomach. The incident nerves are united with the exfcident in the pharyngeal, oesophageal, and cardiac portions of the aneumo-gastric. 5th, Numerous actions connected with the jutlets of the body, as in defmcation and ejcpulsion from the irinary and generative organs, in which the incident and exci- ient nerves are united in the branches of the spinal nerves. 3th, The movements of the foetus in utero. 7th, Numerous com- alex actions, acquired at one period, and performed afterwards lutomatically, without exercise of mind, such as walking, sing- ing, playing certain pieces of music on various instruments, &c, ith. Instinctive actions of various animals, as the flying of migratory airds, building their nests, construction of the honey-comb, &c. )th, All the spasmodic and convulsive actions of the body, in- iluding vomiting, choking from the presence of a foreign body n the larnyx or pharynx, nervous twitching of the limbs, con- SPINAL CORD. 313 vvldons of parts of the whole body in chorea, hysteria, epilepsy, and rigid spasms of tetanus, &o. In these four last kinds of actions, the sensitive nerves of various parts of the body are the incident, and the motor the excident nerves. These diastaltic actions, though spinal and independent of mind, may, to a certain extent, be controlled by the mU. Thus the sudden contact of hot or cold bodies to the skin, the prick of a pin, &c., if unexpected, will cause starting ; but if a reso- lution be formed not to do so, this effect may be prevented. This influence is exercised over different muscles in different degrees, and it varies in persons from constitutional and un- known causes. Other spinal actions apparently require the co-operation of the mind, such as coughing, sneezing, laughing, ^ sobbing, yavming, and hiccough. In these cases it frequently happens that the most determined effort of the will fails to con- trol them ; whilst arresting or withdrawing the attention, checks them at once. Hence we have one class of motions purely voluntary, and another, partly voluntary and partly spinal, such as coughing, laughing, sneezing, &c., which it is difficult to con- ceive being produced without a certain mental effort. Then we have a class of motions altogether involuntary, wholly spinal, which may be carried on for a certain time in a decapitated animal. Pathological results. — Many cases have been published where no sensation has resulted from the application of the strongest stimuli to certain parts of the body, yet where voluntary motion in these parts has continued. Thus Mr Eeid relates a case * where the sentient power was annihilated over the whole sur- face of the body, while the power of motion, though impaired, was so entire as to enable him to use his hands in carving his food, in writing, in holding the reins when on horseback, &c. Mr Listen removed one of his metatarsal bones which was carious, the operation giving him no pain whatever. Loss of voluntary motion has also been known to take place alone without influ- encing sensibility, but this is much more rare. A few cases are known where both these lesions have occurred in one person. Thus Dr H. Ley speaks of a woman who, after delivery, had defec- tive sensibility on one side, and loss of motion on the other. She could hold her child to one breast as long as she looked at it, but on the attention being removed, the child was in danger * Edln. Med. and Surg. Journal, vol. xxxi. p 292. i 314 THE NERVOUS SYSTEM. of falling ; on this side she could not feel the application of the child's mouth to the nipple, though she could see it sucking. On the other side feeling was perfect, but she was unable to hold the child to the breast.* Dr Bright gives a similar case,f and' Andral mentions one of a man, who had the right side of his face without sensibility, and the left without motion. In the great majority of cases, both motion and sensation are affected togethei", and the former suffers most. On recovery, sensibility is restored first, and motion afterwards. It has long been a matter of observation, that dise,ase on one side of the brain causes paralysis on the opposite side of the body. This has been attributed to the decussation of the nerve tubes which may be seen in the medulla oblongata. This, how- ever, could only account for pkralysia of motion, whereas para- lysis of sensation follows the same law. The investigations of Lockhart Clarke, however, have demonstrated that, whUat the motor columns of the cord only decussate in the medulla ob- longata, decussation of the posterior columns takes place throughout the whole extent of the cord. (Plate XVI. fig. 1.) Many cases collected by Brown SSquard shew that while lesions above the medulla oblongata have a crossed action both as to motion and sensation, below that centre paralysis of sensation only is crossed, while that of motion is direct.J With the spinal cord, as with the brain lesions, such as chronic softenings have occasionally occurred to a considerable extent without paralysis ;§ but it is probable, in all such in- stances, that the whole of the white, or of the conducting tubular matter, was not destroyed. In disease of the grey central sub- stance, the power of combining or co-ordinating movements is Lost {locomotor ataxia), sometimes combined with progressive muscular atrophy. Diseases of the membranes, on the other hand, induce pain, spasm, tetanus, &c. ■ The correctness of Marshall Hall's views as to refiex actions being independent of sensation, is conclusively demonstrated by bhose cases in which the cord was so injured as to produce per- fect paralysis of the inferior extremities, so that on pricking them with a sharp-pointed instrument, or tickling the soles of the feet — the intelligence of the individual being perfect — ^the * Med. Gazette, vol. i. p. TBS. t Reports, Case 271. t Lectiire VII. in Lancet, pp. 272-3. { Case of Dessault, Abercrombie, 3d edit. p. 350. SPINAL CORD. 315 limbs are thrown into convulsions, without any pain or irrita^ tion being felt.* Naase and others also have related examples, where, in consequence of spinal disease, women have gone through the stages of labour, and had healthy children, without the slightest suffering. The same result is now brought about by means of ether or chloroforin, which suspends the cerebral functions, leaving the spinal and sympathetic ones unaffected. Brown S^quard has discovered a remarkable result of dividing one half of the spinal cord, between the seventh dorsal and third lumbar vertebrse in the guinea pig, viz., that in from three to five weeks the animal becomes epileptic. Further, that the attacks of the disease may be excited by irritating or pinching a certain space of the face and neck below the ear of the side injured. This space is about 1^ inches long tod 1 inch broad, and is anaesthetic. After a time, the hairs covering the part become crowded with pedieuli. Epilepsy has also in the same manner occasionally followed section of the sciatic nerve, f The existence of cerebral, spinal, and cerebro-spinal diseases must ever be most interesting to the physiologist, whilst the innumerable forms of spasm or convulsive disorders, all of which are reflex and essentially spinal in their character, present a wide field for study, in the prosecution of which the work of Dr Marshall HaU will be found of inestimable value. The cerebro-spinal system has also a therapeutics of its own. Cer- tain remedies, such as tea, coffee, chloral, and opium, excite or diminish the cerebral functions ; others, such as strychnine, hemlock. Calabar bean, and tobacco, excite or diminish the spinal functions ; whilst a third class act both on the brain and spinal cord, such as cold, hydrocyanic acid, and alcohol. Some ' of these remedies are also antagonistic of the other. Thus we have proved experimentally that chloral will suspend the spasms and preserve life after fatal doses of strychnine and of the Calabar bean. The elucidation of the intricate functions we have now dis- cussed is mainly due to three distinguished physiologists, whose labours constitute three distinct epochs in the discovery of the functions of the nervous system. The first of these epochs is characterised by the establishment of contractility and sensi- » See Dr Elliot's case. Lancet, 1837-8, vol. ii. p. 77. t Comptes Bendus de la Societ€ de Biologle, vol. ii, 1850, p. 205 ; and AicMt. de Phys. 1869. p. 211. THE NERVOUS SYSTEM. ty as inherent properties of the muscular and nervous ues. Such was the great discovery of Hallbr. The second ndicated by the demonstration of nerves of sensation and ves of motion, and of mixed nerves in connection with their lal roots. Such was the discovery of Charles Bell. The :d epoch is marked by the separation of numerous combined ^ons from sensation, volition, and contractile movements, demonstration that the spinal cord was their centre, and the ; that it was through a series of incident and excident .nerves t they were accomplished. Such I hold to have been the ;overy of Marshall Hall. Each of these great doctrines given rise to an astonishing amount of discussion, the whole vhich I have carefully considered, and unhesitatingly declare t, in my opini6n, there is no doubt as to the great merits of individuals named both as originators and demonstrators of important doctrines referred to. The Cerbbro-Spinal Nerves. ["here are generally enumerated, after Willis, nine cerebral rs and thirty-one spinal pairs of nerves. yi the so-cjflled cerebral nerves, with the exception of the t pair, which is in truth a ganglion, may be regarded as onging to "the cranial portion of the spinal cord. .. The first pair of nerves, called the olfactory, serve to receive 1 convey the influences excited by odours on the Schneiderian mbrane of the nose — to which it is distributed — direct to the lin, to produce the sensation of smell.' They contain grey ,tter mixed with white tubular substance, and thus histologic ly resemble the ganglia. (See Sense of Smell.) 2. The second pair, or optic nerves, receive and convey to the lin the influences excited by light, so as to produce the sen- ion of sight. In the commissure, or chiasm, the nerves of 3 two sides undergo partial decussation, the efitect of which, • jording to Mayo, is that the tubules from either optic gang- n are distributed to its own side of both eyes, and receive 3 impressions of objects on the opposite sides of the body.' 30 Sense of Sight.) 3. The third pair of nerves, or the motor nerves of the eyeball, 3 purely motor, and regulate all the movements of the eye- U,. except those which depend on the external rectus and supe- )r oblique muscles. When irritated within the cranium, spasm CEREBROSPINAL NERVES. 317 of all the muscles to which they are distributed is occasioned, and dilatation of the pupil. "When divided there are produced, 1st, External strabismus ; 2d, Paralysis of the levator palpebrce, which causes the upper eyelid to remain closed over the eye, constituting ptosis; 3d, The eye cannot be moved upwards, downwards, or inwards ; and 4th, The iris is so paralysed that the most powerful light, diieeted into the eye, is incapable of exciting the least contraction of the pupil. 4. The fourth pair of nerves, or pathetic, also- called trochlear, are purely motor, and govern the movements of the irochlearis, or superior oblique muscle of the eye. Irritation of the nerve causes spasm of that muscle, and division of it, according to Szokalski, causes slight deviation of the eye upwards and outwards, producing double vision, in which the same object appears as two, the one placed above the other. 5. The fifth pair of nerves, called trifacial or trigeminal divide into three branches, — two of which are purely sensitive, and the third is senso-motory. The sensitive branches terminate in the face, and communicate sensibility to the skin, various organs of the head, and to the external parts of the organs of special sense. It is also the great eXcitor nerve of these parts. Its communications also with the ganglia of the sympathetic system render its integrity of the greatest importance to various excito-motory, excito-sensory, and excito-nutrient actions of the head and face. The non-ganglionic Isranch distributed to the muscles of the jaws is motor, and governs the movements of mastication. Irritation or slight disease of any branch of the fifth gives rise to great pain, or neuralgia, and to that severe form of it called tic dmdovi/reux. Division or destructive disease of it causes paralysis of sensibility in the face exactly limited to a line drawn through the middle of the forehead, nose, mouth, and chin. Pricking of a pin causes no pain ; sternu- tatories placed in the nostril are not felt ; and food on the aflected side of the mouth gives no idea of its presence. On drinking from any vessel, it seems to be broken or cut away suddenly at the part where the paralysed lip is applied. In addition to these eflfects, which result from loss of sensibility connected with the ganglionic portion of the fifth, the motion of the jaw is impeded from paralysis of the motor branch. Mastication is interfered with in consequence of palsy of those muscles which subject the morsel to the action of the teeth, 3i8 THE NERVOUS SYSTEM. and from the impaired grinding motion of the jaws. The indi- vidual can only chew on the sound side, the action of the masseter and temporal muscles of the affected side being more or less imperfect or lost. There is stiU command over the features, however, and no distortion of the countenance or loss of expres- sion. The jaw is in some cases a little depressed, but this almost disappears when the individual smiles or laughs. This form of paralysis tarely exists alone, but is most commonly .associated, as in hemiplegia, with palsy of the facial also, which we shaU subsequently describe. (See seventh pair of nerves.) It may be more or less general, affecting the first, second, or third branches of the nerve, and in every case a knowledge of its anatomy and physiology will indicate the effects produced. • Magendie and Desmoulina were of opinion that all special sensibility was dependent on iutegrity of the fifth pair of nerves. Although this idea is incorrect, there can be no question that injury of this important nerve more or less interferes with, and ultimately destroys, smell, sight, hearing, and taste. This re- sults from the loss of that common sensibility which appears indispensable to the secretion of mucus from the mucous mem- branes, so that they become dry and inflamed, inducing a condi- tion incompatible with the proper performance of the functions of special sense. 1 6. The sixth pair of nerves, called abducent, are motor, and govern the motions of the external rectus muscle of the eyeball. When irritated, that muscle is convulsed, and when divided, compressed, or disorganised, it is paralysed, and the eye is turned outwards. 7. The seventh pair of nerves are composed of two parts, which are really separate nerves. The hard portion, or faoM nerve, is motor, and governs the movements of all the muscles of the face. The soft portion, or auditory nerve, transmits the influences of sound through the internal ear to the brain, to produce the sensation of hearing. (See Sense of Hearing.) The motor portion, when irritated towards its terminal branches, sometimes occasions pain, which is attributed to its anasto- mpsis with the sensitive filaments of the fifth pair. It always, tiowever, causes convtdsion or spasm. Section or destructive iisease of the nerves within the cranium, or where it emerges "rom the stylo-mastoid foramen, causes general paralysis of the nuscles of the fa.ce. The aspect of the face then differs accord» CEREBROSPINAL NERVES. 319 ing as tlie muscles are in a state of repose or activity. In the former case, all expression is lost in the paralysed part ; the two sides of the face are not symmetrical, and when viewed by themselves, apparently belong to different individuals. The features generally' are dragged toward the sound side ; the mouth is oblique, and its centre does not correspond to the axis of the body. The paralysed half of the face is a little more prominent than the sound one, which is wrinkled, contracted, and concealed behind the other, when viewed in profile. The paralysed side also appears broader than the sound one, while the eyelids are opened wide, and the eye appears more volumin- ous than its fellow. When, on the other hand, the individual speaks, laughs, cries, sneezes, or coughs, the deformity of the countenance is much increased, the mouth and features remain- ing perfectly motionless on the paralysed side, while on the other, they appear thrown into inordinate action. The muscles moving the jaws, however, which are supplied by the motor portion of the fifth, are still obedient to volition ; mastication is readily performed, and the patient can hold solid bodies between the teeth. The cheek on the affected side is flaccid, it swells at the moment of expiration, and especiaUy when the patient wishes to blow or pronounce a word with emphasis. The lips are paralysed, and the saliva and food sometimes escape from the mouth on the palsied side. The pronunciation of certain letters, as o, 6, and p, which require the intervention of the lips, is imperfect. Lastly, the patient cannot expectorate or direct the saliva to any given point at a distance from his mouth. Occasionally he can articulate with tolerable freedom, by sup- porting the paralysed cheek with his hand. Lagophthalmia, is also frequently present, exposing the eye to constant irritation, and often producing ophthalmia. This form of paJsy may be more or less general, dependent on the number of branches of Vhaporiio dwa distributed to the face, which are affected. Integrity of the facial, like that of the fifth nerve, is necessary to the proper performance of certain special senses, regulating as it does the movements of the nostrils, eyelids, and muscles of the internal ear. Great discussion has occurred as to how far the chorda tympani, which is a branch from it, is concerned in the sense of taste, a point in physiology not yet detfermined.* 8. The eighth pair of nerves are divided into three branches : * See LnssanEi and Yulpian Archives de Phys. 1869. 320 THE NERVOUS SYSTEM. 1st. The glosso-phwryngeal, distributed to the root of the tongue and pharynx, is a nerve of sensibility, administering to taste and touch in the former situation, while it is the great excitor in the act of deglutition in the latter. Irritation of it causes pain, and if injured before it gives off its pharyngeal branches, extensive musouUur movements are produced in the throat and lower part of the face. This was shewn by John Reid to depend on reflex action, the pharyngeal branches of the vagus being the excident or motor nerves. Disease or destruc- tion of the glosso-pharyngeal induces difficulty or complete paralysis of deglutition, from the loss of that power of receiving and transmitting impressions so essential for all reflex actions. 2d. The second branch is the par vag-um, or pneumo-gasinc nerve, which is distributed to numerous important parts, its branches having dififerent functions. As a whole, it is a motor and sensitive nerve, and contains incident and excident fila- ments. The pharyngeal and inferior laxyngeal branches are wholly motor ; its superior laryngeal branch is the sensitive nerve of the larynx, but is mixed with a few motor filaments which supply the crico- thyroid muscle ; the cardiac, pulmonary, oesophageal, and gastric branches are senso-motory. The re- sults of experiments have shewn that irritation of the pharyn- geal branches always produces contractions of the pharynx directly. Irritation of the miiperior laryngeal nerve causes con- traction of the crico-thyroid muscle only, whilst that of the inferior laryngeal causes forcible contraction of the laryngeal muscles, as well as of the inferior constrictor of the pharynx. In a living animal the slightest touch on the mucous membrane of the glottis will cause its instant closure, if the superior laryngeal nerve be uninjured, but if that nerve be divided on both sides, the glottis may be irritated with impunity. Injury or complete section of the recurrent nerves causes also impair- ment or loss of voice. The oesophageal branches of the vagus, if irritated, produce contractions of the (esophagus, which extend throughout the whole tube to the cardia. Their section, or that of the vagus in the neck, causes palsy of the oesophagus, in which case the tube, during eating, becomes filled with the propulsive efforts of the pharynx, and the food even finds its way into the laiynx and trachea. (Eeid.) Section and injury of the cardiac branches of the vagus do not materially influence the actions of the heart. Weber was the CEREBROSPINAL NERVES. 32t first to notice that strong stimulation of the vagus above these branches caused arrestment of the heart's contractions, with relaxation of its walls. This PflUger attributed to an inhibi- tory action, — an idea opposed by Moleschott and others. Ac- cording to Von Bezold, however, the movements of the heart appear to be influenced by three systems of nerves. One of these, seated in the heart itself, influences more especially its rhythmical action. A second, formed by the pneumo-gastrics, checks its action. The third, consisting of the sympathetic trunks in the neck and cardiac plexus, which are connected with the spinal cord, renders the organ answerable to the emo- tions of the mind. They all freely anastomose with one another, and produce compound effects, according to the amount and degree of the nervous influences affecting one or the other. Cyon and Ludwig describe a depressor nerve, arising in two roots — one from the vagus, and another from the superior laryn- gseal. Its division causes no marked result, nor does irritation of its lower cut surface. But if the upper cut surface be stimu- lated, there is a diminution in the force and frequency of the cardiac beats, while the aorta and visceral arteries are dilated ; so that it operates through the vaso-motor system of nerves. Section of one pneu mo-gastric above the puhnonary branches produces no effect on the action of the lungs. But when both nerves are divided, severe dyspnoea and asthma are occasioned. The lungs become congested and oedematous, and the bronchi filled with serous fluid. Animals never survive this operation beyond three days, if the cut ends of the nerves be separated ; but if brought in contact, they will live ten or twelve days (Eeid). Section of the gastric branches of the vagus cause, in the first instance, vomiting and loathing of food, and retard without putting an end to the digestive process. It weakens the con- tractions of the muscular coat of the stomach, which, however, are supplied from the sympathetic, but does not interfere with the secretion of the gastric juice. The vagus also forms most important connections with the sympathetic system of nerves ; and, like the fifth, is instru- mental to numerous excito-motory, excito-secretory, and excito- nutrient functions of the neck, chest, and abdomen. 3d. The third branch of the eighth pair, or spinal accessory, is a motor nerve, the external division supplying the external 322 THE NERVOUS SYSTEM. muscles of respiration — the stemo-mastoid and trapezius — and the internal division, adding inotor filaments to the vagus. On dividing it within the cranium, Eischoff observed that it caused loss of voice, and Bernard maintains that although respiration and phonation seem anatomically confounded, they are physio- logically independent. He believes the vagus acts in producing the muscular movements of the former of these functions, while the spinal accessory regulates those of the larynx and chest engaged in the latter function. 9. The ninth pair of nerves, or hypa-glossal, is the motor Qerve of the tongue. Its irritation induces spasms in the muscles it supplies, while section paralyses them. iSpinal nerves. — There are thirty-one pairs of nerves which belong to the vertebral portion of the spinal cord, all of which are senso-motory, — the posterior ganglionic root being sensory, sind the anterior motor. (See p^ 309.) These, united, form 1 compound nerve, containing sensitive and motor filaments accessary for sensation and combined motions, including inci- dent and excident filaments in connection with distinct portions or arcs of the spinal cords as centres of diastaltic movements. The use of the ganglia are not known. They do not act as centres of reflex movements, as division of the posterior roots between the cord and ganglion destroys aU such movements. The Sympathetic Nekves. This system of nerves has also been caUed ganglionic, organic, and tri-splanchnic. It consists essentially of a number of ganglia containing numerous nerve cells, communicating by one series of connecting nerve-tubes with each other, and by another series with the cerebro-spinal nerves. The structure of a ganglion is well seen, Plate XVI. fig. 3, a. The ganglia are arranged, according to their situation, into cephalic, cervical, thoracic, and abdominal ; while the connecting filaments, forming plexuses, have received numerous names in different parts, such as carotid, cardiac, diaphragmatic, supra-renal, hepatic, splenic, superior and inferior mesenteric, &c., &c; The connection between the cerebro-spinal nerves, and those of the sympathetic system is indirect through ganglia, which break the conducting power of the nerves, or modify it, — probably both. Senso-mofory properties. — Under ordinary circumstances, no act of volition or of the mmd can induce movements in parts SYMPATHETIC NERVES. 323 supplied by the sympathetic ; but under peculiar circumstances, or under the influence of unusual stimuli, movements are induced. Thus the emotions and desires, shame or fear, influ- ence the movetaent of the heart and the contractile power of the capillaries, which an effort of volition cannot do. Such results are only explicable by the coimection of the sympa- thetic system with nerves coming direct from the brain. Direct irritation of the sympathetic ganglia wiU also cause movements in the non-voluntary muscular parts receiving filaments from them. In the same way, for the most part, the internal organs and surfaces supplied by these nerves are not endowed with ordinary sensibility, and the mind is unconscious of their action ; but occasionally very severe pain is produced from their being the seat of disease, as in certain agonising pains of the heart {amgina pectoris), in the intestines {colic), in the stomach, liver, kidneys, &c., &c. Thus, although in health, the sympathetic system so diffuses the influences conducted, that they are not obedient to or excite mental acts, there is abundant proof that the cerebro-spinal filaments passing through the ganglia are constantly operating, although insensibly, in subjection to the cerebro-spinal centres. The ganglia, however, not only- diffuse the influence of impressions coming from and sent to the cerebral and spinal centres, but they are nervous centres themselves, and especially centres of numerous reflex acts in non-voluntary muscles. Excito-secretory and exdto-nutrient properties. — In addition to this excito-motory function of the sympathetic system, there is another of great importance, denominated by Dr Campbell, of the United States, exdto-secretory. ■ We have previously seen, however, that secretion in glands is only a form of nutrition ; and the influence of this system would appear not only to be exerted on glands, but on blood vessels and nutrition generally. It is, therefore, also excito-nutrient, and carried on whoUy inde- pendent of the cerebro-spinal system. Thus it has been shewn by Sir B. Brodie that division of the crural and sciatic nerves neither retarded nor impaired wounds and fractures of the in- ferior extremities ; whUe numerous experiments have proved that injury to the large sympathetic ganglia occasion the most destructive effects to the nutrition of the parts which re- ceive nerves from them. The experiments of Brown Sdquard and Harley on the supra-renal capsules, have shewn that it is 324 THE NERVOUS SYSTEM. difficult to preserve animals if the semilunar or solar ganglion be much injured in the operation ; but if this be avoided, ani- mals can live without the supra-renal capsules for a length of time. Again, as illustrative of the general influence of the sympathetic system over nutrition, is the fact that certain foetuses have been bom with well-developed textures, without a brain or spinal cord, in the same manner that many of the lower animals are destitute of these organs. As local examples of this exoito-secretory and exoito-nutrient function of the sympathetic system of nerves, may be cited, — ' 1st, The eflfusion of tears from the lachrymal gland on the appli- cation of an irritant. In this case the incident nerve is the palpebral branch of the fifth, and the excident or secretory the lachrymal branches from the carotid plexus. 2d, The secretion of saliva on irritation of the gums, or exciting the mouth by food and mastication. Here the incident nerves are the buccal branches of the fifth, and the excident or secretory the parotid branches derived from the carotid plexus. 3d, Dtotition in in- fants and children give numerous examples of excito-secretory and excito-nutrient actions. Thus, from tender gums, and irri- tation of the dental branches of the fifth, the eye may become lachrymose and congested ; the Schneiderian membrane con- gested, and its secretion increased ; while diarrhoea, is one of the most common symptoms. In these cases the excident nerves are derived from the ciliary and Meckel's ganglia, distributed to the conjunctiva and Schneiderian membranes, and through the splanchnic, with the intestines. 4th, The process of lactation exhibits the remarkable influence of excitation applied to the sensitive surface of the nipple. This, when grasped and suction made upon it by the infant, not only occasions increased flow of milk, but causes that peculiar feeling of the rush which mothers describe, and which is apparently owing to congestion of the blood vessels. Keeping up the flow of milk by constant milking long after it is required for suckling, as is constantly done for domestic purposes among our cattle, is an excellent example of the power of exciting such secretions locally. 5th, The secretion of starch from the liver, and its ready transforma- tion into sugar, is influenced by Irritations of branches of the eighth pair in the lungs, and by direct injury of the pneumo- gastric nerves, through the sympathetic branches of the coeliac and solar plexuses going to the liver. 6th, The increased quan- SYMPATHETIC NERVES. 325 tity of urine often secreted, as the result of certain nervous irri- tations,' especially in hysteiical and excitable women, and -which are only explicable as a result of reflex actions propagated through the ganglionic plexuses to the kidneys. 7th, The oc- currence of intestinal disorders must be attributed to similar causes, especially the diarrhoeas which follow exposure to cold, and the remarkable feeling of sinking and prostration to the economy which accompanies or follows colic, tormina, and other lesions of the bowels. 8th, The dissections of Dr Eobert Lee have shewn a great development of the ganglionic system of nerves in the pregnant uterus, which would seem to govern not only its own increased growth, but by its influence over the' vessels to regulate the nutritive supply of blood so necessary to the development of the foetus. 9th, The feeling of shock which follows an extensive or sudden injury, or a feeling of acute agony, seems to owe its general exhaustive efiects to the in- fluence of the ganglionic system. It was shewn by "Wilson Phillip that the brain and spinal cord might be removed entire, if the operation were carefully performed, without inducing the sudden effects of shock. But that when any part of the body was violently contused, then the surface became pale and 'Cold, the heart's action faltered, the pulse was small, and every symptom of depression was manifested. All these, and various other actions, are intimately connected with the influences of the ganglionic system of nei^ves over the blood vessels, which we have next to notice. Infiaence on animal heat. — Division of the sympathetic in the neck was observed to produce remarkable changes in the eye, especially redness of the conjunctive, contraction of the pupil, retraction of the eyeball within the eye,'&c., by Parfour du Petit in 1727, by Dupuy in 1816, by Brachet in 1837, and by John Eeid in 1838. In 1852 Bernard announced his discovery that, in addition to these phenomena, the operation caused great increase of animal heat on that side of the head on which the sympathetic had been divided ; and Brown S^quard shewed that galvanisa- tion of the sympathetic diminished the temperature, and pro- duced contraction of the arteries. The elevation of temperature commences immediately after the section of the sympathetic trunk, between the inferior and superior cervical ganglia, so that not unfrequently in a few minutes a difference in temperature amounting to 4° or 5° cen- 326 THE NERVOUS SYSTEM, tigrade exists between the two sides of the head, and is readily appreciated by the hand. In rabbits these disappear in 15 or 18 days, but in dogs they continue six weeks or two months. After extirpation of the superior cervical ganglion the effects are more rapid, intense, and lasting. In a dog operated on by Bernard, they were stUl very intense a year and a half after removal of the superior cervical ganglion. If the animal re- main in good condition, no oedematous or inflammatory action takes place. But should it fall sick or become exhausted, the nasal and ocular mucous membranes of the affected side become red and swollen, and discharge pus abundantly. These results, described by Dupuy, John Eeid, and otherSj are not necessarily caused by section of the sympathetic, but by the debility of the animal. Bernard conclusively proved that this increase of temperature did not follow section of the senSory or motor nerves. Brown S^quard shewed that, when the cephalic end of the divided sympathetic nerve is irritated by a strong inter- rupted galvanic current, the phenomena caused by its section disappear. The pupil, from being contracted, becomes larger than on the sound side ; the eye, which was sunken, projects from the orbit ; the vascular turgescence of the parts disappears, md their temperature falls below the natural standard. When the galvanic current, is stopped, the phenomena produced by the section reappear, and on its renewed application are again dispelled. These remarkable effects are attributable to section of the sympathetic nerves, causing paralysis, relaxation, and congestion of the blood vessels, whilst irritation of the nerve induces their contraction, and a diminished flow of blood. The vast importance of these facts in explaining the cause of numerous important diseases must be obvious. Thus fevers are ushered in by a feeling of cold or rigor, and followed by increase Df heat, indicating irritation, and then paralysis of the sympa- thetic system of nerves. In inflammation there is added to nere vaso-motor phenomena some lesion of the excito-nutrient lerves, causing exudation from the blood vessels. In cholera ;here is prolongation of the cold or algide state, hence the pallor md blueness of the surface, and the congestion and enormous lischarges from the gastric and mucous membranes. To these ire superadded the excito-motory actions of cramp and spasms. Sfumerous other equally important examples might be added. SPECIAL SENSES. 327 It follows that the fuuctions of the sympathetic system of nerves are — 1st, Excito-motory, thereby regulating the con- tractions of the non- voluntary muscular fibres ; 2(1, Excito- seoretory, whereby the various secretions are governed ; 3d, Eiedto-rmtrient or vaso^motor, operating more especially on the blood vessels, and thereby regulating the circulation in the capillaries, and the amount of animal heat. Special Senses. The nature of sensation has already been dwelt upon ; and it has been shewn to depend essentially on the existence of mind, or the consciousness of impressions made on the sensitive nerves. Perfumes do not exist in flowers, heat in fire, nor sound in a musical instrument. It is the efiiect produced on our minds through the senses that call such sensations into exist- ence. The impressions which result from the stimuli of odours, sapid bodies, contact of hard or irritating substances, of light and of sound, however, are different. Tor the reception of these, nerves with peculiar endowments are provided ; and to them are added a special structure or organ adapted for the purposes of smell, taste, touch, vision, and hearing. It is possible, as previously noticed (p. 286), that there may be tubules possess- ing endowments for conveying influences from other impres- sions than those just referred to, but these are not yet known. Hitherto many distinct sensations have been considered as only varieties of one sense, such as with regard to touch, those of pressure, tickling, pain, cold, warmth, smoothness, roughness, hardness, softness, &c. So with the widely different kinds of smell, taste, sounds, and ocular images. In a case of partial paralysis under my care, it was distinctly proved that the in- dividual was insensible to cold applications, while warm ones were immediately recognised ; and there are individuals in like manner who can readily detect some smells, tastes, sounds, and colours, while they cannot distinguish others. Again, the sen- sations of hunger and thirst, of 'weariness and sickness, cannot be referred to any of the five recognised senses. These facts point to the existence of additional endowments in certain nerve tubules as distinct from each other as those which are capable of transmittiog the influences produced by light or sound. 328 ' THE NERVOUS SYSTEM. Smell. The material cause of odours is the presence in the air of substances in an extremely fine state of division, or gase- ous matters, often of a very subtle description. According to Professor Graham, " odorous substances are in general such as can be readily acted on by oxygen. For example, sulphuretted hydrogen, one of the most intense of odours, is rapidly decom- posed in the air by the action of the oxygen of the atmosphere. In like manner the odorous hydro-carbons are aU oxydisable — the ethers, alcohol, and the essential oils that make aromatic perfumes. The gases that make no smell are not acted on by oxygen at ordinary temperatures. The marsh gas, carburetted hydrogen, is a remarkable case in point. This gas has no smell. As a proof of the absence of the oxydisable property. Professor Graham has obtained a quantity of the gas from the deep mines where it had lain for geological ages, and has found it actually mixed up with free oxygen, which would not have been possible if there had been the smallest tendency for the two to combine. Again, hydrogen has no smeU, if obtained in the proper circum- stances. Now this gas, although combining with oxygen at a sufficiently high temperature, does not combine at any tempera- ture endurable by human tissues. It is further determined that, unless a stream of air containing oxygen pass into the cavities of the nostrils along with the odoriferous effluvium, no smell is produced. Also, if a current of carbonic acid gas ac- companies an odour, the effect is arrested. These facts go to prove that there is a chemical action at work in smell, and that this action consists in the combination of the oxygen of the air with the odorous substance."* All animal effluvia are dense gases (except sulphuretted hy- drogen), and. are diffused slowly. In course of a little.time they will mingle with the lighter gases, according to the law of dif- fusion, but inasmuch as they thereby become diluted, the odour will best be perceived somewhere near the ground. It is on this account that the pointer and bloodhound run with the nose to the ground. The effluvia from decaying matter will be smelt in the ground floor, . scarcely perceived by the persons in the first floor, and perhaps not at all in the garrets. Hence, it is thought, the danger of lying on the ground in tropical swamps,. ♦ Bain on the Senses and the Intellect, p. 163. SMELL. 329 iile suspended on poles or from a tree in a hammock, a irson may pass the night in safety. In Naples, where the il is volcanic, and the air tainted with unpleasant smeUs, the itter class of inhabitants live in the upper stories. To cause smell, all odorous substances must be transmitted in current over the membrane on which the oKactory nerve is .mified. This, in animals who live in air, is accomplished by le respiratory movements ; and hence suspension of respira- an prevents the perception of odouii, or sense of smell, whilst peated quick inspirations, as in the act of sniffing, renders it ore intense and prolonged. On this account the sense of smell IS been considered an appendage to the function of respira- on, as that of taste is an appendage of the function of diges- on. This view is supported by the fact that the mucous irface of the nostrils, like that of the respiratory apparatus, is )vered with columnar ciliated epithelium. The acuteness of lent varies in different animals, and bears a certain relation to le size of the nostrils and turbinated bones, being greater 'here these are large and extended. Histology of tin orgom of smell. — The olfactory bulb, according 3 Lockhart Clarke,* is a remarkable ganglion, composed' of arious layers of nuclei, multipolar cells, and nerve tubules, jrminating in a ciliated epithelial surface in the centre, where liere exists a cavity or ventricle. The nerves also sent through he cribiform plate of the ethmoid bone terminate in an epithe- um of a sepia brown colour (Todd and Bowman), which covers tie deep-seated portions of the turbinated bones, and the upper liird of the septum of the nose. They consist of gelatinous erve fibres, with nuclei embedded in them, and towards their xternal extremities give off lateral fine-branched filaments efore connecting themselves with the epithelium. This con- ists of flat nucleated plates, figured by Eckar (Plate XVI. gs. 4 and 5), Clarke, and Schultze, containing finely-molecular latter, sometimes ending abruptly (Fig. 5), at others having ilia at their free surfaces (Schultze). It is necessary that the luoous surface covering the expansion of the olfactory nerves iiould be moderately moist ; for if it be too dry on the one land, or too moist on the other, the sense is impaired or lost. ?he ducts of the mucous glands, therefore, pass freely between ;he epithelial plates, and diffuse mucous over the surface. (See * Zeitsohrilt f . Wissesaft. Zoologie, bd. xi. heft. 1. 53P THE NERVOUS SYSTEM. Fig. 4. d, e.) The situation of the sensitive surface high up in the lostrUs secures it from the direct contact of air, so as to prevent •apid evaporation and dryness ; while the convolutions of the tur- Dinated bones, over which the currents of air pass before reaching ;he seat of special sense, communicate heat to them, and thus jrevent the action of cold. The peculiar structure described, nduced T6dd and Bowman to suppose that the olfactory bulbs •eceived the influence of impressions iii the same manner that a lervous centre or ganglionic plexus does, — that is, at once and it first hand, — so that the mind becomes cognisant of them mthout their being conducted by means of white substance to ;he brain. This idea, though ingeniously derived from the listologioal arrangement, is opposed to the fact that smell has ;he same connection with mind as all the other sensations. Pathology. — The sense of smeU may be exalted, perverted, or lost. It is apparently increased by education, of which the case ■A James Mitchell is an interesting example. This boy was born blind, deaf, and dumb, and chiefly depended on smell for keeping up a connection with the external world. He employed it on all occasions, like a domestic dog, in distinguishing persons ind things. In some cases, smell is exceedingly acute for parti- 3ular substances, so as to be intolerable and distracting to those svho suffer from it. Certain flowers, or particular odours, have in this way caused fainting or other bodily disorder. In other 3ases the smell is perverted or diminished, and occasionally is iost, as when the Schneiderian membrane is inflamed. Good relates the case of a lady who never possessed the faculty of smelling, a defect supposed to depend on congenital absence rf the olfactory nerve. Of this, examples, found after death, ire recorded by Cerutti, Pressat, and others. In a similar Dbservation by Bernard in a woman, it was asserted after ■ lier death, by those who knew her intimately, that she smelt perfectly well.* In recent times it has been strongly maintained that certain smells, and the emanations that give rise to them, are the cause of wide-spread and dangerous epidemic diseases. The causes of these, in truth, are very obscure, arid nothing therefore is easier than to attribute scarlatina, typhus and typhoid fevers, diphtheria, &c., to some smell inherent in the natural evacua- tions from plants and animals, or resulting from their putre- s Nerve ix. torn. ii. p. 232. SMELL. 331 faction. The following considerations, therefore, may be valuable in a sanitary point of view. I. Many places with strong odours have been proved never to produce disease. — ^This has been shewn — 1. In the perfumed plains near Cannes, Nice, &c., where flowers are largely cultivated to produce distilled fragrant essences. 2. Formerly at Mont- faucon, in Paris, and at present in the Forest of Bondy, where the sewage of Paris is manufactured into poudrette, the smell was and is intense, and has often been complained of as a nuis- ance, but at no time could it be shewn to have originated disease. 3. The Thames, in 1858, in consequence of its disgusting putrid odours, was loudly complained of, but no disease was caused by it. 4. The Craigintinny meadows, near Edinburgh, have for 200 - years been ren dered fertile by causing the drainage of the city to flow over them. The odour is often very bad, but they occasion no unhealthiness. 5. The drains in Naples run down to the sea, having large slits in them opening into the streets, and the beautiful bay is rendered foul, close to the shore, with the drain- age of the city. This, combined with the sulphuretted hydro- gen given off from the volcanic soO, renders the atmosphere so unpleasant, that the rents of the dwellings, unlike what exists in other cities, augment as the apartments ascend in the stair. The latrines in the public hospitals also exhale the most foetid ammoniacal gases. Notwithstanding, neither in the city nor the hospitals is fever, and especially typhoid fever, so common as in other cities of the same size. 6. Drs Livingstone and Kirk informed me that in Africa the smell of the mangrove swamps was often intolerable, but were never productive of ^disease. II. Atmospheric aw, productive of the most dangerous epidemics, may he quite inodorous. — This has been proved in various parts of the world, as in the marshes of Essex and Lincolnshire, the low grounds of Holland, the Campagna of Rome, the Delta of the Ganges, the swamps of Louisiana, the Guinea coast, Jamaica, and many other places. It has never been known that those who catch intermittent, remittent, or continued fevers, on visiting such localities, have connected the morbific causes with peculiar smells. It follows that — III. .There is no necessary connection between smells and dele- terious gases. — Some of these have smells, such as sulphuretted hydrogen, whilst others are inodorous, such as carbonic acid 332 THE NER VO US S YSTEM. gas. Now, it is to be observed, that -wliat makes these and other gases injurious, is their being so concentrated as to ex- clude atmospheric air, or their being pent up in confined places, from which they cannot escape. Hence why work- men going down into pits expire, for the same reason that dogs do in the Chrotto dd Cano. It has been asserted, however, that smells, though not injurious in themselves, give indications of danger. At a discussion on this subject, which took place in the Physiological Section of the British Association in September 1864, one chemist maintained that, during putre- faction, the smeU was given off first, and the noxious vapour afterwards ; whilst another declared that the smell was given off last, and was the proof that all danger had ceased. The first likened smell to the tail of the lion, which, when seen, gave evidence that the claws and teeth were not far off ; while the second, continuing the simile, declared that a sight of the tail was the best evidence that danger was departing. I do not believe that smells, as smells, are injurious to health, nor are they a nuisance to those who live among them, as the sense is most readily paralysed; yet, one of the great difficulties in making the sewerage of towns useful in agriculture, has arisen from exaggerated notions as to the danger of smells, and the necessity of deodorisation. Taste. This sense is dependent on the fifth and glossopharyngeal nerves,: — the former distributed to the two anterior thirds, and the latter to the posterior third of the tongue. The experiments of Stich and Kllaatsch* shew that the sense of taste exists over the whole surface of the posterior third of the dorsum of the tongue, "on the under surface of the tip, and in a band or line about one quarter of an inch broad, running along its edge. The sense is also well defined in the posterior parts of the hard palate, and in that portion of the soft palate which is near the bone. It is, further, present in the anterior pillars of the fauces. The middle and anterior part of the dorsum, the gums, posterior pillars of the fauces, and the inner surface of the lips, possess no sense of taste. Histology of the organ of taste. — The tongue is covered over with minute papillse, described by Todd and Bowman, which, * Arohv. f. Path. Anat, bd. x) 1858, p. 225, and bd. xviii. p. 80. TASTE. 333 ■wLen magnified, present four principal forms, viz., — 1st, Simple papillae, which are scattered over the general surface of the tongue. They are buried in the continuous sheet of the epithelium, and present the general characters of the cutaneous papillse ; 2d, Conical or filiform papUlse. These project from the surface, and are furnished with long, pointed processes, some of which approach hairs in their stiffness and structure (Plate IX fig. 8, a, h, a) ; 3d, Fungiform papillae are scattered singly over the tongue, chiefly upon its sides and tip. They vary in number, from 160 to 290. (Szabadfoldy.) They pro- ject considerably from the surface, are usually narrower at their basis than at their surface, and exhibit numerous simple papillae on their surface. (Plate IX. fig. 8,^.) They contain a com- plex capillary plexus (Fig. 9 and Plate XI. fig. 14), among which lie the tertainal loops of the nerves : and 4th, Ciroum- vaUate or calciform papillse. These are 8 or 10 in number, and are situated in a Y-shaped line at the base of the tongue. Each consists of a central flattened circular projection of the mucous membrane, surrounded by a ring of similar elevation, from whieh it is separated by a depression or fossa. The surface of both centre and surrounding ring is smooth, and covered by acaly epithelium, in which are embedded a multitude of simple papillae. A vertical section exhibits the structure represented Plate IX. fig. 7. It is supposed that the two former are more especially concerned in the sense of touch, with which the tongue is also highly endowed ; whilst the two latter, but particularly the last, constitute more especially the apparatus of taste. According to Todd and Bowman, the filiform papillae, from their isolation and partial mobility upon one another, must render the delicate touch with which they are endowed more available in directing the muscular actions of the tongue. Sapid bodies pressed against the fungiform and circumvaUate papillae give rise to impressions which, when transmitted to the brain, occasion the peculiar sensation of taste. The sense is more acute in some persons than in others ; may be intensified by educatioii, as is remarkably well observed in wine tasters ; and is diminished or lost in febrile or other disorders which alter the condition of the mucous surface of the tongue and mouth. It is intimately connected with, and modified by, the sense of smell, so that closing the nostrils diminishes and often destroys that of taste. The pungent sen- 534 THE NERVOUS SYSTEM. lations caused by mustard, pepper, &c., are owing to the jxcitation of touch, and should be separated from those of taste. Like that of smell, the sensation of taste is soon paralysed, though not so readily. On repeated sipping of a high-flavoured wine, it ceases, to be tasted, until the function be removed by jating a little cheese or other flavoured substance. There can be no doubt that the tongue furnishes us with a iroof that the same nerve which administers to ordinary sensi- jility, or the sense of touch, also communicates special sensibility, )r that of taste. What, however, is more difficult to explain, s, that while the one sense may be paralysed, the other may remain perfect. Several cases demonstrate this. Thus, a lady, )bserved by Mr Noble, had half the tongue insensible to or- linary physical agents. A knife placed in boiling water, and aid horizontally on the tongue, was only felt on the right side. The left side, when wounded by a lancet, caused no feeling of pain. The patient could distinguish on both sides with equal ielicacy bitter, sweet, and saline substances. An ingenious sxperiment gave at once the double demonstration of loss of tactile sensibility and preservation of special sensibility. The tongue having been thrust out of the mouth, a piece of salt and a, piece of sugar were allowed to fall separately on the right and left side. The shock and the contact were felt on the right side only, but when the substances began to melt, the taste was felt at once on both sides.* Vogt, Bernard, and others, have described similar facts, which support the conclusion that some other nerve must be connected with the special sense — supposed to be the Chorda Tympani. (See p. 319.) Touch. This sense is dependent on the nerves of common sensi- bility distributed to all parts of the surface. But here also we observe that a distinct structure is necessary for the mani- festation of the peculiar property. Histology cf the organ of touah. — ^This consists in the papiUsB of the true skin, which are variously modified in dififerent parts of the body, in proportion to the acuteness of the sense. In the papiUee of the fingers and a few other places, minute in- durated bodies of condensed fibrous tissue /were discovered by * Gaz. Med., 1835, p. 10-3. TOUCH. ■■ 335 Wagner, called touch bodies (Plate XVI. fig. 10), which have been supposed capable of rendering this sense more acute. They are in immediate relation to a nerve ; and the well-known effects of pressing such nerve against a hard body, as in the case of a corn, may well be supposed capable of exalting the sensibility. It was supposed by Wagner that the papillae which contain these " axiLe bodies," were different as regards vascularity from others which only contain capillary loops, such as those on the lips (Plate XI. fig. 10). But no such distinction between nerve papUlae and vascular papillae in truth exist, the two textural elements mingling together in varied proportions. The Pacinian bodies are also composed of concentric circles of fibrous tissue forming an indurated body, in the centre of which a nerve terminates (Plate XVI. figs. 8 and 9). They are most common in the mesentery, especially of the cat, and Krause supposes they are connected with the mechanism arid arrange- ment of the viscera required by that animal in the act of springing.* Though touch may be intensified, it cannot be said to be dependent on these bodies. Weber and Valentin have made numerous experiments with a view of determining the amount of tactile sensibility in the skin at different places. These consisted in touching the skin, while the eyes were closed, with the points of a pair of compasses sheathed with cork, and in ascertaining how close the points of the compasses might be brought to each other and stiU be felt as two bodies. This point was termed by Dr Graves, " the limit of confusion." The results were, that the extremity of the third finger aaid the point of the tongue are the parts most sensitive, as in these places the difference of half a line could be distinguished. Next in sensitiveness to these is the mucous surface of the lips, where the two points of the compasses can be perceived when separated to the distance of about a line and a half. On the dorsum of the tongue they require to be sepa- rated two lines. The parts inwhich the sense of touch is least acute are the neck, the middle of the back, the middle of the arm, and the middle of the thigh, where the points of the com- passes must be separated to the distance of thirty lines in order to be distinguished. Weber and Valentin have each given elaborate tables shewing these parts with others exhibit- ing the intermediate amount of tactile sensibility over the • Zeit. f. Rat. Med., bd. xvii. p. 278. 336. THE NER VO US S YSTEM. ■whole surface. Generally speaking, the trunk is more sensitive in the medium line, both before and behind, than at the sides. Some persons distinguish the points of the compasses at one- half or one-third the distance than others can. Czermak, also, has pointed out that certain individuals can recognise the points more readily if they are applied one after the other rather than applied together, although more closely approximated. When the skin is stretched, the delicacy of touch is diminished. We have already referred to the variety of feelings which may be excited by the sense of touch (p. 327), such as pressure or resistance, tickling, pain,, cold, warmth, smoothness, rough- ness, hardness, softness, &c., and pointed to the probability that this may depend upon different tubules possessing different properties. Weber* made many experiments with regard to temperature. In three cases where the skin was destroyed by a burn, heat and cold could not be distinguished over the denuded surface. According to Northnagel,t slight differences in tem- perature are most easily recognised between 80° and 91° Fahr. The eyelids, cheeks, and temples, can distinguish varia- tions amounting to not more than from 0.4° to 0.2° C. The hand and finger are about equally sensitive, but are less so than the forearm, and this again is exceeded by the upper arm, which can distinguish a difference of 0.2° C, and the same holds good of the foot, leg, and thigh. Increase of cold or heat beyond certain limits causes pain, and not a sense of temperature, and this pain is much the same whether caused by one or the other, as is often experienced in toothache. It has also been ascertained that below the skin the trunks of the nerves cannot recognise heat and cold, any more than the optic nerve, after leaving the retina, can be stimulated by light. The power we possess of referring sensations to different parts of the surface is very much the result pf education, and is obtained during infancy and childhood. Anything that inter- septs the ordinary course of events, does not at once intercept 3ur power of mentally associating the sense of touch with rarious organs. Thus pain in the stump of an amputated limb s still referred to the toes, and (why) if we cross our fingers^ uid touch rapidly in succession a round object with both, we ■eel apparently two bodies instead of one. * Mailer's Archiv. 1849, Heft. iv. s. 273-28S. t Deutsch Arehiv. f . Klin. Med., Bd. ii. p. 234. SIGHT OR VISION. 337 Touch, like the other senses, is capable of being greatly im- proved, and intensified by practice, of which the well-known power of distinguishing objects and of reading by raised letters possessed by the blind, is an example. Professor Saunderson of Cambridge, who lost his sight when two years old, could dis- tinguish by this sense genuine medals from imitation ones. Other blind men have, by their exquisite touch, been enabled to become sculptors, conchologists, botanists, &c. Sight or Vision. This sense is dependent on the optic nerve, and a very com- plex apparatus, consisting, in man, — 1st, Of external protective parts ; 2d, Of a set of muscles destined to move the organ of vision in various directions ; 3d, Of the expansion of the nerves, and the addition of a ganglionic structure, whereby the rays of light are received, and the influence of the impressions they excite conveyed to the brain ; and 4th, Of an optical apparatus, consisting of transparent media, which refract the rays of light upon the retina. The eyeball itself consists of an external fibrous coat, a middle or vascular coat, an internal or nervous coat, and of contents composed of refractive media, a minute description of which is purely anatomical. All that need be referred to here is the special functions and histological structure of the individual parts of the eye, together with a consideration of the whole organ in relation to vision. For a clear apprecia- tion of this subject, a knowledge of the physical laws connected with light is essential. (See p. 134.) 1. The external protective parts, composed of the eyebrows, the eyelids, and eyelashes, serve to shade the eye from excess of light ; to diffuse over the cornea the sebaceous matter and lac- rymal fluid, whereby the surface is kept ductile and moist ; and lastly, to prevent the access of dust floating in the atmosphere. These different actions are for the most part involuntary, and carried on partly by the cerebro-spinal, and partly by the gan-' glionic system of nerves performing excito-motory, excito-secre- tory, and excito-nutrient functions. The watery fluid secreted by the lachrymal gland, and which is difiFused over the anterior surface of the eye by the motion of the lids, keeping it moist and translucent, is conducted by two openings in the inner comer of the eye through the lachrymal duct into the nose, from whence it is discharged. THE NERVOUS SYSTEM. The eye-hall has a remarkable amount of mobility, in con- tence of sis muscles, four straight and two oblique, which ipon it in various ways. They are supplied by the third, th, and sixth pairs of motor nerves, and by a sensitive ich of the fifth pair. The object of so many nerves being fibuted to them seems to be the correction or prevention of simultaneous action which would take place in the two eyes 1 theirmuscles were supplied by branches of the same nerve. s, in turning the eyes outwards, the third nerve acts in the eye, and the sixth in the other. If the same nerves were lulated in both eyes, they would be both turned either out- ds or inwards. The action of these muscles, and its amount, be well studied by means of the opthalmotrope of Eeute ,te XXI. fig. 23). (See Practical Physiology.) The retina. — The optic nerve, on entering the eyeball, is tie compressed, but on reaching the internal surface, divides minute branches which inosculate together to form a mem- le. (See Plate XVI. fig. 6, k.) On the inside of this mem- le is placed a layer of ganglionic cells (Fig. 6, li) embedded nolecular matter, which send off processes, chiefly outwards. se two layers contain a vascular plexus of capillaries derived Q the wrterm centralis retinoe. Immediately external to the glionic layer is a fine molecular layer — the vesicular layer 5owman (Fig. 6, g), and outside this is a granular layer (Pig. ), succeeded by another molecular layer — the memhrana frnie- ta of Krause (Fig. 6,/). Outside this is a second granular ir which sometimes presents a striated appearance (Fig. 6, c) ; lastly, most external and close to the choroid membrane, is bacillary layer, or membrane of Jacob, composed of rods and 3S (Figs. 6, a, b), standing vertical to the retina, and com- ;d of a structureless transparent substance resembling glass appearance. The rods, which are external, and cones, are 1 composed of an outer and of an inner segment, which are irated from one another by a bright transverse line (Fig. 6, '), c, and C, a). The former have their thickest portion or Et directed outwards, whilst with the latter it is the reverse, ir broad bases resting on a thin membrane, called the external itary membrane. According to Kolliker, the cones contain ucleus, and are therefore elongated cells. These different srs are connected together by continuous filaments, running n the rods to the internal limitary membrane which is in SIGHT OR VISION. 339 immediate contact with the vitreous humour. (Fig. 6, A, v.) These are the fibres of MiiUer. (See Kg. 6, B and C.) The whole retina is transparent, and the rays of light pass completely through it back to the choroid membrane, and are reflected by the rods of Jacob's membrane, forwards to the sensitive branches of the optic nerve, which convey the influence of the impressions so excited to the brain, to produce the sense of vision. This appears to be demonstrated by two facts : 1st, That at the point where the optic nerve enters there are only nerve tubules, and none of the ganglionic layers or rods; and this point is insensible to light. 2d, That in the foramen of Scemmering in the axis of vision, the branches of the optic nerve and internal layers are absent, but the layer oi rods and cones exist, and here sensibility to light is most perfect The bacillary membrane would appear, therefore, to be the essential portion of the retina. For the method by which the retina may be examined in the living subject, by means of the opthalmoscope, see Practical Physiology. • '4. The optical appa/ratns consists of four lenses of different structures, densities, and curves, filling up the substance of the ball, and forming, with the strong external case or sclerotica, and the choroid, a perfectly achromatic camera obscura. Cornea. — The most anterior of these lenses is the cornea, composed of condensed epidermis resembling horn ; and hence its name. A vertical section through this structure exhibits (see Plate XVI. fig. 12), 1st, An external layer of nucleated epithelial cells forming the oonjimctiva (Fig. 13 as) ; 2d, A clear structureless firm membrane, the anterior dattic lamina (Fig. 12, b) ; 3d, A laminated structure, the edges of which resemble fibres, with fusiform spaces or lacunas communicating with each other, and attached' to the anterior elastic lamina by crossed fibres (Fig. 12, c) ; 4th, Another structureless firm transparent membrane, ilae posterior elastic lamina (Fig. 12, d) ; and lastly and most internally, a delicate lay«r, having a single layer of cells embedded in it — the membrane of Descimet. The cornea is fur- nished with a vascular zone of capillary vessels round its external margin, the larger central portion being non- vascular. Bundles of fine nerve tubules also proceed from the circumference, and form a wide-spread plexus through its substance. Aqueous humowr. — The second lens, proceeding backwards is composed of a watery fluid, or aqueous humour, principally 34° THE NERVOUS SYSTEM. ■ accumulated between the cornea and the iris. It contains io.' solution a minute quantity of chloride of sodium and extractive matter, but no structural element. Crystalline lens. — The third lens is the crystalline — one of the most remarkable bodies in nature. It is of a bi-convex form, the posterior convexity being the greater, and is enclosed by a structureless capsule, liued by a delicate epithelium, the anterior wall being four times thicker than the posterior. The substance is composed of concentric laminae, like those of an onion, united by serrated or notched surfaces, and increasing in density from the circumference to the centre. The external layer consists of transparent nucleated cells, which, after death, soon become loaded with water. (Plate XVI. fig. 7, a.) A thin section of the lens causes the edges of the laminse to appear as notched fibres, the serrated margins varying in depth in difierent animals. (Fig. 7, b, c, d.) The edges of the laminae or planes, as was described by Sir David Brewster, terminate in a stellate or triangular notch, anteriorly and posteriorly, the f o»mer having an intermediate position to the latter. The vitreous humowr. — The fourth lens, or vitreous humour, is of gelatinous consistence, fills up the large proportion of the ball, and appears to be a watery fluid inclosed within fibrous meshes of the greatest tenuity and fineness. After long steep- ing in chromic acid, Hannover shewed that in a vertical section' a number of rays proceed from the centre to the circumference, resembling an orange laid open. In the fresh eye nothing is perceptible by a structureless gelatinous, or, as some call it, mucous substance. These homy, watery, glassy, and gelatinous lenses, united, fulfil all the conditions optically required to produce achro- matism so perfectly as to set the optician's art at defiance. The choroid. — The eyeball is lined by a black opaque mem- brane, the choroid, to absorb unnecessary rays of light, placed immediately behind the vitreous humour. Posteriorly it con- sists of hexagonal pigment cells (Plate III. fig. 27, c), which become fusiform and branched anteriorly. Immediately be- hind the pigment cells is a rich plexus of capillary vessels presenting a peculiar and characteristic steUar arrangement {Tunica Ruysahiana). In connection with this membrane is the tapetum, in certain mammalia, a fine fibrous structure which strongly refracts light ; the pecten on birds and the choroid SIGHT OR VISION. 341 gland in fishes. This membrane must be important in rendering vision distinct, as in Albino's, where it is deficient, a strong light causes confusion of sight. Draper supposes that the choroid absorbs the heat or calorific ray of light, and has its temperature raised in proportion to the intensity of the colour. It is in this local disturbance of temperature, he thinks, the act of vision commences. The Iris possesses two sets of non- voluntary contractile fibres, composed of fusiform cells, with stafi'-shaped nuclei. The cir- cular are internal, and immediately surround the perforation in its centre, or the pwpil. The radiating fibres are external. , The action of the former contracts, and of the latter dilates, the pupU. The contraction of the annular fibres is under the con- trol of the third pair of nerves, while that of the radiating fibres is formed by the cervical portion of the sympathetic (Budge and Waller). The movements of the pupU must be regarded in their nature as reflex, the incident nerves being the optic, the exci- dent the third pair, having the opthalmic ganglion as their centre. Contraction of the pupil may also be induced by squints ing inwards, by strong accommodation of the eyes for near ob- jects, and by certain poisons, as opium, tobacco, and the Calabar bean. The direct action of light produces the same effect as was long ago shewn by Mr Walker, of Manchester, in persons affected by double cataract. Brown S^quard has further proved that light and an increase of 50° or 60° temperature Fahrenheit causes contraction in the pupil, when the posterior part of the eye has been cut off. It may be also seen in eyeballs cut out from a living animal, proving that such motion is not only reflex, but may result from the direct action of light. Dilata- tion of the pupil is caused by accommodation of the eye to distant objects, and by belladonna and its alkaloid atropine. The action of the pupU is most important in securing distinct vision, as the amount of light entering the eyeball is thereby regulated, superfluous rays excluded, and divergent ones cut off. Paralysis of the iris by belladonna causes dimness of sight, and optically, as is well known, too much or too little light inter-, feres with the production of a clear image. In regarding the entire eye as an organ of vision, there are various points which demand consideration. Among these are — 1. The accom/modation of the eye. — ^The means by which the 342 THE NERVOUS SYSTEM. apparatus is so readily accommodated to various distances. On this subject numerous theories have been advanced, all of which answer the purpose, if the truth of certain data be granted. \% has been supposed that the curvature of the cornea is changed (Eamsden, Home) ; but this has not been demonstrated. It has been thought that the lens is drawn forward by a contrac- tile non- voluntary muscle, — the ciliary muscle (Crampton, Bow- man), — or is pushed forwards from behind by the turgidity of the ciliary processes (Wallace, Alison). Some have thought that the contractions of the iris have much to do with the focal adaptation of the eye (Knox, Brewster) ; and others, that it is owing to the pressure on the eyeball of the external muscles which move it (Arlt). The question is now completely an- swered. Cramer * pointed out that when the light, say of a candle, is placed at a certain angle before the eye, three images are visible. The first, seen upright, reflected from the cornea, the second also upright, reflected from the anterior surface, and the third in- verted, reflected from the posterior surface of the lens. On accommodating the eye to a distant object, a considerable space exists between the first and second image (Plate XXI. fig. 24), which may be seen to be diminished when the eye is accommo- dated to near objects, by the advance of the second image to- wards the first. (Plate XXI. fig. 25.) It was clear, therefore, that the change was owing to an increased curvative in the anterior portion of the lens. Helmholtz also pointed out that the third image also underwent a very slight diminution in size, and that the posterior surface of the lens undergoes a little in- crease in convexity. The latter distinguished physiologist has constructed an instrument, the Opthalmometer (Plate XXI. fig. 24), which enables us to measure, with mathematical exactitude, the magnitude of the reflected images, their amount of deflec- tion, and the extent of the increased convexity of the lens.f The cause of accommodation is, therefore, fully demonstrated. (See Practical Physiology.) The increased convexity of the lens cannot be caused by the contractility of the iris, as in the case of Graefe,t where that membrane was wholly removed by operation, the power of accommodation remained ; it follows, therefore, that the change must be caused by the pressure occa- sioned by contraction of the ciliary muscle. • Het Accommai}a.tie, Vermogen, Physiologisch Toegelioh. Haarlem, 1863. t Physiologisohe Optik, 1868. J Archiv. f. Opthalmologie, B. vii. • SIGHT OR VISION. 343 2. The natural power of adaptation is interfered with in myopia, or short-sightedness ; in presbyopia, or long-sighted- ness ; and in amblyopia, or a peculiar dimness of vision. The first is owing to too great curvature of the lenses, and is cor- rected by concave glasses in spectacles ; the second is produced by too little curvature of the lenses, and is corrected by convex glasses in spectacles, — this condition has been called by Bonders Hypeirmetropia ; the third is owing to altered shape or oblique position of the lens, and is corrected by the use of cylindrical glass lenses. 3. Oolow-blindnegs. — Another perversion of vision consists of what is called colour-blindness, or Daltonism. Some persons cannot distinguish colours at all, everything appearing shadowed or light, like an engraving. Others cannot see brown, gray, or neutral tints ; whilst a third class confound red, blue, and yel- low with green, purple, oi;ange, and brown. Eed, blue, and yellow are never confounded with each other ; but red and green are most commonly so, — a matter of great importance to railway travellers, as at night the red light is the signal of dan- ger. This condition may be dependent on some fault in the nerves of vision, possibly in the retina, and more especially in the refractive rods ; or it may be owing to some change in the refractive media or lenses. But the theory is not yet determined. 4. Position of •objects. — All objects refracted on the retina are inverted, and yet we see them in their natural position. To explain this fact, it has been supposed that during infancy this sense, with all the others, undergoes a slow education, and that one, so corrects the aberrations of the others, that gradually we learn to recognise things as we do (MiiUer, Volkman). ' The same explanation applies to a perception of the shape, size, and distance of an object. The case of Cheselden, who operated on a young man successfully who had been bom blind, in conse- quence of congenital cataract, contains many facts in favour of this view. On the other hand, it has been urged that there is no reason why the mind should not perceive correctly, as well from an inverted as from an erect image. 5. Owe object seen from two images. — The circumstance of our seeing one object, although we receive two images in the two eyes, is explained by the regular action of the muscles of the eyeball. When this is deranged, as in squinting, or from the THE NERVOUS SYSTEM. of narcotics, we see double. Hence impressions are made the corresponding part of the retiuse in such a way that, if h eyes were united, the two portions of the membrane would ti receive half the impression. The peculiar decussation of the ic nerves seems to connect exactly these two portions so that sensation is occasioned (Mayo). Sometimes only half or a t of an object is seen ; a circumstance attributed to paralysis 1, portion of the retina, or to some disorder of the brain con- ted with the tevminations in that organ of the optic nerves. Bowman considers that the crossing of the fibres acts as ommissure between the vesicular laminae of the retinae, in same manner as the commissures act between correspond- portions of the gray matter of the cerebral hemispheres, so t, although organs are double, unity of function is the result, re, again, it has been urged that the mental interpreta- \ of the sensory impression is not to be accounted for any structural arrangements of the sensorial apparatus. I. Entrance of optic nerve insensible. — The retina, at the point ere the optic nerve enters it, is insensible. This is shewn by experiment of Marriotte. Shut the right eye, stretch out arms, and place the thumbs together. Then, on moving the ht thumb outwards, while we continue to look steadily at ' left thumb, we shall observe that the former disappears en it comes opposite the entrance of the optic nerve, and rsr )ears again when it has passed across it. The foramen of, nmerring, in the direct axis of the eye, perfectly transmits the s of light. This aperture, however, is not deficient in Jacob's mbrane — a circumstance which points out the great imports !e of that structure as a sensitive medium. '. Impressions remain a certain time. — An impression made the retina remains a certain time. This is proved by look- ; at a dazzling light or bright colour, and observing that, on •ning away the head suddenly, it continues for a longer or irter period. It is also seen by whirling a stick lighted at 1 end, which appears as a ring, the impression being continu- ) from the time the light has left one point tUl it returns to An ingenious toy, called the " wheel of life," illustrates the lie fact. i. Ocular spectra. — Some persons are subject to ocular spectra, ich are of various kinds. Fatigue of the organ causes specks moving filaments to appear, and a blow upon it, or pressure HEARING. 34S at night, indiioes a flash pf light. Remarkable objects, inani- mate or living, may be seen under circumstances preventing the possibility of their existence, which, notwithstanding, have all the aspect of reality. ' They always depend on a state of nervous exhaustion, from ill health, mental depression, or the use of certain drugs, as alcohol, opium, or other narcotic sub- stances. The capability of determining from reasoning whether such spectra are real or unreal, is a strong test of the existing soundness of mind of the individual. Various causes may induce a deception of the sense, which may be divided into sensual and mental. If the former, walking towards the object, or attempt- ing to touch it, will correct the deception. Another test exists in turning one's back to the object ; if a reality, it is of course ' lost; if it exist in the mind's eye, it is still seen. Sir D. Brewster pointed out that mental spectra follow the rotation of the eye- ball. It would be well to employ the word ■iUudon to ocular spectra dependent on disorder of the sense, and delusion as characteristic of perversion of the judgment, or of insanity. Hearing. It is necessary for hearing that certain oscillations in the air, water, or solid bodies, should reach the expanded filaments. of the auditory nerve, and that the influence of impressions so produced should be conveyed to the brain. This is accomplished through the medium of a very complicated organ or acoustic apparatus, the ear, for a description of which we must refer to works on anatomy. The most essential part of the organ is the vestibule, that exists in every class of animals in which an auditory apparatus is to be detected. There also the principal expansion of the auditory.nerve takes place, and there it is brought into connection with the vibrations of sound from the exterior. In man, such is the complication of parts superadded to the vestibule or central ear, — viz., the cochlea and semicircular canals, — that the whole is denominated the labyrinth. It consists of chambers and canals hollowed out in the solid part of the temporal bone, containing a fluid, in which various branches of the auditory nerve are ramified, and so arranged that the slightest vibration communicated to the fluid must aflfect the nerve. Histology of the organ of heoaing. — Under this head we shall I THE NERVOUS SYSTEM. fine ourselves to -what is known with regard to the distribu- i and termination of the auditory nerve iu the labyrinth. Vie vestibvle. — The vestibular branch of the auditory nerve is separate branches to the utriculus, sacculus, and ampul- d enlargements of the membranous labyrinth. -This is mounded by lymph externally {perilymph), and contains ph internally {mdolymph), and may thus be said to be sus- ded in fluid. It may easily be understood, therefore, how slightest vibrations communicated to the internal ear, in- Qce the membranous labyrinth, and immediately affect the res. Within the sacculus and utriculus is a mass of earthy ter (carbonate of lime), sometimes hard like a stone >litK}, at others, soft like powder {Otoconia), with which nerves are directly connected. Miiller mentions that jrous undulations in water are not felt by the hand itself lersed in the water,' but are perceived distinctly through medium of a rod or hard body held in the hand. It has 1 concluded, therefore, that the function of these mineral ises is to re-inforce the sonorous vibrations, and communicate ;he nerves vibratory impulses of greater intensity than the lymph alone could impart. %« cochlea. — The cochlear branch of the auditory nerve ainates, like the optic nerve, in a remarkable ganglionic cture, which is spread over the internal portion of the dbranous zone of the lamina spiralis. On looking down n the vestibular surface, we see the view represented (Plate I. fig. 12) by Ecker. Superiorly, is a thick layer of epi- ial cells (Fig. 12, 1), the membrane of Corti, below which le ligamentvm, memhranm teetorice {tectorium, a cover). (Fig. 2.) Underneath this is a membrane, the habentda sulcata tenida, a small strip of flesh) (Fig. 12, 3), with a denticu- zone to the right (6), and external to this, another mass nucleated cells {d), which fill up the space between the abrane of Corti above, and the niembrana hasilaris (m), iw. Between these membranes lie the organs of Corti {I, ; i), consisting of remarkable structures, resembling in ap- :ance internally flat staves (e), placed side by side like the 3 of a piano {inner rods of Corti). Immediately outside ;e are a row of groves or depressions (/), through which ute continuations of the nerves pass to be connected with e organs {Habenvla perforata of Kolliker). External to HEARING. 347 these are a row of flat transparent staves (middle rock of Corti), and external to these again are another row (outer rods of Corti) (jf, i). A vertical section shews that the inner rods point up- wards and outwards, so as to meet and slightly overlap the outer rods, which point in the opposite direction, like the beams of a roof. On the surface of these last, project three or more ganglionic nucleated cells, connected with them and one another by delicate jointed processes (k). Outside this compli- cated nerve apparatus, is the zona pectinata of the lamima spiralis, which terminates in the spiral ligament (Uc/amentmn spirale), a structure described by Bowman, to pass externally into a mass of non-voluntary muscular fibres, called by him the cochlear m/usde. The exact function of these parts as yet only admits of speculation, although it is impossible to doubt that the rods and terminal cells described by Corti, admit of movement on one another, and that any sonorous undulation communicated to them must cause them to vibrate, and so influence the nerves in connection with them. Further, their analogy to the baoiUary membrane of the retina, leads to the supposition, that like the latter, they are the most essential parts of the ganglionic apparatus. The lahyrinth.