(1 ^ t '!•' '-(I'r ' A ^ ‘ I '^,'1 ’ V. '; ^ ' ^: ?v < ‘ ! 0 S r,/// ' . ' , '- 'I K c ; < •^: i‘i ^-•Y;Vp<< .V 5 1 0 : -. . * ' . ! ' ' ' ’ ‘ ''(''I’’ 'I y ^ ,1 :.\‘ O 'i ' , \ ^ ' V w ‘ . V " , ■ ‘ i ' ' ' '"- '■’'' ^ f ^ . V .t//' fMSSMS!§my0S ■ :■ :‘<:t ^ •'. f,‘*<\i' ‘:‘< :’i"M'- Jj'j v •••?.! 'iri*: . .'^:fl;:>; t '. t-;» ■: •; r^'. v THE PHYSIOLOGICAL ANATOMY ANT) PHYSIOLOGY OP MAN. BT ROBEKT B. TODD, WILLIAM BOWMAN, AND LIONEL S. BEALE, FELLOWS OF THE EOTAL SOCIETT ; FOBMEK AND PRESENT PROFESSORS OP PHTSIOLOGT AND OF GENERAL AND MORBID ANATOMY IN KING’S COLLEGE, LONDON. A New Edition by the last-named Author. LONDON: LONGMANS, GREEN, READER, & DYER. 1866. FEINTED BY HAEEISON AND SONS; 6T. MAETIN’S lake. This edition of the original work of Dr. Todd and Mr. Bowman, has been prepared by Dr. Beale, their successor in the chair of Physiology and of General and Morbid Anatomy in King’s College. His name therefore appears in the title page as joint author. Dr. Beale had already assisted the authors in the completion of the concluding part of their second volume, but for the work in its new form he is alone responsible. The present part, consisting of the Introduction, Chapter I. on Structure, and Chapter II. on Chemical Composition, is complete in itself. In the further prose- cution of the work, the original plan will be adhered to as closely as possible, but the text will be modified where necessary, and numerous new figures introduced. King’s College, London. June, 1866. Digitized by the Internet Archive in 2016 https://archive.org/details/physiologicalana01beal THE /V'\ ^fiCCEO, Tll^yi CoMERCAVT/f R i “I \^'/j "r 1 0'v'V'’ XjH li ^ 10 PHYSIOLOGICAL ANATOMY AND PHYSIOLOGY OF MAN. INTRODUCTION. The aim of all natural knowledge is to ascertain tLe laws wliicli control and regnlate tlie phenomena of the nniverse. So numerous, and so diversified are these phenomena, that for then’ study a division of labom has been found not merely convenient, but absolutely necessary. The position and movements of the planetary system, the cmst of the earth, and its various com- ponent strata, the treasiues hidden in its womb, the abundant vegetation that grows upon its sruface, or beneath its waters, and the munberless hosts of animals that dwell upon the land, or in the rivers, lakes, and seas form separate branches of scien- tific investigation, between which a sufficiently distinct line of demarcation is established by the natrue of the objects of inquuy peculiar to each. But, in all departments of science, the same general rules for conducting the investigation prevail, and it is only by a close adlierence to these that we can arrive at safe and satisfactory conclusions. In any scientific inquiry, the first step must be to form a general notion of the characters and properties of the objects of investigation. In the next place, it is necessary to observe carefully the phenomena winch they natmully present ; and, if they be witlfin our reach, to produce such variation in them by artificial meairs (by experiments), as may serve to throw B 2 ULTIMATE FACTS. THEORIES. light upon then natine. If the phenomena under obsei’vation be complex, we must analyse them with a view to ascertain the simpler ones of which they are composed. By this analysis, and by the elimination of such as are merely collateral, we anive at a phenomenon, micomplicated, incapable of further subdivision, and fundamental ; and this we are contented to receive as an ultimate fact, the result of a law in constant and miiversal opera- tion. The accumulation of observations and experiments affords us Experience ; points out the orduiary succession of phenomena, and teaches us the ways of Nature. If these phenomena are found to present a certain uniformity, we are authoiized to refer them to the operation of one common Cause, and we are thus led to the expression of the Law wliicli regulates their occiuTence. Proceeding in this way, we are enabled to explain the whole train of phenomena which have been investigated, — that is, to devise a Theory wliich develops the rationale of then’ occiuTence. But sometimes om- experiments and observations tlmow an imperfect light upon the phenomena which are the subjects of investigation ; or the latter are so remote, or so little imder our control, as to render both observation and exjieriment exti’emely difficult, and in some cases unpossible. The “ instances ” which we are enabled to collect are, consequently, dubious and obscure, and point darkly or not at all to ultimate facts ; they present little or no general resemblance, and cannot be properly asso- ciated together. Here is no foundation on which to build a theory ; but great advantage may be gained, if, with the httle light we derive fi’om these particular obseiwations, aided by previous knowledge of general laws, we can frame an hypothesis, offering some explanation of the phenomena. The adoption of such an hypothesis, even for a temporary piupose, will “ afford us motives for searchmg into analogies,” may suggest new modes of observation and experiment, and “may seiwe as a scaffold for the erection of general laws.” Previously to the time of Lavoisier, chemists were perfectly familiar with the occmTence of combustion under various ch- cumstances; but the opinions (hypotheses) which prevailed as to the real nature of this process, afforded a very unsatisfactory explanation of it. Subsequently, however, by the laboms of Lavoisier, Davy, and others, t his complex phenomenon has been observed in all its phases ; it has been carefully analysed, and HYPOTHESES. 3 has been proved, to occiu- in all cases, where substances pos- sessed of strong chemical attractions, or different electrical relations, are brought within mutual influence. The ultimate fact thus arrived at is, that intense chemical combination always gives rise to the evolution of heat, and, in many instances, to that of light also. Again, a great number of observations have shewn that bodies combine together only in certain quantities, or in multi- ples of them ; that each body has its proper combining quan- tity, and that it never enters into combination except in that quantity, o-r some mifltiple of it. This is an ultimate fact, ascer- tained by nmnerous experiments, and indicates the law, which is so important m chemistry, that bodies rmite with each other in then- combining proportions only, or in multiples of them, and in no intermediate proportions. And tins, again, has led to the beautiful generahzation of Dalton, that the ultimate atoms of bodies are their respective combinmg quantities, and bear to each other the same proportion as their combining equivalents do. Or, to take an example from the science which is to form the subject of the following pages. The function of resphation in animals is a very complex process, respecturg the natm-e of which many rmsatisfactory hypotheses had been formed, owing to the obscimty m wMch many of the phenomena, immediately or remotely comiected with it, were involved. Until the law of the diffusion of gases, and of the permeability of membranes by them, had been developed, and until it had been shewn that carbonic acid is held in solution in venous blood, no theory of resphation could be framed adequate to explam all the pheno- mena. It is now proved, that, in this process, a true interchange of gases takes place through the coats of the pulmonary blood- vessels, the oxygen of the air passing through and occupying the place of the carbonic acid of the blood while the latter is diffused into the ah’ in the pulmouary vesicles. An admh’able example is thus afforded of a process most important to life taking place in obedience to a pm’ely physical law. Living objects are those which properly belong to the science of Physiology. These are strongly contrasted with the inanimate bodies (which have never lived), to which other branches of natural science refer. At the same time, there are many points of resemblance between them; and as both owe their B 2 4 ORGANIZED AND origin to tlie same Divine Author, and are reducible (as ^vill be seen by-and-by) to the same elementary constituents, so they are subject in a great degree to the same physical laws, and are to be investigated according to the same piinciples of philoso- phical inquiry. In this Introduction we propose, m the fii’st place, to consider the characters in which organized bodies agree with or differ from inanimate, mineral, or unorganized bodies, and then to refer bi’iefly to the structure and special endowments of hsdng beings. Next, the relation of the physical and vital forces will be briefly discussed, and we shall endeavom- to show that phy- sical are distinct fi’om vital phenomena. Life and some of the theories of life of -the gneatest mterest to the physiologist vull then be alluded to, and the diversity of the forms of living beings, and the general differences existing between plants and animals considered. Lastly, we shall endeavom to point out the value of a knowledge of physiology, especially that of man, to tlie diagnosis and treatment of disease, and the modes of pmsuing this branch of natm’al knowledge. OF ORGANIZED AND UNORGANIZED BODIES. Living bemgs have been somethnes said to be organized in the sense of being composed of certain distinct parts or organs, each ha'vdng its own definite stractm-e, and capable of fidfilling a certain end. But if the term be used in this sense its use must be restricted to the higher organisms after they have reached a certain stage of development, for every hrdependent living organism, at the outset of its Kfe, consists merely of a colomless, transparent semifluid matter, disclosing no structure whatever, and possessmg no distinct paids or organs. Yet tliis matter Lives; it is capable of forma tiou, of increase, and of multiplication, and it must be regarded as an independent living organism, organized although exhibiting no structure. We therefore extend the term organized to every Idnd of matter endowed with these pecuhar powers or capa- bilities. They are characteristic of life, and are manifested by living matter which came from pre-existmg hving matter : never have such endowments been shown to exist in relation Avith any inorganic unorganized matter whatever. UNORGANIZED BODIES. 5 All organisms are composed of and are capable of producing peculiar organic matters of complex composition, and often endowed with peculiar properties. By ■proximate analysis several different organic compomids may be obtained from every organism. By ultimate analysis these organic compomids may be resolved into simple elemen- tary substances, such as constitute other objects of the imiverse. The various bodies that compose the mineral kingdom, have not the same complex composition, nor do they exhibit that distmctness and variety of structm’e hi them component parts, which is so characteristic of at least the higher organisms, nor is there any adaptation of then’ parts to separate fmictions. They never exhibit the wonderfid properties characteristic of the hving matter winch exists in all organisms, but in these alone, and they are therefore called unoryanized or inorganic. Chemical analysis resolves them into simple elements wliich admit of no further subdivision. Life, Death, and Dormant Vitality . — Organized bodies are fomid in two states or conditions. The one, that of life., is a state of action, and of change. The other, that of death, is one m which all vital action has ceased, and to winch the dishitegration and chemical decomposition of the organized body succeed as a natm-al consequence. But it cannot be said that any living body exists which at any one moment consists entnely of living matter. In every hvhig organism, at every moment, so long as its life lasts, there is matter that lives and matter that has ceased to live. An organized body in a state of active hfe exhibits growth and nutrition, and resists the destructive influence of sur- rounding agents. Thus the development of structmes is pro- moted, and the hitegrity of the body itself is preserved. The simplest thing gromng, animal or vegetable, is an illustration of this remark. But there are organized bodies m which life is said to be dormant. If in these, actions or changes occm’, they are so slight that they cannot be observed; nevertheless, if placed under certaio favomuble conditions, vital activity null soon become manifest in these organized boches. Of this we have familiar examples m a seed, and hi an egg. It is well knovm that seeds vdll retain their form, size, and other properties for a 6 LIFE. DEATH. DOEIilANT VITALITY. very considerable period ; and aftei-wards, if placed under favoiu’able conditions, 'will exhibit the process of gei-mination as completely as if they had been only recently separated from the jDarent plant. Eggs, also, may be preserved for a long time without mjuiy to the power of development, or to the nutrition of the embryo contahred within them. But neither eggs nor seeds will exliibit vital activity if kept beyond a definite period of time. This fact renders it probable that certain slow changes do occur even in this dormant state ; and that when these changes have once ceased no altered conditions whatever will recall the power of germination to egg or seed. It is worthy of observation, that those processes, which denote vital activity, may be sometimes temporaiily suspended, even in fully formed annuals and vegetables ; and, in such instances, life may be said to become dormant. That is, mider these altered conditions, changes occrn so slowly as not to be perceptilde to ordinary observation. The privation of moistm*e or of heat is the ordinary cause of this paidial cessation, or diminished activity of, the phenomena of life. In chy weather, mosses often become desiccated, and although they appear quite dead, will nevertheless speedily revive on the apphcation of moistine. The common wheel animalcide, although apparently killed by the drying up of the fluid in which it had been immersed, will speechly resmne its active movements on being supplied anew vdth water. But this desiccation is not perfect and complete desiccation. Whenever hving matter of any kind is perfectly dried, it is killed, and can never be resuscitated. The manner m which the hving matter is protected renders it very difficult to dry it thoroughly, and if but the most minute particle remains moist, it may retain its vitahty, and increase and exliibit vital actions whenever the conditions mider wliich it is placed become favomuble. Certain hving organisms and tissues may be frozen without bemg kihed, but in this case it is doubtful if the germinal or hving matter itself be rendered sohd, any more than by desiccation it is completely deprived of water. Composition of Organized and Unorganized Bodies. — Inorganic bodies may be resolved by idtimate analysis into oxygen, hydrogen, nitrogen, carbon, and about fifty other substances, which chemists regard as simple, because they appear to consist of one kind of matter only ; that is to say, they have hitherto PROXIMATE PRINCIPLES. 7 resisted fatlier decomposition. These elements unite in certain definite proportions to form the compound inorganic substances. Organized bodies are capable of being resolved, by ultimate analysis, into inorganic simple elements ; but the list of simple substances -which may be obtained fi-om this source comprises only about twenty. Of the fom' widely-spread elements, oxygen, hydrogen, nitrogen, and carbon, two, at least, -will be found in every organic compound; hence, as Dr Front has suggested, these fom may be conveniently distinguished as the essential elements of organic matter. The other simple sub- stances are found in smaller quantities, and are less extensively diffused; these may be termed its incidental elements. They are sulphiu', phosphorus, chlorine, sodium, potassium, calcium, magnesimn, silicon, ahunhiium, iron, manganese, iodine, and bromine, and probably others ; the last two are obtamed almost exclusively fi-om marine plants and animals. Proximate Principles. — From various animal and vegetable tissues, and fi-om then- fiuids, may be obtained by proxhuate analysis, a class of substances which have been grouped together under the head of proximate principles, or organizahle substances, because they are specially concerned in nutrition. It is these substances which form the most important constituents of the food of man and the higher animals. The following are examples of proximate principles — gluten, starch, lignine, fi-om the vegetable textm-es ; albumen, fihrine, casein, fi-om the animal, ones. From the organized structm-e, called muscle, for example, we obtain by analysis, first fihrine, a proximate principle, which is its chief constituent ; and, subsequently, by the analysis of fibrme, we get the simple elements, oxygen, hydrogen, carbon, nitrogen, and sulphtu-, in certain proportions. On the other hand, by synthesis, or the combination of certain simple morganic elements in the organism of the plant, an organic compound, closely allied to fibrine, is produced ; fi’om which, or from allied substances forming- the food of animals, the organized structure, muscle, is formed. In many organized bodies the constituent particles are, as it were, artfully arranged, so as to form peculiar textures, destined to serve special purposes in the living- mechanism of the animal or plant to which they belong. These textures exhibit peculiar structure, which is one of the results of vital action, although 8 OF THE SYNTHESIS OF tlie tissue which has been foimed may not be alive. The chemical componncls which maybe obtained from these textures by analysis are devoid of any mechanical aiTangement of particles. From these again a great vaiiety of compounds has been obtained by various chemical processes, owing to the tendency winch then- elements have to foiTO new combinations. By boil- ing starch in dilute acids, it becomes converted into a Mnd of giun, and starch-sugar ; and, in the germination of barley, or of the potato, a peculiar substance is foimed, the contact of which with the starch of the barley or potato converts it into sugar. Innumerable examples might be quoted from various vegetable compounds, shewuig that the affinity, which holds together the elements of organic substances, is so feeble, that it affords but slight resistance to thefr entrance into new combinations. The proximate principles of organic substances consist for the most part of three or foiu of the essential sunple elements, and, as many of them contam a large number of atoms, their combuiing proportion is represented by a veiy high number. Respectuig the mode of combination of these elements however, the greatest imcertainty prevails, and it is indeed doubtful if many of the substances which have received special names, as albumen, jihrine, and the like, are really definite chemical sub- stances of fixed composition. Chemists have not yet succeeded in obtaining the majority of these bodies in a state of chemical purity. Secondarn Organic Compounds . — From the blood, from the tissues, and from many of the fluids secreted by different organs of the body, by proximate analgsis, may be obtained another class of substances derived from the process of destruction of the organic substances enteiing into the formation of the tissues, blood corpuscles, or gland cells. These have been called secondary organic compounds, and thefr chemical com- position is far simpler than that of the proximate piinciples. Urea, uric acid, kreatin, kreatininej Mppuric acid, leucin, tgrosin, are all organic substances, which result from the oxidation and dis- integration of more higlily complex organic substances fri the organism, and are examples of secondary organic compounds. Of the Synthesis of Organic Compounds . — As has been remarked already, much micertaiuty exists in reference to the mamrer of combination of the simple elements to form the higher and more ORGANIC COMPOUNDS. 9 complex organic compounds. It is tlierefore not surprising that the attemjits of chemists to produce them by artificial processes should have met vdth so little success. No one has succeeded in the formation by synthesis of albumen, fibrine, or any of those substances (as for example, the constituent of white fibrous tissue), of which the greater part of the bodies of animals is composed. Not even starch, or the celhdose of the very lowest simplest vegetable organisms has been prepared by synthesis - m the laboratory. Indeed, it is veiy questionable whether any of those substances which may be considered as the first or immediate result of vital actions will ever be produced elsewhere than in the living organism. Of late years a vast number of those substances which result from the action of oxygen upon compounds formed in animal and vegetable organisms have been made in the labora- tory from inorganic matter. The formation of m-ea, a second- ary organic compound, has been effected by Wohler fi-om the cyanate of ammonia, by deprrifing it of a little ammonia tlnough the action of heat. And it must be admitted, as no luiimportant step in the sjmthesis of organic compounds, that nitrogen gas has been found to unite with charcoal, under the influence of carbonate of potassa at a red heat. The cyanide of potassium, which is thus formed, yields ammonia, when decomposed by water ; so that cyanogen, and tlnough cyanogen, ammonia, can be primarily derived from their respective elements contamed in the inorganic world. Allantoiu, an analogous compound to mea, formic, oxalic, glycolic, lactic, butyidc, leucic, oleic, and a number of other organic acids, have likevfise been artificially produced. No compound allied to albumen has yet been prepared arti- ficially, but many substances beariug to it much the same relation as mea, have been produced. In short, the substances affeady formed in the laboratory by synthesis, correspond with those which are produced by the chemical action of oxygen upon products resulting fi-om the dismtegration of more complex chemical substances. They are allied rather to the substances included in the secondary compounds, than to the group of proximate principles. They are the results of a long series of chemical changes occm-rmg in the organism, and are so far removed fi-om the actual constituents of the tissues, and fi-om the substances which immediately result fi-om the death of 10 OF THE STRUCTURE OF living matter, that their artificial production affords no safe gi'ounds for supposing that the former complex substances will ever be manufactured in the laboratory, or that a Hving organism will some day be produced by the synthesis of inorganic elements ' as some have not hesitated to regard as possible when organic chemistry shall have advanced to a higher state of perfection. OF THE STRUCTURE AHD SPECIAL CHARACTERS OF ORGANIZED BEINGS. The higher plants and animals are composed of parts often termed organs, distinct fi-om each other in stractm’e and function. Enteruig mto the formation of these organs are many different textmes, each differing from the others in physical properties, in then mode of action, and in chemical composition. The existence of a gTeat variety of textm’es in an animal implies a high degree of organization. In beings of a more simple character^ low in the scale of organization, there is comparative uniformity of stnictm’e ; though often a variety of parts or organs, and tissues ha'vfing different properties, exist in the fully developed organism. But, m many cases, it has been observed, that fi-om almost any one part of the body any other portion might be developed. Thus some species of Actuiia, in slowly movuig over the surface of a rock, detach small pieces of the margin of the disc. From each one of these detached portions a perfect actinia, vdth its tentacles, external coverhig, gastric membrane, glands, and muscular and nervous apparatus and generative organs, is developed. In the lowest and simplest organisms there is no indication of distinct parts or organs. The entne creatme seems to con- sist only of a small mass of clear structmeless material, which possesses in every part the power of mo^dng hi any direction, which absorbs nutrient matter, and grows and multiphes by por- tions bemg from time to time detached. There is a time when eveiy organism, even the most com- plex, consists of such a sunple mass of colourless, groving, moving, matter. Eveiy organ, every tissue, is represented at an early period of its development by such a simple and apparently almost homogeneous mass of plastic material. Such structiueless material exists also at every period of the life even of the most complex tissues. The physical property of THE CELL. 11 tlie tissue does not depend upon this matter, nor is its function due to it ; but no tissue can be produced or be increased without it. There can be no life in the absence of this simple matter. In fact, the tissue does not grow of itself, but new tissue is produced by changes occiming ui tliis soft, plastic matter, and it is added to the tissue which already exists. Neither does the tissue multiply, assunilate, form, or convert, but all these phenomena are effected by the agency of this wonderful simple plastic matter. It is remarkable, that as soon as this matter undergoes conversion into tissue or into any definite chemical compound it loses for ever the active powers above referred to. From this colomdess transparent mateiial, then, every tiling characteristic of a living body is formed, or, in other words, the matter of wliich all the tissues and substances pecuHar to the organism are composed, was once in tliis state. A mass of any tissue at every age may be divided into elementary parts, each one of which contains a portion of this transparent matter within it. Each one of these elementary parts may be termed a “ cell.” In some tissues the “ cells” can be readily separated from one another, but in others, the outer part or tissue of one “ cell” is continuous with that of neighboiuing cells. Various forms of cells are represented in Plates I, II, III, and IV, an examination of which will enable the reader to form a clear notion of the striictm’e of the principal kinds. The simplest or most elementary organic form with which we are acquainted consists of a portion of this soft, transparent, colourless matter, surrounded by a layer of matter formed from it, which may be so thin as to be hardly visible. Tliis latter results, in fact, fr'om the action of external conditions upon the most external portion of the mass. Such an elementary part may be less than the , ^ ^ ^ of an uich in diameter, and may, we believe, exist so small as to be invisible. Still it is a living, and, in a certain sense, mdependent organism, capable of increase and endowed with the power of giving rise to other bodies lik e itself These wonderfrd powers, as afready stated, reside not in the formed matter upon the surface, but ui that vdtlun, which is in formless but living state. The latter may be termed Ger- minal matter. Such is the simple structiu’e of the “cell” — of every cell which 12 OF THE CELL. THE FUNCTIONS. exists in natui’e at an early period of its development. Remark- able alterations in character often occru’ as the cell advances in age, and many veiy different forms of “ cells” result. The natui’e of these differences carmot be discussed here, but they vdll be explamed when the structure of the various tissues is considered and then- development traced. The account here given of the structure and action of the cell differs from that generally received in several essential particulars, but these differences will be noticed in then- proper place. Each organized body has its appropriate and specific shape ; and to each a certain size is assigned. To observe and classify the wonderful diversity of forms of plants and animals, has given employment to Naturalists in all ages ; and the sciences of Zoology and systematic Botany have been founded upon the results of then’ laboiu’s. Every organized body, and evei-y part of an organized body, is limited in its duration; it has “its time to be bom and its time to die,” and at death it passes by decomposition into simpler and more stable combinations of the inorganic elements. Death, however, occiu’s at every period of the Hfe of an or- ganized body. From what has just been remarked with regard to structiu’e, it follows, that every anatomical element or cell is gradually undergoing change diu’ing hfe. Pabuliun passes into the active matter and assmnes the active state, while some of the latter becomes passive and is converted into new sub- stance, which is added to that wliich was afready formed, or takes the place of that wliich has been removed. It is, therefore, e\ddent, that not even the most minute cell is at any moment composed of matter in precisely the same state in every part. There is matter which is about to hve, matter that is alive, matter wliich has ceased to live, and matter that is imdergoing disintegration and is about to be cast away. The entire cell or elementary part is not ahve. The inner matter is living — the outer formed matter has ceased to hve. The inner matter alone is capable of growth, of germination. It may, therefore, be called hving or germinal matter in contradistinc- tion to the passive formed matter which envelopes it. As each organized body has a certain end to seive in the economy of the living world, so each organ has its proper use in the animal or plant. In this adaptation of parts to the per- DIFFUSION. OSMOSE. 13 formance of certain functions, we see the strongest evidence of Design ; and, amidst much apparent chfference of form and obvious diversity of pm-pose, the anatomist recognizes a re- markable miity of plan — affording incontestable proof that the whole was devised by One Mind, infinite in wisdom, imlhnited in resource. Of the Functions. — The various processes by which are effected the ceaseless motion and changes so characteristic of living beings, are called in Physiological language, functions. The function is the work, or duty, or office in the economy per- formed or discharged by a particular tissue or organ. Con- traction is the function of muscle ; the secretion of bile is the function discharged by the liver ; the secretion of urine that of the kidney. Digestion, or the operation of dissolving the food, is the function of the stomach, &c. The fiuictions may be divided into two great classes: 1. The vegetative functions ; and 2. The animal functions. The first class may be fiu’ther sub- divided into the nutritive functions which are connected vdth the preservation of the individual ; and the function of generation, which is concerned in the propagation of the species. The functions specially characteristic of man and the liigher animals are locomotion and innervation. They have been termed the animal functions — a definition wliich is not strictly accru’ate, but, nevertheless, practically advantageous. Physical processes occurring in cells. Of Diffusion. Osmose, and of the Colloid state . — Physical changes of the utmost im- portance occur in connection Tvdtli the various processes takmg place in the elementary parts or cells of living organisms. By diffusion is understood the tendency which one fluid or gas manifests to mix intimately Avitli another. Even if the specific gravity of a fluid below be far higher than that of one winch is above, the latter will gradually pass upAvards and the former doAATiwards rmtil they are equally diffused through, and inti- mately mixed Avith, each other. This tendency, therefore, does not depend upon specific gravity, but upon some peculiar pi-o- perties of the matter itself. A solution of common salt has a diffusive power nearly twenty times as great as a solution of albumen of equal strength. Closely related to the physical process of diffusion is osmose, in which the tAvo fluids or gases are separated from one another 14 DIFFUSION. OSMOSE. by a porous diapbragm, and the result is influenced by the different degrees of adhesion exerted by the fluids or gases to the septum. DutrOchet, who fli’st studied this process, showed that if a little alcohol were placed above a piece of bladder tied over the extremity of a fuimel connected with a long tube, wliile the mider surface of the bladder were allowed to touch the surface of water, the water, owing to its greater power of wetting the bladder, would enter into its pores, and thus pass upwards into the alcohol. This process continuing, the mixtm’e of water and alcohol would gradually rise in the tube against the force of gravity, and would at last overflow. Here endosmose, the flowing inwards, of the water, greatly exceeds exosmose, the flowing outwards, of the spirit. The phenomena concerned in the process have been investigated by Graham, who has shown that alkaline solutions exhibit a remarkable endosmotic power (positive osmose), while acids exhibit the contrary, or exosmotic tendency (negative osmose). In cells, and hi various secreting organs, we have not only the most favourable conditions for osmose and diffusion but the means for maintaining these conditions. The process never comes to a standstill, as in oin osmometers, because new acid or alkahne fluid is continually being generated to take the place of that which is removed, while the mixed and altered fluids are earned away. There is also provision for the preservation of the integrity of the porous septum, and for its reproduction. By the recent researches of Professor Graham many veiy interesting points with reference to the physical constitution of several substances entering into the formation of the hAung body have been brought to hght. He has shovm that sub- stances exist in the organism in what is termed a colloid state, in which condition they wiU not permeate a porous diaphragm ; wliile, on the other hand, crystalloid substances wiU readily pass through such a diaphragm when in a state of solution in water. The fact is one of great practical importance, and has been most successfully employed for the pm-pose of separating poisonous matters of a crystalloid natiu'e fi'om then- solution in the animal fluids (dialysis). The crystalloids readily diffuse themselves through a large quantity of water, while the diffusive tendency of colloids is very low. It might be said, that the “ Ihung matter” of the cell in ASSIMILATION. EXCRETION. 15 ■which such wonderful powers are supposed to reside is simply matter in a colloid state, and it may be admitted that some of the phenomena which have been observed in connection with this matter resrdt from or are determined by its mere physical constitution. But living matter does not possess the same properties or powers in every part of its mass, and when magnified very highly, it is seen to be composed of spherical particles, varying somewhat in size. Colloidal matter, on the other hand, exliibits no such pecrdiarities, so that there is a great "visible difference to be observed between this li-ving matter and matter in a colloid state,— to say nothing of the changes occm-ring in the li-ving matter, wliich distinguish it in the most marked manner fl’om matter in every other known state. Professor Graham has sho"wn that certain mineral substances exist in a colloid as well as crystalloid form. Hydrated silicic acid and soluble alumina are examples. Perhaps the most interesting example in the li-ving organism of an organic body, which may exist in both conditions, is the material of wliich the red blood coi-puscle is composed, which sometimes, as in the case of the Guinea-pig, passes from the colloid to the crystalloid condition soon after it has been removed from the cu’culation and allowed to become stationary. Of Assimilation and Excretion . — Organized bodies can appro- priate and assimilate to their o-uui textru’es other substances, whether inorganic or organic. This process is that which is most characteristic of li-ving creatures : in -virtue of it, animals and plants are continually adding to their textiues new matter, by which they are nourished. Plants appropriate then nutri- ment from the inorganic kingdom, as well as from decaying organic matter ; animals, chiefly from organic matters, whether animal or vegetable. Both possess the wonderful power of rearrangmg the constituents of these substances into fonns identical -^flth those of the elements of their various tissues — and of thus making them part and parcel of themselves. Together -with a process of supply, there is one of waste continually in operation. Animals and plants are ever tlno-wing off effete particles from their organisms. These, under the name of excretions, appear in various forms — either as inorganic compounds, or as secondary organic products. Thus carbonic acid is given off in large quantities from animals ; water, like- 16 ORIGIN. REPRODUCTION. SPONTANEOUS GENERATION. wise, forms a considerable portion of their excreted matter, and serves to hold m solution salts, and secondary organic com- pounds, which result from the waste of the tissues. In this way, also, m-ea, uric acid, and biliary matters are excreted. In plants, water is excreted from the leaves, a phenomenon which has been compared to the perspuation of animals ; and various other excretions, which are sometimes made to seiwe an additional prupose hr the economy of the vegetable, besides that of getting rid of superfluous matter, are doubtless formed by the secondary corrrbinations of the effete particles of their textrues. These two processes, excretion^ or the expulsion of effete particles, and assimilation of substances from without, are neces- sarily mutually deperrderrt. The work performed depends upoir the destruction of particles whose place must be occupied by new ones, for were excretion alone to go on, the destruction of the organism rrrust speedily ensue, by the gradual waste of the tissues ; and as long as new matter is being appropriated, old particles must be thrown off, othervdse growth wordd be rm- limited. Iir both processes new combinations are taking place, as it were, nr opposite dh-ections ; nr the one from the simple to the complex to forrrr organized parts, in the other, fr-om the complex constituents of the textrues to the simple organic, or inorgarric compounds. Origin. Reproduction . — Organized bodies are always derived fr-om similar ones. Some have supposed that out of decaying vegetable or annual matter nihiute animals or plants of other lands may be formed ; but it is most probable that in those cases in which they had been supposed to be formed, the seeds or eggs, or everr the new beings themselves, had beerr con- cealed in the decajdng matter, or conveyed to it from the sruroimding atmosphere. Neither vegetation nor the develop- ment of animalcrrlae vill go on in fluids which have been sub- jected to such processes as must inevitably kill whatever germs may have been diffrrsed around or thr-oughout them. E^’ery year new facts are chscovered which add to the overwhelming evidence hr favour of the Harveian maxhn, “ Omne vi'^urm ex ovo,” usmg here the word ovum in the wide sense of a germinal elemerrt derived fr-om a parent. The progress of Anatomical krrowledge is every day revealing- to ns the mode of generation HETEROGENESIS. 17 in the minutest and the least conspicuons forms of vegetable and animal hfe ; and thus the hypothesis, which assumes that living objects may arise by a sort of conjunction of the inorganic elements of decomposing organic matter, becomes more and more untenable. Of Spontaneous Generation or Heterogenesis . — Of late years the doctiine of spontaneous generation has been revived in more than one form, but, the conclusions in favour of such an origin of Hving beings are unsupported by sufficient evidence. Nor would it be possible were our highest mag- nifying powers increased tenfold, or even a hundred, or a thousand fold, to see the actual particles of matter combining to form part of a Hving structm'e. Those who assert that they have seen particles aggregating together to fonu a Hving being profess to have actually observed by a comparatively low power that which eertauily cannot be seen under a power magnifying ten times more, and with advantages of demonstration which were not at their disposal. Observations made by the use of the highest magnifying powers, and great improvements, in the means of investigation not only render the doctrine of spontaneous generation less and less tenable, but demonstrate the origin of Hving beings fi’om pre-existing ones m so many instances that the most scep- tical ought to be convinced “ that every Hving particle comes from a pre-existmg Hving particle,” “ Omne vivum e vivo.” How beautifrd is the provision which tins power, possessed by organized bodies, of generatmg others, affords, for preserving a perpetual succession of Hving beings over the globe ! The command, “Increase and midtiply,” has never ceased to be fulfilled from the moment it was uttered. Every hour, nay, every minute, brings uito being countless myriads of plants and animals, to supply hi lavish profusion the havoc which death is continually maldng ; and it is impossible to suppose that the earth can cease to be in this way replenished, mitH the same Almighty Power, that gave the command, shall see fit to oppose some obstacle to its fulfilment. In addition to this power of propagation, organized bodies enjoy one of conservation and reproduction of parts. Solu- tions of continuity, the loss of particular textures, whether resulting from injmy or fr-oin disease, can be repaired. Parts, C 18 OF PUTREFACTION'. that have been removed, may be restored by a process of growth in the plant or animal, and in some animals the reprodnctive power is so energetic, that if an indimdual be divided, each segment will become a perfect being. This power of reproduction is greater, the more simple the struc- ture of the organized body; the more similar to each other are the constituent parts, the more easy will reproduction be. Numerous examples of this power may be adduced, — the healmg of wounds, the adhesion of divided parts are familiar to every one. New individuals are developed from the cutting of plants ; the division of the hydi’a into two, gives rise to the production of two new individuals. If a Planaria be cut into eight or ten parts, according to Duges, each part will assume an independent existence. The power of reproducing single parts only, is possessed by animals higher m the scale. In snails, part of the head, vith the antenna, may be reproduced, provided the section have been made so as not to injm-e the cerebral ganghon. Crabs and lobsters can regenerate then claws, when the separation has taken place at an articulation; and spiders enjoy the same power. In lizards, the tail, or a hmb, can be restored, and in salamanders the same phenomenon has been frequently wit- nessed ; and even m man certain tissues may be reproduced. In the reproduction of lost parts, it must be borne in mmd that changes precisely similar to those which take place during the development of the textm-es in the embryo, occur ; in fact, the new tissues are developed from amorphous hwng matter. In all cases masses of simple structureless germmal matter exist, and grow, and multiply before any form or structm-e is manifested. Of Putrefaction , — Dead organized matter is speedily dis- sipated under certain conditions. These are the presence of air, moistiue, and a certain temperatm’e, or contact with an organic substance wdiich is itself undergoing decomposition. The con- ditions imder wNich the mtegrity of the organic substance was -preserved, have become altered, it is destroyed, and its elements are set free to obey new affinities and form new compormds. When we consider the large number of equivalents which enter into the formation of each molecule of organic compounds, it need not excite smprise that a great variety of products results from the decomposition of animal and vegetable matter. OF PUTREFACTION. 19 This decomposition is -usually accompanied by fermentation or ■putrefaction. It used to be supposed that these were pm-ely chemical changes, due to what was considered catalytic action, but it is now known that m both processes living organisms play a most essential part. The process of fermentation is dependent upon the growth and multiplication of vegetable organisms, and it is probable that the carbonic acid and alcohol so characteristic of one kind of fei’mentation result from the death of living particles under the conditions present. In the process of putrefaction, the researches of Pasteur have shovm that so far from oxygen being necessary to the life of the simple Hving beings concerned, there are certain forms of infusoria which not only pass then lives without oxygen, but are killed by its presence. All experiments have proved that the germs from which these organisms are developed gain entrance fr’om without. The size and transparency of some of these particles are such that they are only just visible by an exceedingly good power wliich mag ni fies upwards of 5,000 diameters.* It is certain that germs exist far more minute than these. They may even exist in the iaterior of the liigher organisms. We know they are present in great number on the smfaces of mucous membranes, and even in the interior of glands. It is pro- bable that such germs exist in the blood, and would multiply rapidly if the state of the fluid once became favourable. Nor are cases wanting hi which the decomposition of tissues, and of the blood, and the multiplication of such low forms of life, have occmred in the living body itself, — the change of conrse being soon followed by death. The matter, however, which is the seat of this change is dead. The life of the tissue does not become the life of the infusoria, as some have maintained, but the tissue becomes disintegrated, and the infusoria, derived from infusoria that lived before them, live upon the products, just as other organisms may live upon the matters resulting fr-om the death of the infusoria. Living matter never lives upon fr-ving matter by the life of one organism being converted into the life of another, as some have speculated. Li-vdng matter must itself die ere it can pass as food to form part of any living organism. * How to work with the Microscope, 3rd edit., p. 217. 