—hi man, sonorous vibrations reach the laby- rinth in two ways : — 1st, Through the external ear ; and 2d, Through the bones of the head. The ticking of a watch is heard as distinctly when placed between the teeth as when applied to the ear, and the note of a tiining-fork, when it can be no longer heard by the ear, again gives rise to sound when placed in contact with the teeth. It is by, the direct vibration of the bones of the head also that we become cognisant of the sound of our own voices. It has been suggested that the coch- lea is that part of the labyrinth more immediately connected with those direct vibrations ; whilst the vestibule and semi- circular canals is that portion of it which enables the nerve to receive vibrations from without, indirectly, through the air. (Weber.) The constant position of the semicircular canals led Autenreith and Kemer to suppose that they are the parts con- cerned in conveying a knowledge of the direction of sounds. Their elaborate observations on animals, however, admit of such latitude of interpretation, according to the ingenuity of the experimenter and the theory he desires to support, that little reliance can be placed upon them. Wheatstone, however, sup^ J48 THE NERVOUS SYSTEM. - Dorts the same idea, on the ground that the semicircular canals aeing placed in planes at right angles with each other, are iffected by the sound transmitted through the bones of the lead with diflFerent degrees of intensity, according to the iirection in which the sound is transmitted. Nothing certain s asoerta,ined on this point. Impressions made on the auditory nerves in the labyrinth, remain a certain time, like those made on the retina. This was ihewn by Savart, by holding a card against the edge of a rapidly rotatiug toothed wheel. He found that the removal )f one tooth did not produce any interruption in the sound. The production of musical notes — that is continuous sounds laused by repeated vibrations — demonstrates the same fact. ;See p. 130.) External ea/r. — The awride serves to collect the waves of sound md convey them through the short channel, or meatus, to the naembrane or drum of the ear {memhrana tympani), which closes it internally. Its function is well observed in man, who places iis hand behind the ear when he desires to intensify hearing, by collecting the vibrations of sound. Treviranua thought that the elevations and depressions on the surface enabled him to judge of the direction of sounds, but it is now generally believed bhat the vibrations impinged upon the external ear, are con- strained by them to follow a certain course. In the lower mimals, in whom it is largely developed, asi in solipeds, rumi- aants, and cheiroptera, the loss of the auricle often causes partial deafness, but in man it does not seem to be so necessary. I knew an officer who had the auricle removed at the battle of Waterloo by a sabre cut, but who heard ever after on the mutilated side perfectly well. In the meatus a, number of ceruminous glands pour out a waxy secretion of a bitter taste, which, with the hairs that grow from it, serve as a very sufficient protection from foreign bodies, and especially insects. Middle ear. — The memhrana tympani, or drum of the ear, is connected with -one end of a chain of small bones (called the malleus, incus, and stapes) which pass across the middle ear, or cavity of the tympanum ; the other being attached to a mem- brane which closes the oval opening into the cavity of the vesti- bule {fenestra ovalis). Another opening on the same wall, of a round shape, and communicating with the scala tympani of the cochlea, is termed the fenestra rotunda. These moveable bones SENSE OF WEIGHT, OR A MUSCULAR SENSE. 349 render the membranes tense or lax, according to the intensity of the sonorous vibrations impinged upon them. This is accomplished through the agency of minute muscles, especially the tensor tympcmi and sla/pedms muscles, which contract accor- ding to the influences transmitted by a series of excito-motory nerves, having for their centre the otic ganglion. Hence this part of the apparatus is admirably adapted to carry the nicest vibrations in such a manner as will enable them best to conduce to the production of impressions on the auditory nerve. The cavity of the tympanum or middle ear is filled with air, which passes from the pharynx through the Eustachian tube. This not only permits the free vibration of the chain of ossicles, and equalises the pressure on both sides of the membrane, but further serves to keep the air of a uniform temperature ; a circumstance of the greatest importance to the continuance of good hearing. There is much similarity between the laws which govern the reception and reflexion of sonorous vibrations and of rays of light ; and, looking at the means necessary to effect this, there is a close analogy between the ear and the eye as organs of hearing and vision. The intensity of light and of sound are both regulated by muscular parts independent of the will, operating through a ganglion and excito-motory nerves ; the ciliary resembles the cochlear muscle, and the reflecting-rods of Jacob's membrane have their analogue in the vibratory rods of Corti attached to the acoustic nerve, where it is expanded on the lamina spiralis of the cochlea. So, also, a knowledge of the function of hearing is essentially connected with an acquaintance with certain physical laws which have been previously described. (See p. 129.) Sense of weight, or a muscwlaa- sense. Much discussion has taken place as to whether a sixth sense exists, viz., a sense of weight, or a muscular sense. Two masses of matter apparently similar may be undetectable by sight or touch, taste or smell, but when balanced in the hands, are at once recognised by their difference in weight. The balance of the body itself under varied conditions, as in walking, riding, hopping, dancing, &c., indicates a peculiar sensibility in the muscles, and a corresponding sensation. " When," says Sir C. Bell, "a blind man, or a man blindfolded) stands upright. 3S0 THE NERVOUS SYSTEM. neither leaning upon or touching aught, by what means -does he maintain his erect position ? The symmetry of his body is not the cause. A statue of the finest proportion must be soldered to its pedestal, or the wind will cast it down. How is it, then, that a man sustains the perpendicular posture, or inclines in the due degree towards the wind that blows upon him ] It is obvious that he has a sense by which he knows the inclination of his body ; and that he has a ready aptitude to adjust the parts of it so as to correct any deviation from the perpendicular. What sense is this ? He touches nothing, sees nothing ; it can only be by the adjustment of the muscles that the limbs are stiffened, the body firmly balanced, and kept erect. In truth, we stand by so fine an exercise of this power, and the muscles, from habit, are directed with so much precimon, and with an effort so slight, that we do not know how we stand. But if we attempt to walk on a narrow ledge, or rest in a situa- tion where we are in danger of falling, or balance on one foot, we become subject to apprehension, and the actions of the muscles are then, as it were, magnified, and demonstrative of the degree in which they are excited."* In this particular sense, an infant gradually educates itself, as it does in all the other senses. By constant practice there is acquired from its exercise, a peculiar skill and aptitude. It admits of infinite variety, as in active and passive motions, or in adaptation to various purposes with great nicety, as in estimating weight, balancing, throwing weapons, playing on various musi- cal instruments, skilful workmanship, sense of resistance, &Cj &c. Like the other senses, it adds largely to our feeling of pleasure and intellectual enjoyment, as may be observed in tossing infants, in the constant tendency to running and active games in the young, in the field sports and gymnastic displays of adults, and in passive locomotion of various kinds by carriage, boat, hammock, &c. Its injury or Iqss produces that peculiar absence of combining motions for a purpose, while the move- ments of individual muscles remain, as in the disease now Jailed Loco-motor ataxia. Lastly, it has for its special apparatus the muscles, into the fasiculi of which, according to Kuhne, nerves enter, and are connected with, oval nuclei, which he sup- * Sir 0. Bell on the Hand, Sth edit. p. 238. See also Sir William Hamilton's Dissertations on Beid, p. 864, and Bain, The Senses and the Intellect, p. 8S. Lus- iana. Joum. de Physiologic, 1869. VOICE AND SPEECH. 351 poses to be of a ganglionic nature. (Plate XVI. fig. 11.) On the whole, this sense may, I think, now be considered as fully established. Voice and Speech. Voice is a function of the larynx, while speech is performed by the tongue, lips, and cheeks, in conjunction with the larynx. A description of this organ is purely anatomical. All that need be said is, that it is composed of a tube made up of carti- lages, which are connected together by ligaments, and moved upon one another by muscles. In the interior of the tube is a narrow chink in the shape of the letter V, having the point forwards, formed by two folds of membrane called the vocal cords, which, thrown into vibration by the air rushing from the lungs, give rise to sound. Itji thus resembles in construction the mouthpiece of a clarionet or hautboy. Different degrees of tensity are given to these cords ; and the chink, or rima, of the glottis is widened or narrowed by the various muscles of the larynx, and by the position of the cartilages. Thus the thyroid cartilage is depressed, and the cords rendered tense by contract tion of the crico-thyroid muscles ; or by the retraction of the arytenoid cartilages, which are moved backwards by the pos- terior-arico-arytenoid muscles. The cords are approximated by the arytenoid, and by the lateral crico-arytenoid, while they are separated and the aperture of the glottis enlarged by the posterior-crico-arytenoid muscles. The tension of the cords must be regulated to a great extent by the thyro-arytenoid muscles which are parallel with them throughout their entire length. Voice. — Nearly all air-breathing animals possess a voice ; in man and a few birds only can it be so modified as to be capable of producing articulation. The vocal cords are caused to vibrate by the currents of air coming from below, and at once lose this power by destruction of the inferior laryngeal nerves, which, by paralysing the muscles that regulate their necessary tensity, prevents their vibration and the production of sound. These vocal cords, therefore, are the essential parts of the organ of voice. (See Practical Physiology.) Their tensity is varied sometimes by musculai- action, and sometimes by the column of air. Thus, to produce low notes they are relaxed, and even wrinkled when at rest, but obtain the necessary degree of stretching by the pressure of the column of air. High notes 3SZ THE NERVOUS SYSTEM. on the other hand, are caused by producing great tensity of the cords, and narrowing of the glottis ; and intermediate notes, by intermediate degrees of tensity, and narrowing. The' quality as well as the compass of the voice varies in different persons. In the male the deepest is the bass, the highest the tenor, and the intermediate the baritone. The corresponding tones in the female are the contralto, the soprano, and the mezzo- soprano. (See p. 133, Plate VIII. fig. 19.) Many bass voices possess high notes, but the same high note sounded by a bass and a tenor, or by a contralto and a soprano voice, differ iu quality or tone, in the same manner that a note sounded by claironet and a flute does. It is the quality, therefore, and not its scale, which constitutes the distinction betweeSn voices, the cause of which is unknown. In men, owing to the prominence of the thyroid cartilage, the vocal cords are longer than in the female, as 3 to 2 ; and his voice in consequence is deeper, and in the musical scale an octave lower. Boys have treble voices, like women ; but as manhood approaches, the thyroid cartilage undergoes a change in its form, and while doing so the voice is cracked or broken. Afterwards it becomes manly and deep ; so that the highest soprano of a boy may be converted into the deepest bass of the man. Male voices also possess two series of notes, — chest or true notes, and false or falsetto notes. How the latter are produced is unknown. The strength of the voice does not so much depend upon the current of air as upon the strength and accuracy of the muscular movements regulating the vocal cords. Hence why practice, which gives accuracy and tone to the muscles, is of such" importance in the schools of singing. Con- sidering that the muscles which move the cords are only about three-fourths of an inch in length, and how they must adapt themselves' in producing notes, semitones, and intervals, it has been calculated that their movements can be varied with the greatest precision to the l'1200th to the l'2000th of an inch. The intonation of the human voice produces an effect on the mind wholly different from that which the mere meanmg of words excite. The speech of an accomplished orator rouses an audience to a degree of enthusiasm which those who read it in the papers next morning cannot understand. Hence great orators, as great actors, must be seen and heard to be appreci- ated. Children and animals are affected by our voices, though fUJL£, /iDIU CifJltH^n. 353 incapable of understanding our words. The same phrase may be made to present different meanings by simply varying the tone in which it is uttered.' This is why those who repeat strictly our words may calumniously falsify our sentiments. That which was spoken originally may have been innocent enough, but the manner in which it is repeated may render it significant and offensive. It is this circumstance which creates balf the calumnies circulated among society. Speech. — The voice, so modified by the additional action of the tongue, cheeks, and lips, as to signify objects, actions, and the properties of things, constitutes language. Languages vary jreatly as to the sounds which enter into them, and hence the iifficulty persons who have been educated in one, experience in learning others. Words, however, may be produced by the mouth and fauces alone, without the voice. This is whispering. Eence there may be speech without voice, as there is voice without speech. Vocal language, however, can only be ac- jomplished by the combined use of the laryngeal and oral apparatuses. Articulate sounds are divided into vowels and :on sonants. Vowels are formed in the larynx, whilst conson- mts are produced in the air-passages above it. Many of these last, however, cannot be uttered unless the elements of a vowel ire pronounced with them consonantly ; hence their name. Thus g and k are formed of the vowels e and a, modified by the Dral aperture. It is by different degrees in the opening and jontraction of the mouth and oral canal that most continuous sounds are formed ; others are sudden and momentary, cannot aesustained, and are called explosive sounds, such as 6, p, d, md g. Hence they are difficult to pronouce well in singing ; md this is why the Italian language, in which they are seldom leard, is so much better adapted to songs than English or Jerman. The office performed by the mouth in the pronunciation of rowels has been well analysed by Kratzenstein and Kemplin, vho have pointed out what the conditions necessary for chang- ng the same sound into different vowels or differences in the lize really are. For the utterance of certain vowels, both the ipening of the mouth and of the space between the tongue and lalate (oral cavity) must be large ; for the pronunciation of thers both must be contracted ; and for a third, one must be iride and the other contracted. They give five degrees of size, 3S4 THE NERVOUS SYSTEM. the dimensions of which vary by closure of the oral opening and the space between the tongue and palate as follows : — Vowel. Sound. a as in far Size of oral opening. 5 Size of oral canal. 3 a „ name 4 2 e „ theme 3 1 » go 00 „ cool 2 1 4 5 When the laryngeal and oral parts of the organ of speech cannot be combined, some letters, especially the explosive ones, as t and p, are not consonant with the vowel ; and stammering is the result. It is to be corrected by a careful study of the mode of pronouncing the various consonants, with constant practice — avoiding hurry and nervous agitation, which render all muscular action uncertain. Ventriloquism, is speaking with- out giving external evidence of utterance, and keeping the oral aperture immoveable while the attention of the audience is directed as much as possible to the thing or place from which the voice is supposed to come. The Laymgoscope. — The appearance and actions of the larynx during phonation and, respiration, can now be rendered visible by means of the laryngoscope, for a description of which, its mode of application and results, see Practical Physiology. Sleep — Dreams — Somnainhulism — Mono-ideism. Sleep is that temporary suspension of the cerebral functions which in animals alternates with their exercise for a certain time, which suspension, however, is capable of interruption on the application of stimuli to the sensory nerves. Unless this last condition could be carried out, the individual would labour under coma, syncope, or asphyxia, — states more or less allied to sleep. All action in the living economy produces waste of tis- sue ; and hence the necessity of rest in order that substance may be added. The cerebral functions, especially, are governed by this law, and we are obliged to submit to their suspension for a certain period, which is natural sleep. On awakening, we feel refreshed ; greater strength is imparted to the muscles, higher sensibility to the nerves, and greater power to the mind. Sleep is more or less profound according as the body is more or less fatigued, and according to the constitution of the indivi' SLEEP AND DREAMS. 355 dual ; as in some persons it is naturally light, -whilst in others it assumes a soporose character. Habit and temperament also exert a strong influence over sleep, some persons falling into or arousing from it at particular hours, independent of all other circumstances. Its invasion may be sudden or gradual. As a general rule, the senses and reasoning faculties sleep first, whilst, imagination and the lighter ones remain longer awake. "We may also awake suddenly ; but there is usually an intermediate condition between sleep and waking. It is in these intermediate conditions that the sleep is b'ghtest, and that persons can be ^ aroused with the greatest facility. The amount of sleep re- quired by man varies according to age, temperament, habit, and previous fatigue. In infancy and extreme old age, life is almost a continuous sleep. In adults there is no rule, some persons requiring more and some less. The average period spent by mankind in sleep is eight hours in the twenty-four, being one- third of human life. Drea/rm. — Not unfrequently while some mental faculties are suspended others are still active, and are busy with numerous ideas, which succeed each other with more or less regularity. This is dreaming. There is an absence of consciousness regard- ing external things, and a want 'of control in regulating the current of thought ; so that the principle of suggestion — that is, one thought calling up another in a certain sequence — has Tin- limited governance of the mind. In some rare cases the dream- ing thoughts are very consistent and vivid, but generally speaking they are more or less confused or incongruous. Not unfrequently, when seemingly in danger, we are governed by an intense desire to escape from it, while we possess an agonis- ing consciousness that we have not the slightest power to do so. This is incubus, or nightmare. Another curious circumstance is the rapidity with which, when dreaming, trains of thought pass through the mind, the events of years being apparently compressed into moments. The most mentally agitating dreams need not occasion the slightest change of position or muscular movement, although sometimes they produce restlessness, various gestures, or emotional indications. ■ But when the ideas of a dream govern the motions and conversation of an individual, while the memory and ottier faculties of the; mind are stiU so suspended that on awakening he is quite unaware of what has occurred, the condition is called somnambidism. !56 THE NERVOUS SYSTEM. Theory of sleep and dreams. — Many opinions have been ad- vanced as to the condition of the brain during, sleep and Jreaming, most of which assume a state of congestion to be the ;ause. If this be general and equal, sleep results ; if partial, — ;hat is, more intense in places where particular faculties of the nind may be supposed to exist, — the result is dreaming. In the rast majority of oases, all illusions and delusions, like sleep, ire the result of exhaustion, long watching, iU health, grief, intense excitement, and of narcotic drugs which depress nervous 'orce. The old are much more subject to them than the young. [n all these cases the pulse becomes quick and feeble, and 3onsidering what has previously been said as to the peculiar ;irculation within the cranium (p. 220), it will be readily under- stood how this is deranged. Some have supposed that the choroid plexuses enlarge and become erectile, so causing pressure. Others, that the vaso-motor system of nerves influence the cerebral vessels ; and that as the grey substance is most vascular, so that portion of it we have seen to be most intimately con- nected with mind (p. 284), is the one most readily affected. Somna/mhuliam. — The peculiarity of this state consists in the mind being wholly occupied with one idea or train of thought, to the exclusion of all other considerations. Thus there may be complete insensibility to bodily pain, to loud sounds, flashes of light, or other ordinary stimuli, although whatever is spoken or done in harmony with the subject thought of, is heard and appreciated, often with unusual acuteness. We can frequently change the current of the ideas by audibly suggesting others, when all the feelings and emotions in connection with the new subject are called into action, to the exclusion of those which previously existed. Thus, if the attention be strongly fixed on a distant object, impressions made on the skin will not induce sensation ; but if the attention be directed to the skin, its sensi- bility often becomes wonderfully exoitedy and pain is experienced from the contact of bodies that, under ordinary circumstances, would scarcely be felt. iThe same rule applies to all the other senses. In the same manner the reasoning power is often increased on a p&rticular point, and a variety of things per- formed, or movements gone through, that the individual other- wise could never hav;e accomplished. Some men perform aU the acts which at the time are suggested to them, or describe the various scenes which in imagination are placed before them. SOMNAMBULISM AND MONO-IDEISM. 357 In this way a somnambulist maybe made not only to think and converse on any subject, but to go through any kind of action, however ridiculous or even fatiguing. He will place himself under every variety of condition presented to his mind, and per- form the appropriate motions, as well as give utterance to the ideas, which such conditions would naturally give rise to. Thus, he may be made to hunt, swim, fight, appear intoxicated, visit distant cities or lands, &c. None of these acts and ideas, are remembered in the ordinary waking condition, although when again thrown into a similar state, they may be taken up and continued. Such a person may be said to have two kinds of memory, — one when awake, and one when dreaming ; or, as it has been called by some, a doMe consciousness. Somnambulism may come on involuntarily, at regular or irregular periods, or it may be excited artificially. In either case it may be accom- panied by various nervous phenomena, denominated catalepsy, trance, ecstaey, and so on. Mono-ideism. — Dreaming and the phenomena of somnam- bulism may be excited in some persons artificially, when the acts of the mind, sensation, and motion may be completely governed by means of suggestive ideas, even although the individual be conscious. This state has been called mono- ideism. (Braid.) The mode of effecting this is to cause a certain number of persons to fix their attention on a small object, as a coin, or submit to have monotonous passes made with the hands before their face. On an average, at least one person in twenty so treated feels in a shorter or longer time, first a mistiness of vision or stifihess in the eyelids, and occa- sionally deep-drawn sighs, hurried respiration, and signs of general excitement are visible. If now such persons are respec- tively told in a confident manner that they cannot open their eyes, it will be found that they cannot do so, especially if their attention be more strongly directed to the eyelids by touching or by pointing to them. But on receiving permission, or on being commanded to open them, this is done at once. Such persons may now, as in certain cases of somnambulism, have every kind of motion, sensation, or mental act produced, governed, or arrested, according to the endless train of sugges- tive ideas that may be communicated to the individual. Many of the lower animals also appear to be susceptible of being impressed by what strongly arrests their attention, in such a way 3S8 THE NERVOUS SYSTEM. that th^y are rendered incapaUe of voluntary motion, or irresis- tibly impelled towards the object. Hence the long glittering . bodies of serpents, or the glaring eyes of other animals, /a«cmaJe birds and. small quadrupeds, and render them an easy prey to their enemies. Similar effects are produced in individuals who look from heights and precipices, and experience an uncontrol-- lable desire to leap down, although it be to certain destruction. Like phenomena have occurred in all ages, produced-in certain persons by predominant ideas, and variously modified according to the education, politics, or religion of the period. Thus the effects produced on many votaries during their initiation into the ancient mysteries ; the ecstacies of the Pythian and other priestesses ; the influence of religious enthusiam ; the dancing epidemics of St Vitus or of Tarantism in the middle ages ; the hallucinations of the Convulsionaires at the tomb of St Medard, in Paris ; the effects of magic and of spells, &c., &c., are of the same character. Numerous perversions of the nervous functions, identical in their nature with those described, consisting of sensory Ulnsions, muscular convulsions or rigidity, and peculiar trains of thought influencing acts and conversation, may be found in the histories of witchcraft and demonology, in the legends of the saints, the journal of Mr Wesley, and in the accounts given by travellers of the religious camp-meetings in the woods of America. They are perhaps more common now than formerly, and excite even more astonishment among the ignorant ; the only difference being, that the same phenomena, which in a dark age were attributed to divinatioh or incantation, now issume the garb of science, and are ascribed to magnetism or slectricity. It is unnecessary to enter into any lengthened argument to refute the numerous hypotheses which ascribe these effects to jxternal influences. There is no series of well-ascertained facts capable of supporting such a doctrine ; whereas it would be 3asy to prove that all the phenomena really occasioned depend , Dn suggestive ideas communicated to the person affected. But (srhile these theories scarcely merit attention, the facts them- lelves are highly important, and demand the careful considera- ;ion of the physiologist and medical practitioner. The effect of nind on the body has from the earliest periods been seized upon jy individuals as a ground for veneration or astonishment. In mcient times the heathen priests were the physicians, and the MONO-IDEISM. 359 temples were converted into so many dispensaries, at which the sick applied for relief. In Catholic countries, during the middle ages, the offices of priest and physician were frequently united in one person ; so that the powerful eflFects of certain shrines, and the benefits of pilgrimages in cases not admitting of simple cure, met with every encouragement. Prom what has preceded, it must be allowed that, so far from its being improbable that real cures were so eflfeoted, all that we know of the effects of confident promises on the one hand, and belief on the other, render it very likely that many such occurred. The legends of the saints, the history of witchcraft/ the journal of Mr Wesley, the accounts of celebrated pilgrimages, and of the virtues of particular shrines, and the writings of religious enthusiasts generally, abound in wonderful cures. Charms, amulets, and relics are stated to have at once banished all kinds of agony, and removed numerous nervous diseases. Many of these are certainly incredible, whilst others are perfectly conceivable. The benefits of the royal touch are confirmed by the observa- tions of Bichard Wiseman, and the cures performed by Great- ij^ikes are warranted by Robert Boyle. In aU these cases, there can be little doubt that any benefit which did occur may be attributed to a strong belief, on the part of the patient, in the efficacy of the means employed. The facts ascertained in con- nection with this subject open up a wide field for investigation, not oidy in physiology and practical medicine, but in what relates to evidence as it is now received in courts of law. As regards the nature of this condition, it seems analogous to that of sleep or dreaming, in which certain faculties of the mind are active, and may be even stimulated into excessive action, whilst others are suspended. All the phenomena produced are strictly analogous to what medical men are acquainted with in various morbid states ; and it must now be considered as well established, that in certain conditions of the nervous system they may be induced at will. This conclusion, however, is something new, for it has but recently been received in physio- logy or pathology, that a condition of the cerebral functions may be occasioned in apparently healthy persons in which sug- gestive ideas are capable of producing those phenomena we have described, and which render them, for the time, as irresponsible as monomaniacs. Yet such is really the fact, and once admitted into physiology, must have an important influence on the theory 36o THE NERVOUS SYSTEM. and practice of medioine. Such a condition may probably be accounted for physiologically in the following manner : — We have previously seen that the white matter of cere- bral lobes contain tubes, which run in three directions, — 1st, Those which pass from below upwards, and connect the hemi- spherical ganglion with the spinal cord ; 2d, Those which pass transversely, forming the commissures, and which unite the two hemispheres ; and 3d, Those which run from before back- wards, uniting the anterior with the posterior lobes' on each side. It has also been stated that these tubes are probably subservient to that combination of the mental faculties which characterises thought. Now, all metaphysicians and physio- logists are agreed that the mind is composed of various faculties, and that different portions of the nervous mass are necessary for their manifestation. True, it is by no means determined what or how many faculties mind should be divided into ; still less is it known which parts of the brain are necessary for the manifestation of each. But let the first proposition be granted, then there is no difficulty in supposing that one or more of these may be paralysed or suspended, whilst others are entire, any more than there is in knowing that sensation may be lost whilst motion remains intact, although the nerve fibres of both run side by aide. It may be presumed, then, that certain mental faculties are, as the result of exhausted attention, temporarily paralysed or suspended, whilst others are rendered active in consequence of being' stimulated by suggestive ideas ; that the psychical stimuli of the former make no impressions on the cerebral conducting tubes, whilst those of the latter are in- creased in intensity ; that the proper balance of the mind is thereby disturbed, and thus the individual, for the time being, acts and talks as if the predominant idea was a reality. The condition is analogous so far with ordinary somnambulism, certain forms of hypochondriasis, and monomania, but admits of infinite changes, from the nature of the idea suggested. ■ According to this theory, therefore, we suppose that a psy- chical stimulus is generated, which, uncontrolled by the other mental operations acting under ordinary circumstances, indVices impressions on the peripheral extremities of the cerebral fibres, the influence of which only is conveyed outwards to the muscles moved. In the same manner, the remembrance of sensations can always be called up by the mind ; but under ordinary cir- /mnutavi/ti^ iivivj^ni^^i jiui\. 301 cumstances we know they are only remembrances, from the exercise of judgment, comparison, and other mental faculties ; but these being exhausted, in the condition under consideration, whUe the suggested idea is predominant, leave the individual a believer in its reality. In this manner we attribute to the faculties of the mind a certain power of correcting the fallacies which each is liable, to fall into, in the same way that the illusions of one sense are capable of being detected by the healthy use of the other senses. We further believe that the apparatus necessary for the former operations consists of the nerve-tubes which unite different parts of the hemispherical ganglion, whilst that necessary for the latter are the nerve-tubes connecting together the organs of sense and the ganglia at the base of the encephalon. A healthy and sound mind is characterised by the proper balance of all the mental faculties, in the same manner that a healthy body is dependent on the proper action of all the nerves. There are mental and sensorial illusions, one caused by predominant ideas, and corrected by proper reasoning ; the other caused by per- version of one sense, and corrected by the right application of the others. ' Both these conditions are intimately united, and operate on each other, inasmuch as voluntary and emotional movements and sensation are mental operations. This theory, if further elaborated, appears to be consistent with all known facts, and capable of explaining them on phy- siological principles. ABNORMAL INNERVATION. The derangements of the nervous system like those of nutri- tion, can never be understood without a knowledge of its anatomy and physiology. The general laws which regulate the morbid actions it evinces, have been referred to (p. 289). The special disorders may be classified into : — 1st, Cerebral ; 2d, Spinal ; 3d, Cerebro-spinal ; 4th, Neural ; and 5th, Neuro- spinal, according as the brain spinal cord, or nerves are affected alone, or in combination. Aberrations of intellect always de- pend on cerebral disturbance,' while preversions of motion and sensibility, if extensive, indicate spinal, and if local, neural disorder. Thus, insanity and apoplexy are cerebral ; tetanus and chorea, spinal ; epilepsy and catalepsy are cerebro-spinal ; i02 THiL, PJKKVUUii :SY^l\t.M. leuralgia and local paralysis are neural ; and all combined spasms, dependent on diastaltio or reflex actions, are neuro- spinal. The following is an enumeration of nervous disorders, Biitli the meanings that ought to be attached to them. Classification cf Diseases of Innervation. I. Cerebral Disorders, in which the cerebral lobes (or brain proper) are affected: — Insanity, or mental aberration in its various forms, in- :lude partial and general insanity. The first comprehends Monomania, or madness on one particular subject. Instinctive or Impidsive Insanity, Moral Insanity, and Hypochondriasis. The last comprehends Mania, or raving madness, Dementia or diminution, and Amentia, total loss of the mental faculties. Headache and other uneasy sensations within the cranium, juch as lightness, heaviness, vertigo, &c., &c. Apoplbxt. — Sudden loss of consciousness and of voluntary motion, commencing in the brain. The absence of consciousness necessarily involves that of sensation. The same condition as regards "nervous phenomena exists in syncope and asphyxia, but the first of these commences in the heart, and the second in the lungs. Allied to apoplexy is coma or stupor, arising from, various causes affecting the brain, such as pressure, or poisonous agents like alcohol, chloroform, opium, &c., &c. Trance, or prolonged somnolence, either with or without perversion of sensation or motion. To this state is allied ecstasy, or unconsciousness with mental excitement. Ieebgulae Motions, Spasms, &c., originating in excited or diminished voluntary power, as in certain cases of dominant ideas, somnambulism, saltatory movements, tremors, &c. ; or, on the other hand, incapability of movement from.langour, surprise, mental agitation, &c., &c. II. Spinal Disorders, in which the cranial and vertebral por- tions of the spinal cord are affected : — Spinal Irritation. — Pain in the spinal column, induced or increased' by pressure or percussion, often associated' with a variety of neuralgic, convulsive, spasmodic, or paralytic dis- orders affecting in different cases all the organs and viscera of the body, and so giving rise to an endless number of morbid states. L.l^JH.Hll'lUATlUlN Ut IV£.KyUU^ DliiUKVKK^i. -303 Tetanus. — ^Tonio contraction of the voluntary muscles. Trismus, if confined to the. muscles of the jaw ; Opisthotonos, if affecting the muscles of the back, so as to draw the body back- wards ; Em/prosthotonos, if affecting the muscles of the neck and abdomen, so as to draw the body forwards ; and Plewosthotonos, if affecting the muscles of the body laterally, so as to draw the body sideways. Chorea. — Irregular action of the voluntary muscles, when stimulated by the will. Hysteria. — Any kind of perverted nervous function, con- nected with uterine derangement. Nothing can be more vague than this term. Hydrophobia. — Spasms of the muscles of the phamyx and chest, with difficulty in drinking and dread of fluids. Spasms and Convulsions. — Tonic and clonic contractions of the muscles of every kind and degree, not included in the above, originating in the cord. (Centric Spinal Diseases — Marshall Hall.) Hemiplegia. — Paralysis of a lateral half of the body, gene- rally dependent on disorders of the cranial portion of the spinal cord above the decussation in the medulla oblongata. Paraplegia. — Paralysis on both sides of the body, generally the lower half, in consequence of disorder of the vertebral por- tion of the spinal cord, below the decussation in the medulla oblongata. III. Cerehro-Spinal disorders, in which both cerebral lobes and spinal cord are affected : — Epilepsy. — Loss of consciousness with spasms or convulsions occurring in paroxysms. Apoplexy v/itA conmdsion or paralysis is also cerebro-spiaal. Catalepsy. — Loss of consciousness with peculiar rigidity of muscles, so that when the body or a limb is placed in any position it becomes fixed. Eclampsia. — Tonic spasms with loss of consciousness in infants. The acute epilepsy of some writers. IV. — NcMral disorders, in which the nerves are affected during their course or at their extremities : — Neuralgia. — Pain in the course of a nerve, although in fact all kind of pain whatever is owing to irritation of the nerves. i&4 rtiE NEKVUua :iYi>riLM. Thus the sympathetic system of nerves and its ganglia, though jrdinarily giving, rise to no sensation, may occasionally do so, IS in cmgina pectoris, colic, irritable testicle and uterus, and in jther agonizing sensations, referred to various organs. iRRITATIOlf OF THE NeRVBS OF SPECIAL SbKSE. — Of the Optic, jausing flashes of light, ocular spectra, rmbscce volitantes, &c. ; of the auditory, causing tinnitus aurium ; of the olfactory, causing unusual sensitiveness to odour; and of the gristatory, causing oerverted tastes in the month. Itching, formication, and other sensations referable to the peripheral nerves, also belong to this jlass. Irritation of Special Nerves of Motion, as in local spasms of one'or more muscles, or of the hollow viscera. • Local Paralysis. — Loss of motion or sensibility in a limited part of the body, or confined to a special sense, as in lead palsy, or in amaurosis, eophosis, anosmia, ageibstia, cmcestKesia,, and loco- motor ataaria. V. Neuro-spinal disorders, in which both the nerves and spinal cord are affected : — Diastaltic or Reflex Actions. — To this class belong all those diseases depending on irritation of the extremity of a sensitive nerve, acting through the cord and motor nerves on the muscular system, and producing a variety of spasmodic dis- orders, local or general, far too numerous to mention — which can only be understood by a thorough knowledge of the physi- ology of the diastaltic or excito-motory system of nerves. All these disorders may be the result of structural disease of the nervous system, or of what is called funcpional derangement, understanding by this a disease which, even when it causes death, leaves no trace of altered structure detectable with the aid of the microscope. Thus, tetanic rigidity may depend on a spinal arachnitis, as well as on the irritation from a wound or poisoning by strychnine ; and delirium and coma may be caused by cerebral meningitis, as well as by moral insanity, starvation, or poisoning by chloroform or opium. Whether in these cases there be in fact only one cause common to the whole, it is difficult to say ; certainly it cannot be demonstrated. It might be contended that in every instance there is a certain amount of congestion producing unaccustomed pressure, or that a peculiar state of nutrition of the part is momentarily produced here or there in the nervous mass. But as neither theory appears to us applicable to aU cases, we shall consider the patJiological causes of nervous disorders as of four kinds, — 1st, Congestive ; 2d, Structural ; 3d, Diastaltic ; 4th, Toxic. 1. Congestive derangements of the nervous system. — The peculiar nature of the circulation within the cranium and vertebral canal has been previously pointed out (p. 220), and we have seen that, although well defended under ordinary circumstances against any mischievous change, still, when such change does occur, it operates in a peculiar manner. In other words, so long as the bones are capable of resisting atmospheric pressure, although the amount of fluid within these cavities cannot change as a whole, yet the distribution of that amount may vary infinitely. Thus, by its being accumulated sometimes in the arteries, at other times in the veins, or now in one place and then in another, unaccustomed pressure may be exercised on diflferent parts of the nervous centres. This, according to its amount, may either irritate or suspend the functions of the parts ; a fact proved by direct experiment, as well as by in- numerable instances where depression of bone has caused nervous phenomena which have disappeared on removal of the exciting cause. That congestion does frequently occur in the brain and spinal cord there can be no doubt, although it cannot always be demonstrated after death. The tonic contraction of the arteries is alone sufficient to empty them of their contents, and turgidity of the veins may or may not remain according to the symptoms immediately preceding death, and the position in which the body is placed. But it is, observable that those causes which excite or diminish the action of the heart and general powers of the body are at the same time those which induce nervous disturbance, as well as occasion a change of circulation in the cerebro-spinal centres — such as the emotiops and passions, plethora and aneemia, unaccustomed stimuli, uterine derangement, &c. It is only by this theory that we can understand how such various results occasionally occur from apparently the same cause, and a^ain how what appear to be different causes produce similar effects. Thus, violent anger, or an unaccustomed stimulus may, in a healthy person, induce a flushed countenance. 1 niL ivju.ni'uuo o it jiiliyi. increased action of the heart, a bounding pulse, and sudden loss of consciousness. Again, fear or exhaustion may occasion a pallid face, depressed or scarcely perceptible heart action, feeble pulse, and also loss of consciousness. In the first case, or coma, there is an aiocumulation of blood in the arteries and arterial capOaries, and a corresponding compression of the veins ; in the second case, or syncope, there is distension of the veins and venous capillaries, with proportionate diminution of the calibre of the arteries. In either case, owing to the peculiarity of the circulation within the cranium, pressure is exerted on the brain. Hence syncope differs from coma only in the extreme feebleness of the heart's action, — ^the cause, producing loss of consciousness,' sensation, and voluntary motion, being the same in both. Indeed, it is sometimes difficult to distinguish these states from each other ; and that they have frequently been confounded, does not admit of doubt. In the same manner, partial congestion from either cause may occur in one hemisphere, or part of a hemisphere, in the brain, or in any particular portion- or segment of the spinal cord. The pressure so occasioned may, irritate and excite function, or may paralyse or suspend it ; nay, it may so operate as to suspend the function of one part of the nervous system, while it exalts that 'of another. Thus all the phenomena of epilepsy are eminently congestive, the individual frequently enjoying the most perfect health in the intervals of the attack, although the effects are for the time terrible, causing such pressure that, while the cerebral functions are for the time annihilated, the spinal ones are violently excited. In the same manner are explained all the varied phenomena of hysteria and spinal irri- tation, for inasmuch as the spinal cord furnishes, directly or indirectly, nerves to every organ of the body, so congestion of this or that portion of it may increase, pervert, or diminish the functions of the nerves it gives off, and the organs which they supply. Congestion, therefore, we conceive to be the chief cause of functional nervous disorders originating in the great cerebro-spinal centre. 2. Structwal derangements of the nervous system. — The various parts of the nervous system, being furnished with blood vessels, are subject to most of the diseases of nutrition. The brain and' spinal cord are especially liable to those lesions which produce effusion, extravasation, exudation, morbid growths, and de- generations of texture. The effects these occasion are identically the same in kind as those caused by simple pressure, or from the other circumstances to be referred to. In their mode of onset, however, they exhibit a difference. Thus, as a general rule, hemorrhage is indicated by suddenness of attack ; acute exudations, by local pain, with fever ; chronic exudations and tumours, by gradual perversion of the mental, sensitive, and motor functions in various ways and degrees, according to the part affected. Intelligence suffers in proportion to the extent and nearness of the disease to the hemispherical ganglion, and motion according as the cerebral and vertebral portions of the spinal cord are influenced. Occasionally, after more or less im- pairment of intellect, sudden paralysis appears ; a result attri- butable to the rupture or deliquescence of tubes which have been already softened, but not sufficiently so to interrupt their power as conductors of the nervous force. Instances, indeed, have beeii recorded where complete destruction of one half of the brain, or of the whole thickness of the spinal cord is said to have occurred, in which no paralysis or other symptom has been caused ; but it is certain that numerous tubes in such cases were intact during life, and capable of transmitting impres- 3. Diastaltic or reflex derangements of the nervous system. — We have previously seen (p. 289) that recent researches render it pro- bable that the actions hitherto denominated re/lex are in fact direct ; only that the impression which is conveyed commences in the circumference of the body, instead of in the nervous centires. There is every reason to believe that such impressions pass through the cord by means of conducting nerve fibres, which cross from one side of that organ to the other, and that histology will yet demonstrate that all these apparently con- fused actions are dependent on the existence of certain uniform conducting media. Indeed, already we can judge with tolerable exactitude from the effects, what are the particular nerves and segments of the cord which are influenced during a variety of actions ; and notwithstanding the immense difficulties of the inquiry, we have every hope that the period is not distant when the diagnosis of many more reflex acts will also be ren- dered certain. The principle involved in all these acts is, that 36S THE NERVOUS SYSTEM. the irritation which produces them' is to be sought for in the nervous extremities rather than in lesions of the centres ; and the great importance of this principle in pathology and in prac- tice cannot be too highly estimated, although, for the numerous details which Ulustrate it, we must refer to a previous part of this book (p. 312), and especially to the works of Dr Marshall Hall. "We would point to traumatic tetanus, and to the convul- sions resulting from teething and gastric derangements in children, as good examples of diastaltic functional disorders. Numerous symptom's which accompany organic changes belong to the same category. In other words, the structural lesion constitutes the irritant, or cause, while the effect is functional. 4. Toxia derangements of the nervous system. — The influence exercised by certain drugs is of a kind which causes a close resemblance to various diseases of the nervous system. These influences, if carried to excess, are toxic, and dangerous to life ; if employed moderately, and with caution, they constitute the basis qf our therapeutic knowledge in a vast vai-iety of diseases. Why one drug should possess one power, and another a different one, — or why some should influence the brain, and others the spinal cord or nerves, — we are ignorant. ^ Such facts are as much ultimate facts in therapeutics as are the separate endowments rf contractility and sensibility in physiology. As pathological !auses of functional disorders of the nervous system, their Dower is undoubted. By their means the five classes of lervous disorders may be occasioned in different ways, pro- lucing altogether distinct and peculiar effects. Thus — Toscic cerebral derangements are occasioned by opiimi and most )f the pure narcotics, which first excite and then depress or lestroy the mental faculties. According to Mourens, opium Lcts on the cerebral lobes, while belladonna operates on the orpora guadrigemina. The first causes contraction, and the ast dilatation of the pupils. Tea and coffee are pure exciters of he cerebral functions, and cause sleeplessness. Alcoholic drinks, ither, chloroform, and similar stimulants, first excite and then luspend the mental faculties, like opium. The modern practice if depriving persons of consciousness, in order for a time to [estroy sensation, has been very much misunderstood in conse- [uence of such remedies having been erroneously and un- cientifically denominated anaesthetics. The fact is, they in no CAUSES OF NERVOUS DISORDERS. 371 way influence local sensibility, or the sense of touch. Their action is altogether cerebral ; and hence the danger which has frequently attended their action. Toxic spinal derangements. — Strychnine acts especially as an excitor of the motor filaments of the spinal cord, causing tonic contractions of the muscles, as in tetanus from spinal arachnitis, or from the diastaltic action of a wound. Woorara produces exactly an opposite effect, causing paralysis and flaccidity of the same parts. Coniwm paralyses the motor and sensitive spinal nerves, producing paraplegia, commencing at the feet, and creeping upwards.* Picrotoxine, according to Dr Mortimer Glover, causes the animal to stagger backwards, as in the ex- periments of Magendie or the crwa cerAeUi. Toxic cerebrospinal dercmgements. — Of these, the poisonous effects of hydrocyanic add offer a good example. All the animals we have seen killed by this agent utter a scream, Ipse their consciousness, and are convulsed. These are the symptoms of epilepsy. Cold is at first an excitor of the spinal functions, and is a strong stimulant to diastaltic activity, but if long continued, produces drowsiness and stupor. Toxic nev/ral and newo-spinal derangements are especially occasioned by the action of certain metallic poisons, such as mercwry, which occasions irregular muscular action, with weak- ness ; and lead, which causes numbness and palsy, most common in the hands. On the other hand, caniharides stimulates the contractions of the neck of the urinary bladder and secaie Comutum those of the pregnant uterus. Stramonium acts as a sedative to the nerves of the bronchi ; while aconite operates powerfully in paralysing the action of the heart. * See the author's case, in which the symptoms resembled those caused in Socrates as described by Plato. Ed. Med. and Surg. Journal^ 1845, and Clinical Medicine, 6th edit. p. 469. 372 REPRODUCTION. REPRODUCTION. The process whereby the countless variety of organisms which constitute the vegetable and animal worlds is perpetuated on the surface of the globe has from the earliest periods attracted the attention of physiologists, naturalists, and philosophers. In recent times, the excellence of the achromatic microscope bas enabled us to penetrate much further into the mysteries involved in reproduction, and the whole subject is now one of vast extent. We shall speak of this function as consisting of three kinds, viz. : first, Homogenesis ; second, Parthenogenesis ; and third, Heterogenesis. HOMOGENESIS. By Homogenesis {o/iBiss, like ; ysrins, generation) is to be under- stood the production of offspring resembling in form that of their parents. This mode of reproduction is the only one found in man and the higher animals. The process may be divided into three stages: first, the production and discharge of germs; second, the fecundation of these germs ; and third, the changes which follow fecundation. ThK PEODUCTIOiT AND DiSCHAE&E OP GbEMS. We have seen that at the earliest period of development in all organised beings, without exception, there is formed a mole- cular blastema which originates a nucleated cell (pp. 45 to 49). Up to the point where sexes are manifest, the process of repro- duction is identically the same with that of cell growth. The peculiarity of the function of generation in the higher organisms consists in the superaddition to this process of a particular act, whereby the further development of germ-cells is occasioned. There is a special apparatus in animals and in plants — the ovary, — ^the function of which is to mature a germ, that from the time of its first formation is capable of becoming the rudi- ment or embryo of a new being, and which is often separated from its parent in a form altogether dissimilar to that which it is ultimately to assume; This sometimes takes place as a spore, at others as an egg ; and hence the terms spondiferous and PRODUCTION AND DISCHARGE OF GERMS. 373 ovvpa/rous, as distinguished from wmpa/roui reproduction. The more heterogeneous a structure becomes, — that is, the more difference is manifested in the structure and properties of its separate parts, — the less title has any one to be regarded as a separate individual, since it cannot maintain an independent existence, nor reproduce the entire structure. When an organism merely consists of a multiplication of similar parts, these parts may separate, and constitute independent existences, as in the Algae among plants, and in the Protozoa and Coelenterata among animals. When it divides into a number of parts this has been called fisdparcms generation — a mode of reproduction that never takes place in the more highly organised beings. In other cases, a bud is formed on the parent which may ultimately separate as an independent being. This is termed reproduction by getrvmation. These modes of propagation are identical -with that of multiplication by cells alone, vfith this difference, that at one period groups of cells are aggregated and united together, and afterwards separate. Germ-cells are constantly forming and ripening in the ovaries of plants and animals, and are separated from them at particular times. In the separation of these cells, indeed, a tendency to periodicity is manifested. Thus, plants flower at certain seasons — some in spring, others in summer, and a third class in autumn or winter — with great regularity. Throughout the whole range of animals the same thing is observable. They all present a breeding period, at which time alone ova are f uUy developed, and capable of being fecundated. Phenomena attending the separation of germ-cdls in plants and animals. — The reproductive organs of plants and animals at this time become devoted in temperatwe. Among plants, this is most appreciable in the Arum tribe (Aracese), where male and female flowers are collected in great numbers on a thick spadix or stalk, and are enclosed in a sheathing bract termed a spathe. On one occasion, Brogniart observed that in the Colocasia odora the temperature was 8° above that of the surrounding air. This was increased in the following day to 18°, and, during the emission of pollen, on the three succeeding days to 20°, after which it began to diminish with the fading of the flower.* In animals, the same elevation of temperature has caiised agri- culturists to denominate this season the period of heat. It * "Balfour's Clasa-Book of Botany." 1871. Pp. 619-626. 374 THE PRODUCTION AND originates in them from excessive congestion in the capillarie of the part, causing great local and more or less general dis turbance of the system, the result of an augmented nutritioj in the ovaries necessary for the complete development of the ova This congestion causes rupture of the vessels and discharge o blood, which in the human female, and in a few of the monke; tribes, causes an external flow, known as the menstrual f/uM whUe the process in them has received the name oimenstrimiion Menstruation. — This term is applied to the periodical discharg from the female generative organs of a bloody fluid. It occur in most women once every four weeks, or once every luna: month, hence the term menses. It usually appears at a fixe( date, and continues from three to seven days. There is thai an interval of about three weeks until it again appears. Thi discharge is often accompanied by general symptoms, such ai debility, weariness, pain in the back and limbs. It rareli occurs in pregnant women or during lactation. The quantity of fluid varies in difl^erent individuals and at different ages. Thi essential part of this function, however, is not the dischargi of a fluid externally, but the ripening and separation of ova f ron the ovaries. Multitudes of seeds and of ova are formed in thii rnanner, at regular periods, in plants and animals, which prov( abortive, and the history of which is identical with the forma tion, ripening, and disintegration of simple nucleated cells, whicl have no power of reproduction. Microscopic Characters of Menstrual Fluid. — It consisb chiefly of mucus which is coagulated by acetic acid, formin| molecular fibres. There are also blood corpuscles, and epithelia cells derived from the mucous membrane of the uterus. Il cannot be distinguished from blood discharged from any othei mucous surface, and the anjount of mucus usually prevents il from spontaneously coagulating. Structure of the Ovaries. — These organs, two in number, ii the human female, are situated at the back of the broad Ugameni of the utenis. They measure, in the unimpregnated condition one and a half inches in length, three quarters of an inch ii breadth, and nearly haK an inch in thickness. They consisi essentially of a fibrous stroma (Plate XVII. fig. 4) or network richly supplied with blood-vessels, enclosed in a tough capsul< composed of white and yellow fibrous tissue (tunica albuginea) In the meshes of the stroma there are developed certain ceUi DISCHARGE OF GERMS. 375 termed Graafian vesicles, from De Graaf ■who first described them.* These appear first, axicordiug to Schrbnf Mid Grohe,J near the surface in the ovary of the cat (Plate XVII. fig. 4), and may be seen in great numbers in the ovary of even a uewly- bom female child. As they increase in size, they pass deeper into the substance of the ovary (Plate XVII^ fig. 4), and undergo development, as a result of which ova are formed in their interior. In the ovary of a female at puberty, or during the child-bearing period, Graafian vesicles in all stages of development may be seen (Plate XVII. fig. 4). When the. ovum is fully developed, and ready for extrusion, the cavity of the Graafian vesicle enlarges, by the secretion of fluid in its interior, pushes aside the part of the stroma between it and the surface, and projects from it externally. Structure of the Oraajicm Vesicle and Ovum. — The manner in which ova are formed in the ovary has been well studied by Martin Barry, who informs us that molecules and granules are deposited in groups among the fibrous stroma of the organ (Plate XVII. fig. 4, a, and fig. 5). Around a large granule smaller ones are aggregated, and become surrounded by a mem- brane — the ovisac — so as to form a nucleated cell containing granular matter (Figs. 5, 6, and 7, a, b). This granular matter now separates into two portions. The inner forms a membrane that immediately surrounds the yolk, and from its transparent appearance has been called the zona pellucida (Fig. 4). The outer divides into two layers, one of which, covering the zona pMudda, he called the tunica granulosq, (Fig. 4, c) ; and the other, which lines the ovisac, the membrana granulosa (Fig. 4, 6). These two membranes are united together by four or more bands — the retinacula — having transparent fluid between them. In the fully formed Graafian vesicle, several of the retinacula dis- appear, while those remaining become shortened and enlarge so as to form a disk-shaped mass of granules, termed by Von Baer the proligerous disk. (See Plate XVII. fig. 4, lower Graafian vesicle.) The whole structure now forms a vesicle, — the Graafian vesicle, — and consists externally of a fibrous or vascular mem- brane, and another inner one — the ovisac of Barry — having sus- pended from it, by the retinacula, the ovum composed of zona * De Graaf, De mulierum orgauls generation! inservientibus, 1672. + SchTon, Zeitschrift f. Wissensch Zoologie, vol. xii. p. 409. J GrShe, Virchow's Archives, vol. xxvi. p. 271; xxix. p. 450. 376 • THE PRODUCTION AND pdluaida, yolk (Fig. 4, d), and germinal vesicle (Fig. 4, e). la the interior of the germinal vesicle there is a smaller body termed the germinal spot (Fig. 4, /). So that at this period the ovum resembles a nucleated cell haTuig also a nucleolus. Graafian vesicles, though they may be seen before puberty in the ovary, after that period increase in number and in size, and may be observed in all stages of development scattered through the sub- stance of the organ, those most advanced being near the surface. Towards the end of each menstrual period, such as are ripe burst, from the quantity of sanguinolent serum or blood which is poured into them from the external vascular membrane, and the ovum escapes from the surface into the fimbriated extremity of the Fallopian tube, which grasps the ovary by a reflex action in order to receive it, and through which it is conveyed to the uterus. The Fallopian tube is lined by ciliated epithelium, and the play of the cilia is directed towards the uterus — in the right Fallopian tube downwards from right to left, and in the left one downwards from left to right. The ovum, however, is con- veyed to the uterus, principally .by the peristaltic contractions of the muscular coat of the tube. Corpora Lutea. — The cavity thus left in the ovary is most frequently filled with coagulated blood, the result of haemorrhage from the vascular or external layer of the Graafian vesicle, which participates in the congestion occurring in all the pelvic organs during the menstrual period. This coagulum of blood becomes gradually absorbed, in the course of which it changes its colour, and assumes a yellow and puckered appearance. The cells of the membrane granulosa multiply and grow inwards upon the clot, and assist materially in filling up the cavity.* In this state it has been called corpus lutewm (the yellow body), (Plate XVII. fig. 9, in which one large recent corpus lutewm is seen in the centre of the figure, an older one on the right hand, and one stiU older on the left.) And it has been supposed to present such peculiar appearances when fecundation has occurred a,s to warrant medical men in asserting that pregnancy had taken place — a grave error, which modem science has completely exploded. These appearances are described as being, — \st, An irregular form in the false, but a regular one in the true corpus luteum; 2d, An absence of a central cavity lined by a mem- brane in the false, whilst in the true there are both; 3d, * Schron and GrShe, id. DIULHAKUK UJ' (JKRMS. 377 Absence of concentric radii in the false, -while in the true they are present; 4jLLUJ>iu/LJ.iuJN un ui^km:^. 379 From this moment that series of changes commences in the ovum whereby an embryo is formed. For this purpose, how- ever, various circumstances are necessary, especially a fitting locality, proper temperature, moisture, &c. Seeds which have been impregnated retain the power of growth, or what some call dormant vitality, for many years ; and when at length placed in favourable circumstances, they develop themselves. Generally speaking, instinct guides the lower tribes of animals to deposit their eggs in appropriate localities ; and the extra- ordinary variety of such positions selected by insects, fishes, and reptiles, has furnished a curious subject of observation for the naturalist. In most birds, the fecundated ova are hatched by the mother, who elevates them to a proper temperature by the heat of her own body. In mammiferous animals, fecundated ova are retained in an organ — the uterus — which is provided for their reception, where they grow and become developed ; and when at length they are capable of supporting an independent existence, they are excreted or parted from the body of the parent by the process of parturition. Structure of the testes. — These organs are of an oval form, and consist of a body (Plate XVII. fig. 1, a, i, b,) and an elongated structure placed behind it called the epididymis (Fig. 1, d, e, g). The upper extremity of the epididymis is known as the gloUis major (Fig. 1, d), while the lower is the globus minor (Fig. 1, g). The gland has a tough fibrous tunic, the tunica albuginea (Fig. 1, i), which is projected- in- wards so as to form a prominence called the corpus Highmo- rianum, or mediastinum testis (Fig. 1, c,f). Numerous bands of connective tissue pass from the corpus Highmorianvm to the capsule of the gland, thus dividing it into a number of com- partments, in which lie the essential structure of the testicle, the tvhuli seminiferi. These tubuli, originating by blind ex- tremities at the surface of the gland, are at first much convoluted, but after passing inwards become straight, forming the vasa recta (Fig. 1, b, s). The vasa recta unite with each other in the substance of the corpus Highmorianum, and thus form a plexus called the rete testis (Fig. 1, c). A number of ducts, the vasa efferentia (Fig. 1, d), pass from the rete testis, and become convoluted, forming a series of cones, the apices of which are directed towards the rete testis. These cones are called the cord vasculosi (Fig. 1, d), and they constitute the chief portion of the 38o FECUND A TION OF GERMS. globus major of the epididymis. The epididymis is formed by the windings of a duct or ducts derived from the coni vasculosi, and at length the duct issues from the vicinity of the globtts minor, under the name of ■sow deferens (Fig. 1, g, h). This duct passes behind the bladder, uniting with the duct of the vesicvloe eeminaZes. These vesiculse are receptacles for the storing up of semen, where it is probably mixed with mucus. The duct formed by the confluence of the vas d^erens with the duct of the vesiculce seminales is called the com/mon ^aculatory diict, and opens into the prostatic portion of the urethra iu a small fossa or depression, the sinus pocularis. The testicle is thus essentially a tubular gland. The length of the tubular structure in man has been estimated (Lauth) at 1800 feet. The appearance of one of the tubuli seminiferi, seen under a high power, is repre- sented in Plate XVII. fig. 2. It consists of a strong basement membrane lined with epithelium, and containing molecular matter, and large cells in which the spermatozoids are developed. At certain periods few of those large cells are seen, the tubuli containing chiefly molecular matter ; at other times they abound and contain one or more spermatozoids coiled up in their in- terior. (Plate XVII. fig. 3, 1.) iSpemiatosoids. — The form of the vibratile seminal particle varies in different animals. Various forms are shewn in Plate XVII. fig. 3 (see description of plate). In mammals generally, it has a round or oval extremity, a so-called Ji£ad, and a filiform appendage called a iaU, and varies in length from the 100th to the 500th of an inch (Plate XVII. fig 3, a to g). In birds, the thick extremity is more tapering, and the whole is of a spiral form (Kg. 3, h to k). In certain reptiles and fishes, the filament is much longer, and thickest in the middle, tapering at both extremities, having occasionally a delicate continuation wound spirally round the thicker portion (fig. 3, m to r). In some insects and Crustacea, they present curious irregular forms, without a filament, and are immoveable (Lower part of Fig. 3). In the vast majority of cases, however, they possess active contractile movements. In mammals especially, when watching these under the microscope, it is diflicult to divest oneself of the idea that they are animalcules, as they progress through the fluid with the heads forward, propelled by continued vibratile lashings of the tail. The notion put forth by some observers, that they possess internal organs, we have never, after careful FECUND A TION OF GERMS. 38 1 research, been'able to confirm ; and the circumstance that similar structures, with like movements, exist in the reproductive organs of many plants, negatives the idea of their being distinct ani- malcules. Hence, instead of spermatozoa, the term spermatosoids is more applicable to them. Mode of fecundation. — The mode of fecundation varies in diflferent animals. In some molluscous tribes, and in most plants, male and female organs are united in the same indi- vidual. Such an animal or plant is an hermaphrodite, and is usually self-impregnated. In fishes, the female sheds its spawn, and the male, swimming over it, sprinkles the, sper- matic fluid on the ova, and at certain seasons may be observed to f oUow her for that purpose. In the higher animals, union of the sexes takes place for the same end. In reptiles, especially in the frog and toad, the male clings to the back of the female, and sheds the semen over the ova immediately after they have left the cloaca. In birds and mammals, it is necessary that the spermatic fluid be deposited in the body of the female by the intromission of the male organ. From the circumstance that fecundation may take place in fishes and reptiles, as in plants, by simply sprinkling the male element over the female ova, has originated the modem practice of artificial impregnation. In the same way that horticulturists can multiply varieties, and even fertilise plants with pollen received from a distance ; so, by sprinkling the fluid from the milts of male fishes over the innumerable ova which may be squeezed from the roe of the female, they may be fecundated, preserved, and reared in artificial ponds. At this moment, many of the rivers and lakes of Trance, Scotland, and Australia are being stored with .large accessions of valuable fish so raised, in order to increase the amount of food for the people. For a long time it was supposed that the mere contact of the vibratUe spermatozoids with the ova was all that was necessary to produce fecundation ; but it was first shewn by Martin Barry, and has been subsequently confirmed by many other physiologists, that tJie spermaiozoid actually finds its way into the ovwn by a minute aperture, so that the male and female elements ultimately blend or melt into one another. (See de- scription of the development of the Ascaris Mystaoc, p. 48.) This fact may now be considered well established, and serves to explain many circumstances long known as to the resem- 38.2 CHANGES IN THE OVUM blances wMoh exist in feature and in qualities, mental and bodily, between parents and their offspring. Thus it has long been a matter of popular observation, that the child, in all that relates to the outward form, the gait and manners, takes after the father ; while as regards the size, internal qualities and dispositions, the mother predominates. Not, however, that the male is wholly without influence on the internal organs and vital functions, or the female wholly without influence on the external organs and locomotive powers of their offspring. The law is only general, although it holds very extensively among cattle, as shewn by Mr Orton and Dr A. Harvey. Such facts seem in their turn to be accounted for by the circumstance that the spermatozoid enters and melts down in the external parts of the yolk of the egg, — that is, in connection with those layers of the germinal membrane which, as we shall subsequently see, form the nervous system and muscles ; whereas the glands and internal organs are formed from the mucous layer, which is that part of the membrane furthest removed from the action of the male element. Changes in the Ovum which follow Fecundation. We have seen that ova are formed and discharged from the ovary at regular intervals by the adult female, but that it is only when the spermatozoid enters them that fecundation is produced. At that period the ovum presents the characters of a nucleated oeU, — the zona pellucida being the cell-wall ; the germinal vesicle being the nucleus ; the germinal spot the nucleolus ; while the fluid between them is opaque and granular, and called the vitellus, or yolk (Plate XVII. figs. 4 and 13). The size and relative amount of these three parts of each ovum vary in different animals, but they are present in all. If fecundation does not take place, the ovum degenerates, breaks down, and is ultimately excreted in the mucous discharge from the external passages. But if it encounter the spermatozoids, and one or more penetrate it, then those changes commence which terminate in the formation of an embryo. (See Plate XVII. figs. 14, 15, 18, 19, and 20, representing ova with spermatozoids in the interior.) These changes have now been followed in numerous animals, and the principal efforts of zoologists are at present directed to the elucidation of the transformations which take place at an early period in living beings ; so that the whole subject is not only very extensive, but is constantly acquiring new facts. The study of human embryology is incomplete, for, although, an ovum has been twice discovered after death in the Fallopian tube of woman (Letheby),* it has never been seen at that period when it enters the uterus. In the dog, rabbit, sheep, and other mammals, however, the various transformations have been very carefully described ; and, as it is certain that the same essential mode of development occurs in them as in man, the changes observed in the dog, according to Bischoflf, will be selected as a type of what takes place in the impregnated ovum of the higher animals. (Plate XVII. figs. 12-24, and Plate XVIII.) When the ovum leaves the Graafian vesicle, there is adherent to it externally a greater or less number of the cells wbich form the granular membrane. On removing these artificially, the ovum presents the appearance figured in Plate XVII. fig. 12, when magnified fifty diameters linear. ■ It is composed of a dark, opaque yolk, surrounded by the zona pelludda, or vitelline membrane. On cracking this ovum between two glasses, or on tearing it with a needle, the granular yolk flows out, and the germinal vesicle escapes, as in Pig. 13, a. If such an ovum encounter spermatozoids, the changes subsequently represented take place. One or more enter the ovum, when they and the germinal vesicle are dissolved in the yolk, — a circumstance to which the whole structure is indebted for its continuance and for its power of, as well as direction in, development. Development of the Emhryo. Th^ first change observable after fecundation is that the granular yolk begins to separate into two parts,— a process accomplished by the spontaneous aggregation of the molecules of which it is composed into two masses instead of one. (See page 39 and fig. 14.) Each of these two subdivide, producing four (Fig. 15) ; each of these into other two (Pig. 18) ; and so on, until at liength the whole is reduced into a mass of molecular corpuscles (Figs. 19 and 20), having a clear space or nucleus in their centres, and subsequently distinct cell-walls (Pig. 21). These corpuscles next arrange themselves in a layer externally, immediately lining the zotm pellueida, so as to form a mem- brane, which is called the germinal membrane (Fig. 17). At one * Philosophical Transactions. 1858. part of this, it will be observed that the cells collect in larger numbers, and are closely packed together, forming the germinal a/rea, where the embiyo first appears. The ovum has now entered the uterus, and its appearance at this period, magnified ten times, is represented in Kg. 16. By cutting or tearing out the portion of the germinal membrane which contains the germinal area, and magnifying it, the subsequent changes it undergoes can be well studied. The germinal area now enlarges ; at first round (Fig. 22), it becomes oval (rig. 23), and then theSre appears in it a clear space, — the area pdlumda (Kg. 24, c). At the same time, the germinal membrane becomes thicker, and is now divisible into two layers, — an upper or outer, called -the urous or animal, from which the epidermis and cerebro-spinal system are developed ; and an under or internal, called the mucous or vegetative layer, which ultimately forms the epithelium of the alimentary canal and its appendages. The future changes in the embryo may be observed by watching the changes in these two layers, and of another that afterwards forms between them in the germinal area, called the intermediate or vascular layer, from which are developed all the structures between the epidermis, on the one hand, and the epithelium of the alimentary canal and appendages, on the other. In the centre of the eidarged germinal area there now forms a groove or channel, the primitive groove, by an elevation on each side of the serous layer of the germinal membrane (Kg. 24, e). This groove enlarges anteriorly, and tapers to a point posteriorly (Plate XVIII. fig. 1), and ultimately becomes closed, by its sides, — laminoe dorsales, — ^passing over it and uniting, so as to form a tube. In the floor of this tube, the embryo brain and spinal cord are difierentiated in a way to be afterwards described. This tube is the cerebro-spinal canal. Underneath the canal there appears at a very early period a dense sub- stance called the chorda dorsalis, a structure represented in the idult chiefly by the intervertebral discs. From the chorda dorsalis, as from a centre, two laminae pass upwards, — ^& dorsal lomdnce, already referred to ; while two, the ventral lamince, pass downwards, and meeting below, complete the body of the smbryo (Figs. 1, 3, and 4). A linear mass of square-shaped 3eUs forms on each side of the chorda dorsalis, the so-called orimitive vertebrce, from which are formed the vertebral column md certain other parts (Plate XVIII. figs. 3 and 4). WtULLMl-fUl^J^UW J:'JL<^Ui\UJlllUl\. 385 The embryo is now raised prominently upwards above the serous layer (Fig. 2, which shews a lateral Tiew of the embryo), and between it and the mucous layer another mass of cells is formed which constitutes the third or vascular layer, above described. Here blood-vessels are developed from large trian- gular cells, so as to form a plexus (Plate XVIII. figs. 3 and 4) which unites with the embryo heart and aorta (Figs. 5 and 6). Thus a circulation is established, extending over the entire ovum, with the exception of its two poles (Fig. 7). The embryo is now raised still further above the surface of the germinal membrane, while the duplications and re-duplications of its three layers, which are constantly receiving thickness by cell growth, gradually produce the various organs and textures of the body. Three vesicles or sacs are formed in connection with these layers, — the Wmnios, or amnion (from a^»os, a sheep, because first observed in that animal), with the serous ; the allantois {i>.^is, ukkSmis, a sausage ; tiSa, shape) with the vascular ; and the umbilical {umbilicus, the navel) with the mucous layer. The upper or serous layer of the germinal membrane may be observed from an early period to be reflected backwards, from before backwards, and laterally, so as gradually to inclose the embryo in a sac (Figs. 3 and 5). This reflexion is at first double, but after it closes over the back of the embryo, the two layers separate from each other, the outer passing outwards to be incorporated with the zona pelhtdda, whUe the inner forms a sac, in which the embryo is suspended. (Fig. 7). It is the amnios or ammiotio scK. From the lower portion of the abdominal groove, and at the inferior extremity of the embryo, a swelling may now be observed (Figs. 10, 11, bb). This rapidly enlarges, and, at first open in the middle (Fig. 12, a), coalesces to form another sac, which hangs out of the lower portion of the abdo- minal opening. It is the allantois, a sac communicating poste- riorly with the alimentary canal and the ducts of the Wolffian bodies or primitive kidneys, the ureters. Fallopian tubes and vasa deferentia. This sac is seen at the lower part of fig. 10. , About the same time the middle layer of the germinal membrane, the vascular, spKts into two layers, the inner one of which, coalescing with the mucous layer, .forms the alimentary canal, whUe the outer is differentiated so as to form the muscles of the trunk and abdomen. The space left by the divergence of these layers of 360 JJlLVlLJLUrMILriJT UI' THU. :^Kt.l.KTUN. i the vascular membrane is represented in the adult by the pleuro-peritoneal cavity. As the ventral laminae, already de- scribed, meet in the middle line of the abdomen, part of the inferior or mucous layer becomes more or less constricted by the closure of the laminae so as to form a third sac or vesicle called the 'u/nibiUcoil sac. This sac is therefore the portion of the mucous layer left outside the body of the embryo — ^the portion within the cavity of the embryo becoming the alimentary canal. The outer (umbiUcal sac) is connected with the internal part by a pedicle or duct. The mode of formation and relation of these three sacs will be better understood from the diagram seen in Plate XVIII. fig. 9, in which a is the back of the embryo ; h the amnios ; o the umbilical vesicle connected with the embryo by a pedicle, d; and e is the aUantois growing backwards and down- wards, and continuous with the vascular layer by a pedicle /. The functions of these sacs may be briefly stated to be as follows. The umbilical vesicle, containing part of the yolk, is for the nourishment of the early foetus. The aUantois brings the blood of the foetus into relation with the surrounding media for the purposes of nutrition and respiration. It is seldom of large size in mammalia, because it is soon supplanted by another organ, 7Ac placenta, into the structure of which it enters. The amnios secretes a fluid, termed amniotic fluid, in which the foetus floats, and by its reflexions it permits the aUantois to pass outwards so as to contribute to the formation of the placenta. Development of the Chorion. — While the ovum is very small, its outer surface becomes shaggy from the appearance of nume- rous vOli. These viUi, at first simple, soon become branched by lateral processes passing from them (Plate XVIII. fig. 11). This villous covering is the chorion. Bevdopment of Special Organs in the Embryo.* Development of the shdeton. — Immediately below the primitive cerebro-spinal canal there appears in the middle or vascular layer, a structure termed the chorda dorsalis, or notochord, Bonsisting of large ceUs, surrounded by a thin sheath. About the same time, small square-shaped masses are to be seen on each side of the chorda dorsalis (Plate XVIII. figs. 1, 2). These are the primordial vertebrae, and each pair is ultimately * For further details reference is made to works specially devoted to the sub- iect. See also description of Plates XVII. and XVIII. L)lLV±Ll.UrMJLJMr Ut IH±. HKJiLETON, 387 developed by differentiation into the osseous and cartilaginous portions of a permanent vei-tebrae, the head of ii rib, the central parts of a spinal system of nerves, and the cutaneous and mus- cular parts covering the back.