0 2 20 OF FOKCE. In form, in size, in duration, the contrast between organized bodies and inorganic substances is most striking. The inor- ganic matters are aeriform, bquid, or soHd : they are prone to assume the crystalline form, and to exloibit surfaces bounded by right lines, and uniting to form angles. No distinction of parts, or organs, is to be found in the mineral substance ; its minutest fi’agment is in eveiy respect of the same nature with the largest mass. A portion of sand not weighing a grain contains particles of the same form and size as those of the largest sand-banks knoMm. Inorganic substances, as compared with organic, are milimited in size and dm’ation. Then- bulk; is indefinite and they retain the same condition for ages, without augmentation or waste, provided no external agent be brought to act upon them. None of those internal actions or processes, which have been described in the organized body, occur in the unorganised one ; there is no inherent motion, no power of reproducing lost or injm-ed parts, no growth, no excre- tion, no conversion, no formation of substances which did not exist before, no generation. From age to age the mineral re- mains unchanged, obechent only to the common laws of matter, and unable to modify then’ operation by any inherent power. OF FOECE. Correlation of Forces . — F orce, which is constantly associated with matter in all its states, is as indestmctible as the matter itself The state or conchtion of the matter may be changed, but matter cannot be generated or annihilated. In like maimer the form or mode of force may be altered in such a way that one form of force, as motion, may be converted into another, as heat, electricity, chemical affinity, and the like, and either of the latter may be made to resume the form of simple energy or motion. It is probable that all the physical forces are mutually convertible, but it is certain that force cannot be produced anew or annihilated. Gravitation, Elasticity, Cohesion, Adhesion, Heat, Electricity, Magnetism, Light, Chemical action, are different fonns or modes of one and the same force. The labom-s of Helmholtz, Grove, Mayer, and others, have proved conclusively the mutual relation, or '■'■correlation" of the physical forces. Just as very different quan- tities of thflerent kinds of matter represent, or are equivalent to PHYSICAL FORCE AND VITAL POWER. 21 one another in combiaation, so it has been conclusively proved that one kind of force gives rise to an equal quantity of the same kind of force which produced it, or to an equivalent amount, which is constant, of some other kind of force. The exact amount of heat produced by the conversion of motion into heat has been estimated, and the mechanical equivalent of heat has been determined by the labours of l\b'. J oule. A certain fixed amount of heat is always set free by the same mechanical auction, lasting for the same period of time. The “motion” becomes the “heat.” So the chemical combination of certain equivalent quantities of elementary substances is equivalent to the force of gravitation by which a certain quantity of matter is attracted towards, or tends to combine mechanically with other matter according to its mass ; and in this mechanical combination a definite amount of heat is produced at the moment of the mechanical contact. What was motion is now heat. The same laws apply to the physical phenomena occurring in the living organism. Chemical combination there becomes converted into heat, and the latter into motion. The amount of work performed by the muscles is probably due to chemical change, and particularly to oxidation occm-ring in the nervous system. This mechanical action of the muscle, there can be no doubt, is one of the som'ces of animal heat. But it must not be forgotten that a far greater amount of work results from the same amount of chemical change in the animal economy than can be obtained by any knoAvn machinery. The wasted force in the most perfect mechanical instrument is far greater than the force which results in actual work. In muscular action, on the other hand, we have an actual amount of work performed, which seems perfectly marvellous, when the very small weight of the machinery and the very small amount of chemical change requhed to keep it in action are considered. Still there can be no doubt that muscular contraction is a physical process, although physiologists have hitherto failed in then* endeavom-s to ascertain the precise nature of the change which occurs. Relation of Physical Forces to Vital Power. — It has been said that there exists not only a correlation between the physical forces themselves, but between the vital and physical forces. The forces, however, which have been denominated vital by 22 OF FOKCE AND LIFE. those who take this view, are really only physical forces mani- fested in living things. The sun is the source of all the physical forces operating in hving beings. Living plants collect or absorb this force, and store it up in the various substances which are produced in then organisms. These, in their turn, become the food of animals, and thus the solar energy in the form of light and heat and chemical rays collected by plants, and retained by them in a quiescent state in the fonn of chemical combination, again becomes resolved into mecha- nical and other forces in the animal, and is the source of those active movements which chstinguish animals fi’om vegetables in such a remarkable degree. All the work perfoiTued by our muscles, all the heat developed hi om- bodies — all the chemical actions resulting from the union of oxygen with carbon, hydrogen, and other substances in the animal body, have them original source in solar energy. Nor is it simprising, that many who have studied these matters should have fallen into the eiTor of concluding that life itself was but another mode of force ; and although this inference has been carefully avoided by Helmholtz and Mayer, and some other philosophers, many have expressed themselves as if they considered that we might for life substitute solar energy^ hcat^ or motion. Although there are some authonties who would not hesitate to affirm that eveiy plant and animal is the mere result of changes m matter brought about by solar energy alone, it cannot be, even in a very loose sense, affirmed that a watch or a steam-engine was formed or built by the sim. And yet, to the physiologist, what poor imperfect contrivances the latter must seem, for, in spite of all the mighty human efforts required for them production, they cannot even repam themselves, much less perpetuate them race ! Hitherto not the slightest approach towards the formation by artificial means of anything havhig the propeiiies of the lowest and simplest form of Hving matter has been made. Between the living laboratory and the chemists’ laboratory there is scarcely any real analogy, for the former builds itself, and the elements therein appear to place themselves in the exact posi- tions required for the production of the particular substance which is to be formed. This self-constructing, self-maintaining, OF LIFE. 23 and self-propagating power, is referred to a something which is certainly but temporarily associated with the matter that exhibits it, and which seems totally distinct from ordinaiy force, since it compels the elements to take up the required special relations. The sometliing to the influence of wliich all these apparently spontaneous operations is due, may he termed vital power. OF LIFE. Within every living organism, and vdthin every elementary part or cell, are ceaseless motion and change. The absorption of new lifeless material, its conversion into hving matter, the removal of that which has ceased to live, comprise a continual succession of actions in winch organization and disorganiza- tion — hfe and death — are miceasing. But in these actions are comprised phenomena of two distinct classes, different in then- very natm-e — physical phenomena, which also occm- in the ex- ternal world ; and phenomena truly vital, the nature of which is not to be so explained. The spontaneity of the actions of the living structure, its self-formation and its power of multiplica- tion, distinguish the simplest organism from the most perfect mechanism of human construction. Life cannot be manifested without the co-operation of matter and the physical forces, but it does not therefore follow, as some have maintained, that the physical force, any more than the matter vrith which it is associated, is the life. Nor do heat, light, chemical affinity, &c., evoke, excite, or increase vital action, but they only accelerate certain physical changes in the lifeless matter which surroimds and protects the living matter that is wdtliin (Plates I and II), in consequence of wliich the passage of the nutrient pabulum through this protecting en- velope, and its access therefore to the hving matter are greatly accelerated. In this way the influence of heat and moistm-e in promoting the development of seeds maybe most easily explained. Again, the life of a complex organism, as usually defined, is made up of phenomena much more complex than those exhibited in the LIFE of a single “ cell.” Instead of commencing the discussion by referring to the changes which take place in the most simple hving organism in the simplest conchtion of its existence, some observers, and especially physicists, have passed 24 OF LIFE. at once to the consideration of the phenomena as they occur in a folly developed animal, or more generally in man himself. As would he supposed, the utmost confosion has resulted. The terms physical and vital have been used indiscriminately, and, gradually, many seem to have convinced themselves that all the changes occurring in living beings are physical. It is not to be wondered at, that those who have taken up a view so obviously opposed to broad facts as this is, should have refrained from attempting to discuss in detail the changes which occm' in a single cell ; or that by some, the existence of the processes of formation, growth, and multipHcation, as they take place in all hving matter, has been almost ignored. These are truly vital phenomena, and occur in h^dng beings only, but the development of heat, Hght, electricity, and the hke, are physical phenomena, whether they occm- in fodng organisms or in inanimate matter. Strange to say, the latter phenomena have been called vital when they occm’ in hfong beings, physical when they take place in the inanimate world; but, as they are essentially the same in all cases, it is obvious that the same terms should be appHed to them. The living or germinal matter alone is the seat of vital actions, while in the lifeless jTormed material physical and chemical phenomena only are in operation. (See Figs, in Plates I to IV). Matter derives vital powers or properties in all instances from a previously existing organism. The vital part of the impregnated egg consists of Ihung matter, which results fr’om living matter belonging to the organisms of the beings that produced it. It manifests a life independent of that of its parents, and undergoes development if the requisite physical conditions are suppHed. Thus is hfe in its mysterious associa- tion with matter transmitted fr-om one foring being to another ; and the hfe of a present generation of animals and plants has its som’ce in that of a previous generation. From a very early period in the liistoi-y of natm’al science, there has been a tendency to ascribe these effects to an imag-i- nary principle, or Entity, possessing powers and properties which (however men may try to impress themselves with a contrary notion) would entitle it to rank as an intelligent agent. It is true, that, according to most of the advocates of this docriine, this power is supposed to be superintended and controlled by HARVEY’S THEORY OF LIFE. 25 the Deity himself, and, by this supposition, they have screened themselves against the accusation of attributing to a creature the powers of the Creator. A little examination of tliis doctrine will shew that it has no pretensions to the title of a theory. Aristotle attributed the organization of animals and vege- tables, and the vital actions exliibited by them, to a series of animating principles {y^v)(ai), differing according to the nature of the organized bodies constructed by them, and acting under the direction of the Supreme animating principle (^vcus). He supposed that each particular kind of organized body had its proper animating principle or and that the variety of the former really depended upon certain original differences in the nature of the latter, so that every distinct species of animating principle would necessarily have its appropriate species of body. Harvey, likewise, assumes the existence of an animating principle^ by which every organism is moulded into shape, out of materials furnished by the parent, and which, pervading the substance, regulates the various functions of its corporeal resi- dence. But, at a subsequent stage of his inquiries, in assigning the blood as the special seat of this principle, he advances another supposition totally at variance with his previous hypo- thesis ; namely, that as, dm'ing the development of the chick in ovo, the blood is formed and is moved, before any vessel, or any organ of motion exists, so in it and from it originate, not only motion and pulsation, but animal temperature, the vital spirit, and even the principle of life itself. So completely biassed were the views of this illustrious man, by his exaggerated notions respecting the nature and properties of the blood ! Nor are many writers, in our own days, free from such vague notions. One who endeavours to introduce a new vital philo- sophy talks about the brain cells being the highest parasites (/) which live upon the life of the blood. And very many persons speak of the blood as distributing “ hfe” to the tissues, as if life were something that could be caused to circulate in solution in a fluid, and be separated from it, and absorbed by this or that tissue ! The celebrated John Hunter, who does not appear to have been acquainted wi^b the views expressed by Harvey, revived 26 hunter’s theory of life. a somewhat similar hypothesis ; and it is cmions that the same fact should have so attracted the attention of both as to have given the first impulse to then speculations. This fact was, that a prolific egg vdll remain sweet in a warm atmosphere, while an unfecundated one will putrefy. The views of Hunter were received with very general favour by Enghsh physio- logists. Hunter ascribes the phenomena of life to a materia vita, diffused throughout the solids and the fluids of the body. This materia vita he considers to be “ similar to the materials of the brain he distinguishes it from the brain by the title “ materia vita diffusa, while he calls that organ “ materia vita coacervata" and supposes that it communicates with the fonner through the nerves, the chorda interrcuncia. And Mr. Abernethy, in commenting upon these views, explains Mr. Hunter’s materia vita to be a subtile substance, of a quickly and powerfully mobile nature, which is superadded to organization and per- vades organized bodies ; and this he regards as, at least, of a nature similar to electncity. Such doctiines need no comment. Muller advocated the presence of an “ organic forced' resident in the whole organism, on which the existence of each part was supposed to depend, and which had the property of gene- rating fi’om organic matters the individual organs necessaiy to the whole. “ This rational creative force is exerted in eveiy animal strictly in accordance with what the natiue of each requires ; it exists already in the germ, and creates in it the essential parts of the futrue animal.” An hypothesis, not dissimilar to the last mentioned, was advocated by Dr. Front, and he supposed that a certain organic agent (or agents) exists, the intimate nature of which is un- knovm, but to which very extraordinary powers are ascnbed. It is superior to those agents whose operations we witness in the iuorganic world; it possesses the power of controlhng and directmg the operations of those inferior agents. “ If,” says Dr. Front, “ the existence of one such organic agent be admitted, the admission of the existence of others can scarcely be "with- held ; for the existence of one only is quite inadequate to explain the infinite diversity among plants and animals." “ In all cases it must be considered an ultimate piinciple, endowed by the Ci’eator ■with a facidty httle short of iutelligence, by means of wliich THEOKIES OF LIFE. 27 it is enabled to construct such a mechanism from natm-al elements and by the aid of natural agencies, as to render it capable of taking ftu’ther advantage of their properties, and of making them subservient to its use.” The hypotheses of Aristotle, Muller, and Prout, and the earlier of those proposed by Harvey, seem all alike ; they assume that organization and life are directed and controlled by an Entity, or Power, “ endowed with a faculty little short of intelligence,” the \lrv)(r) of Aristotle, the animating principle of Harvey, the organic force of Muller, and the organic agent of Prout. What the mechanism may be by which this entity acts, they do not determine ; but it is evidently such as bears no analogy to any knowir natural agency. Its existence is inde- pendent of the organism, for it has directed both the organising process and the living actions of the being. Whence then is it derived ? According to Muller, from the parent, for it exists in the germ, — it derives its powers fi’om the same somce, and its pedigree may therefere be traced to the fii’st created individual of each species of animal or plant. Are we to conclude, then, that organic agents generate organic agents, and transmit their powers to their offspring ? Or must we assrnne, that, for each newly generated animal or plant, a special organic agent is deputed “ to control and direct” its organization, development, and gi’owth? But many phenomena of the utmost importance to living beings, as already shown, are in thefr natm-e physical and chemical, and the laws under which they occur are well mrder- stood. The changes effected in the air and in the blood by respiration, the phenomena of absorption, and, in some degree, those of secretion, are the results of purely physical processes. It is in the highest degree probable that many of the actions of the nervous system are due to physical changes in the two kiuds of nervous matter, substances of complex constitution and high equivalent number, and therefore prone to change. The generation of heat is due to the same chemical phenomenon as will give rise to it in the inorganic world; and electricity is also similarly developed within the body. How entirely de- pendent on physical changes are the senses of vision and hearing, and how completely are thefr organs adapted to the laws of light and sound. 28 THEORIES OF LIFE. The resistance which living animals introduced into the stomach are capable of offering to its solvent powers, and the digestion of the walls of the stomach by its own gastric juice, after sudden and violent death, seemed to denote that the dead animal or dead stomach had lost a something which previously protected them against the influence of the gastric fluid. This sometliing, according to Hunter, was the materia vitoe, according to Prout, the organic agent. But such a result as this can be explained in a very simple way according to the view of structure given in Chapter I. In the textm’e still connected with the body of a livuig animal, and for a certain time after its removal, cmuents of fluid are continually passing through every part of the formed matter or tissue, to and from the masses of germinal or living matter, which are regrdarly distributed through it. This slow circulation of fluid derived from the blood, continues in a definite direction as long as the geiTninal matter remains alive ; and while it continues the tissue cannot be permeated by another fluid. When the germinal matter dies, however, all these cm'rents cease, and any flmd with solvent propei'ties m which the tissue may be immersed, as the gastric juice, soon permeates it and dissolves it. So that the tissue is not pre- vented from being dissolved, by the mfluence of any \fital force or power, but simply by the presence of flmds which permeate it in deflnite directions while it still lives ; the flow of these flmds ceasing as soon as the IHung matter of the tissues dies. Thus it is that a living tissue resists the action of the gastric jiuce, and a dead tissue, or more correctly speaking a tissue, the germuial matter of which has ceased to five, and to and fi-om which cmTcnts have in consequence ceased to flow, is soon dissolved by it. The process of digestion itself is probably only chemical solution. So much for the dependence of life and organization on a controlling and du’ecting entity. John Hunter rejected this doc- trine entfrely, but, as has been stated, went so far as to assmne the presence of a peculiar material of life, which he maintained pervaded the organism and gave wtal properties to solids and fluids. If, however, such a constituent existed in the body, it ought to be demonstrable by chemical or other means. Mr. Abernethy’s doctrine that this materia vitoe was electricity or something aldn to it is opposed to obvious facts. Electricity VITAL STIMULI. 29 requires for its development tlie reciprocal action of different kinds of matter, and it is abundantly evolved in various changes taking place in living beings as the necessary result of the action of ■well known chemical laws. If, therefore, organi- zation and -vital operations were due to electricity, this agent would at once \>q formed by, and govern and direct the formation of, each organism. On the whole, we may conclude, then, that the theory which attributes the phenomena occurring in Hving organisms to the action of physical and chemical forces alone, rests upon no secure foundation, and is indeed controverted by important facts, and that the opposite doctrine, wliich supposes the exist- ence of a materia vitce, or of a subtile organic agent, possessiug powers little short of reason, is equally untenable. We have seen that the phenomena usually termed -sutal really comprise two distinct classes of actions — actions pm’ely physical and chemical, and actions purely vital. The truly vital actions which have been alluded to can only be accounted for by attributing them to the influence of some peculiar power totally distinct in its nature from any form of ordinary force. This is not a power which exists as it were in a concentrated state in the germ, and gradually expends itself as the tissues are evolved, or as the development of the race proceeds, but it is a power which is temporarily associated -with, and influences for a brief peiiod of time, every particle of matter which becomes li-ving. It is a power which may be transmitted infinitely through the infinite multiplication of living matter without any iucrease or diminution in its intensity. As soon as tissue or any of the peculiar compounds result from the changes occurring in this hving matter, its wonderful "vital powers have ceased for ever. Of the so-called vital stimuli. Many suppose that organized bodies being acted upon by certain vital stimuli develop -vital actions. Thus heat is supposed to be the -vital stimxflus which excites the changes resulting in the development of the cluck, light is supposed to excite or stimulate certain changes going on in the vegetable organism, nay, lifeless inorganic matter is regarded as an excitant to increased -vital action in certain cases. A particle of sand falling upon the conjunctiva is followed by increased action as shown by the more rapid growth 30 IRRITANTS AND EXCITANTS. of cells, and increased vascularity. It is said the particle of sand has excited these changes. It is an irritant. But the heat, light, and particle of inorganic matter are probably all perfectly passive. They have not been instrumental in actively exciting changes, but the conditions under which Hfe was canied on before, have been altered, and the alteration is really due to changes not in the living matter, but in the formed lifeless matter by which it is sm’rounded. In consequence it pennits pabulum to flow tow^ards the living matter more readily than before. The h^-ing matter is not excited to live faster, but in consequence of more pabulum having access to it, more matter becomes living within the same period of time. The influence of the excitant is there- fore of a passive character. It does not excite dormant energies or evoke vital actions, but by it some of the restrictions under which the matter lived previously are removed. It is remarkable in these days, when the explanation of phenomena by hypothetical agencies, forces, or powers is assailed on all hands, that even some of those obseiwers who have been specially distinguished for their opposition to any doctrine which admits the influence of vital as distinct from physical force, should pertuiaciously insist, and vdthout attempting to explain by what mysterious means, that a living cell can exert a mochlying influence upon the action of cells arormd it. A cell undergoing increased action is supposed to excite increased action in those cells in its immediate neighbom-hood. For example. Professor Vfrchow' asserts that cells may be incited by a stimidus chrectly applied to them to take up an increased quantity of material. He maintains that every ^dtal action presupposes an excitation or irritation. The illustration he gives for the purpose of explaining what he means by irritation will per- haps enable the reader to form a clearer notion of the views entertauied upon these matters in the present day than a long exposition of the doctiines themselves. “ Suppose thi-ee people were sitting quietly on a bench, and suddenly a stone came and injured one of them, the others would be excited, not only by the sudden appearance of the stone, but also by the injury done to then- companion, to whose help they woifld feel bound to hasten. Here the stone would be the irritant, the injmy the irritament, the help an expression of the irritation called forth in the bystanders.” So that not only have the DIRECTIVE AGENCY — CONSTRUCTIVE FORCE. 31 iimnjiired cells a power of sympathising with their less foidunate companions, but they manifest a deshe to hasten to afford them active assistance in their difidculty ! Such a doctrine is perhaps not more untenable or more rmsupported by evidence than that which gives to insoluble inanimate matter the power of exciting increased action in living things. In every one of the cases in which this increased action occm-s, it may be explained by the increased facihty of access of pabulum to the living matter which is brought about by the so-called hritant or excitant. When a particle of sand, falling upon the conjunctiva, causes the removal of a portion of the outer layers of cells which in the normal state form a smooth membranous investment of uniform thickness, the thickness of tliis tissue protecting the vessels is diminished at the seat of in- jmy, and as a matter of com'se a larger quantity of nutrient matter will permeate the thin layer which remains in a given time. Again it must he remarked that even in the present day many observers admit the existence of some sort of power or force or agency which directs or controls the operation of the various actions going on in different parts of an organism, and is supposed to exert its influence thi-ough cell walls and other tissues, and to be capable of govermng and regulating if not determining, the changes which take place in matter situated at some distance, and in the formation of which it has taken no part. Dr. Carpenter speaks of a power manifesting itself m organisms, which, according to him, exerts upon the cells and other structures, as well as upon the forces concerned in then* production, a control winch may be compared with that exer- cised by the “ superintendent builder who is charged with the working out of the design of the arclntect.” The germ supphes the “ chrective agency ” and a distinction is made between directive agency and constructive force, which last is maintained to be but another mode of heat. Dr. Carpenter also speaks of “germinal canacity,” but this, according to Ixim, is a condition which, although transmitted fi-om one organism to another, has its parallel in the inorganic world, in the fundamental difference in properties which constitute the difference between one substance, whether elementary or compound, and another ! Now those phenomena which are ascribed by Dr. Cai-penter to what is termed Germinal Capacity and Dhective Agency, are 32 RECENT THEORIES OF LIFE. not peculiar to the germ, for there is not a living cell in any organism at any period of hfe in which such phenomena are not manifested in some degree. Moreover, long before any tissue is produced, a mass of living matter may be removed from an organism and canfed far away from the influence of “ directive agency,” and may nevertheless give lise to tissues like those of the organism from which it was derived. Is the dfrective agency capable of being divided and subdivided, each subdivision having an mfluence equal to that of the whole ? If so it can haixlly be compared to the control exercised by the superintendent builder. Mr. G. H. Lewes deflnes life as “a series of definite and successive changes, both of structure and composition, winch take place within an individual without destroying its identity.” It is doubtful if a series of changes is necessary to life ; aU we know is that lifeless matter passes into hiring matter and lives. Living matter exhibits no structure whatever, so that hfe may certainly exist without involving changes of structme. The definition seems to apply to the life of man and the higher animals rather than to hving things generally. There are many masses of living matter which cannot be regaixled as indivi- duals. A wliite blood corpuscle or a pus-corpuscle is alive but it exhibits no structure and we know nothing of its composition while it lives. It cannot be regarded as an indi\'idual unless an uidividiial may consist of millions of indi\dduals, and many of these individuals differ from one another in very many essential pomts. Moreover, when a mass of living matter takes pabu- lum, increases m size and di\ddes into numerous masses, what becomes of its identity? Such words as “individual” and “identity” woifld destroy the value of any definition. Mr. Herbert Spencer proposes to define hfe as “ The definite combination of heterogeneous changes, both simultaneous and successive, in con’espondence vdth external co-existences and sequences.” While this definition does not exclude hfeless machines it is doubtful if it would include many things which possess life although apparently quiescent. This 'writer, how- ever, admits “ the tendency to assume the specific form, inherent in all parts of the organism,” which is pecuhar to living things. He does not, however, attempt to explain the natme of the tendency, or why bring matter alone exhibits it. What causes OF VITAL POWER. 33 the tendency? We know that the particles do actually arrange themselves in a very peculiar and special manner wliich cannot be imitated, and we want to know why they do so. Is it nm-ea- sonable to suppose that they take up then- peculiar and con- strained position in consequence of being influenced by a very peculiar force or power? It is difficult to help calling for an hypothesis to account for the tendency to assume specific form, which is admitted. It has often been suggested that the movements of living beings are due to physical changes, but it must be borne in mind that different classes of movements are observed in con- nection with living beings. Under the head of contractility have been described several phenomena differing in their essential nature. F or instance, the contractihty of muscle, the vibration of cilia, and the oscillations of the spermatozoa, are different in then’ natm’e from the movements observed in the white blood corpuscle, pus and mucus corpuscle, and in many of the lowest and most simple organisms, such as the amoeba, the foraminifera, &c. These and other movements will be considered in Chapter III ; but with reference to the latter class of movement it may be at once remarked that they cannot be accounted for by physics, nor are they to be explained by any chemical changes occurring in the matter itself. They have been referred to osmosis, and to diffusion, but no such movements as these occur when conditions favom-able to diffusion exist, while, even if they had been shown to depend upon these processes, we should still have to learn how the substance coilcerned in these movements was produced. The motion does not at all resem- ble any other kind of motion whatever. The moving power seems to reside in the particles themselves, and if such a moving mass be divided into several small portions, each portion wiU exhibit movements, wlule any very sudden shock, as of electri- city, will at once destroy the capacity for movement, and at the same time cause all those phenomena which we regard as evidence of hfe to cease for ever. It has been assumed that these movements are peculiar to certam cells or bodies, and they have been termed “amoebiform cells” in consequence, but it will be shown that such movements occur in every form of living matter. They are peculiar to living matter, but not to any special organisms. D 34 OF VITAL POWER. It is to be regretted that many wbo have recently vnitten upon the subject of life have not expressed themselves clearly. Not unfi’equently assertions are met with which are incompatible with one another, and even in the writings of the best modem thinkers there is much that is obscure and indefinite. Almost every writer seems to avoid stating in what points the simplest living things resemble, and in what they differ from, inorganic matter, and instead of discussing in the first place the nature and causes of the phenomena occmning in a mass of the simplest living matter, and then proceeding to the consideration of those observed in more complex organisms, the latter are almost exclusively referred to. Veiy different classes of phenomena are often included rmder the same head, and fatile attempts made to account for opposite and antagonistic actions by the same hypothesis. Although we are quite unable to say what sort of force vital power is, to isolate it, to examine it, or to give any satisfactory account of the exact manner in which it exerts its peculiar influence upon inanimate matter, we seem compelled to admit the existence of such a power, because the facts obseiwed cannot be explamed without such an admission. Eveiy attempt hitherto made to account for the vanous phenomena wliich occm' in hving beings by physical actions alone has signally failed, and although some physiologists still hold to this view, they are compelled to ignore those phenomena which they cannot explain, and to discuss only those which occm' after the peculiar (vital) actions have ceased to manifest themselves. They in fact describe as vital acts the destruction of peculiar substances which subtances resulted from the death of hving matter, which occm-red perhaps a long time before. Strange as it may seem, it has been argued that as these unquestionably physical changes were formerly considered to be due to vital forces, physical forces only are concerned in vital phenomena. If those who hold such opinions would follow out the changes which occur throughout the life of the simplest organism, or even single cell, they would probably soon be convinced that sometliing more than physical agency was required to account for the results observed. It is unsatisfactoiy to many minds to be thus compelled to OF VITAli POWER. 35 admit the action of a force or power of the nature of which nothing is yet known, hut it is better to do so than to pretend to be able to give a satisfactory explanation of phenomena which science in its present state is incompetent to account for. Nevertheless an attempt has been made here, to assign to the word vital a definite meaning, and to distinguish vital from physical actions. It has been shown that besides the actions which may be explained upon the same principle as actions taking place in inanimate matter there are changes in every living being, and in every cell, which cannot be so explained or accounted for, which are pecuKar to matter derived from living beings. Whatever the real nature of these changes may be, they cannot result fi’om the action of any ordinary force, nor do they obey the same laws. The seat of these peculiar actions has been pointed out, and has been distinguished from the seat of the physical and chemical changes. It will be remarked that the view of the vital processes advocated in these pages differs fi’om others in the very essential point, that the assumed vital power is supposed to influence only particles of matter with wliich it is associated, and its association with matter is but temporary. The power bears neither a qualitative, nor as far as can be at present proved, a quantitative relation to the matter. It cannot act upon matter at a distance, nor upon the same particles for any length of time. The particles are influenced by it, but soon pass from its control. If their place is not soon succeeded by new particles, vital action must cease, but as long as new particles come iuto con- tact with those which live already, the action is transmitted, and so on for ever (not simply transferred from particle to par- ticle so that one gains what another has lost). The direction and control exerted, are exerted upon particle after particle. The various particles are not placed in this or that place by a controlling power, ordering and mfluencing all, but each particle for the time being seems to direct and control itself, and its power is transmitted to new particles -without loss or diminution in intensity, and sometimes -with actual increase. Certain physical conditions interfere with the manifestation of this power. The action of air, and various external cncum- stances, cause death. In fact it would seem that inanimate matter to become li-vdng, must come into contact with that whieh D 2 36 OF THE FORMS OF LIVING BEINGS. lives, only in exceedingly minute portions at a time. If much lifeless matter comes into contact with living matter, the latter dies. Death is simply the cessation of the vital changes, and is due alone to the action of physical conditions. Physical forces invariably cause death, but they cannot give rise to life. Ordi- nary force and life seem to be opposed. OF THE DIVERSITY OF FORMS OF LIVING BEINGS. How shall we explain the strange process of organization, in the production of that infinite diversity of forms, that “ insatiahle variety of Nature,” which is so conspicuous in the vegetable and animal kingdoms ? The view that has been most generally entertained is, that the Ihfing matter of each species of animal or vegetable was created to propagate after a certain fashion, and after that only ; the living matter of which these organisms consist in the early stages of development, must have the power of evolving the adult tissues of animal or plant of its own species only ; the simple volvox develops, fi.'om its iateiior, matter which becomes volvoces ; and the cell which foians the important part of the ovmn of the elephant or the mouse, is able, by an inherent power of multiplication, to evolve the tissues and organs peculiar to each of those animals respectively. The particular endowments of the organic matter, composiug the various tribes of animals and plants, are transmitted fi'om parent to offspring. But, as is well known, they admit of certain modifications under the influence of chcumstances afiect- ing the parents, as is proved both in the animal and vegetable kingdoms in the production of hybrids, and of forms difiei’ing in certain chai'acters from either parent. “ Two distinct species of the same genus of plants,” says Dr. Lindley, “ wiU often together produce an offspring intermediate in character between themselves, and capable of performing all its vital functions as perfectly as either parent, with the exception of its bemg imequal to perpetuating itself permanently by seed ; should it not be absolutely sterile, it vfill become so after a few genera- tions. It may, however, be rendered fertile by the application of the pollen of either of its parents ; in which case its ofispiing assumes the character of the parent by which the pollen was supplied.” The same thing precisely occurs among animals, and the mrde, produced by the miion of different species, is OF THE FORMS OF LIVING BEINGS. 37 incapable of breeding witb another mule, although it may pro- duce offspring with an animal of the same species as either of its parents. Various facts show that physical agencies exert an important influence in modifying organic development. The most potent cause of these changes has been chmate ; but particular cus- toms and usages, connected with the uncivflized state, have not been without their influence. Climate also produces con- siderable modifications in the size and other characters of the lower animals. The very striking alterations in character which are known to result from the influence of such external conditions has led many observers to suspect that still more important modifications may really be due to these causes alone, and that possibly two or more different species may have been produced by the action of dissimilar physical conditions upon the descendants of different members of the same original stock. It is true that the mind attempts in vain to realize the direct im- mediate creation of a living being out of inorganic matter, and it is therefore not to be wondered at that from time to time strong opposition to the old view, regarding the origin by sepa- rate special creations, of all the countless beings which surround us, should have arisen, or that attempts shoifld have been made to substitute for it some theory which should account satis- factorily for the phenomena, without the necessity of accepting a dictum, or adopting an assumption which cannot be proved. But it is remarkable that some of the strongest opponents of the old account of the creation, experience no difficulty in accepting the doctrine of the spontaneous or fortuitous origin of organic particles, and their aggregation to form living organisms. No one attempts to explain how the atoms composing the first living particle, brought themselves together, any more than the natm’e of the forces associated with the inorganic atoms prior to their concom’se, or the condition of the matter at a still earlier period than this, to say nothing of the origin of the matter itself. Of late years the idea has been gaming ground that all the different plants and animals which exist, and which have existed from the beginning, have resulted entirely from the constantly modifying influence of continually altering external circum- stances upon what was originally a very simple form. And 38 OF THE ORIGIN OF SPECIES although the facts of the case compel the admission of inherent forces, acting as it were, from within living beings, the internal changes themselves have been attributed to the influence of pre-existing external conditions. The oi’igm of a single, growing, multiplying mass of form- less, structureless, organic matter being admitted, it is said that comitless modifications in structm’e and function of the masses resulting fi’om it, and thefr descendants, are easily explained by the modifying influence of the different external conditions to which these must be subjected as the numbers increased, and necessarily became removed from the spot where the fii'st concourse of inorganic particles, with its mysterious result, occm-red. Of all the views ever advanced in this direction, those of Mr. Darwin, “ On the Origin of Species, by the process of Natiu’al Selection,” published in 1859, have received the warmest support, and although we cannot attempt to give more than a very rough outline of this view, the hypothesis is so full of interest, and is so fertile of investigation, that we shall draw attention to it m few words, and refer the reader for further information to the work itself. The offspring of hvuig beings, it has been tiudy obseiwed, exhibit a tendency to inherit the characters of those from which they sprang. This is termed atavism. But there is also a tendency in the offspiing to vary in certain particulars from the original stock, and an alteration having occun’ed is transmitted to the descendants. Now if it so happens that any of these modifications fi-om the primitive t}’pe give advantages to their possessors over those which have them not, it follows that in the struggle for existence individuals of a species which vary in a way advantageous to themselves, possessing perhaps greater facilities for obtaining food, or greater power of resisting external destructive agencies, will sm-vive and multiply, wliile thefr less fortunate fellows will gradually die out. In this way the former Avill be “ natmally selected ” fr’om the latter, and by the strong tendency to inlieritance, any variety thus selected will propagate its newly-acqufr’ed form. The tendency to the production of ncAv characters, and the tendency to transmit these to the descendants, working through infinite time, must, it is argued, produce great differences in the character of the various BY NATURAIi SELECTION. 