* During this prqcess of develop- ment, the chorda dorsalis becomes constricted, and ultimately portions of it form the centres of the bodies of the permanent vertebrae, whUe other portions are persistent in the intervertebral disks. Thus the vertebral column is formed. DevdopmerU of the shvll. — At a very early period of foetal life, two curvatures are to be observed near the anterior ex- tremity of the embryo, one at the point corresponding to the junction of the vertebral column -with the skull, and the other opposite to the second cerebral vesicle. Behind the latter curva^ ture, the dorsal plates bend downwards and unite iuferiorly, so as to form four arches, behind each of which there is a cleft or fissure, termed a branchial deft (Plate XVIII. fig. 14, d, f). The posterior part of the first cleft remains open in the fuUy developed foetus as the external aperture of the ear, the cavity of the tympanum, and the Eustachian tube, while its anterior part, along with all the other clefts, are ultimately obliterated. We have now toconsider, first, the development of the cranium', and second, that of the face. 1. The crcmium. — The chorda dorsalis terminates at the posterior part of the sella turcica, the fossa in the base of the skull for the reception of the pituitary body. In front of this point, two thick bars of cartilage, separated by a thinner portion between them, pass forwards, and unite in front of the ethmoidal region. These have been termed the lateral trabeculce of Rathke. The whole of the base of the skull is now cartila- ginous, whUe the vault of the cranium is membranous. The cartilaginous portion ossifies and differentiates into the occipital bone below its protuberance, the petrous and mastoid portions of the temporal, the sphenoid and ethmoid ; whUe the membranous portion becomes the parietal, frontal, upper part of the occipital, and the squamous portion of the temporal. The vomer and perpendicular plate of the ethmoid are developed from a vertical process of cartilage passing forward from the neighbourhood of » Quain's " Elements at Anatomy," 1867, p. 16 ; Goodsirt " Anatomical Me- moirs. On the Morphological Constitution of the Skeleton of the Vertebrate Head," Tol. ii., p. 89, et sej. 2 388 DEVELOPMENT OF THE SKELETON the termination of tlie chorda dorsalis, called the ethmo-wmeriiK cartilage.* 2. The face. — The bones of the face are all originally cartila- ginous, and are developed as follows : A process passes from the upper or first visceral arch forwards beneath the eye, and forms the sides of the face, namely, the superior mazillary and malar bone (Plate XVIII. fig. 14, e). Coincident with the development of the two processes just, described, another pro- cess, called the middle frontal process, passes down from the anterior extremity of the ethmo-vomerine cartilage between them, and becomes the nose and middle part of the upper lip. The lower part of this process bears the upper incisor teeth. In man it is blended, even at a very early period of foetal existence, with the sv/perior mamUcu-y process ; but in all other mammals it remains separate as the intermaxillary or premaxillary bones. In the three upper visceral arches, narrow strips of cartilaginous tissue make their appearance. These are the subjects of re- markable changes. The first, or upper piece, is divided into three parts : the proximal, or .that in connection with the basis cranii, is developed into the palate plate and internal pterygoid process of the sphenoid bone ; the second forms the incus and its two processes j while the remaining part, long and narrow, passes downwards and forwards so as to unite with its feUow of the opposite side, and is called Meckel's cartil- age. The upper part of this cartUage forms the" malleus and its handle, and the lower part forms a rod, on the external surface of which the lower jaw is developed. It ultimately disappears, except a small portion, which is represented by the processus ffracilis of the malleus. The proximal extremity of the firm tissue in the second arch forms the stapes, and the distal extremity the styloid process of the temporal, the stylo-hyoid ligament, and the small cornua of the hyoid bone. A por- tion of that of the third arch forms the great cornua and body of the hyoid bone. Thus are formed the bones of the face and ear. Development of the limbs. — The upper and lower limbs are developed from the ventral plates on the sides of the body. The upper limb appears before the lower, and according to KoUiker, the division into arm and fore arm, thigh and leg, occurs about the eighth week. About the same time the division * Quain's " Elements of Anatomy," 1867, p. 66. AND THE ORGANS OF CIRCULATION. 389 into fingers and toes also takes place (Plate XVIII. figs. 10, 13, 15). Devdopmesfd of the orgcms of ciroulation. — The heart is at first a mass of cells, shewing rythmical contractions even before muscular tissue is developed, but at an early period it is a simple dilated tube having two veins entering its posterior end and a large arterial trunk passing from its anterior. The tube soon becomes constricted in two places, so as to form three compart- ments, the posterior of which is the auricular portion, the middle the ventricular, and the anterior the bulbus arteriosus. Septse next make their appearance in these compartments, so as to divide the auricular portion into the two auricles, the ventri- cular into the two ventricles, and the bulbus portion into the aorta and pulmonary artery. The heart also becomes twisted upon itself somewhat like the letter S, and this process goes on until the two auricles are anterior, at the base of the heart, the two ventricles posterior, forming the cone. From these originate the pulmonary artery and the aorta (Plate XVIII. figs. 3 and 6). The bulbus arteriosus is at first a tube which, after passing forwards a short distance, splits into two. These diverge, but afterwards unite to form a large tube running down behind the heart in front of the vertebral column. This tube is the descending aorta. Thus two arches are formed. Pour other pairs of arches are also developed, each arch being placed in one of the branchial processes already described (fig. 14). These arches never co-exist, as the highest disappear before the lower are developed. This transitory arrangement of blood-vessels resembles somewhat the branchial arteries in fishes ; but it soon disappears. Elnbryologists have not satis- factorily traced the development of these vascular arches into permanent structures. According to some, the fifth or upper- most arch remains persistent as the anastomosis between the internal carotid and vertebral arteries through the circle of the WUlis at the base of the brain ; the fourth, as the inosculation between the superior thyroids of the external carotids and the inferior thyroids of the subclavian ; the third, as the subclavian arteries ; the second, becomes, on the left side, the arch of the aorta, while that on the right side disappears ; and the first is represented in the foetus by the ductus arteriosus on the left side, the right having disappeared at an earlier period.* * For further details regarding the development of the great arteries and veins, 390 DEVELOPMENT OF Development of the nervous system. — The spinal cord and encephalon are developed in a deposit of blastema in the bottom of the primitive groove. As this groove is formed by the seroug layer of the embryo, it follows that the cerebro-spinal system is developed from this layer. The layer of blastema, composed at first of cells uniform in size and appearance, increases in thickness in each lateral half so as to form a furrow or groove, the sides of which growing upwards and uniting produce a tube or cylinder, which is represented in the mature condition by the ventricles of the brain and the cerebral canal of the spinal cord. According to Eemak and KOUiker, the posterior roots of the spinal nerves, with their ganglia, are separately developed and grow inwards towards the cord, while the anterior pass outwards from the cord. The nerves are developed from difierentiated masses of blastema, and grow inwards till they reach the cord. Thus we have formed the spinal cord, with the various motor and sensory nerves ramifying through the body. With regard to the development of the brain, it is first to be noted that it is really a portion of the nervous tube just described, modified into various ganglionic masses, There is at first no enlarge- ment representing brain, a condition which is persistent in the Amphioxus lanceoUzius.* Soon, however, the anterior part of the medullary tube enlarges, and becomes constricted into three parts, so as to form three vesicles, called the primary cerebral vesicles (Plate XVIII. figs. 4, 5, 6, and fig. 8, a, b, e, d). These three vesicles are at first in a straight liae ; but three bends make their appearance : the most posterior, at the junction of the posterior vesicle with the spinal corci ; the next between that part of the third vesicle forming the medulla and that developed into cerebellum ; and the anterior appears in the middle vesicle between the parts from which are developed the optic thalami and corpora quadrigemena. The anterior is now placed nearly at a right angle with the middle vesicle. The following changes next occur in these three vesicles. Beginning with the posterior primary Vesicle, we find that its floor is developed into the medulla oblongata (a continuation of the cord). The posterior part of its roof is never closed by nervous matter, having only membrane over it, and this open part is reference is made to Kblliker, *'Eiitwicklungsgeschichtej'*p. 412, etseq, Quain, rol. i. pp. 325 and 488, Ac. • Goodsir's " Anatomical Memoirs," vol. i. p. 378. THE NERVOUS SYSTEM. 398 represented in the adult by the floor of the fourth Ventricle, communicating below with the canal of the spinal cord. The anterior part of the roof is diflferentiated into the cerebellum, and the transverse commissural fibres of the cerebellum consti- tute VaspoTM Varolii. The vermiform process of the cerebellum appears before the two lateral hemispheres. In the floor of the middle or second cerebral vesicle, matter is deposited so as to form the crura cerebri, and in the roof we have developed the corpora gMffldngiemcBO, an antero-posterior median groove being first seen about the sixth month, and a transverse, separating the testes from the rules, first making its appearance about the seventh month of intra-uterine life. The primitive cavity of the second cerebral vesicle remains persistent as the Sylvian aqueduct, or itesr a terlio ad qmrtum ventriculum. The develop- ment of the anterior primary cerebral vesicle is more complicated. At a very early period, two vesicles are developed from the anterior primary vesicle, one on each side. These" vesicles have been termed the hemisphere vesicles, because from them are developed the hemispheres — the corpora striata appearing in the floor, while the hemispheres, properly so called, constitute the roof. The external surface of the mass termed corpora striata is the Island of Beil, seen in the Sylvian fissure. The cavity of these vesicles is represented by the lateral ventricles, and between the double partition separating them, we have the fifth ventricle. The cavity of the anterior primary vesicle, behind the cerebral vesicles, forms the third ventricle, the floor being formed by the optic ihalami which are at flrst hollow, while the roof is formed by the velur/i interpositum, a layer of pia mater ^ which is folded into the brain through the transverse fissure. As develop- ment proceeds, the communication between the cavity of the anterior cerebral vesicle (third ventricle) and those of the hemi- sphere vesicles (lateral ventricles) becomes smaller and smaller, and ultimately constitutes tlae foramen ofMunro. The margin of this f Of amen forms anteriorly the fornix, an antero-posterior commissural set of fibres, and posteriorly the corpus fimbriatum and hippocampus major, and as the hemispheres increase in size they grow backwards, so as to overlap the optic ihalami, corpora qua'drigemena, and cerebellum. The great transverse commis- sural mass, corpus eallosum, is first seen about the end of the third month. The first trace of convolutions is seen about the fourth month. They are at first indistinct, and continue so till 392 DEVELOPMENT OF the seventh month, after which they are rapidly developed. The Sylvian fissure appears at the fourth month, and is soon followed by the fissure of Rolando. Such is an outline of the development of the brain. Bevdopment of the eye. — The eye first appears as a hoUow process in connection with the anterior cerebral vesicle (Plate XVIII. fig. 5, where the first cerebral vesicle is expanded laterally; fig. 6 ; fig. 8, e; and fig. 13, 6). This process soon becomes a round vesicle {primary optic vesicle) connected pos- teriorly with the anterior cerebral vesicle by a hollow pedicle. The optic vesicle now approaches. the cuticle and becomes inva- ginated,- carrying a portion of the cuticle along with it. This invaginated portion of cuticle, at first a pouch, becomes con- stricted to form a sac, and is ultimately severed from its connection with the general cuticle, thus forming the lens. The primary optic vesicle now undergoes a second invagination behind the lens until the opposite surfaces come into contact^ and the cavity of the primary optic vesicle disappears. Accord- ing to ESUiker, the invaginated portion forms the retina and the layer of hexagonal pigment cells in the choroid ; and the outer portion, the pigmentary (branching pigment cells) and probably the vascular part of the choroid. The cup-shaped cavity behind the lens, called the secondary optic vesicle, is soon filled with the vitreous humour. The iris is developed about the second month as a septum projecting from the anterior part of the choroid. The sclerotic and cornea are formed from tissue external to the eye. The lens in the foetus is surrounded by a vascular tunic, the fore part of which is persistent in the young of many animals for several days after birth. It is then termed the pupillary membrane. In the human being it is atrophied before birth. The eyelids are folds of integument. The lachrymal canal is the representative of the fissure between the frontal process and the maxUlary lobe of the embryo.* Development of the ear. — The ear is developed ifrom ,a vesicle, the primary auditory vedcle, above and behind the second branchial arch (Plate XVIII. fig. 5, where the embryo ears are seen opposite the third cerebral vesicle ; fig. 8,/). This vesicle, however, is not a process from the brain, as is the case in the eye, but an invagination of the cuticle. The first part developed is the membranous labrynth, afterwards the semicircular canals, * Quain, vol. ii. p. 737-9.' THE ORGANS OF SENSE. 393 and finally the cochlea. The osseous labrynth is developed from cartilage, continuous with the cartilage at the base of the primordial cranium. The stages of development of the intri- cate portions of the cochlea have not yet been clearly made out. The development of the middle and external ear have been already described. The external meatus, tympanum, and Eustachian tube are the remains of the upper part of the first branchial cleft ; the incus and malleus are formed from the upper part of Meckel's cartilage (part of the first branchial arch), while the stapes is derived from the cartilage of the second branchial arch. Beedopmeni of the nose. — The nose is a development of the integument (Plate XVIII. fig. 13, as). The olfactory bulbs, at first hollow, are processes from the two vesicles which ulti- mately form the cerebral hemispheres (p. 394). It has not yet been made out whether the olfactory nerves grow from the bulbs, or originate, like other nerves, from separate masses of blastema. The nostrils first appear as two grooves separated by the frontal process. They are shut off from the eye' by the lateral frontal process, and the side wall of the'nostrU is com- pleted by the maxillary processes. The nostrils at this period communicate with the mouth. The palate is now developed by transverse growths towards the middle line, and ultimately they unite. Sometimes we have, by their non-union, the congenital deficiency known as cleft-palate. ' Development of the alimentary canal. — The alimentary canal first appears as a groove directed towards the yolk. The groove is lined by the mucous layer of the embryo, which ultimately forms, as already mentioned (p. 384), the epithelium of the canal. The wall of the groove is formed by the deeper divi- sion of the intermediate or vascular layer of the embryo. The groove soon closes, so as to form a long, straight tube, stretch- ing in front of the vertebral column from the base of the skull to near the posterior extremity of the embryo (Plate XVIII. fig. 13, m, and fig. 15, l). This tube, however, communicates with the yolk-sac, or umbilical vesicle, by an opening on the ventral aspect, which speedily becomes a narrow duct, named the omphalo-enteria duct (Fig. 9, d; fig. 15, m). This duct soon disappears. The intestine now forms a curve or loop in the centre of the body, and a portion dilates to become the stomach (Fig. 13, e, and fig. 15, k). The stomach is at first vertical, turns 394 DE VELOPMENT OF LIVER, Over on its right side, so that the right lateral surface becomes its posterior surface. This explains the anatomical fact of the right pneumogastric supplying the posterior aspect of the stomach, while the left supplies its anterior aspect. The great intestine, at first narrower than the smaU, in the early embryo shews' no caecum. The mouth is developed by an infolding of the integument above the highest branchial arch, and is separated at first from the pharynx by a partition. The anus and lower part of the rectum are also invaginations of the outer surface. It is remarkable that viUous processes are at first foimd throughout the whole alimentary canal, but ultimately disappear in the stomach and large intestine. Occasionally, diverticula are found in the adult in connection with the lower part of the ileum. These are believed to be remains or develop- ments of the original omphalo-enteric duct. Umbilical hernia arises from the want of complete apposition of the wall of the abdomen at the umbilicus. Deoelopment of the liver. — The liver appears as two cul-de-sacs or tubes, arising from the intestinal canal immediately beneath the dilation for the stomach (Plate XVIII. fig. 13, h, and' fig. 15, i, i, i). These processes, according to Eemak, consist both of the epithelial and muscular parts of the intestine. They increase in size by the development of glandular substance, and surround the omphcdo-mesteric vein, the vein bringing blood from the umbilical vfesicle, and from the wall of the primitive aliment-ary canal (Figs. 6 and 7). As the umbUical vesicle decreases in size, the omphalic portion of the vein also decreases, and the mesenteric portion coming from the alimentary canal becomes the portal vein. The continuation of the omphalo- mesenteric vein passing from the liver to the general circulation receives the name of the hepatic vdn. At this period, then, the liver is supplied with blood chiefly by the portal vein. Coincidently with these changes, the allantois is being developed so as to form, along with the decidual membranes, the placenta ; and as the placenta increases in size, a time arrives when the liver receives more blood by the umbilical vein, or vein coming from the placenta, than from the portal vein.* The umbilical vein, on reaching the liver, divides into two branches ; one of these, the smaller, passes onwards to the vena cava inferior, and is called the ductus venosus; the other joins the vena poriw. * Dalton's Physiology, p. 664. LUNGS, AND BLOOD GLANDS. < 395 Several other small branches are given, off by the umbilical vein to the Uver. After respiration is established, and blood ceases to come by the umbihcal vein, it and the ductus venosus contract and shrivel up, the umbilical vein constituting the round ligament of the liver, whUe the ductus venosus disappears. (See pp. 224, 225, and Plate XI. fig. 16, and description.) Development of ■the salivary glands, and pancreas. — These organs are developed as simple canals with small processes passing them. In the case of the salivary glands, these canals communicate with the mouth, while that of the pancreas arises from the left side of the intestine, close to the spleen. Development of the organs of respiration and organ of voice. — The lungs are at first diverticula from the oesophageal portion of, the alimentary canal, and their internal cavities are lined by a prolongation of the lining of the oesophagus. At a later period, they are connected with the digestive tube by a pedicle which becomes the trachea (Plate XVIII. fig. 15, a). The lungs ai-e seen at a very early period of development, and the air cells are rapidly developed round the extremities of the ramified bronchial tubes. UntU birth, the lungs are of small size, and occupy a small space at the back of the thorax. On respiration being established, they expand so as to fill the cavity. The rudimentary larynx appears as two slight enlargements separated by a fissure, and embracing the communication between the pharynx and trachea. According to Eathke, all the true car- tOages are formed at the same time. The larynx is small in childhood. In the female, the larynx retains its comparatively small size, and rounded thryroid cartilage anteriorly ; but in the male the cartilages become stronger, and the alae of the thyroid cartilage project forwards so as to form the pomum Adami. ' The vocal cords are thus lengthened. The cartilages undergo partial ossification from middle life to old age. Development of the blood glands. — The spleen appears about the seventh week, close to the pancreas, but by the tenth week it is placed at the great end of the stomach. It is developed in a special mass of blastema. Kblliker has observed the thyroid gland at the end of the third month, as consisting of shut sacs with cells in their interior. This organ is relatively larger in the foetus than in after life. The thymus gland (Plate XVIII. fig. 15, 6) has been seen by Simon in embryoes of swine and oxen about haU an inch in length, as a simple tube. From 396 DEVELOPMENT OF THE URINARY this tube lateral diverticula arise containing corpuscles. By the twelfth week, the thymus consists of lobules ; it rapidly increases in size during foetal life, and continues to grow after birth to the end of the second year. By the tenth or twelfth year it becomes a fatty mass, and at puberty it has almost disappeared. The supra renal capsules originate from blastema diflferent from that of the kidneys. Some observers (Goodsir) have seen at an early period these organs apparently in one mass, others in two separate masses united together, while many have seen them at birth completely separated from each other. At one period, about the fifth or sixth week, the supra-renal capsules are larger than the kidneys, but ultimately they become much smaller. Nothing whatever is known definitely of the development of the lymphatic glands, Peyer's glands, pituitary body, -or pineal gland. Deedopmeni of the urinary and generaiwe organs. — ^At a very early period in the development of the human embryo, two ridges of blastema appear, one on each side of the primitive straight alimentary canal. These increase in size, — ^vesicles, and afterwards tortuous csecal tubes, are developed in them, com- municating with a duct which runs along the outer side of each organ. These are the primordial kidneys or Wolffian bodies, named after their discoverer, C. F. Wolff (Plate XVIII. fig. 13, / fig. 15, o). The ducts open into the allantois, and a whitish excretion, containing uric acid, has been found in them and in the aJlantois. As development progresses these bodies decrease in size, and ultimately almost entirely disappear, their ducts, however, becoming modified into certain- permanent structures, as will be afterwards described. The kidneys are not developed from the WolflSan bodies, but from separate masses of blastema behind their upper end. At first smooth, the kidneys soon become lobulated, each lobule consisting of a number of csecal tubes which are modified into the tuhuli uriniferi. The Malpighian todies have been seen at a very early period. The ureters are believed by Eathke to commence separately from the kidneys, and afterward to become united to them. The ureters open into the allantoid sac. The lower part of the allantois is retained in the abdomen by the closure of the ventral walls at the umbilicus, and receives the ducts of the "Wolffian bodies and of the ureters. This portion becomes dilated, and afterwards constitutes the urinary bladder (Fig. 9, /). The contracted part above this dilated portion. AND GENERATIVE ORGANS. 397 passing from the bladder to the umbilicus, is afterwards known as the urachus. The bladder at first communicates freely ■with the lower end of the alimentary tube. This general cavity is called the cloaca, and represents the permanent condition in birds and reptiles. Soon, however, a partition is developed, dividing the cloaca into two parts, the posterior constituting the rectum, opening externally. by the anus, while the anterior has been termed the sinus urogeniialis, and receives the ducts of the Wolfifian bodies as well as those of the kidneys and of the ovaries or testes. The generative organs are developed from separate masses of blastema on the inner aspect of the Wolffian bodies. It cannot at first be determined whether male or female organs are to be the result of the development. The Wolffian bodies are pushed outwards by the development of the kidneys above and between them, and they gradually decrease in size. A white elongated thread-like mass of blastema is seen on the front of each Wolffian body, running along the duct. This becomes a tube termed the Miillerian duct. The Mullerian ducts become fused together at their lower end, and, along with the ducts of the Wolffian body, form a single cord — the genital cord. Now commences a distinct differentiation between the organs of the sexes. In the female, the portion of the Miillerian ducts united together is developed into the vagina, cersvv, and lower part of the bod^ of the uterus. This partial formation of the uterus by the union of two ducts explains the occurrence occasionally of a double or homed uterus. The upper part of the body of the uterus and the Fallopian tubes are formed by the remaining upper portions of the Mullerian ducts. A very different development occurs in the male. Here the Miillerian ducts undergo little development, and are repre- sented in the adult by the vesicula prostatica, sinus pocvlaris, or utricle, first described by Morgagni, and situated in the floor of the prostatic portion of the urethra, and in fi?ont of the caput gallinaginis, or verumontanum. This little recess, therefore, represents in the male a portion of the uterus and the vagina in the female. The united portions of Miiller's ducts dis- appear. The male organs of generation are developed partly from the mass of blastema already referred to, and partly from the ducts of the Wolffian bodies. The ducts of the latter form the vasa defereniia and ejaculatory ducts, the vesicula seminales being cul-de-^cs from their lower part. Part of the duct of the 398 DEVELOPMENT IN THE HUMAN OVUM. Wolffian body becomes the epididymis. According to Cleland and Banks the coni vasoulosi are developed from separate deposits of blastema. The testicles are, until the seventh month, in the abdominal cavity. They then descend through the internal inguinal ring into the scrotum pushing a pouch of peritoneum before them. This pouch becomes constricted, and is ulti- mately cut off from the abdommal portion of the peritoneum, so as to form the tunica vaginalis^ The external organs of genera- tion are first represented by a small body projecting from the median line in front of the cloacal opening, having a groove on its under surface. This body is the rudimentary organ which becomes the clitoris in the female and the penis iij the male. ' About the eleventh or twelfth week, a transverse band divides the anal from the genito-uriuary passage. Two cutaneous folds, one on each side of the clitoris, become, in the female, the labia majora. In the male, the penis enlarges, and the margins of the groove on its under surface unite so as to form the urethra. The lateral cutaneous folds already mentioned unite so as to form the scrotum. When the union of the urethra canal is not complete, and the penis is smallj we have then the condition of hypospadias. 7;i the human ovum similar changes occur to those in the dog. The early stages, indeed, may be said to be identical. The umbilical vesicle and allantois, however, never become so large, and according to a dissection of a foetus by Miiller, supposed to be twenty-eight days old, union between the two may be observed even at that early period. The amnion is formed in the same manner as in the dog, very early, and con- tinues during the whole period of intra-uterine life, constituting the membrane that surrounds the foetus. On the chorion, the villi become concentrated on a particular spot, while the rest of its surface become smooth. The allantois grows into this part of .the chorion, and blends with it, as will be afterwards more particularly described. About the beginning of the second month, the umbilical vesicle begins to disappear, it shrinks together, its peduncle uniting with that of the allantois to con- stitute the umbilical cord. Its remains may sometimes be traced in the foetal coverings at birth. All the organs are now evolved, and are gradually perfected during the remainder of intra-uterine life. ' DE VELOPMENT IN BIRDS. 399 In birds. — The same process previously described occurs essentially in the egg of the bird. In the bird there is no uterus. The ovum is maturated out of the body of the animal. In the ovary of the common fowl, numerous eggs may be seen in various stages of development. When discharged from the ovary into the Fallopian tube or oviduct, the egg consists of a large globular yellowish yolk inclosed in a transparent vitelline membrane. At one spot on the surface of the vitellus, there is a round white spot, the " cicairicula," in the centre of which is the germinal vesicle. The peristaltic actions of the muscular wall of the oviduct forces the egg downwards, and during its passage a homogenous layer of a gelatinous depbsit is formed around the vitelline membrane. This is termed the " chodazi- ferousr tnerribrane. The egg is stiU pushed downwards with a ' slow rotatory motion, and the chalazif erous membrane is twisted in opposite directions so as to give rise to two fine cords, running from the opposite poles of the egg, termed the " chalazcB ;" and from the mucous membrane of the oviduct there exudes an albuminous substance, the so-called albumin, or " white of egg." In the next part of the oviduct, another material is deposited outside the albumin, in the form of three distinct membranes, layers, or envelopes ; and in the lower part of the oviduct, which is wider than the rest of the canal, the villous mucous membrane transudes a iluid containing a large amount of calcareous salts, which are deposited amongst the fibres of the outermost layer. Thus, the shell of the egg is formed. The egg is finally discharged through a narrow portion of the oviduct, and finally from the external orifice. ■ The shell, although it has no visible pores, is stiU permeable to air, a condition essential to the future development of the embryo, for it has been found that if the shell be covered with a layer of varnish, the egg dies. The ovum of the bird contains all that is necessary to perfect the embryo, and it receives no further nourishment from the mother. On this account it is furnished with a much larger amount of albumin and yolk, which are metamorphosed by cell growth, into the tissues of the chick. During this metamorphosis some chemical change is continually going on, and material, such as watery vapour, must pass out through the shell, for the egg is daily losing weight. Soon after the egg is passed, a small quantity of air passes through the shell at the rounded extremity, and accumu- 400 CHANGES IN THE UTERUS lates between the internal and middle fibrous membranes. The viteUus or yolk, being lighter than the albumin, rises towards the surface of the egg, with the cioatricula uppermost, so that in whatever situation it may be placed, it is next the warm body of the mother during the hatching period. The three embryonic sacs are also developed in the egg, and the ajlantois, at an advanced period of incubation, lines nearly the whole of the shell. By this sac, the chick breathes ; for it has been shewn by Baudrimont and Ange,* that during eighteen days' incubation the egg absorbs nearly two per cent, of its weight of oxygen, while the quantity of, carbonic acid exhaled from the sixteenth to the nineteenth day amounts to three grains in twenty-four hours. .At length the chick is strong enough, partly by means of its beak, and partly by its struggles^ to break its covering and escape. Chanobs in the Utertjs which follow !FeOTJNDATIO!I. We have now to consider the changes that take place in the uterus after fecundation. As the ovum descends the Fallopian tube, the uterus is being prepared for its reception. The mucous membrane of the uterus contains numerous small tubular glands or follicles, and it is covered with ciliated epithelium. On impregnation, the mucous membrane becomes more vascular, increases in thickness, and biilges into the cavity of the uterus in the form of small rounded processes. The glands also increase in size, and pour out a copious secretion. This thickened mucous membrane is called the decidua vera. When the ovum reaches the cavity of the uterus, it becomes entangled in the decidua vera, a portion of which is rapidly developed round it. This' latter portion is the decidua reflexa, so called because it is reflected over the ovum. At this stage the ovum is covered by the shaggy coat of the chorion. The villous tufts of the chorion are pushed into the follicles or glands of the two decidua, and absorb from these glands a nutritious fluid for the support of the ovum. But as the foetus is further developed, a larger supply of nourishment is necessary, and the blood of the foetus must be brought into nearer relation to that of the mother. This is accomplished by means of an organ called t\i& placenta. Formation of the placenta. — ^As already mentioned, the villi of the chorion disappear, except at a particular portion of its sur- * Du Developement du Foetus. Paris, 1860, p. 143. WHICH FOLLO W FECUND A TION. 40 1 face — ^the portion opposite to the allantois. This is the situation of the future placenta. This organ consists essentially of a fcetal and a maternal portion. The/atoZ part is formed by the villous tufts of the chorion, containing loops of capillaries derived from- the allantois. It is connected with the foetus by the umbilical cord, and both it and the cord are covered by a reflection of the amnion. The maternal portion consists of the decidua, or hypertrophied mucous membrane, containing the uterine follicles. As already explained, these follicles become much enlarged, so as to allow the tufts of the chorion to be pushed into them, and at the same time the blood-vessels or veins ramifying on the outer surface of the follicles rapidly increase in size, and thus form large sinuses, termed the uterine sinuses. These sinuses exist in the decidua, not in the wall of the uterus, and they and the uterine follicles mould themselves over the outer surface of the villous tufts of the chorion, as seen in Plate XVII. fig. 8, a, b, 0, d. Thus the blood of the foetus is in close proximity to that of the mother, but is separated from it by the following rjembranes, which become more or less fused together : first, the wall of the foetal capillary (Plate XVII. fig. 10, g) ; second, the chorion (e,/) ; third, the waU of the uterine follicle (6) ; and fourth, the waU of the uterine sinus (a). Ac- pording to Goodsir, there are two layers of cells between the foetal and maternal portions of the placenta, — first, a layer on the lining of the uterine sinus, h {external cdls); and second, a layer on the chorion, e,f {internal cells). The function of the external cells is to absorb nutrient matter from the blood of the mother, while that of the internal is to absorb this matter from the external, and pass it into the blood of the ohUd.* Through these membranes, the blood of the foetus receives nutritious matter from, and gives up impurities to, that of the mother, probably by processes of endosmose and exosmose. During ' pregnancy, the involuntary contractile fibre of thte uterus becomes gradually hypertrophied so as to increase the power ef the uterus. Parturition. — The process of parturition takes place a few days beyond the end of the ninth calendar month. During pregnancy, the involuntary contractile fibre of the uterus is enormously hypertrophied. The foetus is expelled by the • Ooodsir. The Structure of the Human Placenta. " Anatomical Memoirs," p. 445. 402 GENERAL CONCLUSIONS, contractile force of the uterus, aided by the abdominal and other muscles. It is soon followed by the expulsion of the placenta. When the placenta separates, the uterine vessels are torn across, but the orifices are speedily closed by the contraction of the uterus. The whole placenta, maternal and foetal, including the uterine sinuses, uterine glands, and tufts of the chorion, separates, and the haemorrhage which usually takes place does not come from the uterine vessels, but from the large sinuses in the placenta. After parturition, the muscular walls of the uterus atrophy by fatty degeneration, and the mucous membrane is renewed. General eonclwions. — Such is a general sketch of the various stages of the function of reproduction, a study of which in the different classes of animals has led to the formation of various ingenious hypotheses, whereby it has been sought to bring the order of evolution within the operation of certain laws. One of these, which has excited great attention, is, that the human foetus passes through transition periods resembling in turn the different inferior beings of the animal scale : that is to say, it at first resembles a zoophyte, then a mollusc, then a worm, a fish, a reptile, and so on. Thus the monads found among the inferior animals have been supposed to be represented by the germinal vesicle. The yolk, when divided, has been thought to resemble a gonium or a volvox. When the primitive groove closes, it has been likened to a worm ; afterwards to a molluscous animal j and when the visceral arches appear, to a fish ; and so on. This method of viewing the phases of development has led to a generalisation thus expressed by Serres, — ^viz., that " Human organogenesis is a transitory comparative anatomy, as in its turn comparative anatomy is a fixed and permanent state of the organogenesis of man." But that the human embryo ever resembles a worm, a mollusc, reptile, fish, or bird, can, on careful examination, nowhere be recognised. It is true that at one period all ova resemble each other ; but it is equally certain that from the first moment of their formation they are im- pressed with a power of developing themselves in a certain direction, so that the ovum of a reptile, fish, or bird, wiU. always be developed into similar animals, and by no concurrence of circumstances wUl ever be transformed into different ones. Neither is there any anatomical or structural relation between LACTATION. 403 them, for the visceral arches in the human foetus are in no way, as has been supposed, analogous to the bvanchise or lungs of the fish, for the former are partly transformed into the bones of the face, while lungs originate in inflections of the mucous layer. The theory, then, may be considered as more fanciful than real, and founded upon loose analogies, which, instead' of being strengthened, are weakened as development proceeds, and the true types of such analogies become more evident. Lactation. The most natural food for the infant is the mOk of the mother. This fluid is secreted by special glands termed the mammary glands. lu the human female, they form two rounded masses, the breasts, placed one at each side on the front of the thorax. They are essentially compound racemose glands, re- sembling in structure the pancreas and salivary glands. They consist of a number of lobes or lobules, from which proceed about fifteen or twenty ducts, called galadophorous duds. These converge towards the areola, or circle round the prominence, or nipple, where they form simtses. From these sinuses, small ducts pass to the surface of the nipple, where they open by separate orifices. When examined by a high power, the small vesicles and ducts of the gland are found to consist of a waU, of areolar tissue lined by a mucous membrane, having tasselated epithelium. They are usually filled with molecular matter. The secretion of milk commences during the latter period of pregnancy, but it is not fairly established until two or three days after delivery. Its appearance is usually ushered in by a feverish condition, " milk fever." The fluid secreted during the first few days after delivery is of a yellower colour than that secreted afterwards, and is termed colostrum. This mUk is believed by some to act as a natural purgative to the infant. Afterwards the milk is white, or bluish white, opaque, has little or no smell, and a slightly sweet taste. Histological structure of milk. — When a drop of mUk is examined with a magnifying power of 250 diameters, it is found to consist of a fluid in which there are numerous globules of various sizes, varying from the 1/2500 to 1/1500 of an inch in , diameter (Fig. 1, p. 404). These globules are very refractive. 404 LACTATION. They are often in groups, but in healthy milk readily roll upon one another. On the addition of acetic acid they may be seen melting together, so as to form larger globules, -which may then be dissolved by ether. Thus we learn that each milk globule consists of an envelope of albumen surrounding a drop of oU, and an appearance very similar to milk can be artificially prepared by first forming the Haptogen membrane of Ascherson, as already described at p. 36, and then rubbing the covering glass with a circular motion, so as to break up the membrane. Colostrum is found to contain, in addition to the ordinary milk globules, numerous large, irregulajr, globular bodies, from the 1/1100. to 1/800 of an inch, termed " colostrum corpuscles." They contain numerous minute oily granules (T^g. 2). Fig. 1. Fig. S. Chemical composition of milk. — The specific gravity of human milk is about 1032 (Simon). It is usually alkaline, sometimes neutral, but it gradually becomes acid. When it has stood for a time, the globtdes float to the surface forming a layer called cream, while beneath we have a bluish- white fluid, poorer in fat, but having a higher specific gravity than the upper stratum. If the temperature is cool, and the atmosphere not highly charged with electricity, milk will remain in its natural condition for several days ; but under reverse conditions, it spontaneously coagulates. This coagulation is caused by part of the milk sugar undergoing acid fermentation, yielding lactic acid, which precipitates the albuminous constituent of milk — the casein. /CisHaiOio + 2H,0 = 4 (C3H,03)\ The following are analyses of human milk, compared with that of a few other animals, in 1000 parts : * * Article " Millc," in Watt's Dictionary of Chemistry, vol. iii. PARTHENOGENESIS. 405 Constituents. Human— Yenwi& and BecquxrA. Human, 3d day after delivery— SiiMin. Cow— CheoaXlier and Henry. Asa — CkevalUer and Henry. Ewe— ChenaMer and Henry. Water . . . Sugar . . . Casein and extractives Butter . . Salts . . . Total, 889-08 43-64 39-24 26-66 1-38 828-0 700 40-0 50-0 3-1 870-2 in 44-8 313 6-0 916-5 60-8 18-2 1-1 3-4 856-2 ■ 50-0 45-0 42-0 6-8 1000-00 991-1 1000-0 1000-0 1000-0 It wiU be seen from the above table that ewe's milk is the richest of all milks, -while the milk of the ass is rich in sugar, but poor ia butter and casein. It will also be observed that human and cow's milk are, on the whole, much alike, and hence the last may be substituted for the first. The human milk examined by Simon soon after delivery was rich in sugar and fat, the amount of the latter being nearly double that found in ordinary milk. Vernois and Becquerel found in the ash of human milk 6-9 per cent, of calcium carbonate, 70-6 per cent, of calcium phosphate, 9-8 per cent, of sodium chloride, 7-4 per cent, of sodium sulphate, and 5 '3 per cent, of other salts. MUk is often adulterated with water, flour, brain-substance, almond emulsion, chalk, &c. These adulterations may be readily detected by microscopical examination. PARTHENOGENESIS. By parthenogenesis (from ^rx^hisia, virginity ; yinns, genera- tion) we understand the production of offspring, unlike their parents, which may take place without a true act of fecundation, that is, without at each birth, a necessary union of the male and female elements. This process had been previously called by Steenstrup, alternate generation. But many of the facts de- scribed under this term refer not so much to an alternate as to a continuous development. Thus, many insects spend part of their lives as a worm, and part as a moth. The moth produces . the worm, and the worm produces the moth ; but this is not an alternate, but a different phase of the same generation. So a 4o6 PARTHENOGENESIS. correct knowledge of the development of the Medusa aurita has shewn that what naturalists had considered to be four distinct animals are in fact only different stages in the development of one animal. The formation of the Aphis is especially alluded to by Steenstrup. Several of these insects are produced from the mother, and each may produce others, although it is only certain of them which become transformed into a fly. But the generation of a plant may be called alternate in the same sense as it is used in the case of the Medusa or the Aphis,, inas- much as the seed produces a root and a leaf -bud, which proceed to develop other leaves before they finally produce flowers with seed like that from which the plant originated. The term parthenogenesis, therefore, proposed by Owen, is the more correct one, and the following are examples of this process : 1. The development of the Tape Worm, Sc. — The researches of Helminthologists, but especially of Siebold, Van Beneden,, Dujardin, Steenstnip, and Blanchard, have cleared away the mystery which has so long hung over the origin of tape worms and other entozoa. It seems now determined that tape worms are only further stages of development of cysticerci, as flukes are only further stages in growth of certain cercariae. Professor Siebold first pointed out that the cysticercus fdsaio- laris found in the liver of the mouse, reaches its ultimate stage of development in the intestines of the cat, and is there trans- formed into the toenia, crassicollis. This fact was confirmed by a careful series of observations made by Dr Henry Nelson, who, in his thesis presented to the University of Edinburgh in 1850, carefully traces and figures all the various stages which the tape worm of the cat passes through. Each joint of this worm is estimated to contain 125,000 ova, which gives for the entire animal about 12,500,000., These minute bodies pass off by the faeces in itioalculable numbers, and enter into the body of the mouse, mixed with its food or drink, or by licking its furry coat, to which they adhere. JFrom the alimentary canal of the mouse they may enter the liver of that animal in three ways — Ist^ They may ascend the bile ducts. 2d. They may pass through the, coats of the intestine, and penetrate the adjoining portion of the liver., 3d. They may bore their way into one of the mesenteric veins, and be carried by the blood along the vena porta to the liver. Dr Nelson considers the latter to be the most correct view, as he shews that the ova are furnished DEVELOPMENT OF TAPE WORM. 407 ■with temporary teeth, which, enable them to pierce the tissues. That they do not perforate the intestine, and so get into the liver, is shewn by the fact that they are most developed on the surface of that organ, and least so in its interior. Neither are they found especially in the biliary ducts, like the distomata. Hence the blood seems to be the channel of their introduction, an idea stiU further supported by facts, the number of which is rapidly augmenting, demonstrating entozoa in various stages of development existing in the blood itself^ Arrived at the liver, these ova are transformed into oysttcerci fasaiola/res, and would never proceed further in development in the mouse, but being eaten by the cat, they become tape worms, and are transformed into tcenwe crassicoUes. This series of observations renders it probable that all the . various kinds of toenia are only advanced stages of development of different cysticerci. Dr Nelson points out that " the head of the cysticercvs cellidosce resembles in every respect that of the toenia soliwm of man. The, two figures given by Bremser are identical, if we allow for the stretching of the neck in the latter. Both have a double circle of hooks ; and although the toenia soliv/m is sometimes found without any teeth, Bremser has fully proved that this is the result of age, and not the original condition. He also observed, that as the worm increased in age, one row of the double corona first fell oflf, ajid was after a time followed by the other, leaving the worm thus unarmed." Besides, man feeds on animals in which these cysticerci are common, especially on the pig and sheep ; and it has been observed that in countries where meat is often eaten raw, as in Abyssinnia, tape worms are very common. JThe reason of the rare occurrence of toenia in civilised countrijes is^pro'bably Wiyg to the cooking of food, which destroys the vitality of the oysticerci.^ 'j^ Occasionally, however, it may easily be ooriceivedvthjit, (jwing to ' ; meat being very underdone, or to the teaacity of life in certain of these creatures (many of them resist a high teniperature with- out injury), they may escape the action of the teeth, arrive 1 ( > living in the human stomach, and l?e( Cotfviet'tfed into young toenia. 1 These ideas with regard to the origiiyof tape worms have < been converted into certainties by the experiments of Dr Kiich- enmeister.* He fed dogs and cats upon parts of animals which * Prague. Viertdjahrtchrifi, Band i. 1852, p. 126. 4o8 PARTHENOGENESIS. contained different kinds of eysticerci, and subsequently found the tape -worms into ■which these had been transformed present- ing various stages of development, according as the life of the animal which had eaten the eysticerci was more or less prolonged afterwards. Every precaution seems to have been used in these experiments, one of which may be cited. An old dog, during a period of from six to eight weeks, was frequently purged with castor oU, so as to prevent the possibility of tape worms being present. On the 18th of March 1851, he ate food containing ten eysticerci. On the 25th, he ate as many more, and on the 1st of AprU several others which were not numbered. On the 10th of April the dog was killed, and thirty-five tosnia were found in the intestines, of which five were from 124 to 390 millimetres (from about 5 to 15 inches) in length, and possessed from 130 to 160 joints. There were six others from 25 to 96 millimetres , (1 to 5 inches) in length, having from 40 to 60 joints. There were twenty-one others which measured from 8 to 16 milli- metres (J to \ an inch) in length, in which the joints were so indistinct that they could not be counted. Lastly, there were three measuring from 4 to 5 millimetres (l-6th of an inch) in length, in which the joints could scarcely be distinguished. Considering the power of contraction and elongation possessed by these worms, their length was not so decided a character of their stage of development, as the size pf the Head and hooks, which corresponded to the three periods in which the eysticerci had been swallowed. On feeding dogs upon the liver of the mouse, containing the C fa soiola/ns , Dr Kuchenmeister never found toenia in the intes^mesTTBttt when he fed cats on the same liver, the intes- tines contained the ttenia, crasdcollis. This observation indicates that not only are^' certain- eysticerci transformed into certain tcenia, ]iut itljat .the farmer require certain habitats, or peculiar animals in order to undergo this transformation. Although the present amotfnt of our knowledge does not enable us to state from what kinds of eysticerci many species of toenia are formed, it seems toletaWly- oertain from the observations of Siebold, Nelson, and Kuchenmeister that the Cysticercus fasdola/ris of the mouse is transformed into the Toenia crassicoUis of the cat ; the \% " After the dust hasj^een prepared in the manner described, r~ aj^ took a portion of it from the watch-glass, and diluted it with a solution of potash, consisting of 5 parts of potash in 100 of water. As soon as I perceived a globule evidently organised under the microscope, I drew it. This is how figure 4 was drawn."* This description leaves it uncertain whether an exact copy was taken of any portion of the field (4 the micro- scope, and, therefore, whether the figure represents the exact number of corpuscles present, and their relation to each other. . It only gives their form. But, assuming that the same kind of demonstration was made in each case, we have the relative numbers of these bodies taken from the gun-cotton in Fig. 1- Fig. 2 is another demonstration of the same after the addition of an aqueous solution of iodine. Fig. 3 represents the organised corpuscles associated with amorphous particles obtained on the 25th and 26th of June 1860. Fig. 4, the dust of an intense fog in the month of February 1861. In all these demonstrations he admits the organised corpuscles are comparatively scarce, because, he observes (p. 31), it is frequently necessary to change the field in order to see one of them, whilst at other times several could be seen together. ' M. Pasteur thinks that these drawings indicate the number of organised corpuscles that may be arrested in a small mass of * Annales des Sciences NaturelleSj 4me serie, torn. xri. p. '25. 1 428 HETEROGENESIS. cotton through which 1500 litres of air, in one of the les frequented streets of Paris, have passed in twenty-four houi about three or four yards from the ground. These he estimat at several millions in a litre (p. 29). .1 Now, it must be remembered that M. Pasteur is a chemii ^jand it will be admitted by every histologist that no methi (could be more unsatisfactory for determining either the natu )or the number of the corpuscles than the one he adopted. T] solution of the cotton in ether, the frequent soakings in wat« the desiccation, and then the addition of a solution of potas must completely alter the character of any living corpuscl in the atmosphere. Then the forms he assumes to be organ are not necessarily so. They are exceedingly freqtient amoi mineral substances, and siliceous rounded forms are commo which, of course, resist sulphuric acid. Natwe of dust. — Numerous investigations have been mad both before and since M. Pasteur wrote, to determine the natu of dust floating in the atmosphere — of that dust, for examp] which a ray of sunlight reveals to us, when admitted intp chamber. It consists, for the most part, of different kinds , starch corpuscles ; the debris of clothing, especially filaments cotton, silk, and wool ; the results of different kinds of combu tion, whether of coal or of wood ; various mineral bodies, globuli or ovoid, aAorphous or crystalline ; and minute fragments insects and vegetables ; very rarely small seeds and microsoof animalcules. These constituents vary to such an extent in different loca a\ ing, to a temperature of 300° centigrade for several hour \^ animal and yegetable microscopic organisms were found in tl fluid * S W In the same manner, air and infusions exposed to inteni cold still produce animalcules, but, according to Pasteur, not-i readily. Twenty flasks containing boiled infusions, and fro: which the aix was expelled, were opened by him with excessii precaution on the Mer de Glace at Montanvert on the Jur Notwithstanding the purity and extreme coldness of the ai infusoria appeared in five of his flasks. As an illustration of the manner in which the controversy c this subject has been carried on in the Academy of Scienc in Paris, I may give a short account of that portion of referring to the Glacier experiments. M.M. Pouchet, JoU and Muaset opened eight similar flasks used by M. Pasteur i Monta,nvert, on the Glacier of the Maladetta, in the Spanii Pyrenees, 9000 feet above the sea, and 3000 feet higher ths that of Montanvert, using all the precautions required by 1 Pasteur. In addition, before cutting off the ends of the _ . hermetically sealed tubes with a file, prev iously heated by ___lamp, they held the flasks above their headgj Notwithstandin a-Tg infusoria appeared in all the infusions a few days afterwards.- J To this communication, presented to the Academy, Sept. 2 1863, M. Pasteur replies, Nov. 2, J saying that he is rejoicf that his learned adversaries have gone to such an altitude repeat his experiments ; but observes that they did not tal the necessary precautions. They only had eight flasks, where he had twenty ; they shook their flasks before opening thei which he took care not to do ; and they had the imprudence use a file, instead of a pair of pincers with long branches, heati in the flame of a lamp. He says that the thumb and finge holding the file were too near the opening into the flask, ai may have conveyed germs there, especially as they were n passed through the flame, as the file was.§ He defies them, they take sufficient precautions, to obtain infusoria in all the flasks. {'I MM. Jolly and Musset accept the defiance of M. Paster * Bastian : The Modes of Origin of Lowest Organisms, 1871. t Comptes Rendus, torn. Ivii. p. 658. % Ibid. p. 724. i Ibid. p. 725. \ Ibid. p. 726. CHEMICAL EXPERIMENTS. ■ 437 Nov. 16 * and, iu fact, on the 13th Jiine following, they send a memoir to the Academy, stating that they had returned to the Maladetta, this time with twenty-two flasks — that is two more than were used hy M. Pasteur— fulfilled all his conditions, not forgetting the pincers with long branches, properly heated, and found that infusoria appeared in every flask without exception in four days ;t and so ended this part of the controversy. Numerous other important questions have been debated before the Academy. Among these are the changes which take place in the air confined in the flasks, founded on numerous analyses ;J the observations of JoUy and Musset with regard to vibrios living in distilled water ; § the statement by M. Pasteur that neither free oxygen nor atmospheric air are necessairy for the growth of infusoria, 1 1 and that they will develop themselves in carbonic acid gas only. Lastly, the same chemist declares that, notwithstanding his often declared opinion that ferments are living beings and not dead matter, he can produce fermen- tation with the ashes of yeast. IT Some of these statements are confirmed by Donn^,** who found that hens' eggs became putrid without the formation of vibrios or other infusoria. This observation, while it might serve to prove that atmospheric air passing through the egg-shell separated the germs by filtration, is whoUy opposed to the idea that putrefaction is necessarily caused by such germs. The only conclusion I can draw from the numerous contra- dictory and ingenious communicationspresented to the Academ y " C of Sciences on this matter is, that fiot the slightest proof is • Si^ given by the chemists, with M. Pasteur at their head, that fermentation and putrefaction are necessarily dependent on living germs existing in the atmosphere. They rather tend to shew that these are phenomena of a chemical nature, as was ably maintained by Liebig-ft Did we, indeed,confine our read- ing to the papers of M. Pasteur — that is, to one side of the case — we could easily persuade ourselves of his correctness ; JJ * Comptes Eendus, torn. IvU. pp. 842-845. t Ibid. M. p. 1122. ' X Ibid. pp. 734-739. § Ibid. Iv. p. 491. II Ibid. li. pp. 346, 346 ; lir. p. 267 ; Ivi. p. 1191. \ Ibid. Ivi. pp. 418, 419. ** Ibid. Iviii. pp. 961, 952 ; Ixv. p. 602. •ft Letters on Chemistry, letters xviii. and xix. \\ This is what unfortunately seems to have been done by the Commission of the Academy, which made a report on this subject, Feb. 20. 1866 (Comptes Eendus, torn. xl. p. 884). Ko histologist was on the Commission, which refused to enter » 'S*! VI t^ 438 HETEROGENESIS. but every one of his experiments has been repeated by seve independent investigators, who have shewn his imagined pre as to the existence of atmospheric germs to be altoget erroneous. We may conclude, therefore, that living germs not necessarily the cause of putrefaction and fermentati neither is it necessary to believe that ferments are living all — they' may be dead. This, if not admitted, seems to implied by Pasteur himself, who tells us he can now exi these processes, not by fresh yeast, only, but by the ashes yeast.* That they may be induced by dead organic ma1 which has been subjected to a direct temperature of 150' 200° centigr.ade— a heat utterly incompatible with the existe of life-;— we have seen to have been proved by Pouchet, Jo Musset, and others. The. idea that these imaginary germs were the cause of pui faction, of disease, of blights among vegetables, and other ev originated with Kircher and the pathologists of the seventee century. It has been frequently revived, but always shewi be erroneous. JTjdl 1852, cholera was supposed to be oceasioa "By.a fungus that really existed in the dejections, buit which i/ Bus^ointed out was the wedo segetum of diseased wheat, wi entered the body in the form of bread. Certain well-kno parasitic diseases are spread by contact, such as scabies, wh as it depends upon an insect burrowing in the skin, maj understood to crawl from one person to another. I succeec in 1841, in proving that Favus might be made to grow on ' eased surfaces of otherwise healthy persons ; but many of unquestionably infectious diseases, such as smallpox, scarlat measles, and typhus, have no such origin. It has been attemj to be shewn, indeed, by Lemaire,f that in the conder vapours of hospitals and other putrid localities," vibrios i be found ; but that vibrios' are the cause of these various eases, is not only not^royed, but from what has been statec ■ — ^'"g^V ^Tn]T robable. \ We have previously alluded to the m 33^ cules which, according to some, convey some of these poisi (See p. 104.) What, then, it may be asked, is the origin of the infuse upon any kind of microscopical inquiry j Messrs Pouchet, Jolly, and Mu under such circumstances, very properly took no part In the investigation, wI consequently, was altogether one-sided, and of no scientific value. , * Comptes Bendus, tom. Ivi. pp. 418, 419. t ^^- toi". 1"^ PP. 317-4: /^' 319 EXAMPLES OF HETEROGENESIS. 439 vegetable and animal, that we find in organic fluids during fermentation and putrefaction? In answer to this question; I say they originate in oleo-albuminous molecules, which are formed in organic fluids, and which, floating to the surface, form the peUicle or proligerous matter. There, under the influence of certain conditions, such as temperature, light, chemical exchanges, density, pressure, and composition of atmo- spheric air, and of the fluid, &c., the molecules, by their coales- cence, produce the lower forms of vegetable and animal Ufe. Other researches may be referred to as confirming these con- clusions, such as — 1. The development of Botrytis Bassiana in Muscardine, a disease of silk worms. — The true cause of this disease was first ascertained by Bassi in 1835, who shewed that it depended on the presence of a fungus which developed and multiplied within the body of the worm or moth, caused its death, and appeared through the skin in many places as a whitish growth. M. Gu&in-M&eville* has observed the development of the fungus filaments from the blood corpuscles of the worm. A similar disease occurs in the house fly in autumn, and is said by Cohn to depend on a mould called Empusa, which also originates from the blood cells.t 2. The d'Bvelopment of PenicfUMv/m from milk globules. — ^This was first described by Turpin in 1837.| When a drop of milk is examined after it has acquired an acid reaction, flakes of casein will be found along with bacteria and milk globules variously altered. These milk globules throw off buds from their margin, which grow into mycelium-like filaments, and soon the mUk is covered with a whitish mildew, seen with the naked eye. 3. The development of Bacteria within the latioiferoits vessels of plamts. — M. Trecul, a distinguished French botanist, has found numerous minute bodies, of a globular or cylindrical form, some motionless, others shewing slight undulating move- ments, within the laticiferous vessels of Apocynwm cannahinvm,, in the closed medullary ceUs of the Ficvs carica, and in the fibre cells of the bark of various plants, such as Asolepias comuti, the conmion elder, &c. &c.§ He believes these living bodies, « Comptes Rendus, torn., Ivi., p. 674. t Hedwigia, 1866, p. 69. J Turpin, Ann. des So. Nat., 1837 (Zoologie), torn, viii., p. 349. - J Comptes Kendus (1866), torn. Ixi., pp. 168,-.432, and 436. 440 HETEROGENESIS. to which he gives the name of Amyldbacteria, are derived from metamorphosed starchy matter, hence their name. 4. The occwrence of Bacteria, Fv/ngi, Sc, in the centre of the organs of dead animals or in the closed cavities of the body. — Nothing is more common than to find these organisms in the centre of the brain, in the centre of the liver, even in the hepatic cells, in epithelium cells, or in any part of a dead or even a living body undergoing putrefaction. Berkeley has found a yellow mould within the cerebral cavity of golden pheasants.* jMurie has seen fungus-growths within the abdomino-pleural jmembrane of a kittiwake gull, of a great white-crested cockatoo, and of a rough-legged buzzard.t Bacteria and fungi have often been found ia eggs. Helmarecht found spores in the aqueous humour of the human eye.} Numerous other examples might be given, but enough has been brought forward to shew that f 9reign living organisms have originated in situations entirely removed from the air. ABNORMAI. BBPRODIICTION. This consists in the various alterations which may occur in the different stages of the generative functions, and include, — 1st, Diseases which arrest or modify ovulation ; 2d, Diseases, nutritive or nervous, which impede fecundation, and occasion barrenness in the female, or impotence in the male ; 3d, Diseases of the embryo, causing various kinds of monsters, from arrest or excess of development in oue or more of its parts. This last subject is now generally studied under the name of teratology {rif"!, monster), and has in recent times beeonie a very extensive one. Congenital malformations of the foetus were formerly considered as indicative of some misfortune, — as the effect of witchcraft, or as offsprings of the evil spirit. They are now not only recognised to originate in natural derangements of embry- onal development, but the laws which govern such derangements have to a great extent been determined. From these it ha9 become evident that monstrosities are not the result of chance, but are always induced by alterations in the known processes which regulate reproduction, and the evolution of the ovum and its contents. Hence in this, as in every other disordered con- dition, the real source of the abnormaKty is to be sought for, * Berkeley, Introduction to Cryptogamic Botany, p. 260. t Murie, Beport of British Association, 1871. J Robin's " Veg€taux Parasites," 1853, p 370. ON DEATH. 441 aot only in the investigation of that condition itself, but in the kno-wledge, first, of the healthy or physiological state ; and secondly, of the manner in which it has become deranged. In all our inquiries, it must be apparent that disease is morbid physiology ; and such is the aspect in which we have endeavoured to place it before the reader. ON BEATS. Death is the permanent cessation of those properties and functions which constitute life. In this wide sense, it must be apparent that the textures are continually dying, in the same manner that they are continually being generated. What we have described as the secondary digestion essentially consists in the removal of the particles of the body which have been worn out, — fulfilled their functions, and died. Thus, death is mole- cular, cellular, fibrous, or tubular, in proportion as these various organic elements become degenerated, and disappear to make way for others which enjoy activity or life, and in their turn die, enter into new chemical combinations, and are excreted like their predecessors. In the more common acceptation of the term, however, death may be considered as partial or gen&ral. Partial death of the animal body is caused by those diseases or injuries which produce mortification and ulceration in soft, and necrosis and caries in the hard parts, to a greater or less extent. Of this we have already spoken, and therefore need only treat of general death of the system. This has been variously conr sidered as natural or v/imatwal ; by the former meaniog death from old age or gradual decay, and by the latter, death from diseases or violence. In this latter case, death may be gradual or sudden, and be induced by a great variety of agents. It may be said, however, that all the modes of death are reducible to three, viz. : 1st, Death by syncope — that is, beginniog at the heart ; 2d, Death by asphyxia, beginning at the lungs ; and 3d, Death by coma, beginning at the brain. Death by syncope. — ^All causes which arrest the action of the heart occasion stoppage of the circulation ; a circumstance which interferes with the due performance of the vital func- tions ; and death is the consequence. It may occur through the nervous system, through feebleness of the muscular walls of the heart itself, or through loss of blood. As examples of the first 442 ON DEATH. method of causing syncope, may be cited concussion, or all sudden shocks to the system — as from violent hlows or injuries, extensive lesions, violent mental emotions, a stroke of lightning, exposure to the sun (or cowp de soleiT), and certain poisons which, acting especially on nerves going to the heart, paralyse its rhythmical motions, as aconite, digitalis, &c. Syncope, from feebleness of the muscular walls is illustrated from the effects of long-continued violent exertion, starvation, and disease of its textures, especially that now recognised as fatty degeneration, one of the most common causes of sudden death. Lastly, ex- cessive loss of blood, whether from direct external injury to a large vessel, sudden bursting of an internal vascular tumour or aneurism, disease of the coats of an artery or vein leading to sudden or to long-continued loss of blood, are among the fre- quent causes of syncope. Death hy asphyxia. — This is produced by all causes which in- terrupt the act of respiration, or the access of oxygen, so necessary for carrying on the nutritive functions, and has been previously referred to (p.. 233). It is now ascertained that mere obstruc- tion of air does not immediately act upon the heart, which not only continues to contract for a time, but even sends venous blood through the arterial system. From the numerous inves- tigations which have been made to determine in what manner the vital actions are arrested in asphyxia, it would appear that at first non-aerated or venous blood passes freely through the lungs to the heart, from whence it goes to all parts of the system. It operates on the brain, however, as a poison, rapidly suspending the sensorial functions. The capillaries of the lung next refuse to transmit non-oxygenated blood, in consequence of which it is not returned to the right side of the heart, and thus the vital actions cease. These effects are produced with greater or less rapidity, according as the occlusion of air is more perfect, as in cases of drowning and strangulation. In diseases of the heart and lungs, the same results are produced more slowly. The only poisons which operate upon the lungs directly causing asphyxia are certain so-called poisonous gases, such as carbonic acid gas, the fatal effects of which, however, are not so much to be ascribed to any noxious properties it possesses as to the absence of free oxygen. Death by coma. — This is caused by aU circumstances which suspend the sensorial functions by first operating on the brain. ON DEATH. ' 443 We observe it produced from the long-continued action of cold, from the influence of narcotic poisons, especially - opium and chloroform, and from such injuries of the brain, from without or -within, as are not necessarily connected with shock. If a violent blow be given to the head of an animal, it may be observed to suffer from shock or syncope ; the heart flutters, and the pulse is weak. , But if it recover from this, the heart's action may be restored, while sensation is suspended, and it dies comatose. If shock be avoided during the operation, the brain of an animal may be removed, producing coma or stupe- faction, which will ultimately kill, although for some time the circulation and respiration continue. In apoplexies, fevers, and other diseases, similar effects are observable. ' It should not be overlooked that death in many cases is produced by a conjunction, or by the rapidly-following results of two or all three of these modes. Thus, chloroform may kill from the conjoined stupefying action on the brain, as well as from difliculty of respiration. Coma, from pressure on the brain, may, by' influencing the medvlla oblongata, affect the pneumo-gastric nerves, which send branches to the heart and lungs. In this case, death is the most rapid — occurring in all three ways. Hence the humane effort of the hangman not only to produce strangulation, but by dislocatioii of the bones of the neck, to crush the upper part of the spinal cord. The preceding observations evidently indicate that, in our endeavours to produce recovery from either of these states, much wiE depend upon the correct information we derive as to the causes producing them. In syncope, our efforts wiU be directed to restore the action of the heart by stimuli, a proper position, checking haemorrhage, &c. ; in asphyxia, to reproduce respiration ; and in coma, to remove any cause which, by pres- sure on the brain from without or within, interferes with its functions. . PART III. PRACTICAL PHYSIOLOGY. Bt the term " practical," is not understood giving lectures on practical as distinguished from theoretical subjects. "What I understand by it is causing the student himself to perform -with appropriate instruments the necessary investigations, so that he may learn the art of observation, and obtain the necessary manual dexterity for arriving at exact results. Thus, practical chemical physiology consists not in being shewn by the teacher, how to analyse the various fluids and solids of the animal frame, but in his doing this himself. Practical histological physiology is not merely examining objects and preparationlEl, but in causing the student to manipulate the microscope, demonstrate for himseK, and describe what he sees. Practical experimental physiology, in like manner, consists not only in witnessing, but taking part in, the performance of experiments • on animals, with all the modem instruments of precision that science in recent times has placed in our hands. PRACTICAL PHYSIOLOGICAL CHEMISTRY. Practical physiological chemistry includes an examination of the solids and fluids of the body. The physical properties of the substance, such as form, colour, hardness, specific gravity, GENERAL EXAMINA TION OF ANIMAL FL UID. 445 &e., must first be accurately observed. It is then siibjected to chemical analysis, either quantitative or qualitative, and a syste- matic mode of procedure followed. I. GENERAL QUALITATIVE EXAMINATION OF AN ANIMAL FLUID. The examination should be made in the following order : — 1. Heaction to test paper. — The tests used are blue litmus paper, which becomes red when dipped in an acid fluid, and red litmus, which turns blue, or yellow turmeric paper, which becomes brown when immersed in an alkaline fluid. An acid reaction of a liquid indicates the presence of free acids or of acid salts, whereas an alkaline reaction is produced by free alkalies, alkaline phosphates, or carbonates. If an alkaline reaction disappear on gently heating the paper over the flame of a spirit lamp, it informs us that the alkali is volatile ; if it remain, the alkali is fixed. 2. Filter,- or strain. — A fine, white, thin blotting paper is the best filtering medium for ordinary purposes. When the liquid passes through the paper turbid, it should be returned once or twice to the filter till it comes through clear. The precipitate should be preserved by being scraped off with a spatula of ivory, platinum, or steel, or it may be washed off with a gentle stream of water from an ordinary wash bottle. Sometimes it is necessary to strain through one or several folds of muslin or cotton. 3. Heat a portion of the filtrate. — This should be done in a test tube over a spirit lamp. If no precipitate is formed, albumin is absent. If a precipitate appear, it may be albimiin or phosphates. Add a few drops of dilute hydrochloric or nitric acid. If the precipitate disappear, albwnin is absent (p. 8), but earthy phosphates may be there (p. 28). These must be looked for and isolated by special tests. 4. Add to the flaid a solution of Ferrocyanide of Potassium. — If there be no precipitate, casein and globulin are absent. If a precipitate fall, take a fresh portion of fluid and divide into two parts. To one add a solution of chloride of calcium and apply heat. A precipitate indicates casein (p. 9). Carefully neutralise the other portion, — if acid, with an alkali, if alkaline, with a few drops of acid, — and observe whether a precipitate be 446 PRACTICAL PHYSIOLOGICAL CHEMISTRY. formed at the point of neutralisation. If a precipitate appear, glohuUn is present (p. 10). ' 5. To a portion of the liquid add acetic add. — A precipitate may be formed. If so, it is chondrin, mucus, or pyim. To a portion add a solution of common alum or sulphate of copper. If a precipitate fall, soluble in excess of the reagent, chondrin is present (p. 11). To another part add a solution of corrosive sublimate, and if there be a precipitate, we have pyin, or mucin (p. 11). Neutral acetate of lead distinguishes the two, giving a copious precipitate with pyin and a very slight turbidity, or none at all, with mucin. 6. Evaporate a feio ounces of the liquid to one-sixth of its hdJe. — If a jelly form on cooling, we have chond/nn,OTC gelaUn (p. 10). For the mode of distinguishing chondrin see last paragraph.' If there be a precipitate, it may be wates, phosphates, sulphates, allantoin, tyrosin, hippwrate of calcium,, or benzoic acid. These must be examiued microscopically, and by special tests, to be afterwards described. , 7. Evaporate a few ounces to a syrup, and allow it to stand for forty-eight hows. — If crystals form, allow the fluid to stand as long as they increase. Such crystals may be creatin {^. 18), Creatinin (p. 18), leuoin (p. 17), allantoin (p. 16), tavrin ($. 16), sarcin (p. 16), inosite (p. 27), hippwates of potash or soda (p. 15), sodium, chloride, and other salts (p. 28). The next point to determine is, do the crystals consist of organic or inorganic matter. Heat a small portion on a clean bit of platinum foil. If it blacken when strongly heated, organic matter is present. If a whitish-coloured residue be left, after heating strongly, it consists of inorganic matter ; and the probability is we have an organic acid united with an inorganic base. If the crystals con- sist solely of organic matter, they must be examined by pro- cesses of organic analysis for nitrogen, sulphur, and phosphorus, and their chemical composition determined. The tests for these substances will be given when we treat of special fluids and solids. 8. Separate the crystals from the syrup, and exhaust the residue with alcohol of specific gravity 0'833. — Treat as follows : Divide Alcoholic Solution into Six Portions. 1. Concentrate, dilute with water, place a few drops on a porcelain plate, and add a drop of nitric acid, irtay of colours indicates ...... Bilepigmmt (p. 32). ANALYSIS OF BLOOD. H7 2. Concentrate, dilute with water, place in a test tube, add i bulk of syrup, then allow a drop or two of sulphuric acid to flow down side of test tube. Play of colours at junction of fluid and syrup indicates Bile acids (p. 12). 3. Evaporate to dryness, dissolve in water. Apply the tests for sugar according to methods to be afterwards described ..." Sugar {p. 25). 4. Evaporate to a small bulk, add nitric acid ; laminar crystals of nitrate of urea separate out — vindicating Urea (p. 14). 5. Mix with a very strong solution of chloride of zinc. A crystalline precipitate indicates . . . Creatim and (p. 18). 6. Heat with oxide of zinc, filter while hot, and evaporate a drop on a glass sUde. Club-shaped crystals of lactate of zinc indicate Lactic Acid (P- 27). 9. Evaporate part of original Jbdd to clryness, pound the residue in a mortwr, and exhomst vrith ether. — This etherial extract con- taining fats in solution, is evaporated and fui-fclier examined. ' 10. Incineration. — The residue insoluble in ether is inciner- ated in a platinum capsule, and the ash examined by the ordinary methods of inorganic analysis. General Conclusion. — By these ten processes we ascertain: whether the fluid be acid, alkaline, or neutral, and whether it contain albuminates, albuminoids, or albuminous deriyatives. We also obtain a knowledge of the presence of fatty matters oc mineral principles. II. QUALITATIVE AND QUANTITATIVE ANALYSIS OF SPECIAL ANIMAL FLUIDS. The fluids we specially examine are — (1.) The blood; (2.) The chi/le ; (3.) The lymph ; (4.) The saliva ; (5.) The gastric juice ; (6.) The pancreatic juice ; (7.) The hUc ; (8.) The wrin^ ; (9.) The sweat. Under this head we may also describe the analysis of (10.) Th& foeces. Analysis of Blood. For the chemical constitution of the blood, see pp. 239, 240. The analysis is conducted in the following manner. The re- action is usually slightly alkaline. 448 PRACTICAL PHYSIOLOGICAL CHEMISTRY. 1. Water. — Weigh out a certain definite quantity, evaporate in a porcelain basin over a water bath, and dry the residue in a hot air chamber, at a temperature between 120° and 130° C. Weigh again. The loss in weight will represent the water. 2. Fibrin. — Eeceive an ounce or two of the blood into a glass vessel as it flows from a vein, stir it up for ten minutes with a glass rod or twig of birch till the fibrin is separated. The blood, with the fibrin, is then weighed, and strained through auslin to separate the fibrin, which is well washed with water, dried, and boiled with alcohol and ether to free it from fat. The alcohol and ether are driven off by evaporation, the fibrin is dried at 120° C, and again weighed. The weight indicates the amount of fibrin in the portion of blood examined. 3. Albwmin and substances coagulated by heat. — A few oimces by weight of blood are acidulated with acetic acid, and added drop by drop to boiling water. The aqueous liquid is then poured upon a carefully weighed filter, and the coagulum separated. The coagulum is then washed on the filter with boiling water, and dried at 120° C. It is then weighed, the weight of the fibrin deducted, and the balance represents albumin, and a small amount of certain other substances coagulable by heat. 4. Fat. — A weighed quantity of blood is dried at 100° C, and treated with ether. The etherial solution is filtered into a platinum capsule, in which it is slowly evaporated, and the residue dried at 100°. The weight of residue gives the amount of fatty matter. 5. Fixtractive matter and mineral constituents. — The filtrate obtained in the estimation of the albumin is evaporated oq a water bath, and the residue dried and weighed. It is then burnt at as low a temperature as possible. An ash is left, which consists of mineral constituents. The weight of this ash is deducted from the weight of the dried residue, and the difference is the extractive matter., The mineral matter may also be obtained by the process of dialysis (p. 118). 6. Mineral matter. — A quantity of the blobd is weighed, mixed with ignited carbonate of soda, dried and burnt at as low a temperature as possible. The residue is the ash. The incineration must be done with great care, as the chlorides of potassium and sodium volatilise at a high temperature ; phos- phates may be decomposed, and sulphates reduced to sulphides. . The ash is then treated as follows : ANALYSIS OF BLOOD. 449 Divide into Two Pabts. First portion — Treat with dilute nitric acid ; add nitrate of silver to precipitate the chlorine as chloride of silver Chloridei. Second portion— Treat with dilute hydrochloric acid. Divide into three portions. 1. Add chloride of barium to precipitate sulphuric oid as sulphate of barium . . . Sulphwic 2. Mix with ammonia and a little acetic acid — - acid. (1.) Add oxalate of ammonia to throw down lime as oxalate of lime ... Idme. (2.) Add excess of ammonia to throw down all the magnesia and part of the phosphoric acid pho^horic add. (3.) Add sulphate of magnesia to throw down the rest of the phosphoric acid . . Phosphm-ic acid. 3. Add a little oxalic acid to throw down the Ume, and also a few drops of ammonia, and phosphate of ammonia, to throw down the magnesia. Filter. Dry the residue, and dissolve in hydro- chloric acid. Add tetrachloride of platinum, which throws down all the potassium as a yellow crystalline precipitate. In the fluid, on evaporation, will be found the sodium salt , Potassium and Sodium. 7. Serum and coagvlvm,. — A certain amount of blood is aUowed to stand in a vessel till all the clot has separated. The clot is then carefully detached by a needle or sharp knife from the side of the vessel. The blood is weighed, and after the clot has contracted as much as possible, the serum is pouted off. The clot is dried by means of blotting paper and again weighed. If ■we deduct the weight of the clot from the total weight of the blood, we find the proportion of serum. 8. The colovring matter of the blood, Hxm^glohin, Hoemata- gldbin, or Hoematoarystcdlm. — (See p. 31, and Plate I. figs. 20 and 22.) Take a few ounces of blood, beat with a twig of birch for a quarter of an hour to separate the fibrin, strain through a linen cloth along with a mixture consisting of one volume of a saturated solution of sodium chloride and nine volumes of dis- tilled water. A precipitate is formed, which is shaken up with a little water and from four to ten times its volume of ether. 4SO PRACTICAL PHYSIOLOGICAL CHEMISTRY. The ether is drawn oflf with a pipette after several hours, and is found to contain cholestrin. An aqueous solution of the residue is now brought to a low temperature, and a pulpy mass forms consisting of crystals of hsemoglohin. 9. Estimation of Iron. —This may be readil}' done by burning the hsemoglobin obtained by the process just described. When haemoglobin is burnt, a small residue of ferric oxide is left, from the weight of which the amount of iron is then calculated (every 100 parts of ferric oxide containing 70 parts of iron). 10. The optical properties of Haemoglobin. — These may now be examined according to the method and optical principles described at pp. 32 and 138. For this purpose we require an instrument termed a, spectroscope, of which there are two principal -varieties, the ordinary spectroscope and the micro- spectroscope. When there is a large quantity of blood available, as in most physiological experiments, the ordinary spectroscope should be employed, but when only a drop or two of blood can be obtained, we use a spectrum apparatus fitted to a microscope. The construction of a spectroscope depends on the optical principle that when a ray of sunlight, or a ray of white light from an artificial source, passes through a prism it splits up into a number of individual coloured rays, in the following order, running froni left to right — red, orange, yellow, green, blue, indigo, purple, and violet (p. 138). The ordinary instrument consists essentially of three parts : 1st, a tube having at the end an adjustable slit for admitting the light ; 2d, a prism made of flint glass, or a triangular glass bottle filled with Bisulphide of Carbon ; and 3d, a magnifying glass or telescope for increasing the apparent size of the spectrum. The tube of the telescope must be placed in a different direction to the tube carrying the slit, because the coloured rays forming the spectrum form an angle with the incident rays as they enter the prism.* When a thin layer of a liquid, such as arterial blood (which contains oxy- hsemoglobin, p. 32), is placed in front of the sht, the colouring matter intercepts certain coloured rays of the spectrum, so that two dark bands are seen between the yeljow and green of the ordinary spectrum. Tor this experiment the blood must be greatly diluted with water and a small test tube, or still better, a vessel having parallel sides of thin glass, filled with the solution, is placed before the slit. To increase the amount of light, it * Schellen, Spectrum Analysis. London, 1872. ANALYSIS OF BLOOD. 451 may be concentrated on the slit by means of a powerful bull's- eye condenser. The miorospectroscope of Sorby and Browning is a spectrum arrangement which can be applied to any microscope by fixing it in the place of the ordinary eyepiece, so that spectroscopic investigation Of an object can be pursued without any change in the manner of using the instrument. By means of this instrument the two absorption bands of arterial, and the single one of venous blood, can be readily recognised. Recently, W. Preyer* has applied the method of spectrum analysis to the determination of the quantity of haemoglobin. " The determination depends upon the fact that a concentrated solution of haemoglobin in a layer of certain thickness is opaque, even in strong, illumination, to all rays except the red, whereas less concentrated solutions in a layer of the same thickness give passage to other rays besides the red and orange, and especially to a portion of the green. If, therefore, a measured quantity of blood placed before the slit of the spectral apparatus be diluted with water till green light appears in the spectrum, and if the proportion of hemoglobin in a solution which ti^a^^s- mits the green under exactly similar circumstances has once for all been determined, it is easy to estimate the percentage of hsemoglobin in the blood under examination." f 11. Effkct of passing a stream of carbon moiwxide through blood. — When a stream of carbon monoxide is passed for some time through blood, and a little of this blood is examined by the spectroscope, the two absorption bands of oxy-hsemoglobin will be seen. Hoppe-Seyler of Strasburg has pointed out that these absorption bands do not disappear and give place to a single band on the addition of sulphide of ammonium even after several days, and he proposes this unalterability of blood containiug carbon monoxide by ammonium sulphide as a test for the presence of this gas in the blood. J 12. Detection of blood stains by the formation of Hoemin crys- tals. § — Sprinkle a few grains of common salt on the stain. After a few minutes add a few drops of glacial acetic acid. * Ann. Chem. Fharm. oxl., p. 187. t Watt's Dictionary of Chemistry. Supplement, p. 353. X Hoppe-Seyler, Zeitsehrift Anal. Chem, Ui. 439. Jabresb. 186S. p. 74S. ; Brttcke, Jabresb. 1857. P. 609. 4S2 PRACTICAL PHYSIOLOGICAL CHEMISTRY. Scrape off as much matter as possible from the stain, and place it on a glass-slide. If necessary to moisten still more, add another drop or two of glacial acetic acid. Then carefully put on a thin covering glass, and lay the slide aside for two hours in a moderately warm place, say four feet from an ordinary fire. At the end of this time, examine with a power of 250 diameters and the black crystals of hsemiu wiU be found. (Plate I. figs. 19 and 21.) 13. Chdacwm test for blood. — Another test for blood is given by tincture of guiacum. A drop of freshly prepared tincture is placed on a bit of white blotting-paper. A drop of any solution suspected of containing blood is added, and after- wards a drop or two of hydrogen dioxide (HjOg). If blood be present, the stain on the blotting-paper soon turns from green to blue. This, however, is not a test to be absolutely depended on, because saliva, gum arable, citrate of iron, &c., give the same reaction. As a negative test, however, it is valuable, because if the blue colour be not obtained, blood is certainly not present.* 14. Gases of the blood. — The method of L. Meyer for deter- mining the gases of the blood is as follows : — The blood is diluted with ten times its bulk of water, and the gases are col- lected by boOing the liquid in vacuo at a gentle heat. The/ree gases are thus obtained. A few crystals of tartaric acid are then added, the blood is again boiled, and the oombmed gas is liberated. The gases of the blood consist of oxygen, nitrogen, and carbonic acid. They are introduced into a special apparatus for the analysis of gases, f The carbonic acid is absorbed by caustic potash, and the amount thus determined. The amount of oxygen is found by exploding the mixture with an excess of hydrogen, and one-third of the total amount of contraction caused by the explosion is the quantity of oxygen present. To ascertain the nitrogen, all the other gases must be removed, and the residue consists of nitrogen. The gases may also be collected by means of an air pump, of which the best form for this pur- pose is the mercurial air pump of Sprengel.t * Van Been, Zeltschrift Anal. Chem. ii., p. 459. Taylor, Guy's Hospital Reports. 1868. t For details as to analysis of gases, see Watt's Dictionaiy of Chemistry, voL i. p. 268. J Quicksilber — Luftpumpen ; Miiller — Pouillet's Lehrbuch der Physik. I. Bd. s. 211 ; II. £d. s. 911. Also Dr WiUlner's Lebrbuch der Experimentalphysik. I. Bd. p. 365. , ANALYSIS OF CHYLE, LYMPH, AND SALIVA, 453 The serum Of blood has alao been found to contain sugar, urea, uric acid, creatine, creatinine, hippuric acid, hypoxanthin, leucin, and tyrosin, which substances exist only occasionally in very small quantity, and are difficult to isolate. Analysis of Chyle. This fluid must be obtained from the thoracic duct of an animal killed during digestion. It is an opalescent, milky liquid, having a saline taste and a very weak alkaline reaction. The specific gravity varies from 1012 to 1025. It may be analysed by pursuing the same method described for the blood. Numer- ous analyses made by Pelouge, Fr^my, Eees, Simon, and Nasse vary as to the relative proportions of its constituents. Analysis of Lymph. When obtained fresh from the lymphatic vessels, its reaction is usually alkaline. It soon coagulates, forming a jelly-like coa- gulum. The coagulum ■will be found to consist of a substance identical with fibrin. The fluid contains albumin, which may be readily separated by dropping into boiling water. A small amount of fat may be found by shaking up with ether. A very small amount of extractive matter may be taken up with alcohol. The salts are separated either by obtaining the ash, or by means of dialysis. They are found to consist of sodium chloride, alkaline carbonates, salts of ammonia, sulphates, and phosphates. Analysis of Saliva. This may be obtained by introducing a small sUver canula into either Stenson's or Wharton's duct, and may be examined according to the method already detailed (p. 445). The reaction is alkaline. Evaporation will yield the amount of solid residue. On allowing saliva to stand for some time in a beaker, it becomes opalescent or turbid, and bubbles of gas form on the surface. This is due to a deposition of calcium carbonate and the escape of carbonic acid. When a drop of saliva is placed on a porcelain lid, and a drop of Ferric chloride added, a blood red or yellowish red colour is obtained owing to the presence in saliva of sulpho- cyanide of potassium. Separation of ptyalm. — Dilute the saliva with dilute phos- phoric acid, add lime water, and thus obtain a precipitate containing phosphate of lime, ptyalin, and a small amount of 4S4 PRACTICAL PHYSIOLOGICAL CHEMISTRY. albumin. Shake tip with distilled water. The ptyalui is dis- solved and separated from the other two substances. This solution of ptyalin may be concentrated by evaporation, and its action on starch observed. Analysis of Gasteic Juice. This fluid may be collected by making in a dog a gastric fistula, into which a silver or gold canula, having a stop-cock, is introduced. The gastric juice is transparent, colourless, or slightly yellowish. It has a sourish odour. When obtained during fasting it is neutral or slightly alkaline, consisting chiefly of muc\is, but during the ingestion of food it is strongly acid (p. 203). Water. — This may be calculated by evaporating a given weight of gastric juice and weighing the residue. Deduct this weight from that of the gastric juice, and the difference yields the weight of water. Prepwration of pepsin. — Add alcohol, which precipitates the pepsin. Evaporate and pepsin is obtained, the properties of which should be examined as follows: — Dissolve in warm water. Divide into five portions, and treat as follows : • ' 1. Add solution of corrosive sublimate. ^ 2. Add protoohloride of tin. f ^^^^^ precipitate of pepsin, 3. Add basic acetate of lead. I jt jr 4. Add tannic acid. ) 5. Add a few drops of hydrooMorio or lactic acids, tlen several pieces of minced meat, and lay aside in a warm place (100° F.) for four hours. The meat will then be found soft, whitish in colour, and partially digested. Acid of the juice. — Great differences of opinion have prevailed as to this point, Bernard * and others asserting that no hydro- chloric acid is present, but only lactic acid ; while Bidder and Schmidt f declare they have found free hydrochloric acid. Gastric juice will always be found to give a precipitate with nitrate of silver or oxalic acid. It is probable that sometimes one sometimes the other acid is present, while occasionally both may be there. Ash of the juice. — When examined in the usual way, sodium * Bernard, Leoons de Physiolosie ExpSrimenUle. Paris, 1856. il. t Bidder und Schmidt, Die Verdauungssafte und der Stnflwechsel. Mittau und Leipsig, 1862. ANAL YSIS OF PANCREA TIC JUICE AND BILE. 45s and calcium chlorides; potassium, sodium, and calcium sulphates; and calcium carbonate and phosphate, will usually be found. Analysis of Pancreatic JmcB. This fluid may be obtained in sufficient quantity for analysis by cutting the duct, inserting a canula, and collecting the juice in a caouchouo bag. It is clear, viscid, and has an alkaline reaction (p. 203). The amount of solid matter may be ascer- tained by evaporating a known quantity, drying carefully in a hot-air chamber over sulphuric acid and under the receiver of an air pump, and weighing the residue. Preparation of pancrealm. — ^Add to the juice its own bulk of alcohol. A white flaky precipitate falls. Filter, dry carefully, and dissolve the filtrate in water. This is probably a solution of pancreatin along with a protein substance alHed to casein.. D'anUewsky* has tried to shew that in the pancreatic juice we have three ferments : one which acts on starch and tilbumin and fats ; a second, which acts on starch and albumin biit not on fats ; and a third, which acts on starch but not on albumin. Analysis of Bilk. Ox-bile is usually examined because easily obtained. It is a transparent greenish liquid, having a ropy character due to admixture with mucus. This last-named characteristic may be demonstrated by pouring the bile from one vessel to another. Sp. gravity about 1002. Reaetion, slightly alkaline, or neutral (p. 203). The analysis of bile may be conducted as follows f : — 1. Muavx. — Precipitate the mucus by adding to the bile half its bulk of alcohol (83 per cent) ; filter, wash the precipitate with spirit, afterwards with water, dry in a hot air chamber, and weigh. 2. Solid matter. — Evaporalte the fluid obtained by the last operation (which is bUe free from mucus) first over a water bath, then under the air pump on a sand bath heated to 100° C. Cool in vacuo, after which allow dry air to pass into the receiver, weigh quickly, and the result will indicate the amount of sol|id matter. The air may be dried before passing into the receiver by passing it over chloride of calcium. 3. Fat and cholestrin. — Pour upon the solid matter obtained * VirchoWs Archives, xxv. p. 2Y9 t Watt's Dictionary of Chemistry, article— Bile, p. 686. 4S6 PRACTICAL PHYSIOLOGICAL CHEMISTRY. as above, a few ounces of ether, and allow it to digest for twenty- four hours. Thus an etherial extract of the fat and cholestritt will be obtained, and the amount of these substances can be determined by evaporation and weighing (p. 19). Cholestrin is easily prepared by boiling a little powdered gall stone in alcohol along with a few drops of caastic potash to dissolve fatty matters. From this boiUng solution cholestrin separates out in laminae, often having a small notch at one corner (Plate I. fig. 19). 4. Bile flsacZ«.— These are taurocholic and glycochoUc acids (see p. 12), united with sodium and potassium. ■ They may be obtained by either of two methods. First method. — After the third operation of removing the cholestrin and fat by ether, an insoluble residue will remain. This must now be treated with cold absolute alcohol, which dis- solves the alkaliue salts of the bile acids along with a small proportion of pigment. Evaporate the most of the alcohol, add ether to the concentrated alcoholic solution, and set the liquid aside for forty-eight hours in a cool place. A precipitate is thus formed of the bile-acid-salta. Filter, and dry and weigh the precipitate. To estimate the amount of alkali united with the acids, add to the ether precipitate a little sulphuric acid. Thus sulphates of soda and potash will be fortned, which may be separated, weighed, and the amount of the alkalies calculated. Second method. — Add to the bile along with alcohol, basic acetate of lead ; filter, wash the precipitate with a solution of carbonate of soda ; evaporate to dryness. We thus obtain the sodium salts of the bile acids, to which we add first a little absolute alcohol, and afterwards dilute with water. The chemical composition of the bile acids has been already given at pp. 12 and 16. It is to be observed that the sulphur of the bUe exists in taurin, one of the ingredients of taurocholic acid. The relative quantities of the two acids may therefore be deter- mined by finding the amount of sulphur in the ether precipitate ; every six parts of sulphur correspond to 100 parts of taurocho^ late of sodium'.* 5. The residue, which is usually very small in amount, con- tains pigment, alkaline and earthy phosphates, chloride and carbonate of sodium. The amount of inorganic salts may be * For the mode of estimatiug the sulphur see Watt's Dictionaiy of Chemistry, article— Analysis (organic). Estimation o£ Sulphur, p. 247. ANALYSIS OF BILE. ,457 determined by incineration and subsequent chemical examina- tion. BUe pigments. — These are five ia number (p. 32), but they may be conveniently divided into the brown and the green. The brown pigments are soluble in chloroform, while the green are not, and thus we have a ready means of separating the two. The brovm pigments are bilirubin (red) and cholophsein (brown). To distinguish the cholophsein from the bilirubin, according to Bruoke,* evaporate the chloroform solution, wash the residue with alcohol and ether, until a brick-red powder, soluble ia ammonia, is obtained (bilirubin) ; add to the ammoniacal solu- tion a little hydrochloric acid, and cholophasin will be precipi- tated as yellowish-brown flakes. The green pigments are represented chiefly by biliverdin, which is insoluble in chloroform, but easily soluble in alcohol, benzol, or disulphide of carbon. The green pigment may be formed from the red pigment by boiling an alkaline solution of the latter ; and, according to Stadeler, the change may be represented by the following equation : — CibHisNA + -3.^0 + = CieH^oNA Bilirubin. Biliverdin. The chemical reactions of alkaline solutions of these pigments may be examined as follows :-;— Reagent. Bilirubin. Biliverdin. Chloroform. Soluble. Insoluble. Barium chloride. Precipitate. No precipitate. Calcium chloride. Precipitate. No precipitate. Neutral lead acetate. Eed precipitate. Darkgreenprecipitate. Silver nitrate. Eed-brown precipitate. Darkgreenprecipitate. Nitric acid. Play of colours ending Play of colours ending in a green. in a yellow. Optical properties of hile acids cmd pigments. — According to Hoppe-Seyler,t the bile acids rotate the ray of polarized light to the right. The highest rotatory power is shewn by cholic acid (p. 16). An alcoholic solution of the bile pigments when examined, by the spectroscope, give absorption bands in the vicinity of the letters C and D of the spectrum. Biliverdin absorbs light at both ends of the spectrum, and if not much diluted transmits * BriSoSe, J. pr. Chem. Ixxvii. 72. Jahresb, 1859, p. 637. t Hoppe-Seyler, J. pr. Chem. Ixxxix. 297. Bull. See. Chim. v. 622. 4S8 PRACTICAL PHYSIOLOGICAL CHEMISTRY. only green light. A very ■weak solution absorbs only the extreme red. Numerous modifications of these absorption bands may be obtained by acting on the pigment solution with nitric or hydrochloric acids, or by lead acetate or calcium chloride.* Tests for bile, bile acids, and bile pigment. — It is often of im- portance to ascertain the presence of bile in urine or other fluid. For that purpose the following tests may prove serviceable : — 1. Noel's test for bile. — Immerse a strip of blotting paper for a few minutes in the fluid, dry, and add a drop of nitric acid containing a little nitrous acid. If bile be present, it will assume a violet colour, changing to red or yellow.f 2. Pettenhofer's test for bile acids. — To a little diluted bile, or any liquid containing bile, in a test tube, add a little powdered white sugar, or its equivalent of syrup. Then pour in of strong sulphuric acid (very gradually) rather more than half the bulk of the liquid. By this means the temperature is gradually raised to the proper point, and a deep purplish-crimson colour makes its appearance. This test frequently fails when applied to urine, but if an attempt is made to separate the bile acids by the second method above described, and the test applied to the alcoholic and aqueous solution of the acids, very minute quan- tities will give the reaction. 3. The nitric acid test for the bile pigments. — Place a drop of the suspected fluid on a white porcelain plate, add carefully a drop or two of strong nitric acid, and at the point of contact of the fluid with the acid there will be a play of colours, passing through a red, green, pink, blue, violet, and yeUow. The appearance of the green colour, though often evanescent) is indicative of bile. A play of colours maybe obtained by the action of nitric acid on the pigment in concentrated urine, but it never shews a green tinge unless bile is present. 4. The silver oxide test for bile pigments. — Boil the fluid with an ammoniacal solution of silver oxide. Acidulate the filtrate with a few drops of hydrochloric acid. A purple colour will be produced if biliverdin be present, owing to the formation of an artificial compound called bUipurpin. Bilia/ry calcidi or gallstones. — These concretions consist usually of a nucleus of mucus or inspissated bile, which becomes coated with cholestrin. Upon this successive layers of earthy * Jaffe, ZeitsohrUt f. Chem. [2| v. 666. Maly, ibid. [2] v. 365. t Noel, J. Pharm. [31 xU. 3S4. ANALYSIS OF URINjE. 459 phosphates and carbonates are deposited, often tinged with the bile colouring matter. Analysis of the Urine. This secretion, from its great clinical importance, requires to be carefully examined. Urine may be either healthy or abnormal, that is to say, it may contain normal constituents, such as water, inorganic salts, and organic substances ; or it may contain occa- sional or abnormal constituents such as blood, albumin, sugar, fat, &c. 1. Physical properties. — In its fresh state it is clear, and of a light-yellow colour, has a peculiar odour, a bitter taste, and an acid reaction. With regard to colour, Vogel has classified the numerous varieties of shades of colour we constantly meet with into three groups : 1. YeUow urines ; 2. reddish urines ; 3. brown or dark urines. These again may be subdivided. The varieties of colour depend not on different pigments, but on variations in the quantity of the same pigment. This may be readily shewn by evaporating a light-coloured urine. We find that as the fluid diminishes in quantity, the colour becomes darker. On the other hand, when we dilute any dark-coloured urine, the colour becomes much lighter. The colouring matter of the urine, so far as known, has been already described at p. 34. The odowr of urine is affected by food, or medicine, for instance, asparagus, turpentine, saffron, cubebs, iSsc, may be detected. Turpentine gives urine the odour of violets. 2. Reaction, — The uriae of carnivorous animals is acid, except during digestion, while that of herbivora is alkaline, except after a prolonged abstinence from food. The cause of the constantly acid reaction of healthy human urine has been disputed. Liebig's view is, that it depends chiefly upon the presence of an acid phosphate, such as NaHjPO^. According to the researches of Lehmann, however, there can be no doubt, that in many cases, free hippuric and lactic acids exist in the urine, and consequently assist in giving it its acid reaction. The urine is alkaline during digestion, owing to the increased elimination of alkaline phosphate, such as NagPOj derived from the food. 3. Fermentations of wine. — Two fermentations occur : 1st, the add; 2d, the alkaline. 46o Practical physiological CHEMisTkv. When the urine has been left at rest, especially under the influence of a moderate degree of heat, its acid reaction becomes stronger ; and distinct crystals of uric acid are often deposited on the sides and bottom of the glass. This increase of its acidity usually goes on for some days, and may even continue in rare instances for two or three 'weeks. The acidity, however, at last begins suddenly to diminish, and gradually disappears. The urine now becomes lighter in colour ; a whitish, iridescent pellicle forms on its surface ; and the presence of ammoniacal odour indicates that it has become alkaline. A deposit is thrown down consisting of the ammoniaco-magnesian or triple phos- phate, phosphate of lims, and urate of ammonia. This change, the alkaline fermentation, is owing to the decomposition of the urea into carbonate of ammonia. Urea unites with the element of water thus : — CN2H4O + 2(H20) = (NH,)2C03 Urea. Water. Carbonate of ammonia. The urine is thus rendered alkaline, and the earthy phosphates are precipitated, — the phosphate of lime as isuch, and the phos- phate of magnesia as the triple phosphate- of ammonia and magnesia (MgNH^POj + 6 HjO). 4. Quantity in twenty-four hours. — The determination of the quantity of urine passed in a given time forms the basis of all quantitative investigations, and must therefore not be over- looked. In all analyses of the urine; the quantity of the fluid, and the time during which it is collected, must be taken into consideration. The time usually adopted is twenty-four hours. The quantity can be determined either by weight or measure ; but measure is almost invariably employed for the purpose. The cubic centimetre we take as a standard of unity ; one thousand cubic centimetres are equal to a litre, and one litre of distilled water weighs a thousiand grammes. When we have learnt the specific gravity of urine, the quantity of which has been ascer- tained, we may readily arrive at a knowledge of its weight, by simply multiplying the number of ascertained cubic centimetres by the specific gravity of the urine. Thus 1000 0. C. of urine of I'OSO sp. gr. will weigh 1030 grammes. ' The urine is measured by means of graduated glass jars of different sizes. Care should also be taken in all examinations of urine that the glass vessels are kept quite clean, because a small amount of decomposing ANALYSIS OF URINE. 461 organic matter is sufficient to induce the alkaline fermentation in a few hours. • 5. Amount of solid matter. — For this purpose we require an accurate chemical balance, several small porcelain crucibles or capsules, a water bath formed of copper plate, a hot air bath or chamber, and a shallow vessel containing a little strong sulphuric acid which can be placed under a bell-jar. The method of estimating the amount of solid matter is as follows : — (1.) Measure ten cubic centimetres * in a carefully weighed porcelain capsule. (2.) Evaporate to dryness at a low temperature over a water- bath. (3.) Dry as thoroughly as possible, and afterwards place "the capsule in the hot air chamber for several hours. (4.) Remove the capsule from the chamber, and place it over the sulphuric acid under the bell- jar for two hours. (5.) At the end of that time remove it, and weigh rapidly. The difference in weight from that of the urine used, gives the amount of solid matter in the urine. The object of this process is to remove the water as thoroughly as possible. An example will illustrate the calculation : — Weight of capsule alone 30'62 grammes. Weight of capsule with residue 30 '84 „ Weight of residue 0'22 „ < Therefore in 10 C. C. of the urine examined there are 0'22 grammes of solid matter. It is important, if a very accurate estimate is required, to weigh several times after the residue has been placed over the sulphuric acid, and not to finish the process until there is almost no difference (say one or two mille- grammes) between the two weights, t 6. Amount of orgam/ic and inorganic matter. — That the residue obtained by evaporating a certain quantity of urine consists partly of organic matter may be easily shewn by the fact that it chars on being strongly heated. If a white heat be applied for some time, the blackened appearance is removed, and a * The symbol for cubic ceniimelres is C. C. ; for grammes, grms. ; for miUe- grammes, m.grms., &c. t A still more accurate method is described by Neubauer and Vogel in their " Guide to the Qualitative and Quantitative Analysis of the Urine," New Sydenham Society. 1863. P. 153. The method of examining urine described in the text is chiefly that of Neubauer and Vogel. 462 PRACTICAL PHYSIOLOGICAL CHEMISTRY. ■white ash is left behind. This white ash consists of inorganic salts. 'The mode of determining the amount of organic and inorganic matter is as follows : — (1.) Evaporate 10 C. C. of urine in a porcelain capsule. (2.) When the residue is dry, scrape it out with a small plati- num knife, and place it in a weighed platinum capsule (along with from 10 to 13 drops of strong nitric acid or with a known weight of spongy platinum), in which it is to be heated, at first gently, but afterwards strongly* We thus obtain a white ash, free from carboil. The addition of nitric acid converts the urea into nitrate of urea, which when heated is first decom- posed into carbonic acid and nitrate of ammonia, and finally escapes as water and nitrous oxide gas. By using nitric acid as an oxidising agent we save time, for the urea, which forms the greatest part of the residue, and produces much carbon at the ordinary red-heat, is thereby removed, and a portion of the remaining carbon more readily oxidises and burns off under the action of the nitrate of ammonia which is formed. We must, however, carefully avoid adding too much nitric acid, and using too great a heat, so as to avoid losing chlorine and phosphorus. (3.) Weigh the ash with the crucible, and subtract from it the weight of the crucible alone, and the difference gives the actual amount of incombustible salts. Example : — Crucible with ash - 24'656 grammes. Crucible alone 24'524 ,, Weight of ash in 10 C. C. of urine -132 7. Amount of water. — Th^ loss of weight, after evaporating, at a low temperature, 10 C. C. of urine represents the amount of water in 10 C. C. 8. Specific gravity. — This may be determined in three ways : — (1.) By the specific gravity bottle. — Ascertain the weight of the bottle alone, then the weight of the bottle filled with dis- tilled water, and thirdly, the weight of the bottle filled with urine. In each operation the bottle must be quite full and carefully wiped dry. Then subtract from each of the last two the weight of the bottle. The proportion then is : weight of water : weight of urine : : specific gravity of water : specific gravity of urine. Example : — ANALYSIS OF URINE. 463 Weight of bottle =12 Grammes. Weight of bottle + water = 45 „ Weight of bottle + urine = 46 „ Therefore 33 : 34 : : 1000 : 1030. Weight of Weight of Speoiflo gravity Specific gravity water, urine. of water. of urine. The chief objection to this process is that it is tedious, but th care great accuracy may be attained. (2.) By the iminometer. — We obtain only an approximative .owledge of the true specific gravity of the urine by the aid the urinometer. This instrument consists of a glass float aring a graduated stem, and kept upright by a little ball at J bottom containing mercury. It should be graduated so that 5 zero of the scale be on a level with the surface of the fluid len placed in distilled water, and the degrees should go as jh as 1050. To determine the specific gravity of the urine by means of ? urinometer, a proper cylindrical glass is filled with the ine, all froth removed by means of a glass-rod, and the an urinometer allowed to sink gently into the fluid. The iss should be wide enough to allow the instrument to float lely in the i^rine, and not to touch its sides. Bring the eye a level with the surface of the fluid, and read ofi' the scale the lower level of the curve — ^ formed by capillary attrac- n ; always read off at that level. [3.) By glass beads of such & weight that they will float ictly at the surface in fluids of various specific gravities, ese beads are numbered from 5 to 50, with many intermediate mbers. If bead No. 20 floats in the fluid so that its upper •face is ejiactly on a level with the surface of the fluid, the icific gravity of the fluid is 1020. ). Christison's method of ascertaining the amount of solid matter m the specific gravity.* — The rule is to multiply the last two ires of the specific gravity, ascertained as above, by 2 '33, number ascertained from numerous experiments) and the rtient gives the amount of solid matter in 1000 parts of urine. ample: — A man passes 46 ounces of urine in 24 hours- 2cific gravity, 1025. How much solid matter is excreted ? Sir Bohert Chriatison, Bart., Tweedie'u Library of Medicine, vol. iv. p. 248, 464 PRACTICAL PHYSIOLOGICAL CHEMISTRY. —25 X 2'33 = 58-25 oz. of solid matter in 1000 oz. Then 1000 : 58-25 : : 46 : 2-6795 oz. Answer. — ^Amount of solid matter excreted by kidneys in 24 hours, 2-6795 oz. Volumetric Analysis. It is extremely convenient to estimate the amount of cer- tain constituents of the urine by volumetric processes because the analysis is simplified and time is saved. It is therefore essential first, that we understand the theory of the process, for which we are indebted to Gay-Lussac. Theory of the process. — It consists in submittiog the substance to be estimated to certain well-known reactions, using for such reactions, solutions of known strength, and from the quantity of solution employed, calculating the weight of the substance to be estimated according to the laws of equivalence. Tor example : — Suppose that it is desirable to know the quantity of pure silver contained in a shilling. The coin is first dissolved in nitric acid, forming a bluish solution, containing silver, copper, and probably other metals. It is known that chlorine combines with silver in the presence of other metals to form chloride of silver, AgCl, which is insoluble in nitric acid. The proportions in ■\yhich the combination takes place are 35-5 of chlorine to every 108 of silver ; consequently, if a standard solution of pure chloride of sodium is prepared ^y dissolving 58-5 grammes of the salt {i.e., 1 eq. sodium := 23, 1 eq. chlorine = 35 -5 = 1 eq. chloride of sodium, 58-5) in so much distilled water as will make up exactly 1000 O. C. by measure ; every C. C. of this solution will contain exactly enough chlorine to combine with 0-108 grammes of pure silver to form chloride of silver, which precipitates to the bottom of the vessel in which the mixture is made. In the process of adding the NaCl solution to the silver, drop by drop, a point is at last reached when the precipitate of AgCl ceases to form. Here the process must stop. On looking carefully at the graduated vessel from which the standard solution has been dropped, the operator sees at- once the number of C. C. which have been necessary to produce the complete precipitation of the silver, and as each C. C. equals -108 grammes of silver, it is easy to calculate the quantity of the latter present in the shilling. We therefore require in every volumetric process ; VOLUMETRIC ANALYSIS. 465 1. A solution of the re-agent, the chemical equivalence of which is accurately known. This we term the standard solu- tion (symbol S.S.). 2. A graduated vessel from which portions of it may be accurately delivered — the burette. 3. The decomposition which the solution produces with any given substan,ce is usually of such a character that its termina- tion is unmistakable to the eye, and thereby the quantity of the substance with which it has combined accurately determined. Occasionally, however, we use another solution which pro- duces a characteristic reaction with the standard solution, and which thus informs us when we have added excess of the standard solution. This is termed the indicator. Apparatus required. 1. The graduated pipette. — It is made of glass. It serves for measuring the fluid which is to be investi- gated ; and when filled to the neck, where it is marked by a single stroke or mark, contains 50, 20, 15, 10, 4, or 3 CO. In using it, its point is introduced into the fluid, and suction made until the fluid has risen above the level of the mark in the neck ; the upper opening is then closed with a moist finger, the pipette dried outside to remove any adherent fluid, and the finger slightly raised to admit a little air, and to allow the fluid to escape until it reaches the level of the mark, the surface of the fluid being kept on the same level as the eye. When the fluid has fallen to this point, the pipette is again firmly closed with the fingerj and its contents may now be allowed to run out into any convenient vessel, such as a beaker. 2. Flasks and Ja/TB. — These may be graduated from -j^th litre to 5 litres. There is usually a mark across the neck indicating the volumetric capacity. It is convenient to have these flasks so arranged that the volumes shall be whole numbers — not 1| litres, 2f litres, but I, 2, 3 litres, and so on. 3. Mohr's Bwette.—'YhSs instrument (Plate XXI. fig. 26, a, c) consists of a glass tube provided below with a caoutchouc tube a, which is closed by a spring clamp e. Two or more of these may be fixed into a wooden or iron frame g, h, m, m, so as to hang down perpendicularly. ' In using it, the pipette is filled up to zero with the volumetrical fluid, the urine to be tested measured out into the beaker glass I, and the volumetrical solution then allowed to run out into the glass beaker I, by pressing on the clip, and towards the end of 466 PRACTICAL PHYSIOLOGICAL CHEMISTRY. the experiment to drop into it, until the proper quantity has been added. * By this arrangement we secure both a rapid flow of the fluid, and also its flow in single drops. In investigations which require some time for their completion, two or more of these burettes are employed ; when completely or half-filled, they are fixed in the stand and there left, their upper opening being closed with a cork to prevent evaporation. Certain standard solutions act injuriously on the caoutchouc and clamp (such as nitrate of mercury in the urea process), and destroy them. In these instances it is advisable to use a burette, having a glass stop cock. Mode of conduciing tUe process. — In carrying out the volume- trical method of analysis, first carefully prepare the solutions required for the purpose, for upon these solutions the correct- ness of the analyses depends. Special directions for this object will be given under the head of each particular process. The solutions must always be preparedand used at a given tempera- ture, as their volume varies considerably under the action of heat. Care is also required in reading off the level of the fluid in the different kinds of measures used. Bubbles of air must be removed by a glass rod, so that the surface of the fluid be perfectly level. This point is obtained in the case of the pipette by allowing it to hang freely. We must also allow for the capil- larity of the tube. When we examine the curve, especially by transmitted light, several zones are readily distinguished in it. The measurements are most accurate, when (the pipette or the burette having been placed in a perpendicular condition) the eye is brought to a level with the under border of the lowest zone, and the graduation of the tube corresponding with it then read off. This border is most distinctly marked and seen by transmitted light. When the urine to be tested has been measured, and the pipette or the burette filled with the volumetrical solution, we first of all allow the solution to run slowly out, and at last to pass drop by drop into the urine, until the operation is completed. When the point of completion is shewn in all parts of the fluid, by some distinct reaction, or by the use of an indicator, we are sure that the process followed is good ; but if this be not the * The yolmnetrical fluid is usually placed in the hurette and the urine in a beaker or porcelain capsule, but occasionallj, as in the diabetic sugar process^ the reverse is the case. INORGANIC CONSTITUENTS OF URINE. 467 case, then we must .test the mixture again and again towards the conclusion of the experiment, until the right point has been attained.* DETBCTIOIf AND ESTIMATION OF THE INDIVIDUAL INORGANIC CoifSTITUBNTS OF HbALTHT UeINE. Under this head we shaU include chlorides, sulphates, phos- phates, iron, ammonia, and silicic acid. 1. Chlorides (p. 28). — Nitrate of silver always serves as a test for the presence of chlorides in the urine, giving a white curdy precipitate. The phosphoric acid in the urine also throws down a precipitate with nitrate of silver ; but this precipitate — phosphate of silver — is soluble in nitric acid, which the chloride of silver is not. Consequently, in testing the urine for chlorine we must, before the nitrate of silver is dropped into it, render the mixture strongly acid by the addition of one or two drops of nitric acid.* This wiU prevent the .phosphate of silver being thrown down. The chlorine exists chiefly in combination with sodium, but a small amount is in the compound of chloride of potassium. «The soda may be demonstrated in the urine ty giving a yelloV colour to the inner blow pipe flame, and the potash by giving a yellow precipitate of octahedral crystals of the double chloride of potassium and platinum on the addition of the tetrachloride of platinum to an acid and alcoholic solution of the ash. The amount of chlorides varies considerably. They are much diminished in all acute febrile diseases, the quantity sinking to a minimum, so as sometimes to form scarcely one hundredth of its normal standard. The quantity increases as the disease passes away, and during convalescence is occasibnally greater than normal. The presence of a large quantity of chlorine, 6-10 grammes daily, indicates good digestion ; a small quantity, under five grammes, weak digestion, provided always that the diet of the patient is not such that only very little chlorine is ingested. 2. Sulphates (p. 29). — The sulphates yield, with chloride of ■* In this work, we shall give the volximetric processes for only a few of the con- stituents of urine, namely, those most important physiologically or pathologically. For details sa to the others, reference is made to Neubauer and Vogel, and other works. T 46? PRACTICAL PHYSIOLOGICAL CHEMISTRY. barmm or nitrate of baryta, a precipitate Tehich is iusoluUe in mineiral acids, and easily detected even when the solution is exceedingly diluted. Consequently, iti testing the urine for its sulphates, we first of all render it strongly acid by the addition of a drop of nitric acid or hydrochloric acid, for the same reasons as given in the case of chlorides, and then add to it a solution of chloride of barium or nitrate of baryta. A heavy precipitate falls of sulphate of baryta. If, therefore, we take a certain volume of urine, say 10 C. C, and add to it an equal or sufficient quantity of chloride of barium and hydrochloric acid, we obtain, from the greater or less quantity of precipitate which is thereby thrown down, an approximative estimate of the amount of sul- phates present in it. 3. Phosphates (p. 28). — These consist of pho^hates of the alkalies, and phosphates of the alkaline earths. , The latter are insoluble in an alkaline iluid, and consequently are always pre- cipitated when the urine becomes alkaline (p. 262). Tests for the phosphates. — (1.) Chloride of barium, or nitrate of baryta, give a precipitate of phosphate of baryta, soluble in mineral acids. (2.) Ammonia, or caustic potash, or caustic soda, give a pre-' cipitate of phosphates. ' (3.) Perchloride of iron throws down from a solution of phos- phates contaiuing free acetic acid, a yeUowish-white precipitate of perphosphate of iron. (4.) Acetate of uranium added to urine containing a few drops of free acetic acid, gives a light yellow or lemon-coloured precipitate, consisting of uranium and ammonium double phos- phate. (5.) Molybdate of ammonia, along with a few drops of nitric acid on boiling yields a brownish, greenish, or canary-yellow precipitate of the phospho-molybdate of ammonia. This is an exceedingly delicate reaction. VOLTTMETKIC PeOCESS EOR PhOSPHOBIC AcID. It is often important to determine with accuracy the amount of phosphoric acid excreted in a certain period of time. This is best accomplished by the volumetric process which depends on the fact that a precipitate of uranium and ammonium double phosphate (^TJt^^^^O^ is immediately formed, when a hot solution of a phosphatic salt which is soluble in water or acetic PHOSPHORIC ACID. 469 acid, is treated with a solution of acetate or nitrate of uranic ozide in presence of free acetic acid.* The phosphate of uranic oxide thus thrown down, appears as a whitish-yellow,passingeven into a greenish, precipitate ; itis completely insoluble in water and acetic acid, but soluble in mineral acids. The exact point of the completion of the reaction cannot be ascertained in the fluid, on account of the slimy character of the precipitate, and of the slowness of its deposition ; consequently, in order to determine whether or not the whole of the phosphoric acid is precipitated, a small excess of uranic oxide must be added, — ^the presence of this salt being readily shewn by the highly sensitive reaction of the salts of urauic oxide with ferrocyanide of potas- sium, which gives a reddish-brown precipitate. The ferrocyanide of potassium thus serves as an indicator. It is necessary, in the first place, to prepare with great care the standard solutions. (a.) Stomdard phosphoric aaid-solution. — This solution should be so coiistituted as to resemble the urine as nearly as possible, as regards the amount of phosphoric acid i 50 C. C. of it should contain O'l gramme of phosphoric acid. It may be readily pre- pared from chemically pure phosphate of soda, which has not undergone efflorescence. The pure crystals are rubbed down as fine as possible, dried between folds of bibulous paper, 10"085 grammes weighed and dissolved in a litre of water. 50 C. C. of this solution contain exactly O'l gramme of phosphoric acid. (6.) Accede of soda-solwtion. — It has been found 0'5 gramme of acetate of soda is, under all circumstances, sufficient for 50 C. C. of urine. Consequently, 100 grammes of acetate of soda are dissolved in 900 C. C. of water, and the solution brought up to a litre by the addition of JOO 0. C. of concentrated acetic acid. In the volumetrical process, 60 C. C. of urine are treated with 5 C. C. of this acid solution of acetate of soda. (c.) Solution of uranic oxide. — Pure commercial uranic oxide, is dissolved in pure acetic acid, free from all empyreumatic matters, the solution diluted, and its strength tested with the standard phosphate of soda-solution (a). One C. C. of it should precipitate, and indicate the presence of, only 0"005 gramme of phosphoric acid. 50 C. C. of the phosphoric acid-solution (a) ^ O'l gramme of phosphoric acid, would consequently require exactly 20 C. C. of the uranic oxide solution; this • Neubauer and Vogel, pp. 191-193. 470 PRACTICAL PHYSIOLOGICAL CHEMISTRY. solution, therefore, must, in the first place, contain 0'4023 gramme of uranic oxide for the precipitation of the phosphoric acid, and, secondly, a slight, excess of uranic oxide for the indication of the completion of the reaction. 50 C. C. of the solution of phosphoric acid require 20 C. C. of the uranic oxide-solution, which again must indicate and preci- pitate 5 milligrammes of phosphoric acid. If, for example, we employ 18"0 C. C. of the uranic oxide-solution to 50 C. C. of phosphoric acid-solution, we must add to each 180 C. C. of the same 20 C. C. of water. For this purpose we measure oflf 1 litre of the uranic oxide-solution, and add to it the .quantity of water required. In the case supposed, 111'2 C. C. of water must be added to 1000 C. . C. of uranic oxide-solution to produce the required degree of strength. Thus, if we have a second time used 19'8 0. C. of uranic oxide-solution to 50 C. C. of phosphoric acid solution (O'l gramme of phosphoric acid), we add to each 198 C. C. of the same 2 C. C. of water, and make a new and final test with the phos- phate of soda-solution. The uranic oxide-solution, each cubic centimetre of which precipitates 5 milligrammes of phosphoric acid, and which also contains a small excess of uranic oxide for the final re-action, must contain 20 3 grammes of pure uranic Bxide in a litre. Process for the whole of the phosphoric acid with acetate of wraniwm, ferrocyanide of pdtassiwm, being used as an, indicator. 1 C. C. of S. S. = 0'005 grainmes of phosphoric acid. • (1.) Place 50 C. C. of filtered urine in a beaker. (2.) Add to it 5 C. C. of a solution of sodium acetate. (3.) Drop in standard solution of uranium acetate, until a drop gives a faint brown colour when mixed with a drop of potassium ferrocyanide, on a porcelain plate. (4.) Boil and test again. If necessary, add a few drops more of the S. S. until the brown colour again appears immediately on testing. Example. — Patient passes in 24 hours 1000 C.C. of urine-; 25 C. C. of S. S. are used in volumetric process for phosophoric acid. How much phosphoric acid is excreted : — '005 X 25 = •125 grammes in 50.oz. - Then 50 : -125 : : 1000 : 2-5 gramnies, the quantity in 1000 C. C. of urine. PHOSPHORIC ACID. 47 1 Process for estimating the amount of phosphoric add united with the alkaline ea/rths. (1.) Take 100 C. C. of filtered urine, and make it alkaUne with ammonia. The earthy phosphates are thus precipitated. (2.) Let the urine stand for 12 hours. (3.) Collect the earthy phosphates on a filter, and wash with ammonia water. (4.) Wash precipitate into a beaker, heat and dissolve inafew drops of acetic acid. (5.) Add 5 C. C. of acetate of sodium solution, and add water to niake up volume to 50 C. C. (6.) Proceed with acetate of uranium solution as before, and make the necessary calculation. Taking the previous example, we find that : — The whole of the phosphoric acid, as deter- mined by acetate of uranium process, is 2'5 grammes. Phosphoric acid with the earths required 5 C. C. of S. S. Therefore, "005 X 5 -= •025 grammes in 100 C. C. of urine. Patient passed 1000 C. C. Therefore, in 1000 C. C. we find of phosphoric acid united to the alkaline earths, 0'25 Phosphoric acid with alkalies, 2'25 ' 2 '5 grammes. 4. Iron. — This is rarely found in urine, and only in very minute quantities. It probably exists in the colouring matter. For testing and ascertaining the presence of iron in the urine, the ash obtained from the urine is always employed. Dissolve in a few drops of hydrochloric acid. Boil with a drop of nitric acid, and add a drop of sulphocyanide of potassium, thereupon the fluid will assume a reddish colour, and if a considerable quan- tity of iron be present, a deep dark-red colour. When mere traces are present, the change of colour is best observed by placing the tube over a white ground. 5. Am/monia. — ^According to Neubauer and Vogel, a small amount of free ammonia is present even in acid urine, but its. quantity is so small as to render its detection extremely difiicult. It is of no importance. 6. Silicic acid. — This acid has been detected in very small amount by incinerating the ash of urine with sodium and 472 PRACTICAL PHYSIOLOGICAL CHEMISTRY. potassium carbonate, dissolving the ash in water, and acidulat- ing with hydrochloric acid. On again evaporating to dryness, the silicic acid remains behind in a pure state. Detection and Estimation oe the Individual Orsanic ., Constituents op Healthy Urine. i'hese are urea, uric acid, hippuric acid, creatin and creatinin, xanthin, and benzoic, phenylic, damaluric, damolic, and succinic acids. 1. Urea, (p. 14 and p. 25). — This substance may be prepared from the urine by first precipitating all the phosphates by means of baryta, filtering, evaporating the filtrate, and treating the residue with alcohol. This alcoholic solution is evaporated to dryness, and the product again treated with pure alcohol. We thus obtain an alcoholic solution of urea, which crystallises out on evaporation. The most important salt of urea is the nitrate, which may be obtained by mixing a concentrated solution of urine or urea with concentrated and pure nitric acid. It then appears as white plates. Tests for Urea. — (a.) When the quantity of urea is small, the formation of nitrate of urea may be observed under the micro- scope, and in the following way : — One end of a little bit of thread is laid in the drop which is to be tested for urea ; the drop itself and one-half of the thread is then covered with the glass, and the other end of the thread moistened with a drop of pure nitric acid. In this way, the two fluids being gradually mixed together, we may see the formation of crystals of rhombic plates or short prisms, as well as numerous complicated forms. (6.) When a solution of nitrate of mercury is added to urine, we obtain a white floculent precipitate, which varies in composition according to circumstances. It may, according to the quantity of urea present, consist of mercuric oxide and nitrate of urea, or urea combined with mercuric nitrate and mercuric oxide. Upon this reaction, however, the volumetric process is based. Volumetkic Process for Urea. When a dilute solution of urea is added to an equally dilute solution of nitrate of mercury, and the free acid neutralised by carbonate of soda, a white precipitate is obtained. After all the urea has been precipitated, we reach a point where the yellow-coloured hydrated oxide of mercury is thrown UREA. 473 down by the carbonate of soda, carbonic acid escaping with eflfervescence. It has been found by analysis that the urea is thrown down in combination with oxide of mercury, and that the precipitate contains four equivalents of oxide of mercury to one equivalent of urea. The exact point, or rather the exact point has just been over-stepped,- when all the urea is precipi- tated, and is known by t^e formation of a yellow pellicle on the surface of a drop of carbonate of soda mixed with a drop of the fluid being examined for urea. Prepa/rations of standard solutions, (a.) Stomdard solution of wrea. — Four grammes of pure urea, dried at 100° C, are dissolved in water, and diluted until the volume of the fluid equals 200° C. C. Thus 10 C. C.=-2 grammes of urea. (6.) Stcmda/rd solution of nitrate of m»cwry. — Pure oxide of mercury best serves for the preparation of the mercury solution. Commercial oxide of mercury may be obtained sufficiently pure for the purpose. An oxide of mercury which leaves no visible residue when heated on platinum foU is fitted for the purpose. Of this oxide 77'2 grammes, dried at 100° C. are taken by weight, dissolved under a gentle heat with the smallest possible quantity of nitric acid in a porcelain basiu, evaporated to a syrup, and then diluted with water up to a Utre. Should any basic salt separate, a few drops of nitric acid are dropped into it until the precipitate re-dissolves. The next step is to graduate the prepared solution of mercury by means of the standard solution of urea. For this purpose 10 C. C. of the urea-solution are measured off and placed in a beaker, the dilute mercury solution is then added to it, until a few drops of the mixture, added to a drop of carbonate of soda on a' watch-glass, give a yellow colour. If, for example, to obtain this reaction, we use 19'25 C. C. of the mercury solution, we add to each 192-5 C. C. of the mercury solution, 7'5 C. C. of water, and thus get 200 C. 0. of a solution, 20 C. U. of which will pre- cipitate the urea from exactly 10 C. C. of urea solution (that is ' -2 grms.). Thus 10 C. C. of mercuric nitrate solution will correspond to •! grms. of urea. Process for estimating Vrea with, Nitrate of Mercwy, Carbonate of Soda being used as an Indicator. (1.) If albumin be present in the urine, separate it by boiling and filtration. 474 P.RA CTICAL PHYSIOLOGICAL CHEMISTR Y. (2.) Mix the urine with half its volume of a solution called " baryta mixture" (composed of two volumes of solution of Barium hydrate with one volume of Barium nitrate, both saturated in the cold). (3.) rUter to get rid of Barium sulphate and phosphate. (4.) Take 15 C. C. of filtrate (=10 C. C. of urine) and place in a beaker. (5.) Drop in S. S. till precipitate ceases, testing the mixture ■ from time to time with a solution of sodium carbonate, until a faint yellow reaction is obtained. We thus obtain a knowledge of the quantity of urea in 10 C. C. of urine. Exa/mple. — Patient passes in 24 hours 1000 C. C. of urine, 14 C. C. of solution of mercuric nitrate are employed. How much urea is excreted ? 1 C. C. of mercuric nitrate solution =•01 grms. of urea .'. 14 C. C. = '14 grma. in 10 C. C. of urine. Then 10 : "14 : : 1000 : 14 grms. of urea, the quantity in 1000 C. C. of urine. Corrections for wines containing more or less than two per cent, of i^rea.* — The reaction between mercuric nitrate and carbonate of soda is exact only for fluids containing two per cent, of urea, and we require 30 C. C. of S. S. for complete precipitation of the urea in every 15 C. C. of urine, as well as for the reaction with sodium carbonate. When the urine cor(tains more than two > per cent, of urea the reaction takes place too soon, when it con- tains less the reaction is delayed. • (a.) With more than two per cent, or excess of urea. — When double the volume of mercurial solution has been used, and no reaction set in, 1 C. C. of distilled water is added to the mixture' for every additional 2 C. C. of the mercurial solution used, and thus the proportion of urea is maintained at two per cent. Thus, if 30 C. C. of solution of mercuric nitrate are added to 15 C. C. of urine, and the reaction is not seen, 1 C. Q. of distilled water is added, and the process is continued. If the reaction set in when 10 C. C. more, or 40 C. C. in all, of the mercurial solution have been used, the 5 C. C. of distilled water added (i.e. 1 C. C. of water for every 2 C. C. of the excess over 30 C. C.) wiE, with the original 15 C. C. of urine, make 20 0. C, and the mercurial * Corrections must also be made, if 'great accuracy be desired, for the chloride of sodium, and carbonate of ammonia, but as these are not very important, reference is made to Neubauer and Vogel, p. 186. URIC ACID. 475 solution will have been employed on a urine containing two per cent, of urea. (6.) WUh less than two per cent of wea. — ^If the urine contain less than two per cent, of urea, subtract "ICC. from every 5 C. C. of mercurial solution less than the normal 30 • C. C. Thus, if with 15 C. C. of urine, the reaction with sodium carbonate is got on using 20 C. C. of solution of mercuric nitrate, '2 C. C. — that is ■! X 2, are deducted, and 19'8 CO. taken as correct. 2. Uric add (pp. 13, 357). — The presence of this acid may be readily demonstrated in urine by placing a few ounces in a conical glass, adding a few drops of hydrochloric acid, and allowing it to stand for forty-eight hours. Uric acid then crystallises out, and appears on the surface of the fluid and adhering to the bottom and sides of the glass. When examined microscopically, the crystals will be found as represented in Plate I. figs. 1 and 2. The mv/rexide test for wric add, — Place a few drops of urine on a large flat porcelain lid. Add a drop of nitric acid. Evapo- rate nearly to dryness, and then bring a glass rod dipped in a solution of ammonia over the residue. A splendid purple- red or violet colour of murexide is produced. In this te§t the nitric acid frees uric acid from its union with bases, and converts it into two substances termed alloxan and alloxantin (p. 13). A compound called murexide or purpurate of ammonia is then formed by the union of the ammonia with these two uric acid derivatives. Sehiff's test for uric add.* — Dissolve the suspected powder in sodium carbonate, and place a drop of the solution on a bit of blotting paper moistened with nitrate of silver solution ; if uric acid be present, a brown spot appears, carbonate of silver being reduced to oxide by uric acid at ordinary temperatures. Garrod's test for wric add present in, small quantity.^ — This test is more especially applicable to the detection of uric acid in the blood. Take about two drachms of the serum and place it in a flat glass dish or watch-glass. To this add twelve drops of ordinary strong acetic acid, which wUl cause the evolution of a few bubbles of gas. When the fluids are mixed, introduce two^ or three threads of unwashed cotton. AUow the glass to stand on the mantel-piece, or on a shelf in a warm room, for from * Sohiff. Ann. Ch. Pharm. cix. 65. t Garrod On Gout. London. 1863. 476 PRA CTICAL PHYSIOLOGICAL CHEMISTR V. thirty-six to sixty hours, until its contents set, from evaporation. If the cotton fibres be then removed and examined microscopi- cally with a half -inch object-glass, they wiU be found covered -with crystals of uric acid, if this agent be present in the serum. The crystals form on the thread somewhat like masses of sugar- eandy on string. 3. Hippvric acid (p. 15). — Thip acid exists in very minute quantity in human urine, more especially after a person has taken benzoic acid, toluene, cinnamic, or mandelic acids, but it may be readily prepared by treating the urine of a cow or horse with excess of lime water, and thus precipitating it as hippurate of lime. Evaporate to 1-lOth of the original volume of the urine, and add hydrochloiic acid. Hippuric acid crystallises out impure, but the crystals may be obtained colourless and semi- transparent by dissolving them in water in the presence of animal charcoal, and allowing them again to crystallise out (Plate I. fig. 5). 4. Creaim and ereatmin (p. 18). — TJrine contains only a small quantity of creatin and creatiuin, so that a large amount of the fluid is required for their demonstration. The mode of separat- ing these from urine is as follows : — Three hundred C. C. of fresh urine are neutralised with milk of lime, and the phosphoric acid then thrown down by a solution of chloride of calcium. Filter and quickly evapor?ite to dryness in a water-bath. The residue thus obtained is extracted with absolute alcohol, allowed to stand for some hours, and again filtered ; the clear fluid is theB) treated with a few drops of a concentrated solution of chloride of zinc free from acid. The mixture becomes turbid, and the separation of the creatinin-chloride of zinc is completely effected in forty-eight hours. The compound is washed on a filter with spirits of wine, dried, and microscopically examined (Plate I. figs. 11 and 12). To obtain the creatinin in a pure state, dissolve the zinc com- pound in a small quantity of boiling water, and separate- the oxide of zinc and hydrochloric acid by boiling the fluid with freshly-precipitated and well-washed hydrated oxide of lead. The filtered liquid is rendered colourless by boiling with animal charcoal, and evaporated to dryness. The residue, which con- sists of a mixture of creatinin and creatin, is then treated with cold strong spirits of wine, whereby the creatinin is dissolved and the creatin left. XANTHIN. 477 Should the urine operated upon contain albumin, the albumin 1st be previously separated from it by coagulation. 5. Xantkin (p. 16).* — The mode of preparing this substance im urine is as follows : — TVesh, healthy urine, in quantity not s than from 100 to 200 pounds, is evaporated in a water-bath from one-sixth to one-eighth of its original volume, and its osphorie acid removed by precipitation with baryta- water. The :rate is again evaporated until the salts are crystallised out of ; the mother-liquor thus obtained is then well diluted with ,ter, a solution of acetate of copper added, and boiled for some le. A dirty-brownish precipitate is thus obtained, which is !t decanted and then washed on the filter with cold water til all chlorine-teaction has disappeared. By treating this jcipitate Ivith hot nitric acid, we obtain a brownish solutioa, im which the impure xanthin-silver compound is precipitated nitrate of silver. The crystalline compound, after being shed, is dissolved in boiling dilute nitric acid ; any remaining :culi of chloride of sUver are removed by filtration, and the rate set aside and allowed to crystallise slowly. The collected ^staUine silver'compound is freed from nitric acid by digestion th an ammoniacal solution of sUver ; the washed precipitate Fused through water, boiled, and the conjpound decomposed sulj)huretted hydrogen. The boiling filtered solution deposits, len concentrated, coloured flocculi of xanthin, and the re- inder is obtained by further evaporation. The prepai'ation IS obtained is, however, always much discoloured ; but by ution in strong hydrochloric acid and treatment with animal ireoal, the purification is readily effected. The filtrate, thus ed from colour, yields, when evaporated, hydrochlorate of ithin, from which pure xanthin may be obtained by re- Lted treatment with ammonia, and by subsequent removal the chloride of ammonium by washing with cold water. 3. Beingoia, phenylia, tawrylic, damaVu/rie, damolia, suacmic, die, formic, lactic, and acetic acids. — Human urine contains y a very small and variable quantity of these acids. Acetic I butyric acids are usually to be found in decomposing urine. ;s not within the scope of this work to describe the various icesses by which these substances can be obtained from urine, 1 reference is made to larger works on Physiological Che- 3try. * Neubauer and Vogel, p. 24. 478 PRACTICAL PHYSIOLOGICAL CHEMISTRY. Detection and Estimation of the Abnormal Constitttents or Ueine. "We shall consider the f oUowing : albumin, sugar, bile pig- ment, bile acids, fat, kiestein, lactic, acetic, and butyric acids, sulphuretted hydrogen, allantoin, leucin, and tyrosin. 1. Alhvmdn. — This substance is occasionally present for a short time in healthy urine, but as a rule its presence is indica- tive of disease of the kidneys. It is therefore of the greatest importance to be able to detect it even in minute quantity. Albumin is always present in urine containing blood. Tests for alhvmin. (as.) Heat. — In the first place, test the reaction of the urine with litmus paper. If it be alkaline, or neutral, add to it a few drops of acetic or nitric acids ; if very acid, carefully neutralise with a little dilute ammonia. Boil a small quantity in a test tube. If albumin be present in gmall amount, the fluid will become turbid when the heat exceeds 68° C. ; if it be abundant, there will be a distinct coagulation. It is important to remember that if the urine be either alkaline or neutral, coagulation may not take place — the albumin, if present in small quantity, uniting with the alkali. On the other hand, if a small amount of albumin be present in a large quantity of water, and there be excess of acid, no coagulation may follow, because a combination of albumin, with the acid may be formed, which is soluble in water. Another fallacy to be remembered is, that upon boiling certain varieties of urine, a precipitate of earthy phosphates takes place, which, however, can be readily distinguished by the addition of a little dilute nitric acid, which dissolves the phosphates, but not the albumin. (6.) Nitric add test. — On adding nitric acid to urine a white turbidity occurs if albumin be present in small, and distinct coagulation if present in large, amount. Sometimes, however, no coagulation is obtained because nitrate of albumin is formed, which is soluble in a large quantity of water ; in other specimens of urine, a precipitate of nitrate of urea may be formed, which, however, is readily detected by means of the microscope ; while in the urine of patients in the habit of taking copaiva, cubebs, and other oleo — ^and resinous — medicines, a white turbidity appears, which, however, does not sink to the bottom of the test tube as albumin does, but will remain for many hours suspended in' the fluid. DIABETIC SUGAR. 479 (c.) Ferrocyanide of potassiv/m test. — When to a well-filtered urine, acidulated with acetic acid, a weak solution . of ferrocy- anide of potassium (5 grains to the gi) is added, there is a white precipitate. If there be a large quantity of mucus in the urine, this test is not serviceable. In testing for albumin, therefore, it is better to employ both heat and nitric acid than either alone, and if the above sources of fallacy are borne in mind, there is usually no difficulty in detecting even minute traces of albumin. Estimation of the quantity of albwnin hy weight. — ^Place 20 C. C of urine, diluted with 80 C C of water, in a beaker, and allow the albumin to coagulate in a water bath. Collect the ooagulum 6n a filter, wash and dry it at 100° C, weighing occa^ sionally until there is no appreciable difi'erence between two weighings. This is albumin with inorganic matter. Incinerate, and collect and weigh the ash. Deduct this from the weight of albumin + inorganic matter, and the difference will be a very near approximation to the amount of albumin. Example. — Patient passes 1000 C. C. of urine in 24 hours. 20 C. C. yielded •454 grammes of albumin -|-- ash. After incineration, the ash was found to weigh '0015 grammes .■. '454 — ■0015='4525 grammes in 20 C. 0. In 1000 C. C. therefore, the amount of albumin would be -4525 x 50 = 22-625 grammes. There is also a volumetric process for albumin depending on the fact that albumin is precipitated by ferrocyanide of potassium, but it is open to so many objections that the process by weight is always preferred. 2. Sugar. — The variety of sugar found in urine is grape sugar CjHijOb frequently termed diabetic sugar. Briicke has demonstrated that sugar in small quantity may frequently be found in healthy urine ; but its constant presence in large amount in urine constitutes the disease known as diabetes (S/«, through, and /Saivm, I pass). The urine ia this disease is usually light coloured, froths readily on being poured from one vessel into another, and has a high specific gravity. Preparation of dietetic sugaa- from wine.. — Evaporate urine to consistence of syrup, and allow the sugar to crystallise out. It is still-impure, being mixed with urea and extractive matters. Separate these by means of absolute alcohol, and then add to the residue spirits of wine which will dissolve the sugar. It is again allowed to separate out from this solution, and the crystal- 48o PRA CTICAL PHYSIOLOGICAL CHEMISTR Y. liue masses purified from alcohol by repeated re-orystallisations from water. When thus obtained, it is white, and crystallises in little lumps. These are composed of crystals belonging to the rhombic system. Tests for sugar in wrine. (a.) Moore's test with caustic potash. — To the suspected urine add an equal bulk of solution of caustic potash, and boil. If sugar be present, a deep orange-brown (like dark sherry) will be obtained. If sugar be present in large quantity, the colour is dark purple, and frequently almost black. This colour is produced by the action of KHO on CgHijOg producing melassic and glucic acids. The caustic potash used should be freshly prepared, because if allowed to stand for a length of time in a glass bottle, it becomes contami- nated with lead, which, acting on the sulphur of urine, produces black sulphide of lead, and gives rise to a deceptive colour. (6.)- Trommer^s test with sulphate of copp&r and caustic potash. To the urine add a few drops of solution of sulphate of copper. To this add a little caustic pptash. This throws down a greenish blue precipitate of hydrated cupric oxide (CuOHjO), which is dissolved in excess (rf the caustic potfish, forming a blue liquid. Heat this by applying the flame of the lamp to the upper stratum of the fluid, and if sugar be present, a yellow, or orange, or red precipitate of cuprous oxide (CujO) will be formed, which will form a marked contrast to the blue liquid in the bottom of the test tube. This test depends on the fact that diabetic sugar has the property of reducing cupric oxide to cuprous oxide. It does not do so directly, but indirectly, by its decomposition by the action of caustic potash, into melassic acid, which has a strong tendency to unite with oxygen. Unfortunately, however, other substances, such as excess of urates, or the protein com- pounds oceasionaEy present in urine, have the same property, especially with the assistance of prolonged boiling, and it is consequently often difficult to detect minute traces by means of this test. If the cupric oxide be reduced to cuprous oxide in the cold, we may be sure diabetic sugar is present. (c.) FehUng's test with potassio-cupric tartrate (KjCuSCjHjOs). — The composition and mode of preparing this solution wiU be subsequently described when treating of the volumetrical estima- tion of sugar (p. 482). A few drops of it are added to the urine, and the upper stratum boiled. If sugar be present, it will reduce the cupric oxide in the alkaline tartrate to cuprous oxide, and DIABETIC SUGAR. 481 »iTe the same reaction as in Trommer's test. If freshly prepared, Fehling's solution will often detect minute traces of sugar, but it is liable to decomposition if kept for even a week, and DccasionaUy it gives uncertain results, even when the presence jf sugar has been ascertained by the other tests. (c^.) Boucher's test with nitrate of bismuth. — Add to the urine a,n equal volume of a solution of carbonate of soda (3 parts of water to 1 part of crystallised NajCOa), and afterwards a little trisnitrate of bismuth, and boU. If the white powder become dark, sugar is present, owing to the fact that sugar has the power of reducing the oxide of bismuth. If albumin be present in the urine, it must be first got rid of by boiliDg and filtration, because the sulphur of the albumin may readily form with the bismuth black sulphide of bismuth. (e.) Bichloride of tin test. — Moisten a few strips of merino in a solution of stannous-chloride, and dry in a water bath. On moistening one of these strips with diabetic urine, and hiolding it near the fire, a brownish-black colour wiU make its appearance. (/.) Fermentation test; — Ordinary yeast is mixed with water, and a long test-tube filled vrith the suspected urine, to which some of the yeast has been added. The tube is then inverted over a saucer containing the urine under examination, so that no air may enter, and the whole is set aside in a warm place. If sugar be present, it will be decomposed under the action of the ^east into carbonic acid and alcohol, and the gas will speedily jolleet in the upper part of the tube. Another mode of demon- jtrating the change is to conduct off the carbonic acid by a fine ;ube into lime-water, which of course at once becomes turbid 'rom the formation of insoluble carbonate of lime. Estimation of the wmownt of sugar. — This may be done in :wo ways : (1.) by a volumetrical process ; and (2.) by means )i an instrument termed a saccharimeter. 1. Volvmetric process for Biabetic Sugdr. This process is founded on the property already mentioned vhich diabetic sugar possesses of reducing cupric oxide to luprous oxide. If we use, therefore, a solution of potassio- lupric tartrate which contains, in a given volume, a quantity if 4supric oxide that is reduced by a certain quantity of sugar, ve can estimate the amount of sugar in solutions of unknown 482 PRA CTICAL PHYSIOLOGICAL CHEMISTR Y. strfogth by finding the volume required for the decompo- sition of a fixed quantity of copper solution. Prepouration of the copper solution {Fehling's solution). — 34"65 grammes of pure crystallised sulphate of copper are dissolved in about 160 grammes of water ; and a solution of 173 grammes of pure crystallised double tartrate of potash and soda is treated with from 600 to 700 grammes of caustic potash of 1-12 sp. gr. Into the latter solution the sulphate of copper solution is gra- dually poured. The clear mixture is then diluted up to a Utre. It has been found that 10 C. C. of this copper solution are reduced by exactly 0'05 gramme of diabetic sugar. In order to preserve the copper solution for a length of time, it is necessary to keep it in a dark place, in small stoppered glass bottles (containing 1 or 2 ounces). Process. — (1.) Mter the. urine. (2.) Dilute the urine with 20 times its bulk of distilled water, and place it in a burette. , (3.) DUute 10 C. 0. of standard solution (= '05 grammes of sugar) with 20 to 30 parts of distilled water, and place it in a porcelain capsule, under the burettei. (4.) Boil, gradually adding the diluted urine from the burette, until the cuprous oxide has been precipitated as a reddish powder, and the supernatant liquid has acquired a straw-yellow colour, not a trace of blue remaining. (5.) Filter the boiling fluid, and divide into three portions : a. 1st portion. — Add a few drops of hydrochloric acid, and afterwards a little, of a solution of sulphuretted hydro- gen. The absence of a black colour indicates that all the cupric oxide has been reduced. 6. 2nd portion, — Add a few drops of acetic acid, and then test with ferrocyanide of potassium. The absence of a reddish brown colour or precipitate indicates that all the cupric oxide has been reduced, c. 3rd portion. — To guard against the error of adding too much urine, add to this portion a few drops of the copper solution, and boU. If a trace of sugar be present, a reddish colour wiU appear in a short time. Example — Patient passes 15,000 C. C. of urine, 36 C. C. of dilute urine were required to reduce all the cupric into cuprous oxide in 10 C. C. of standard solution. How much sugar was passed? 10 0. 0. of S. S. require exactly "05 grammes of sugar THE SACCHARIMETER. 483 to effect the reduction. 36 C. C. of dilute urine=l'8 0. 0. of real urine (20 : 1 : : 36 ': 1"8) .'. 1'8 C. 0. of real urine contain ■05 gramme of sugar. Then I'S : -05 : : 15,000 : 416-6 grammes of sugar in 15,000 0. 0. of urine. 2. Estimation of Svga/r by the Saccharimeter. It is well known that diabetic sugar, in common with cane sugar, milk sugar, camphor, &c., have the property of rotating the plane of the vibrations of a ray of polarised light to the right (p. 142). It has been found also that the angle of deviation is in proportion to the length of the column through which the ray passes, or to the quantity of the substances contained in a column of given length. The saccharimeter of SoleU consists essentially of four parts : 1. A glass tube, for containing the fluid to be exa- mined, fitted into a brass case, and closed at both ends with plate- glass discs ground to fit water-tight, and kept tightly in their place by means of screw-caps. This is placed on a support be- tween a polarising and analysing apparatus. 2. A polarising' apparatus consisting of an achromatic calc-spar prism, having a small screen behind it (that is nearer the tube containing the solution) which intercepts one of the images ; and a double plate of quartz, one half being dextro, — and the other Isevro- rotatory. 3. An analysing apparatus, consisting of a quartz plate cut perpendicularly to its axis, and a doubly refracting prism, fitted into a small telescope ; and, 4. An apparatus, termed a com- pensator, which is placed between the quartz plate and doubly refracting prism just mentioned. This consists of two elongated quartz prisms cut perpendicular to the axis, each one being narrower at one end than at the other^ and set on two racks moved horizontally by a toothed pinion, so as to vary the thickness which the modified light has to traverse. One rack carries- a scale (tenths of a milimetre), the other a vernier (tenth of the tenth of a milimetre=l-100th of a milimetre) so as to measure the displacements of the prisms. Mode of using the saccharimeter. — -The instrument is placed before a bright light, the polarising apparatus being next the light. The tube is filled with distilled water, care being taken to exclude all bubbles of air, and is placed between the polarising and analysing apparatus. The eye is now directed to the telescope. If the instrument be correct, a disc of coloured light 8 484 PRACTICAL CHEMICAL PHYSIOLOGY. is seen, divided into two hemispheres by a very faint dark line, when the zeros of the vernier and scale coincide. The tube is now emptied of distilled water, carefully dried, and filled with urine which has been prepared by adding to it a solution of acetate of lead, and filtering. When the polarised light is allowed to pass through this stratum of urine containing diabetic sugar, the two hemispheres will now be found to have different colours, say one red and the other blue, and the object is now to bring back the two hemispheres to the same tiat by moving the compensating prisms, which is done by turning a screw attached to the pinion already mentioned. By thus moving the compensator, we pro- duce an inversion of the rotation of the ray of polarised light opposite to that produced by the liquid, and the displace- ment of the vernier gives the angle of deviation — ^the thickness of quartz corresponding to one division of the scale being known. The number of degrees on the scale is now read off, and each degree corresponds to a certain amount of sugar in a known quantity of urine. The instrument in use in the physio- logical laboratory of Edinburgh University, is so adjusted that each degree of the scale corresponds to "111 ounces of diabetic sugar in 50 ounces of urine. Thus, suppose a patient passes 200 ounces of urine in 24 hours. How much sugar is excreted ? The urine is examined as above, and it is found that the zero of the vernier is opposite 28 of the scale when the tints of the hemispheres are exactly the same. Then. 28 X "111 = 3'108 oz. in 50 oz. .-. 3108 X 4 = 12-432 oz. in 200 oz of sugar.* 3. Bile. — Urine containing bile has a peculiar greenish-black colour. The tests for bile acids and bile pigment have already been described at p. 458, while treating of bile. 4. i''a<.— Occasionally fat is found in the urine in the form of oil globules, but it js usually associated with fatty casts, indicat- ng an advanced condition of Bright's disease. 5. Chylous urine. — This urine is white, from the abundance of fatty molecules it contains. Sometimes albumin is present when it coagulates on cooling. It is probable in these cases there may be some abnormal communication between the lacteal system and the ureters or kidney. 6. Kiestein.—^h.% urine of pregnant women often shews a fat- * For a complete description and figure of - the saccharimeter, see Watt's Dictionary, of Chemistry— article, ** Light." Vol. iii. p. 674. Also Desplats et Garifel's Nouveai\ Elements de Physique Medicale. Paris, 1870, p. 396. SEDIMENTS OF URINE. 485 like scum on the surface, -which consists of crystals of triple phosphate, fat globules, and a granular matter of an albuminous nature called kiestein. When kept, it smells like old cheese. 7. Lactic asoK^.^-This acid is rarely found in urine, and its presence cannot be determined by any special test, but by the following mode of procedure : Evaporate fresh urine nearly to dryness, and treat the residue with a solution of oxalic acid in alcohol. Oxalates are thrown down, while the lactic acid remains in solution. This fluid is-then digested with litharge, evaporated to dryness, and an alcoholic solution of lactate of lead obtained. This, in turn, is decomposed by sulphuretted hydrogen, the sulphide of lead filtered off, and the fluid evapo- rated to a syrup. The syrup is now shaken up with ether, the etherial solution of lactic acid evaporated, and the lactic acid dissolved in water. The aqueous solution is now boiled with zinc oxide and the crystals of lactate of zinc are allowed to separate. 8. Acetic and hutyrio acids- — These are found only in decom- posing urine, and it is not important to detect or isolate them. 9. Sulphwretted hydrogen,. — This gas has rarely been found in urine. It may be readily detected by blackening a piece of paper dipped in a solution of acetate of lead and held over it. 10. Allantoin (PI. I. fig. 8). — Schottin has found this sub- stance in the urine of a man who had taken a large quantity of tannic acid. It has also been found in the urine of young children, but it is probable its presence is only temporary. Its detection is of no practical importance. 