39 organisms descended from the same primary stock. The modi- fying influences of external circumstances, chmate, food, tem- perature, acting through inflnite time, and varying remarkably in places remote from one another, and in the same places, in successive epochs, will undoubtedly account for changes in character. Peculiarities thus arising, it is obvious may be further developed or diminished, according as the conditions by which they were induced persist, or become replaced by new ones. Although Mr. Darwin himself does not attempt to ex- plain how many of these pecuharities arose, some seem to have regarded them as the result of accident occm-ring at a very early period of embryonic hfe, while many, who do not seem to admit that the supposed original simple hving form, or foians, were endowed with any internal powers whatever at the time of their origin, attribute them to the influence of external cfr- cumstances alone. By selective breeding, in ceiflain cases, for many generations, very difierent foi-ms undoubtedly result, so difierent, indeed, that a superflcial observer might consider them at least as distinct as many creatimes, admitted upon all hands, to be truly distinct species ; and if the same modifying causes contiuued, it is difficult to conceive to what extent the modifications might proceed. It is m-ged there is no limit to the continuance and augmentation of changes thus induced. But all the instances hitherto adduced differ from true species in one very important particular. Members of different species seldom breed with one another, and in the few instances in which this does take place, the resulting mules or hybrids, if they are not absolutely barren, never breed with mules of the same kind, so that there is this most important fact opposed to the application of conclusions arrived at from observations upon varieties of one or more domestic species to the production of the various and un- doubtedly distinct species of annuals and plants now existmg. The offspring of mere varieties is fertile, and they breed one with another, and there seems no limit to the varieties that may be produced in certain cases, but for this reason they must be considered varieties and not species. It must not, however, be forgotten that the tendency to vary under altered conditions is not manifested in very many species of existing animals. The slightest alteration in external 40 OF PHYSIOLOGICAL DIFFERENCES. conditions, at once destroys certain animals and plants. They do not live long enough to be modified by physical agencies. The capacity for existence, mider a variety of different condi- tions, and tendency to gradual structural alteration, in conse- quence, seems indeed to be limited to comparatively few of the existing species of animals and plants. It would appear as if the life of the great majority of living beings was almost dependent upon the persistence of the particular external circumstances under wliich they happen to live. Moreover, the degree of change which actually occm’S in different animals, which are capable of bemg domesticated, is very great. A famihar and very striking example occms in the case of cats and dogs. How few the varieties of the former, and how comparatively slight the variation which does occur as compared with the latter. The organization of the cat is, as it were, much less plastic than that of the dog. Looking at the facts broadly and generally, there undoubtedly seems much in favom’ of l\Ir. Darwin’s view, but when we come to consider the structm'al changes which must occur in a single organ of one of the higher animals, it is more difficult to accept his conclusion. Changes occurring in each stage of develop- ment of a single organ seem continuously associated with others which occuiTed during those of a prior stage, and the changes affecting every part of one organism appear to be due to some general cause acting upon the whole from the very first. Crea- tm’es, undoubtedly very closely alhed to one another, differ fi-om each other, not in one or two, but m a vast number of charac- ters. Although they may be much ahke m form, and closely allied zoologically, they exhibit physiological differences of the most remarkable kind; and although there is some general accordance in the life history of distinct species, the differences of detail are far more striking and remarkable than, and quite as difficult to account for as, the general resemblances which have attracted notice. In that temporary state in which all matter exists before it assumes the structine and composition peculiar to the difterent tissues of different living beings, no differences can be detected by any means yet knovm. The living matter of an adult tissue could not be distinguished from that of an embiyo. Xor could the living matter of the highest brain cell of man be distin- OF ANATOMICAL DIFFERENCES. 41 guislied from that concerned in the production of the lowest living structure. And yet how different are the results of the Hfe of the two? This difference would he more readily accounted for upon the hypothesis of the existence of some marvellous original difference in the power of the different kinds of living matter, than by the action of the different external circumstances under which descendants from one and the same stock have passed, or upon the h}^othesis of the inherent ten- dency to vary. Can we accept the conclusion, that there was no well-defined difference at an early period of the world’s his- tory between the hving forms then inhabiting the earth, until we have studied in detail the structure, mode of development, and complete life history of two existing species of simple organization, which are closely allied to one another? As yet we have no history of the life of any living thing which at all approaches completeness. It should be stated that, according to the theory, as accepted by many, something which amounts to a special creation is admitted to have occurred in the case of the first living molecule. The argument is supposed to com- mence from this point. The anatomical differences between corresponding tissues of closely allied species are often so distinct that the anatomist familiar with them could distinguish one from the other. For example, it would be difficult to state in few words the differ- ences between the unstriped muscular fibres of the bladder of the hyla, of the common frog, and of the newt, and yet there is a recognizable difference, and corresponding differences can be demonstrated in other textures, if a comparison be carefully instituted. So also with regard to the chemical composition of the corresponding sohd matters, fluids, secretions, &c., of closely allied animals, remarkable differences are observed as may be demonstrated by a careful examination of the blood, bile, or urine, for example. Such differences affecting the minute structure, and chemical composition, of every part of the organism of creatmes closely allied, are strong arguments in favour of the doctrine of the independent origin of distinct species ; for it is scarcely reasonable to assume that any diver- gence in a few particulars, from the general characters of the common original stock, should be accompanied by, or should necessarily involve, a change in all these points, rmless such 42 OF PLANTS differences can be demonstrated to have occurred in the varieties of existing species ; but tliis is a subject which has not yet been touched upon by Mr. Darwin or by those who have embraced his -snews. Animals may differ in many charac- teristics but still retain the most striking resemblance in all essential biological characters, or they may resemble one another in external form and general characters but differ most mate- rially in internal stmctm-e. If a careful comparison sho\ild be made of everything in connection with the formation of structures thi'oughout the hfe of closely allied but distinct species and between the most different varieties of the same species, it is probable that such essential points of difference in the one case, and agreement in the other, would be demonstrated as would suffice to convince the warmest advocate of Mr. Darvun’s views that more minute investigation was required before his doctrine, as appHed to the origin of all species, could be admitted to rest upon a satisfactory basis. OP PLANTS AND ANIMALS AND OF THE FUNCTIONS. It is impossible to define precisely a boundary between the vegetable and animal kingdoms, and any attempt to lay do^vn characters which shall distinguish plants from animals m eveiy case must fail. The lowest animals are said to exliibit so much of the plant nature that natm-ahsts are as yet undecided as to the true location of some species. The common sponge, for instance, a short time since was claimed for each kingdom, but there can now be no doubt of its animal natm-e. The important phenomena of plant and animal hfe are, in fact, the same in their essential natm’e. Still it will be advantageous to recomit briefly some of the most important general characters in which the fully developed animal differs fr’om, or agrees with the fully developed plant. The first step in the nutritive functions of both plants and animals, is to form a fluid, which contains aU the elements necessary to nomlsh the various textm'es, and to supply materials for the secretions. This fluid is, in plants, the sap ; in animals, the blood. In both classes of beings a process of absorption precedes the full development of the nutritive fluid : it is by this means that AND ANIJIALS. 43 material is obtained for its formation. Witbin the plant or animal it becomes more completely elaborated. In plants, the absorption takes place by the spongioles of the roots. A fluid, ah-eady prepared in the soil, — ^water, holding in solution carbonic acid and various mineral substances, — passes through them into the vegetable organism. In animals the food experiences much change, and a more or less elaborate process of digestion takes place, before a fluid is formed, capable, when absorbed, of furnishing the materials of the blood. Plants, fixed by then' roots in the soil, imbibe from it their nutriment. A nim als, obtaining food from various sources, introduce it into a digestive cavity, where it is prepared for absoi-ption. The presence of a digestive organ, or stomach, is charac- teristic of animals. The only instances in which a similar organ may be supposed to exist in the vegetable kingdom, are to be found in those remarkable modifications of leaves, called pitchers {gscidid) in Nepenthes, Sarracenia, and Dischidia. In the last two plants, these organs certainly serve to retain and dissolve the bodies of insects in the fluid which partially fills them : in Sarracenia, according to Mr. Emmett, the fluid con- tained in the pitchers is very attractive to insects, which, having reached its surface, are prevented from retmning by the direc- tion of the long bristles that line the cavity. The dissolved food is then absorbed into the plant. On the other hand, the animal kingdom affords some excep- tions to the presence of a stomach. In such animals, the absoiption of nutrient fluid takes place by a general sm-face. Many of the infusoria are destitute of a stomach. A parasite of the human body, the Acephalocyst, also derives its nutriment by imbibition thimugh its walls. A famihar example is the Acephalocystis endogena, or pill-box hydatid of Hunter. It con- sists of a globular bag, closed at all points, containing a limpid fluid, capable of growth, developing upon the inner surface of the sac little organisms, also nomished by absorption, the echinococci, which are the early stage of development of what was once supposed a distinct species, the tapewoimi. Some difference may be noticed as regards the nature of the food in animals and plants. The former derive their nutiiment entirely from the organized world, unless, indeed, we suppose 44 OF PLANTS AND ANIMALS. that the nitrogen absorbed in respiration contributes to their sustenance. Plants appropriate inorganic elementary matters -for food, as carbon, carbonic acid, ammonia, &c. “ Inorganic matter,” says Liebig, “ affords food to plants ; and they, on the other liand, yield the means of subsistence to animals. The conditions necessary for animal and vegetable nutrition are essentially different. An animal requires for its development, and for the sustenance of its vital functions, a certain class of substances which can only be generated by organic beings possessed of life. Although many a nim als are entbely carni- vorous, yet their primary nutriment must be derived from plants ; for the animals upon which they subsist receive their nourishment from vegetable matter. But plants find new nutritive material only in inorganic substances. Hence one great end of vegetable life is to generate matter adapted for the nutrition of animals out of inorganic substances which are not fitted for this purpose.” The nutrient fluid, however formed, is distributed through- out the textures of the plant, or animal, by vital or physical forces, or by the junction of both; and the function, by which this is effected, is called Circulation. In plants, this function is very simple, and is perfonned without the agency of a pro- pelling organ, circcflating tlu’ough capillaiy vessels wliich exist in every part of the tissues of the plant. In some plants, the fluid is foimd to circulate, or rotate, vuthin the interior of cells, as in Chara and Vallisneria., the fluid of one cell not communi- cating with that of the adjacent ones ; or to pass up from the spongioles in an ascending cm'rent, and to descend in another set of vessels. In the greatest number of animals, a propel- ling organ, a heart, is the main instrument in the distribution of the blood. In animals, then, there is a true cfrciflation ; the fluid setting out from, and returning to, the same place. In many sunple animals and plants, however, there is no cfrcula- tion at all in special vessels, but the tissues are uomlshed by imbibing the elements of nutrition from the mechum in which they are immersed. The presence of atmospheric air is necessary to the existence of all organized beings. The air both passes by endosmose into their nutrient fluids, and receives from them certain deleterious gases developed in their interior. The function, by which the OF WILL. 45 fluids are thus aerated, is called respiration. In plants, the intro- duction of atmospheric air conveys nutriment to the organism ; carbonic acid and ammonia are thus introduced ; the former is decomposed, its carbon is assimilated, and its oxygen is ex- changed for a fresh supply of atmospheric air. As the agent in the decomposition of the carbonic acid is light, it is evident that the generation and the evolution of oxygen can take place only in the day-time. Consequently, during the night, the carbonic acid, with which the fluids of the plant abound, ceases to be decomposed, and is exhaled by its leaves. Hence, plants exhale oxygen in the day-time, and carbonic acid at night. In animals, carbonic acid accumulates in the blood during its circiflation ; and, when the atmosphere is brought to bear upon the capillary vessels containing the blood charged with this gas, a mixtm-e takes place through the delicate walls of the vessels, the atmospheric air passing in, and carbonic acid, with nitrogen and oxygen, in certain proportions, escaping. Thus the evolution of carbonic acid, and the absorption of oxygen and nitrogen, are the characteristic features of respfration in animals. It is highly interesting to notice, how plants are thus subservient to the well-being of animals, in the respiratory func- tion, as well as in preparing nutriment for them. By thefr respfration they serve to pmdfy the air for animals ; for, in absorbing the carbonic acid from the atmosphere, they are con- tinually depriving it of an element which, if suffered to accu- mulate beyond certain bounds, would prove destructive to animal Hfe. From the fluids of animals and plants, certain matenals are separated by a singrdar process, nearly allied in its mechanism to nutrition, and called the function of secretion. The secreted matters are various, and have very different ends : in some cases being destined for some ulterior pm-pose in the economy; in others, forming an excrement, the continuance of which in the organism would be prejudicial to it. The function, which has for its object the propagation of the species, generation, presents many points of resemblance in plants and animals. In the former it is cryptogamic, or phanerogamic ; in the latter, non-sexual or sexual. In the phanerogamic and sexual, the jimction of two kinds of matter fru-nished by the parents is necessary to the development of fertile ova. In the 46 OF MIND. cryptogamic and non-sexnal generation, the new individual is developed by a separation of particles from the body of the parent, by which the new formation is nourished rmtil it has been so far matured as to be capable of an independent existence. The functions, hitherto enumerated, may be called organic, as being common to all organized beings ; but there are others which, as being pecuhar to, and characteristic of, a nim als, may be appropriately designated animal functions. The prominent characteristic of animals is the enjoyment ot volition or will, wliich impHes necessarily the possession of con- sciousness. Our knowledge of the share which consciousness and tlie will have m the production of certain phenomena of animal life, is derived from the experience which each person has of his own movements, and a comparison of them with the actions of inferior annuals. We are conscious that, by a certain effort of the mind, we can excite our muscles to action ; and when we see precisely sundar acts performed by the lower creatm’es, vdth all the marks of a pm’pose, it is fafr to infer that the same process takes place hr them as in om-selves. J\Ioreover, we learn by experience, that injury or disease of the neiwes, which are distributed to our muscles, destroys the power of accom- phshing a ceriain act, but does not affect the desfre or the wish to perfoiTQ it : and experiments tell us that the di^dsion of the nerves of a limb m a lower animal destroys its power over that member ; wliile its ineffectual struggles to move the Hmb obviously mdicate that the Avdl itself is not affected by the bochly iujmy, though its powers are limited by it. Agaui, certain external agents are capable of affecting the mind, thi’ough certain organs, thus giving rise to sensations. Light, sound, odom’, the sapid quahties of bodies, thefr various mechanical properties, hardness, softness, &c., are respectively capable of producmg coiTesponding affections of the mind, which experience leads us to associate vdth their exciting causes, and which may be agreeable, and produce pleasure, or the reverse, and give rise to pai?i. In a similar way to that by which we leam that the will stimulates om- muscles thi-ough the neiwes, we can ascertain that the nerves are the channels through which our sensations also are excited. “ Certain states of otu bodily organs are OF INSTINCT. 47 directly followed by certain states or affections of our mind; certain states or affections of oru mind are dii'ectly followed by certain states of our bodily organs. The nerve of sight, for example, is affected in a certain manner; vision, which is an affection, or state of the mind, is its consequence. I vdll to move my hand ; the hand obeys my will so rapidly, that the motion, though truly subsequent, seems almost to accompany my volition, rather than to follow it.”* And in all the inferior animals, possessed of like organs, there can be no doubt that sensations may be produced similar to those which arise in the human mind. In many of them, indeed, the sense of sight, hearing, or smell, seems much more acute than in man, and affords examples of a beautiful and pro- vidential provision for the peculiar sphere which the creatines are destined to occupy. The unerring precision of the beast or bird of prey in pouncing upon its victim — the accinacy with which the hound tracks by its scent the object of its pursuit — or the quickness with which most of our domestic animals detect sounds and judge of then direction, are familiar illustrations of the superiority of these senses in animals whose general organi- zation is inferior to that of man. There are few animals, however small and insignificant, in which we cannot recognize evidence of a controlling and direct- mg will. But even in those few, in which vohmtary movements are not distinctly to be discerned, the presence of a special system of organs, with which m the higher animals vohtion and sensation are associated, namely, a nervous system, serves as a characteristic distiaction fi’om plants. A power of perception, and a power of volition, together constitute our simplest idea of mind; the one excited through certaiu corporeal organs, the other actiug on the body. Thi’oughout the greatest part of the animal creation mental power exists, ranging from this its lowest degree — a state of the bhndest iustmct, prompting the animal to search for food — to the docility, sagacity, and memory of the brute ; and to its highest state, the reasoiung powers of man. The phenomena of nfind, even in their simplest degree of development, are so distinct from anything which observation teaches us to be produced by material agency, that we are * Dr. Brown. Pkilosophy of tlie Human Mind, p. 106. 48 OF ANATOmCAL INVESTIGATION. bound to refer them to a cause different from that to which we refer many of the phenomena of living bodies. Although asso- ciated with the body by some unknown connecting hnk, the mind works quite independently of it ; and, on the other hand, a large proportion of the bodily acts are independent of the mind. The immortal soul of man, divince particula aurcB, is the seat of those thoughts and reasonings, hopes and fears, joys and sorrows, wliich, whether as springs of action or motions excited by passing events, must ever accompany him through the chequered scene in which he is destined to play his part during liis earthly career. Although the animals, inferior to man, exhibit many mental acts in common with him, they are devoid of all poAver of abstract reasoning. “ Why is it,” says Dr. Alison, “ that the monkeys, who have been observed to assemble about the fires which savages have made in the forests, and been gratified by the warmth, have never been seen to gather sticks and rekindle them when exphmg? Not, certainly, because they are inca- pable of understandhig that the fire which Avarmed them for- merly will do so again, but because they are incapable of abstracting and reflectmg on that quality of wood, and that relation of wood to fires already existing, Avhich must be com- prehended, in order that the action of rencAA'ing the fii'e may be suggested by what is properly called an effort of reason.” Yet animals are guided by instinct to the performance of cer- tain acts Avhich have reference to a determinate end : they con- struct various mechanical contrivances, and adopt measures of prudent foresight to proAude for a season of want and dififculty. None of these acts could be effected by man A\uthout antecedent reasoning, experience, or histruction. But animals do them Avithout previous assistance ; and the young and inexperienced are as expert as those winch liaA^e frequently repeated them. “ An animal separated immediately after its birth from all com- munication with its kind, aauII yet perform every act pecuhar to its species in the same manner, and A\uth the same precision, as if it had regularly copied them example, and been mstructed by then- society. The animal is guided and govemed by this pidn- ciple alone, by this all its poAvers are hmited, and to this all its actions are to be idtimately referred. An animal can discover nothing ucav ; it can lose nothing old. The beaver constmcts OF HUMAN AND COMPARATIVE ANATOMY. 49 its habitation, the sparrow its nest, the bee its comb, neither better nor worse than they did five thousand years ago.” In plants there is no nervous system ; there are no mental phenomena. The motions of plants correspond in some degree with those movements of animals in which neither conscious- ness nor will participate. Some of the movements undoubtedly result from physical changes produced directly in the part moved. Amongst the most interesting examples are those of the Mimosa pudica, the Dionaa muscipula, and the Berberis. But movements of another kind, as the movements in the interior of the cells of Vallisneria Tradescantia, &c., depend upon changes occurring in the living matter, the natm’e of which is not yet understood. These movements will be discussed in another place. OF ANATOMICAL INVESTIGATION. It is the province of physiology to investigate the manner in which the fnnctions of living beuigs a.re carried out ; and this investigation natmully involves the examination of their mechanism, of the chemical constitution, and of the properties of then- component textm’es. The study of anatomy must always accompany that of physiology, on the principle that we must understand the construction of a machiae before we can comprehend the way in which it works. The history of phy- siology shows that it made no advance until the progress of anatomical knowledge had unfolded the structure of the body. There is so much of obvious mechanical design in the intimate stractm’e of the various textures and organs, that the dis- covery of that structure opens the most dh-ect road to the determination of their uses. That kind of anatomy which investigates structm-e with a special view to function may be properly designated Physiological Anatomy. In investigating the functions of the human body, the physiologist cannot do better than follow the instructions laid down by Haller in the preface to his invaluable work, “ Ele- menta Physiologic Corporis Humani.” The first and most important step towards the attainment of physiological Imowledge is, the study of the fabric of the human body. “Et primum,” says Haller, “cognoscenda est fabrica corporis humani, cujus penfe infinite partes sunt. Qui E 50 OF ANATOMICAL INVESTIGATION. physiologiam ab anatome avellere stucluenmt, ii certfe mibi viclentur, cum mathematicis posse comparari qui macbinae alicujus vires et fiinctiones calculo exprimere suscipiunt, cujus neque rotas cognitas babent, neque tympana, neque mensuras, neque materiam.” A knowledge of human anatomy alone is, however, not sufficient to enable us to form accurate views of the functions of the various organs. Before an exact judgment can be formed of the functions of most parts of living bodies, Haller says, that the constniction of the same part must be examined and com- pared in men, in various quadrupeds, in birds, in fishes, and even in insects. And, in proof of the value which attaches to this knowledge of comparative anatomy, he shews how, from that science, it may be determined that the liver is the organ which secretes bile ; and that the bile found in the gall-bladder is not secreted by, but conveyed to, that organ ; for no animal has a gall-bladder without a liver, although many have a hver with- out a gall-bladder ; and, in every case where a gall-bladder is present, it has such a communication with the liver, that the bile secreted by the latter may be easily transfen’ed to the former. “Vides adeo,” he adds, “bdem hepate egere, in quo paretm, vesicula non egere, non ergo in vesicida nasci, ex hepate vero in vesiculam transu’e.” And Cuvier has happily compared the examination of the comparative anatomy of an organ, in its ga-adation fi-om its simplest to its most complex state, to an experiment which consists in removing successive portions of the organ, with a view] to determine its most essential and important part. In the animal series we see this experiment perfonned by the hand of nature, wdthout those distmbances which mechanical violence must inevitably produce. We thus learn, fi-om comparative anatomy, that the vestibule is the fundamental part of the organ of hearing ; and that the other portions, the semicircular canals, the coclilea, the tympanmn and its contents, are so many additions made successively to it, according as the in- creasing perceptive powers of the animals rendered a more delicate acoustic organ necessary. In a similar manner we learn, that one portion of the nervous system, in those animals in which it has a definite arrangement, is pre-eminently asso- ciated with the mind, and is connected with, and presides PHYSIOLOGICAL ENQUIRIES. 51 over, the other parts. This organ, the brain, is always situate at the anterior or cephalic extremity of the animal, and with it are immediately connected the organs of the senses, the inlets to perception. We soon find that the brain exhibits a subdivision into distinct parts, and of the relative importance of these parts, and their connexion with the organs of sense, and with the intellectual functions, we derive the most im- portant information from the study of comparative anatomy. Haller fiu’ther assigns the examination of the living animal as a valuable aid in physiological research. Many obscm*e points have been elucidated by experiments on living animals, and discoveries have been made wliich have greatly contributed to the progress of physiology. Very useful knowledge may be derived from observing the play of certain functions in hving animals, or in man himself, — contrasting them in various indi- viduals, and noting the effects of age, sex, and temperament, and ascertaining the influence which other conditions, natural or artificial, may exert upon them. The investigation of disease, both dm’ing Kfe and after death, is of great value in enabling us to appreciate the action of an organ in health. If, for example, as Haller remarks, a particular function be ascribed to a certain part, how can there be a more favourable opportunity of testing the accuracy of such a doctrine than by the examination of a body in which that part was affected with a disease, of which the previous history was known ? If the function in question had been vitiated, or destroyed, it may be fauly presumed to have had its seat in the diseased organ. Nothing has contributed more largely to determine the functions of particular nerves, than exact histories of the symptoms during hfe, in cases in which they had been found, after death, in a diseased condition. IMPORTANCE OF ANATOMY AND PHYSIOLOGY TO THE ADVANCE OE MEDICINE AND TO ITS STUDY. A correct physiology must ever be the foundation of rational medicma He who is ignorant of the proper construction of a watch, and of the natm-e of the materials of which it is made, could not find out in what part its actions were faiilty, and would therefore be very unfit to be entrusted with repahing it. In medicine, the fii'st step towards the cure of disease is to fin d E 2 52 IMPORTANCE OF PHYSIOLOGY out wliat the disease is, and where it is situated {diagnosis). Without a knowledge of the offices which various parts fulfil in the animal economy, om’ search to deterroine what organ or fonction is deranged must be most vague and indefinite. Patho- logy is the physiology of disease ; and it is obvious, that no pathological doctrines can command confidence, which are not founded upon accurate views of the natm’al functions. It is also certain that improvements m pathology must foUow in the wake of an advancing physiology. The practice of medicine and sm’gery abounds with examples illustrating the immense benefits w'hich physiology has con- ferred upon the healing art. The gi'eat advance which has been made in the pathology of nervous diseases, is mainly owing to the discoveries of Bell, and more recently to the researches of Marshall Hall, Bernard, Brown-Sequard, and others, upon the fmictions of various neiwes, and the general doctrines of nervous actions. We may instance the case of the facial nerve — the portio dma of the seventh pair. It was sup- posed formerly that tins neiwe was the seat of that painful disease, called tic-douhureux, and section of it has been per- formed for the relief of the patient. It is now known that this nerve could not be the seat of a veiy painful disease, for it is itself, in a very gneat degnee, devoid of sensibihty. It need hardly be added, that the operation is discarded. The dangerous disease, to which many children have fallen victims, laryngismus stridulus or crowing inspiration, although admirably described by practical physicians, was never properly understood until the functions of the laiyngeal neiwes were clearly ascertained, and until it had been shown that spasmodic actions maybe excited bymitation of a remote part, or through a stimulus reflected from the nervous centre. It is now known, that this disease has not its seat in the larynx, where those spasms occur which excite so much alarm for the fate of the httle patient ; but that it is an irritation of a distant part, which derives its nerves fi-om the same region of the cerebro- spiual centres as does the larynx, — that the afierent nerves of that part convey the hritation to the centre, whence it is reflected by certaui efferent nerves to the muscles of the larynx. The important obseiwations made of late years upon the TO MEDICINE. 53 action of the sympathetic nerve npon the blood-vessels has already thrown great light upon the nature of numerous patho- logical changes, especially those complex phenomena which constitute what in the higher animals and man are termed con- gestion and inflammation. The recent researches upon the arrangement of, and course taken by, the nerves in the central organs conducted by Stilling, Lockhart Clarke, and others, are likely to lead to most important conclusions with reference to the actions of the brain and cord. The accm-ate diagnosis of diseases of the heart rests entirely upon a correct knowledge of the physiology of that organ. This improvement in medicine may be said to date from the time of Harvey, for he was the fh’st who clearly expounded the mechanism of the central organ of the ckculation. But the application of auscultation to the exploration of the sounds developed in its action, and the correct interpretation of those sounds in health by the experiments and observations of the last few years, have almost completely removed whatever difficulties stood in the way of the detection of cardiac maladies. We are not less indebted to the illustrious Englishman who discovered the cu’ciflation of the blood, for having paved the way to a rational treatment of anemismal and womided arteries by the modern operation of placing a ligature between the heart and the seat of the disease or injury. “ The active mind of John Hunter,” says Mr. Hodgson, “ guided by a deep insight into the powers of the animal economy, substituted for a dan- gerous and unscientific operation, an improvement founded upon a knowledge of those laws which influence the cu’culating fluids and absorbent system ; and few of his brilliant discoveries have contributed more essentially to the benefit of mankind.” THE USE OE THE MICEOSCOPE. F or exploring the structure of the various textures, and the relation of the anatomical elements of the body to one. another, the Microscope is necessary. The great unprovements which modern opticians have accomplished, not only in the dioptric but also in the mechanical adjustments of this mstrument, render it an invaluable adjuvant in physiological research. We shall have frequent occasion in the following pages to 54 THE USE OF THE j\HCROSCOPE refer to anatomical analyses, effected by tbe microscope, of the utmost value to tbe knowledge of function. New means of preparing tissues, and the use of powers magnifying upwards of 1,000 diameters, have enabled us to investigate details with a precision and to an extent wliich not long since was con- sidered impossible. It may, however, be remarked, that, as the sources of fallacy are numerous even vdth the best instruments, more depends upon the observer himself, in this kind of investi- gation, than in almost any other. The great impediment to deriving correct inferences from microscopical obseiwations has arisen from the discordance, too apparent, m the nan’ations of different observers. This dis- cordance has been the result of a twofold cause ; namely, imperfection of the instruments, and the very unequal quahfica- tions of different observers. The former cause is now almost completely removed ; the latter must remam while men imper- fectly appreciate their ovm abilities for particular pm-suits. Many observers have placed too much rehance upon minute and elaborate description of what they have seen, and have not been at the pains to give carefrd representations of the stnictiue as it appeared to them. Others, although they have given di’awings, have executed them very carelessly, and have omitted to di’aw them to a scale, so that they cannot be compared one with another, or with the drawings of other observers. Again, the system of one anatomist endeavouring to refute the statements of another by researches upon a different object, conducted upon a different principle, only serves to increase the confusion already existing, and to post- pone to a more distant period the definite settlement of most important elementary principles. If anatomical obseiwers would select the same organisms for study, and make then drawings as accinately as possible to a fixed scale, many of the ques- tions upon which they are now at issue would soon be de- termined. To make microscopical observation really beneficial to phy- siological science, it should be done by those who possess two requisites : an eye, w'hich practice has rendered famihar with genuine appearances as contrasted with those produced by the various aberrations to which the rays of hght are liable in then passage thi’ough highly refi'acting media, and which can quickly IN PHYSIOLOGICAL ENQUIEIES. 55 distinguish the fallacious from the real form; and a mind, capable of detecting sources of fallacy, and of understanding the changes which manipulation, chemical re-agents, and other distm-hing causes may produce in the arrangement of the elementary parts of various textui’es. To these we will add another requisite not more important for microscopical than for other inquiries ; namely, a freedom from preconceived views or notions of particular forms of structme, and an absence of bias in favour of certain theories, or strauied analogies. The history of science affords but too many instances of the baneful influ- ence of the idola specus upon the ablest minds ; and it seems reasonable to expect that such creatures of the fancy would be especially prone to pervert both the bodily and the mental vision, in a kind of observation which is subject to so many causes of error as that conducted by the aid of the microscope. Of late years, however, great improvements have been introduced ui the mode of preparmg specimens, and the chances of aniving at erroneous inferences very much diminished. The structm-es represented in the new plates, illustrating tliis work, have been prepared according to the same plan, and all the figm-es have been drawn to a scale, so that they may be com- pared one with the other. The methods of injectmg with trans- parent Pmssian blue fluid and staining the germinal matter of the tissues with carmme are described in detail in “How to work with the Microscope,” but the student will find an outline of the plan at the end of the present chapter. This process of preparation is applicable to those specimens which require to be examined by the aid of very high magnifying powers, and it possesses this great advantage — that every tissue can be demon- strated in the same preparation. During the last ten years we have had the advantage of the use of much higher magnifying powers than could have been obtained previously. The fii’st J-g- ever made was the workman- ship of Mr. Wenham, and was completed in dime, 1856. In 1840, Messrs. Powell and Lealand succeeded in making a y’-g-, in 1860, a Jg, and in 1864 the same makers produced a -g-L-, the definition and penetrating power of all which glasses are exceed- ingly good. The first of these objectives magnifies about 1,500, and the last nearly 3,000 diameters linear. 56 PHYSICAL AND CHEMICAL INVESTIGATION. PHYSICAL AND CHEMICAL INVESTIGATION. Of late years our knowledge of physiology has been greatly advanced by physical investigation. The study of the processes of Diffusion, Osmose, and of the physical conditions of matter, has added much to om’ information regarding the natme of many changes occm’rmg in the living organism. The invention of various ingenious instruments for ascertaining the force of the cu’culation has taught us many important pidnciples which were unknown before. The fui’ther prosecution of investiga- tions upon the electrical phenomena of Hving beings, a depart- ment in which great success has been already achieved by Matteucci, and more recently by Du Bois Reymond, promises most valuable generalizations. The still recent discoveries regarding the mfluence of the solar spectrum upon different substances have been ah-eady applied to the investigation of animal fluids, and unportant results have been obtained by Stokes, in connection with the changes occmi'ing in the blood dm’ing the process of resphation.* Physical investigation has greatly advanced oru knowledge of the wonderful phenomena of sight and hearing, and by the aid of various optical instni- ments we are now enabled to make a most minute examination durmg life of the tissues within the eye. Haller perceived how necessary to the fiu’therance of physiology is a knowledge of Organic Chemistry ; and we could adduce many instances to prove, that the attention which has of late years been paid to this subject, has been most fruitful in giving us an msight into the natui’e of many functions, which, without it, we could not have obtained. In the living body the most dehcate chemical processes are unceasingly going on, for the formation of new compounds and the alteration or destruction of old ones. It is evident that no progress can be made in the investigation of these invisible processes, unless we can arrive at an exact knowledge of the chemical composition of the various substances which are concerned in them. Henceforward, in physiological research, physics, anatomy, and chemistry must go hand in hand. By the fii’st the physical * “ On the Reduction and Oxidation of the Colouring-matter of the Blood.” Proceedings of the Royal Society, No. 66, page 355, June, 1861. PHYSICAL AND CHEMICAL INVESTIGATION. 57 plienomena, which play so important a part in the changes which take place in complex organisms, may he elucidated ; by the second, the minute mechanism concerned in these pheno- mena is ascertained ; by the third, the nature of the diemical analyses and syntheses taking place in the Ihung organism are to be determined. Here is a wide field of research open for the employment of every Idnd of mind, and by devoting himself to one or other of these departments, every earnest student may contribute important aid to the advance of physiology, and thereby to the progress of medichie and surgery. In tlie composition of the Introduction, the authors have to acknowledge valuable aid from the following works : — HaUer, Elementa Physiologiae Corporis Humani ; Barclay on Life and Organization ; Koberton on Life and Mind ; Prichard on the Doctrine of a Vital Principle ; Dr. Carpenter’s article Life, and Dr. Alison’s article Instinct, in the Cyclopsedia of Amatomy and Physiology ; L. Pasteur, papers in the Comptes Eendus, 1859 — 64 ; P. A. Pouchet, Heterogenie ; Jorde, papers in the Phil. Trans. ; Julius R. Mayer, Die Organische Bewegung ; Tyndall, Heat as a Mode of Motion ; Grove on the Correlation of the Physical Forces ; Helmholtz, Erhalts- ung der Kraft ; Lectures at the Royal Institution ; Carpenter on the Correlation of Physical and Vital Forces, Journal of Science, Nos. I. and II. ; Graham’s papers on Diffusion, Osmose, Crystalloids and Colloids, Phil. Trans. 1850 — 64 ; Darwin on the Origin of Species ; Huxley, Lectures on the Origin of Species, and Elements of Com- parative Anatomy ; Carpenter, Principles of Physiology ; Herbert Spencer’s First Prmciples and his Principles of Biology ; Beale, the Anatomy of the Tissues, the Microscope in Medicine, and papers in the Archives of Medicine and Microscopical Journal. On the Preparation of the Tissues of Man and the higher Animals and Morhid Groioths, for Microscopical Examination with high poioers. It has been thought desirable to describe briefly the general method which has been employed in preparing specimens for examination with the highest powers, in the hope that the student may be encouraged to pursue some of the inquiries entered upon in this work, and that many of the investigations may be extended still further. In the first place, it is necessary to consider what circumstances interfere with the perfect demonstration of structure under the highest powers of the microscope, and how the disadvantageous operation of these might be pre- vented or diminished. 1. Of many tissues, sections sufficiently thin for high powers cannot be obtained by the processes usually adopted. In order to make the specimen thin enough, pressure must be employed, and in many instances very strong pressure is required. Even by very moderate pressure, tissues immersed in 58 ON THE PREPARATION OF TISSUES water are destroyed completely, and experience has proved that the requisite amount of pressure can only be employed if the tissue be immersed in, and thoroughly impregnated with, a viscid medium, which is not only readily miscible with water in all proportions, but with such chemical reagents as may be required to act upon one or more constituents of the tissue for the purposes of demonstration. 