11. Leucin (PI. I. fig. 10). — This product has been found in the urine of individuals suffering from hepatic disorders. There is no chemical test for its presence, and it can only be identified in deposits by microscopical examination. It usually is found in the form of roundish, yellowish coloured balls, which consist in reality of masses of small needle-like crystals. 12. Tyrosin (PI. I. fig. 9). — It is formed under the same conditions as favour the production of leucin, and like it, can be identified only by means of the microscope. It consists of stel- late groups of long silky needles, not in balls or coloured, as is the case with leucin. Examination of the Sediments of TJrine. These may be conveniently divided into 1. those occurring 486 PRACTICAL CHEMICAL PHYSIOLOGY. in acid or alkaline urine, namely, uric acid, urates, phosphates, oxalates, and cystin ; 2. those found in alkaline urine only, namely, the ammoniaoo-magnesian, or triple phosphate, phos- phate of lime, and urate of ammonia ; and 3. organised deposits, namely, mucus, blood, pus, tube casts, spermatozoids, torulse, sarcinse, bacteria, vibriones, &c. 1, Deposits found ocaa^onally in acid or alkaline urine, usvMy in the former. ' (1.) Uric acid (PI. I. figs. 1, 2). — This appears as a yellow, reddish, or brown coloured sediment, consisting of Kttle masses of crystals. It assumes various crystalline forms : (a.) lozenge- shaped rhombs ; (6.) rectangular tables or prisms ; (c.) dumb- bell crystals ; and, (af.) spindle or barrel-shaped forms. (2.) Urates. — ^These appear when the urine is cold, if the salts are present in excess, because urates are much more soluble in hot water than in cold. Consequently, every deposit which disappears on heating consists of urates. They usually form a heavy precipitate at the' bottom of the glass, presenting an ill- defined upper border. The deposit may be white, or deeply tinted by the colouring matter of the urine. Such deposits have been termed " lateritious deposit," " brick-dust deposit," " critical deposit," and " purpurates." (a.) Urate of Soda is amorphous in urine, but when prepared artificially, by acting with uric acid on sodium phosphate, it forms acicular crystals (Plate I. fig. 3).- (5.) Urate of ammonia appears as an amor- phous granular sediment, or in the form of brown round balls covered with spines (Plate I. fig. 4 and fig. 18, h). (c.) Urate of lime is very rare, and appears as a white amorphous powder. (3.) Phosphates. — In acid urine, phosphates may be present in excess, when they appear as a cloudy precipitate, at once • soluble in a drop of nitric or hydrochloric acids. (4.) Oxalate of lime (Plate I. fig. 17). — This salt is easily detected by its characteristic crystals, which are octahedra (a.) or dumb bells (6.). It is not found as a distinct sediment, but exists as isolated crystals entangled in the mucous cloud with which it is usually associated. , (5.) Cystin (Plate I. fig. 6). — This is occasionally found as a sediment mixed with amorphous urates. Under the microscope its transparent, colourless, six-sided plates can scarcely be mis- taken. If it, exist in large quantity along with urates or phos- SEDIMENTS OF URINE. i 487 phates, or both, it may be distinguished from them by heating and adding acetic acid. The heating dissolves the urates, and the acid dissolves the phosphates, but neither have any effect on cystin. 2. Deposits found occasionoHly in alkaline wrine onfy. The formation of these has already been explained at p. 262 and p. 460. They are all dissolved on adding a few drops of nitric or hydrochloric acids. They are, (1.) Ammoniaoo-magnesian, or triple phosphate (Plate I. fig. 18). — This salt always exists in ammoniacal urine, and is easily recognised by its well-known crystalline forms. It is usually found iA variously modified six-sided crystals, some elongated (A), others nearly square (see to right of 6), some having sharp angles, while others have broad facets (a), and in very alkaline urine they appear as feathery crystals (c). (2.) Phosphate of lime. — It is usually an amorphous white powder, but occasionally it appears aggregated into rosette-like crystals. (3.) Urate of ammonia is always present in alkaline, and rarely in acid urine. It has been described above. (4.) Urate of lime is also occasionally found in alkaliae urine. 3. Organised deposits. These are mucus, blood, pus, tube oasts, spermatozoids, torulse, sarcinse, bacteria, vibriones, &c. (1.) Mucus. — When urine is left at rest, cloudy transparent floculi are seen, which consist of mucus entangling various forms of epithelial cells, derived from the urinary passages. If the supernatant liquid be ca^efu^y poured off, and acetic acid added to the mucus, it coagulates, forming delicate molecular fibres (Plate IV. fig. 1). (2.) Blood. — Urine containing blood has a peculiar smoky colour that the practised eye can readily detect, but the best test is to identify the blood corpuscles by means of the micro- scope. As a rule, the blood corpuscles are colourless and have lost their biconcave form, and are globular from the imbibition of water. Urine containing blood always contains =.& trace of albumia. (3.) Pus. — If there be a thickish yellow deposit at the bottom of the vessel, which has a stringy consistence, it usually consists 488 PRACTICAL CHEMICAL PHYSIOLOGY. of mucus containing pus. Pour off the supernatant fluid, and add to the deposit an equal bulk of caustic potash. It at once gelatinizes,- becoming so thick and tough that it cannot be poured from the test tube. When pus is present in small quantity, by means "of the microscope we can readily detect the pus corpuscles (Plate III. figs. 17 and 18). (4.) Tvhe casts. — These bodies are detected by allowing any sediment to fall to the bottom of a conical glass, removing a small portion of it with a fine pipette, placing a drop on a slide, covering it with a thin glass, and examining it with a power of 250 diam. linear. Tube casts are of various kinds, but they may be conveniently classified under the following: a. Fibrinous casts, often containing blood discs ; 6. Desquamative casts, con-, taining epithelial cells ; o. Granular or fatty casts, containing numerous oil globules, free, or in the epithelial cells (PI. XIII, figs. 12 and 13) ; d. Hyaline or waxy oasts, solid and trans- parent, or containing epithelial cells, granules, and free nuclei. (5.) Spermatozoids, torulce, sardnoe, bacteria, vibriones, So. — These, occasionally found in urine, may all be readily detected by their characteristic microscopical appearance. The gases of the urine are not of importance, and it is sufficient to state they ajre the same as those of the blood, and in variable proportion. CLINICAL EXAMINATION OF THE URINE. , The examination of a specimen of urine is to be made in the following manner : — 1. - Colour, whether pale from being dilute, dark from being concen- trated, dark or greenish frora presence of bile, smoky from blood. 2. /SmeK.— Fragrant from the existence of cystine, or sugar, &o., or f cetid from alkalinity. 3. Measure quantity passed, in 24 hours, and observe whether there is excess or diminution. 4. Specific gravity. — ^Take the specific gravity, if possible, of the mixed urine. Normal sp. gr. 1020. If high, suspect sugar ; if low, suspect albumin. 5. Reaction. — If acid, is it normally so or not ? If excessively acid, examine for crystals of uric acid. If alkaline, ascertain whether the alkali is fixed or volatile. 6. Heat. — Heat a portion in a test-tube. If a precipitate appear, it may be albumin or phosphates. Add a drop or two of nitric or hydro- chloric acids. If precipitate disso\\e, phosphates ; if not, albumim. If a deposit disappear on heating, we have urates. If it do not disappear. GENERAL EX AMIN A TIONOF ANIMAL SOLIDS. 489 add a drop of nitric acid. If now dissolved, we liave phosphates ; if not, cystin. 7. Bile.- — Test for bile pigment and bile acids, if necessary (p. 458). 8. Sugar. — Test for sugar, if necessary (p. 481). 9. Chlorides. — Add a drop of nitric acid, and then nitrate of silver, till a precipitate ceases to form. Thus estimate the amount of chlorides. 10. Microscope. — Examine for blood, pus, cystin, oxalate of lime, leucin, tyrosiu, tube casts, &c., by the microscope. Analysis of the F.a;cBS. As may be expected, the constitution of this excretion varies considerably from time to time. There are always present frag- ments of the undigested remnants of food, fatty matter, fatty acids, bile pigment, and soluble salts, chiefly alkaline phos- phates, the ammoniaco-magnesian or triple phosphate, with traces of sulphates and earthy phosphates. Undigested fragments are , readily separated by suspending them in water ; fatty matter may be taken up with ether and alcohol ; and the ash obtained by incineration will yield the mineral ingredients. Dr. Marcet states* that healthy human f aices contain an acid, excretoUc acid, and a substance called exereiin, both of which are soluble in ether. He obtains these substances by making an alcoholic extract of faeces. This deposits, after long standing, an " olive- coloured " acid, excretolic acid. The alcoholic solution is then treated with milk of lime which throws down e-vcretin, with other substances. The excretin is now separated from ttese by ether. It is probable that these substances may not be fixed compounds. (See pp. 271-2.) ,///. GENERAL QUALITATIVE EXAMINATION OF AN ANIMAL SOLID. The analysis of tissues and organs is attended with even greater difficulty than in the case of animal fluids. It is im- portant, if trustworthy results are desired, to operate upon at least 12 or 15 lbs. of the tissue. The following is the mode of procedure to be adopted : — f 1. Cut the tissue into small fragments, and allow it to macerate in cold water. Tilter. Add to the filtrate a con- centrated solution of barium hydrate to throw down phos- phates, sulphates, wic acid, and hypoxanthin. • Marcet, Phil. Trans. 1864, p. 266 ; and 1867, 403. t Watt's Dictionary of Chemistry, vol. i. p. 252. 490 PRACTICAL CHEMICAL PHYSIOLOGY. 2. Filter again and evaporate to a symp. During this operation, a film will coUect on the surface, consisting probably of harivm, carbonate or magnesium phosphate, and possibly of uric acid and hypoxanthin. 3. Allow crystals to separate out of the syrup, and probably they will consist of creatin. 4. Exta-act the mother liquid with alcohol and ether, and thus obtain lactates of potash and soda, inosite, creatinin, and levxdn. 5. Make a fresh extract by steeping a portion of the tissue in cQld water. Boil, and alhvminous matters will coagulate, and are to be separated by filtration. 6. Evaporate the filtrate to a syrup, and masses having a crystalline appearance may separate out. These consist of leudn. Tyrosin sometimes appears in the form of star-shaped groups of slender needles, which are insoluble in alcohol. 7. The mother liquids from the last-mentioned deposits con- tain volatile acids, lactic adds, &c. 8. Incinerate a known weight of the substance, weigh the ash, dissolve it in a little hydrochloric acid, and test the solution for inorganic adds and bases. Thus we obtain a general knowledge of the chejnical consti- ' tuents of the tissue under examination. Special processes are requisite for special tissues. IV. QUALITATIVE ANALYSIS OF SPECIAL ANIMAL SOLIDS. Under this head we shall treat of the analysis of muscle, white fibrous tissue, yellow elastic tissue, tooth, caEtilage, bone, the nervous system^ and lastly, of liver. Analysis op Mtjscle. 1. Reaction. — When quiescent muscle is tested with litmus paper, it is found to be neutral or slightly alkaline, but if the muscle be thrown for sometime into a state of tetanus by an interrupted current of electricity, it is iound to become acid. This is generally supposed to be due to the formation of sarco- lactic acid. ' ' 2. Kiihne's method of obtaining nmsde-plasma. — Kill two frogs, and inject into the blood vessels a weak solution of common ANALYSIS OF MUSCLE. 491 salt (1 per cent.), until all blood is removed. Then cut off all the muscle of the limbs, reduce it to fragments, and subject it to powerful pressure. A liquid is thus obtained, termed by Kiihne, muscle-plaima, which soon coagulates, resolving itself into a clot, called muscle clot or myosin, and a fluid, musde- serwn. 3. Exommoction of mvscle-serwn. — If this fluid be obtained in sufficient quantity, it will be found to contain three modifica- tions of albumin, each coagulating at a different temperature. When a portion of muscle-serum is heated to 30° C a coagula- tion takes place ; increase the heat to 45° C. and there is a further coagulation ; continue heating until 75° C. and another large amount of albumin will fall down. Muscle-serum also contains many excrementitious substances, resulting from the retrograde change of the tissues (Secondary Digestion, p. 239), such as creatin, creatinin, leucin, tyrosin, urea, uric acid, &c. These are to be distinguished and separated by the special pro- cesses and tests already fully described. 4. Examination of musde-clot or myosin (p. 10). — This wUl be found to be insoluble in water, ether, or alcohol, but it is very soluble in dilute acids or dilute alkalies, and especially so in a ten per cent, solution of common salt. If the common salt solution be added to distilled water, the myosin falls as a flaky precipitate. 5. Syntonin (p. 10). — Dissolve a portion of muscle-clot in a little weak hydrochloric acid. When this acid solution is added to water, a flaky precipitate is obtained, which is insoluble in a ten per cent, solution of common salt. This substance, which thus does not exhibit the characteristic reaction of myosin, has been termed by Kiihne Syntonin. He holds that syntonin does not exist as such in muscle, but is an artificial product obtained by the action of dilute acid on myosin. Syntonin may be prepared from muscle in the f oUowihg way : — Mince a piece of muscle and allow it to macerate in cold water until the water does not coagulate on boiling, shewing the absence of albumin. The macerated muscle is now treated with ten times its bulk of weak hydrochloric acid (•! per cent.) and left to stand for 24 hours. Neutralise with carbonate of soda, and a white and gelatinous precipitate will fall, consisting of syntonin. 6. Inosite. — The muscular substance of the heart contains a peculiar saccharine substance, isomeric with glucose, CjH^Oj, 492 PRACTICAL CHEMICAL PHYSIOLOGY. which may be separated as follows : — Macerate the heart in water, precipitate the phosphates with baryta-water, filter, eva- porate the filtrate, and allow creatin to separate out. Treat the mother liquid with dilute sulphuric acid, which will precipitate the baryta. Filter so as to remove the sulphate of barium. Shake up the liquid»with ether so long as anything is dissolved. Separate the ether by skimming, and mix with alcohol until a precipitate appears. This precipitate is sulphate of potash, which is now separated by carefully pouring oflf the supernatant fluid. Mix this. latter with more alcohol, and soon small oblique or tabular prisms of inosite will separate (p. 27). Seherer's test for inosite.* — The following is a test for the presence of inosite. To an aqueous solution, evaporated nearly to dryness, add a drop or two of nitric acid, moisten the residue with a few drops of ammonia and calcium chloride, again evaporate, and a rose-coloured substance remains. Incineration — Incinerate a given weight of muscle, and weigh the ash. Dissolve this in hydrochloric acid, and test for salts in the ordinary way.f Analysis of White Fibrous Tissue. 1. Basis of white fibrous tissue, gelatin. — This tissue shrinks much on being dried. When allowed to macerate in water^ or when boiled in water, a gelatinous mass is obtained, consist- ing of gelatin (p. 10). The jelly dissolves in hot water, and from the solution, alcohol precipitates a white clotted mass. 2. Incineration. — White fibrous tissue contains a very small amount of ioorganic matter, which can be obtained by in- cineration. Analysis of Yellow Elastic Tissue. l; JBasis of yellow elastic tissue, elaatin. — Boil a piece of the ligamentum nuchm of an ox with alcohol, then with water con- taining ten per cent, of sti'ong hydrochloric acid ; allow it to cool, and a yellowish, fibrous, and brittle mass is obtained, termed elastin. This substance is insoluble in water, alcohol, ether,' and acetic acid. It is dissolved by strong caustic potash. 2. Incineration. — There are more inorganic substances present * Scherer, Ann. Ch. Pharm., Ixiii. 322, Ixxxi. 375. t For details as to the chemical composition of " Flesh/' or butcher meat, see Watt's Dictionaiy of Chemistry, vol. ii. p. 661. ANALYSIS OF TOOTH, CARTILAGE, &» BONE. 493 in elastic tissue than in white fibrous tissue. The amount of these may be determined by incineration. AuALTsis OP Tooth. 1. Separation of organic bads. — By allowing fragments of teeth to macerate for three or four weeks in dilute hydrochloric acid (1 to 19 of water), a soft substance remains, which is pro- bably gelatin. This constitutes the organic basis of teeth, and is present in larger quantity in dentine than in enamel. 2. Incineration. — Bj' incinerating teeth, the organic matter is burnt off, and the ash will be found to consist chiefly of calcium phosphate, along with a much smaller quantity of calcium carbonate. Phosphate of magnesia, and a very minute trace of calcium fluoride, are also present. For examples of analyses of teeth, see p. 87. Analysis of Caetilagb and Bone. 1. Water in cartilage. — Weigh a piece of cartilage, allow it to dry in a hot-air chamber, and it will be found to have lost half its original weight. This is owing to the fact that cartilage consists largely of water. 2. Prepa/ration of chondrin (p. 11). — Boil a few of the cartilages of the ribs or joints with water for 48 hours, evaporate to a jelly, and wash the jelly with ether to free it from fat. The jelly is chondrin.' The various reactions of chondrin may now be demonstrated. It is soluble in boiling water, but insoluble in alcohol or ether. When any of the mineral acids are added to an aqueous solution, a precipitate is formed, which is redissolved in excess ; but the precipitate formed by carbonic, sulphurous, acetic, or tartaric acids, is not redissolved in excess. It should also be compared with gelatin, as foUows : — Reagent. Chondrin. Gelatin. Alum. Precipitate. No precipitate. - Acetate of lead. Precipitate. No precipitate. Sulphate of iron. Precipitate. No precipitate. Mercuric chloride. No precipitate. Precipitate. 3. Boiie. Ofganic basis of bone, ossein. — Allow fragments of bone to macerate for some time in dilute hydrochloric acid (1 to 19 of water). The calcium salts are dissolved, and a soft translucent mass remains, termed bone-cartilage or ossein. This substance resembles gelatin, but it differs from it in being 494 PRACTICAL CHEMICAL PHYSIOLOGY. insoluble in boUiag water. By prolonged boiling, however, ossein is converted into gelatin. 4. Inorganic salts of bmie. — The acid solution of bone salts may now be evaporated, and the examination of these inorganic salts conducted in the usual method. 5. Incineration. — First reduce the bone to fine powder, wash with water to remove soluble salts, and with ether to remt)ve fat. The powder is now incinerated (best of all in a mufl9.e) till it becomes white. A few drops of solution of carbonate of ammonia are now added to it to make up for the loss of any carbonic acid driven oflF from the carbonate of lime present in bone, and it is again incinerated. The diflference between the weights before and after ignition gives the amount of ossein. The ash is now to be analysed in the ordinary way. The results of numerous analyses of cartilage and bone will be found at pp. 90, 92, 93* , Analysis of the Nervous System. The chemical composition of nervous tissue is still very im- perfectly understood, and no definite mode of chemical analysis can be recommended. 1. Water and fat. — The amount of water may be ascertained by drying a certain definite weight, and wUl be represented by the loss in weight. The white matter of the nervous centres contains less water than the grey matter ; while the white, on the other hand, contains more fat than the grey matter. The amount of fat may be determined by acting upon nervous sub- stances with ether. Various physiological chemists have detected in nervous matter the following substances : leucin, uric acid,, xanthin, inosite, creatin, creatinin, formic, and acetic acids. 2. Cerebrie add. — This is a fatty acid supposed to exist in the brain. Cut brain substance into thin slices, act upon it with boiling alcohol to remove water, press it, digest with cold, then with warm ether, distil off the ether, and digest with much more ether. We have now cerebrate of soda mixed with phos- phate of lime, &c. Digest it in boiling absolut^ alcohol acidu- lated with sulphuric acid. We thus obtain an alcoholic solution of cerebrie acid. When this is evaporated, the acid is deposited • For analyses of bones of difEerent animals, see article "Bone" in Watt's Bictionary of Chemistry, vol. i. page 619. ANALYSIS OF THE LIVER. 495 as a -white crystalline substance. It is doubtful if this acid be a constant ingredient, and probably it is a substance produced artificially during the chemical process. Other substances have been found in brain, termed cerebrin, cerebrol, and eerebrote ; but it is probable they are one and the same substance. 3. Protagon. — This is the name of a substance supposed to exist in brain. According to Liebreich, it is the principal con- stituent of nervous tissue, (a.) Eeduce brain substance to a pulp, and act upon this with water and ether at 0° C. From the remaining substance extract the protagon by 85 per cent, alcohol at 45°. Cool the alcoholic solution to 0° C, and a pre- cipitate is formed which, on being examined microscopically, is found to consist of bundles of crystals. (6.) This substance may aisp be prepared in a somewhat dif- ferent form from yoke of egg. Beat up very thoroughly the yoke of an egg in 2 ounces of absolute alcohol. Boil carefully and filter while hot. Allow the filtrate to drop upon a flat and cold porcelain plate, when a yellowish non-orystaUine deposit will be found, consisting of protagon. The remarkable reactions of this substance are described at page 45. 4. Oleo-phosphorio acid. — This is a fatty acid found in the brain ; it may be prepared as foUows : — Beat up brain substance to a thin pulp with water, heat the mixture to the boiling point, and act on the coagulum formed with boiling alcohol. This extract is filtered while hot, and deposits cholestrin, cerebrin, and oleo- phosphoric acid, united with alkalies. Act upon this with cold ether, which takes up oleo-phosphate of soda. Evaporate the ethereal solution, decompose the oleo-phosphate by a few drops of dilute hydrochloric acid, dissolve the residue in boiling alcohol, and the oleo-phosphoric acid is deposited when it cools. It is a gummy or fatty yellowish substance, easily de- composed into phosphoric acid, and one of the higher fatty acids. Analysis of the Liver. It is well known that the liver contains a substance termed glycogen, isomeric with starch, CeHuOs (p. 25). It may be pre- pared from the liver, as f ollows : Bernard's method. — Cut a piece of liver into small portions, boil it for an hour in water, and allow the hot decoction to filter into glacial acetic acid. Nearly pure glycogen is thrown down, the albuminous substances remaining in solution. It is precipitated from its aqueous 496 PRACTICAL HISTOLOGICAL PHYSIOLOGY. solution by animal charcoal, and is usually quite insoluble in alcohol. It is important to observe that dilute mineral acids, diastase, and the peculiar nitrogenous ferments found in the blood, saliva, liver, and pancreas, readily convert glycogen into diabetic sugar, CsHjjO,,. It is probable a change of this' kind occurs with great rapidity on death, for we have found that a decoction of a liver removed from a rabbit or mouse just kiUed, always gives a characteristic reaction with any of the tests for sugar. If, however, a portion of the same liver be kept for several hours, and a decoction then made, a much more decided reaction will be obtained. (See p. 251.) In conclusion, it may safely be asserted that chemical phy- siology is still in its infancy. It is a diflBcult field of labour, both from the complex constitution, as well as from the insta- bility of many of the substances to be examined. Nor must we forget that the chemist can analyse only dead tissues and fluids, not living tissues, and many of the substances which are ob- tained by chemical processes in the laboratory do not exist as such in the living body. PRACTICAL HISTOLOGICAL PHYSIOLOGY. This subject can only be prosecuted with the aid of an achro- matic microscope, the construction and mode of employment of which instrument must be first understood. HiSTORT OP THE MICROSCOPE. A microscope (from ^ixjos, small, and irxsiiTM, to see) may be defined, an instrument which is capable of making small objects appear larger than they do to the naked eye. In this sense, it applies to any instrument, of whatever contrivance, capable of fulfilling this condition ; and if we accept this definition, various reasons have been adduced to shew that the microscope was known to the ancients. Spectacles, it is said, were in use among . the Greeks and Eomans ; and as the glasses of these were made of difierent convexities, and, consequently, of different magnify- ing powers, it is natural to suppose that they must have been acquainted with the property possessed by the lens, of enlarging .small objects. Various passages also occur in the works of HISTORY OF THE MICROSCOPE. 497 Jamblichiis, Pliny, Plutarch, Seneca, and others, which lead to a similar conclusion. Thus, Seneca observes : " Letters, though minute and obscure, appear larger and clearer through a glass bubble filled with water." Now, this glass bubble filled with water is sold by pedlars and others to the vulgar at the present time, in order to magnify objects. The compound microscope appears to have been constructed in the early part of the seventeenth century. Both Holland and Italy have claimed the honour of producing its inventor. WiUiam Borelli attributes its construction to one Zacharias Jansen of Middleburgh in the Low Countries, who, with his son John, according to this author, made his first compound microscope so early as 1590. It is stated that either he or his son presented one of his instruments to the Archduke Charles of Austria, who, in turn, gave it to Cornelius Drebbel, a Dutch alchemist, who subsequently became astronomer to James I. of England. He it was who first brought the instrument to Lon- don in 1619, where it was seen by William Borelli and other scientific individuals. It is well known that Drebbel made microscopes in London in 1621, and generally passed for their inventor. On the other hand, Francis f'ontana, a Neapolitan, states, that he invented the instrument in 1618, and gave a description of it in his " Novee terrestrium et cselestium observationes." It would appear, however, that although Drebbel and Fontana disputed concerning the origin of this instrument, the honour of inventing it, so far as our present knowledge extends, belongs to Jansen. The microscope brought by Drebbel to London is thus described by Adams, who observes : " It is possible that this instrument of Drebbel's was not strictly what is now meant by a microscope, but was rather a kind of microscopic telescope, something similar in principle to that lately described by Mr .^pinus in a letter to the Academy of Sciences at Petersburgh, It was formed of a copper tube, six feet long, and one inch, iu diameter, supported by three brass pillars in the shape of dol- phins. These were fixed to a base of ebony, on which the objects to be viewed by the microsope were also placed."* Thei improvement of the microscope made much less rapid progress than that of the telescope. The great utility of the * Adams on the Microscope, p. 3. 498 PRACTICAL HISTOLOGICAL PHYSIOLOGY. latter, indeed, appears to have been early appreciated, while the microscope was for a long time only regarded as a means of SEttisfying curiosity. Thus it was merely looked upon as an expensive toy, and kept by the rich in their cabinets as a source of amusement. At a later period, however, it was found sus- ceptible of adding much to our knowledge of the natural sciences ; and no sooner was this perceived, than the most cele- brated artists, mechanics, geometricians, and natural philoso- phers paid great attention to its improvement. For a long time, however, they were baffled by the difficulties of the undertaking, and during this period naturalists, for the most part, employed the simple microscope. Thus, some of the most important discoveries in science have been made by means of a single biconvex lens, and the laborious and brilliant researches of Leuwenhoeek, Swammerdam, Lyonet, Ellis, and others were thus accomplished. The inconveniences of the simple microscope, however, are con- siderable. Thus, when capable of magnifying largely, the field of vision is very limited, and there is great difficulty in ad- justing the focus. Leuwenhoeek had a separate lens especially ■ adapted to one or two objects, and always had several hundreds at his disposal. • The imperfections of the compound microscope, on the other hand, were at that time very great, and must have appeared insurmountable. Thus, from its peculiar construction, the rays of light were readily decomposed, and circles of diflferent colours surrounded or tinged the object, constituting the aber- ration of refrangibility. The form of the object was also dis- torted on account of the aberration of sphericity. Opaque objects could not be seen from the absence of light, and very transparent ones could not be examined from its excess. But gradually all these diflferent obstacles were overcome by patience and labour. The details connected with these, how- ever, we cannot enter into. Suffice it to say, that to Lieberkiihn we are indebted for the means of examining opaque objects by means of a reflector ; to the diaphragm of Le Bailhf, for a convenient mode of modifying an excess of light. Achromatic instruments were constructed principally through the ingenuity and labours of Euler, DoUand, Frauenhofer, Selligue, Amici, TuUey, and Vincent, and Charles Chevalier, and may be said to have been perfected only during the last thirty years. OPTICAL PRINCIPLES. . 499 The object of the optician at present engaged in manufactur- ing this instrument is to construct a microscope which ■will admit of an easy and universal application, and possess the power of magnifying largely, combined with clearness and distinctness of the image. The instruments now constructed by Ploesel in Vienna, Frauenhofer in Munich, Schiek of Berlin, Hartnach and Nachet in Paris, and Powell, Boss, and Smith in London, if they have not reached perfection, certainly approach very near it, and permit the most minute details of structure to be examined with ease, even when magnified largely.* OPTicAii Pbinciplbs on which the Microscope is CONSTRDCTBD. The optical principle on which every microscope is constructed is, that rays of light passing through a lens are more or less refracted, that is, are bent out of the straight line. This has already been fully explained at page 135. Theory of mla/rgement. — The theory of a simple bi-convex lens will be understood by referring to Plate XXI. fig. 3. Here we have a convex lens interposed between the eye and a small object ab. If a 6 be very close to the eye, the rays passing from it would diverge so far that the optical arrangements of the eye itself would fail to briiig them to a focus on the retina, because the eye is adapted to receive and bring to a focus rays which are parallel or but slightly divergent. But when the lens xy i& placed between the eye and the object, the rays ax, by, are so refracted by the lens as to come to a focus on the retina. Thus a well-defined picture or image is formed. But the rays now enter the eye at a greatly increased angle, and, conse- quently, the small object a b appears increased in size to a' V . It will be evident also, that if the lens xy were more convex the effect would be further increased, as the refraction would be greater, and the object a b would be seen still larger than a' h . * To no one is science more deeply indebted than to the late Mr Oberhseuaer of Paris. He it was who first made good microscopes cheap, and brought them within the reach of the poorest scientific cultivator. Thousands of his instruments have been scattered over the world, and by their aid most of the facts on which the science of histology is founded were discovered. His nephew, M. Hartnach, continues his system with the like success. 9 Soo PRACTICAL HISTOLOGICAL PHYSIOLOGY. A simple lens is termed a dmple miaroscope. The same theory applies to increased convexity of the lenses in the eye-piece, only it is the image which is transmitted by the objective (p. 507) that is then magnified. It foUows that any imperfection it possesses will be magnified also, so that the excellence of the objective is always the chief consideration in obtaining magnifying power. A third method of obtaining enlarge- ment is by elongation of the tube, which, by causing greater divergence of the rays, also increases the apparent size of the object. ' ' Faults of simple lenses and their corrections. — Every simple lens has two faults or optical imperfections — 1st, that of spheri- cal aberration, and 2nd, that of chromatic aberration^ The modes of remedying these faults cannot be understood without an acquaintance with their causes. Spherical aberration. (See p. 137.) — By referring to Plate XXI. fig. 4, it will be seen that all the rays of light passing through a, convex lens do not come to the same focus in conse- quence of the refraction being necessarily greater at the circum- ference than towards the centre. Thus the rays a and c, as they impinge upon the glass at a greater angle, come to a focus at A, while the rays b, which are nearer the centre, come to a focus at B. This is owing to the unequal refraction of the rays, the rays a and b, passing through the margin of the lens being more refracted than those of 6 passing through its centre. Con- sequently, an image formed on the retina either at A or B would not only be indistinct and imperfect, but curved according to the convexity of the lens. There are various methods adopted for correcting spherical aberration. 1. By using a double convex lens the radii of which are as 1 to 6, with its most convex face turned towards the object. 2. By using a stop in the eye-piece, which is a plate with a round aperture interposed between the lens and the eye (Fig. 1, c), so as to cut off the rays a c (Kg. 4), and receive only those coming from b. Such an arrangement is used in all compound microscopes. 3. By using combinations of lenses, so disposed that the aberration of the one wUl correct the aberration of the other. Tius the aberration of one plano-concave lens may be made to correct that of another, so that all the rays will be brought to one focus, as in the eye-piece of Huyghens. tChis arrangement OPTICAL PRINCIPLES. 501 will be described after we have considered the other imperfect tion of simple lenses, namely : Chromatic aberration. — When an object is examined by a simple lens it will be found surrounded by rings of colour — red, orange, yellow, and so on. This appearance arises from the fact that the lens acts as a prism (see p. 140), and decomposes or disperses the ray of white light into its constituent coloured rays— red, orange, yellow, green, blue, purple, and violet. The most refrangible of these rays are the violet, the least the red, while those between these two colours possess different degrees of refrangibUity. On referring to Plate XXI. fig 2, it will be seen that the rays of white light a x and c y are decomposed into the violet coloured rays x A and y A, and into the red rays X T and y T, the intermediate coloured rays, purple, blue, green, yellow, and orange not being represented in the diagram: In consequence of the great refrangibUity of the violet rays, they are brought to a focus at A, while the least refrangible rays, the red, meet at T, a point farther from the lens than A. If the retina were situated at A, a coloured image would be seen, the centre violet, then purple, blue, green, yellow, and orange, while the margin would be red. On the other hand, if the retina were at T, a coloured image having the centre red and the margin violet would be the result. These fringes of colour seriously interfere with a correct interpretation of microscopic appear- ances, and must be got rid of. This is effected 1. By the compound aorvmatic lens. — This consists essentially of a bi-convex lens of crown glass and a plano-concave lens of flint glass carefully adjusted and cemented together, as seen in PI. XXI. fig. 1, fl, /, g, and figs. 5, a, and 6. The principle is, that as the dispersive power of the flint glass is so much greater than that of the crown glass, the one exactly corrects the other, and we thus have dispersion destroyed without destroying the refraction. When this is accomplished, we have achromatism, or the refrac- tion of light without decomposition. At the same time, the refractive power of the two kinds of glass being also so different as exactly to neutralise each other's defects, we remove spherical aberration by this arrangement of lenses, and we thus obtain a distinct image on the retina by all the rays being brought to a focus without dispersion. It has been found best to use a com- bination of three such double lenses. Fig. 1, e,/, g, and Fig. 5, a. In Hartnach's and Nachet's piicroscopes, each pair of these are S02 PRACTICAL HISTOLOGICAL PHYSIOLOGY. fitted into small rings of brass which are screwed the one before the other. In the objectives of the London makers, a section of one of which is shewn (Plate XXI. fig. 6), the front pair can be approximated to the other two pairs, or the distance between increased so as to adjust the lenses for examining objects with or without a covering glass. Object glasses having this adjustment, are constructed as follows (Plate XXI. fig. 6). The two higher achromatic lenses are fixed in the end of the tube B ; upon this slides a cylinder A A, carrying at the lower end a third lens, which, by turning the screwed ring CC, may be approximated to, or separated from, the other two lenses. These lenses can thus be so adjusted that the positive aberration of the anterior lens corrects the negative aberration of the two posterior, and also the aberration produced by even a thin covering glass when one is used. This improve- ment we owe to Mr Eoss, the eminent optician of London. 2. The eye-piece of Huyghens. — It consists (PI. XXI. fig. 1, c c,b d) of two plano-convex lenses, b d, with their plane sides towards the eye. These are placed, with regard to each other, at a distance equal to half the sum of their focal lengths. The upper one, 6, is termed the eye-glass, the lower, d, ih.e field- glass. A stop or diaphragm is placed at c c in the visual focus of the eye-glass, which is the same position as that where the image produced by the field-glass d is formed. Huyghens made this arrangement of lenses to correct spherical aberration merely ; but Boscovitch shewed that it also corrected chromatic aberra- tion. This correction is now completely attained in all good Huyghenian eye-pieces. The rays of light passing into the eye- piece by the margin of the convex surface of the field-glass d, are decomposed so as to form two coloured images near the position of the eye-glass, the upper one blue and the lower red. The eye-glass, in its turn, would then magnify these so as to pro- duce two secondary-coloured images near y x. These coloured images are combined so as to form a colourless image y x : 1st, by using a stop c c, which intercepts the rays passing through the margin of the lens ; and 2d, by having the eye-glass slightly over corrected for chromatic aberration, so that its focus would ■ be shorter for blue rays than for red rays by just the difi^erence in the place of the images formed at y. x. Thus the rays enter the eye through the eye-glass in a parallel direction, and produce a picture free from colour. MECHANICAL PARTS OF THE MICROSCOPE. 503 Arrangement of lenses. — A section of a compound microscope is seen in Plate XXI. fig. 1. At the lower end of the tuhe there are one or more combinations of achromatic lenses, termed the objeative, e, /, g, and at the other the eye-piece, e c, b d. An inverted image of a; y, a small object placed under the objective, is made and inverted in the tube of the microscope in front of d, the field-glass ; this image is magnified and again inverted hjd, so as to form an image beneath 6, the eye-glass, which last image is a third time inverted by the eye-glass b, which also directs the rays of light into the eye a, so as to form a distinct image on the retina. Thus the image on the retina is reversed as regards the object, a fact to be remem- bered in making microscopical observations. Modes of increasing magnifying power. — ^This may be done in one or more of three ways : 1st, by increasing the length of the tube ; 2d, by increasing the power of the eye-piece ; and 3d, by using a higher objective. The objection common to all of these arrangements is, that while we increase the power we lose light. In the first instance we lose light by distributing it over a greater length of tube ; in the second, we find that while we gain in power we lose brightness and definition, because any faults of the lens are of course iutensified by the eye-piece. By using higher objectives, if th«y are good we obtain clearness of definition, with a sacrifice of light by dispersion of the rays. This, however, can be diminished by illumination, so construct- ing the lenses as. to permit the passage of a large amount of light. Such n, lens is said to have a, large angle of aperture. (See Fig. 5", where a b cia the angle of aperture.) All three modes of enlargement, viz., by the objective, by the eye-piece, and by elongation of the tube, are taken advantage pf in the best instruments, and are useful within certain limits, as in the model I recommend, now manufactured by Hartnach. CONSTBUCTION OF THE MiCEOSCOPB. A microscope may be divided into mechanical and optical parts. Mechanical parts. — These determine its general form and ap- pearance. Of the numerous models which have been invented, the one figured (PI. XXI. fig. 8), one-eighth its real size, appears to me the most useful for all the purposes of the physiologist and medical practitioner. It was suggested by me to the late Mr 504 PRACTICAL HISTOLOGICAL PHYSIOLOGY. Oberhseuser, and manufactured by him with his accustomed ingenuity. (6.) The body consists of a telescope tube, eight inches in length, held by a split tube (c), three inches long. It may be elevated and depressed with great readiness with a cork- screw movement, communicated to it by the hand, and this constitutes the coarse adjustment. It is attached to a cross bar and pillar, at the lower portion of which last, very conveniently placed for the hand of the observer, is the fine adjustment (/). The stage {d) is three inches broad, and two and a half inches deep, strong and solid, with a circular diaphragm below it. The height enables the observer to rest his two hands edge-ways on each side, andi-to manipulate objects on its surface with the thumbs and fore fingers.- The base of the instrument is heavily loaded with lead to give it the necessary steadiness. This form of microscope possesses all the mechanical qualities required in such an instrument. These are — 1st, steadiness ; 2d, power of easy adjustment ; 3d,' facility for observation and demonstration ; and 4th, portability. 1. Steobdiness. — It must be evident that if the stage of the microscope possesses any sensible vibration, minute objects, when magnified highly, so far from being stationary, may be thrown altogether out of the field of view. Nothing contributes more to the comfort of an observer than this quality of a micro- scope, and great pains have been taken to produce it. In the large London instruments this end has been admirably attained (Plate XXL fig. 7), but at so much cost and increase of bulk as to render it almost useless. In the small model I have recom- mended, all the steadiness required is present in the most con- venient form. 2. Power of easy adjustment. — It is a matter of great import- ance to those who use the instrument much, and work with it for hours together, that the adjustments should work easily and rapidly, and be placed in convenient situations. Nothing can be more commodious than the manner in which these ends are arrived at in the model figured. By insertion of the body of the instrument (6) within a split tube (c), you may, by a spiral movement, elevate and depress it with the greatest rapidity, and even remove it altogether if necessary. The necessity of continually turning the large screws affixed to most microscopes (Fig. 7, d), becomes fatiguing in the extreme. Then the fine adjustment (/) placed conveniently ' behind the microscope, MECHANICAL PARTS OF THE MICROSCOPE. 505 near the hand -which rests on the table, is in the very beat posi- tion ; whereas, in some London instruments, it is placed on the top of the pillar, so that you must raise your hand and arm every time it is touched (Fig 7, f). In other London instruments, it is placed in front of the body, so that you must stretch out the arm and twist the wrist to get at it. No one could work long with so inconvenient a contrivance. 3. FadMiy for observation and demonstration. — For facility of observation and demonstration, it is necessary that the instru- ment should be of a convenient height, and that the stage on which the objects are placed should be easily accessible. Here, again, nothing can be more commodious than the microscope I have recommended, for, when it is placed on the table, its height is almost on a level with the eye, and we can look through it for hours without the slightest fatigue. On the other hand, the stage (fl!) is elevated just so much as enables the two hands, resting on their external edges, to manipulate with facility all kinds of objects placed upon it. The large London instruments are so high as to render it necessary to stand up to see through them. To obviate this disadvantage,, a movement is given to the body, by which it can be depressed to any angle (Plate XXL fig. 7). But this movement renders the stage oblique, and removes it to a distance, where it becomes very inconvenient to manipulate on its surface. To obviate this difficulty, the stage itself has been rendered moveable in various ways by diflferent screws (Fig. 7), so that in this way complexity has been added to complexity, until a mass of brass work and screws is accumu- lated, to the advantage of the, optician, but to the perplexity and fatigue of the observer. But by no contrivance is it pos- sible to avoid the aching arms which such a position of the stage invariably produces in those who work with such a cumbrous machine for any length of time. Hartnach has recently placed a joint on his small microscopes, which, when they are bent, brings the eye-piece opposite the observer's stomach. Except for the purpose of drawing with a camera it is utterly useless. 4. Portahility. — This is a property which should by no means be overlooked in instruments that are intended more for utility than ornament. A medical man is often called upon to verify facts in various places ; at his own house, at an hospital, at the bed-side of his patient, or at a private post-mortem examination. It is under such circumstances that the value of portability is So6 PRACTICAL HISTOLOGICAL PHYSIOLOGY. Teeognised. The large London instiiiments require an equipage or a porter to transport them from place to place ; even the putting them in and out of the large boxes ot cabinets that are buUt around them, is a matter of labour. In short, notwith- standing the splendour of the screws, the glittering of the brass, and the fine workmanship (Plate XXI. fig. 7), there can be little doubt that, on the whole, they are very clumsy affairs. There are many occasions on which a medical man may find it useful to carry a microscope with him, especially in the case of post-mortem examinations. Many attempts have been made to construct a pocket microscope ; and for the purposes above alluded to, I myself caused one to be constructed some years ago which, with its case, resembled a small pocket telescope: Dr Gruby of Paris, however, has planned the most ingenious instru- ment of this kind, which possesses most of the properties we have enumerated, and will be found very useful for those accus- tomed to microscopic manipulation. It is contained in a case the size Of an ordinary snuff-box, and possesses all the con- veniences of the larger instruments, with various lenses, a micrometer, slips of glass, needle, knife, and forceps in that small compass.* It is deficient in steadiness, however, a fault which has been removed by a similar instrument made by Nachet of Paris, the box of which is made of brass (Plate XXI. figs. 9 and 10), and which I can strongly recommend for its usefulness and excellence. There is a general feeling among the public Jthat the larger a microscope is, the more it must magnify ; but this is an error. A very imposing mass of brass -njprk and mechanical complexity is no guarantee that you will see objects better, or what is of more consequence, become good observers. On the contrary, the more unwieldy the instrument, the less disposed will you be to use it. Besides, the habitual employment of artificial methods of moving about the object, as by the screws of a moveable stage, wiU prevent your acquiring that dexterous use of your fingers and accuracy of manipulation which are at all times so useful. Nothing, indeed, can be more amusing than to see a man twisting his screws, pushing his heavy awkward stage about, and laboriously wasting time to find a minute object which another can do in a moment, and without fatigue, by the • For a representation of this instrument, see my Clinical Medicine, fifth edition, pp. 97 and 80. ' OPTICAL PARTS OF THE MICROSCOPE. 507 simple use of his fingers. But perhaps you will consider the weightiest objection to the large instruments is the expense they necessitate, — the cost being necessarily in proportion to the amount of brass and mechanical labour employed upon them. If, then, you have to choose between a complex model and a simple one, I strongly advise you, as a matter of real economy, to choose the latter. We have next to speak of the optical parts of microscopes, which are certainly much more important than the mechanical . ones— for everything depends upon obtaining a clear and dis- tinct image of the object examined. Under this head we may describe the objective, the eye-piece, and methods of illumination. 1. The Ghjective, or series of Achromatic Lenses, is that part of the optical portion of a microscope which is placed at the bottom of the tube or body, and is. near the object to be examined. . This may be considered the most important part of the instrument, and the greatest pains have been taken by all opticians. in the manufacture of good lenses. It is here, I consider, that the London opticians are pre-eminent, for I am not aware that in any part of the world more perfect objectives have been manufactured than the eighth of an inch by Smith, the twelfth of an inch by Boss, and the sixteenth of an inch by Powell. The latter has also manufactured the twenty-fifth of an inch, which I have used with advantage. And Dr Beale tells us he has made for him a lense of one-fiftieth of an inch focus. But when we come down to one-fourth of an inch, which is by far the most useful objective for histological and medical pur- poses, the superiority of the London opticians is very slight, if any. A,t this magnifying power the compound lenses of Hart-, nach and Nachet of Paris ; Schick and Pistoi; of Berliia ; Prauenhof er of Munich, and Ploesel of Vienna, may be employed with the greatest confidence, and it may be "said that, by far the largest number of important discoveries in soieVice have I been made through their employment. The Parisian lenses ^n addition, have one great advantage, namely, their cheapness. The London opticians have succeeded in combining thei l^nsfe^ ; 1 of their objectives so as to obtain a large field or vision, with as little loss of light as possible (Plate XXI. figs. 5, a, and 6). These qualities are valuable in the lower inaguifying lenses during the examination of opaque objects, and in the higher So8 PRACTICAL HISTOLOGICAL PHYSIOLOGY. ones when observing transparent objects by transmitted light. But in the lenses of medium power, such as the one-fourth of an inch, those of Hartnach and of other continental makers are equally good. In recent times so-called immersion lenses have been employed with advantage, that is, lenses so made that they may be depressed in a drop of water placed upon .the covering glass. The object is thereby more highly illuminated and the focal, distance increased. The highest powers can in this way be obtained at a much more reasonable price, from Hartnach, thaa from the London makers, and they are excellent. For the above reasons, as well as from considerable experience in the use of many kinds of microscopes by different manufac- turers, I am satisfied that the best lens you can employ for ordinary purposes is Hartnach's No. 7, which corresponds to what is called in England the quarter of an inch. For low powers you may have Hartnach's No. 3, or the one-inch lens of the London opticians. For all the wants of the medical man these will be suificent. Occasionally the higher lenses may be required by the physiologist, as during the examination of the ultimate fibrillae of muscle. These, by whoever made, may be attached to the model we have recommended by means of a brass screw made on purpose. 2. T}m Eye-piece. — This is that portion of the optical apparatus which is placed at the upper end of the tube or body, and is near the eye of the observer (Fig. 8, a). While the objective magnifies the object itself, the eye-piece only magnifies the image transmitted from below. Hence, as a source of magnify- ing power, it is inferior to the lens ; and when this possesses any defects, these are enlarged by the eye-piece. Two eye- pieces are/ al^ that is necessary with the model I have recom- mended, ariand's electromotor or induction apparatus. — ' The production of electricity by inductiot has been described at p. 155. A side view of the instrument is seen in PI. XIX. fig. 1, and an end view in Fig. 2. It consists of a primary coil, El, of thick copper wire, insulated with silk, and of a secondary coU, E2, consisting of numerous coUs of fine copper wire, also well insulated. The centre of the primary coil, Ei, contains a bundle of thin iron wires, which are rendered magnetic during the passage of the electrical current round the primary coil, and thus increase the amount and intensity of the induced current obtained from the secondary coil (Fig. 2 S). The primary coil is firmly fixed ; but the secondary one slides in a double groove in the board B B, and this board has a hinge which allows one- half to lie under the other, as depicted in Fig. 1. "When, however, we wish to increase to a greater extent the distance between the primary and secondary coils, we unloose a hook, seen on the board iUnder Ej, and fold out the board to double the original length. A scale, divided into centimetres and milli- metres, is pasted on one side of the Upper surface of the board, and we can thus, in comparative experiments, carefuUy gradu- ate the distance between the two coils. The nearer the coils APPARATUS. 527 are to each other the more intense the shock, and vice versa. The shock of induced electricaty can, however, only he obtained at the moment of opening and at the moment of closing the prim- ary current. This regular opening and closing of the primary circuit is effected by an apparatus placed at the end of the instru- ment, termed Wagner amd Nee/'s hammer. This apparatus will be understood by referring to Plate XIX. fig. 2. Here we have K representing the battery from which voltaic electricity is derived. It passes from the positive pole in the direction of the small arrow to the brass pillar a. Having run up this pillar, it goes along a steel spring seen over S, and as the elas- ticity of the spring keeps a small square bit of platinum on its upper surface in apposition to the platinum point of the screw Si the current passes into Si from thence by a copper wire to Sii, and from thence, as indicated by the small arrow -^ >, round the wire of the primary coil, Ei- It now goes from Ej, as indicated by the lower small arrow, to a small U-shaped piece of soft iron surrounded by the wire, and thus converts it into an electro-magnet, which draws down the armature of soft iron (the hammer) on the free end of the spring, and thus the contact between the back of the latter and the screw point Si is broken. When this happens, the primary current is broken at Si, the electro-magnet loses its magnetism, releases the spring, which flies up by its elasticity, and again establishes the current. Thus by the alternate breaking and forming of the primary current, a secondary current is induced ia E2, which has no connection by wire with Ei. It is the secondary current (Faradic electricity) which is used in many physiological experiments. Helmkolt^s modification of the apparatus. — ^When a muscle or nerve is irritated by an induced current from the secondary coil, E2, it receives a rapid series of shocks, because the hammer acts with great rapidity. If the hammer acted slowly, so that we could distinguish between the effect of the opening shock and the closing shock, it would be found that the effect is much greater in the case of the foi'mer. The reason of this is that the open- ing shock is more rapid in its course, its velocity rising rapidly from zero to a maximum. If then we can retard the opening shock, we may render it equal to the closing one. This Helmholtz has accomplished by an arrangement in which he makes the hammer, when attracted by the electrormagnet, S28 PRACTICAL EXPERIMENTAL PHYSIOLOGY. not open the primary circuit, as in the apparatus just described, but close an accessory circuit so as to weaken the primary one. Tlie accessory circuit (PL XIX. fig, 2) is ^ running from a to Sill. Beneath the centre of the steel spring is a middle pillar, having in its base the binding screw x to which a wire in con- nection with the negative pole of the battery is attached* The accessory circuit, a Sm Su Ri, continued in the direction, of the lower arrow down an electro-magnetic pillar to another arrow which leads to *, S, and a, is closed when the steel spring is in contact with S. When this is the case, the primary circuit is so weakened that the electro-magnet loses its mag- netism, and the spring flies up, the primaiy circuit being now formed and the accessory broken. By this arrangement the velocities of the two shocks are equal, and the apparatus is better adapted foir careful physiological research, 3. Du Bois-ReT/moncPs Icey (Plate XX. fig. 4). — When we wish to open or close a circuit, we may do so either by detaching or fixing the wires by binding screws, or by using small cups filled with clean mercury, into which the ends of the wires dip. This latter expedient is adopted in very delicate stimtdatiom experiments. It is, however, preferable in most experiments to use the galvanic key. It consists of a plate of vulcanite: firmly attached to a strong rectangular vice-pin. On the plate there are two small thick pieces of brass, each bearing two binding screws, 6, c, placed at a short distance from each other. These can be united by raising or depressing the brass arm, d, which has an ivory handle, and turns on a pivot attached ■ to the piece of brass, c. The wires from the battery are con- nected with the two internal binding screws, while the two external ones connect those going to the nerve or muscle. When the handle is pushed back, the key is opened, and the current passes to the tissue to be irritated ; but when the handle is pushed forwards and the key closed, as seen in the figure, the current passes along the thick arm of brass, back again to the battery. 4. Pohl's commutator, gyrotrope, or rtieotrope (Plate XX, fig. 6). — This instrument is for the purpose of inverting or changing the direction of a current of electricity. It consists of a round disc of wood or vulcanite having six small mercury cups. A, B, a, h, a, (3, in it substance, in connection with each of which there is a binding screw. The cups a, h, are in conr APPARATUS. 529 stant connection with a pair of brass -wires, P, 0, brought close to each other at S by a piece of glass tubing, into -which they are inserted. These brass wires carry two brass arcs transversely, m, n, o, and p, q, r, having their ends free, so that by moving the glass bridge S forwards or backwards, the ends may dip into the cups a, /3, or A, B. The apparatus may be used with or without the cross wires h, i, the wire h being curved in the middle so as not to touch i. (1.) Without the cross vdres. — The wires-from the battery or key are fixed into a and 6. The current cannot pass across the bridge S, because the centre is com- posed of glass. If now two -wires are in connection -with a, A and the arcs dip into these cups, as shewn in the figure, the current -will flow along those -wires. If, on the other hand, two other wires are in connection with the cups A, B, and the ends of the arcs are dipped into them, then the current will pass from A to B. Thus, by simply twming the central bridge bearing the arcs, we can send a current either in the direction of a, 0, or A, B, at pleasure. (2.) With the cross wires. — Suppose, now, the wires h, i, are inserted so that the wire i connects the cups a, B, and the wire h, ^ and A, a different use is made of the instru- ment. If the current, for example, entered at-J-a, it would follow the direction a, P, r, a, j8, n, 0, and back to the battery by — 6. If now we reverse the bridge, the direction will be a, P, q, A, along the cross bar h to /3, a, from thence along the cross bar i to m, o and — b, and from thence back to the battery. By this last arrangement, the current has passed along the circuit between a and /3 in such directions that it can be sent up or do-wn a nerve at the will of the experimenter. The course of the current, however, in these cases, can only be clearly under- stood by a study of the instrument itself. 5. Muscle tehffraph (Plate XIX. fig 7).-— This is an appar- atus very useful in experiments on both muscle and nerve, and it consists of the following parts : A brass forceps. A, at the end of an arm capable of sliding up and do-wn on an upright round pillar of brass. This is for holding the femur of a frog's leg which has the gastrocnemius muscle attached to it. The screw S, permits the forceps A, to be rotated in any direction, and fixed securely in any position. Into the tendon of the gastroc- nemius a small hook h is inserted, to which is attached a fine thread passing round a pulley ^, and then do-wnwards along a to a little balancing bucket 6, containing a few shot. On the S^o PRACTICAL EXPERIMENTAL PHYSIOLOGY. same pulley we have a long arm, bearing at its free end a round coloured disc of mica, ■which moves in front of a piece of white plate in the direction of the arrow. By the contraction of the muscle, the signal is pulled up to a greater or less extent, and thus the eflfecfof irritation on it may be seen by many observers at once. If the muscle is to be stimulated by the direct application of a current, the wire from the positive pole is a attached by the bending screw S, and that in connection with the negative, x, is wound tightly round the hook fixed in the tendo AchUUs. The upright bearing the pulley and disc, is fixed in a wooden socket which can move in either direction in a groove, and is retained in its position'by a strong screw, Z. 6. Dv, Bois-Reymond's polarizable electrodes (PI. XIX. fig. 6). — This apparatus is designed for the purpose of stimulating a nerve in any situation. It consists of a, a strong wooden stand bearing a round piece of vulcanite b, in which we have two small binding screws. In connection with this we have a ' long arm, having in its centre a universal joint which can be tightened in any position by the screw c. This bears the essential part of the apparatus, which consists of two triangular platinum points or plates, e, each soldered to a thick wire passing through a square block of ivory. This block has two small screws on its upper surface, which are for the purpose of adjusting the distance of the platinum points from each other. Underneath the ivory block and electrodes we have a glass plate for insul- ating the wires. When the instrument is used, the nerve is laid across the two electrodes, and the portion of nerve on and between them is thus stimulated. Escperiments on Contractility. The property of contractility can be readily demonstrated by shewing that a piece of living muscle, or a whole muscle, con- tracts when irritated. The irritation may be mechanical, such as by a blow, or a pinch ; chemical, as by the action of a solution of common salt ; electrical, on applying electricity ; or vital, on stimulating a nerve. The truth of the Hallerian doctrine of contractility, namely, that it is inherent in muscular tissue, and not dependent on nerve may be demonstrated by two experi- ments. 1. John Reid's experiment. — Eemove the sciatic nerve fr6m the leg of a living frog, and irritate the muscles by an induced cur- EXPERIMENTS ON CONTRACTILITY. S3,i rent of electricity. At first there is violent. spasm or tetanus, but after some time the muscles cease to respond to the stimulus. Thus the contractility has been exhausted. But allow the frog to lire for six, eight, or twelve hours, and it will be found, on again applying the stimulus, that the contractility has returned, while sensibility has not. , 2. Bet'nard's Woora/ra expermmii, as shewn hy Du Bois- Reymond.* — This requires the following apparatus : 2 muscle telegraphs, 1 of Du Bois-Eeymond's polarisable electrodes,, a Pohl's commutator, without the transverse bars, a key, an induction apparatus, and a Smee's or Daniel's element. Mode of preparing the frog.— The frog is chosen for many of these experiments because it "is easilj' manipulated, and the muscles and nerves can be quickly isolated. First, decapi- tate the animal, or cut through the medvUa with a sharp pair of scissors, to destroy sensation, then holding it in the left hand\)y the legs or lower part of the body, turn the animal round, and cut the body through about the middle of the abdomen. Then sieze hold of the back bone with the fingers and- thumb of the left hand, and with the forefinger and thumb of the right hand, quickly drag off the skin of the legs. Then various preparations may be made according to the nature of the expe- riment. The limbs may be used without further disseption, or the sciatic nerve may be dissected out (Plate XIX, fig. 3 6), or the gastrocnemius muscle, with or without the sciatic nerve, may be isolated. In the experiment about to be described the sciatic nerve is first dissected out. This is easily done by pressing the muscles of the thigh forwards with the thumb and fore- finger of the left hand, when the nerve usually starts into yieWj Then with a pair of blunt-pointed scissors, separate the nerve from the surrounding tissues, taking great care not to injure or even touch it. Cut through a small branch which runs downwards and inwards a little above the middle of the thigh. Trace the nerve as high up as possible, so as to have it of considerable Itogth, cut it, and with a blunt quiU or an ivory point turn it down upon the gastrocnemius in order to keep it moist. Then remove the muscles of the thigh, except the attachment of the gastrocnemius, and snip through the femur ■just below its head. Now cut through the tendo AchilMs, and * Lesons sur les eSets des substances toriques, 18S7i p. 277. 11 S32 PRACTICAL EXPERIMENTAL PHYSIOLOGY. puU the gastrocnemius upwards to the knee. Then amputate the leg below the knee, and you have a preparation consisting of a femur having the gastrocnemius attached to its lower end, together with the uninjured sciatic nerve. A hole in the gastrocnemius tendon should now be made for the steel hook of the muscle telegraph. ' Woorwra soZafoom.^Dissolve 5 grains of woorara in a little weak spirit, rubbing it up in a small mortar, and then add 5 drops of glycerine ajid three drachms of distilled water. Each minim contains about the l-38th part of a grain, and usually 6 minims, or about the l-6th part of a grain is a sufficient dose for the experiment. The eieperimenl consists in first putting a ligature on the femoral artery in one of the limbs of a frog, or tying a tight cord round the upper part of the hmb, so as to prevent the poison entering it ; then with a syringe having a fine nozzle we inject, under the skin of the back, six minims of the above solution, and allow the animal to come tho- roughly under its influence. It •should take about half-an-hour to completely prostrate the animal, so that it rests on its belly unable to move. Care must also be taken not to inject too strong a dose of the woorara. Two dissections are now made in the manner already described. In the one the sciatic nerve has been poisoned by woorara, and in the other, it is quite healthy. Each limb so prepared is now attached to a muscle telegraph (see Fig. d), a pair of brass f orcepsTseing placed midway between the two telegraphs, so as to hold the two femurs (as), and the two nerves (e) are laid across the platinum points of Du Bois- Eeymond's electrodes (/). These electrodes are connected by wires {g) with two of the cups of Pohl's commutator by binding screws, and from the other two cups, wires (A) proceed to, and are wound rotind, the hook fixed into the tendo Achillis of each muscle (e). The two cups of the commutator, into which the iwires bearing the arcs are permajnently fixed are connected with' two outer binding screws of a key placed at i, From the two MUSCULAR ELECTRICAL CURRENT. 533 inner binding screws, wires {€) proceed to the secondary coil of an induction apparatus (k), while the primary coU is placed in the cir- cuit of a Daniel's or Smee's battery, consisting of one cell. By this arrangement of apparatus, the eommutator enables us to reverse the electric current so as to irritate the twp nerves or the two muscles at pleasure. If successful, the result will be that when both nerves are irritated, only one muscle contracts and elevates the disc of a telegraph, namely, the one supplied by the nerve not poisoned by woorara ; whereas, if the current be sent through the m/useles, both contract, and the two discs are elevated. Thus, although the nerve has been poisoned by woorara, the con- tractility of the muscle remains, a fact which demonstrates the truth of the Hallerian doctrine that it is a property inherent in muscle, capable of being excited by any direct stimulus, and not dependent on the nervous system. KolUker's epop&nmeiift.^-A reverse experiment to the one just described is made by destroying the contractility without affects ing the motor nerves by means of meratria. The experiment is conducted in the same manner, and it will be found that when both nerves or both muscles are irritated, one muscle contracts, namely, the one which has not been poisoned. Experiments cm the evolution of dectridty hy mitscles. All muscles evolve a constant stream of electricity (p, 82), passing from any natural or artificial longitudinal section to any transverse section (p. 166). In order to demonstrate this im,- portant fact, the following apparatus is necessary : (1.) A multiplying galvanorrteter (see p. 149). — This instrument is represented in Plate XIX. fig 4. It consists of an astatic combination of two magnetic needles (p. 149), the lower of which is surrounded by a coil of fine copper wire. When even a feeble current of electricity is passed through this wire, 3. deflection of the needle is obtained. The instrument must be^^ carefully arr^iPged, the needles rendered perfectly astatic so as to point from east to west, and the whole levelled by means of three screws supporting a brass disc (a) ; on the surface and ia the centre of the disc is a brass box (6), on the top of which is fastened a boxwood frame (0) supporting the ooUs of wire. Thi? brass box can be nmde to revolve by means of a screw {g), which S^\ PRACTICAL EXPERIMENTAL PHYSIOLOGY. acts as a fine adjustment, and enables us to place the coils of ■wire in any direction we please. The disc (a) is usually gradu- ated into 1-lOths of a degree. The two pillars {hK) support a horizontal bar, having suspended from its centre, by a single fibre of spun silk, the astatic combination of needles, which are usually kept steady from vibrations by a small magnet placed on a line with the direction of the coils of wire. On the top of the wooden frame (C) we have a circular scale of white paper divided into parts of 90°, which is so arranged that zero is also parallel with the direction of the coils of wire. The instru- ment is protected from dust and currents of air by means of a cylindrical glass cover. It must be securely fixed, carefully levelled, and made free from vibration. (2.) A pair of Du Bois-Reymond's non-polarizable electrodes. (See Plate XIX. fig. 5.) — They consist of shallow troughs of zinc, carefully amalgamated on the inner surface. In connection with each trough there is a brass pillar (c) supporting two bind- ing screws. The trough is placed upon a piece of vulcanite which acts as an insulator. Into each trough we place a saturated solution of sulphate of zinc. We must now prepare two cushions of Swedish filter-paper as follows : Fold a sheet so as to make a bundle or cushion about half an inch thick. Place, it in the trough so that one surface rests everywhere in close contact with its bottom, bend one side over, as shewn in Fig. 5, 6, and with a sharp razor cut the cushion so as to make a perpendicular surface. The cushions being thoroughly saturated with the sulphate of zinc solution would exercise an irritant action on the muscle, if laid upon them, and would cause it to contract. This is avoided by making two thin films or plates of sculptor's clay moistened with saliva. One is placed on the surface and perpendicular Section of each cushion, as seen in Plate XIX. fig. 5 (g). Strips of bladder well soaked in white of eggmay also be used for this purpose. / (3.) Arrangement of apparatus. — The two troughs, prepared as already described, are placed opposite to each other, at a distance of about a quarter of an inch. A thin wire is conveyed from each trough to the two innermost binding screws of a key. Prom the two outer binding screws, wires pass either directly to the galvanometer or to a special apparatus termed the com/mutator. This is a mahogany box, having inside a coil of wire to increase the resistance to the electrical current, and a MUSCULAR ELECTRICAL CURRENT. 535 series of brass plates and movable contact lerers connected with each other, so that the muscular current passing through it can be diminished or inverted at wiU. In order to prove that the apparatus does not itself pro- duce any electric current, the two troughs should be connected with each other' by a little oblong pad of blotting paper wet with the solution of zinc sulphate. The key is now opened, and if the appaxatus be in order, the needle is unaffected. Any long muscle of a frog can be dissected out, the gastrocnemius i^ best, and a clean transverse section made with a pair of sharp scissors. The piece of muscle thus prepared, is now, laid upon the plates of moist clay on the cushions in the troughs, so that its transverse section is placed accurately against the one cushion, and its longitudinal section against the other. The key is now opened, and a deflection of the galvanometer needle at once indicates the -presence of a current of electricity, and the direction in which one pole of the needle is deflected shews the direction of the current. The key is now closed, and when the needle, after oscillating, stops at zero, the position of the piece of muscle should be reversed, and the key opened, when it will then be found that the needle will be deflected in the opposite direction to that of the first experiment. The experiment may be modified by placing a transverse section, or a longitudinal section, against each cushion, when there will be no or little effect on the needle. For this purpose, and for ascertaining the various electrical conditions of points of the surface oiE the muscle, there are many subsidiary contrivances, termed supporting plates, rheoplwric tubes, &c., a knowledge, of the use of which is best acquired by practice. It having thus been clearly shewn that a piece of living Inuscle; evolves a current of electricity, it may next be demon- strated that when the muscle is thrown into a state of contrac- tion, this property is diminished. For that purpose it is necessary that the muscle have attached to it the uninjured sciatic nerve. It should then be adjusted on the two cushions, as previously described, while the nerve is laid gentiy on the platinum electrodes, which are in connection with an active induction coil, a key intervening. Deflection of the needle by the muscular current is now allowed to take place, and then to come to rest. On opening the key between the battery and the platinum electrodes, the muscle on the cushions ia at once 536 PRACTICAL EXPERIMENTAL PHYSIOLOGY. tliro-wii into a state of contraction through the irritation of the nerve, and the needle of the galvanometer will be seen return- ing towards zero. Thus it is proved that the intensity of the electro-motive power is opposed to that of active contractility, (See p. 168.) Numerous other structures, both animal and vegetable, such as skin, intestine, stems, leaves, bark, &o., may be examined with the view of ascertaining the presence or absence of a cur- rent of electricity. Bv, Bois-ReymoncPs enpervment to shew the presence of a musr cula/r current in the living hwnan body. — This will be understood by referring to Plate XIX. fig. 10, where an individual is re- presented grasping a roller, c, attached to two wooden supports firmly screwed to the table, so that the forefinger of each hand is immersed in, and touches the bottom of, the trough 6. If the muscles of both arms are relaxed, there is no effect on the needle of the galvanometer a, but if the muscles of one of the arms are contracted by firmly grasping the roUer, in many individuals we see a feeble deflection of the needle. Among the numerous students attending the practical physiology class dur- ing each session, a very few are found capable of causing this deflection, and we have observed that a large proportion of the successful individuals are of what is usually described as the sanguine temperament, having often red hair. Experiments on the effects of muscular irritation. This investigation, which is of great importance therapeutic cally, should be conducted in the following manner : (1.) Effect of a contifmoiis cmrmt (p. 82). — The hind leg of a frog is held by a pair of strong brass forceps, sliding on a round pillar of brass which is fixed into a solid wooden stand. Such a pair of forceps may be seen on the left side of fig. 7, Plate XIX. A. The Umb so fixed is to hang down loosely, the knee being flexed. Two wires from a Daniel's or Smee's element are attached to the inner binding screws of a key. Wires are also conducted from the two outer binding screws, one being fixed by the screw S (Plate XIX. fig. 7), while the other is attached to the frog's foot. It will now be found that the muscles of the limb contract on opening and on closing the key, but there is no contraction while the key is open, that is during the passage of the continuous EXPERIMENTS ON MUSCULAR IRRITATION. 537 current. A continuous current, however, eflfectff electrolytic changes in the muscle. (2.) Effect of an interrupted cwrent. — By the same arrange- ment of apparatus, it may be shewn that an interrupted cuiTcnt stimulates the muscle on the opening and closing of the key„ and if this be done so rapidly that the muscles have not time to become relaxed before they receive a fresh shock, a constant state of rigidity or tetcmua is occasioned. «• (3.) Effect of an induced or Faradio current. — When an induction apparatus is employed for stimulating the muscle, the latter at once becomes tetanic, even although the same galvanic element is used to produce the induced current, as was employed in the two previous experiments. This shews that an induced current irritates much more strongly than either a continuous or an interrupted current. Production of tetanus. — Tetanus is a. state of permanent muscular contraction. It may be studied by the following illustrative experiments : (1.) By meckamcal violence. — Kill a frog by violently striking its head against the table. It will usually be found that for some minutes after death, the body becomes rigid from the tetanic condition of the muscles. (2.) By. an induced cwrrent. — ^As has been above described, tetanus is produced by an induced or Faradic current. (3.) By saline solutions. — Prepare the limb of a frog in the usual way, and expose the sciatic nerve. Place the limb on a glass plate, and allow a drop of a strong saline solution to faU upon the nerve. In a few minutes the muscles become tetanic from the irritant action of the saline solution on the nerve. (4.) By Kuhn^s apparatus, consisting of a pair of vertical forceps fixed over a circular glass plate, the irritant action of many different acid, alkaline, and saline substances can be examined. The muscle preparation is fixed in the forceps, so that either it or the nerve are suspended over the glass plate. The latter may be elevated or depressed by a screw placed underneath it, so that the irritant solution, the effect of which is to be examined, may be brought into contact with the extremity of the muscle or nerve. (5.) By Heidenhainls Tetanometer, — ^Another very ingenious mode of producing tetanus is effected by the use of an apparatus termed Heidenhain's hammer or tetanometeir. The use of this S3^ .PRACTICAL EXPERIMENTAL PHYSIOLOGY. Instrument is to beat the nerve suppljdng a muscle or limb with great rapidity, and thus, by frequent mechanical irrita- tions, produce tetanus. It is shewn iu Plate XIX. fig. 9, and consists essentially of a modification of Neef's hammer, already described ia connection with the induction coil (p. 527). The apparatus rests upon a vulcanite plate, K, supporting a brass column, sl; which carries the lever L, in the middle of which is the armature of the electro-magnet (near L). This lever turns upon an axis at a, and may be relaxed or tightened by turning the screw S, which acts upon a spiral wire above it, marked with a smaller s. The pillar C supports, on a horizontal Arm, the screw S, , the point of which rests on a small piece of platinum on the upper surface of the lever. It is at this point the current is broken, and thus the hammer caused to vibrate. In the base of we have a screw, S„,, which secures the wire coming from the positive pole of a galvanic element, while the screw Z receives this wire in connection with the negative pole. When used in the present experiment, the screw S„ is attached, by a piece of copper wire, with the screw S„. The hammer, properly so called, is seen at h. It is made of ivory, and beneath it there is an ivory support, t, which receives the nerve in the groove h}. Behind the ivory support there is a small ivory axle. A, fixed between two brass notches, and caused to move slowly by the pressure of the spring ''p. By means of the screw S"", the whole of this part of the apparatus may be elevated or depressed at pleasure. When the sciatic nerve of a limb (which is placed on a glass-support, or held by a pair of forceps before the apparatus) is placed in the ivory groove, and rapidly beaten by the ivory hammer, which is worked by the electro-magnet, the muscle becomes at once tetanic. The nerve is usually rapidly beaten through, and then it is neces- sary, in order to repeat the experiment, to attach its- end by a fine silk thread to the ivory axle, and by turning the latter, to drag through a fresh piece of nerve. The only difficulty in using this apparatus is, that the different parts must be so adjusted with reference to each other that the nerve be beaten with a proper amonnt^of force and rapidity. (6.) By Poggendorff's whed. — Another mode of producing tetanus by an interrupted cun'ent is by means of an instrument termed Poggendorff's wheel. This instrument consists of a EXPERIMENTS ON MUSCUL/LR IRRITATION. 