2. As many structures are exceedingly delicate, and undergo change very soon after death, it is necessary that the medium in which they are examined should have the property of preventing softening and disintegration, and should act the part of a preservative fluid. 3. In order that tissues should be uniformly permeated with a fluid within a very short time after the death of the animal, it is necessary that the fluid should come quickly in contact with every part of the texture. This may be efiected in two ways : — a. By soaking very thin pieces in the fluid, or i. By injecting the fluid into the vessels of the animal. 4. As difierent structures require fluids of difierent refractive power for their demonstration, the medium employed must be such that its refractive power can be increased or diminished, or that, for the medium fulfilling the former condition, another can be readily substituted which fulfils the latter requirements. 5. In investigations upon the changes which structure undergoes in the organism, it is necessary to distinguish between that part of the texture which is the oldest, and that which has just been produced — between matter in which active changes are going on, and matter which is in a passive state. It is only by fulfilling this requirement that the direction in which growth takes place, and the point where new matter is added, can he ascertained. 6. It is necessary, in many investigations, that the vessels should be positively distinguished from the other constituents of the tissue, aud it is important that the process by which this is efl'ected, should not interfere with the demonstration of all the tissues in the immediate vicinity of the vessels. 7. It is of the utmost importance the medium employed for demonstration should have the property of preserving the specimens, so that observers should be able to exhibit their preparations to others. Glycerine and syrup fulfil the requirements mentioned in the foregoing paragraphs. Strong syrup may be made by dissohing, with the aid of heat, lump sugar in distilled water, in the proportion of about three pounds to a pint. It is necessary in many cases to employ the strongest glycerine. In this country we have had the advantage of the beautiful preparation called Price’s glycerine, which is made of specific gravity 1240. It has been said that glycerine and strong syrup are not adapted for preserving soft tissues, because the tissues shrink and soft cells collapse in consequence of exosmose of their fluid contents. But I have many hundred specimens preserved in the strongest glycerine I could procure, aud I should obtain advantages if glycerine could be made of still greater density. There would be no difficulty in impregnating even very soft tissues with it. Tissues possess a considerable elastic property, aud although they shrink FOR MICROSCOPICAL EXAIMOSTATIOM. 59 when immersed in a medium of considerable density, they gradually regain their original volume if left in it for some time. In practice, the specimen is first immersed in weak glycerine or syrup, and the density of the fluid is gradually increased. In this way, in the course of two or three days, the softest and most delicate tissues may be made to swell out almost to their original volume. They become more transparent, but no chemical alteration is produced, and the addition of water will at any time cause the specimen to assume its ordinary characters. The hardest textures, like bone and teeth, may be thoroughly impregnated and preserved in strong glycerine, and the softest, like cerebral tissue, delicate nervous textures like the retina, or the nerve textures of the internal ear, may be permeated by the strongest glycerine, and when fully saturated with it, dissection may be carried to a degree of minuteness which I have found impossible in any other medium. Nor is the use of glycerine and syrup confined to the tissues of man and the higher animals. I have preparations from creatures of every class. The smallest animalcules, tissues of entozoa, polyps, star fishes, mollusks, insects, Crustacea, various vegetable tissues, microscopic fungi, and algae of the most minute and delicate structure, as well as the most delicate parts of higher vegetable tissues, may all be pre- served in these viscid media ; so also may be preserved the slowest and most rapidly growing, the hardest and softest morbid growths, as well as embryonic structures at every period of development, even when in the softest state. I am, indeed, not acquainted with any animal or vegetable tissue which cannot with the greatest advantage be mounted thus. All that is required is, that the strength of the fluid should be increased very gradually until the whole tissue is thoroughly penetrated by the strongest that can be obtained. Glycerine has long been in use among microscopists, but my object is to show that it is universally applicable, that it or syrup may be made the basis of all solutions employed by the microscopical observer with the greatest advan- tage, that many points are to be demonstrated by the use of these solutions, which have hitherto escaped observation, and that there are reasons for believing that very much may yet be discovered by the use of these substances. From these general remarks, I pass on to describe, more in detail, the particular method I have adopted during the last four years for minute investigations upon structures magnified by the highest powers yet employed. It will be necessary, in the first place, to give the composition of the difiereut solutions which I find useful for general purposes. 1. Weak common glycerine of about the specific gravity 1050. 2. The strongest Price's glycerine that can be obtained. 3. Syrup made by dissolving, by the application of a gentle heat in a water-bath, 31bs. of sugar in a pint of distilled water. A weaker solution can be prepared, as required, by mixing equal parts of syrup and water. The two following solutions should be kept ready prepared. They will keep for a length of time. The first is required for rendering the vessels distinct. The last enables us to distinguish with certainty the germinal or living matter of every tissue from the formed material. The Injecting Fluid. — The following mixture has succeeded admirably in my hands, and I therefore recommend it strongly. It penetrates to the finest 60 ON THE PREPARATION OP TISSUES vessels. The specimens injected with it retain their colour perfectly, and the injected tissues can also be stained with carmine. Price’s glycerine, 2 oz. by measure. Tincture of perchloride of iron, 10 drops. Ferrocyanide of potassium, 3 grains. Strong hydrochloric acid, 3 drops. Water, 1 oz. Mix the tincture of iron with one ounce of the glycerine ; and the ferro- cyanide of potassium, first dissolved in a little water, with the other ounce. These solutions are to be mixed together very gradually in a bottle, and are to be well shaken during admixture. The iron solution must be added to the ferrocyanide of potassium . Lastly, the water and hydrochloric acid are to be added. Sometimes I add a little alcohol (2 drachms) to the above mixture. This fluid does not deposit any sediment, even if kept for some time, and it appears like a blue solution when examined under high magnifying powers, in consequence of the insoluble particles of Prussian blue being so very minute. The Carmine Fluid . — The following is the composition of the carmine fluid ; Carmiue, 10 grains. Strong liquor ammonise, J drachm. Price’s glycerine, 2 ounces. Distilled water, 2 ounces. Alcohol, ^ ounce. The carmine in small fragments is to be placed in a test tube, and the ammonia added to it. By agitation, and with the aid of the heat of a spirit- lamp, the carmine is soon dissolved. The ammoniacal solution is to be boiled for a few seconds and then allowed to cool. After the lapse of an hour, much of the excess of ammonia wiU have escaped. The glycerine and water may then be added and the whole passed through a filter or allowed to stand for some time, and the perfectly clear supernatant fluid poured oflT and kept for use. This solution wiU keep for months, but sometimes a little carmine is deposited, owing to the escape of ammonia, in which case one or two drops of liquor ammonise to the four ounces of carmine solution may be added. The rapidity with which the colouring of a tissue immersed in this fluid takes place, depends partly upon the character of the tissue and partly upon the excess of ammonia present in the solution. If the solution be very alkaline the colouring is too intense, and much of the soft tissue or imperfectly developed formed material around the germinal mattei', is destroyed by the action of the alkali. If, on the other hand, the reaction of the solution be neutral, the uniform staining of tissue and germinal matter may result, and the appearances from which so much is learnt are not produced. When the vessels are injected with the Prussian blue fluid the carmine fluid requires to be sufficiently alkaline to neutralise the free acid present. The permeat- ing power of the solution is easily increased by the addition of a little more water and alcohol. Some tissues absorb the colour very slowly. Fibrous tissue, bone and cartilage, even in very thin sections, will require twelve houi-s or even more. FOR MICROSCOPICAL EXAMINATION. 61 but perfectly fresh soft embryonic tissues, and very thin sections of the liver and kidney, thin sections of morbid growths rich in cells, may be coloured in half an hour, while the cells of the above structures, placed on a glass slide, may be coloured in less than a minute. I have often coloured the germinal matter of the fresh liver cell in a few seconds, by simply allowing the carmine fluid to flow once over the specimen. After the specimen has been properly stained, it is to be washed in a solution consisting of — Strong glycerine, 2 parts. Water, I part. It is then transferred to the following acid fluid : — Strong glycerine, I ounce. Strong acetic acid, 5 drops. After having remained in this acid fluid for three or four days, it will be found that the portions of even soft pulpy textures have regained the volume they occupied when fresh. They have swollen out again even in the strongest glycerine. It being established as a principle that, for minute investigation, tissues must be immersed and thoroughly saturated with viscid media miscible in all proportions with water, it almost follows that reagents applied to such tissues should be dissolved in media of the same physical properties. For a long time past I have been in the habit of employing solution of potash, acetic acid, and other reagents, dissolved in glycerine instead of in water. In some cases I have found the addition of very strong solutions of certain reagents necessary. For example, the greatest advantage sometimes results from the application to a tissue of very strong acetic acid. If the acid be added to glycerine in quan- tity, the solution will no longer be viscid, so that another plan must be resorted to. I thicken the strongest acetic acid with sugar, a gentle heat being applied to dissolve the sugar. Thus a very strong acetic acid solution of the con- sistence of syrup can be most readily prepared. Strong solutions of potash, soda, and other reagents, are to be made in the same way. Thus a complete chemical examination may be conducted upon tissues, solutions, or deposits pi’eserved in viscid media. The reactions are most conclusive, but of course take a much longer time for completion than when carried out in the ordinary manner. Ten or twelve hours must be allowed to elapse before the change is complete, and the process is expedited if the slide be placed in a warm place (about 100°). Chromic Acid Fluid . — A most valuable fluid to the microscopist, is a solution of chromic acid in glycerine, and another solution of bichromate of potash in the same fluid. A few drops of a strong solution of chromic acid may be added, so as to give to the glycerine a pale straw colour. The bichromate of potash solution is prepared by adding from twelve to twenty drops of a strong saturated solution of bichromate of potash to an ounce of the strong glycerine. By this plan, the hardening effects of these reagents upon the finest nerve tissues are improved, while the granular appearance which is caused by aqueous solutions of these substances is much less. Some- times advantage seems to result from mixing a little of the chromic acid with the acetic acid solution of glycerine. 62 ON THE PKEPARATION OF TISSUES If desired, sugar may be substituted for glycerine in all the fluids employed, including the carmine and injecting fluids ; but glycerine, although more expensive, possesses many advantages, and, as far as I am able to judge, is the best viscid medium to employ for general purposes. One great inconvenience of syrup arises from the growth of fungi, especially in warm weather. Camphor, creosote, carbolic acid, naphtha, prevent this to some extent ; but it is a disadvantage from which strong glycerine is perfectly free. Sometimes, too, crystallisation occurs, and destroys the specimen. In using first a syrupy fluid, and then glycerine, to the same specimen, it must be remembered that the two fluids mix but slowly, so that plenty of time must be allowed for the thorough penetration of the medium used last. I keep various tests, such as alcohol, ether, the various acids, and alkalies, and other tests in the form of viscid solutions made with glycerine or sugar. The reaction of the iodine tests for amyloid matter, starch and cellulose, is much more distinct when employed in this manner. The plan is, to allow the texture to be tested to be thoroughly saturated with the strong glycerine solutions, and then to add water. In the course of a few hours the reaction takes place very strongly. The plan pursued for preparing the Tissue . — The general plan I follow, is the same for all tissues of all vertebrate animals and morbid growths ; but I will describe the several steps of the process as they were conducted in the demonstration of the minute structure of ganglion cells, and of the structure of the papillae of the frog’s tongue.* The description given also applies to the mode of preparing specimens of muscular fibre to demonstrate the mode of distribution of the finest branches of nerve fibre, and specimens of the minute structure of the brain, spinal cord, and ganglia of man and the higher animals. Perhaps it will be most useful to describe the mode of proceeding when a frog is to be prepared for minute inspection. My researches upon the tissues of the frog have been principally conducted upon the little green tree frog (Hyla arborea), for expei’ience has proved to me that the tissues of this little animal are so much more favourable for investigation than those of the common frog, that it is well worth while to obtain specimens, even at the cost of 2s. or 2s. 6d. each. The student may, however, obtain very beautiful specimens from the common frog. The animal is killed by being dashed suddenly upon the floor, but it must first be carefully folded up in the centre of a large cloth, so that the tissues may not be bruised in the least degree. Next an opening is made in the sternum, the heart exposed, and a fine injecting pipe, after being filled with a little injection, is tied in the artery. The injection ought to be complete in from twenty minutes to half an hour, and sometimes in less time than this. The injection, being pale, cannot be very distinctly seen by the unaided eye, but if the operation has been con- ducted successfully, the tissues will be found swollen and the areolar tissue about the neck will be fully distended. The injection being complete, the abdominal cavity of the frog is opened, and the viscera washed with strong glycerine. The legs may be removed, the mouth slit open upon one side, and the pharynx well washed with glycerine. * “ On tlie structure and formation of the so-called apolar, unipolar, and bipolar nei-ve cells of the fi-og.” — Phil. Trans. May, 1863. “ New Observations upon the minnte anatomy of the papdlaD of the frog’s tongue.” — Plul. Trans. June, 1864. FOR MICROSCOPICAL EXAMINATION. 63 If it is desired to prepare one organ only, this may, of course, be removed and operated upon separately ; but I generally subject the entire trunk, with aU the viscera, to the action of the carmine fluid. If the brain and spinal cord are special objects of inquiry, the cranium and the spinal canal must be opened so as to expose the organs completely, before the staining process is cemmenced. Enough of the carmine solution is then placed in a little porcelain basin or gallypot, just sufficient to cover the entire trunk and viscera. The specimen is then moved about in the carmine fluid, so that every part that is exposed may be thoroughly wetted by it ; sometimes slight pressure with the finger is required. It is left in the carmine fluid for a period varying from four to six or eight hours, being occasionally pressed and moved about during this time, so as to ensure the carmine fluid coming into contact with every part. By this time the blue colour of the vessels of the lungs, viscera, &c., will have almost entirely disappeared, and all the tissues will appear uniformly red. The staining is now complete. The carmine fluid is poured ofiF and thrown away, and the preparation washed quickly with the glycerine solution. The specimen is now placed in another little basin, and some strong glycerine poured over it ; it is then left for two or three hours, and a little more strong glycerine added ; when, from six to twelve hours since the specimen was removed from the carmine solution have elapsed, the preparation is ready for the last preliminary operation. The glycerine used for washing it is poured oflf, and sufficient strong Price’s glycerine added just to cover it. To this, three or four drops of strong acetic acid are added, and well mixed, with the glycerine. In this acid fluid the preparation may be left for several days, when a small piece of some vascular part may be cut off, placed in a drop of glycerine, and subjected to microscopical examination. If the injected vessels are of a bright blue colour, and the nuclei of the tissues of a bright red, the specimen is ready for minute examination ; but if the blue colour is not distinct, three or four more di-ops of acetic acid must be added to the glycerine, and the preparation soaked for a few days longer. If the nuclei are of a dark red colour, and appear smooth and homogeneous, more especially if the tissue intervening between them is coloured red, the specimen has been soaked too long in the carmine fluid ; but in this case, although parts upon the surface may be useless for further investigation, the tissues below may have received the proper amount of colour. Another plan which I have adopted, and which, although more difficult in practice, if carried out with due care, possesses some advantages, is the following : The vessels are in the first instance thoroughly injected with the carmine fluid, and the preparation allowed to soak for four-and-twenty hours, when a little glycerine is first injected, and then the Prussian blue injecting fluid introduced until the capillary vessels are completely filled with it. The fluid must be injected very slowly, and but slight pressure employed, or the vessels will certainly be ruptured. When the second injection is complete, the textures required for investigation may be removed, washed in glycerine, and, after soaking for a day or two in acetic acid glycerine, will be ready for microscopic investigation. Beautiful and most perfect specimens of solid internal organs, like the brain and spinal cord, may be obtained by this process ; and it is the most perfect plan I have adopted, although it presents many practical difficulties, and will probably fail in the hands of the student 64 ON THE PKEPARATION OF TISSUES unless he has the patience to make the attempt many times ; when, however, success is obtained, he is well rewarded for the trouble he has taken, and the many failures he may have experienced. The tissues or organs to be subjected to special investigation may now be removed, and transferred to fresh glycerine ; they may be kept in little corked glass tubes, and properly labelled. Generally, the tissue will contain sufficient acetic acid, but if this is not the case, one drop more may be added. Suppose, now, the nerves with the small vessels and areolar tissue at the posterior and lower part of the abdominal cavity, have been placed in one tube, and the prepared tongue of the Ilyla in another, the former specimen may be taken out of the glycerine and spread out upon a glass slide. If it be examined with an inch power, numerous microscopic ganglia may be seen. Several of these, perhaps, are close to small arteries. Those which are most free from pigment cells are selected, and removed carefully by the aid of a sharp knife, fine scissars, forceps, and a needle point. This operation may be effected while the slide is placed upon the stage of the microscope. The transmitted light enables the observer to see the minute pieces very distinctly ; if necessary, a watchmaker’s lens may be used. The pieces selected are transferred to a few drops of the strongest glycerine placed in a watch gLass or small basin, or in one of the little china colour moulds, and left to soak for several hours. The microscopical examination of the specimen may now be carried out. One of the small pieces is placed upon a glass slide, in a drop of fresh glycerine, and covered with thin glass. The glass slide may be gently warmed over the lamp, and the thin glass pressed down upon the preparation by slight taps with a needle point. The specimen may now be examined with a quarter, and afterwards with the twelfth of an inch object glass. A good deal of granular matter will possibly obscure the delicate points in the structure. The slide is again gently warmed, and, with the aid of a needle, the thin glass is made to slide over the surface of the specimen, without the position of the latter being altered, and then removed and cleaned. The specimen is then washed by the addition of drop after drop of strong gh'cerine containing five drops of acetic acid to the ounce. The slide can be slightly inclined while it is warmed gently over the lamp, in such a manner that the drops of glycerine slowly pass over the specimen and wash away the debris from its surface. The most convenient instrument for dropping the glycerine on the specimen is a little bottle, of two ounces capacity, with a syphon tube drawn to a point, and a straight tube, with an expanded upper part, over which is tied a piece of stout sheet vulcanized India-rubber. Upon com- pressing the air, by pressing down the India-rubber, the glycerine is forced drop by drop through the syphon tube and allowed to fall upon the specimen.