539 ■wooden disc or wheel having twenty or more spaces cut out of its circumference, which are occupied hy pieces of brass, alternating with pieces of ivory. The pieces of brass are con- nected alternately with each half of the axle, the two halves being insulated from each other in the centre of the wheel by an intervening piece of vulcanite or glass. Two stiff brass springs, having screws at their bases, are caused to press firmly against the margin of the wheel, so that while .the wheel is being rotated, the flattened ends of the springs touch alter- nately the pieces of ivory and the pieces of brass. The bind- ing screws in connection with the springs receive wires coming from a galvanic element, while there are two others on the supports of the axle from which wires may be conducted to a muscle. When the connections have been thus made, and the wheel rotated slowly, the muscle contracts and relaxes alternately, but when turned quickly, it becomes tetanic. (7.) Rittefr's tetanus. — It may also be demonstrated that if a continuous current of electricity be allowed to traverse a nerve attached to a limb in the upward direction, that is centri- petally, for two hours (the nerve being kept moist and warm), and the current be then suddenly interrupted by moving the electrode neict the free end of the nerve, the muscles become suddenly tetanic. This has been termed the tetanus of Ritter. (8.) By strychnine. — Tetanus may also be produced by poison- ing a frog with a solution of strychnine. This poison, injected hypodermically, increases the reflex action of the spinal cord, so that the slightest irritation at once throws the animal into a state of tetanus. Effects of the opening and dosing induction shoeh on a muscle. (See p. 82.) — This may be studied accurately with the aid of an instrument termed PfMgen's falling apparatus or trip-hammer. A view of this instrument is seen in Plate XIX. fig. 8. On a plate of vulcanite, E, there is a brass plate, haying two uprights, d d, between which we have the steel axle of the hammer e. This hammer consists of a long rectangular handle, a', and of a large steel head, i. On the left side of the latter we have a small steel rod, m, pointing downwards, and tipped with platinum. Above the hammer head, there is an electro-magnet, A , placed between the two supports d d, which may be fixed at any height by the screws n n. When this electro-magnet is called into action by a Smee's element, the head of the hammer is 540 PRACTICAL EXPERIMENTAL PHYSIOLOGY. supported as seeu in the figure. If, however, the galvar circuit be opened, the hammer head falls and strikes agam the end of the lever P at y, forcing it downwards, and th breaking the contact of the other end of the lever with the sore point r. At the same moment, the platinum point m, falls in the conical steel trough X, which contains mercury. By tl arrangement the instrument may be introduced into two gi vanic circuits, and the moment the hammer head falls, the o circuit is closed and the other opened. The connections a made, for the first circuit, by wires attached by the screws c ai y, and for the Other by wires attached to the screws t and Suppose the hammer head to be in the position represented the figure, and a muscle preparation interpolated into each c: cuit. Allow the hammer head to fall, and the point m to d into the mercury in X, and the muscle in the circuit II, passii in the direction c, d, h, i, m, x, y, will receive the closing shoe while that in the circuit, marked I, *, P, r, %, wUl receive tl opening one, because the circuit is broken by the forcil separation of the lever P from the screw r. Thus the action the two shocks may be compared. At Z, underneath the hand of the hammer there is a spring catch which receives it whi the hammer falls, holds it securely, and thus prevents vibratic WKend/ricVs appa/ratua for measv/ring tetanus. — This enabl US to calculate with readiness the number of distinct galvai shocks necessary to produce tetanus. It consists of a series wheels so arranged that if one of them make a revolution in minute, the next will perform twelve revolutions in the sai space of time, the third, 144 revolutions, and so on. Each of the wheels carries on a prolonged axle one or more small wheels brass, having portions of the circumference cut out at equal d tances, and small pieces- of ivory interpolated. A steel spring caused to press against the circumference of one of the whei while it revolves, and an electric current passing through t instrument is opened each time the spring passes from t brass to the ivory, and closed when it passes from the ivo to the brass. The time occupied by the revolution of t first wheel is calculated by causing it to operate on a spri in connection with a small bell, so that the bell rings at t end of a revolution. Knowing the time occupied by the fii wheel, we also know the second revolves twelve times as fa and the third 144 times, and so on. By means of this arranj EXPERIMENTS ON NERVE. 54* ment, electric shocks can be transmitted to a muscle or nerve, varying in rapidity from 12 to 3000 a minute. The interval be- tween the shocks may also be calculated to the 1000th of a minute. Experiments on m/usGular fatigue. — The only satisfactory way of studying the gradual fatigue of muscle, when stimulated to do a certain amount of work, is to obtain a tracing on a cylinder, or plate of glass, by means of an instrument called a myogra- fhion, or muscle-writer {f-Mm, a muscle ; ygafia), I write). Various myographions have been constructed for this pui'pose, but the most convenient is that of Pfliiger, shewn on Plate XX. fig. 5. It consists of a solid wooden stand, S, into which is fixed a strong brass upright, F, carrying upon it a moveable forceps, Z. Into the forceps the end of a frog's femur is securely fixed, the gastrocnemius muscle being attached to it, and hanging downwards. Into the tendo AchUlis a small hook is inserted, which supports by its other end the lever apparatus d b. This lever is a double framework, which moves freely on an axle at the top of the support a. At one end of the lever tbe]'e is an apparatus bearing a stylette, which is employed for making tracings on a plate of smoked glass, P, moving in a frame, B, or still better, a tracing may be obtained on a revolving cylin^ der. Underneath the lever there is a balance, g, attached by a small hook, /, to. a swivel apparatus, c. Into this balance a weight is placed sufficient to overcome the contraction of the muscle, and the consequent elevation of the lever, when the stimulation is removed. In order to keep the muscle and nerve alive for a considerable time, a square glass case may be placed over it, as shewn in the figure, containing moist blotting paper. By means of this appai-atns many interesting experiments may be made, such as the tracing of a muscle stimulated by the opening and closing of a continuous current, the effect of the opening and closing of an induced current, and the eflect of mus- cular fatigue from long-continued stimulation applied directly to the muscle or to the nerve supplying it. Experiments on Nerve. The nerve current is demonstrated in exactly the same man- ner as the muscular current (p. 535). To increase its amount, the nerve should be doubled, and both transverse sections placed in apposition to the cushion (pp. 97 and 169). Effects of decprioiiy on a nerve. — It is easily demonstrated that t^2 PRACTICAL EXPERIMENTAL PHYSIOLOGY. if a current of electricity pass through, a motor nerve, it irritates it, and causes contraction of the muscle or muscles supplied by it. It must not be supposed that the electricity is conveyed along the nerve to the muscle ; it only stimulates the former, and calls into action the nerve force which causes the latter to contract. It has been found, however, that the presence and amount of the contraction depends partly on the strength and partly on the direction of the current. This has already been explained theoretically (pp. 169, 176). Experiments on P finger's law of contraction. To graduate the strength of the stimulation-current, we re- quire ten or twelve small Grove's cells, the zinc surface of each being about 2J square inches ; and also a special instrument termed a rheooord. The rheoaord. — A view of this instrument is seen in Plate XIX. fig. 11. It is for the purpose of enabling us to send a cur- rent of definite strength through a nerve or muscle, and to vary this strength at pleasure. When a rheocord is introduced iato a galvanic circuit, the current divides itself into two, the one of which we can transmit to the nerve, while the other returns directly to the battery. We have thus a nerve circuit and a battery circuit, and if we interpose resistancg in the latter cir- cuit, more electricity will pass through the former. The rheo- cord consists of a long wooden box. Along one side of this box there are two thick platinum wires. Si W^, and S W, con- nected at S and Sj by screws with the two brass plates S, with 1 and S with P. At e a they pass over a piece of ivory to the screws W and Wj. At one end, on the top of the box, there are six brass plates, 1,2, 3, 4, 5, and 6, each of which is separated from the other by an interval, which may be readily filled up by a thick ivory-headed brass stopper. Along the surface of the box, and under the platinum wires, there is a piece of brass, Z, capable of sliding backwards or forwards, and having on its surface two hollow cylinders. A, made of polished steel and filled with mercury. These cylinders are pierced by the platinum wires, and the ends directed towards Wi and W are tightly corked. This brass slide, therefore, forms a bridge between the two platinum wires, which are nowhere else connected by a conducting substance. The current cannot pass from S to Si except by going to the nearer cylinder in the direction of the EXPERIMENTS ON NERVE. 543 arrow >, and from the other cylinder to Si, as indicated by the arrow < . It is, therefore, evident that the amount of resistance offered by the platinum wires to the passage of a current of electricity may be modified by pushing backwards or forwards the brass slide. In proportion as it is pushed towards Wj, W, the resistance evidently becomes greater. -Along the side of the platinum wires there is a graduated scale divided into millimetres, which may be used in comparative experiments. In order still farther to modify the resistance at pleasure, there are on the under surface of the cover of the box, in connection with the brass plates 1, 2, 3, 4, 5, 6, a series of wires of German silver, which are represented in fig. 11 by dotted lines, and which, after going up and down in the box, pass from the one brass plate to the other. When all the stoppers are placed between the brass plates, the German silver wires are not in the battery circuit. If, however, we remove the stopper between 5 and 6, the wire connecting 5 and 6 (bracketted at the other end of the figure, and marked X) is brought into the battery circuit, and thus the amount of resistance is increased. The same holds good with regard to the other stoppers. In connection with the brass plates S and 6 there is a short brass upright, each bearing two binding screws, P and Q. The wires from the battery a a are connected with the lower binding screws, while those going to the nerve h h are attached to the upper. Mode of demonstrating BfMger's experiment. — The limb of a ■frog, having been prepared by dissecting out the sciatic nerve, without injury, is fixed in a pair of brass forceps. The nerve is then stretched over two copper or zinc wires, carefully insu- lated, and provided with connectors, by which they are attached to two of the cups in a Pohl's commutator, the cross bars being present for the purpose previously described, that of enabling us to transmit a current upwards or downwards in a nerve at pleasure. Two wires are led from the commutator to the upper screws on the rheocord. The lower screws of the rheocord receive wires from the battery, and a key is introduced into the circuit, by means of which we can open or close it at pleasure. The connections having been thus made, we endeavour in the first place to stimulate the nerve by as weak a current as pos- sible. This is effected by using one small Grove's cell and hav- ing all the brass stoppers of the rheocord in their places. By this arrangement there is almost no resistance in the battery 544 PRACTICAL EXPERIMENTAL PHYSIOLOGY. circuit, and consequently a weak current is transmitted to the nerve. By means of the commiitator, also, we are enabled to transmit the current along the nerve either in an upward or downward direction, and the result is to be observed on opening and closing the key. The strength of the current is now to be increased by using two or perhaps three of Grove's ceEa, and by removing one or two of the brass pegs in the rheocord. On open- Lug and closing the key, and by moving the commutator, we now observe the effect of a medium current transmitted upwards or downwards along the nerve. The effect of a strong current is shewn by using five, six, or eight of Grove's cells, and by removing all the pegs in the rheocord. By carefully gi'aduat- ing the strength of the current,- and operating upon at least IJ inch of healthy nerve, the results described at page 172 may usually be obtained ; but occasionally, from the fact that the nerve is irritable in frogs which have been long kept in con- finement, it is difficult to obtain contractions in the order described by Pfluger and others. Pjluger's •experiment to shew that the nerve force accimvidatss intensity as it advances. — This remarkable fact may be demon- strated by stimulating a nerve close to the muscle, or at a short distance from it, when it wiU be found that a current too weak to cause contraction of the muscles when sent to a point close to the muscle, will cause powerful contractipja when transmitted to a point at a distance from the muscle (p. 175). To succeed with this expejMoent, it is necessary to use a large frog so as to obtain a long nerve. This nerve is stretched across two pairs of wires, the wires in each pair being placed close together, and each pair being also separated by a distance of about an inch. The wires are placed in connection with a Pohl's commutator, to which also are attached wires from the secondary coil of an induction machine, a key being interposed in the battery circuit. We are thus enabled to transmit the current either near to, or at a distance from, the muscle ; and by diminishing or increasing the distance between the primary and secondary coil of the induction machine, we can graduate the strength of the current. The best method of making the experi- ment is, in the first instance, to remove the secondary from the primary coD. to such a distance that no effect is produced when the nerve is stimulated either close to, or at a distance from, the muscle. Having then placed the commutator so that the current EXPERIMENTS ON NERVE. 545 vill be transmitted along the wires to the portion near to the muscle, the key is opened, and the secondary coil is gradually approximated to the primary, until a very feeble, almost imper- ceptible, contraction is produced. On now moving the commu- tator so as to transmit the current to the portion of uerve at a distance from the muscle, a very powerful contraction at once takes place, clearly demonstrating that the same amount of stimulus produces a greater e£fect when applied to a nerve at a distance from, than when applied near to, the muscle. Experiment to determine the rapidity of the nerve dvrrent. This problem, which has received the attention of many physiologists, has now been satisfactorily solved by the labours of Helmholtz and Du Bois-Eeymond. The necessary instru- ment is termed a tnyographion, of which there are several varie- ties, but the one generally used is that employed by the two distinguished physiologists just mentioned. A sectional view of this instrument is seen, Plate XX. fig. 1, and the arrange- ment of the apparatus for the experiment, will be understood by referring to the diagrammatic sketch in Plate XX. fig. 3. Mode (^calculating time by tracings on a revolving cylinder. — Before describing the Myographion, the student must under- stand this important method, which is applied to many ex- periments in practical physiology- Suppose a cylinder, worked by clockwork, or even steam power, makes one revolution in a minute, and its surface is divided into sixty equal parts by sixty vertical lines at equal distances from each other, the distance between two lines evidently represents in time one second. By measuring the circumference of amy cylinder, and by observing the time occupied by one revolution, we can thus calculate the time represented by the distance between any two points in the circumference. This principle, which we owe to Th. Young, 1807, is taken advantage of in the myographion. It is necessary that all revolving cylinders go smoothly, and at a uniform rate. This is attained by a fly-wheel, or a centrifugal apparatus attached to it. Description of the Myographion. — ^The myographion, although a very complicated instrument, consists essentially of threeparts : 1st, arrangements for holding a muscle having the sciatic nerve attached, the latter being connected with electrodes ; 2d, clock- work for moving a revolving cylinder with a certain measured ^^fi PRACTICAL EXPERIMENTAL PHYSIOLOGY. rapidity ; and 3d, arrangementa for stimulating the nerve at ,th,e particular moment when the cylinder has reached a knovm velocity. (1.) The muscle cousists of the gastrocnemius (figs. \J and 3 6) attached to the femur, and having the sciatic nerve in connection ■with it. Into the terido Achillis is inserted a small hook, from which is suspended a long thin iron wire, h, the latter being in connection with a lever apparatus, 1 1. This lever, the fulcrum of which is on the top of the pillar F, is balanced behind by a movable weight, m, and has at its other extremity a rectangular arm, O, bearing the stylette P. This stylette is opposite the cylinder B, and it is evident, on examining the plate, that if the muscle contract, it will elevate the lever, and the stylette P will make a mark upon the cylinder. At the top of the figure will be seen various contrivances for accurately adjusting the muscle with reference to the lever. The strong brass pillar E supports a square glass chamber, in which the muscle is placed, and in which it can be kept living and moist for several hours, by placing on the inner surface of the glass a few bits of blotting paper dipped in warm water. The floor of this chamber is made of vulcanite, and is perforated by a hole between r and r, so as -to permit the passage downwards of the iron wire h, connecting the tendo Achillis, with the lever. When the apparatus is being ■used, in order as muGh-a,y " PflShible to exclude air, and keep the muscle moist, the hole in thewif ,~^flbor is almost closed i5Vards\*°' by two semicircular pieces of gla* . Nng a small excava- tion on the straight border of eacllf i j ^®^ ™ apposition, only a small round opening is lef tfr*^'-' '^''fcafiorceps may be elevated or depressed by moving tf ** steam \ g^r downwards in the socket marked c.^ This so by clock-work (see Fig. 13). The degree of pressure by the button f (Fig. 14), on the pulse may be regulated by the screw i f (Fig. 14), seen also at a (Fig. 13.) The objection to this form of sphygmograph is, that there are no means of accurately measuring the pressure of the button on the ' pvdse. This has now been accomplished, in recent instruments, by means of a screw which regulates the pressure of the spring (Fig. 14) h. The head of this screw is divided into equal parts, each division representing so much pressure in grammes- weight, so that in taking tracings of the same pulse at different times, we are enabled to use exactly the same amount of compression upon it. Other sphygmographs have recently been constructed by Mayer & Meltzer, of London, which may be easily adjusted to the wrist by a bracelet, and in which the tracing is obtained on a piece of mica surrounding a small revolving cylinder. For a description of the pulse, and of the meaning to be attached to a sphygmographic tracing, see pp. 216, 217. The cardiograph of Marey. — A view of this apparatus is seen in Plate XXI. fig. 16, by which Marey was enabled to obtaia three tracings simultaneously from the right auricle, the right ventricle, and the pulsation of the heart through the walls of the chest. It consists essentially of (I.) a registering apparatus ; (2.) small oval sacs or ampullae,- made of india-rubber, for receiving the impulse in the vessels or cavities of the heart ; and (3.) an apparatus termed a tamhow or drum, for com- municating the impulse to a lever. The registering apparatus is a cylinder. A, E, moved by clock-work, on which there is enrolled a long band of paper. The levers le, Iv, Ic, placed one above the other in the same plane, touch the paper by the point of the pen, which terminates each (Fig. 15, 1, P). The ampullae for receiving the impulses are seen in Fig. 16, c, v. These communicate with the tambours by long elastic tubes, containing air, marked to, to, tv, which are supported by two iron stands, seen one on each side of A 3. A separate view of EXPERIMENTS ON THE CIRCULATION. 555 one of the tambours is seen in Pig. 15. It consists of a shallow drum, T, on the surface of which there is placed a thin circular plate of aluminium, a. This supports, and is at- tached to, a short upright in connection with the lever I, I, P. There is an arrangement seen above E for moving the drum backwards or forwards, and there is also a screw by which we can move the position of the aluminium plate, A short brass tube communicates with the bottom of the drum, or opens into its side, as seen at 6, to which the elastic tube is fixed, so that the slightest pressure of the air in the drum communicated through the elastic tube produces a movement of the lever. The advantage of this apparatus is that it is easy of application, and its disadvantage is that, in consequence of the great amount of elasticity of the india-rubber drum head, the lever is apt to produce a number of secondary curves instead of one firm, well-defined Una. It may be applied to the registration of many other kinds of movement. The Sphygmoscope of Scot Alison. — This instrument, as its name indicates, is an apparatus for shewing the movements of the pulse to the eye. It is a truncated cone made of brass, the base consisting of a piece of highly elastic india-rubber. To the truncated end of the cone there is a piece of india- rubber tubing passing to a glass tube, bent near the same end to an angle of about forty-five degrees. The apparatus being nearly flUed with a coloured fluid, such as infusion of litmus, it is evident that the slightest impulse communicated to the elastic base of the cone, will be at once seen by an elevation and depression of the coloured fluid in the tube. The Sphygmoscope of Gzermah. — This instrument consists of a small rectangular mirror, so fixed by its upper extremity aa to move freely when the lower extremity rests upon the pulse. If the instrument be now fixed to the arm so that the free end of the mirror rests on the radial artery, and a strong ray of light be reflected from the mirror upon a vertical scale, the slightest movement of the mirror will be manifested by a great extent of, movement of the spot of light on the scale. Thus the movements of the pulse may be exhibited to a large audience. The Sphygmosphone of Upham. — This apparatus, seen in Plate XXI. fig. 17, is for the purpose of enabling the ear, by means of electric bells, to determine the frequency and rhythm of the cardiac and radial, or femoral pulsations. It may be ^^S PRACTICAL EXPERIMENTAL PHYSIOLOGY. divided into two parts : (1.) An arrangement for receiving the impulse, and by means of this impulse, breaking an electric circuit ; and (2.) an apparatus for ringing one or other of a pair of electric bells when the circuit is broken. The arrangement for receiving the impulse from the apex or base of the heart through the thoracic wall, and from any large artery, consists of two small bell-shaped glasses, I, m, having the mouth of the bell covered over with thin india-rubber. From the other end of the bell we have two elastic tubes which are attached at their other extremity to similar bell-shaped glasses, also closed by india-rubber, marked i and i'. When these tubes and bells are carefully filled with water, it is evi- dent the slightest impulse received on the india-rubber surfaces of .Z m will be communicated to those of i and i'. Immediately over i and i' there are two brass bars moving upon hinges, and having their free ends directed inwards, and resting upon a square piece of brass, as seen at h and k'. Attached to the under surface of each of these bars there is a round metallic plate, which rests on the india-rubber surface of the glasses i and i'. By this arrangement, a very slight impulse communicated through the fluid in I i and m, i' , will elevate the brass bars and break the contact at h and K . The other portion of the apparatus consists of two electric bells, a and 6, which are rung by the hammers c and d, attached to the keepers e and / of the two electro-magnets g. The current of electricity from two of Smee's elements is conveyed into the appa- ratus by the wire p, passes through both electro-magnets, which, by attracting their keepers e and/, withdraw the hammer c and rf to a short distance from the bells a and 6. The point of contact between the two electro-magnets, as already explained, is at h and H . If, therefore, an impulse be communicated through the apparatus I i suificient to break the contact at h, by elevating the brass bar, the keeper of the electro-magnet g is released, and the bell a will ring, only one stroke of the hammer c being given. In the same manner the bell 6 is rung through the influence of m i. By means of this apparatus the interval of time between the cardiac and radial pulsations may be rendered evident to an audience by the different tones of the bells ; and as the contact-breaking part of the apparatus may be in Edinburgh, and the electro-magnetic apparatus in London, a demonstration might be given by telegraphic wires to a London EXPERIMENTS ON THE CIRCULATION. 557 audience of the cardiac and radial pulsations of an individual in Edinburgh. Experiments to measwe the rapidity of the circulation. This may he estimated roughly by means of two instruments. 1. Hcematachometer of Vierordt (ai/ia, blood ; rd'^og, speed ; /JjItoov, measure). — ^The essential part of this apparatus is seen in Plate XXI. fig. 20. It consists of a rectangular chamber, A B, the sides of which are made of glass. This chamber is furnished with two nozzles, a and b, for insertion into an artery which has been cut across. In the anterior part of the chamber there is a very light vertically-suspended pendu- lum seen at c, placed close to the point of entrance of the current of blood into the chamber. This will of course move the pendulum from the perpendicular as seen at e, and the amount of this deviation will indicate the velocity of the current. To this apparatus is suspended a long lever placed above the box A B, which is moved by a rack and pinion arrangement by the hand of the experimenter, synchronous with the movements of the pendulum. The free end of the lever is provided with a pen or brush, so that a tracing may be obtained on a revolv- ing cylinder. The objection to this instrument is, that the conditions of a square box are different from those of a blood vessel; the inertia of the pendulum has to be overcome, the accuracy of the tracing depends on the quickness of the eye and steadiness of hand of the experimenter, and the whole appar- atus is large and difficult of application. 2. Hoemadromometer of Vollcmann {a'ljjir/,, Spofiog, a, race- course, fjjiT^m). — This instrument is seen in Plate XXI. figs. 18 and 19. It is composed of a U-shaped tube, d, e, of a given length, having attached to it a scale, graduated in millimetres. The ends of this glass tube fit at d and e into a brass apparatus, a, 6, having nozzles at a and 5, which are inserted into the cut ends of the artery. This part of the apparatus is furnished with a screw, or stop-cock, bearing a rectangular arrangement of brass tubing, so that by turn- ing it the blood may be caused to flow directly from a to b, as seen at Pig. 18, or along the U-shaped tube, as seen in Fig. 19. The experiment is thus performed : — The artery is laid bare, and the circulation through two inches of its extent is con- trolled by two strong spring forceps fixed on it at that dis- 11^ PRACTICAL EXPERIMENTAL PHYSIOLOGY. tance from each other. It is then divided, and the nozzles a and h inserted into the cut ends, and firmly secured by liga- tures. The stop-cocks are arranged, as seen in Pig. 18, and the spring forceps being removed, the blood will, of course, flow directly from a to 6. The experimenter being provided with an accurate chronometer, on a given signal the stop-cock is turned, so that the blood will flow along the U-shaped tube, as seen in Fig. 19, and the time it occupies in passing from c? to e is noted. The length of the U-tube being known, the rapidity of the cir- culation is, of course, thus determined. The U-tube, however, being almost non-elastic, and in no way fulfilling the conditions of a living artery, the determination of the rapidity must be held as only approximative. Experiments to measure blood-pressure. 1. Hcemadynamometer of Poisseuille (a//ia, blood ; Suva^/f, power ; /j^trgov, a measure). — This instrument consists of a long U-shaped glass tube, Plate XXI. fig. 21, a, 6, of uniform calibre, and having the inner surface exceedingly smooth. Into the tube some clean mercury is placed, which coines to a level in the two limbs as seen at d e. Attached to both limbs there is a graduated scale for registering the oscillations of the mercurial columns. From the limb of the tube at a, there passes the curved leaden tube q I m,, having an air hole at n, a joint at I, a stop-cock at o, and a nozzle placed transversely at q. This bent tube fits the U-shaped tube at a very accurately, and there is a collar, m, which is screwed over the connection so as to make the junction perfectly water-tight. The transverse nozzle at q, is represented of larger size in Fig. 21, b. It con- sists of the tube a b, Fig. 21, for insertion into the artery, and of the short ttibe c placed at right angles to a b, which $ts accurately into the end of the leaden tube at q. The whole of the leaden tube qlm, and the upper limb of the glass tube a d, to the surface of the mercury at d, is carefully fiUed with a solu- tion of carbonate of soda, which is used because it has the property of preventing the coagulation of the blood in the nozzle q. In accordance with the law that fluids press equally in every direction, the pressure of the blood passing through the nozzle q, is communicated latterly through the column of the solution of carbonate of soda to the surface of the mercurial column at d. The blood does not flow into the leaden pipe EXPERIMENTS ON THE CIRCULATION. 559 qlm, but passes straight through the nozzle q, and the increase and diminution of pressure is indicated by the movements of the mercurial columns at d and e. The amount of this pressure is measured by the scales c, Fig. 21. If the mercurial column be depressed one-fourth of an inch at d, it will be elevated the quarter of an inch at e; the total pressure, therefore, being one- half inch of mercury. 2. KymograpMon of Ludwig {xufta,, wave, y^xpoi). — This in- strument, as seen in Plate XXI. fig. 21, is the apparatus just described, together with an arrangement for registering the movements of the mercurial column. This is effected by means of a very light glass float,/, having attached to it a long fine steel wire, f g, at the top of which there is a steel rod bearing a stylette, i. From the upper end of the rod g, a delicate thread passes upwards to the top of the frame h h, moves round a small pulley, and suspends a weight, Js, which acts as an equipoise to the glass float/. The rod g, bearing the stylette, moves in the same vertical plane, being kept in position by two fine steel wires in the frame h h. This apparatus enables us to obtain very delicate tracings, the movement of the mercurial column being communicated to the float, and by the latter to the sty- lette. To the left of Fig. 21, a revolving cylinder, b, is shewn, moving upon an axle, a c, and having a stylette, d, applied to its surface. When it is desirable to make an experiment, with the view of determining the amount of blood pressure, the leaden tube must, in the first place, be carefully filled with a solution of carbonate of soda. For this purpose we require several syringes, having nozzles of various sizes. The stop-cock at is perforated through the top, so as to permit the escape of air, and it is furnished with a small stopper for preventing the escape of the fluid. By means of this stop-cock we can allow the blood pressure to be communicated to the mercurial column, or we can shut it off at pleasure. The leaden tube is to be filled by inserting the nozzle of a syringe into the hole in the stop-cock 0, the latter being turned so as to prevent the escape of- the fluid through the nozzle q. Thus wg fiU the tube I, m, and usually part of the tube n, m, d, — ^the air escaping by the air- hole n. We next introduce the point of the syringe at rij and endeavour to fill the remainder of the tube. When we have done so, we must rapidly remove the syringe, and introduce a ^(io PRACTICAL EXPERIMENTAL PHYSIOLOGY. stopper into the air-hole n, taking care to bring the mercury iu the two limbs of the U-tube to a level. Th6 nozzle is introduced into the artery in exactly the same way as abeady described with reference to the Hsemadromometer. To obtain an accurate tracing, three things must be carefully attended to : 1. The blood must be prevented from coagulating in the nozzle introduced into the artery, and occasionally it may be necessary to remove the nozzle, and to clean it out by a fine wire or bristle, after properly securing the artery. 2. The float must move freely in the glass tube. Before using the apparatus, the tube ought to l?e carefully dried with a piece of cotton attached to a long wire, and the mercury employed must be perfectly free from dust or moisture. Before using the latter, it should be carefully filtered through a minute perforation in a sheet of white writing paper, and be dried by placing it in a porcelain capsule for five or ten minutes before the fire. 3. The stylette must mark the cylinder with as little friction as possible. This is accomplished by attaching to its point a small finely-pointed brush, which is kept wet with ink of sufficient fluidity ; or by means of a small conical glass, fixed to the stylette, having the apex drawn to a very fine point, perforated and bent so as to barely touch the cylinder. A small quantity of ink is placed in the glass, and passes in a very fine stream through the perforation in the bottom. In addition to the curve produced by the movements of the recording apparatus, it may be serviceable to have two other ■tracings made at the same time, one being a horizontal line, drawn by a fixed stylette, and the other a rapid but regular tracing of a series of equally sized secondary curves, produced by another stylette in connection with a ma,gneto-electric appa- ratus working with great regularity. In the event of numerous 'experiments being required in any particular investigation, the whole apparatus should be permanently fixed to a table, which is also used as the operating table, and on which thp animal lies. Experiments on Eespiration. 1. Expiration of coA-ionio acid hy the limgs. — This may be readily demonstrated by breathing through a glass tube into lime-water. The lime-water becomes mUky from the forma- tion of insoluble carbonate of lime. The amount of carbonic acid expired may also be determined by causing an individual EXPERIMENTS ON, RESPIRATION. 561 to breathe for an hour air which has been carefully purified by passing it through caustic potash. He must inspire this pure air and expire through a solution of caustic potash, the strength of which IS known, and which may be weighed. The increase in weight, due to the carbonic acid, indicates the amount of the latter ; or the amount of carbonic acid may be calculated, by the chemical rules of equivalence, from the amount of carbonate of potash formed. 2. .Expiration of aqueous vapov/r hy the lungs. — The amount of aqueous vapour may be estimated by breathing air (dried by passing through sulphuric acid) through an apparatus con- sisting of several U-tubes containing chloride of calcium, or pumice-stone steeped in sulphuric acid. The increase in weight wiU indicate the amount of aqueous vapour expired in a given length of time. 3. Mode of measwing the quaMity of air in inspiration and expiration. (See pp. 228, 229.) — This is done by means of instruments termed spirometers. (1.) Spirometer of Mr Hutchinson {spiro, I breathe ; /urgoii). — This is essentially a gasometer, consisting of an outer cylinder, having introduced at its base a pipe, leading from a mouthpiece, and rising in the centre of the cylinder nearly to its brim. Into this cylinder another one is inverted, which is carefully balanced by two cords passing over two pulleys, and suspending two weights. When air is forced into the tube already mentioned, and the outer cylinder contains a certain quantity of water, the inner cylinder rises. The amount of air is indicated by a. scale, graduated into cubic inches, which is attached to the inner cylinder, and consequently rises with it, the amount being marked off by an index fixed to the outer cylinder. The inner cylinder is provided with a stopper, by removing which, and forcing down the cylinder, we are enabled to expel the air. This instrument does not give accurate scientific results — the muscular strength of an individual influencing the amount of air forced from the luug, independently of the pulmonary capacity. (2.) The Anapnograph of Bergeon and Kastus {avairnii, to draw breath ; ygapft)).^The principle of this instrument is quite different from that of Mr Hutchinson. It is seen in Plate XXI. fig. 22. It consists of two parts : first, an arrangement of clock-work for carrying a sheet of ruled S62 PRACTICAL EXPERIMENTAL PHYSIOLOGY. paper, P 0, placed in a brass box, M N' ; and second, of another apparatus consisting of a rectangular box, R, into one side of -which we have fixed an india-rubber tube, termi- nating in a cover for the nose, as seen at O. . The other side of the box is quite open, as at V. A section of the box is seen at C. In its interior there is a vertical plate of aluminium, moving freely on a hinge, at the bottom of the box. This plate, seen in C, 3 — 2 acts as a valve during inspiration and expiration through the box. In inspiration the valve is drawn towards the nose, as indicated by the dotted line in C, 3 — 4 ; and in expiration it is forced in the opposite direction. To the edge or border of this valve there is attached a long light lever, K, having at its free end a pen, P, which, as the lever is moved by the valve, makes a tracing upon the paper. It is important to observe, as will be seen on examining 0, that when the valve is forced from the nostrils in expiration, the pen point will move in the opposite direction ; and the reverse holds good in the case of inspiration. The whole of the tracing on the left of the median line of the paper, therefore, represents the curve of expiration, while that on the right represents that of inspiratioli. Thus we obtain a tracing of the inspiratory and expiratory curves. The amount of air of inspiration and expiration is calculated by having the paper carefully divided into squares, so that in ordinary respiration sixteen squares represent half a litre of air, while in forced respiration, four squares represent only half a litre. Thus by counting the number of squares within the curve, we obtain a knowledge of the amount of air. For ordi- nary respiration the apparatus is as shewn on Pig. 22, and the pen hangs loosely. In this condition forced respiration would drive the pen point beyond the margins of the paper, and perhaps damage the instrument. To obviate this, by turn- ing the small button B, seen near the top of the box, pushing it downwards in a little slit, and again fixing it, the lever is rendered much less easily moved. This instrument is easy of application, and is more accurate than that of Hutchinson. Experiments on Sight or Vision. The practical experiments which may be performed with reference to sight are so numerous that we can only select a few of the more important. 1. Inversion of the image upon the retina. — This may be illus- EXPERIMENTS ON VISION. 563 trated by the student examining the inverted image upon the ground glass plate in an ordinary photographic camera. It may be also done by taking the eye of an ox newly kUled, or still better, that of an albino rabbit, carefully separating the sclerotic from its posterior surface, and fixing it in a hole in a shutter, the pupil being directed forwards, while the observer is in the dark room examining the retina. 2. Action of the muscles of the eye-halL — The ophthalmotrope of Rente (ofSaX/MS, the eye ; rgoirri, a turn). By means of this instrument, seen in Plate XXI. fig. 23, we are enabled to study the actions of the muscles of the eye-ball. It consists of a wooden box, h, supported by levelling screws, i k. From the surface of the box there rises a brass pillar, g, bearing a frame- work in which there are mounted the accurate models of two eye-balls. These latter consist of box-wood frames, having passing through their centre a brass tube, bearing on. its anterior part a glass, representing the cornea, behind which there is a diaphragm, like the pupil, while its posterior end consists of a disc of ground glass, which stands for the retina. The six muscles acting upon each eye-ball are represented by as many delicate silk cords, accurately fixed to their proper posi- tion on the eye-ball. Prom thence they pass backwards through two brass plates, c d, then over a number of ivory pulleys down- wards towards two scales, / /. The back of one of these scales is seen in Kg. 23, A. Each cord has attached to it a small piece of tinfoil, which serves as a pointer. The sUk cords are ulti- mately attached to a roller in the box h. The peculiar position and direction of the superior oblique muscles of the eye-ball are imitated by a movable arm seen near the inner surface of the eye-ball as. By turning with the fingers the eye-balls of this ophthalmotrope, the action of the various muscles may be observed, and the angles formed by the lines of direction of the muscles measured. Numerous other experiments may be per- formed with it. By placing a wax candle eight or ten feet in front of the ophthalmotrope, the position of the inverted images on the retinae, corresponding to any given direction of the 'rtsual axes, may also be studied. Measurement of the Curoatwres of the Cornea and Lens. The cornea being a transparent structure, acts both as a lens and as a convex mirror. It acts as a lens by refracting to a 13 S6/^ PRACTICAL EXPERIMENTAL PHYSIOLOGY. slight extent rays of light passing through it, and it acts as a convex mirror by reflecting rays of light from its surface. It is the latter property that is taken advantage of in the method of making accurate measurements of its radius of convexity. Formation of images hy convejc mirrors. — The image produced by a convex mirror is an erect image apparently placed behind the mirror. This will be understood by referring to Plate VIII. fig. 21. Here A P is a convex mirror, and C is the centre of the' circle of which C D is, the radius, and A P is an arc. If the eye of the observer be placed at E, a reflected and erect image of the arrow M N will be seen at m n, but reduced in size. Of the numerous rays of light reflected from the surface of the mirror, only a few can enter the eye, and those which do, such as D E, F E, G E, and H E, are so reflected that the angles of incidence and reflection are equal. The ray M D is reflected in the direction D E, the angle of incidence M D N being equal to the angle of reflection N D E. ■ The same is true of the rays M E, N H. By carrying back the rays E D, E F, they will be found to meet at the point m, and they will appear to an eye placed at E as if they had come from their focal point m. In the same way the rays E G, E H, will apparently issue from n, — all the points composing the image m n being foci coiyugate to the points composing the object M N. The small image m % will therefore be the virtual image of M N. By drawing the lines M C, N C, it will also be found that the virtual image m n is always within those lines, hence the image is erect and always smaller than the object. It is important also to recollect that the size of the image m n. is to the size of the object M N as the distance of the image from the centre of the mirror m C is to C M, the distance of the object. The image m n will recede from the surface of the mirror, as the object M N recedes from it, and when the object M N is indefinitely, distant, as it often is in the case of objects placed before the cornea, the image m, n wiU be situated about half-way between the mirror and C, that is at a point corresponding to half the radius of convexity. It follows also from this, that the greater the degree of convexity of the surface of the mirror, the smaller will be the virtual image, a fact which may be easily demonstrated by compai-ing the sizes of the reflected images in convex mirrors of difierent degrees of convexity. Formula for calculating radius of curvature of cornea. — When EXPERIMENTS ON VISION. 565 ■we apply these principles to the cornea, we find that it acts as a convex mirror, having a virtual image behind it at a point situated at a distance, of half the radius of its convexity. The size of the image must be measured, and from its si^ the radius of curvature may be Calculated thus : E-F Let C D in the above Figure be the cornea, and E F H its optical axis. The object A B, placed before it will be reflected by its surface, so that its virtual image will be a h, placed at F, that is at a distance of half the radius E G. Draw th^ lines A 6, B J. The object A B will be to the image a 6 as the distance H G is to G P, that is half the radius. Let E = the radius — AB:a6 :: HG:GF (that is half B) .HG X a6 iE = AB o,« = .(=iL|^) Thus let A B = 1000 mm. ; ah,l mm. ; and H G, 3800 mm. ; what is the radius of curvature ? ^ 1000 E = 3'8 X 2 = 7-6 mm. Optical principles of the ophthalmometer. — The instrument by means of which we measure the size of the reflected image on the convex surface of the cornea or lens is termed the Ophthal* mometev (o^feXjitos, the eye ; /iirgov, a measure). This ingeni- ous instrument was invented by Helmholtz. In order to understand its practical application, it is necessary, in the first instance, that we examine the optical principle on which it is constructed. When a ray of light falls perpendicularly on the surface of a glass plate, it passes through it without under- S66 PRACTICAL EXPERIMENTAL PHYSIOLOGY. going any refraction. If, however, the plate be held obliquely to the direction of the ray, as seen in the accompanying figure, ■we obtain a different result. Here A B C D in the above figure represent a plate made of flint glass, having the ray a c impinging upon its surface. It is refracted in the direction a i, and on passing again from the flint glass into the air, it is a second time refracted in the direction i I, — i I being parallel with a c. Draw a line perpendicular to A B, namely n c, and continue.it to k. The angle a cnia equal to the angle m i I, being produced by parallel lines falling on parallel surfaces. The angle a bears a ratio to the angle ^, — the angle of refraction. The iadex of refraction of flint glass is 1'6. Hence the sine of the angle a = 1'6 (sin ^). Conse- quently, if the eye be situated at I, the point a will not be seen at a, but at 6, in the direction of the line Ifb. The glass plate, therefore, effects a displacememt of the point a to the right, and to an extent indicated by the length of the line a h. As yet we do not know the length of a b, but it may be represented by the liae c /, which is equal to ffl 6 by parallel lines. The line c/ we will term e. In the triangle c f i, cfis opposite to the angle c if, and c i is the hypothenuse, therefore — : — := Sm I f. CI •' and therefore e ^ c i • sin c if. But e has not yet been measured, neither do we know the length EXPERIMENTS ON VISION. S^7 of c i, nor the angle c if. We must now find c i. This line is, as the figure shews, the hypothenuse of a triangle cih ; and one of the sides of this triangle, c h, ia equal to the thickness of the glass plate, which we will term P. The line c h '\% ad- jacent to the angle e i h, and hence we get P by multiplying o i, we have P = cos /3 • c i, wherefore cos |8. Now we know that P equals the thickness of the glass plate, and that the sines of the angles a and /3 are in a known ratio. But by substituting the value of c i in the previous equation, we have p e =: — sin c i f. cos j3- We see now that the c i f equals h i f — hie; but h i f equals the angle of incidence a, in that their sides are parallel ; and hie equals the angle c& refraction jS, because they are alternate angles. Therefore e i f equals a — 18, and sin c i / = sin [a, — j8). We have therefore the following formula : (e representing the amount of displacement of the point a towards b and P the thickness of the plate). ,_p sin(« — )3 ) cos/3. But as there are two such plates in the ophthalmometer, we have the complete formula, in which E will equal the total displacement. - „ ^ sin (a, — jS) E = 2 P '^ — —^ cos/3. The use of the ophthalmometer, therefore, is to supply us with the angle a, and as we know the thickness of the glass plates, and the index of refraction between air. and flint glass (namely 1'65), by applying the above formula, the amoimt of lateral displacement maybe ascertained. Suppose the thickness of the glass plate to be •325 mm., the index of refraction 1'65, and the angle of incidence 6°, we find, by the use of logarithmic tables, that /3 = 3° 37', very nearly. Therefore ct—^ = 6°— 3° 568 PRACTICAL EXPERIMENTAL PHYSIOLOGY. 37' = 2° 23'. This gives, on referring to the tables, e = 0'02'7 mm. veiy nearly. Bescriptioth of the ophthtdmometer. — This instrument consists of a telescope suitable for short distances, part of which is seen in Plate XXI. fig. 24, c. In front of the telescope there is a square brass box, abb, having the inner surface blackened. The box has a circular opening near 6 b, which is usually closed with a plate of very thin glass. In the interior of this box there are vertical plates of flint glass b b, fitted into frames, and moving the one at an angle with the other, by means of a rack and pinion movement, on a circular disc or wheel seen in Kg. 24, c, which is set in motion by turning the screws seen on the top and bottom of the box, the lower one being marked d. In Kg. 24,/, we see the inner surface of the bottom of the box with the circular wheel just alluded to. In connection with each pinion, and placed on the outside of the box, there are two circles made of steel, and carefuUy graduated into 360 degrees. These circles are upon the same axis as that on which the glass plates in the interior of the instrument revolve, the upper circle - corresponding to the one plate, and the lower to the other plate. There is a fixed vernier at the point a, so that by ob- serving the number of degrees on the circle opposite the zero of the vernier, we read off the number corresponding to the obliquity of the plate, or in other words, the number of degrees formed by the angle of incidence, namely, a. In making accurate observations, a number of readings should be taken on both graduated scales, and the differences between these readings should never exceed the one-tenth of a millimetre. If they do, the instrument is not in proper order, owing to the plates not moving at equal rates, or owing to a flaw in the glass. Mode of using the ophthahnometer. — The first requisite for ophthalmometrie observations, is a room having the walls blackened, and from which all sunlight can be excluded. The ophthalmometer is placed at a distance of ten feet from the eye under examination, and on a level with it. The object to be reflected on the cornea, until recently, was the distance between three candle flames placed beside the experimenter, two being on his right hand and one on his left. Helmholtz has, however, now substituted for this an apparatus consisting essentially of three small reotangida/r mirrors fixed by universal joints to a graduated wooden rod about foul: feet long. The EXPERIMENTS ON VISION. 569 distance between the mirrors may be regulated by sliding them in moveable sockets along the rod. In the centre of the rod there is a circular movement round a graduated scale, so that the rod may be placed vertically, obliquely, or horizontally, according as it may be desirable to obtain images in a vertical,, oblique, or horizontal meridian of the cornea. This mirror- apparatus is screwed to a table immediately in front of the ophthalmometer. A. candle flame is now placed on the right or left hand side of the eye to be examined (for the right eye on the right side and for the left eye on the left), as near it as possible, and on the same plane, a dark screen intervening, so as to pro- tect the eye from the glare of light. The experimenter now throws, by means of the mirrors, a reflection of the light from each mirror upon the eye. He then directs his own eye to the telescope of the ophthalmometer, and by carefully focusing, the instrument, and directing it to the eye under observation, he sees three minute specks of light, thus * * * on the cornea. The vernier of each scale of the ophthalmometer is now at zero. Then, by turning the screws already mentioned, the glass plates in the interior of the box are placed obliquely, and the motion is continued until six small specks of light are seen thus : — * * * » « * 1 a 2 & 3 c Here the asterisks numbered 1, 2, 3, represent one-half of the amount of displacement in the one direction, and those marked a, 6, and c, half the displacement in the other direction. Thus the three original images have been displaced through a distance equal to that between the two extreme images. The number of degrees through which the plates have moved are now read off, giving the angle of incidence, and by means of the calculation above described, the size of the image is ascertained. The fol- lowing measurements are now made : First, the distance between the upper and lower reflecting mirrors — this gives the size of the object; and second, by a tape line divided into milli- metres, the distance from the anterior surface of the cornea to the centre of the apparatus bearing the mirrors ; but as these reflect rays of light from the candle flame, this measurement must be doubled. We now know the size of the object, the size of the image, and the distance of the object from the cornea ; and from these data, by the formula already given. S70 PRACTICAL EXPERIMENTAL PHYSIOLOGY. the radius of curvature is easily calculated. (For an example, see p. 565.) Dondeir^s method of vtimg the ophthalmoTneter. — This is an easier, though a less accurate, mode of measuring reflected images. It consists of preparing a scale, in. which each degree, or fraction of a degree, corresponds to a certain size in millimetres. The mode of constructing it is as follows : Place a small white ivory scale, divided into tenths of a millimetre, at a distance of ten feet from the ophthalmometer. Turn the plates until the lines on the scale diverge and ultimately pass through any given distance, say ^V of a millimeter, J, \, \, J, •^, f, or 1 millimeter. The number of degrees corresponding to each of these displacements is noted, and thus a scale, by numerous observations, may be readily constructed. Observations are to be made on the living eye as described. When the distance between two reflections on the cornea, representing the image, has been displaced through its whole extent, the number of de- grees are noted, and on referring to the scale of measurements prepared as above, the size of the image is at once known. Measwements made hy, means of the ophthahnometer. — We give here various measurements in millimetres made by means of the ophthalmometer, which are intended to serve as standards of comparison for students or others who may make a special study of, and devote time to, the subject :* Optical Cokstahtb. Myopic eye. Kna]pp. Hypermetropic eye. Woinow. Presbyopic eye. AdamM^ ajnd Woinow. Rest. Aocom- moda'n. Rest. Acoom- moda'n. Rest. Accom- moda'n. Kadius of cornea . Radius of anterior surface of lens Radius of posterior sur- face of lens Distance of anterior sur- face of lens from the cornea Thickness of the lens . Focal distance of the lens Index of refraction of the cornea, aqueous humour and vitreous humour . Index of refraction of the lens .... 7-2053 9-0641 6-4983 3-4786 3-6225 43-133 l-3465t l-4545t 7-2063 5-0296 5-0855 2-8432 4-2579 30-939 8-00747 9-3785 6-2480 3-6175 3-6826 44-9616 ... V 8-00747 5-2904 4-9714 3-0028 4-1972 31 -188 7-15568 10-2021 6-2156 3-23731 13-96269 46-357 7-15668 8-6975 6-0001 -2-98986 4-21fll6 38-1513 ' M. Woinow, Ophthalmometrie, Wien. 1871. t Helmholtz, Physlologische Optik. • EXPERIMENTS ON VISION. 571 The apparatus of Enapp for holding the head.* — This ap- paratus, designed by Professor Knapp, now of New York, is for the purpose of securely holding the head of the individual whose eye is being examined with the ophthalmometer. It is composed of a circular piece of wood placed vertically, which may be turned round on an axis, and which has holes cut for the nose, eyes, and mouth. The head is held steady by two flat pieces of wood, which are moved by screws so as to be applied, one to each side of the head. These are well padded. Tlie phakoseope of Hdmholtz ( Let the individual whose eye is to be examined, be seated in a dark room on a chair of a convenient height, and place a gas light, furnished with a ground-glass shade, or a moderator lamp, immediately behind his shoulder, and yet close to the side of his head. Let the light be on a level with the eye, and so far behind it that the countenance is in the shade. If this cannot be so arranged, place a dark shade between the eye and the light. The student is now to sit down opposite, take th@ mirror in his right hand and apply the back of it to his own eye, at a distance of about eighteen inches from the eye under examination, and looking carefully through the small hole iu the back of the mirror, he so moves the latter as to catch the rays of the light from the lamp, and to reflect them into the patient's eye. He must now take the biconvex lens between the forefinger and thumb of the left hand, and hold it at a distance of about an inch in front of the patient's eye, keeping' the hand steady by resting the- little finger on the forehead of the patient. Then by a slight backward and forward move- ment of his head and the mirror, the student will succeed in catching the proper focal distance, and the image of the retina will then be distinctly seen. In the axis of the eye-ball the yellow spot (pnacula lutea) may be seen forming a slight oval patch, and having in its centre a small bright dot, the fovea centralis, the thinnest part of retina. About the 1-lOth of an inch to the inside of the yellow spot, we now observe a white or rose-coloured round spot, bounded by a well-defined border, and having radiating from its centre a number of minute vessels. This is the entrance of the optic nerve, and the vessels are branches of the central artery of the retina. It is sometimes termed the optic disc {porus opticus), and it has also been called the optic papilla, because at this place the nervous substance of the retina is slightly elevated, so as to form an eminence {aolliiyaliis^ neni optid). The neighbourhood' EXPERIMENTS ON HEARING. 573 of the optic disc and yellow spot is usually of an orange-red colour, and is richly supplied with branches of the retinal vessels. The yellow spot is seen most distinctly when the individual looks straight f oirward, and the optic disc is demonstrated when the eye is rolled a little inwards. By causing the patient to move his eye in different directions, the whole surface of the retina may be examined. Experiments on Hearing. This department of practical physiology has become, chiefly owing to the brilliant researches of Helmholtz, one of the most inviting fields of study. Before entering upon it, however, the student should be familiar with the general principles of acoustics explained at pp. 129, 134. The following are a few examples of the kind of apparatus used, and the experiments performed. Helmholt^s model for eicplaining the mechanism of the hones of the ear. — ^This is a model of the tympanum, having accurate models of the mcdleas, incus, and stapes, moving upon each other by joints, and having attached to them, at the proper points, cords which run in the direction of, and represent the muscles of, the tympanum, viz., the tensor tympani, laxator tympani, and stapedius. By tightening or relaxing these cords, the action of the chain of bones or the membrana tym/pa/ni, on the one hand, and on the membrane covering the fenestra ovalis, on the other, may be easily demonstrated. It may also be shewn by means of this apparatus how the vibrations of the air com- municated to the membrana tympami are carried onward through the chain of small bones to the fenestra ovalis. Monochord of Helmholtz. — This is an apparatus consisting of a long narrow box, on the upper surface of the lid of which there is a cord drawn tightly over two ivory bridges, placed one at each end of the box. There is also a bridge, of the shape of that of a violin, which may be moved in any direction beneath the cord ; and thus it may be shewn that vibratiog 'cords of different lengths produce various musical notes. Attached to the instrument there is a trumpet-shaped resonating apparatus, having the wide end covered with a delicate membrane. This part of the apparatus may be moved along the side of the box, so as to be opposite to any given point of the vibrating ^11^ PRACTICAL EXPERIMENTAL PHYSIOLOGY. cord, and the note corresponding to the vibrations will be dis- tinctly heard. The apparatus of Appunn for illustrating the researches of Helmholtz, adapted for physiological purposes.— This is an appa- ratus invented and made by Georg Appunn, of Hanau, near Prankfort-on-the-Maine.* . It consists of a strong table pro- vided with a bellows and air-chest. The entrance of air from, the bellows into the chest is regulated by a valve, which may be opened or shut at pleasure. On the top of the table there are six square holes communicating with the air-chest, each being provided with a sliding valve, which can be opened or shut by a rod attached to it. These square holes serve as sockets, into which we can 'fit the different parts of the apparatus. When we wish to use any partipular instrument, the valve beneath it is opened, and thus air is at once admitted into it from the air-chest. The following are the principal parts of the apparatus : — 1. An over-tone apparatus. — This part of the instrument con- sists of a rectangular chest, having in" its interior sixty-four metallic tongues, placed transversely, and carefully constructed, so that the vibration of each produces a certain musical tone. Suppose we were to divide a vibrating cord into equal parts of i, I, I, I, I-, and so on up to the l-64th of its length, we would obtain the tones of this apparatus. Underneath each tongue there is a sliding stop, which has a short metallic rod attached to it. The end of each rod is finished with a small knob, by pulling out which, the sliding valve under any particular tonguie may be withdrawn, and the corresponding musical tone produced by working the bellows. In order to maintain the sound while the bellows is refilling, the top of the box of the over-tone apparatus moves upwards and downwards like an accordion, and the tongues vibrate whether the air passes from below upwards, or frdm above downwards. By means of this apparatus, as we can sound several notes at the same moment, the peculiar colour, or timbre, or, according to Hehnholtz the Marig of a musical note may be demonstrated. Every musical note contains not only its fundamental tone, and over- tones, but also other tones called the octave, the duo-decimo, double octave, &c., the ratio of the vibrations of which are as 1:2:3:4:5:6:7, and so on. In order to detect these ovex*- * Ueber die Helmholtz' sche Lehre vou den Tonempfinduugeiij &g. EXPERIMENTS ON HEARING. S7S tones, we require a series of instruments termed resonators. These are globes or cones made of copper or tin, and each one is so constructed that the air in its interior is thrown into vibration by one of the over-tones iii the musical note. With Appunn's apparatus, twenty-nine of these resonators are sup- plied. They vary in length from 4^ feet to 3 inches, and they are all conical and made of tin. The narrow end is placed close to the ear, and the base directed upwards, and if possible the observation should be made at a distance from the place or instniment from which the sound issues. The presence of over-tones in a musical note may be shewn by sounding the fundamental tone. Then, by withdrawing the stops cor- responding to the different over-tones of that particular note, we find that its colour or quality depends on the different nuinber and relation of the over-tones. It is this fact which explains why the same note on a flute, a clarionet, a piano, or a trumpet, differ from each other in quality. The fundamental tone is the same in each, but the number and relation of the over-tones vary. The soft note of a flute contains fewer over- tones than the same note sounded on a trumpet. Tor instance, if we sound on the over-tone apparatus the notes in the propor- tions 1:2:3:4:5:6:7, &e., which are the over-tones of the fundamental tone ^ 1, the sound becomes stronger and rougher as we proceed. This illustrates the law laid down by Helmholtz, that "The more over- tones a compound note contains, the rougher is its quality or timbre." The quality of the voice in different individuals depends on the number and strength of these over-tones. Another method of observing the over-tones is to sound the fundamental note on the over-tone apparatus, and the students may hear distinctly the various over-tones corresponding to the particular note by listening with the resonators at the other end of the room. In order to sound the fundamental note with volume and intensity, so that the over-tones may be detected in a room with a large audience, Appunn's apparatus is provided with two powerful tongue-pipes. These consist of rectangular wooden pipes, having at the top a wedge-shaped box, the apex of the wedge pointing downwards, and furnished with a vibrating metallic tongue. A large cone made of tin is fitted, apex down- wards, into the top of the pipe. This acts as a powerful S7(> PRACTICAL EXPERIMENTAL PHYSIOLOGY. resonator, ami the note produced by the metallic tongue is increased in intensity. After some practice with this instrument, one can detect the over-tones even without the resonators. The resonators do not produce the over-tones, but the confined mass of air -within them, by its vibrations in unison with those causing the over- tones, strengthens the latter, and renders them appreciable to the human ear. The over-tones are not therefore formed in the ear, as was supposed before the researches of Eelmholtz, but they are produced in the air surrounding the apparatus causing the fundamental note. The production of comhination tones. — If, by the over-tone apparatus, we sound two notes of different pitch at the same time,, and if they correspond in strength, we may hear, by using a resonator, not only the two primary notes, but a third, which is deeper than the primary. This is termed the combination or ground-tone, first discovered by Andreas Sorge in 1740, and investigated by a violinist, Tartini, and often called after the latter, Tartinian tones. For instance, if we sound two notes on the over-tone apparatus, the proportion of whose vibrations are as 2 : 3, or 3 : 4, or 4 : 5, or 6 : 7, or 7 : 8, we hear the ground tone, which is always, in this case, the tone whose vibrations are as 1 = C2. The student, until his ear is accustomed .to the apparatus, should sound the notes 16 : 20, or 20 : 24, or 24 : 28, and he will easily hear the deep ground torie, the vibrations of which will stand in the arithmetical ratio of 4 to the figures just given. In the same way the proportions 16 : 18 : 20 : 22 : 24 produce a ground-tone =: 2 ; those of 15 : 18 : 21 : 24 : 27 pro- duce tone = 3 ; and so on. The production of difference tones. — The difference tone is that in which the number of its vibrations are equal to the difference between those of the two primary tones. For examplBj suppose we sound on the over-tone apparatus two notes, the ratio of whose vibrations are as 16 : 20. The difference tone will have a vibration of 4, that is, 20 — 16 = 4. But the vibrations of 1 (the lowest in the over-tone apparatus) = 32 iu the second. Therefore, the vibrations of 16 will be 16 X 32 = 512 ; of 20 will be 20 X 32 = 640 ; and of the difference tone will be 4 X 32 = 128 vibrations in an equal period of time. This tone was first discovered by Helmholtz. The production of svimmation tones. — When we sound two EXPERIMENTS ON HEARING. 577 tones of unequal pitch, but the ratio of the vibrations being as 16 : 18 : 20 : 22 : 24, &c., we obtain not only, as already described, a fundamental or ground tone, and a difference tone, but we also produce a third called a summation tone. For example, if we sound on the over-tone apparatus the tones 4 : 6, we hear, by means of resonator No. 10, another tone, the vibrations of which are in the proportion of 10 : 4 : 6. We hear in those circumstances a musical chord, thus (e ■=■ summa- tion tone) : C : G : e 4:6 : 10 And in the same way by sounding 1 : 2, 2 : 3, 3 : 4, or 4 : 5, we may produce the corresponding summation tones, 3, 5, 7, 9, &c. ; and these summation tones may be heard with resonators 3, 5, 7, 9, &c. By this apparatus also, even higher tones may be obtained. Thus, when we sound 2 : 3, we may hear the deep difference tone ^ 1 ; at the same time the summation tone 2 + 3 = 5; and with care, by increased attention, we may hear another tone, the ratios of whose vibrations are as 2 X 2 -|- 3 = 7 ; and even a third, namely, that produced by 2X2 + 2X3 = 1 0. Thus, when we sound 2 : 3, and provide four individuals with the resonators marked 1, 5, 7, and 10, each will hear distinctly the tone corresponding to the resonator he employs. 2. An appa/ratua to demonstrate deep difference tones. — This con- sists of two tall organ pipes placed at the end of the table, and communicatingwith the air chest. These pipes are of equal length, but each is furnished with a stop attached to a vertical rod, by which the length of the vibratiug column of air in the one may be made to differ from that in the other. _ When the stops are so arranged that the columns of air in the two pipes are equal, and the bellows are worked, we obtain two notes so perfectly in unison as to be undistinguishable. If, however, the length of one of the columns of air be diminished by pushing down the atop, the rate of vibration is changed in that pipe, and we hear two notes or impulses alternating with each other ; a kind of shake. It may also be shewn that these impulses inci'ease in rapidity as we augment the difference between the lengths of the columns of air in the two pipes, that is as the vibrations in the two differ. And it may be demonstrated that the number of impulses per second is always equal to the difference between the rates of vibration. Sr^jPIiACTICAL EXPERIMENTAL PHYSIOLOGY. 3. A Vocal apparatus. — This will be described with the expe: ments on voice (see p. 579). 4. Apprmn's tone-measm-er. — This consists of an apparat similar in structure and appearance to the over- tone app ratus already described. It contains thirty-three tones, mark( 0, 1, 2, 3, 4, 5, &c., on to 32 ; and these tones are so arrange that the difference between the vibrations of any adjacent tw such as : 1, or 1 : 2, or 2 : 3, and so on, produce, when sound( together, exactly four impulses per second. In the same wi when : 2, or 1 : 3, or 2 : 4 are sounded, we have eight impuls per second ; again : 3, or 1 : 4, or 2 : 5 give sixteen impuls per" second, and so on. With this instrument we can readily d termine the number of vibrations in any given tone (see p. 347 Experiments on Voice. The human voice is produced by the vibrations of the tn vocal cords (p. 351). This may be illustrated in several way 1. By Mallet's artificial larynx. — This consists of a woode tube of the form seen in Plate XXI. fig. 25, /, having at e brass frame-work for holding a piece of india-rubber tub and moving on a hinge, so that the margins of the latter ma be separated or approximated, or relaxed or rendered tense. blowing through the end of the tube, various sounds are pri duced according to the degree of tension of the India- rubb( margins. It may be shewn that as we increase the tension i these, the pitch of the sound rises, while it is lowered when v remove the tension. 2. By Mailer's apparatus for experimenting on the vocal con themselves. — A view of the principal portion of this apparatus seen in Plate XXI. fig. 25. It consists of a broad wooden stani having two Or three strong uprights, provided with numeroi holes and screws, by which the larynx may be attached. In Fi 25, the anterior part of a human head, with the larynx le attached to it, is afiixed to the apparatus. Into the trachf there is inserted and securely fastened the bent wooden tube by which air can be forcibly blown upwards through the glotti When this is done, a sound is produced, which may be increase in pitch in two ways : 1st, by means of the rectangular force] a, movable on the steel rod b, which grasp the larynx ar thus approximate the cords; or, 2nd, by fixing a small hoc into the anterior and upper border of the thyroid cartilage, ar EXPERIMENTS ON VOICE. 579 carrying a thread from this hook over the pulley c. By placing weights in the scale or cup 6 d attached to the thread, the thyroid cartilage is pulled forwards and the cords tightened. Instead of using part of a head, as shewn in Kg. 25, it is more satisfactory to make a special preparation of a lamyx, by removing it from the neck, clearing it from the muscles, and by cutting off the upper part down to the level of the true vocal cords. It may then be clearly demonstrated that voice is pro- duced by the vibrations of these cords, and numerous experi- ments may be performed, shewing how they are influenced by the various muscles, and the change of note consequent thereon. Formaiicm, of vowel sounds. — These may be illustrated by the special apparatus made by Appunu, already alluded to. It consists of a combination of wooden organ pipes, having stops so that air may be admitted into one, or more at pleasure. It maybe shewn that the vowel a consists of a fundamental note and of certain over-tones ; the vowel e of a fundamental note and other over-tones, and so on. The fundamental note is produced by the vibrations of the cords, and is the same for all the vowels ; but the over-tones are produced in the upper part of the larhyx, and are modified by the resonance of the mouth. It is well known that the vowels, if sounded by different voices, have not the same quality or timbre ; a fact due partly to the over-toneg varying in different individuals, and partly to the effect of resonance of the oral cavity, which also varies in shape. (See p. 353.) 3. The Laryngoscope. — The idea of illuminating and render- ing the larynx visible by means of a reflector, has been more or less attempted by Listen, Warden, Avery, Garcia, and others, but abandoned as impracticable in medicine, until successfully revived in recent times (1858-59) by Professor Czermak. For the examination of the larynx he employs, 1st, a perforated mir- ror, by means of which a powerful light is thrown from a lamp into the back of the mouth, and through which the operator gazes in the direct axis of the illuminating rays. This mirror may be attached to a bent stalk, the end of which can be held firmly by the teeth, but it is far more conveniently, for purposes of demonstration, held firmly in the left hand. 2d, A laryngeal mirror of glass or steel, varying in size, attached to a stem at one of its corners, which having been previously warmed to pre^ 14 S8o PRACTICAL EXPERIMENTAL PHYSIOLOGY. vent condensation of the breath, upon it, is placed in front of the uvula, and reflects the image of the rima glottidis to the eye of the observer. The person examined should place his hands upon his knees, the upper part of the body is advanced forwards; the neck bent onwards, the nape slightly inclined backwards, the mouth widely open, the tongue flattened and held a little without. The observer is seated in front of the person to be examined ; he places in his mouth the handle which supports the illuminating mirror, and looks through the central opening ; the laryngeal mirror, introduced into the back part of the mouth with the right hand, is illuminated by the light which is projected from the illuminating mirror. In the first place, the illumination of the back part of the mouth and the mutual position are regu- lated ; then the laryngoscope is heated, and its temperature regulated by the touch. After these preliminaries are gone through, the patient should open the mouth wide, and alternately inspire and expire deeply. While doing so, the laryngoscope is placed against the uvula and the velum palati, to sustain ' these parts a little, and the mirror is given a convenient incli- nation ; at times it is impossible to avoid touching the posterior wall of the pharynx ; the examination is directed by the image we thus obtain. On telling the patient to pronounce ah ! the movement of the vocal cords is seen. Practice and reflec- tion will bring each observer to comprehend the modifications to which he ought to submit this proceeding, according to the special circumstance; whether, for instance, he has in some degree to advance or to withdraw the laryngoscope, to bend it, to lower or to elevate it, to change the position and attitude of the individual undergoing examination, raise his chair. For the performance of many experiments, more especially those on the nervous centres and individual nerves, anatomical knowledge and operative skill are required. T6 these we have not specially alluded, neither do we profess to have exhausted those for which particular instruments have been indented; but enough has been said to illustrate this department of physiology, and to assist the student in making himself familiar^ practically, with the use of the extensive apparatus he wiU find in the laboratory. INDEX. Abducens, sixth nerve, 318. Aberration, chromatic, cause of, 140 ; how corrected in microseope, 601 ; spherical, cause of, 137; how corrected in micro- scope, 600. , Absorption bands of spectrum of blood, 32 ; and secondary digestion, 239 ; of gases, 122 ; of oxygen in respiration, 227 ; by the skin> 269. Acetic acid in urine, 477, 485 ; use of, in Histology, 620. Achromatic lens, description of, 601. Achromatism, principle of, 601. Acid, acetic, 22 ; acetic in urine, 477 ; adipic, 23 ; arachidic, 22 ; benzoic in urine, 477;, butyric, 22; caproic, 22; caprylic, 22 ; carbonic, 28 ; cerebric, pre- paration of, 494 ; cerotic, 22 ;. chromic, use of, in Histology, 520 ; damaluric in urine, 477 ; damolic in urine, 477 ; ex- cretolic of Marcet, 489 ; formic, 21 ; formic in urine, 477 ; free in body, 28 ; glycocholic, 12, 260 ; hippuric, 16 ; test for, in urine, 476 ; hydrochloric, 28 ; ino- sinic, 15 ; lactic, 27 ; lactic in urine, 477; lauric, 22 ; melissac, 22 ; myristic, 22 ; oenanthylic, 22; oleo-phosphoric, pre- paration of, 495 ; oxalic, 23 ; oxalic in urine, 477 ; palmitic, 22 ; pelargonic, 22 ; phenylic in urine, 477 ; propionic, 22 ; rutic, 22 ; sarcolactic, 27 ; silicic, 28 ; stearic, 22 ; succinic in urine, 477 ; sul- phunc, 28*; taurooholie, 12; preparation of, 260 ; taurylic in urine, 477 ; uric, 13 ; uric, test for, in urine, 475 ; valeric, 22 Acids fatty, 21 ; stearic acid, series of, 21 ; oleic acid, series of, 22 ; physiological importance of, 23. Acids related to sugar, 27. Aconite, effects of^ on the heart, 369. Acoustics, properties relating to, 129 ; ap- paratus of Appunn, 574. Adamiick and Woinow on the measure- ments of a presbyopic eye, 570. Adenoma, 279. Addison, Dr 'W'., on increase of colourless cells, 208 ; on cell therapeutics, 237 ; on molecular fibre, 73 ; on formation of pus, 70. Addison, Br, on disease of supra-renal cap- sules, 207. Adhesion, 110. Adipic acid, 23. ^pinus on Drebble's microscope, 497. Afferent nerves, definition of, 289. Affinity, 110. Agassiz on development of coral reefs, 411. Age, effect of, on respiration, 231 ; effect of, on the pulse, 216. Agustia, 364, Air, breathing, 229; complemental, 229; composition of, 121 ; effects of respiration on, 229 ; Pasteur's experiments on, 426 ; pump of Sprengel, 462 ; required for wards of infirmaries, 235 ; reserve, 229'; residual, 229 ; tidal, 229 ; tubes, 84. Albumin, chemistry of, 8 ; estimation of, in blood, 448 ; in egg, 399 ; in urine, tests for, 478 ; estimation of, by weight, 479. Albuminates, 8. Albuminous degeneration, 280; derivatives 12 ; principles, 8. Alcohol, use of, in Histology, 620. Alcoholic drinks, effects of, in brain, 368. Aldinl on animal electricity, 163. Aliment, nature of, 188. Alimentary canal, development of, 393. Alison onturgidity of ciliary processes, 342. Alison Scott, description of sphygmoscope of, 555. Allantoin, chemistry of, 16 ; in urine, 486. Allantois, 385. Alternate gjeneration, nature of, 405. Aluminium in. tissues, 6. Amseba, the, 40, 47. , Amaurosis, 364. Amblyopia, 343. Amentia, 362. Amici on the microscope, 498. Ammonia in urine, 471. Ammoniaco-magnesian phosphate, 29; as a deposit in urine, 487. Ammonium, carbonate, in tissues, 28. Amnios, 385. Ampere's theory of magnetism, 145 ; astatic needle, 149. Amphioxus lanciolatus, nervous system of, 390. Amyloid bodies, nature of, 25, 280 ; sub- stances in sugar, 26. AnsBSthesia, 364. Analysis of animal fluid, general, 445 ; qua- litative and quantitative analysis of, 447. 582 INDEX. Analysis' of animal solids, 489; of blood-, 447 ; of the bile, 455 ; of cartilage and bone, 493 ; of chyle, 453 ; of faeces, 489 ; ^ of gastric juice, 454 ; of liver, 495 ; of lymph, 453 ; of muscle, 490 ; of nervous system, 494 ; of pancreatic juice, 455 ; of saliva, 453; of tooth, 493; of the urine, '459 ; volumetric method of, 464 ; of white fibrous tissue, 492; of yellow elastic tissue, 492. Anapnograph of Bergeon and Kastus, 229 ; description of, 561. Anasarca, 277. Aucon sheep, case of, 415. Andral on a case of diseased spinal cord, 314 ; and Gavarret on blood in disease, 243. Anelectrode, definition of, 151. Auelectrotonus, 171. Aiigina pectoris^ 364, Angionoma, 279. Animal fluid, qualitative and quantita,tive analysis of, 447 ; general qualitative ex- amination of, 445. Animal parasitic growths, 281. Animal heat, 245. Animals, fecundation in, 378. Anosmia, 364. Aphides, development of, 414. Aphorisms regarding nervous system, 293. Apoplexy, 290, 362. Aphrodite, iridescent colours in, 140. Aphis, development of, 406. Apocynum) cannabinum, bacteria in, 439. Appunn, acoustic apparatus of, 574. Aqueous, humour, 339 ; vapour experi- ments on amount oi, in respiration, 561. Aracese, heat in spathes of, 373. Arachidic acid, 22. Archibiosis, definition of, 421. Archimedes, principle of, 115. Area germinal, 384 ; pellucida, 3S4. Areolar tissue, 76. Arlt on accommodation of the eye, 342. Armadillo, hair of, 268. Arnold on nerve cell, 65. Arteria centralis retinse, 338 ; helicinse of Miiller, 224. Arterial blood, colour of, 231. Arterial circulation, 215, Arteries, functions of the, 215 ; structure of, 84. Ascaris mystax, development of. 48. Ascherson's, Dr, haptogen membrane, 36. Ascites, 277. Asclepias cornuti, bacteria in, 439. Aspergillus, formation of, 48. Asphyxia, death by, 442; John Reid on, 234 ; mode of restoring persons suffering : from, 234; Astatic needle of Ampgre, 149. Atavism, explanation of, 418. Athermancy, 12^. Atmospheric air, composition of, 121 ; dangerous though inodorous, 331. Atom, definition of, 3. \ Atrophy, definition of, 238. Attraction and repulsion of magnets, 145. Auditory nerve, 318. Auricle, function of, 348; contractility of right,^14. Auscultation, description of, 227. Auteureith and Kerner on function of semicircular canals, 347. Avery on the laryngoscope, 679, Axis cylinder of Furkinjeln nerve tube, 96. Bacteria, development of, 47,423 ; develop- ment of, in closed cavities of body, 440 ; in laticiferous vessels of plants, 439 ; in urine, 488, Baer,Ton, on cells, 52 ; on the proligerous disc, 375. Bain on mental faculties, 299. Baker on the porcupine man, 417, Band of Bemak in nerve-tUbe, 96. Barometer, 121. Barry, Martin, on blood corpuscles, 63, 64 ; on ciliary movements, 78 ; on Graafian vesicles, 375 ; on mode of fecundation, 381. Bassi on muscardine, 439, Bastian on archebiosis, 421 ; on develop- ment of embryonal areas. 424 ; on eflecis of temperature on germs, 435 ; on pro- ligerous pellicle, 426. Batteries, galvanic, 152; bichromate of potash, 154 ; Bunsen's, 153 ; Danibls*, 152; Groves', 153 ; Smee's, 153 ; use of in practical physiology, 525. Baudrimont and Ange on respiration*of ^ZZ, 400. Bayle on gray granulations, 72. Beale, carmine fluid for injecting, 523 ; on ciliary movement, 78 ; germinal matter, 104 ; nerve-cell, 65 ; Prussian blue 4n- jecting fluid, 523 ; structure of dentin, 86 ; theory of cell-formation, 55. Beaumont on St Martin's case, 198. Bephamp on microzymes, 104. Beclard's definition of life, 184. Becqiierel and Breschet on the use of Melloni's pile in measuring animal heat, 150. Becquerel and Rodier on blood in disease, 243 ; on chemistry of blood, 240. Becquerel on chemical composition of urine, 257, Bees, development of, il2. Belladonna, physiological, effect of, 368. Bell, Sir Charles, experiments on spinal cord, 309 ; on muscular sense, 349. Beneden, Van, on development of tape- worm, 406- Bennett on diaphanous bodies in morbid formation] 44 ; on action of drugs on secretion of bile, 253 ; on leucocythas- mia, 208 ; on formation of pus, 209 ; on vegetable nature of favus, 438 ; experi- ments on germs in the air, 423, 433; molecular theory, 54 ; on pellicle on sur- face of limewater, 44; theory of cell- formation, 54 ; theory of the formation of infusoria, 429, 430. Benzoic acid in urine, 477. INDEX. 583 Bergeon and EastuB' anapnograph, 229 ; description of, 561. Berjot's amalgamating fluid, 526. Berkeley on yellow mould in pheasant, 440. Bernard on acid of gastric juice, 454; on action of bile on gastiic juice, 203 ; on curara, 82 ; on electrotonus, 172 ; method of preparing glycogen, 495; on glycogenic function of the liver, 251 ; on the nerves of the salivary glands, 195 ; on paralysis of taste, 334 ; experiments on pancreatic juice, 201 ; on section of sympathetic, 325 ; on smell, 330 ; on spinal accessory nerve, 322 ; on the portal circulation "in the horse, 224 ; Wooi'ara experiment on muscular contractility, 531 Berzelius on chemical composition of fffices, 271. Bezold, Von, on nerves of the heart, 321 ; on rapidity of nerve current, 287. Bibra, Von, on analysis of bone, 92 ; on muscle ash, 75 ; of tooth; 87. Bichats^dBfinition of life, 184. Bichromate of potash battery, 154. Bidder and Schmidt on amount of bile, 260 ; on quantity of digestal fluids, 204 ; on a case of gastric fistula, 198 ; on acid of gastric juice, 454 ; on intestinal juice, 204 ; on amount of saliva, 106. Bile, description of, 203 ; as an excretion, 250 ; action in digestion, 203 ; action of, on chyme, 201 ; analysis of, 455 ; colour- ing matters of, 32; effects of drugs on, 253 ; as affecting colour of faeces, 272 : estimation of fat and cholestrin in, 455 ; estimation of solid matter in, 455 ; mu- cus of, 455 ; Noel's test for, 458 ; quantity of, 204 ; reaction of, 455 ; specific gravity of, 455 ; in the urine, 484. Bile acids, as albuminous derivatives, 12 ; as excretions, 250 ; modes of separating, 45s ; and pigments, optical properties of, 457 ; Pettenkofer's test for, 458 ; tests for, 468. Bile pigments, mode of preparing, 457 ; silver oxide test for, 458. Bilhartz on nerves in electric fishes, 160. Biliary acids in fsBces, 273; calculi, nature of, 458; concretions, '280. Bilifuscin, chemistry of, 33. Biliphffiin, chemistry of, 33. Bilirubin, chemistry of, 33 ; reactions of, 457. Biliverdin, chemistry of, 33 ; reactions of, 457., Bipolar nerve cells, 65, Birds, fecundation in, 381 ; fungi in cavi- ties of, 440 ; Bainey on lungs of, 226 ; spermatozoids in, 380. Bischoff on biliary acids in fceces, 273 ; on development of ovum, 383 ; on spinal ac- cessory nerve, 322, Bismuth test for sugac in urine, 481. Bladder, development of, 396. Blake on rapidity of circulation of poifions, 219. Blaachard on development of tape worm, 406. Blane, Sir Gilbert, on reflex actions, 311. Blastema, definition of, 58. Blood, description of, 239 ; amount of, in adult, 241 ; analysis of, 447 ; in Bright's disease, 243 ; Chauveau on rapidity of circulation of, 219 ; chemical constitu- tion of the, 239 ; circulation of the, 212 ; colour of, 231 ; colouring matter of, 31 ; alterations ofbloodin structure in disease, 243; diseases of the, 246 ; effects of respira tion on, 231 ; estimation of albumin, 448 ; of coagulum, 440 ; of colouring matter, 449 ; of extractive matter, 448 ; of fat, 448; of fibrin, .448 ; of iron in, 450 ; of mineral matter, 448 ; of serum, 449 ; of water, 448 ; function of the, 241 ; gases of, 452 ; morbid conditions of the, 241 ; in nutrition, 236 ; portal, description of, ! 249 ; pressure, mode of measuring, 658 ; rapidity of the, 219 ; specific heat of, 125 ; spectrum analysis of, 32 ; tests for stains, 452 ; in urine, 487. Blood corpuscles, 61 ; in cholera, 63 ; colour of, 61 ; chemical constitution of, 62 ; effects of disease in, 63 ; functions 6f, 65 ; Hewson on origin of, 210 ; origin and development of, 64 ; effects of re- agents on, 63 ; shape of, 61 ; size of, 62 ; structure of, 64. - Blood glailds, description of, 205 ; develop- ment of, 395 ; functions of, 208 ; general description of, 207. Blood tubes, 84 ; contractile movements of, 85 ; development of, 85 ; functions of, 86 ; structure of,' 84. Body, human, weight of. 111 ; Bcerhaave on the blood, 242 ; theory of error loci of, 64. Boiling, phenomenon of, 126. Bone, description of, 90 ; practical analysis of, 493 ; canaliculi of, 90 ; chemical composition of, 92 ; Haversiam canals of, 90 ; lacunae of, 90 ; structure of, 90 ; transformation of cartilage into, 93 ; re- generation of, 94. Bone tubes, 88. Bones of the ear, development of the, 388 ; middle ear, 348 ; Helmholtz' model for shewing action of, 573. Bonnet on development of aphides, 414. Bowman on action of ciliary muscle, 342 ; on cochlear muscle, 347 ; on decussation of optic nerves, 344 ; on fatty liver, 251 ; on the retina, 338 ; on sarcolemma of muscle, 73 ; on structure of kidney, 256. Boyle on Greatrakes' cures. 359. Borelli on blood corpuscles, 64; oa the microscope, 497. Bothriocephalus latus, development of, 409. Bottcher's test for sugar in urine, 481. Boscovitch on effect of eye-piece of Iluy- ghens in correcting chromatic aberra- tion, 502. Botiytis Bassianain silk worms, 439. Brachet on sympathetic, 325. Braid on monoideism, 857. - Braldwood on development of musculai; fibre, 53, 75. 584 INDEX. Brain. eflPects of asphyxia on, 234 ; develop- ment of, 390; dependence of mind on, 2S4 ; functions of, 294 ; preparation of protogon from, 495 ; pressure of blood vessels on, 220. Branchial clefts, development of^ 387. Breathing air, 229. Breeding, examples of selection in, 418. Brewster, Sir David, on colours produced by grooved structure, 141 ; on crystalline lens, 340 ; on contractions of the iris, 342 ; on mental spectra, 345. Bridgman's observations on the effect of a galvanic current on viscous solution of carbonate of lime, 43. • Bright's disease, blood in, 243, 245. Brodie,^ir B., on efiffecfcs of wounds on in- juring nerves, 323. Brogniart on heat in reitroduction of colocasia odora, 373. Bromine in tissues, 4. Bronchial sounds on auscultation, 227. Bronchophony, 228. Brown, Thomas, classification of mental faculties, 299. Brown and Broussais on the blood, 242. Brown Sequard on disease of cerebellum, 305 ; on the corpora quadrigemina, 307 ; on epilepsy vn guinea-pigs, 315, 420; oil the pupil, 341 ; on experiments on spinal cord, 286, 310 ; on effects of dis- eased spinal cord, 314 ; on special sensory 'nerves, 286 ; on supra-renal capsules, 323 ; on section of sympathetic, 325. Briicke on coagulation of the blood, 241 ; on coagulation of muscular substance, 83; definition of a cell, 60; observations on pigment cells of frogs, 39 ; on Peyer's glands, 206 ; on villi, 20S Brunner's glands, function of, 202. Brunonian movements, examples of, 38. Buchanan on coagulation of the blood, 241. Budge on spinal cord, 284. Buflf on vegetable electricity, 157. Buffon's theory of life, 184. Bulbus arteriosus, development of, 389. Bull's-eye condensers of microscope, 5u9. Bulimia, cases of, 191. Bunsen's battery, 153. Burdach's primordial mucous layer, 46, 104. Burke, skull of, 302. Burdon Sanderson on effects of respiration on rapidity of circulation^ 219 ; on con- tagia, 104. Burrows' on cranial circulation, 223. Busk on the uredo segetum, 438 ; Butyric acid, chemistry of, 22; in 'urine, ' 485. Burette for volumetric analysis, 465. Cadaveric rigidity, 83. Cagniard de la Tour's syren, 130. Calabar bean, effects of, on pupil, 341. Calcium in tissues, 5 ; carbonate in tissues, 28 ; fluoride in tissues, 28 ; oxalate in tissues, 28 ; oxalate as a sediment In urine, 486 ; phosphate in tissues, 29 ; phosphate as a deposit in mine, 487 ; sulphates in tissues, 29. Calculi, blood in persons having, 245. Calendula oflcinalis, phosphoresence in, 144. Campbell on excito-secretory function of sympathetic, 323. Camper and Lavater on physiognomy, 303. Canada 'balsam, use of, in histology, 524. Cancer, nature of, 278 : blood in, 245 ; cells, 71. Cane-sugar, 26. Canoies, smell of flowers near, 331. Cantharides, effect of, on the bladder, 369. Canton on compressibility of fluids, 114. Capillaries,functiOns of, 217; arrangements 'of, in various tissues and organs, 218 ; circulation, 217. Capillarity, 116. Capillary tubes, Foisseuille's researches on, 119. Caproic acid, 22. Carbon, amount of, exhaled from lungs, 248 ; monoxide, effect of, on spectrum of blood, 451 ; amount of excreted; in respiration, 230 ; in tissues, 3. Carbonate of ammonium, in tissues, 28 ; of calcium in tissues, 28 ; of magnesium in tissues, 28 ; of potassium in tissues, 28 ; of sodium, 28 ; in tissue, 28. Carbonic acid, in crowded rooms, 235 ; in respiration, 227; experiments on amount of, in respiration, 560, CaT-cinoma, 279, Cardiac dropsy, blood in, 245. Cardiograph of Marey, description of, 554. Carmine, use of, in histology, 521; injection of Beale, 523 ; injection of Carter, 623. Carnot on heat, 124. Carpenter and Bunn on corpus dentatum of cerebellum, 305. Carter's carmine fluid for injecting, 523. Cartilage, Meckel's, 388. Cartilage, analysis of, 493 ; articular. 88 ; cells, 68 ; chemical composition of, 90 ; costal, 89 ; diseased. 89 ; fibro- , 89 ; foetal, 89 ; permanent, 88 ; structure of, 88 ; temporary, 88. Casein, chemistry of, 9. Catalepsy, 363. Cathelectrotonus, 171. Oathelectrode, definition of, 151. Cells, epithelial, 68 ; cancer, 71 ; carti- lage, 68 : embryonic, 68 ; ftit cells,, 66 ; fibre, 68 ; functions of, 56 ; gland cells, 67 ; granule, 70 ; nerve, 65 ; morbid, 69j ori- gin of, 52 ; physical and chemicalpro- perties of, 50 ; pus, 69 ; reproduction of, 56 ; secretions of, 51 ; size of, 51 ; tran- sition, 67 ; varieties of, 51. Cell, contents, definition of, 50 ; develop- ment theories of Beale, 55 ; Bennet, '54 ; Goodsir, 52 ; Huxley, 53 ; Schleiden' and Schwann, 52 ; Virchow, 70 ; elements of the tissues, 50 ; fibres, 76 ; movements, 57 ; sap, definition of, 50 ; wall, definition cif, 60. Centre of gravity, 106. INDEX. 585 Cerebellum, development of, 391 ; experi- ments on, 304 ; function of, 314 ; Histo- logy of, 303 ; Pathology of, 305 ; structure of granular layer, 303. derebral disorders, 362. Z!erebric acid, preparation of, 494, Jerebro-spinal disorders, 363. Derebro-spinal nerves, 316, Uerebrum, 282 ; development of, 390 ; effects of removing, 295 ; experiments on, 294 ; Histology of, 294 i pathological effects on, 294, 297. Ceruminous glands, 266. ::;erutti on smell, '330. Dhalaziferous membrane in egg, 399. Ohara, movements in cells of, 38. Chauveau on contagia, 104 ; on rapidity of circulation, 219. dheeks and lips, structure of, 193. Chemical, alterations of the blood in dis- ease, 243 ; action of light, 143 ; elements, 3 ; Physiology, 444 ; reagents in Histo- logy, 518. Chemistry of the tissues, 2. Chevallier and Henry on analysis of milk, 405. Dhevalier on the microscope, 498. Ohloral, an 'antagonist to strychnine and Calabar bean, 315. Chloride of ammonium in tissues, 28. Chlorides in tissues, 28 ; in urine, estima- tion of, 467 ; of potassium, excretioa of, by kidneys, 261 ; of potassium in tissues, 28 ; of sodium, excretion of, by kidneys, 261 ; of sodium in tissues, 28 ', in urine, as affected by disease, 467. Chlorine in tissues, 4. Chloroform, effects of, on brain, 368. Cholsemia, blood in, 245. Cholestrin, chemistry of, 10 ; in bile, 250 ; mode of preparing, 446. Cholophsein, chemistry of, 33. Uhondrin, chemistry of, 11 ; preparation of, 493. Chorda dorsalis, structure of, 384. Chorda tympani, a nerve of the tongue, 193; to salivary glands, 196. Chorea, 363. Chorion, development of the, 386. Choroid, 340. Chossat on starvation affecting tempera- ture, 247. Christison's method of ascertaining amount of solid matter from specific gravity of urine, 463. Chromatic aberration, nature of, 140 ; how corrected in microscope, 501. Chromatic scale, 132. }hromic acid, use of, in Histology, 520. 3hrzonszczewsky on the sti-ucture of the liver, 249. 3hyle, analysis of, 453 ; corpuscles, 60. Chylous urine, 484. ;hylificatlon and sanguification, 205. !;hyme, description of, 201. ^icatricula in egg, 399. ;ilia, description of, 77 J in Fallopian tubes, 376. I Circulation, arterial, 215 ; of the blood, 212 ; capillary, 217 ; in the cranium, 220; history of controversy regarding, 223 ; in the lungs, 224 ; in erectile tissues, 224 ; in the foetus, description of, 224 ; changes in tjie, at birth, 225 ; experi- ments on, 551; forces producing, 212; in the liver, 249 ; Marey on the forces of, 216 ; experiments to measure the rapid- ity of, 557; organs of, development of, 389 ; in portal system, 223 ; venous, 218. Circumvallate papillse of the tongue, 833. Clarke, J, Lockhart, on decussation of posterior columns of cord, 31i ; on de- velopment of muscle, 53, 75 ; method of examining cerebellum, 303 ; on spinal cord, 283 ; on structure of spinal cord, 309 ; on structure of organ of smell, 329 ; on transverse section of nei've-tubes, 95. Classification of the diseases of innervation, 362. Cleavage of the yolk, 383. Clefts, branchial, 387. Cleland and Banks on the development of testes, 398. Climate affecting the liver, 252. Clinical examination of urine, 488. Clitoris, development of, 398, Cloaca, 397. Coagulation of the blood, 241 ; different theories of, 241. Coagula, softening of, 243 ; coagulum, esti- mation of, in blood, 449. Coathupe on amount of air in respiration, 228. Cohn on disease in house files, 439. Cobbold on development of tapeworm, 409, Cochineal insect, 30. Cochlea, development of, 393 ; structure of 346. Coelenterata, reproduction in, 373. Cohesion, 109. Cohnheim on pus formation, 70 ; on passage of white blood corpuscles, 210. Gold, effect of, on tissues, 619 ; on spinal functions, 369. Oolding on heat, 124. Colic, 364. CoUadon and Sturm on compressibility of fiuids, 114 ; on velocity of sound, 13u. Collard on mental faculties, 299. Colloids, 118. Colloid cancer, 279; disease of thyroid gland, 207. CoUongues and Haughton on muscular sounds, 131. Colostrum, description of, 403, 404, Colour blindness, 343. Colour of fibre on grooved surfaces, 140 ; of races of men, 30 ; of the urine, 459 ; . of thin plates, 140. Colouring matter in blood, description of, 31 ; estimation 0^ 449 ; of the urine, 34. Colourless corpuscles of the blood, passage of, according to Cohnheim, 210. Colours, simple or compound, 141. Columba livia, the progenitor of all tame pigeons, 418. 586 INDEX. Conia, 442. Ooinbe on phrenology, 300. Combination tones, description of, 676. Gommutatoi: of Fohl, description of, 528. Compass of the human voice, 133. Complemental air, 229 ; nutrition of Paget, 237. Compressibility, 108. Concretions, .biliary, intestinal, mineral, and urinaryj'280. Condenser of Gillett, 509. Conductivity of heat, 127. Conductors and non-conductors of electri- • city, 147. Congestion, 277 ; of brain, 365. Conium, physiological action of, 369. O&ni vasGulosi of testes, 379 ; development ■ of, 398. Connective tissue theory, 79. Consciousness, definition of, 299 ; double, phenomena of, 357. Conservation of force, 182. Constipation, 274. Contractile cell fibres, 77 ; fibres of tissue, 80. ' Contractility, experiments on, 530 ; a vital property, 177 ; stimuli of, 289. Contractile movements of blood vessels, 85. Convolutions of brain, development of,39X. Convulsionaires of St Medard, 358. ~ Convulsions, 363. copper in tissues, 6. Cophosis, 364. Coral reefs, development of, 410* Correlation of force, 181. Gorium, structure of, 264. Gornai-o, case of, 192. Cornea, formula for calculating radius of curvature of, 565 ; mode of measuring, 563 ; refiections on the, 135 ; structure of, 339. Corpora amylacese, 25. Corpus callosum, 282 ; development of, 391 ; fimbriatum, development of, 391 j High- moriaflum,-379. Corpora lutea, chEEracters of true and false. 376 ; structure 'of, 376 ; Malpighiana of kidney, 256 ; cLuadrigemenia, rotatory movements following injury of, 307 ; de- velopment of, 391. Corpora striata, 300. ^■ Corpuscles, blood, 61 ; chyle, 60 ; lymph, 60. Corti, membrane of, 346 ; organs of, func- tion of, 578. Costal cartilage, structure of, 89. . Coup de soleil, 442. Gourvoisier on nerve cell, 65. Cousin on mental faculties, 299. Corrans, Dr, on blood corpuscle in case of ' cholera, 63. Graigintinny meadows, smell of, 331. Cramer on images on the eye, 135, 342 ; on accommodation of the eye to distance, 571. Crampton on action of ciliary muscle, 342. Cranial circulation, 220 \ as affecting the b^ain, 289. Cranium, circulation i& the, 220 ; dei ment of, 387. Cream, nature of, 404. Creatin, chemistry of, 18 ; preparatii from urine^ 476. Creatinin, chemistry of, 18 ; preparati from urine, 476. Creosote, use of, in Histology, 525. Orefcification of tubercle, 278. Cruorin of Stokes, 32. Crura cerebri, development of, 391. Crusta petrosa, structure of, 87. Crustacea, spermatozoids in, 38. Cruveilhier on artificial embolism, 2^ Cryptogamia, reproduction of, 99. Crystallin, chemistry of, 10. Crystalline lens, structure of, 340. Crystalloids, 118. Cutis, structure of, 264. Cylinder, mode of calculating time revolving, 545. Cyon and Ludwig 'on the depressor i of the heart, 321. Cystica, 281. Cysticercus fasciolaris, developm^n 406. Cystic oxide, chemistry of, 16. Cystin, chemistry of, 16 \ in urine, 48 Oystoidea, 281. Cystoma, 279. Czermak on deglutition, 196 ; on lari scope, 579 ; sphygmoscope of, descri" of, 555 ; on touch, 336. Dalton's experiments on cerebrum, 2J Daltonism, 343. Damaluric acifl in urine, 477. Dammar fluid, use of, in Histology, 5! Daniels' battery, 152. Danilewsky on ferments in panci juice, 455. Danson on the weight and size of the hi body. 111. Darwin on the human voice, 419 ; o law of battle among animals, 41!i natural selection,. 415 ; on the stn for existence, 418. Davy, Sir Humphrey, on the electric '. 155 ; on he&t, 124 ; on temperatu arterial blood, 232. Death by asphyxia, 442 ; by coma, 441 drowning, 233 ; nature of, 441 ; by .cope, 421 ; varieties of, 441. De Blainville on blood corpuscle, 64. Decidu^, formation of, 400. Decidua reflexa, formation of, 400. Decidua vera, formation of, 400. Deen Van, experiments on spinal 310. Defffication, phenomena of, 274. Deglutition, mechanism of, 196. Degenerations of textures, 280. De Qraaf on vesicles in ovary, 375. ^ Delafond on villi, 205. De la Torre on blood corpuscles, 64. Dementia, 362. Density, 110. INDEX. S87 Cental tubes, 86 ; structure of, 86. Dentition, nerves in, S24. Deposits in urine, 4S6, 487. Dermis, structure of, 264. Descartes on reflex action, 311. Descimet's membrane 339. Development, of the alimentary canal, 393; of the aphides, 414; of bees, 412 ; of the blood glands, 395 ; of the chorion, 386 ; conclusions as to, 402; of the body on effect of, on amount of carbonic acid, 231; of the organs of circulation, 389 ; of the cranium, 367 ; of coral reefs, 410 ; of the ear, 892 ; of the embryo, 3S3 ; of egg in birds, 309 ; of the eye, 392 ; of the face, S88 ; human ovum, 398 ; of infusoria, 428 : of the kidneys, 396 ; of the limbs, 388 ; of the liver, 394 ; of molecules, 36 ; of the nervous system, 390 ; of the nose, 393 ; of the ovum, 398 ; of the pancreas, 305 ; progressive, discussion of theory of, 402 ; of salivary glands, 395 ; of the skull, 387 ; of special organs in the embryo> 386 ; of striated muscle, 75 ; of the supra- renal capsules, 391 ; of the organs of respiration, 395 ; of the ureters, 396 ; of the urinary bladder, 396 ; of the urinary and generative organs, 396 ; of the organ of voice, 395 ; of Wolfaan bodies, 396. Diabetic sugar, 26 ; preparation from urine, 479 ; tests for, in urine, 480. Diabetes, blood in, 245. , Diathermancy, 128. Diastaltic actions, 364. Diastolic sound of the heart, 213. Diamagnetism, 146. Diaphanous bodies in morbid products, 44. Diarrhcea, 274. Diatonic scale, 132 ; di-cbloride of tin test for sugar in urine, 481. Difference tone apparatus of Appunn, 577 ; description of, 576. Differentiation in growth, 176. Difi^raction of light, 137. Diffusion of gases, 122. Digestion, conditions favourable for, 199 ; in the intestines, 201 j rapidity of, 200 ; of various kinds of food, 200 ; influence of nervous system on, 198 ; secondary, 239 ; in the stomach, 197- Disease, of cerebrum, 297; effects cf, on che- mical constitution of blood, 243 ; effect of, on amount of carbonic acid, 231 ; effect cf, on the pulse, 216 ; affecting sweaty 265 ; effects of, on urine, 260. Diseases of the blood, 245 ; of nutrition, 277 ;. of reproduction, 440. Discharge of fluid through tubes, 119. Dispersion of light, 138. Divisibility, 107. Dobie, Dr, on structure of muscle, 74. Doff, development of ovum in, 383 ; varie- ties of, 418. Dolland on the microscope, 498. Donders on movements of the brain, 222 ; method of using Helmholtz's ophthal- mometer, 570 ; on hypermetropia, 343. Donne, on blood corpuscle, 64 ; on putre- faction, 437. Double consciousness, phenomena of, 357. Dowler Bennet, Dr, on tempei-ature in yellow fever, 248. Doyferes injection of chromate of lead, 523. Dreams, phenomena of, 355. Drowning, death by, 233. Dropsy, 277. Du fiois-Reymond on cutaneous current, 169 ; demonstration of animal electricity, 166 ; on electrical fishes, 161 ; on elec- trotonus, 172 ; on effects of electricity on nerves, 97; on evolution of electricity by nerves, 97; experiment to shew current in living body, 536; galvanometer of, 149 ; induction apparatus of, 526 ; key of, 528; modification of Bernard's ex- periment on contractility, 531 ; myogra- phion of, 545 ; on nerve-current, 169 ; non-polarizable electrodes of, 534; on par-electronomy, |167 ; polarizable elec- trodes of, 530 ; rheocord of, 542 ; theory of muscular current of, 167. Duct, common ejaculatory, 380 ; develop- ment of, 397. Ductus arteriosus, 389 ; venosus, develop - ment of, 394. Duge's definition of life, 184. Dujardin's sarcode, 104 ; on development of tapeworm, 406. ' Dumas' theory of compound radicles, 6 ; theory of chemical balance of organic nature, 7. Dupuy on sympathetic, 325. Dust, nature of, 428 ; examination of, from different localities, 429. Dynamical theory of electricity, 147 : of heat, 124. Dysentery, 274. Dyspnoea, 233. Dzierzon on development of bees, 412. £. Ear, analogy to eye, 349 ; bones of, 348 ; cochlea of, 346 ; development of, 372 ; Eustachian tube in, 349 ; external ear, 348 ; histology of, 345 ; labyrinth of, 347 ; middle ear, 348 ; model of Uelmholtz for explaining the mechanism of bones of, 673 ; muscles of, 349 ; organ of Corti in, 346 ; semicircular canals, 347 ; suscep- tibility of, to vibrations, 130 ; tympanum, 348 ; vestibule of, 346. Ebullition, 126. Ecker on the cochlea, 346 ; on structure of organ of smell, 329; on structure of kidney, 256. Eckhard on development of muscle, 75 ; on electrotonus, 172. Echoes, 130. Eclampsia/ 363. Ecstacy, 357. Edinburgh Committee on eflfecfc 0^ drugs on secretion of bile, 253. Edwards and Balzac's experiments on food, 189. Effluvia, nature of, 328. S88 INDEX. Egga, bacteria and Tibi'ios in, 440 ; devs- lopment of, iu birds, 399 ; putrefaction of, 437 ; shell of, 399 ; white of, 399. Ehrenberg on ciliai'y movements, 78. Einbrodt on effect of respiration on rapid- ity of circulation, 219. Elasticity, 108. Klastin, chemistry of, 11 ; preparation of, 492. Electricity, properties relating to, 146 ; animal, 157 ; current of, in living body, 168 ; in the animal tissues, history of, 161 ; effect of, on living tissues, 519; produced by chemical action, 150; Dufay and Symmer'B theory of, 147 ; dyoamical theory of, 147 ; Franklin's theory of, 147 ; frictional, 150 ; produced by heat, 150 ; of muscle, experiments on, 533 ; effects of, on muscles, 82 ; produced by living organised structures, 157; effects of, on nerve, 97 ; evolution of, by nerves, 97 ; by induction, 155 ; by miKcle, 82 ; vege- table, 157. Electrode, definition of, 151. Electrolysis, 155. Electro-magnetism, 148. Electro-magnet, rotation of, 145, Electroscope, 148. Elecbrotonus, 169. Elements, chemical, 3. Ellis on the microscope, 498. Embryo, development of the, 383 ; develop- ment of special organs in, 386. Embryonal areas of Bastian, 424. Emission theory of 'heat, 123 ; theory of light, 134. Emphysema, cause of, 109. Emprosthotonos, 3(13. Empusa in house flies, 439. Enamel, structure of, 87. Encephaloma, 279. Enchondroma, 279. Enderlin on ashes of fseces, 272. Endolymph in the ear, 280, 346. Endoplast of Huxley, 33. Endosmose, 116. Energy, definition of, 183. Enlargement, theory of, 499. Entozoa, 281. Entozoon foliculorum, 281. Epidemics as connected wlch smell, 330. Epidermis, structure of, 263 ; modification of appendages of, 269. Epididymis, development of, 398 ; structure of, 379. % Epigenesis of Robin, 77. Epithelium, artificial, 44 ; cells of, 68. Epithelioma, 279. Epilepsy, 363. Epiphyta, 281. Epizoa, 281. Equilibrium, condition of, 106. Erectile tissues, circulation in, 224. Erysipelas, blood in, 245. Esquimaux, food consumed by the, 192. Eschricht on Bothriocephalus latus, 409, Esodic nerves, 289. Ether, effects of, on brain, 368. , Euler on the mitii-oscope, 498. Europeans in tropical countries, healtl 252. Eustachian tube, development of, 393. Exanthemata, 245. Exosmose, 117. Excito-secretory actions, examples of, I Excretin of Marcet as an excretion, £ chemistry of, 489. Excretion by various organs, 248 ; fron testinefl, 270 ; from the kidney, 256 ; f the liver, 249 ; fi'om the lungs, 248 ; i the skin, 263 ; general results of pro of, 274. Excretolic acid of Marcet, 489. Exercise, effect of, on secretion of bilo, on the pulse, 216 ; on urine, 259. Exodic nerves, 289. > Experimental physiology, 525. Expiration, effect of, on venous circulat 219. Extractives, estimation of, in blood, 44 Exudation, 278. Eye, accommodation of, to distance, \ anatomy of, 337 ; in albino, 341 ; aqu< humour of, 339 ; choroid in, 340 ; col blindness, 343; cornea in, 339; ciystal lens vin, 340 ; development of, % entrance of optic nerve insensible, i explanation of one object seen f two images, 343 ; external protec parts of, 337 ; impressions remain f certain time, 344 ; iris, 341 ; diffe lenses of, 339, 340 ; muscles of, \ ocular spectra, 344 ; optical apparatu 339 ; position of objects as seen by, * retina in, 338 ; theory of single vifi 343 ; vitreous humour in, 340 ; spore aqueous humour of, 440: Eye-ball, movements of, 338 ; expevin to shew action of the muscles of, J nerves of, 338, Eye-brows, 337. Eye-glass of microscope, 502. Eye-piece of Huyghens, 502 ; of microBC description of, 508. E. Face, development of the, 388. Facial nerve, 318 ; paralysis of, 318. Faculties, mental classification of, 298. Fseces, analysis of, 489 ; amount of, creted daily, 202, 270 ; biliary acids 273 ; chemical composition of, 271 ; oration of, by bile, 272; histoloj structure of, 271 ; odour of, 273. Falling apparatus of Pfluger, descrip of, 539. Fallopian tubes, action of, 376 ; deve ment of, 397 ; cilia of, 376. Falsetto voice, 352. Faradic electricity, 155 ; physiologica feet of, 637. Farady on electro-magnetic rotatibn, : on magnetic electricity, 156; on i netism and diamagnetism, 146. Fasciculus of muscle, 73. Fatigue, muscular, 83. INDEX. 589 fats, 18 ; chemical nature of, 19. Tat and Cholestrin, estimation of, in bile, 455. I'at, cells of, 66 ;; estimation of, in blood, 448; Boussingault's experiments on, 24 ; Dumas', 24 ; Liebig's origin of, 24 ; in the liver, 251, in the nervous system, esti- mation of, 494, in the urine, 484. faults of simple lenses, 500. ''avus, vegetable nature of, 438. B'ecundation, in animals, 378 ; in bees, 412 ; of germs, 378 ; mode of, 381 ; changes in ovum following, 382; in plants, 378; changes in uterus following, 400. Fehling's test for sugar in urine, 480 ; solution for volumetric process for sugar in urine, 482. ^ F'emale organs of generation, development of, 39T. Fenestra ovalis, 348 ; rotunda, 348. P'er mentation, test for sugar in urine, 481; of urine, 4.')9. Ferrocyanide of potassium in volumetric process for phosphoric acid, 469. Fever, 277 ; fibrin in blood of, 245 ; effect on sympathetic in, 326. Fibre-cells, 68. Fibre, definition of a, 72. Fibres, and grooved surfaces, colour of, 140 ; cell, 76; contractile, 73; histolytic, 78; molecular, 73; nuclear, 76; non-voluntary contractile, 77. Fibrin, chemistry of, 9 ; estimation of, in blood, 448. FibrillEB of muscle, 73. Pibro-cartillage, structure of, 89. Fibroma, 279. Fibrous elements of the tissues, 72. - Fick on electrotonus, 172 ; and Wislicenus on food, 190 ; and Wislicenus on effects of exercise on excretion of urea, 259. Ficus carica, bacteria in, 439. Field glass of microscope, 502. Fish, artificial rearing of, 381. Fishes, electrical, 157 ; fecundation in, 381 ; spermatozoids in, 380. Flasks for volumetric analysis, 465. Flint on ffeces, 272. Florida, development of coral reefs on coast of, 411. Flouren's experiments on brain, 285 ; ex- periments on cerebellum, 304; experi- ments on cerebrum, 294; on corpora quadrigemina, 307. Fluid, general qualitative examination of an animal, 445 ; qualitative and quanti- tative analysis of, 447. Fluids In motion, laws of, 119. Fluorescence, 189. Fluorine in tissues, 4; Foetal circulation, description of, 224; changes in the, at birth, 225. Foetus, development of human, 398. Fontana on the microscope, 497. food, nature of, 188 ; as influenced by ex- ercise, 190 ; eflfect of on secretion of bile, 264; experiments on nature of, 389; effects of, on mineral ingiedienlis, 29 ; as Influenced by oxygen in the air, 190 ; quantity of, 190 ; efi'ect of, on respiration, 230 ; influence of, on temperature of body, 247 ; effects of, on urine, 268 ; variety in, 189. Foramen of Munro, development of, 391. Force or energy, 183 ; correlation of, 181 ; conservation, 18:i ; of left ventricle, 215. Forces producing the circulation, 212. Formula for radius of convex mirrors, 565 ; dental of man, 192 ; for ophthalmometer ofHelmhoItz,567. Fornix, development of, 391. Fox, Dr WHsoh, on development of muscle, 76. Franklin on food, 190 ; theory of electricity, 147. Frauenhofer on the -microscope, 498 ; on solar spectrum, 138. Freei-'s Dr J. W., observation on coloured blood corpuscle, 61 ; on analysis of chyle, 463. Freezing, mixtures, composition of, 519. Frerichs on gastric follicles during diges- tion, 199. Frey on structure of kidney, 256. Friction, 110 Frogs, lungs of, 226 ; mode of preparing for physiological experiment, 631. Frommherzand Gugert on ash of cartilage, 90. Fungi, development of, in closed cavities of body, 440. Funke on reaction of nerve tube, 96 ; on amount of sweat, 265 ; on urea in sweat, 265 ; on villi, 206. Fusion, 125. Gall on the cerebellum, 306 ; and Spurz- heim on phrenology, 300. Gall-bladder, action of the, 250 ; structure of the, 250. Galactophorous ducts, 403. Galvani, Madame, on frogs, 162. Galvanic current, physiological action of, 154: thermal and luminous effects of, 154. Galvanometer, the multiplying, 149; de- scription of, 533. Galvano-puncture, 156. Gamgee on secretion of bile, 255. Ganglionic system of neiTcs, 322 ; excito- secretory and excito-nutrlent, properties of, 323 ; senso-motory, properties of, 322. Garcia on laryngoscope, 579. Garrod*s test for uric acid, 475. Gases, absorption of, 122 ; diffusion of, 122 ; transpiration of, 123-; of the blood, 232 ; mode of analgia of, in blood, 452 ; of intestine, 272; in tissues, 27 ; of the urine, 488- Gaspard on embolism, 244. Gaserian ganglion, nerve-cells in, 65. Gastiic juice, acid of, 464; analysis of, 454 ; ash of, 454 ; description of, 202 ; quantity of, 204. 59° INDEX. Gastric mucous membrane, structure of, 199. Geese of Strasburg, pat6 du-foie-gras, 251. Gelatin, chemistry of, 10. Gemmarium of a queen-bee, 414. Gemmation, reproduction by, 373. Gelatin, composition of, 10 ; preparation of, 492 ; properties of, 11, Generalisation, faculty, of, 299. GeneratioUj spontaneous, discussion of, 421. Generative organs, development of, 397. Genital cord, 397. Gerlach on the granular layer of the cere- bellum, 303. Germ cells, phenomena attending separa- tion of, 373. Germinal, area, 384; membrane, division of, into layers, 384 ; spot, 382 ; vesicle, 382. Germs in the air, experiments on destruc- tion of, 432. Gibbon, voice of the, 419. Gilbert and Lawes, experiments on origin of fat, 24. Gillett's condenser, 509. Girafife, nuclear fibres in, 76. Glanders, blood in, 245. Glands, blood, description of, 205 ; cells of, 67 ; of oesophagus, 196 ; lymphatic, description of, 206; of Peyer, descrip- tion of, 206 ; sebaceous, 266 ; of the skin, 2(54. Gland thymus, description and function of, 207 ; thyroid, description and func- tion of, 207. Glandulse odoriferse, 266. Glacuoma, formation of, 47. Globulin, chemistry of, 10. Globus major, structure of, 379. ' Globus minor, structure of, 379, Glossopharyngeal nerve, 320 ; nerve of the tongue^ 193. Glucose, 26. Glycerin, chemisti-y of, 2a ; use of, in His- tology, 520. Glycocholic acid as an excretion, 250; chemistry of, 12, 456. Glycocin, chemistry of, 17. Glycocol, chemistry of, 17. Glycogen, chemistry of, 25 ; preparation of, 495. Glycogenic function of liver, 251 ; also an exclto-secretory functioli, 324. Glycohsemia, blood in, 245. •: Gold cliloride, use of, in Histology, 521. Goodsir on the amphioxus lanceolatus, 390 ; theory of cell formation, 52 ; centres of germination, 52; centres of nutrition, 52 ; on the placenta, 401 ; on develop- ment of supra-renal capsules, 396. Gout, blood in, 245. Graafian vesicles, structure of, 375 Graefe, case of removal of iris, 342, Graham, observations on crystalloids and colloids, 44 ; researches on dialysis, 118 ; researches on endosmose and exosmose, 117 ; on diffusion of gases in respiration, 227 ; on difTusion of gases, 123 ; t piration of gases, 123 ; on odorous stances, 328. Granule, definition of, 35. , Grainger on spinal cord, 284. Grape sugar, 26. Grassi on odours in Neckar hospital, £ Gratio Kelleia, case of, 416. Graves, Dr, on touch, 335. ~ Gravity, 106. Gray matter of the spinal cord, 285. Greeks and Bomans, principle of m scope known to, 496. Grotto del Oano, gas in, 832. Growths "raorbid, blood in, 245. Growth in secretion, 236, Grove on co-relation offeree, 181. Grove's battery, 153. Gruby's pocket microscope, 50. Gruby on villi, 205. Guaiacum, test for blood, 452. Gu^rin-Meneville on disease in silk wo 439. Guinea pigs, epilepsy in, 420, Gulliver on blood corpuscle, 64 ; meas ment of blood corpuscle, 62; on fluid in blood glands, 208 ; on fatt^ generation of arteries, 244 ; on softe; of clots, 243. Gum Dammar, use of, in Histology, 52 Gustatory, nerve of the tongue, 193. Gymnarchus electricus, 158, 160. Gyrotrope of Fohl, description of, 528. H ilabenula sulcata in cochlea, 346. Hseekel's primordial protogenes, 104. Hsemadromobieter, Volkmanu's, 219 ; scription of, 557. Hsemadynamometer of Foisseuille, scription of, 558. ' H£ematachometer,Tierordt's, 219 ; des( tion of, 557. Hsematitis of Piorry, 208. H£emato-cryBtallin, 31; chemistry of, estimation of, in blood, 449. Haamin crystals, formation of, 451. Haemoglobin, chemistry of, 31 ; estima of, in blood, 449; optical piopertiei 450. Haemorrhage, 277. Haggart, skull of, 302. Hair, chemical composition of, 26p ; cc of, 268 ; hygrometiic property of. number of, 268 ; root of, 268 ; strnc of, 267 ; varieties of, in animals, 261 Hales on rapidity of circulation, 219 static force of heart, 216. Haller, theory of contractility of, : on organised co^icrete, 104; on ri actions, 311. Hallucinations, 358. Hamilton, Sir Wm., classification of e tal faculties, 299. Hammond's experiments on food, 189. Hanging, effect of, on cranial circula 221. Hannover on vitreous humour, 340. INDEX. S9I Hapto^en membrane of Ascherson, 36. Harles's, experiment on muscular con- tractility, 178 ; observations on pigmei.t cellsoffroe:6,39. Harley on colouring matter of the urine, 34 ; on amount of saliya, 195 ; on the supra-renal capsules, 323. Hartnach and Nachet's microscope^ 499. Harvey on heterogenesis, 42X ; on the egg, 102 ; on reproduction, 382. Hammer of Heidenhain, description of, 637- Harmonics, laws of, 132; as illustrated by Appunn'a apparatus, 574. Haughton on effects of exercise on excre- tion of urea, 260. Headaclie, 362. Hearing, ca^uses of, 345 ; experiments on, 573 ; histology of organ of, 345. Heart, development of, 389 ; nerves of the, 321; order of succession in the action of the, 214 ; preparation of inosite from muscular substance of, 491 ; sounds, de- scription of, 212; time occupied by sounds of, 213 ; causes of the sounds of, 213. Heat, properties relating to, 123 ; animal, 245 ; circumstances affecting animal, 246; relation of chemical affinity to, 127; conductivity of, 127; effects of, 124; latent, 126; relation of Jight to, 143 ; mechanical equivalent of, 124 ; radiant, 128 ; in reproductive processes, 373 ; sources of, 124. Hegar on excretion of chlorides by kid- neys, 261. Hegel on mental faculties, 299. Heidenhain's tetanometer, description of, 537 ; on the terminations of nerves in the salivary glands, 196; on structure of villi, 205. Heller on colouring matter of the urine, S4. Itelmarecbt on spores in aqueous humour of eye, 440. Helmholtz on accommodation of the eye to distance, 342; on animal heat, 247; on colours, 141 ; on harmonics, 132 ; modification of induction coil, 527 ; nio- nochord, description of, 573; on muscle, ■• 75 ; myographion, description of, 545 ; on rapidity of nerve current, 287 ; oph- thalmometer, 842; ophthalmometer, opti- cal principles of, 565 ; description of, 568; measurements made by means of 570 ; mode of using, 568 ; ophthalmo- scope, description of, 571 ; phakoscope- description of, 571 ; model of tympanum, description of, 573. Helmont, Van, on (be blood, 242. Hemispherical ganglion of Solly, 283. Hemplegia, 363 Henle on structure of blood tubes, 84 ; on connective tissue, 80 ; on the cutis, 264 ; on number of hairs, 268; on nuclearfibre, 76; on development of white fibrous tisane, 77; on tendon, 80. Hensen on blood corpuscle, 64. Hepatic vein, development of, 394. Hermaphrodite, definition of, 381. Hertwig's experiments on brain, 285, 294. Heterogensis, description of, 421 ; history of, 421. Hewson on nature of blood corpuscle, 64 ; on origin of blood corpuscle, 210. Hinny, ^5. , Hippocampus major, development of, 391. Hippocrates on white blood, 209 ; on col- oured bloods, 242. Hippuric acid, test for, in urine, 476 ; che- mistry of, 15. Hirsch on rapidity of circulation, 288. His on structure of lymphatic glands, 206. Histogenetic molecules, definition pf, 36. Histological physiolo^, 496 ; mode of teaching, 516 ; physical reagents, 618 ; chemical reagents, 518; softening, rea- gents, 520 ; hardening reagents, 620. Histology^ general, 35 ; of various organs ([see wnaer names of organs). Histolytic fibres, structure of, 78 ; mole- cules definition of, 36, 37- History of electricity in the animal tissues, I 162 ; of heterogenesis, 421 ; of the micro- scope, 496. Hodgkin on blood corpuscle, 64. Holothuria, formation of mineral matter in, 102. Home on the accommodation of eye to distance, 342. Hoppe-Seyler on chemical constitution of blood corpuscles, 62 ; on colouring mat- ter of the blood, 32 ; on optical proper- ties of bile acids and pigments, 457 ; on spectrum of blood containing carbon monoxide, 451. Horse, portal circulation in the, 224. House flies, disease in, 439. Human body, weight of. 111 ; ovum, de- velopment of, 398 ; voice^ compass of, Humboldt on animal electricity, 164 ; on gymnotus, 160. Hunger and tbii-st, 191. Hunter, John, on elasticity of larger vessels, 85 ; materia vitse diffusa, 183 ; on the origin of the dog, wolf, and jackal, 418. Hutchinson on amount of air in respira- tion, 228 ; spirometer of, 229, 561. Huxley on the Ancon sheep, 416 ; on the case of Gratio Kelleia, 416; theory of cell formations, 53. Huyghen's eye-piece, 502. Hybrids, 41,5. Hydrochloric acid as a constituent of the body, 28 ; use of, in histology, 520. HydrocyaniQ. acid, physiological action of, 369. Hydrogen in tissues, 3, 27 ; light carbu- retted, 27 ; sulphuretted, 485. Hydrophobia, 363. Hydrostatic equilibrium, 115. Hydrostatic and hydrodyinamic properties, 114. Hypermetropia, 343. 592 INDEX, Hypertrophy, 279 ; definition of, 238. Hypochondriasis, 362. Hypoglossal nerve, 322. Hypospadias, condition of, 398. Hypoxanthin, chemistry of, X6. Hyrtl on injecting tissues, 622. Hysteria, 363 ; secretion of urine in, 325. Icthyosis, case of, in porcupine man, 417. Idea of the beautiful among savage tribes, origin of, 420. Ileus, 274. Iliac passion, 274. Imagination, faculty of, 290. Imbibition, ne. Immersion lenses, use of, 508. Incubus of nightmare, 355. IncuS:, the, 348. Indian bat, hair of, 267- Indican, chemistry of,.34. Induced electricity, 155, 157 ; mode of de- monstrating the physiological effect of, on muscle, 537. Induction, electrical, 148 ; apparatus of Du Bois-Kejonond, description of, 526. Induration, 279. Inflammation, 277 ; fibrin in blood of, 245. Infusoria, development of, 46, 423. Injection of tissue, 521 ; opaque injec- tions, 522 ; transparent, 523. Innervation, 282; abnormal, 361. Inorganic.constituents of urine, estimation - of, 467. Inosinic acid, 'chemistry of, 15. Inosite, chemistry of, 27 ; preparation of, from'muscular substance of heart, 491 ; Scherer's test for, 492. Insalivation, function of. 194. Inspiration, efEect of, on venous circula- tion, 219. Intellect, faculties of, 299. Intellectual faculties, conditions for, 284. Intensity of musical note, cause of, 131. Intercellular substance, 51. Interference of rays of light, 137. Intermaxillary process, 388. Interrupted current, definition of, 157 ; mode of shewing physiological efEect of, on muscle or nerve, 537./- Intestinal concretions, 274, 280 ; juice, de- scription of, 204 ; quantity of, 204. Intestines, digestion in the, 201; excre- tion from, 270. Iodine in tissues, 4. Iris, development of, 392 ; nerves of, 341 ; strueture of, .S40. Iron, estimation of, in blood, 450 ; in urine, 471 ; in tissues, 5. Irritants, effects of, on muscles, 81. Irritation of the nerves of Special sense, 364. - Island of Reil, development of, 391. Iter a tertio ad quartum ventriculum, 391. Ivory, or dentine, structure of, 86. Jacob's membrane of the retina, 338. Jacob, Sarah, case of, 192. Jaundice, blood in, 245. Jolly and Mussat on proligerous pel! 426. Joule on the dynamical theory of 1 124. E Kangaroo, hair of, 267. Kerona, formation of, 47- Key of Du Bois-Reymond, use of, 528. Kellie on cranial circulation, 220. Kidney, excretion from the, 255 ; of i rides by, 261 ; phosphates by, 261 ; phates by, 261 ; inorganic matters 261 ; functions of the, 257 ; devi ment of the, 396 ; structure of the, Kieman on the Liver, 249. Kiestein in urine, 484. Kircher on blood corpuscles, 64 j om table blights, 438. Kirchoff on Frauenhofer's lines, 139. Kirk on smell of mangrove swamps, 3 Kirks on embolism, 244. Knapp, apparatus for holding head du ophthalmometric measurements, measurements of optical constants 570. Knife of Valentine, 517- Knox on contractions of the iris, 342. Kblliker on connective tissue, 79 ; oi ' velopment of the limbs, 388 ; on s1 ture of the lungs, 226 ; on mus( contractility, 633 ; on developmei nervous system, 390; on the re 338 ; on rods of Corti, 346 ; on S] cord, 284; on development of ~ thyroid gland, 395 ; on veratrin, (VI villi, 205. Kolpoda, formation of, 47. Kratzenstein and Kemplen on pronui tion of vowels, 353. Krause on the retina, 338 ; on numb ' sweat glands, 265 ; on touch bo 335. Kiichenmeister on development of 1 worms, 407, 408. Kuhne, on muscle, 75 ; method of ob ing mt^cle plasma, 490 ; apparatu experimental on effect of solutior muscle or nerve, 637 ; on protopl 104 ; on termination of nerve muscle, 350. Kussmaul and Tenner on cranial cir tion, 222. Kutzing-on development of prolig( pellicle, 426. Kymographion of Ludwig, use of, description of, 559. Labia, development of, 398. Labour, effect of, on amount of ca excreted, 230. Labyrinth of the ear, 347-. Lachrymal gland, 337 ; nerves of, 324 Lactation, nerves in, 324 ; phenomex 403. INDEX. S93 actic acid, chemistry of,. 27 ; in urine, 477. actose, chemiatry of, 26. agophthalmia, 819. ambert, the porcupine man, 417. amina spiralis of cochlea, 346.- fiminEB dorsales, 384 ; ventrales, 384. ampyris noctiluca, 144. .ancelet, 390. laryngoscope, the, 364 ; description of, 579. larynx, changes in, at puberty, 377 ; de- velopment of, 395 ; artificial of Mliller, 578 ; muscles of, 351 ; nerves of, 320 ; structure of the, 351. laryngeal sounds in auscultation, 227. .atent heat, 126. laticilerous vessels, bacteria in, 439. auric acid, chemistry of, 22* lavater's physiognomy, 303. jaw, of battle among animals, 419 ; of contraction of Pfiilger, 542; of mole- cular attraction, 41 ; physical and vital, of molecular coalescence and dislnte^a- tion, 40, 45; regulating, morbid action oi nervous system, 289. jawes and Gilbert on origin of fat, 24 ; on food, 190. jawe on blood coi^uscle, 64. jawrence's definition of life, 184 jead, chromate, use of, in histolopy, 523 ; effect of, on muscles, 369 ; In tissues, 5. je Baillif on the diaphragm of the micro- scope, 498. jee, Dr Robert, on nerves of the uterus, 325. Je Gallois on reflex actions, 311. Liehmann onhsematocrystallin, 31 ; on effect of diet on excretion of sulphates by Iridneys, 261 ; on occurrence of free hip- puric acid in urine, 459 ; on effects of exercise on excretion of urea, 259. Leidy on structure of bone, 91. Lemair^ on air of hospitals, 433. Lemur, hair of, 267. Lens, compound achromatic, 501 ; of eye, development of, 392 ; immersion, use of, 508. Jenses, arrangement of, in microscope, 503; faults of simple, 500 ; im^es formed by, 137 ; varieties of, 136. Leptothrix, formation of, 48. Letheby on ovum of woman, 383. Letzerich on villi, 205, Leucin, chemistry of, 17 ; in urine 485. Leuckhart on bees, 414. [^ucocythaemia, history of, 208. Leucocytha of Robin, 209. Leucocytotical fluid of Virchow, 209. Leukhsemia of Virchow, 209. Lewenhoeck on the microscope, 498 ; on blood corpuscles, 64. Lever, properties of, 112 ; varieties of, in human body, 112. Ley on a case of diseased spinal cord, 313. Lieherktihn on glands of intestine, 202; on injecting tissues, 522 ; on the use of a reflector for microscope, 498. Lienteria, 274. Liehig on animal heat, 247 ; artificial faeces, 273 ; on chemical nature of fer- mentation, 437 ; experiments on origin of fat, 24 ; respiratory food, 230 ; theory of compound radicles, 6 ; on effects of exercise on excretion of urea, 259 ; on conversion of uric acid into urea, 258 ; on acidity of urine, 262, 459. Life or vitality, definition of, 184; theory of, 184. Ligamentum membranaa tectorise in coch- -lea, 346 ; spirale of cochlea, 347. Light, chemical acbion of, 143 ; diffraction of, 137 ; dispersion of, 138 ; emission, • theory of, 134 ; relation of heat to, 143 ; interference of, 137 ; law of refraction of, 135; polarization of, 141, 142; propa- gation of, 134 ; reflection of, 134 ; theo- ries of, 134 ; undulatory theory of, 134 ; velocity of, 134. ^Limbs, development of the, 388. Lime water, Bennett on pellicle on, 44. Lipsemia, 245. Lipoma, 279. Lips and cheeks, functions of, 193. Liquidity, 114. Liquor, amnii, 385 ; puris, 69 ; sanguinis, 241. Lister on coagulation of blood, 241; on blood corpuscle, 64 ; on structure of blood vessels, 85 ; observations on pig- ment cells of frog, 39. Liston on lai-yngoscope, 579. ' Liver, analysis of, 495 ;-development of, 894 ; excretion from the, 249 ; fat in the, 251 ; glycogenic function of, 251 ; structure of 249. Livingstone, Dr, on smell of Mangrove swamps, 331. Lockhart Clarke. {See darke.) Locomotor ataxia, '314, 364 ; loss of mus- cular sense in, 350. Local paralysis, 364. Logwood, use of, in histology, 521, Longet's experiments on cerebrum, 294 ; on movements on injuring humour of the eye, 308 J on experiments on spinal cord, 310. Ludwig on static force of heart, 215 ; on the kymographion, 217 ; description of, 559 ; method of injecting tissues, 521. Lungs, structure of, in birds, 226 ; circula- tion in, 224. Lungs, development of, 395 ; excretion from the, 248 ; mode of measuring quan- tity of air in inspiration and expiration, 561 ; structure of the, 226. Lussana on cereb'ellum, 305. Lymph, analysis of, 453 ; channel, 206 ; corpuscles, 60 ; sinus, 206. Lymphatic glands, description of, 206. Lyon's, Dr, terms given to molecules, 36. Lyonet on the microscope, 498. M Madden on absorption by the skin, 269. Magenda on corpora quadrigemina, 307 ; 594 INDEX. on the 5th pair of nerves 318 ; experi- ments on food, 189 ; on injecting foreign matters into blood vessels, 244. Magenta, use of, in Histology, 520. Magnesium, carbonate in tissues, 28 ; phos- phate in. tissues, 29 ; in tissues, 5. Magnetic induction, 145. Magnetism and diamagnetism, 146. Magnetism, properties relating to, 144. Magneto-electricity, 156. Magnets, 144 ; attraction and repulsion of, 145 ; constitution of, 145. Magnus on gases of the blood, 232. Malacosteon, blood in, 245. Malapterurus electricus, ,159, Male organs of generation, development of, 397. Malleus, the, 348. Malpighi on blood corpuscles, 64. M^lpighian bodies of kidneys, development . of, 396 ; bodies of the sple^, 206. Mammal's, apermatozoids in, 380. Mammary glands, structure of, 403. Man, duration of virility, 378 ; , time of puberty, 377. Mandl on the corpuscles of Camelidse, 61 j on blood corpuscle, 64. Manganese in tissues, 5. Mania, 362. Mantegazza on proligerous pellicle, 426 Marcet on analysis of fseceSj489 ; on faeces, 272: Marey on forces of circulation, 216 ; cardio- graph, description of, 554; sphygmograph, 217 ; sphygmograph for the wrist, descrip- tion of, 553 ; triple sphygmograph, de- scription of, 552 ; tambour or drum, description of, 554. Margarin, chemistry of, 20. Marriotte's experiment on entrance of optic nerve, 344. Marshall Hall on diastaltic actions, 284, 310; method of restoring persons asphyxi- ated, 234. Martens on temperature of birds, 248. Mastication, 192, 194.' Matteucci, on absorption of fatty matter, 118 ; muscular pile, 166 ; and Savi on electrical fishes, 160 ; secondary contrac- tion of muscles, 168 ; on the torpedo, 161. Haudesley on mental fa>cu1ties, 299. Max gchultze's definition of a cell, 50. Mayer on heat, 124. Mayo on decussation of nerve tubes in optic commisure, 316, 344. McDonnell on glycogenic function of the liver, 252. McKendrick, experiments on heterogenesis, 423, 435 ; on apparatus for measuring electric shocks in tetanus, 540. Measles, blood in, 245. Meatus of ear, 348. Mechanical, equivalent of, heat, 124 ; pro- ' pertles, 110. Mechanism of respiration, 227. Meckel's cartilage, development of, 388. Mediastinum testis, structure of, 379. Medidla oblongata, function of, 308 ; effects of injuries to, 308 ; general structu 283 ; connection with spinal cord, 2 Medusa aurita, development of, 406. Medusa, wreck of the, 191, Melanin, chemistry of, 31. Melissic acid, chemistiy of, 22. Melloni's pile, 150. Membrana, basilaris, in cochlea, 346 ; 1 strEita in retina, 338 ; granulosa of o'< 375 ; tympani, 348. Membrane of Corti, 346 ; of Descimet, haptogen of Aseherson, 36 ; Jacob, X Membranes, vibrations of, 133. Memory, 299, Menstrual fluid, microscopic charactei 374. Menstruation, phenomena of, 374. Mensuration and demonstration with roscope, 510. Mental acts, phenomena of, 179 ; facu1 classification of, by psychologists, by phrenologists, 300 ; sensations, 3 Mercury, effect of, on muscular aci ,369; nitrate of, in volumetric pre for urea, 473 ; on secretion of bile, 2 Merino sheep, 416. Mesmerism, 359. Metallic elements, 3. Metals in tissues, 29. Meyer Xothar on absorption of carh acid by blood, 232; on absorptio: gases by the blood, 122 ; metho obtaining gases of blood, 452. Miahle's experimentS'On ptyalin, 195. Micrometer, use of, 510. Microscope, art of demonstrating, I adjustment of, 504 ; bull's-eye conder of, 509 ; cells, materials for making, ■■ construction of the, 603 ; eye-piece S08; facility for observation and dei stration, 505; Gillett's condenser 509 ; history of, 496 ; how to desc objects seen with, 514; howtomea magnifying power of, 511 ; how observe with a, 513 ; mechanical i of the, 503; mensuration and dei . stration with, 510 ; methods of illun . tion of, 508 ; mode of increasing ma fying power, 503; objective of i optical principles of, 499 ; portabilit 505 ; price of, 510 ; simple, 500 ; stf ness of a, 504 ; test objects for, 510. Micro-spectroscope of Sorby and Browi 451. Microzymes of Bechamp, 104, Middle ear, 348. Middle frontal process, 388. Miliary tubercle, 278. Milk, adulterations of, 405 ; analysis, ash of, 405 ; chemical compositioi 404; development of penicilliuin globules of, 439 ; fever, 403 ; histo of, 403 ; sugar, 26 ; teeth in man, 19' Mill on mental faculties, 299. Mineral concretions, 280; degenerai 280 ; matter, amount excreted, 275 ; : ter, estimation of, in blood, 448 ; poi affecting blood, 245 ; principles, 27. INDEX. 595 Mirrors, formation of images in, 135 ; theory of formation of images in convex, 564 ; of microscope, 508. Mltchel, James, case of, 330. Mohl, Yon, on primordial utricle, 50 ; on protoplasm, 104. Mohr's burette for volumetric analysis, 465. Molecular, elements of the tissues, 85 ; movements, 3S ; properties, 109 ; theory of organisation, concluslous as to, 98. Molecule, definition of a, 3. Molecules, chemical composition of, 35 ; ^ development of, 36 ; histogenetic, defini- tion of, 36; histolytic, definition, 36, 37 ; physical properties of, 36. Moleschott on pneumogastric, 821, Mollusca, fecundation of, 381. Monas lens, development of, 47, 424. Monkey, hair of, 267. Monochord of Helmholtz, description of, 573. Monoideism, 357. Monomania, 362. Montraucon, smell of sewage at, 831. Montgomery's observations on protagon, 46. Moore, Ann, of Tutbury, 192. Moore's test for sugar in urine, 480. Moral faculty, 300. Morbid cells, 69. ' Morbid conditions of the blood, 242 ; de- generations of texture, 280 ; growths, 270 ; diaphanous bodies in growths, 44. Morgagni on development of generative organs, 397. Mormyrus longiplnnis, 169. Morrell on mental faculties, 299, Mortification, 279. Motion, 289. Motores bculorum, 816. Mouse, hair of, 268. , Mouth, form of, in pronouncing vowels, 354. Movements, in cells, 67 ; ciliary, difi'erent views of, 78. Mucin, chemistry of, 11. Mucus in bile, estimation of, 455 ; in urine, 487. Mucous layer of germinal membrane, 884. Muldei^s theory regarding albumin, 190. Mule, 415. Muller's, arteriss helicinse, 224; duct of, 897 ; on development of generative or- gans, 307 ; fluid for hardening tissues, 620 ; on develppment of human foetus, 398 ; on'artlficial larynx, 578; on rapid ity of nerve current, 287 ; on position of objects as seen by the eye, 343 ; on fibres in retina, 339 ; apparatus for experiments on vocal cords, 678 ; on sonorous undu- lations in water, 346. Multipolar nerve cells, 06. Munro on cranial circulation, 220, 221; on intestinal concretions, 274. Munk on rapidity of nerve current, 287. Murexide test for uric acid, 475. - Marie on fungi in cavities of birds, 440. Muscardine, nature of, 439. Muscle, analysis of, 491 ; qhemical compo- sition, 75 ; clot, analysis of, 75, 491 ; Helmholtz on chemical composition of, 75 ; Kiihne on chemical composition of, 76 ; development of, 75 ; evolution of electricity by, 82, 533; effects of electri- city on, 82 ; fatigue of, 83 ; effects of irri- tants on, 82; effects of poison on, 82; nerve terminations in, 350; plasm, Kuhne's method of obtaining, 490 : se- rum, analysis of, 490 ; specific heat of, 125; sugar, ^7; telegraph, 629. Muscles of deglutition, 196 ; of the ear, 349 ; of the larynx, 351 ; of mastication, 194 ; of respiration, 227, Muscular fibre, 73 ; fibrillse of, 73 ; fasciculus of, 73 ; structure of, 74. Muscular effect of contraction in venous circulation, 219 ; experiment on effect of irritation on, 536; experiments on muscular system, 525 ; experiments on, 524 ; fatigue, 83 ; sense, 849. Music, physical theory of, 131. Musical sounds, 180. Musk deer, hair of, 268. Myelin, chemistry of, 12. Myographion of Helmholtz and Dn Bois- Beymond, calculation in experiment with, 551 ; mode of making experiment with, 549 ; of Ffliiger, description of, 541. Myopia, 343. Myopic eye, measurements of, by Knapp, 570. Myosin, analysis of, 491 ; chemistry of, 10. Myristic acid, chemistry of, 22. N Nachet's pocket microscope, 606. Nails, structure of, 269. Naphtha, use of, in Histology, 524. Naples, sewage in, 831. Nasse on analysis of chyle, 463. Natural selection, description of 415. Neefs, hammer in induction apparatus, 627. Nelson, Dr Henry, on development of tape- worm of cat, 406 ; on the development of ascaris mystax, 48. Nematoda, 281. Nerve cells, 65 ; Beale's, 65 ; bipolar, 65 ; functions of, 66 ; in gasserian ganglion, 65 ; multipolar, 65 ; sbape, 65 ; size of, 66 ; structure of, 65. Nerve current, 169 ; mode of demonstrat- ing rapidity of. 6^. Nerve-tubes, chemical composition of, 96 ; effects of electricity, 97 ; mode of demon- strating effects of electricity on, 542; effects of reagents on, 95 ; evolution of electricity by, 97 ; functions of, 96 ; neurilemma of, 94 ; reaction of, 96 ; structure of, 94. Nerves of common sensation, 286 ; efferent, definition of, 289 ; muscles of mastica- tion, 194 ; of motioui 286 ; of the pupil, 341; in various reflex actions, 312; of the salivary glands, 195 ; of special sen- Id 596 INDEX. sation, 2S6 ; structure of, 286 ; of tbe tongue, 193 ; varieties of, 286. Nervous system, aphorisms regarding, 293 ; anal jsis.of, 494; congestive derange- ments,, 365 ; development of, 390 ; epochs in history of discovery in, 316 ; influence > of, in nutrition, 237 ; morbid actions of, 289 ; reflex derangements, 867 ; special (unctions of, 293 ; structure of, 282 ; structural deradgedients, 366 ; tonic de- rangements. 368. Nervus patheticus vel trochlearis, 317. Neubauer and Togel on ammonia in acid urine, 471. Neural disorders, 363. Neuralgia, 317, 363. !^euro-Bpinal disorders, 364. Newton, on refrangibility of light, 138 ; law of molecular attraction, 41 ; rings, 140. iSrichol's prism, 142. Nitric acid, use of, in Histology, 620. Nitrogen, 27 ; in respiration, 231 ; in tissues, 3. Nitrogenous food, 189 ; matters, excretion of, 267. Nobili, on animal electricity, 164; on elec- trotonus, 172 : on the galvanometer, 149. Noble, Mr, case'of paralysis of taste, 334. Noel's test for bile, 458. Non-contractile fibres, functions of, 78; molecular fibre, 73. Non-metallic elements, 3. Non-polarizible electrodes of Du Bols-Eey- mond, description of, 534. Non-saponiflable fats, 19. Non-voluntary contractile filjres, 77. Northnagel on touch, 336. Nose, development of, 393. Nuclear flbres, 76 ; chemical composition of, 76 ; in giraffe, 76. Nucleus, definition Of, 50. Nutrition, abnormal, 276 ; blood In, 236, 237 ; diseases of, 277 ; function of, 187 ; nervous system in, 237. O <]iberhEguser*S model microscope, 499, 504. Object glass, adjustment for covering glasses in, 602. Objective of a microscope, 603, 507. Obstructions in bowels, 274. Ocular spectra as variously produced, 344. CEdema, 277. CEnanthylic acid, chemistry of, 22. CErsted on compressibility of fluids, 114 ; onsdetection of electrical currents, 148 ; discovery of electro-magnetism, 165. CKsopbageal glands, 196. CEsophagus, nerves of, 320. Olfactory, bulbs, development of, 393; nerve, 316. Oleic series of fatty acids, 22. Olein, cbem. of, 20. Oleo-pbosphoric acid, preparation of j 495. Oligo pyrenEemia,,245. Omphalo-enteric duct, 393. Omphalo-mesenterib vein, 394. Onimus on contagia, 104 Ophidians, lungs of, 226. . Ophthalmometer of Helmholtz, 342; de- scription of, 668 ; Donder's method of using, 570 ; measurements made by means of, 670; mode of /Using, 668; optical principles of, 665. Ophthalmoscope.of Helmholtz, description of, 571. Ophtiahnotrope of Rente, 338 ; descrip- tion of, 663.' Opisthotonos, 363. Opium, physiological effects of, 363. Optic, nerve, 316; thalami, 306; develop- ment of, 391 ; tubercle, 307! Optical, constants,measurements of Enapp, Woinow, and Adam&ck, 570 ; principles of, 499 ; properties of bile acids and pig- ments, 467 ; of haemaglobin, 450. Optics, properties relating to, 134. Organs of the body, weights of, 112; speci- fic gravity of, 116. Organic electricity, 157. Organogenesis, explanation of, 402. Omithorynohus, hair of, 268. Orton on reproduction, 382. Osmic acid, use of, in Histology, 620. Osmometer, description of, 116. Ossein, preparation of, 493. Osseous labyrinth, developineht of, 393. Osteoma, 279. Otter-sheep, case of, 415. Otoconia in the ear, 346. Otoliths in the ear, 346. Ovaries, structure of, 374: definition of, 372. Over-tone apparatns ot Appunn, descrip- tion of, 674. Ovisac of Barry, 376 ; structure of, 376. Oviparous reproduction, 373. Ovum, structure of, 382 ; descent of, into uterus, 382. Owen on the Gibbon's voice, 419 ; on par- thenogenesis, 406. Oxalate of calcium in tissues, 28; as a sediment in luine, 486. Oxalates in tissues, 28 ; in urine, 477. Oxalic acid, cheimistr? of, 23; series ot fatty acids, 22. Oxyfeeii, 327 ; absorption of in respiration, 227. Oxyhsemoglobin of Hoppe-Seyler, 32. Faccini on touch corpuscles, 335 ; on the electrical organs of the gymnotus elec- tricus, 159 ; on the electrical organs of the torpedo, 158. Paget on complen^ntal nutrition, 237. Palate, development of, 393. Palmitic acid, chemistry of, 22. Pancreas, development of, 395. Pancreatic juice, action of, on chyme, 201; analysis of, 466 ; description of, 203 ; quantity of, 204. Fancreatin, description of, 203 > prepara- tion of, 455, Panspennists, 425. INDEX. 597 Papaver Orientale, phosphorescence in, 144. Farama^cium, formation of, 47. Par-electronomy, 167. Paraffine mixture for microscopic sections 578. Paraplegia, 363. Parasitic growths, 281. Farf our du Petit on sympathetic, 325. Parkes on effects of exercise on excretion' of urea, 260 ; on food, 190 :' on urine, 266. Parry on bulimia, 191. Parthenogenesis, nature of, 405. Parturition, phenomena of, 401 ; time of, in woman, 401. Pascal's principle of equality of pressure, 114. Pasteur, on bent tubes retaining germs, 434 ; heterogenesis, 422, 426 ; on effects ' of temperature upon germs, 435 ; ex- ' pediments on air collected at a great height^ 436. Pavy on glycogenic function of the liver, 252. Pectoriloquy, 228. Pediculus, 281. Pelargonic acid, chemistry of, 22. Pellicle on lime water, Bennett on, 44. Pelou^e on analysis of chyle, 463. Penicillium, development of, in mUk glo- bules, 439 ; formation of, 48. Penis, developu^ent of, 398. Pepe, skull of, 302. Pepsin, action of, 203 ; chemistry of, 11 ; 'Separation of, 454. Perception, faculty of, 299. I'erilymph on the ear, 348. Perkins on compressibility of fluids, 114. Periplast of Huxley, 53. Fettenkofer's test for bile acids, 458ii Fettigrew on muscular wall of the heart, 214. Peyer's glands, action of, 202. Pf aff on animal electricity, 164 ; on elec- trotonus, 172. Ffliiger on electrotonus, 172 ; falling ap- paratus, description of, 539 ; on inhi- bitory action of the pneumogastric nerve, 321 ; on termination of nerves in salivary glands, 196 ; avalanche theory of nervous action, 175; experiment to shew, 544 ; law of stimulation, 173 ; experiment to shew, 642; on contraction, 171. Pha,koscope of Helmholtz, description of, 671. Phanerogamia, reproduction in, 99. Phenylic acid in urine, 477. Philip Wilson on removal of brain and spinal cord, 325. / Phlebolites, 280. Phosphate, of ammonium and magnesium, 29 ; calcium in tissues, 29 ; of lime as a deposit in urine, 487. Phosphates, excretion of, ^y kidneys, 261; of magnesium in tissues, 29; of potassiiun in tissues, 28 ; of sodiiun In tissues, 28 ; as sediments in urine, 48 ; in tissues, 28 ; in urine, tests for, 468 ; in urme, effect of disease on excretion, 262. Phosphorescence, 143. Phosphoric acid, process for estimating amoimt in urine, 468, 470, 471. Phosphorus in tissues, 4. Phrenology, 300 ; function of cerebellum according to, 306 ; objections to, 301. Physical, law of molecular coalescence and disintegration, 40; physical and chemical properties of cells, 60 ; sensations, 300 ; theory of music, 131 ; and vital proper- ties of the tissues, 105. Physiological chemistry, 444 ; experimen- tal, 526. Physiology, general, 2; practical defini- tion of^ 444 ; special, 187. Picrotoxme, physiological effect of, 369. Pigeon, removal of brain from, 295 ; varieties of, 418. Pigmentary, principles, 30 ; degeneration, 280. Pigment cells, 67 ; effects of acidjg on, 67. Pigment* of bile, mode of preparing, 457- File of Volta, 152. Pineal gland, description of, 207. Fineau on heterogenesis, 422 ; on develop- ment of proli§:erous pellicle, 426. Fiorry's hssmatitis, 208.| Pipette, 465. Pitch of musical note, cause of, 131. Pituitary gland, description of, 207. Placenta, formation of, 400 ; functions of, 401. Plague, blood in, 245. Planer on gases of intestine, 272. Plants, fecundation in, 378. Plate, of battery, definition of, 151 ; colours of thin, 140. Plethora, 245. Pleurosthotonos, 363. Ploesers microscope, 499. Pneiunatic properties, 121. Pneumogastric nerve, 320; cardiac branches of, 320. Podophyllin on secretion of bile, 254. Poggendorff's wheel, description of, 538. Pohl's commutator, description of, 528. Poisseuille on the discharge of fluids through capillMy tubes, 119 ; hsema- dynamometer, description of, 558; on static force of heart, 215. ' Polar bear, hair of, 268. ' Polarizable electrodes of Bu Bois-Bey- mond, 630. Polarizatioii of light, 141. Pole of batteiy, definition of, 151. Polypyrenamia, 246. Fomum Adamii, 377. Pons Varolii, description and function of, 308 ; development of, 391. Porcupine man, case of, 417. Pores, physical, 108 ; sensible, 108. Porosity, 108. Portal blood, description of, 249 ; circular tion, 223 ; vein-development of, 394. S98 INDEX. Posture, effects of, on the pulse, 216. Fotafisium, acetate, use of in Histolo^, 624; carbouaite in tissues, 28; chloride in tissues, 28 ; phosphates in tissues, 28 ; salts in tissues, 6 ; sulphate in tissues, 29 ; sulphocyanide in saliva, 29. Pouchet upon effects of temperature upon germs, 435 ; on heterogenesis, 422 ; on development of proligerous pellicle, 426 ; proligerous pellicle of, 46, 104, 423 ; law as to development of animalcules, 425. Pouchet, Jolly, and Musset's experiments on air collected at a great height, 436. Powell's microscope, 499. Practical, experimental physiology, 525; histological -physiology, 496 ; physio- logical chemistry, 444 ; physiology, defl- nition of, 444. Presbyopia, 343. Pressat on smell, 330. Pressure of liquids, 114. , Prevaz on galvano-puncture, 165. Preyer on finding the quantity of hsema- g:lobin by spectrum analysis, 451. Primitive groove in germinal area," 384 ; ■vertebrse, 384. Primordial kidheys, development of, 396 ; utricle of Von Mohl, 60; vertebras, changes in, 386. Principles, albuminous, 8 ; fatty, 18; mineral, 27 ; pigmentary, 30. Frochaska on reflex actions, 311. Progjlottis, definition of, 409. Proligerous disc, 375 ; pellicle of Pouchet, 423. Prometheus, fable of, 184. Properties, relating to acoustics,' 129 ; of cells, 50; relating to electricity, 146; relating to heat, 123 ; relating to mag- netism, 144; mechanical, 110; mole- cular, 109 ; relating to optics, 134 ; pneu- matic, 121 ; general, of the tissues, 106. Propionic acid, chemistry of, 22. Protagon, chemistiy of, 12 ; preparation of, 495; reactions of, 45. Protophyta, conju^tion of cells in, 99, Protoplasm,- definition of, 50. Protozoa, reproduction of, 373. Prout on urine, 256. Proximate principle, definition of, 7 ', groups of, in body,_ 8. Prussian blue, injecting flmd, 623. Psychology, 299. ' Ptosis, 317. Ptyalin, chemistry of, 12 ; mode of pre- paring, 453 ; in saliva, 194. Puberty, 377. Pulex penetrans, 281. Pulley, properties of, 113 ; example in human body, 113. Pulmonary circulation, 224 ; circulation of the blood, 212. Pulp of tooth, structure of, 86. Pulse, effect of age on, 216; effect of I exercise on, 216 ; disease, effect of, on, 216 ; phenomena, of, 216 ; effect of pos- ture on, 216; effect of $ex on, 216; effect of time of day on, 216. Pupil, the, 341. Pupillary membrane, development of, 392. Purgative action explained, 117. Piurgatives, effect of, on secretion of bile, 263, 254. Purkinie's axis-cylinder in nerve tube, 96. ' "^ Purpura, 245. ' Pus, 69 ; cells of, 69 ; Bennett on forma- tion of, 209 ; in urine, 487. Pyin, chemistry of, 11. Quantity of food, 190 ; of digestive fluids, 204. Quekett on nuclear fibres of giraffe, 76; on structure of bone, 91. Quetelet on atmospheric pressure on the surface of the body, 121. Quinoidine, chemistry of, 12. Raasch, the, 159. Rabbit, hair of, 267. Rachitis, blood in, 245. Badcliffe on electrotonus, 172; theory of a muscular current, 167. Radiant heat, 128; ^^yndall's researches on 128. ^Radicles, compound, 6. Raia batis, 160. Rainey on lungs of birds, 226 ; on mole- - cular formations, 37 ; on duct' of sweat gland, 264; on formation of rounded bodies from viscous solutions, 42; obser- vations on stkrch granules, 37. Ramsden on accommodation of eye to dis- tance, 341. Rapidity of circulation of blood, 219; effect of, on respiration, 219 ; of the nerve current, 287 ; mode of measuring by the myographion, 645. Raspail on cells, 52 ; theory of compbund radicles, 6. Rathke on development of cranium, 387 ; on development of larynx, 395 ; on de- velopment of ureters, 396. Reade, Winwood, on savage African tribes, 420. , Reagents, effects of, on blood corpuscles, 63 ; on nerve tubes, effects of, 95. Reasoning, 299. Redfem on changes in diseased cartilage, 89. Redi on heterogenesis, 421. Bees on blood corpuscles, 65 ; on analysis of chyle, 453. Reflection of light, 134. Reflex actions, examples of, 312 ; on dia- staltic actions, 310 ; derangement of the nen^ous system, 367. Refraction, double, 141 ; of light, 136. Refrangibility of light, 138. Reichert's connective tissue theory, 79. Reid on a case of diseased spinal cord, 313. Beid, John, on asphyxia, 234 ; on cranial INDEX. 599 circulation, 220 ; experiment on contrac- tility, 178 ; mode of demonstrating, 530 ; experiments on glos30-phar3'ngeal nerve, S20; on muscular wall of the heart, 214 ; on pneumo-gastric, 321 ; on sympa- thetic, 325. eil. Island of, 391. einhardt on fatty degeneration of tiells, 70. elative weight. 111. emak, band of, in nerve tube, 96 ; on development of the liver, 394 ; a^d Kolliker on development of nervous system, 390. eproduction, 372;' abnormal, 440; of cells, 56 ; fissiparous, 373 ; oviparous, 373 ; of phenomena of heat, 373 ; vivi- parous, 373. eptiles, fecundation in, 381 ; spermato- zoids in, 880. Reserve air, 229. fsidual air, 229. esonators. of Appunn, description and uses of, 575. espiratlon, 226 ; amotint of carbon ex- creted in, 230 ; effects of, on'atmospheric air, 229 ; on effects of, on blood, 231 ; effects of, on smell, 329; effect of f^e on amount of carbonic acid in, 231 ; sex, 231 ; external temperature, 231 ; season, 231 ; period of the day, 231 \ develop- ment of body, 231 ; sleep on, 231 ; dis- ease, 231 ; experlmenjis on, 560 ; effects of different articles of food on carbon in, 230; of egg, 400; mechanism of, 227; orgaus of development of, 895; watery vapour in, 231. espirations, number and extent of, 228 ete, mucosum, 267 ; testis, structure of, 379. etinacula of ovum, 375. etina, expeiiment to shew inversion of image on^ 562 ; structure of, 338 ; ap- pearance of, as seen by ophthalmoscope, 672. eute's ophthalmotrope, 333 ; description of, 563. heocord of Du Bois-Reymond, 542. heophoric tubes of Du Bois-Reymond, 635. heotrope of Pohl, description of, 523. heumatism, blood in, 245. hinobatus electricus, 159. hizomorpha^ subterranea, phosphores- cence in, 144. ichardson on coagulation of the blood, 241. igidity cadaveric, 83. itter on electrotoniis, 172; mode of pro- ducing tetanus, 639. oberts on blood corpuscle, 64 ; on effect of magenta on blood corpuscles, 63. Dbertson Arj^U, expeiiments on germs in the air, 433 ; on heterogenesis, 423. obin on wutagla, 104 ; on development of white florou^ tissue, 77 ; on elecLric organs of the skate, 160 ; embryoplastic matter of, 104 ; on leucooyths, 209. Rods, and cones of retina, 338 ; of Corti, 346 ; vibrations of, 133. Rolando's experiments on braia> 285 ; fissure, development of, 392. Ross* adjustment in object glasses for coverinj? glasses, 502 ; microscope, 499. Rotation of electro-magnet, 146 ; of raj of polarized light, 143. Rotatory movements on injm'Ing corpora quadrigemina, 307. Royer on mental faculties, 299. Ruge on gases of intestine, 272. Ruhmko]^'s induction coil, 157. Rumford, Count, on heat, 124. Rutherfbrd, ^periments on germs in the air, 434 ; on heterogenesis, ' 423 ; ou secretion of bile, 253. Rutic acid, chemistry of, 22. S Saccharimeter, description of, 483. Sacculus in theear, 34tJ. Sacs of the embryo, 385. Saline solutions, effect of, on muscle or nerve, 537. Saliva, amount of, secreted daily, 105 ; analysis of^ 453 ; chemical composition of,J.94 ; description of, 194 ; functions of, 195 ; action of poisons on, 196 ; quantity of, 204. Salivary cell, movements of molecules in, 38 ; glands, description of, 194 ; develop- ment of, 395 ; secretions, different effects of, 195. Salivation, nerves In, 324. Salter on auscultation, 228. Salts in' tissues, 28, Saunderson Burden, case of delicacy of touch, 337 ; on contagia, 104. Sapidity as necessaiy for digestion, 190. Saponifiable facts, 20. Sarjcin, chemistry of, 16. Sarcinee in urine, 488. Saroolatic acid, chemistry of, 27. Sarcolemma of muscle, 73. Saussure on hygrometiic property of hair, 269. Saviirt on production of musical notes, 130 ; experiments on sound, 348. Savory on blood corpuscle, 64 ; on develop- ment of muscle, 75 ; on development of muscular fibre, 53. Scale, diatonic, 131 ; chromatic, 132. Scarlatina, blood in, 245. Scolex definition of, 409. ' Schaafhausen on proligerons pellicle, 426. Scharling on carbonic acid from lungs, 231. Schelling on mental faculties, 299. Schclslce and Jaager on rapidity of sensa- tion, 287. Scherer's test for inosite, 492. Scherer, Rosow, and Heintz, on melanin, 31. Schiek'9 microscope, 499. Schiff on electrotonus, 172 ; test for uric acid, 476. Schlelden and Schwann on blastema, 104 ; theory of cell formation, 62. 6oo INDEX. Schmidt on coagulation of the blood, 211. Schrsuder -and Dusch on experiments on germs in the air, 432. ^ 8chr5n and G-rohe on development of G-raafian vesicles, 375. Schutze's experiments on germs in the air, 432. Schultze, Max, on organ of smell, 329 ,von Mood corpuscles, 64. Schwann, chemical experiments on germs in the air, 432 ; on development of mus- cle, 75 ; on development of white fibrous tissue, 76 ; white substance of,'in nerve, 94. Schwelgger on the galvanometer, 149. Scirrhus, 279. Scot Alison's sphygmoscop'e, 217 ; descrip- tion of, 555. Scrofula, blood in, 245. Sculptoi^s clay, use of, in experiment on muscular current, 534. Scurvy, fibrin In blood of, 245. Season, effect of, on amount of carbonic acid, 231 ; on urine, 260. Sebaceous glands, 266. Secale cornutum, effect of, on uterus, 869. Secondary digestion, 239. Secretion, 236, 238. Secretions in cells, 51^ Section cutter of Stirling, 517. Sediments in urine, 486. Seguia on heat, 124 ; on amount of sweat, 265. Sella turcica, 387. * Selection, in breeding, examples J3f, 41 S ; natural, description of, 415 ; sexual, ex- planation of, 419. Selllgue on, the microscope, 498- Sensation, ancient theories regarding, 180 ; classification pf, 300 ; defini^on of, 288. Sensations, nature of, 327 i phenomena of, 180 ; varieties of, 327. Sense of weight, 349. Senses, special, 327. Sensible pores, 108. Sensibility, 179, 286. Senso-motory nerves, 286. Sensorium commune, 311. Sensory aerves, electrical phenomena of, 176. Serolin, chemistry of, 19. Serous layer of germinal membrane, 384. Serum, estimation of, in blood, 448. Serpents, lungs of, 226, Serres on development, 402. Setschenow on absorption of oxygen by blood, 232. Sex, effect of, on amount of carbonic acid, 231 ; effects of, on Uie^ulse, 216 Sexual selection, explanation of, 419. fc'harpey on fibrous basis of bone, 91. Sheep, otter, case of, 415 \ wool of, 267. Shell of egg, 399. Siebold en development of bees, 412 ; on tapeworm, 406. Sight or vision, 337 ; experiments on, 562; organs of, 337. Silicic acid, 28 ; in urine, 471. Silicon in tissues, 4. ttilver, oxide, -test for bile pigments, 453 ; nitrate, use of, in Histology, 521. Simon on analysis of chyle, 453 ; on analy- sis of milk, 405: on development of thymus gland, Sga. Silkworms, disease in, 439. Sinapt£e, formation of mineral matter iq, 102. Sinus, pocularis, 380; urogenitalis, 397; uterine, 401. Size and weight, influence of, on secretion of bile, 255. Skin, 263 ; absorption by, 269 ; appendages of, 287 ; colour of, 267 ; cutis of, 264 ; epi- dermis of, 263; excretion from the, SuS; sebaceous glands of, 266 ; sweat glands of, 264. Skull, development of the, 387. Sleep, amount of carbon excreted in, 230 ; nature of, .354 ; and dreams, theory oL 356. Smallpox, blood in, 245. Smee's battery, 153. Smell, absence of, in individuals, 330 ; cause of, 328 ; conditions of, 329 ; »s connected with epidemics, 330 ; histology of organ of, 329 ; pathology of, 330. Smith, Dr, on amount of cai-bonic acid in respiration, 230 ; on food, 190 ; effects of exercise on excretion of urea, 259. Smith and Milner on amount of faeces, 270 ; on excretion of nitrogen by fseces, 273, Smith's microscope, 499. Sodium carbonate in tissues, 28 ; chloride in tissues, 28 ; pliosphates in tissues, s 28 ; salts in tissues, 5. Soemmering's foramen in retina, 339. Solar spectrum, 138. Soleil's saccharimeter, description of, 483. Solids, general qualitative examination of animal, 489 ; qualitative analyses of special, 490. Solly's arciform band, 283 ; hemispherical ganglion, 283. Somnambulism, 355 and 856. Sorby and Browning's micro-spectroscope, 451. Sorge Andreas on combination tones, 576. Sound, caufte o^ 129; intensity of, 129; velocity of, 129. Spansemia^ 245. Spasms, 363. Special senses, 327. Specific gravity, bottle for estimatinfr, 462; of various fluids and solids of the body, 116. Specific, heat, 125; ofblood, 126; of muscle. 125 ; weight of, 111. Spectra ocular, variously produced, 344. Spectroscopy, description of, 460. Spectrum analysis of bile, 33; of bUe pigments, 457 ; of blood, Z% 450;; Speech, 351. 363. Spermatozolds, 380 ; entrance of, into ovum, 38 1'; in different animals, 380 ; in urine, 488. INDEX. 60 1 herical aberration, 137; in mlcroBCope, low corrected, 600. hjgmoscope of Sco't Alison, 217. hygmograph, Marey's description of, 553; Marey's triple, 552 ; "Vierftrdt's, 217, 653. hygmographlc tracing, description of, !17. bygmoscope of Czermak, 556 ; of Scot ilison, description of, 656. hygmosphone of Upham, 217 ; descrip- tion of, 066. inal cord, general description of, 282, !09 ; disorders of, 362 ; eftects of various mbstances on, 315 ; experiments on, 109 ; gray matter, 285 ; histology of, 309 ; irritation, 362 ; nerres,322 ; pathological results, 3l3 ;' reflex actions of, 310. inal accessory nerve, 321. irit, use of, in Histology, 624. irometer of Hutchinson, 229 ; descrip- tion of. 561. leen, description of, 203 ; development 3f, 395 ; functions of, 206. ontaneous generation, discussion of, 421. rengel's air pump, 452. Martin, case of, 197. Vitus' ddnce, 358. Bdeler on Bilifuscin, 33. ig's horn, growth of, 218, lining of tissues, 520. ipes, the, 348. sirch, chemistry of, 25. irk, Br, on the electric organ in the skaie, 160. a,tic force of left ventricle, 215. eatic acid, chemistiy of, 22; series of f^tty acids, 21. earip, chemistry of, 20. eenstrup on alternate generation, 403; on development of aphis, 406 ; on de- velopment of tapeworm, 406. ^wart's Dugald, classification of mental i^tculties, 209. Et^ and Kllaatsh on taste; 332. mlitff'iB experiments on spinal cord, 310. Unuli, degree of, as affecting functions of nervous system, 290 ; of nerves, 288. irling's section cutter, 517. 3kes on the colouring matter of the blood, 32. omach, area of, 197 ; capacity of, 197 ; development of, 394 ; digestion in, 197 ; movements, of, 197 ; structitre of, 197 ; weight of, 107. Dkes on fluorescence, 139, rabismus and ptosis, 317. ramonium, effects of, on bronchi, 369. ricker's hot stage, 518. rings, vibrations of, 133. robila, definition of, 409. rychnine, effects of, on cord, -368 ; pro- ducing tetanus, 539. urgeon on electro-magnetism, 156. iccinic acid in urine, 477. idoriferous glands, 264. igar, acids related to, 27; cane, 26; diabetic, 26 ; grape, 26 ; milk, 26 ; muscle, 27 ; in the urine, preparation of, 479 ; in urine, estimation of, by saccharimetre, > 483. Sugars, and amyloid substances, 25. Sulphate of calcium in tissues, 29. Sulphates, excretion of, by kidneys, 261 ; In tissues, 29 ; of sodium in tissues, 29 ; in urine, test for, 468. ' Sulphocyanide of potassium in saliva, 29 ; of potassium, tbsts for, 453. Sulphur in tissues, 4. Sulphuric acid, 28, Sulzer on voltaic electricity, 163. Summation tones, description of, 676. Superior, laryngeal nerve branches of to the tongue, 193 ; function of, in larynx, 320 ; maxillary process, 388. Supra-renal capsules, Addison's disease of, 206; description ckP, 206; development of, 396. Sutherland on air required for hospital wards, 235. Swammerdam on the microscope, 498. Sweat, as affected by cold, 266 ; by pressure of the air, 266 ; f&od, 26S ; period of the day, 266 ; season of the year, 266 ; tem- perature, 266 ; amount of, 265 ; chemistry of, 265 ; glands, functions of, 265 ; sweat glands, number of, 265. Swedish filter paper, use of, in experiment, 534. Swine, development of thymus in, 395. Sylvester, method^ of restoring person asphyxiated, 234. Sylvian aqueduct, development of, 391. Symmer and Bufay's theory of electricity, 147. Sympathetic nerves, 286 ; influence on animal heat of, 325 ; exci to-nutrient properties of, 323 ; excito-secretory pro- perties of, 323 ; functions ot 327 ; senso- motory properties of, 322 ; effect of section of, 326 ; structure of system of, 322. Syncope, 441. Syntonin, preparation of, 491. Syphilis, blood in, 245. Syren, production of musical sounds by 130. Systemic circulation of the blood, 212. Systolic sound of the heart, 213. Sznbadfdldyon Aingiformpapilla of tongue, Tsenia, development of, 406, 407. Tambour or drum of Marey, description of, 554. Tannic acid, use of, in Histology, 620 ; de- velopment of, 406. Tape worm, development of, 406. Tarantism, 358. Taraxacum on secretion of bile, 254. Tarrari, case of, 192. Tartini on combination tones, 576. Taste, nerves of, 332 ; Histology of the organ of, 332 ; paralysis of, 334. Tatu-in, chemistry 0^16. Taurochollc acid, 250 ; chemistry of, 12. Taurylic acid in urine, 477. 602 INDEX. Tea and cofifee, effects of, on brain, 368. Tears, nerves involved in effusion of, 324. Telegraph for muscle expervments, 529. Temperature of arterial blood, 232; of the body, 246 ; circumstances affecting tem- perature of body, 246 ; effect of on amount ^of carbonic acid, 231, Tenesmus, 274. Teratology, deffnition^of, 440. Testes, descent of, in abdomen, 398 ; func-. tion of, 380 ; structure of, 379. Test objects for microscope, 610. Tetanus 363 ; of Bitter, mode of producing, . 539 ; definition of, 83 \ modes of produc- .. ing, 537. Tetanometer'of Heidenhain, description of, 537. I Tetraodon electrlcus, 160. Teeth, chemical composition of, 87 ; de- scription of, 192; analysis of, 493 ; func- tions of parts of, 88 ; periods of shedding milk teeth, 193 ; structure of, 86 j varie- ties of, 192. Thirst and hunger, causes of, 191. Thames, smell of the, 330. Thermo-electricity, 150.. Thermo-luminoua effects of the galvanic current, 154. Thier'&ch's injecting fiuid, 524. Thompson, John, on heat, 124. Thomson, Professor Sir W., on the divisi- bility of matter, 108 \ galvanometer of, 149. Thomson, .Allen, on heterogenesis, 421. Thrombosis, 214, Thudicum on the colouring matter of the bile, 33 ; on fluorescence, 140 ; on heemato-crystallin, 31 ; on colouring matter of the urine, 34. Thymus gland, description of, 207; de- velopment of, 395. Thyroid gland, description of, 207 ; deve- lopment of, 395. , . Tic doloreux, 317. Tidal air, 229. Timbre of musical note, 131 Tinnitus aurium, vibrations producing, 131. , Tissue, connective, theory, 79. Tissues, cell-elements of, 50 ; chemistry of, 2 ; elective affinity of, in growth, 236 ; fibrous ^elements of, 72 ; mode of injecting, 520 ; mode of preparing for microscopical use, 517; inorganic el&r ments of„4 ; preservation of, 524 ; mode of staining, 520 ; physical and vital pro- perties of, 105 ; tabular elements of, S3. Todd on function of cerebellum, 3o4 ; on functions of corpora striata and optic thalami, 306; on nerves of motion, 287. Todd and Bowman on structure of organ of smell, 329 ; on taste, 332 ; on papillss of tongue, 333. Tomes on structure of bone, 91 ; on struc- ture of dentine, 86. Tone-measurer of Appuon, 678. Tongue, functions of, 193 ; nerves of, 193 ; papillSB of, 333, Tongue-pipes of Appunn, description of, 576. Torricelli^e law of the velocity of efflux of a fluid' 119. ToruUe, formation of, 48 ; in urine, 488. Torpedo Galvani, 158. Touch, bodies, Wagner's, 335 ; ^Histology of organ of, 334; sensibility of, how measured, 335 ; sensibility of various parts of body, 335. Toxhsemia, blood in, 245. Toxic derangement of the nervous system, 368. Trabeculse of Bathke, 387. Tracheal sounds in auscultation, 227. Trachelius, formation of, 47^, Tradescantia, movement in cells of, 38. Trance. 302, 357. Transpimtion of gases, 123. Trecul on bacteria in laticiferous vessels, 439. Trematoda, 281. Treviranus on the external ear, 348 j defi- nitfoa of life, 184. Trichiurus electricus, 160. Tri&cial nerve, 317 ; paralysis of, 318. Trip hammer of Ffliiger, description of, 539. Triple phosphate of ammonia and magnfr* slum, 291 ; as a deposit in urine, 487. Trismus, 363. Tri-splanchnic nerves, 322; excito-nutrient properties of, 323 ; excito-secretory pro- perties of, 323 ; senso-motory properties, 322. Trbmmer's test for sugar in urine, 480. Tubercle, 278"; corpuscles, 72. Tube, definition of. 83 ; casts in urine, 480. Tubes, air, 84 ; effect of passingairthrouch, 434; blood, 84; bone, 88 ; dental, 86; elastic, experiments on, 552 ; nerve, 94; non-elastic, experiments on, 551^ dis- charge of fluids thpough, 119. Tubular elements of the tissues, 83. Tubuli seminiferi structure of, 379 ; u^ini- feri of kidney, 256. , Tiiffnell on embolisinj 244. Tulley on the microscope, 498. Tunica albuginea, 374, 379 ; granulosa of ovum, 375 ; Euyschiana of choroid, 340 ; vaginalis, formation of, 398. TurnbuU's blue injecting fluid, 523. Turpin on development iA pencillium in milk globules, 439. Tympanum, the, 349. Tyndall oii function of aqueous vapour, 128 ; researches on radiant heat of, 128. Tyrosin, chemistry of, 17 ; in urine, 485. Ulceration, 279. TJltimum morions, 214. Undulatory theory of heat, 123 ; of light, 134. Umbilical, cord, 398; sac, 386; vein, devel- opment of, 384 Upham's sphygmosphone, 217; d^tription of, 566. INDEX, 603 rachus, 397. ranic oxide in volumetric process for phosphoric acid, 469. rate of ammonia, as a sediment in urine> 486 ; as a deposit in alkaline urine, 487. ''rates, as sediments la urine, 486. Trate of lime as a sediment in urine, 486 ; of soda as a sediment in urine, 486, Trea, amount excreted, 275 ; chemistry of, 14 ; effects of exercise on excretion of, 259 ; tests for in urine, 472 ; Tolumetric process for, in urine; 472. Tredo segetum of diseased wheat, 438. Freters, development of, 396. Ire's, Dr, experiment on dead body with galvanic currenf, 144, Irethra development of, 898. Trie acid> amount excreted, 275 ; chemistry of , 1 3 ; derivatives, 13 ; Garrod's test for, 475 ; SchifPs test for, 475 ; test for in urine, 475 ; as a sediment in urine, 486. Jrinary concretions, 280 ; organs,' develop- ment of, 396. Jrine, abnormal constituents of, 478; acetic and butyric acids in, 485 ; cause of acidity of, 262 ; albumin in, estimar tlon of by weight, and tests for, 478, 479 ; alkaline, decomposition of, 460 ; alkaline decomposition, cause of, 262 ; allantoin in, 485 ; ammonia in, 471 ; apaount of, 256 ; analysis of the, 459; bacteria in, 488; bile iUf 484; blood in, 487; ofcarnivora, 258 ; chemical composition of, 257 ; chlorides in, 467 ; chylous, 484 ; clinical examination o^ 488 ; colouring matters of the, 34; creatin and creatinin 19, 476 ; deposits in, 486 ; in disease, 260 ; exercise, 259 ; fat in, 484 ; fermentation of, 459 ; food, effects of, on, 258 ; gases of, 488 ; of herbivorous animals, 258 ; hippuric acid tests for, 476 ; detection and estimation of inorganic constituents , of, 467 ; estimation of iron in, 471 ; kiestein in,. 484; lactic acid in, 485; leucin in, 485 ; mucus in, 487 ; ndour of, as affected by food or drugs, 459 ; or- ganic acids in, 477 ; detection and esti- mation of organic constituents in, 472 ; process for estimating amount of organic and inorganic matter in, 462 ; tests for phosphates in, 468 ; volumetric process for phosphoric acid, 468; pus in, 487; estimation of quantity of, 461 ; reaction of, 459 ; sarcinsB in, 488 ; season, 260 ; sediments in, 486 ; silicic acid in, 471 ; process for estimating amount of solid matter in, 461 ; determination of specific gravity of, 462 ; spermatozoids in, 488 ; sugar in, 479 ; tests for sugar in, 480 ; volumetric process for sugar in, 481 ; by saccharimeter, 483 ; sulphates in, test for, 467 ; sulphuretted hydrofren in, 485 ; torulffl in, 488 ; tube casts in, 488 ; tyrosin in, 485 ; tests for urea in, 472 ; volumetric process for urea in, 472 ; uric acid in, test for, 475 ; amount of water in, 462 ; Tibriones in, 488 ; xanthin in, 477. Frochrome chemistry of, 34. Urohsematin, chemistry of, 34. TTrorhodin of Heller, 34. Uroxanthin, chemistry of, 34. IJterine sinuses, 401. 'Dterus, development of, 397 ; changes In, following fecundation, 400, Utriculus in the ear, 316. Vacuoles of Huxley, 53. Vagina, development of, 397. Valentin on amount of blood, 241 ; knife of, 517 ; on rapidity of circulation, 2J9 ; on strength of extensor tendons, llO ; on static force of heart, 215 ; on weight of new-bom infant, 111 ; on amount of sweat, 265. Valeric acid, chem. of, 22. Vallisneria, movements in cells of, 38. Vapours, cause of, 126. Vauquelin on ash of hair, 269 ; on colour of hair, 268. Vas deferens, 380. Vasa, deferentia, development of, 397 ; efferentia of testis, 379; recta, struc- ture of, 379. Vascular layer, changes in, 385 ; layer of germinal membrane, 384. Vegetable electricity, 157 ; parasitic growths, 281 ; poisons affecting blood, 245. Veins, circulation in, 218; structure of, 218 ; valves in action of, 218. Velocity of circulation, 219 ; of efflux of fluids, 119 ; of light, 134 ; of i^erve cur- rent, 287; of sound, 129. Velum interpositum, development of, 391. Vena porta, development of, 394. Ventilation, 234. Venous blood, colour of, 231 ; gases of, 232 ; spectrum of, 32. Venous cu-culation, 218 ; effect of muscular contraction on, 219 ; effect of expiration and inspiration on, 219. Ventriloquism, 364. Ventral lamina, 384. / Vernois and Becquerel on analysis of milk, 405. Vermillion, use of, in Histology, 522. VertebrsB, primitive, 384. Verumontaniun, 397. Vesicles of the embryo, 385 ; functions of, 386. -Vesicula prostatica, development of, 397 ; , seminales, development of, 397 ; semi- nales, functions of, 380. Vestibiile in the ear, 346. Vibration of membranes, 133 ; of rods, 133 ; of strings, 133. Vibrio, development of, 423; movement. > of, 423 ; formation of, 47 ; in urine, "488- Vierordt on rapidity of blood, 219 ; heemas tachometer of, 219; hsematachometer, description of, 557 ; sphygmograph, 217 description of, 653. Villi, intestinal, description of, 205 ; function of, in absorption of the, 220 ; chorion, 400. ^ 16 6o4 INDEX, Yincent on tbe nricroscope, 498. Virchow's law of cell formation, 102 _; on connective tisEFiie, 79 ; on emboliHm, 244; leukhsemia, 209; leueocytotical fluid of, 209 ; on pus formation, 70. Vis a fronte in capillaries, 218. Yiscosity, influence of, on molecular for- mation, 37, 42. Vision, experimentg on, 662- Vital, law (Bennett's) of molecular coales- cence and disintegration, 45 ; proper- ties of the tissues, 176, Vitality, definition of, 184. Vitellus, 382. Vitreous humour, 340. Viviparous reproduction, 373. Vocal apparatus of Appunn, 678 ; of Hehn- holtz, by Appunn, 680. Vogel on colours of the urine, 460. Vo|;t on paralysis of taste, 334. Voice, cause of, 351 ; compass of, 133 ; development of organ of, 395; experi- ments on, 578 ; exercise of, in singing. 362 ; intonation of the htiman, 353 ; fal- setto notes of the, 352 ; in males and females, 352. Voit on biliary acids excreted by liver, 273; effects of exercise on excretion of urea, 259. Volition, phenomena of, 179, 300. Volkmann on rapidity of blood, 219; on position of objects ^ seen by the eye, 343 ; hsemadromometer of, 219 ; descrip- tion of, 557. VoIta*s, Alexander, researches in animal electricity, 162 ; pile, 162. Voltaic, batteries, 162 ; electricity, 161. Volumetric analysis; apparatus for, 465 ; method of, 464 ; mode M}f conducting process, 466; for phosphates in urine, 468 ; for sugar in urine, 481 ; for urea in lu^ne, 472. Vorticella, formation of, 47 ; spiral fibre in stalk of, 76. / Vowel sounds, formation of, 353, 680. W Wagner*s touch bodies, 335. Wa^er and Neef s hammer In induction apparatus, 527. ' Wallace on turgidity of dliary processes, 342. Walker on contraction of the pupil, 341. Walsh on the torpedo, 158. Warden on laryngoscope, 579. Wards of hospitals, amount of air required for, 235. Water, amount of, exhaled from lungs, 248 ; estimation of, in gastric juice, 454 ; as a constituent of the human body, 30 ; estimation of, in blood, 448. Waterhouse on the Gibbon, 419. Waters', Dr, on auscultation, 228 ; on structure of the lungs, 226. Watery vapour in respiration, 231. Watson, Sir Thomas, on cranial circula- tion, 220. Weber, on the functions of labyi'inth, 347 ; experiment on muscular coDtractility, 178 ; on rapidity of circulation, 219 ; on sensations of different temperatures, 336 ; and Valentine on touch, 336, Weight, absolute, relative, and specific, 110; ofindiridualorgans,112;of human body, 111. Wesley, John, journal of, referred to, 358. Weyrich on secretion of sweat, 266. Wheel of life, 344 ; of Foggendorff, descrip- tion of, 688. White of egg, 399. White, fibrous tissue, 76 ; chemical comr position of, 77 ; method of analysis of, 492 ; substance of Schwann, 94. Whytt on refiex actions, 311. Williams on increase of colourless cells, 208. Willis's classification of cerebro-spinal nerves, 316. Wiseman, Richard, on the royal touch, 359. Witbof on number of hairs, 268. Wittich, Von, on contractility, 81 ; on pig- ment cells of frog, 39. Woinow on the measurement of a hyper- metropic eye, 570. Wolfs Bolidescible nutritive fluid, 104. Wolff on cells, 52 ; on primordial kidneys, 396. Wolffian bodies, development of, 396. Wollaston on electro-magnetic rotation, 146 ; on lines in solar spectrum, 13S ; on muscular sounds^ 131.' Woman, duration of time of childbearlng, 378 ; time of puberty In, 377. Woorara, strength of solution of, to be u?ed in experiment on muscular contractility, 632 ; physiological effects of, 368. bright on Ancon sheep, 416. Wundt on electrotonua, 172. Xanthic oxide, chemistry .of, 16. Xanthin, preparation of, from urine, 477 ; as a product of disintegration of the tissues, 250. T Yellow eli^tic tissue, description of, 76 ; method of analysis of, 492. Yellow fever, temperature in, 247. , Yolk, 382; cleavage of the, 383; move- ments of molecules in, 39. Young on blood corpuscles, 64. Young, Thomas, principle of calculating time on a revolving cylinder, 545, Zona pectinata of cochlea, 347 ; pelluclda; of ovum, 376, 382. EEEATA. , Page 2, line IS from bottom, /or ". Ca N," reai C N^ „ 6, „ 18 from top, far " of the above series," read of the first of the above „ 6, „ 10, ,. 1*. .. 16, " i«> ,. 28, , ,. 28, ., 29, ,, 37, ., 63, ,. 64, ,, 74, „ 77, ^, 80, „ 81, „ 83, „ 90, ,,112, „m, ,,125, ,,131, ,,138, „ 146, „ 147, „ 147, „ 147, „ 152, „ 155. „ 158, „ 164, „ 172, „ 172, ., 172, „ 175, „ 178, „ 179, „ 182, , „ 183, „ 185, „ 186, „ 190, » 198, „ 193, „ 194, 11 from bottom, omit " free." 4 from bottom, for " Ptalyln," read Ptyalin. 15 from top, in formula for urea,^r " 02," read O. 1 at top, in formula for xantbin, /or " 0," read O2. 16 from bottom, in formula for oholio smld, for " H49," read H40. 3 from top,/or " latter," read former. 13 from bottom,/or " Ca M'\read Ca Pa. 10 from bottom, for" possible," read impossible. * 17 from bottom,/or " rises," read rise. 9 from top,/or "a)l," read cell. 2 from top,/or "but no fats," read and phospharetted fats. 5 from top, /or " renders," read render. 6 from bottom,/oi' " some," read semL 1 at top,/br " consists," read consist. 14 from top, omit " a," and /or"** body," read bodies. 21 from bottom,/or " have" and " exist," read has and exists. 21 from top, OTTtit " basic." 7 from bottom, /or " commences," read commence. 4 from top, /or ** consists," read consist. 19 from bottom,/or " straight," read sti-aight or curved. 14 from top, alter " gas," introdwx at zero C. 9 from bottom, after ** volume," introduce at zero C. 1 at bottom, /or 27, 27, read 24, 27. 15 from bottom, /or '* Fraunhofer," rea3 J^auenhofer. 14 from bottom,/(w " magnetic," read diamagnetic. 2 from top, for " inherent," rnotJ not inherent; and for "and evolved froD^ them," read hut developed in them. -^ 10 from top, after " is," introduce in. 25 from top,/or " intervals,'' read interval. 10 from bottom, /or " Zn SO4," read Cu SO4. 16 from bottom, for " form," read kind. 8 from top, /or " was," read were. 17 from bottom, /or "flg. 24," read fig. 34. 23 from top,/or " opened," read closed. 24 from top, /or " closed," read opened. 7 from bottom, /or " clos." read open. 17 from top, before "nerve," introdiuce the. 3 from bottom, /or -" are," read is. 17 from bottom,/or " sensations," read secretions, 7 from bottom, omit " gravity." 15 from top,/or " his," read its. 17 from bottom, /or " produce," read produces. , 12 from top, after "which," introdtiee its. ', 17 from bottom,/or " consists,"' read consist, , 1 at top,./br*'latter," read former. , 2 from top, /or " former," read latter. , 13 from top,/or "is," read are. 6o6 ERRATA. Page 199, line 6 from top,/or" action," read section. , 200, „ 16Jromtop,/or"afe,"»'codis. , 202, „ 9 from top, omit " of Peyer and," '"'[ ,215, „ 2 from bottom, /or "PQissieiiIle,"reorJPoisaeuille. ' ,216, „ 19 from top, /or "is increased," reai are increafied. , 219, „ 17 from top, for " Hsemadrometer," read Hsemadromometer. ^ I 224, „ 9 from top, /or "possess," read possesses. , 224, „ 2 from bottom,/or Plate IX.," read Plate XL , 227, „ 16 from top,/or " by," read of. , 233, „ 12fromtop,/or"selenurretted,"r«oif seleniuretted. ,234, „ 11 from top,/or "furiction,"-reaS functions. , 240, „ 4 from top, /or" some," reatf same. ,241, „ 17 from bottom,/or" liquid," rcatflinuids. , 242, „ 3 from topj after "these," introduce latter. ,247, „ 3 from bottom, /or "Helmholz," 'read Helmholtz. 249, „ 2Hromtop,/or "contain," reoi contains. 255, „ 10 andl2fromtop,/or "kilos," reodgrammes. 255, ,, 5 from bottom, /or "shew," reodshiews. • , 256, „ 22 from top, /or "cortiole," read cortical. 256, „ 8 from bottom, /or "uretors," read ureters. 268, „ 8 from bottom, /or " 32," read 62. 260, „ 7 from bottom, /or "anasarca," read anasarca. 262, „ 9, 12, and 13 from bottom, for " divided," reod derived. ■ .; 263, „ 6 from bottom, /or "chorium," read oorium. ' t)'& 273, „ 7 from top, /or "absorption or decomposition," reod decomposition^ itnd absorption. '? 273, „ 2 from bottom, /or "undergo,," read undergoes, J74, „ 4frnmbottom,/or "seven," read fifteen. 276, „ 6 from.top, after "to," introduce help to.. 318, „ 16 from bottom, after " convulsed," sn^oduce and the eye is turned - outwards. 318, „ 14 from bottom,/or "outwards," readinwards. 329, ,, 9frombottom, /or "Eckar," read Ecker. 338, „ 13 from top, for " opthalmotrope," read ophthalmotrope. . 342, „ 11 from bottom, for " opthajmometer," read ophthalmometer; 344, „ 22frombottom, /or Mrifhti" read left. 352, „ 10 from top, for " differ," read differs. 352, „ 8 from bottom, /or "precision to," read precision from. , 360, ,, 4 from top, /or " contain," read contains. 4 from bottom, for " preversions," read perversions. 361, 371,'sli6uld be 369. 380, line 13 from bottom, for " (Fig. 3, * to K)," read (Fig. 3,mn o). 380, „ 10 from bottom, /or " (Pig. 3, m to r), read (Fig 3, j) 5 and ft to W. 387, 389, 390, 394, 395, 395, 403, 462, 801, S49, 2 from top, for " vertebrae," read vertebra. 8 from bottom, after " circle" omit the. 10 from top, for " cerebral," read central. 17 from bottom, for " mesteric," read mesenteric. 9 from top, after " passing," introduce from. 14 from bottom, for " thryroid," read thyroid. 16 from bottom, for " tasselated," read tesselated., 9 and 10 from top, for " Guiacum," reod Guaiacum. 16 from bottom, for " acromatic," read achromatic, from top, Greek character is inverted. Description of Plate /. — Crystals. Fig. 1. ZTWc axAd,. Lozenge-shaped ciystals with obtuse angles rounded off (pp. 13, 14). Fig. 2. Prw; axi^. Dumb-bell crystals, and rectangular plates (pp. 13, 14). Fig. 3. UroiQ of Soda. Acicular crystals forming round masses. Seen in various stages of aggregation (p. 14). Fig. 4. Urate df Ammonia. Acicular crystals forming round masses. Seen in various stages of aggregation (p. 14). See aJso Fig. 18. h. Fig. 5. Hifjppwric add. Colourless prisms (p. 15). Fig. 6. Cystvn. Six sided plates (p. 16). Fig. 7. Tcmrin. Six sided prisms terminating in four or six sided pyramids (p. 16.) Fig. 8. Allanioin. Shining colourless prisms (p. 16). Fig. 9. Tyrosin. Stellate groups of long silky needles (p. 17). Fig. 10. Leudn. Balls^ composed of scales or needles. Usually of a yellowish colour (p. 17). ' Fig. 11. C^eaUn. Clear prisms, with pyramidal ends (p. 18.) Fig. 12. Creatinin. Prisms with rounded ends (p. 18). Fig. 13. (Molestr^. Soft nacreous lammse (p. 19). Fig. 14. Stea/rin. Soft nacreous laminse or needles (p. 20). Fig< 15. Ma/rga/rm. a. Fat cells containing star shaped masses of needles ; &. Star-like cluster of needles (p. 20). Fig. 16. iTWsite. Oblique prisms and tabular plates (p. 27). Fig. 17. Oxalate of Lime. a. Octahedral crystals ; &. Dumb bells (p. 23). Fig. 18. Tr'^le pTio^hate qf Ammonia and Magnesia. A. Large crystal of triple phosphate ; a. knife-rest crystal of triple phosphate ; 6. amorphous mass of urate of Ammonia ; c. Clift form of crystal of triple phosphate (p. 29). Fig. 19. JECcEmatin. Rectangular plates (p. 32). Fig. 20. ScBmatocrystallin or HcBmoglobin. Lozenge shaped crystals, colour dark red (p. 31). Fig. 21. HcBtnatoidine. Lozenge shaped thick crystals. This figure shews only the form ; they are of a dark red colour (p. 31). Fig. 22. Triangular blood crystals from a guinea-pig. This figure shews only the form. They are reddish coloured crystals (p. 31). F^. 23. Filamentous colouring matter of the bile (p. 32). Fig. 24. Melanin (p. 31). CRYSTAkS. Plate I 9 I .\ U " ii ■ftilr ^ 6 /r\Xa/ >&' O 10. s7i ^ C !?;$ i i II- "^ S 8 ♦^^ si I9\\_ . .T^/i ^^^ o ?2 "^S v.\l 1 li*^ ^ ~^ -t^ 24- /: 'i:^.f'S^ •^^>^^"^s. ^-n% Plate II. — Molecular Elements of the Tissues. Pig. 1. Yario-m arrain43mie,ntz of Molemles. a. Finely molecular mass ;&. Mole- cules varying in size as seen in milk ; c. Molecules aggregated in groups ; d. His- tolytic molecules from broken down fibrous tissue (pp. 36, 37). Fig, 2. J'a^JfoZecwZes precipitated from an alcoholic solution, and presenting the various forms here figured, shewing nucleolus, nucleus, and cell-mass, a, 6, c, — d shews two nuclei (p. 38). Fig, 3. Precipitation of Carbonate of Lime, from a viscous solution on a slide of glass, exhibiting molecular, nuclear, and cell forms in various stages of develop- ment, a. Oval body containing nucleus ; &. round body containing nucleus (p. 37). Fig. 4. The Cfrystallvne passing into the cell form, the former from a limpid and the latter from a viscous fluid : a. crystalline form ; h. angles of crystals rounded off ; c. ovoid cell forms ; d. cell forms aggregated together (p. 37). Fig. 5. A perfectly formed globular crystal of Carbonate of Lime, with radiating lines (p. 42). Fig. 6. A similar crystal disintegrating (p. 43). Fig. 7. Flattened crystals of Ca/rhonateof Lim>e, adhering at their edges, from the surface of lime water, resembling epithelium in form (p. 44). Fig. 8. Protagon. Processes shooting out from a mass of protagon on the addi- tion of water, stra^ht, curved, and spiral (p. 46). Fig. 9. Protagon. Occasional concentric layers formed at the extremity of these protagon processes (p. 4^. Fig. 10. Befoel&pment of "bacteria arid vibrios on the swrface of an infusion, a. Molecular or proligerous mass ; &. larger molecules, with their union together to form short bacteria ; c. still larger molecules and bacteria ; d. the same more separated ; e. aggregation of molecules lengthways or melting together of bacteria to form -mbrios ; /. chain-like molecular filaments— XfipioiAria; (pp. 46, 47," 48). Fig. 11. Globula/r dia^hanoiis bo&ies, caused by pressing epithelial cells in a viscous dropsical fluid (p. 44). Fig. 12. An AmcBba, a contractile molecular mass (p. 47). Figs, is, 14, 15, 16. Vital movements of pigment Molecules. Effects of diffusion and concentration of molecules in pigment cells in the skin of a frog ^p. 39-40), Figs. 17, 18, 19. Diagrams explanatory of Molecular Coalescence (pp. 41, 42). MOLECULAR ELEMENTS Plate II 1+ /vV ■■■*«*--^s ^ >•• .»>'' 16. &. V^dvuAot ^Soru£dm,FhaioJidt^ Plate III. — Cell Elements of the Tissues. Fig. 1. Chyla. A drop of fresh chyle, partly coagulated. On the left of the figure, the corpuscles, some resembling in form coloured corpuscles of blood, the true chyle corpuscles ; others those of the colourless, or lymph corpuscles. They float in a finely molecular fluid, the molecular basis of the chyle. On the right of the figure, the fibrillated coagulum, with the corpuscles entongled in it. These are globular in the centre of the coagulum, but flattened and fusiform-shaped to- wards the margin (p. 60). Fig. 2. Chyle. Effect of acetic acid on the fluid chyle ; chyle corpuscles rendered smaller and more opaque with thickened margins. The lym^h corpiiscles more transparent, with distinct nuclei (p. 60). Fig. 3. Blood. Fresh hiunan blood corpuscles. On the left of the figure,' isolated ; on the right, aggregated in the form of rotileavsc (p. 61). Fig. 4. Blood. Altered forms of human blood corpuscles, caused by slight evaporation of the fluid, or from adding dense and viscous solutions (p. 63). Fig. 5. Blood. Altered form and mode of aggregation of blood corpuscles when the blood is loaded with fibrin. See also Plate IV. fig. 2 (p. 63). Fig. 6. Blood. Blood corpuscles from different animals, a. From proteus ; b. salamander ; c. frog ; d. the same after the addition of acetic acid ; e. bird ; /. cameUdae ; p. fish ; and, h. crab (p. 61). Fig. 7. Blood. Appearance of human blood after the addition of magenta ^chloride of Rosaniline). a. (600 diameters) ; &. the same (2000 diameters), shew- ing that the dark molecules on the circumference are ciys^ls (p. 68). Fig. 8. Blood. Human blood corpuscles, after addition of solution of tannic acid (p. 63), Fig. 9. The same, followed by addition of tincture of iodine (600 diameters) (p. 63). Fig. 10. Blood. Human blood corpuscles from a case of cholera (p. 63). Fig. n. Blood. Human blood corpuscles disintegrating, from the fluid of a hsematocele (p. 63). Fig. 12. Blood. Blood corpuscles seen by direct light. The upper group are human, and the lower those of the frog (p. 61). Fig. 13. Blood. Blood corpuscles in leucocythffimia (p. 64). Fig. 14. The same after the addition of acetic acid (p. 64). Fig. 16. Mucus. Mucous corpuscles, from the fauces, F^. 16. Mvffus. The same after the addition of acetic acid, shewing the molecular fibres of mucin. See also Plate IV. fig. 1. Fig. 17- -f*M5 corpuscZes (p. 69). Fig. 18. The same after the addition of acetic acid (p. 69). Fig. 19. Pus corpuscles. From the fresh fluid of an abscess, surrounded by a hyalme membrane (p. 69). Fig. 20. Blood. Group of birds' blood corpuscles from the brain, surrounded by a fiyaline membrane (p. 69). Fig. 21. Blood. Group of human blood coi*puscles from an apoplectic clot, sur- rounded by a hyaline membrane (p. 64). Fig. 22. Gran/ule cells in masses from softened brain (p. 71). Fig. 23. Ctmcer. Different forms of cancer cells (p. 71). Fig. 84. l^ercle corpuscles from the lung (p. 72). Fig. 25. The same after the addition of acetic acid (p. 72). Fig. 26. Fat cells (p. 66). Fig. 27. Pigment cells, a.. From human lung; 6. from the skin of frog; c from choroid membrane (p. 67). Fig. 28. JTerve cells, varying greatly in' form. a. Oval, from gasserian ganglion ; &. globular, from the same ; c. oval, or round, from cerebellum ; d. bi-polar, from ganglion of posterior root of spinal nerve ; e. multi-polar, from spinal cord ; /. branched on one side, from grey matter of cerebellum ; g. triangular, from grey matter of cerebrum ; h. from sympathetic ganglion of frog, with spiral process, as figured by Beale Qp. 65). Fi^. 29. Artificial cells. Made by mixing protagon with fluids of different densities, a. Resembling pus cells ; b. finely granular cell, with molecular Brun- onian movements ; c nucleated cell ; d. cells resembling those of pus surrounded by a hyaline membrane : e. compoimd nucleated cell (p. 45). CELL ELEMENTS Plate III Plate IV. — Fibrous Elements of the Tissues. Fig. 1. Moleeulm jibres, with inteispersed nuclei in mucin (p. 73). Fig. 2. MoleaOar fibres in blood loaded with fibrin (p. 73). Pig. 3. Nudea/r, or elastic yellow fibres (p. 76). Fig. 4. Spiral elastic fibres winding round a bundle of white areolar tissue from the base ol the brain (p. 76). Pig. 5. Oell fibres formed by aggregation of fusiform cells (p. 76). Fig., 6. White areolm- fibres formed by splitting up of fibre cells (p. 77). Fig. 7. Bundle of the same after the addition of acetic acid (p. 77). Pig. 8. Diagrammatic view of the development of raucleor, or elastic tissue, u. Nucleus ; 6. cell ; e, nucleus elongating ; d. elongated and branched nuclei in neighbouring cells uniting; e e. nuclei in neighbouring cells, so uniting as to form the spiral (p. 76). Fig. 9. Development of wliite areolar tissue, a. fibre cell ; b. Fibre cell enlarging lengthways ; /. still further elongated, a so-called fusiform cell splitting at both ends ; d. a fibre cell splitting up at one end, and forming white areolar tissue (P, 76). Pig. 10. Sistoh/itcfiires—a. epidermic cell sphtting up with its nucleus ; b. epi dermic cell transformed into fibres, nucleus having disappeared (p. 78). Fig. 11. Molecular contractile fibres, from a recent infusion (p. 73). Pig. 12. I^uckar contractile fiiyre, with a rounded molecular head, as in Sperma- tozoid (p. 76). Fig. 13. Contractile cell-fibre, as in non-voluntary muscle (p. 77). Pig. 14. The same after the addition of acetic acid (p. 77). Fig. 15. Contractile fiHrres growing from epithelial ceUs— Cilia (p. 77). Pig. 16. A ciliated epithelial cell more highly magnified (p. 77). Fig. 17. VoUmtary iwusde. Voluntary muscular fasciculi, with transverse striae (p. 73). Fig. 18. Transverse section of volujitary muscle, shewing polygonal form of fasciculi (p. 73). Fig. 19. Voluntary muscular fasciculus splitting up transversely (p. 73). Fig. 20. Volimtary muscular fasciculus splitting up longitudinally (p. 73). Fig. 21. Voluntary muscular fasciculus after addition of acetic acid (p. 74). Fig. 22. Voluntary muscular fasciculus ruptured, shewing sarcolemma (p. 73). Fig. 23. Living voluntary muscular fasciculus after addition of acetic acid, shew- ing mode of contraction, with sarcolemma at the mai^n (p. 73). Pig. 24. Structure of voluntary muscular fibrillse (p. 74), Fig. 25. Ultimate fibrillse magnified 1200 diameters, shewing alternating light and dark spaces, a and 6, in different foci ^. 74). Fig. 26. Devdopment of muscular fibre im. the ewhyro, a. Nuclei embedded in a molecular blastema ; t. nuclei arranged in rows, with the external blastema dif- ferentiated ; c the nuclei separated, with further differentiated molecular blastema ; d. the transverse strise appearing in the molecular blastema outside and between the nuclei ; e. transverse striae fully crossing the fasciculus ; /. the fasci- culus perfectly formed (p. 75). Plate V, — Tubular Elements of the Tissues, Fig. 1. Blood-vessels. Structure of one of the minutest blood tubes or capillaries. Nuclei irregularly scattered (p. 84). Fig. 2. Blood-vessels. Structure of a small blood tube. a. Second or fenestrated membrane ; h. nuclei arranged transversely ; c. rounded nuclei (p. 84). Fig. 3. Blood-vessels. Third and fourth muscular layer in a still larger vessel. a. Third membrane with longitudinal nuclei ; &. fourth membrane with transverse nuclei ; c, external areolar or sixth layer ; d. transverse section of a nucleus — (p. 84). Fig. 4. Blood-vessels. Elastic coat or fifth membrane of a blood-vessel (p. 84). Fig. 5. Blood-vessel. Spiral arrangement of fusiform cells round a blood tube.— (p. 85.) Fig. 6. Bloodr-vessels. Third and fourth muscular layer in a vessel twice the diameter of the former one. (Fig. 3) i, f, t, Third membrane with longitudinal nuclei, its superior border ; 6. fourth membrane ; c. its transverse nuclei ; d. trans- verse section of one of these (p. 84). Fig. 7. Bevelopment of blood-vessels, a. Triangular cell uniting itself with the recently formed capillaries ; &. filiform cells aggregating together to form a vessel ; c. layera of cells forming the coats of a blood-vessel ; d. cell branching to form a vessel ; e and/, similar brancldng cells in recent exudation (pp. 85, 86). Fig. 8. Tooth. Longitudinal section of enamel, u. Enamel ; &. dentine (p. 87): Fi^. 9. Fodth. Transverse section of dental tubes (p. 86). Fig. 10. Tooih. Longitudinal section of dentine and crusta petrosa of tooth. Interglobular substance at the junction of crusta petrosa and dentine, a. dentine ; 6. crusta petrosa ^p. 86, 87). Fig. 11. Tooth. Transverse section of enamel (p. 87). Fig. 12. Transverse section of the grinder of a horse at the junction of crusta petrosa and enamel. The bone cells with their nuclei are seen melting into the crusta petrosa, the latter forming the lacunse (p. 87). Fig. 13. Structure of the nerve tvibes in the senso-motory nerves throughout the body generally, composed 1st, of the neurilemma of the nerve tube externally ; 2dly, the white substcmce of Schwanna; and, 3dly, in the centre, a viscous fluid which, when coagulated, constitutes the central axis (pp. 94, 96). Fig. 14. Nerve tubes from the spinal cord. These are of the same structtire, but possess varicositieSj and vary greatly in size (p. 95). Fig. l5. Nerve tubes from the spinal cord acted on by water. The white sub- stance of Schwann is coagulated and fibrillated, and the central fluid is now solid, and often projects beyond the lacerated white substance of Schwann (p. 95). Figs. 16, 17, 18. Similar but smaller nerve tvbes from the medulla oblongata and brain. EHg. 16. a. The neurilemma of the nerve tube is distinctly seen. Fig. 17- Varicose nerve 'tubes. Fig. 18 are the finest nerve tubes towards the circumference of the cerebrum. Fig. 17. a. Globules varying in size and shape, formed of the white substance of Schwann squeezed .out of the tube (pp. 95, 96). Fig. 19. Nerve fiibe after addition of sulphuric ether, shewing loose globules of oil inside, and of ether outside. Fig. 20. A nerve tvhe, at one end of which, a, the central fluid has been squeezed out, forming a coagulated mass with concentric circles, h. Transverse section of a nerve tube after steeping in chromic acid and a solution of carmine. There is seen the transverse section of the central rod or axis, siurounded by the concentric laminBe of the white substance of Schwann (pp. 95, 96). Fig. 21. Transverse section of wMtest^stomceofspim>al cord, shewing nerve tubes greatly varying in size, and each exhibiting the dark central axis of the nerve tube highly coloured, surrounded by the flbrillated white substance of Schwann (p. 95). Fig. 22. Transverse section of nerve iid)es, shewing portions of the tinted central axis dragged out by a blunt knife. Plate VL — Structure of Cartilage and Bone. Fig. 1. Cartilage. Section through the articular surface of a metatarsal bone, 100 diameters linear (p. 88). Fig. 2. Cartilage. Section of a cartilage of a rabbit's ear. 250 d. (p. 89). Fig. 3. Fibro-ca/rtilage. 250 d. (p. 89). Fig. 4. Diseased corJiZofl'e.— Fibrbufi degeneration of cartilage from diseased joinji. 250 d. (p. 89). Fig. 5. Diseased cartilage. Endogenous multiplication and bursting of cells in pulpy degeneration of articular cartilage. 250 d. (p. 89). Fig. 6. Bone. Vertical section of a long bone, shewing Haversian canals, and their anastomoses. 20 d. (p. 90). Fig 7. Bone. Tranverse section of a long bone. 250 d. (p. 90). Fig. 8. Bone. Vertical section of a long bone. 250 d. (p. 90). Fig. 9. Ca/rtUage cells, a, b, c, d, e, f. Fissiparous multiplication in articular surface of a long bone (p. 88) ; g h. Endogenous multiplication from a velvety or diseased cartilage of the femur. 400 d. (p. 89) Fig. 10. Various forms of lacimce and canalicuU in bone, a a. Simple irregular cavities from an ossification of the pleura ; b. from human bone ; c. a lacuna ■ next the Haversian canal, with most of its canaliculi towards the canal ; d. lacimse and canaliculi from the boa, also next the Haversian canal ; e. canaliculi without a lacuna.- 250 d. ; /. lacunse and canaliculi shewing their mode of anastomosis. 500 d. (p. 91). F^. 11. Ossification. Transverse section through a portion of foetal vertebral bone shewing commencement of ossification. 40 d. (pp. 93, 94). ■ F^. 12. Ossification. Vertical section through the epiphysis of the tibia of a new-bom kitten, i*. Cartilage cells arranged in rows ; B. cartilage cells shrunk- within their cavities ; c. cartilage cells still filling the cavities ; d. c. cartilage cells on the surface ; /. calcareous ridges between rows of cartilage cells, forming cancelli and Haversian canals. 250 d. (pp. 93, 94). Fi^. 13. Ossification, Vertical section through a foetal long bone shewing com- mencement of ossification, c*. cartilage ; 6. cartilage cells arranged in rows ; V. mineral matter deposited between them. 40 d. (pp. 93, 94). Fig. 14. Oss-^^ation. Transverse section throiigh ossifying cartilage of a calf, u.. Empty cartilage spaces ; b. shrunken cartilage cells breaking down ; c. trans- verse section of calcareous ridges. 250 d. (p. 93, 94). CARTILAGE AND BONE Plate t^ ■ * I 3lJ-^u~^^ si-ri — ii-i — X a f_f_ 9il_f.. .•-^,. Plate VIL — Molecular Theoty of Organisation^ as Illus- trated by Development of Ascaris Mystax, after Nelson, ISeeFhilosophical Trarisactions ofLondon^ vol. 142, 1852 (pp. 48-49, et seq.)}. ¥ig8, 1 to 4 Represent the histogenetic changes which take place among the molecules deposited in the ovarian tuhe of the female worm, until the fully maturated ovum (Fig. 4) passes into the oviduct. Fig. 5. Contact with, and entrance of, the spermatozoids into the ovum. This, the act of impregnation, is followed "by gradual solution of the spermatozoids, while the -germinal vesicle is still visible. Vig. 6. This also soon dissolves, and the interior of the ovum is now reduced to a; mass of histolytic molecules. Some spermatozoids still undissolved. rig. 7. Formation of a chorion externally— spermatozoids dissolved— germinal vesicle still visible. Fig. 8. Both spermatozoids and germinal vesicle fully dissolved. The histolytic molecules dense in the centre, but beginning to clear up at the circumference. Fi^. 9, 10 shew these molecules clearing up still further, when they meet together, concentrate themselves, and form histogenetic molecules. Figs. 10, 11 shew this process completed, and a membrane forming round them, another included cell is developed, as in Figs. 11 and 12. Fig. 12 shews the nucleus beginning to divide. Fig. 13. The cell now dividing into two. Fig. 14. The division complete. Fig. 15. Each Ibalf separated into other two. Figs. 16, 17, 18, 19, 20. The process of division is seen going on in these f^ures, until another histolytic mass of molecules is produced in Fig. 20. Fig. 21. This mass begins to clear up by coalescence of the molecules, which again become histogenetic. Fig. 22. They have now united together, and concentrated themselves, and begin to separate from the vitelline membrane. Fig. 23. A cup-shaped depression now appears, which, passing through the mass, forms a ring. Fig. 24. This ring is now seen to be divided at one place. Fig. 25. The two-endfe of the ring now elongate, and cross one another, and the molecules go on coalescing, to form the body of the worm. Figs. 26, 27. The worm now becomes spiral, and, on the bursting of the vitelline wall, Fig. 28. The perfect animal is extruded. MOLECULAR THEORY Plate VII I'late VIII. — I^/iysical I^rqperties of the Tissues. Figs. 1, 2. Diai^am shewing the centre of avity in a man with and without a burden I his'back (p. 107). Fig. 3. Diagram of a lever of the 1st order ; , resistance ; P, power ; Fulcrum in the ntre (p. 112). Fig. 4. Diagram of a lever of the 3d order : power ; R, resistance (p. 112). Fig. 5. Diagram of a lever of the 2d order ; power ; R, resistance (p. 112). Fig. 6. An example of the 2d order of lever the body, as seen in movemeuts of lower w In opening the mouth. Resistance is mporal muscle; Fulcrum Is the glenoid ivity in temporal bone ; Power is anterior slly of the digastric (p. 112). P^g. 7. An example of the 1st order of lever seen in the act of walking. Resistance is e ground; Fulcrum is the upper surface the astragalus ; and Power is the tendo- hiUes (p. 112). Fig. 8. An example of the 3d ordei^ of lever, see^ in flexion atihe elbow joint. Resist- Lce is the hand, with or without a weight ; ilcrum Is the trochlear surface of the hume- is ; and Power is the biceps inserted into ibercle of radius (p. 113). Fig. 9. Diagram illustrating Pascal's law the equality of fluid pressure (p. 114), Fig. 10. DiE^am shewing that the pressure a fluid on any portion of the inner surface a containing vessel is in proportion to its ipth beneath the surface (p. 114). Fig. 11. Diagram illustrating Torricelli's w that the velocity of the efflux of a fluid determined by the degree of pressure (p. ,9). Fig. 12, Capillarity. Bent glass tube con- ining mercury in equilibrium in the two nbs, shewing that the upper surfaces of the luid are convex, the tube not being wetted r the mercury (p. 116). Fig. 13. A similar tube containing water, le upper surfaces of the fluid concave, the ibe being wetted by the water (p. 116). Fig. 14. An endosmometer ; B, tube having membrane. A, tied over one end, and im- ersed in vessel C (p. 116). Fig. 15. Apparatus to illustrate the pheno- ena of diffusion through a blood-vessel ong which fluid is flowing (p. IIS). Fig. 16. Poisseulle's tube for experiments 9on the discharge of fluids through fine Lbes(p 119). Fig. 17. Arrangement of variously formed Lbes, A, B, C, D, £, and F, all communi- ,ting with the reservoir L U, to shew rdrostatic equilibrium (p. 115). Fig. 18. A barometer. A, tube ; B. C, stem containing mercury ; D D, level of ercury in tube ^. 121). Fig. 19. Dia^m shewing the ranges of the fferent varieties of the hiunan voice (p.l33) . Fig. 19^ A chromatic scale formed of semi- nes, shewing the sharps and flats of the itural notes (p> 133). Pig. 20. Diagram shewing reflection from a plane mirror. A B, plane of mirror ; E, eye of observer ; M N, object from which the pencils of rays, M D, M F, N G, H, proceed ; N M N, the object as seen in the mirror (p. 135). Fig. 21. Diagram shewing reflection from a convex mirror. A B, The surface of the mirror ; E, e^e of observer ; M N, object ; m «, object as seen behind the mirror reduced in size (p. 135). Fig. 22. Diagram shewing reflection from a concave mirror, A B, Surftice of the mirror ; M N, object ; m n, reflected image reduced in size, inverted, and hefore the mirror (p. 135). Fig. 23, Various forms of lenses : 1. double convex ; 2. plano-convex ; 3.' concavo- convex; r. double concave; 2^ plano-concave; 3^ concavo-concave (p. 137). Fig. 24. GrystaUof Iceland spar shewing double refraction. See description (p. 142). Fig. 25. Nichol's prism for throwing out one of the rays of polarised light (p. 142). Fig. 26. Arrangement to shew the refrangi- bility of light. E F, Shutter ; H, aperture in the same ; A B 0, prism of glass ; S, ray of light which, instead of proceeding in the direction of the dotted lines, is refracted so as to form the spectrum, M N, shewing the prismatic colours (p. 138). Fiff. 27. Diagram shewing that a magnet may DC regarded as composed of hypothetical molecules having southern and northern polarities (p. 145). Fig. 28. Arrangement to illustrate diamag-' netism (p. 146). Fig. 29. Arrangement to shew the produc- tion of a Current of voltaic electricity arising from the action of a fluid on one of two hetero- geneous metals. Z, zinc plate ; C, copper pl^ite. Arrows shew direction of the current (p. 150). Fig. 30. Arrangement to she w the prodilc. tion of an induced or Faradic current of elec- tricity, d. A bichromate of potash battery (p. 155). Fig. 31. Arrangement to shew the influence of an electric current on the m^:netic needle, NS(p. 148). Fig. 32. A gold leaf electroscope (p. 148). Fig. 38. Galvani's experiment (p. 162). Fig. 34. Experiment of Galvani, Aldmi, and Humboldt, shewing contractions in a pre- pared frog's leg, without the agency of metals or a metallic arc, simply by bringing the leg in contact with the lumbar nerves (p. 164), Fig. 35. Matteucci's pile of frogs' leg^ for the production of a current of electricity. A, Femur divided ; B, knee-joint (p. 166). Pig. 36. Diagrammatic view of Du-Boi6 Reymond's hypothetical peripolar electrical molecules of which he believes muscular fibre is composed (p. 167). Fig. 37. Diagrammatic view of Dr Rad- cliSe's hypothetical electrical cylinders com- posing muscular fibre, shewing a central nucleus or rod manifesting negative electri- city surroimded by a positively electrified covering (p. 167). Plate IX, — Function of Nutrition, Fig. 1. View of the nutritive system of a dog— modified from BtrtwrA. A. (Esophagus. B. Lungs. C. Vena cava. D. Liver, E. Stomach. F. Spleen. G. Receptaciilum chyli. H. Pancreas. I. Duodenupa. J. Entrance of biliary and hepatic duct. K. Jejunum. L. Ileimi, M. Caecum. N. Colon. 0. Rectum. P. KidneySj with the supra-renal capsules above. E. Urinary bladder. B. Thoracic duct, through which the chyle passes to join the blood. 1. Parotid gland. 2. Salivary gland of Nuck. 3. Submaxillary and other salivaxy glands. 4. Jugular and subclavian veins. 5. Situation ,of thymus and thjroid glands. 6. Entrance of the thoracic duct into the left subclavian vein, near the jugular. 7. Left auricle. 8. Right auricle. 9. Left ventricle. 10. Right ventricle. 11. Gall bladder. 12. Vena portse, which conveys blood from the intestines to the liver. 13. Mesenteric glands. 14. Lymphatic vessels. 15. Lacteal vessels. 16. Branches of the portal vein. 17. Ureters. Fig. 2. Structure of lobule of parotid gland with its duct. 20 diam. Fig. 3. Epithelial flattened cells, and globular salivary cells, and molecules in the saliva. 260 diam. Fig. 4. Action of acetic acid on two salivary cells. Fig. 6. Closed follicles covered with blood vessels in the tousU. 60 diam. {EMUher.') Fig. 6. Follicular gland from the root of the human tongue, containing closed follicles, a, a, epithelium ; &. surface of_follicular gland ; c. cavity of the gland ; d. follicle in the thick wall of the gland. 20 diam. (^oZZifcer.) F^. 7. Vertical section of a human circumvallate papilla. A. central papilla ; B B. circumvallate papilla ; C C. Depression, or fossa surrounding the central papilla ; a. epithelium ; &. &. nerves of the papilla ; c. secondary papilla. 10 diam. Fig. k. Fungiform papilla of the human tongue, w. epithelium ; p. secondary papilla. 10 diam. {EMliker,') a, b, v. elongated filiform papillse of the human tongue. 160 diam. (Todd and Bowman.) Fig. 9. Section of fungiform papilla, shewing distribution of : a. artery, and v. vein, forming capillary loops. 18 diam. {Todd and Bowmam.) Fig. 10. Mucous glands and ducts in the cesophagus. 25 diam. {Danders.) Plate X. — Digestion and Chylification. Fig. 1. Section of mucous membrane of the stomach, shewing above, a, follicular depressions, and below, b, the gastric follicles. 10 diam. (fVeric^.) Fig. 2. Follicular depression, with the opening of four follicles on surface of mucous membrane of the stomach. 200 diam. (fVericfts.) Figs. 8-7. The terminal or secreting end of gastric follicles, with the gastric cells in various stages of formation : (3) molecular contents ; (4 and 5) formation oi nuclei ; (6 and 7) formation of gastric cells. 200 diam. (JVericAs.) Fig. 8. Structure of a gastric follicle, cut obliquely, shewing aboye ; a. section oi cylindrical epithelium ; 6. seen from above. 250 diam. (TFosmoun.) Fig. 9. Isolated cells from gastric follicles. (JVcriicft*.) Fig. 10. A large Feyer's gland occasionally seen below the gastric follicles, 16 diam. (JVericAs.) Fig. 11. portion of the contents of the same, shewing molecules, nuclei, and cells. 200 diam. Fig. 12. Glands of Brunner below the villi in the duodenum. 20 diam. (^en'cAs.] Fig. 13. Glands of Peyer below villi of small intestine. 20 diam. (i^ericAs.) Fig. 14. Extremity of a villus shewing columnar epithelium, vessel^, and com' mencement of lacteal duct. a. fine lines at the external margin of epithelial cells. 400 diam. (Leydig.) Fig. 15. Villus of small intestine, the extremity and centre filled with fattj molecules during absorption. 200 diam. (Freri^:-li„ ^X-.\'&n.^t6TL.I7iatO'£iiho Plate XII. — Respiration and Secretion, Fig. 1. External stirCace of the lung, a. Air cells ; fi, &. borders of the smallest lobules. 30 diam. (£ar£^.) Fig. 2. Internal surface of section of lung, shewing air resides, a. Deep seated ; 6. towards the margin. 30 diam. {Bxisi^nol.) Fig. 3. Slightly oblique section of injected bird's lung. a. Spaces between con- tiguous lobulesj containing terroinal pulmonary arteries, and reins supplying the capillary plexus ; 6. lining membrane of bronchial tube ; c. blood-ressels, with large areolae, d, in bronchial membrane ; e. carity of bronchial tube ; /. very fine dense capillary plexus. 25 diam. (iZoijiei/.) Fig. 4. Thin section of pulmonary substance. ». Fibrous tissue ; 6, 6, &. cut air cells ; c. group of epithelial cells, from lining membrane of air cells ; (Z, d. capillary blood-ressels lining air vesicle below epithelial membrane. 260 diam. (defter.) Fig. 5. Two small pulmonary lobules, a, &, 6, &. Air cells ; c. terminal bron- chial twigs. 25 diam. {EMlik&r^ Fig. 6. Mode of termination of bronchial tubes in air vesicles of the lung, according to Wa>t&rz of Liverpool. Figs. 7-11. Diagrams of secreting glands. 7. ». Basement membrane ; t. epithelium ; c. blood-vessels ; g. straight follicle ; %. saccular follicle ; t. coiled tube : 8, fc. tubular crypt ; I. saccular crypt : 9. racemose or compound gland : 10. a lobule of the same enlarged ; n. lobule ; o. terminal duct : 11. compound tubular gland. (Shcvrp^.) Fig. 12. Fatty degeneration of muscle. 260 diam. Fig. 13. Group of hepatic cells. 250 diam. Figs. 14 and 15. Fatty degeneration of hepatic cells. 250 diam. Fig. 16. Waxy degeneration of hepatic cells. fii-i Respiration & secr etion. P^bteXII Plate XIII. — Excretion by Liver and Kidneys. Fig., 1. Transverse section of a lobule of the hiunan liver, in which the vessels have been fuiUy injected. 1. Intralobular or hepatic vein; 2. Its smaller branches, collecting blood from the capillary network ; 3. Interlobular or portal veina^ pass- ing into the lobule. 60 diam. (Sappey.) Fig. 2. Terminal bile duct. a. Small branch of interlobular hepatic duct ; b. . smallest biliary duct, communicating with others in which cells are seen. 216 diam. {Beale.) Fig. 3. Small fragment of a hepatic lobule, in which the smallest intercellular biliary ducts (a) were filled with colouring matter during life. 600 diam. (ChrzonszczewsJey. ) F^. 4. Two lobules of the liver, in which the bUiary ducts are represented as originating In a plexus towards their exterior. 20 diam. {Kiemem.) Fig. 5. Section of cortical substance of kidney, shewing Malpighian bodies, and their capsules, and the convoluted tubes. 20 diam. (Dickinson.) Fig. 6. Injected' portion of cortical and medullary structure of kidney. «-. ' Tubuliumiiferi ; b. their termination, by expanding over the^ Malpighian body; c, d. capillary plexus, 26 diam. (JEcker.) Fig. 7. Malpighian body, b. and its capsule, a ; c. bands of fibres between the tubes ; d. capillary vessels ; e. epithelium lining the tubes. 250 diam. (Ecker.) Fig. 8. Blood-vessels forming Malpighian body. a. Terminal renal artery ; c^. afferent branch, going to Malpighian body ; m, m. plexus of vessels forming Malpighian body ; ef. efferent branch, coming from Malpighian body, dividing into capillaries, &., which furnish the tubes. 50 diam. {BowTrum.) Fig. 9. Malpighian capsule and uriniferous tube. 6. Artery passing into Mal- pighian body ; d. capsule distended by injection, which fills the uriniferous tube in connection with it, c, 30 diam. (Botomcm.) Fig. 10. Uriniferous tube, lined with epithelial cells, in medullary portion of kidney. 250 diam. Fig. 11. Uriniferous tube in cortical substance of kidney, containing nuclei and molecular matter. 250 diam. Fig. 12. Commencing fatty degeneration of lu^aiferpus tube. 260 diam. Fig. 13. Advanced fatty degeneration of uriniferous tube. 260 diam. EXCRETION BY LIVER & KIDNEYS. • Plate XIII Plate XIV. — Excretion by the Skin. Fig. 1. Vertical section through the skin. a. Corium ; 6. epidermis ; c. sudori- parous glands ; d. hair sac ; e. straight ducts from sweat glands ; /, /. their open- ings on the surface of skin ; g. sebaceous glands. SO diam. {KolUher.) Fig. 2. Hair and hair sac. u. Hair shaft ; h. root of hair ; g. bulb of hair ; d. epidermis of hair ; e. inner root sheath ; /. outer root sheath ; g. structureless membrane of hair sac ; h. transverse and longitudinal fibrous layer ; ^. papilla of hair ; h. excretory ducts of the sebaceous glands ; j. its epithelium ; Z. cutis at aperture of hair sac ; m. lower or coloured portion of epidermis ; n. external layer -of epidermis ; 0. end of inner root sheath. 50 diam. {KolUkeF.) Fig. 3. Hair root and hair sac. a. External fibrous sac ; &. structureless mem^ brane ; c. the outer, and d. the inner root sheath ; e. junction of the outer sheath, c, with the hair bulb; /. external layer of hair;/*, transverse fibres; g. lower portion of the same ; h. cells of the hair root ; i. hair papilla ; ft. cells of medulla ; I. fibrous shaft ; m. medulla containmg air ; n, transverse section of medulla, and o. of the shaft. 300 diam. (JFrey.) Fig, 4. Section of skin of heel. a. External epidermic layer ; &. internal epi- dermic layer ; c. spiral tennination of sudoriparous duct ; d. position of papilla of cutis. 150 diam. (Leydig.) Fig. 5. Large sebaceous gland from skin of nose, opening into a hair follicle containing fatty matter. 50 diam. (Ecker.) ' Fig. 6. 'Longitudinal section through the middle of the naU and bed of the nail. lb. Free edge of proper subsfeince of the nail ; 6. external epidermis of finger ; c, internal epidermis ; d. bed of nail; e. follicle or root. 8 diam. ,Figs. 7-25. Structure of various kinds of hair. 7. Imbricated human bair ; 8, human hair with central medulla ; 9. and 10. sections of human hair ; 11. hair ol anindian monkey ; 12. hair of camel ; 13. hair of lemur ; 14. hair of an Indian bai —a. low, &. higher power; 15. hair of polar bear ; 16. wool^of sheep ; 17. hair ol lion ; 18. and 19. hair of kangaroo ; 20. and 21. hair of rabbit ; 22. hair of mouse 23. hair of armadillo ; 24. hair of musk deer ; 25. fibrous human hair. 100 diam Plate KV. — Nervous System, Fig. 1. Vertical section of grey matter of cerebral convolutions, shewing six alternate light and dark layers, a. External ligiht layer, with capillaries entering from the meninges, containing nuclei imbedded in molecular matter ; &. form of cells in deeper layers ; c, tubular white matter. 250 diam. Fig. 2. Vertical section of external grey matter in leaflet of cerebellum, u. Molecular layer, with large cells sending off branched processes ; &. granular layer ; c. tubular white matter. 250 dlam. Fig. 3. General appearance and attitude of pigeon after removal of cerebral lobes. {Dalion.') Fig. 4. General appearance and attitude of pigeon after removal of cerebellum. Fig. 5. Skull of Burke, a notorious murderer, executed in Edinburgh in 1828, with the supposed organ of destructiveness small. Fig. 6. Skull of Pepy, a noted pirate and murderer of the West Indian seas, with the smallest organ of destructiveness known. His skull was sent to the Edinburgh Anatomical Museum by Captain Graham, E.N., brother of the late Professor of Botany, wbo captured him. Fig. 7. Skull of Haggart, a noted thief in Edinburgh, who was hung for mur- dering his gaoler, with acquisitiveness and destructiveness small. Fig. 8. General type of Saxon skull. Fig. 9. Skull with great prominence of occipital bone. Fig. 10. Section of and internal view of the same, shewing thickening of bone and deep groove, in which was lodged the enlarged iorcuZar E.&ro^'MU. Pig. 11. Transverse section through middle of hxunan meduUa oblongata. 6, 6. Posterior pyramids, on each side of the posterior median fissure ; &, c. posterior column ; d, posterior part of antero-lateral colunm ; e. expanded extremity of posterior horn;/, di, cP-. fibres forming the decussation;/!, anterior horn; *. central grey substance behind the canal ; z. anterior median fissure. 6 diam. (Zodhhart Clarke.) Pig, 12. A. View of posterior surface of rahbit*s spinal cord, d, e. Two sections dividing posterior columns. B. Diagrammatic view, shewing the manner in which nerve fibres yf the spinal roots are distributed in the grey matter, a. FosteHor white colunm ; /. grey matter ; c. ganglion on posterior spinal root. NERVOUS SYSTEM, Plate F &. WaiK^vton d Fig. 1. Longitudinal section through the lumbar enlargement of the spin cord. a. Anterior column ; &. anterior roots of nerves ; c. mode of distributioi spreading out in all directions in grey matter^ like a brush ; d. decussation fibres in posterior white column. (Reduced from figure of Lockhart Clarke.) Fig. 2. Transverse section of spinal cord through the middle of the lumbi enlargement. A. Anterior column. F. Posterior column. L, Lateral colum a. Anterior median fissure ; p. posterior median fissure ; &, &, 6. anterior roots ■ spinal nerves; c. posterior root; /. spinal canal. The ganglionic cells are^t represented. (Reduced from figure of Lockhart Clarke.) Fig. 3. Roots of a spinal nerve, a. Structure of ganglion on posterior, or sei sorj, root ; 6. anterior, or motor, root. (Leydig.) Fig. 4. Vertical of the Schneiderian membrane of the olfactory region of a fo? B. Epithelium, a. Broad end of cells ; h. nucleated deeper layer ; c. deepef cell layer. D. Fibrous layer of Schneiderian membrane, d. Excretory duct froi e. glands of Bowman ; /. branches of olfactory nerve. E, Olfactory nerve. 10 diam. (Eckcr.) Fig. 5. Cylindrical epithelial cells from the olfactory region of a man. a. Epi thelial nucleated cell ; h. nerve cell, with straight process c ; d. internal brancb ng filaments of the epithelial cell. 350 diam. (Bcker.) Fig. 6. Vertical section of a small part of the retina. A. Entire section of a smal part of the retina. B. Two cones, represented separately in their connection wit! the fibres of Miiller and other structures. C. Two rods, represented separately ii their connection with the granules, fibres of Miillei*, and the nerve cells. ] Columnar layer— a. in A and C, the rods, in B, the terminal part of the cone ; I c ones : 2. Granular layer — o. outer layer of nuclei (striated corpuscles of Henle) d. inner layer of nuclei ; /. inter-nuclear layer : 3. Nervous layer— o". fine mole cular substance outside h, the nerve cells ; k. nerve fibres ; I. menArana Umitafts e. inner ends of the fibres of Miiller, resting on the limiting membrane. 351 diam. (KolUker.) , Fig. 7. Structure of crystalline lens. a. External layer of nucleated cells ; 6, fibres of human lens ; c. of ox ; d. of cod, 250 diam. (Todd and Bowman.) Fig. 8. Nerve from the finger, shewing Faccinian corpuscles, natural size. Fig. 9. Faccinian body from mesentery of cat. a. Nerve tube, terminating in fine filament, c, c ; b. concentric series of layers of fibrous tissue. 250 diam. (Ecker. Fig. 10. Touch-body of Wagner, treated by acetic acid. 250 diam. (Mckevi) Fig. 11. Muscular fasiculus, with^nerve entering its substance, and suppose) ganglionic nuclei. 300 diam. {Kuhne.) Fig. 12. Vertical section through the cornea. A. Anterior surface. «-. Con junctival epithelium ; 6. anterior elastic lamina ; c layers of cornea proper joine to anterior elastic lamina by crossed fibres ; d. posterior elastic lamina ; e. mem branch of Descemet. 80 diam. (Todd and Bowman.) Fig. 13. Soft lamina spiraUs of the cochlea. 1. View from above of the mem bra/na tectoria of Corti. 2. lAgamentum mem^rana tedoricB, immediately' beloi this. 3. Ha^enula sulcata. 4. Internal rods of Corti. 5. Auditory nerve, o, c Ligament of the cochlea ; &. Tia^enula sulcata ; c. its toothed free margin ; < parenchymatous cells between the Ugamentu/m menibrana tectoria and the men brana basilaris, m ; e. internal flat rods or staves of Corti ; /. oval groove through which pass fine nerves, l*i ; g. middle rods of Corti ; h. external squar( shaped extremity of the middle rods, g ; i. outer rods of Corti ; k. terminal gai glion cells of Corti ; I. bundles of cochlear nerves ; t^. minute nerves coming throug the grooves,/; m. position of memibrana basilaris ; n. zona pectinafa^ terminatin externally in the ligamemtwm membra/na bftsilaris, ^Reduced from figure of EcJar If late A VII. — Keproauctton, Fig. 1. Section of a testicle, a. Convoluted tv3Mli seminiferij 6, s. vasa recta; c,f. rt tig, in the cor^tts Mighmorianum; d. globus major; e. body of the epididymis ; g. glob nor; h. vas d^erens; ii. tunica albuginea. Fig. 2. View of a portion of one of the tvX>uU semdniferi, shewing molecular matter, ar Is ojf various sizes in which the spcrmatzoids are developed. (250 diam.) Fig. 3. Spermal^olds of various animals, a. Spermatzoids of man, viewed on the su ;e; i. the same viewed edgeways; c. the same with granule at summit of head ; d. tl ne edgeways ; e. dog ; /. mouse ig.mt; h. frog ; i. snake ; Tc. lizard ; I. spermatozoid coilc in cell; m. wild duck; n. shrike; o, finch; jp. Bombinatorigneus; 3. a magnified view < portion of the same ) r. perch; s. loach ; t. shark ; u. lamprey ; v. Helix (a snail) ; i maria ; x. a crab ; y. P'agurus (hermit crab) ; z. eai'thworm,. Fig. 4. Section of ,a portion of an ovary, a. Fibrous coat ; 6. a Graafian vesicle, shewin c the tunica granulosa; h. membrcma granulosa; d. zona pelhidda and yolk ; e. germini side ; /. germinal spot ; g. Graafian vesicles forming. In the middle of the figure, aafian vesicle is seen in a more advanced stage of development, and at the bottom w ^e one ^till farther advanced. These lie in a fibrous stroma, rigs. 5 and 6. Formation of ova by molecular aggregation. ilg. 7. A primitive Graafian vesicle, a, containing an ovum &. fig. 8. Section of the mucous membrane of the uterus, shewing at a, c, and d, a foetal tui )jecting into a uterine sinus : and at b, another sinus. rig. 9. Section of an ovary shewing in the centre a recent corpus Vut&wm, on the right hani older one, aiid on the left one still older, much reduced in size by contraction, rig. 10. The extremity of a placental villus, a. The external membrane of the villus,— tb ing membrane of the vascular system of the mother ; h. the external cells of the villus,- Is of the central portion of the placental decidua ; c, c. germinal centres of the externa Is ; d. the space between the maternal and foetal portions of the villus ; e. the interna mbrane of the vDlus, — the external membrane of.the Chorion ; /. the internal cells of th [us, the cells of the chonon; g. the loop of umbilical vessels, i'ig. 11. A placental villus. rig. 12. An ovum from the bitcb freed from the granular membrane, shewing the darl emal yolk, and clear external zona pelVoGida. (50 diam.) rig. 13. The sa.me ovum lacerated with a needle. The yolk has flowed out, shewing th 'minal vesicle, a, with its germinal spot. (50 diam.) I'ig. li. The ovum has encountered spermatzoids, which are seen adherent to the zom liwida. Fecundation has taken place ; the spermatzoid, which has penetrated the trane •ent zone, together with the germinal vesicle, has been dissolved m the yolk, which i ided into two masses. (50 diam,) i'ig. 15. The yolk divided into four masses. (50 diam.) 'igs. 18 and 19. The process of division in the yolk fuither illustrated. (50 diam.) 'ig. 20. The yolk nowreducedbydivision to alargenumberof molecular cells. (50diam. ^ig, 21. The molecular cells rendered visible by laceration of the ovum. They contain 1 ar space in their centres. (50 dia/m.) I'ig. 17. An ovum further developed after it has been placed in water for a short time consequence of endosmose, the internal membrane is separated from the zona pellucida I is seen to be formed by the cells which have coalesced. This is the germinal membran< ih' the germinal area composed of an extra layer of cells. (50 diam.), 'ig. 16. An ovum much larger, taken' from the uterus, moistened with water. Th minal ihembrane is somewhat separated from the zona pelhtcida, and thrown into foldi diam.) ^ig. 22. Portion of the germinal membrane surrounding the genninal area, cut out fror iurther developed ovum. A clear space in the area called Off-ea pelhMida is apparent diam.) 'ig. 23. A similar piece from a somewhat older ovum. The germinal area has becomi A. (10 diam.) Ig. 24. The germinal area is now greatly enlarged in the germinal membrane; a. gennina mbrane; b. limit of vascular area; c. area pnAlMCida; d. lamincB dorsales; $. Primitiv ove. REPRODUCTION. PlateXYII ■1. Wa/^r-^toTtJi-'^on.S^Ti.^aUiJirPio rounded by the serous membrane. The lower portion of the embryo is covered wi vascular and mucous layers. (5 diam.) Fig. 9. Diagram representing the mode of formation and position of the three emb: sacs, a, Embryo— 6, amnios — c, umbilical vesicle — d, the vitelline duct, or pedicle umbilical vcsicle~e, allantois— /, the urachus or pedicle of the allantois, afterwari t urinary bladder. Fig 11. The lower end of an embryo some hours older than that in Fig. 8. The n and vascular layers are drawn upwards, so that not only is the visceral cavity seen, h lower portion of the intestinal canal, a. At the lower portion of the embryo are two swellings, &, &, the commencement of the allantois. (10 diam.) Fig. 12. The lower end of an embiyo twelve hours older ,than the last. The allanto forms a sac,' the two halves of which, however, are not yet closed. (10 diam.) Fig. 10. The embryo of an ovum twelve hours older than the last, suspended by tl cular and mucous layers. All the different parts formerly referi'ed to may be seen f developed. The superior extremity is prominent. In the visceral cavity two long st bodies are seen, the Wolffian bodies ; and the allantois is now so enlarged as to hang the visceral cavity, covered with a network of vessels in connection with the vascular (5 diam.) Fig. 14. The head of the same embryo, a, Anterior brain-cells— &, eyes— c, second cell— d, first, visceral arch— e, process thereof—/, three lower visceral arches— ff/righ ft, left auricle— i, left, and 7c, right ventricle— 2, aorta, with aortic branches to the y arches. (10 diam.) Fig 13. An embryo older than that represented in Fig. 14, seen in front, a, Nasa tures— &, eyes-rC, first visceral arch, now the under jaw— id, second visceral arch— e, and/, left auricle— (?, right, ajid h, left ventricle— i, aorta— fc, liver ; between its two 1 seen the cut vena ompTudo-mesenterica — I, stomach — m, intestinal canal, terminating; umbilical vesicle — n, o, Wolffian bodies— j?, allantois— g, upper, and r, under extremii diam.) ' Fig. 15. Embryo of an egg about four weeks old. a, Trachea and 03sophagus— 6, t gland— c, right, and d, left auricle— e, right, aud/, left ventricle— c, left, and h, righ1 — i, i, i, three lobes of the liver— fc,, stomach—/, intestinal coils, which by a band, former ductits omphalo-mesentei'icm% are in cpnnection with the umbilical vesicle Wolffian bodies. (5 diam.) Plate XVIII, — Reproduction. Pig. 1. Portion of gemjinal membrane, with the embryo from an ovum twenty-four h older than Fig. 24, Plate XVII. The primitive groove is not yet closed, hut is much stroi especially above. Here three swellinga are observable, which are the three primitive bi cells. At the inferior end, the groove is of a lancet shape (jinus rhornboidoMs). In the c( of the groove is a thin streak, the commencement of the i^kmda dorsalis. Six square are formed on each side, the commencement of the vertebral column. The germinal n hrane is now composed distinctly of two layers, the : upper of which (the seroiis or an layer) is out close round the embryo, shewing more distinctly the lower (the mitcoi vegetative layef). (10 diam.) Fig. 2. The same embryo, seen sideways, whereby the elevation of the dorsal laminae, the groove between them, are better seen. The head is already distinctly elevated abov germinal membrane. (10 diam.') Fig. 3. An embiyo twelve hours older than the former one, turned round and examine the under or abdominal surface. The head with the broadened-out firat brain-cell is coming forward. Inunediately below this an S-shaped tube is seen, which is the rudimei heart. The lower end branches o£E on eaoh side to join the vascular network, forming vena omiphalo-'mesentericaB. The visceral or abdominal cavity is seen open below, causini embryo to resemble somewhat the appearance of a partly-decked boat. (10 dima.) Fig. 4. The same embryo seen from above. The primitive groove is now for the most closed over. The first hraiu-cell is widened out laterally, and bent forwards. The post ones are altered in shape from absorption of fluid. There are two vertebral cells. At ends of the primitive groove folds of the serous layer are visible — the commencement ol amnios. The serous layer is cut qIqsq round the embryo ; and upon the mucous layer, lines, in the form of a network, are visible— the commencement of the vascular layer, diam.) , Fig. 5. An embryo from an ovum supposed to be twenty-three or twenty-four days seen from above. The primitive groove is now completely closed, to form the medu tube, and exhibits above the three primitive brain-cells. The first of these Is seen to 1 expanded laterally as to form at each side the embryo eyes. The embryo ears are also at each side opposite the third brain-cell. The upper and lower ends of the embr^'o are Inclosed in a backward fold of the serous layer, which, however, is still open In the ce; The blood vessels in the vascular layer are now fully formed. (10 diatn.) Fig. 6. The same embryo seen from below. The head is strongly bent forward, so tha first brain-cell and embryo eyes are best seen on this surface. Below these, two not processes are seen, which are the first visceral arches. Below these again, the S-sh heart— terminating, above in the aorta, below in the ven(R ojn^tialo-TnesentericcB. The 1 now pulsates, and a circulation is established oter the vascular area. (10 diam.) Fig. 7- An entire ovum, with the embryo somewhat older than the last. The vi chorion is raised off the entire centre of the e^, which is suspended by it at one point, w the folds of the serous layer have completely closed over the back to form the amnios, embryo lies with its Interior half in the plane of the vascular and mucous layers ; whils head and superior half is prominent, and inclosed by them. At the sides are seen botl artericB axid vence omphalo-mesenterica, wTiich. communicate with the plexus of thevas< layer, and terminate in circular rings, the vencs termmaJes, leaving the two poles of theo bare. (5 diam.) Fig. 8. The same embryo, removed with its membranes, and viewed from the internal face of the ovum, sideways. The head and upper portion is seen surrounded by the ami In the head is observable the brain, divided into anterior, neighbouring, and middle bi a, &, c / the third brain-cell, d ; eyes, e ; ears,/; not yet connected with the third b: cell. There are three visceral arches. The heart is further developed, prominent, and REPRODUCTION. Plate- Ml (?. /K,./,/,,/,... (■ ■;., A-'/'/ .f'ifito-l-rh pillars ; c. transverse bar connecting d d at the top. j. Bar bearing underneath tl electro-magnets/. These may be elevated or depressed on d (2 by the screws n n. O. connecting two Sraee*s elements with electro-magnet. Fig. 9. Heidenhain's tetanometer. K. Upright brass pillar, having an attachment and hearing the lever A, li, S"j, ». a. Fulcrum of the lever ; S".^". two screws by mi which lever niay he lei^hened or shortened. L. Armature for the electro-magnf underneath, S' V. C. Upright brass pillar bearing at top a horizontal arm, at end of there is a screw S', the point of which touches a bit of platinimi on the upper surface lever. Sj,/, Attachment screw. S,,. Attachment screw. S,„ and S/„ are connectei wire in the vulcanite stand not shewn. Z. Short brass pillar having a binding screw current is broken by pushing hack the handle seen on the right, and thus elevating th arm &. S. Spiral Spring, worked by screw S underneath for restraining the action lever. A. On left end of the instrument is the apparatus for beating the nerve, h. ivory hammer, at end of lever ; h'. ivory groove in which hammer head k beats, t > ^ passing transversely for nerve A. m. Small roller for attaching the end of the nerv Steel spring for retaining roller m in position. S,„/. Screw by which the apparatus may be elevated or depressed. Fig. 10. Arrangement of apparatus for demonstrating the presence of a current of city in the living body. The individual is grasping a wooden roller, having the index immersed In the troughs. On his right hand the galvanometer is seen. Fig. 11. The rheocord. S W. Platinum wire. S' W,. Another platinum wire. I a bridge over which the wires pass at a", tr. Z. Piece of brass carrying two bottles fiUe mercury A, capable of sliding along the platinum wires S W, and S' W,. 0. 1000, Scale ated into niillimetres.^ P S. 1, 2, 3, 4, 5, and 6, Kectangular pieces of brass, which ] connected by brass stoppers, or pegs. P and Q. Short brass pillars, each hearing two ment screws for wires a a. The dotted lines, marked on the right hand thus : >X, , I 'c, and I &, and passing round small ivory pulleys, rdt)resent German silver wires, e ing the pieces of brass, 1, 2, 3, 4, 5, and 6, when the stoppers are removed. Plate XIX. — Practical Physiology. Fig. 1. Du Bois-Reymond's induction-apparatus. R 1. Primary coil ; E 2. secon coil ; the upper B is the groove in which the secondary coil slides. B B. "Wooden stand Scale graduated into millimetres. 6. Electro-magnetic apparatus for attracting W hammer, k. Screw for attaching wire from positive pole. Z. Screw for wire in connei with negative pole, fe^ %„. Attaclmients for a wire when Helmholtz's modification is ployed (see Fig. 2 |8). S'. Screw, the point of which establishes a connection with the of the spring. Fig. 2. The end of Ihi Bois-Reymond's apparatus, shewing on the right hand a diag; matic view of the primary and secondary coUs. o. Screw for attaching the wire /3 passin %„y as used in Helmholtz's modification. 6. End of the primary coil. S. Screw i which touches the under surface of the spring, and is placed on the top of the middle pi in the base of which there is an attaching screw, x. S,, Screw, the point of which touche: back of the spring when the apparatus is used in the ordinary way. S^,. Attachment si for the wire passing in the direction of the arrow to Ri, the primary coil. The lower ai indicates the wire passing to the ma^eto-electJ'ic apparatus Rs, secondary coil. h. battery. Fig, 3. The limb of a frog skinned, a. The muscles of the leg ; 6. the sciatic nerve. Fig. 4. Multiplying galvanometer, a. Base ; 6. brass box ; C. boxwood frame carr coils of wire ; //. wires leading to galvanometer; g. screw for rotating &. ft, A. Verticall bars supporting a horizontal bar, from the centre of which the astatic needle is suspende a single silk fibre. «', Screw for raising or lowering the needle. , Fig. 5. Non-polarizable electrode of Du Bois-Reymond. a S. Amalgamated zinc troi c, attachment screws for wires, e. A rectangular piece of vulcanite for maintaining cushion of blotting paper in position ; o- film of moist clay laid on the cushion so as to tect the muscle from the irritant action of the solution of sulphate of zinc. Fig. 6. Folarizable electrodes of Du Bois-Reymond. u. "Wooden stand ; h. round pie( vujpanite with screws ; c. universal jcHnt ; d. binding screws ; h. square block of ivory wires, e, passing through it ; /. the n6rve lying on the triangular platinum electrodes troughs containing cushions of blotting paper immersed in solution of sulphate of zinc. Fig. 7. Muscle tel^^ph. A. Forceps holding the femur ; B. handle of forceps, bearii its end the screw S. The forceps may be elongated or shortened by drawing them out oJ socket, secured by S. S. Screw for attaching wire a from positive pole of the batter? hook fixed to tendo AchilUs, and having a wire, x, In connection with negative pole atta< to it. a a' thread passing from h over the pulley p" p and supporting the bucket b ; round counterpoise-weight attached to the end of the long arm above ^Z, bearing the dis which moves in the direction of the arrow. Z. Screw for fixing in the socket the upi pillar of brass bearing the telegraph, g' q'. The stand of the whole instrument. Fig. 8. Pfliiger's falling apparatus or trip hammer. E I. Wooden stand ; d d. upri bearing the axle e, on which the huidle U of the hanuner i h moves, i. Head of the hami m. steel point attached to side of the hammer-head, for dipping when the hammer i into the trough X. a' b' Z. Steel catch for holding securely the handle of the hammer v the head falls, y. Screw for attachment of wire in connection with negative pole on same piece of brass as supports the trough x. c. Screw for wire from positive pol battery. P. Lever working between two uprights, P, one end of the lever being seen (following the dotted line), and the other at q. r. Screw point which, when hammer hei elevated, is touched by the end of the lever, but is separated from it when the head 'i t. Screw for attachment of wire from positive pole ; w. screw for the wire in connec with negative pole. The closing shock is given by the current passing in the direc c, d, e. A, m, X, y; while that of the opening shock passes thus : t^ V '''s '*■ Above hammer head s the magneto-electric apparatus A for supporting it, d d. Two brass upr PRACTICAL PHYSIOLOGY. Plate XIX trbUed by a spring, d, which may be tightened or relaxed, e. Fixed weight actini counter-poise to c. /. End of the'rectangular arm seen at n'^ Fig. 1, and A, Fig. 3. The to the right shews the direction in which the box revolves. Fig. 3. Diagram shewing the arrangement of apparatus for determining the rapic the nerve-current, a. Fdrceps holding /emur; &. gastrocnemitts muscle ; c. sciatic ner revolving cylinder; e. lever cariying the stylette;/- centrifugal apparatus; g. steel i forming the bridge between the two pillars Jc i; h. end of out-springer, and above it tl of the rectangular arm ; A:, wire passing from primary coil m to one side or pier of the 1 in .the myographion ; i. wire from the other pier back to the battery I ; i. the batter primary coil of induction machine ; n. secondary coil ; n" n". Pohl's Commutator, ha^ p3, 4 wires going to stimulate a portion of the nerve c, close to the muscle at r, and at wires passing to q, so as to stimulate at a distance from the muscle. The primary cir< in the direction I, m, k, g^ i, back to I. When this is broken at a, an induced current i from n eittier to r or g, on the nerve c, according as we place the Commutator. Fig. 4. Du Bois-Reymond's key. B. Vulcanite plate. 6, c Rectangular pieces of each bearing two screws. These may be connected by means of the handle d. Fig. 5. Pfliiger's Myographion. S. Wooden stand, p. Frame having a groove in whi glass plate P moves. F. Brass pillar bearing a square glass chamber for the muscle. L ceps for the femur, to which is attached the gastroeneTnius muscle A with the sciatic nei a. Brass pillars bearing at the top the double lever 6 ; c. swivel apparatus for connectii lever b with d, a long hook attached above to the tendo AchiUis ; g. a scale for a weight cient to draw down the lever after it has been elevated by the contraction of the muscl movable weight for carefully balancing the lever. Fig. 6. Fohl's Commutator, a. A round wooden disc, having six small holes filled raercuiy, each having a screw for the attachment of a wire ; + a. wire coming from pc pole of battery ; — 6. wire going to negative pole ; P 0. two pieces of wire permanentlj at one end into + a, and — &, and the other ends held in close proximity by a glass tt q, r, and m, n. transverse ar<..ft>r, .f'Sf,i..£S''..J^ato-li^?io Figs. 18 and 19. Volkmann's hsBaiadrombmeter for measuring the rapidity of the c tion of the blood, a b. Nozzles for insertion into the artery ; c c. tubes connected stop cock', so that the current may be caused to flow from a to &, as seen in Fig. 18 oi the U-tube d e, as seen in Fig. 19. In Fig. 18 the limb e of the U-tiibe is provided ■ scale, hut in most Instruments the scale passes along the whole length of the U-tube. Fig. 20. The essential part of Yierordt's hsematachometer, for measuring the rapii the circulation. A 6. Square metallic box, two sides being made of glass ; a b. nozs insertion into the artery ; c. a pendulum hanging in the box, near the point of entri the blood at a ; (2. a graduated arc for measuring the deviations from the perpendici the pendulum ; e. the pendulum as moved by a stream of blood through the box. Fig. 21. The kymographion of Ludwig, for measuring blood pressure, and also for n ing the time occupied by pulsations, a, d, e. A U~tube containing mercury, ^he li which, in the two limbs, is seen at d and e. L », m, a. A tube filled with a solul carbonate of soda, the part Z, n, m, a, being made of lead, while a d is glass. At m c accurately fitting screw-collar for uniting the two tubes ; n. an air hole in the leade provided with a stopper ; I. a connecting screw-collar between the part of the apparal which is made of brass and the leaden pipe ; o. a stop cock ; g. a, T-shaped nozzle for ins into the artery. At c and e are graduated scales opposite each limb of the U-tu measuring blood pressure in inches of.mercury. The apparatus as described to this p the hsBmadynamometer of FoisseuiUe. The apparatus for registering the oscillations mercury is now added. /. A glass float on the surface of the mercury bearing a thin v rod g ; b. a. screw-collar ; h h. two uprights, having thin wires, on which the transvei bearing the stylette i moves freely up and down in the same vertical plane ; k. a weight acts as a counterpoise to the float and stylette ; r. is the square wooden stand of the i ment. To the left of 21 is seen a revolving cylinder, 6, moving on an axle, a c, and ha stylette, d, in contact with it. Fig. 21*. A T-shaped nozzle for insertion into an artery by the ends a 6, the tube necting it with the end of the leaden pipe 2 n m, in Fig. 21. Fig. 22. The anapnograph of Bergeon and Kastus, for measuring the amount of inspiration and expiration, and for obtaining a tracing of the movements of respiratio India rubber jiozzle ; T. india rubber tube ; V. aluminium valve ; H. wooden lever ; t c. Tracing obtained on the paper. N .M. Box containing clock-work ; B. button for ti ing or relaxing the lever H; C. diagramatic view of interior of box, shewing 3, aluminium plate and lever. The dotted line, 4, shews movement of the lever in inspi; Fig. 23. The ophthalmotrope of Reute. a, b. Models Of eye-halls ; c, d. brass plates tl which cords pass representing the muscles of the eyes ; e. cords passing downwards oi brass plates /, /. The back of one of these plates /, /, graduated, is seen at A. g. pillar supporting the apparatus ; h. wooden box, having in its interior a transverse r( which the cords e, are attached ; i, k. levelling screws. Fig. 2L The ophthalmometer of Helmholtz. a, d, b, b. brass box containing two of glass, 6, 6, which may be; revolved by the pinion a^c; d,. screw-head for movi pinion. At c, is a portion of the telescope. The whole appai-atus is mounted on a having a universal joint. 24,/. A view from above of a circular brass plate (seen in I in the upper part of the box, in a line with a), toothed at the edge, for revolving th plates by means of pinions. Fig. 24o. Diagrammatic view of the reflections of a candle flatne seen in the hums as adjusted for distant objects. 1. Cornea, erect ; 2. anterior surface of lens, er posterior surface of lens, inverted. Fig 246. The same as adjusted for near objects. The anterior surface of the It become more convex, as 2 is seen nearer to 1 than in 24o. Fig. 25. Miiller's apparatus for shewing the productioij, of voice, a. Forceps fo pressing the thyroid cartilage, so as to approximate the cords ; b. movable handle forceps ; c. cord passing from a hook attached to the, upper margin of the thyroid ca: in the mesial line, over a small pulley ; d. scale or balance, at the end of c. By ; weights in d, the tension of the vocal cords may be increased at pleasure. A B. Woodei supporting the forceps and pulley. Fig. 26. A stand, i h, on which there is a pillar, g A, bearing two of Mohr's buretteSj may be elevated or depressed by the split tubes mm; a, &, and c, d. glass burettes, gra in millimetres ; /, .e. Mohr's clips for compressing the short pieces of india-rubber t I, glass beaker placed under a,b. Plate XXI. — Practical Physiology, Fig. 1. Section of a compound achromatic microscope, a. Eye of observer ; 6. e3e-g c c. stop in the eye-piece ; d. field gla^s. The letters, &, c c, and d, represent the eye-i: e,/, and ff, the objective, conBisting of three achromatic lenses. The arrow, x^ y, bei the objective is seen magnified and inverted and curved at y x. Fig. 5. Diagram to illustrate chromatic aberration, x y. A bi-convex lens ; &. an light passing directly through xy ; ab. two rays of light dispersed by x y, so that the "v rays come to a focus at A;and the red at T. L L. a screen placed mid-way between A ai Fig. S". Yiew of three achromatic lenses ; ahcis the angle of aperture of the lenses. Fig. 3. Diagram to illustrate the theory of enlargement, x y. A-bi-convex, lens thr which rays of light pass to the eye from the small object a b, and which so refracts ' that they enter the eye at such an angle as if they came from a large object a' b\ a 6 sequently appears magnified to the size a' b'. Fig. 4. Diagram to illustrate spherical aberration, shewing the rays a c impinging o: Burface of the lens near the margin brought to a focus at A, while those passing throng] centre b, not being so much refracted, meet farther off, at B. Fig. 2. Boss* compound achromatic microscope with movable stage and Gillett's conde A. Body of microscope. B. Rectangular arm supporting it. D. Coarse adjustment Fine adjustment. M. Mirror, concave on one side, plane on the' other. G. Gillett's denser fitted beneath the stage. K S. Bull's-eye condensers for reflecting light on oj objects. 7 is opposite the strong brass pillars supporting the microscope. Fig. 6. Section of a compound objective of Ross, shewing three .achromatic lenses the arrangement for correcting the lenses for use with covered and uncovered objects Tube carrying the two upper lenses ; A A. a cylinder carrying the lower lens ; C O. scr ring for approximating A A to B. Fig. 8. Oberhauser's microscope, a. Eye-piece ; &. body ; c. split tube ; d. objectiv inirror ; /. fine adjustment ;• g. condenser. Fig. 9. Nachet's pocket microscope, a. Eye-piece; &. bodyj c. fine adjustment; d, for containing the microscope and lenses, &c., and on the under surface of the inv lid the microscope is fixed, as shewn in the figure ; e. mirror. Fig. 10. The same instrument seen closed, d. A small button for moving the mirror Fig. 11. Stirling's section cutting apparatus. A. View from the side. B. View o top. a. Screw for fixing apparatus to a table ; b. socket in which the fine threaded sc ' works, pushing up the bottom of the circular box d. Fig. 12. Valentine's knife, a, &. Blades ; c. screw for fixing the distance betweei blades ; d. steel catch for holding blades together at the joint e. Fig. 13. Sphygmograpb of Marey affixed to the left wrist. The names describe the of the apparatus. The arrows shew the direction in which the card moves by clock-^ a. The upright rod in connection with the spring resting on the artery. Fig. 14. Diagram of the essential parts of the sphygmograpb. a, b. Lever ; c, d. fixe for attachment of spring e f; /. button for restine on the pulse ; g h. dotted lines indie the position of lever a b when elevated ; %. spring for regulating movements of levc head of upright ;-od, resting below on /, and which, by a little metal shoulder, elevate lever a b. Fig. 15. Marey's drum or tambour for obtaining delicate tracings of pulsations. T, drum. a. Aluminium plate resting on the drum ; b, tube communicating vnth the d £. Ring by which the apparatus is fixed on an upright brass rod. li. A long, light wc lever. P. A pen point at the end of the lever for making tracings. Fig. 16. Marey*s cardiograph for obtaining simultaneous tracings from different pa] the apparatus. On the right is seen a revolving cylinder for obtaining tracings, le, \ Levers moved by drums, which are seen imder A3 connected with india-rubber tubei tv, tc, lying in front of the instrument, are india-rubber tubes filled with air, and havi; V and c, small conical bags, for insertion into the blood vessels or into one of the cavit the heart. Fig. 17. Sphygmosphone of Upham, for discriminating between the times of alte pulsations by sound, a 6. Bells ; c d. hammers worked by the two electro-magnets g keepers of the electro magnets g, having c d attached ; i i*. bell-shaped glasses, the m.' being covered with India rubber, and having round metallic plates resting on them sruj ing we levers kk'; 2 m. two similar bell-shaped glasses for receiving the impulse froi heart and vi'rist. The glasses i i' and I m, and the India rubber-tubing connecting the: filled with water, p, q. Connectors for wires leading from a battery and conveying elect to work the electro-magnets. PRACTICAL PHYSIOLOGY. Plate XXI 9 ' (9 Wn/fsmton A3