* When several drops of pure glycerine have been allowed to flow over the specimen, the thin glass cover, after having been cleaned, is re-applied and pressed upon the specimen very gradually, but more firmly than before. If * These little bottles, as well as any other instruments or apparatus required, can be obtained of Mr. Matthews, Carey-street, Lincoln’s Inn-fields ; Mr. G. King, 190, Great Portland-street, or Mr. Highley, Green-street, Leicester-square. FOR MICROSCOPICAL EXAMINATION. G5 the preparation looks pretty clear when examined with the twelfth, the glass cover may he cemented down with Bell’s cement, and the specimen left for many days in a quiet place. It may then be re-examined, the process of washing with glycerine repeated, and further pressure applied until it is rendered as thin as is desired. When this point has been reached, more glycerine with acetic acid is to be added, and a plate of mica or the thimiest glass cover 'when it maybe examined with the twenty-fifth. The pi’ocess of fiattening may be pushed still further if desirable, — and if only carried out very slowly by gentle taps or careful pressure with the finger and thumb from dag to dag, the elements of the tissues are gradually separated without being destroyed. If there be much connective tissue, which interferes with a clear vierv of the finest nerve or muscular fibres, it may be necessary to immerse the specimen for some days in the acetic acid syrup, and then transfer it to fresh glycerine. The success of this process depends upon the care and patience with which it is carried out. The most perfect results are obtained in cases where the washing, pressure, and warming have been very slowly con- ducted, and it is most interesting to notice the minute points of structure which are gradually rendered clearer by the application of a gentle heat, subjecting the specimen to a little firmer pressure or by soaking it in a little fresh glycerine placed in a watch-glass. Specimens of tissue prepared in this way can be transferred from slide to slide, and no matter how thin they may be, after having been allowed to soak in fresh glycerine they may always be laid out again perfectly flat upon another slide, by the aid of needles.* The action of these viscid fluids is most valuable, and I feel sure that by the process here given, retaining the principle, but modifying the details in special cases, many new and important anatomical facts will be discovered. Until this process is carried out successfully by ether observers, I have little hope of my own observations being confirmed. Suppose the observer desires to study the papillm of the frog’s tongue. Small pieces of the mucous membrane being removed by sharp scissors, they are transferred to glycerine, subjected to the same very gradually increased pressure, until the individual papillae are themselves slightly flattened. It is possible from a specimen to remove a number of the separate papillae on a needle point, transfer them to glycerine or to the acetic acid syrup, and then mount them for examination with the 25th object-glass. All the points I have described and figured in my paper may then be demonstrated in several papillae. Thin sections of brain, spinal cord, &c., may be subjected to the same process for examination with the highest powers. The tissues of man in health and disease and various morbid growths may be prepared in precisely the same manner. Even the vessels of a small portion of a solid organ, like the brain, liver, or kidney, or those of a small tumour, may be very readily injected. The escape of the injection from divided vessels may be prevented by tying them or by pressure, but considerable escape from the divided vessels does not prevent some of the capillaries being perfectly filled. The most delicate preparations retain their characters for many months, and some * I often mount these specimens upon a circle of thin glass about. | of an inch in diameter, instead of upon a glass slide. The circle is then placed in a wooden slide in the centre of which a hole has been drilled of the proper dimensions to receive it. It is fixed in its place by a ring of gummed paper. F 66 ON THE PREPARATION OF TISSUES for several years, so that in many cases the very preparations from which my drawings have been made, have been preserved. Method of preTpannq specimens of Bone and Teeth and. other hard tissues . — By the methods generally employed for demonstrating the structure of bone, teeth, and other hard tissues, we are enabled to form a notion of the dead and dried tissue only. The soft material is dried up before the section is made. And yet this very soft material, which is not represented in the drawings published in different works, is that which makes the only difference between the dried bone or tooth in our cabinets and that which still remains an integral part of the living body. So far from this soft matter being unimportant, it is the most important of all the structures of the hard textui-e. It is by this alone that all osseous and dental tissues are formed and nourished, and from the arrangement of this soft matter not having been recognized the most erroneous ideas have prevailed, and still prevail, upon the formation and nutrition of the osseous and dental tissues. Even now it is generally believed that the dentinal tubes are real tubular passages for conveying to all parts of the dentine, and are thus subser- vient to its “ nutrition,” and yet it is more than eight years since Mr. Tomes proved most conclusively that these so-called “ tubes ” were occupied in the recent state by a moist but tolerably firm material (“Phil. Trans.,” Feb., 1856). I have verified Mr. Tomes’ description, and am quite certain that the so-called dentinal tubes are not channels for the mere flowing up and down of nutrient fluid.* Suppose a tooth is to be prepared for minute microscopical investigation, we may proceed as follows. The same plan is applicable to bone and shell. 1. As soon as possible after extraction, the tooth may be broken by a hammer into fragments, so as to expose clean surfaces of the tissues. Pieces of dentine with j)ortions of pulp still adhering to them may then be selected and immersed in the carmine fluid, and placed in a vessel lightly covered with paper, so as to exclude the dust. The whole may be left in a warm room for from twenty-four to forty-eight hours. 2. The carmine solution may then be poured off, and a little plain dilute glycerine added, as already described in the case of soft tissues. 3. After the fragments of teeth have remained in this fluid for five or six hours, the excess, now coloured with the carmine, may be poured off, and replaced by a little strong glycerine and acetic acid. 4. After having remained in this fluid for three or four days, it will be found that the portions of soft pulp have regained the volume they occupied when fresh. They have swollen out again even in the strongest glycerine. 5. I have found that in many cases, when it is desired to study the arrange- ment of the nerves, it is necessary to harden the pulp by immersion in glyce- rine solution, made by adding to an ounce of the glycerine solution of acetic acid two or three drops of a strong solution of chromic acid. The fragments may remain in this solution for three or four days, and then be transferred to the acetic acid solution, in which they may be preserved for years with all the soft parts perfect. * On the structure of recent bone and teeth, see my leetures on “ The structure and growth of the tissues.” Delivered at the Royal College of Physicians, I860. FOR JIICROSCOPICAL EXAillNATIOX. 67 6. The specimens are now ready for examination. Thin sections are cut with a knife from the fractured surfaces of the dentine, including a portion of the soft pulp. The knife should be strong, but sharp. In practice I have found the double-edged scalpels made for me by the Messrs. Weiss and Son, of the Strand, answer exceedingly well for this purpose, nor will the edge of the knife be destroyed so soon as would be supposed. 7. The minute fragments of sections thus obtained are placed upon a slide and immersed in a drop of pure strong glycerine, in w’hich they may be allowed to soak for an hour or more, and then examined by a low power (an inch). The best pieces are then to be selected by the aid of a fine needle, and removed to a drop of glycerine containing two drops of acetic acid to the ounce, and placed upon a clean slide. Lastly the thin glass cover is care- fully applied, and the specimen may be examined with higher powers. 8. If it is desired to retain the specimen, the excess of glycerine fluid is absorbed by small pieces of blotting-paper, and the glass cover cemented to the slide by carefully painting a narrow ring of Bell's cement round it. When this flrst thin layer is dry, the brush may be carried round a second time, and after the lapse of a few days, more may be applied, ilounted in this way the specimen will retain its character for years. Hard tissues, like bone, dentine, and enamel, become somewhat softened by prolonged maceration in glycerine, and if a few drops of acetic acid are added, the softening process may be carried to a greater extent, and yet without the calcareous matter being dissolved out to any perceptible extent. If desired, of course the calcareous matter may be in part or entirely removed by increasing the strength of the acid fluid in which the preparation is immersed. But, far short of this, the hard, brittle texture is so altered that thin sections may be cut without any difficulty. Specimens prepared in this way may be examined by the highest magnifying powers yet made, — by which statement I mean, of course, to imply that more may be learned by the use of such high powers (1,000 to 3,000 linear) than by employing ordinary object glasses. Contrary to general opinion, many of the softest textures may be inves- tigated with the greatest facility after having been soaked in strong glycerine. In preparing these, the same steps which have been described must be carried out, but the glycerine used at first must be weaker, and its strength must be very slowly and gradually increased. Young embryos may be injected with the Prussian blue fluid. The pipe cannot be tied in the vessels, as they are extremely soft. But if it is simply inserted, much of the injection will run onwards into the capillaries, and the escape of a certain quantity by the side of the pipe is a matter of no moment. I have beautiful preparations of the most delicate embryonic tissues, preserved in the strongest glycerine. It is often advantageous to harden the tissues slightly by the addition of a little of the chromic acid glycerine solution. When once the tissues have been fuUy permeated by glycerine, they may be dissected and manipulated in a manner which before was impossible. [L. S. B.] F 2 CHAPTER I. oi? STIUTCTITRE. OF THE TISSFES OEIs'EBALLT. OF THE CEEE, OR ' ELEMENTARY PART. — EIFFERENT FORMS OF CELLS. — OF INTERCEL- LULAR SURSTANCE. — OF THE LITING OR GERMINAL MATTER OF THE CELL. — OF THE DEYELOPMENT AND MULTIPLICATION OF CELLS, — OF THE CHANGES IN THE CELL IN DISEASE. In certain tissues ive are unable, even with the aid of tlie liighest powers, to demonstrate any stmctiu-al peculiarities Avhatever. But it must be borne in mind that in some appa- rently perfectly homogeneous textures distinct stmcture may be demonstrated by special methods of investigation. Vaiious plans of tintuig have been employed for tliis pm-pose, and solu- tions of rosanilin dye, nitrate of silver and other soluble coloiuing matters hai^e been found veiy useful. It is, therefore, not impro- bable that future research will prove that many tissues which are now considered perfectly stmctureless and homogeneous possess distinct structm-e. The different ph^’sical properties of tissues seem to be due in part to then’ chemical composition and partly to peculiaritii s in Avhat may be termed the build of the textm-e. The differences in structin-e and properties of tlie vaiious tissues must not be attributed merely to a difference in the composition of the nutrient material lA-hich takes part in their production, for, fi'om the same pabulum, matter chfiferent in physical properties and chemical composition may be produced through the agency of structureless living matter. Nor can we trace the cause of the difference in structiu'e of the tissues to difference in stnictural character, or chemical composition of the germuial matter from which they are formed. So far from tliis being the case it seems that the very different textures in the body all result from changes in germinal matter having, as far as can yet be ascertahied by ohsei'vation, precisely the same characters. And we know that all the masses of germinal matter concerned in the process have the same origin. It seems, therefore, upon the whole, more probable that the masses of germinal matter of the different tissues produce from the same nutrient constituents, substances differing in composition and in texture by virtue of GRANULES AND GLOBULES. 69 some peciiliar inliereiit power, than that each selects from a com- mon fluid those particular materials most nearly correspondhig to the substance to be formed, and causes them to combine. The constituents of the tissues are not constituents of the blood which are merely selected and separated from it, but they are actually formed through the agency of the germinal or livnag matter. The formative power of tliis germmal or living matter seems to be of far greater importance than its power of selection. Indeed, tliis supposed selective power, considered by some sufficient to account for the obseiwed facts, has been assumed rather than proved to be one of the most hnportant properties of the cell. Grajiules, Globules, Fibres, Membranes. — In certam textines, and suspended in the fluids of the animal body, chfferent struc- tiu’al elements may be observed which have received definite names. Granules are muiute particles which exhibit no definite form or magnitude when examined mider very liigh magnifying- powers. Granules are represented in plate I. fig. 1. Globules are small bodies of spherical or oval form, composed throughout of the same substance, exhibiting a clear centre and a distinct outluie, the apparent thickness of wliich varies according as the medium hi which the globule is placed differs in refr-active power from the material of which the globule itself is composed. So that the outluie of the same globule may appear to be very thick and black in water, and as a very thin line m oil, turpentine, or Canada balsam. Granules and globules vary in chemical com- position. They may be composed of albuminous matter, fatty matter, or earthy matter, and these substances may be chsthi- guished by the application of chemical tests.* Globules are represented in plate I. fig. 2. A very good idea of the general appearance of globules may be formed by examuiing a drop of milk luider a magnifying power of 200 diameters. Fibres may appear as exceedingly fine lines, the diameter of which cannot be measm-ed, or as distinct cylindrical threads, or flattened bands, liavhig a definite chameter. The fibres may be. straight, or wavy, or much cm-ved. They may be arranged parallel t© one another or they may cross one another at every * Globules of albuminous matter are rendered transparent by acetic acid and are dissolved by potash and soda. Eat globides are soluble in ether and not altered, by acetic acid. Globules of earthy matter are dissolved by acids but are not changed by alkalies. 70 FIBRES — MEMBRANE, possible angle. Not mifi-equently there is an indication of fine lines although no distuict fibres separable from one another can be demonstrated. This is spoken of as a fibrous appear- ance as is represented in fibrous tissue, plate I. fig. 3 a. Membrane . — Membrane may be so perfectly transparent and homogeneous that we are only able to demonstrate its existence by the plaits or folds which it forms. Sometimes membrane appears granular or exhibits a fibrous appearance, and not unffe- quently calcareous particles are deposited m its substance. ]\Iembrane sometimes consists of an insoluble material allied to albumen, but some membranes are composed of a substance which in its physical and chemical characters agrees -vrith yellow elastic tissue. Clear, transparent, and stmctm’eless membrane is represented in plate I. fig. 4. OF THE TISSUES. Although fully developed tissues might be classified accord- ing to the peculiarities of structure they exhibit, the classi- fication woidd be defective in. so many particulars that little advantage could result from the attempt to arrange the tissues of man or those of animals and plants in several artificial groups. Nevertheless siich an arrangement as that given below, though far fr’om perfect, may be of some assistance to the student TABULAE TIEW OF THE TISSUES OF THE HUAIAX BODY. 1. Simple membrane, bomogeneous, or nearly so, employed alone, or in the formation of compound membranes. 2. Filamentous tissues, the elements of which are real or apparent filaments. 3. Compound membranes, composed in some cases, of simple membrane, and a layer of ceUs, of various forms (epithehum or epidermis), in others of areolar or connec- tive tissue and epithehum only. 4. Tissues which exhibit a cellular structm’e in then’ fuUy developed state. 5. Tissues hardened by calcareous salts. 6. Compound tissues. a. Composed of two different kinds of tissues of simple structure. h. Tissues composed of material which possesses special endowments, c. Tubes for distributing nutrient matter. Examples. — Posterior layer of the cornea. — Capsule of the lens. — Sarcolemma of muscle. White and yeUow fibrous tissues. — Areolar or eounective tissue. Mucous membrane. — Skin. — True or secreting glands. — Serous and synovial membranes. Cuticle. NaUs. Hah. — Gland, pig- ment, and fat cells. — Cartilage. Bone. — Teeth. Connective tissue. — ^Fibro-cartUage. Certain forms of elastic tissue. Muscle. — Nerve. Blood vessels. — Absorbent vessels. OF THE TISSUES OF THE HUIVIAN BODY. 71 Of the Tissues generally . — The first texture enumerated in this table is an example of the simplest form of membrane. Its principal character is extension ; but as to the arrangement of its ultimate pai-ticles nothing is known ; for, under the highest powers of the microscope it appears homogeneous, that is, without visible lunits to its particles, or, at most, irregulaiiy and very indistinctly granular. The capsule of the lens, the posterior layer of the cornea, the uruiiferous tubes, and the walls of many “cells” are composed of it; and it enters into the formation of muscle, nerve, and the adipose and tegmnentary tissues. It is not peculiar to living beings, for a structmeless fibre or membrane may be produced artificially. The filamentous tissues are extensively used for connecting different parts, or for associating the elements of other tissues. The ligaments of joints, for instance, are composed of the white or yellow fibrous tissues ; and areolar or connective tissue smTounds and coimects the elementary parts of nerves and muscles, accompanies and supports the blood-vessels, and unites the tegmnentary tissues to their subjacent parts or organs. Under the title compound membranes we include those expan- sions, which form the external integument of the body, and are continued into the various internal passages, which, by their involutions, contribute to form the various secreting organs or glands. These are composed of the simple homogeneous mem- brane, covered by epideimis or epithelium, and resting upon a layer of vessels, nerves, and areolar tissue in great variety ; and they constitute the skin, and mucous membranes, with the various glandular organs which open upon their sm’face. To these, we may add those remarkable membranes, com- posed of areolar tissue and a tlun indusium of epithehum, which are employed as mechanical aids to motion. These are the serous membranes which line the great cavities of the body, and the synovial membranes, which are mterposed between the articular extremities of the bones in certain joints, or are con- nected vith and facilitate the motions of tendons. The tissues which compose the fourth class have no common character, except then.’ adlierence, in the adult state, to the primitive cellular structme, and then analogy m that particular with the vegetable tissue. Although a certain agreement, in morphological characters, allows these textures to be grouped 72 GENERAL STRUCTURE' together, none can be more dissimilar as regards their endow- ments. They differ materially as to the degTee of cohesion between their cells : in cartilage there is generally what is spoken of as a finn and resisting intercellular substance, which, however, is not truly hUercellular, smce it exactly corresponds to what in other tissues is spoken of as cell-wall. The sclerous tissue {aK\'qpo<;, hard,) contains a large pro- portion of inorganic material, to which it owes its hardness. The compound tissues are those, the elementary paris of which are concerned in the production of two distinct tissues. Fibro-cartilage is a compoimd textni’e, being made up of white fibrous tissue and cartilage ; it is employed almost exclusively in the mechanism of the joints of the skeleton, in wliich it is associated with bone, cartilage, and ligaments. Muscle and nerve are composed of parallel fibres or thi-eads, each fibre being compound, and exhibiting a special stmcture ; in muscle, it is composed of homogeneous membrane, disposed like a tube, contahnng a fleshy {sarcous) substance, arranged in a particular manner, which is the seat of the pecuhar con- tractile properties of the tissue ; and, hi nerve, the fibres are composed of similar tubes of homogeneous membrane contain- ing an oleo-albummous substance, vdthin which is a dehcate band or fibre possessing the remarkable property of conducting the nerve force. The arteries, veins, and larger absorbent vessels, are also examples of compomid tissues, — their walls bemg composed of several textures exhibitmg different endow- ments. All these different tissues, however, possess in the hving groAving state, dissemmated at nearly equal distances thi'ough their substance, masses of germinal or Hvuig matter, which appear perfectly colomless, homogeneous, and ahnost diffluent. In this material all the essential changes take place. Each mass is spherical or oval in form, and often exliibits in its sub- tance one or more smaller masses (nuclei), which are somewhat less transparent than the general mass in which they are embedded. In the nuclei in many cases are other still smaller masses (nucleoh), and sometimes within these yet another series may be detected with the aid of very high magnifying powers. Thus it Av’ould seem as if centres were arranged within centres. OP THE TISSUES. 73 xA.lthoug’li tlie various tissues existing in the fully developed organism differ remarkably from one another hi structure, physical properties, chemical composition, and action, they all pass tlnough a shnilar series of changes dui’ing then formation. The production of the matter of wliich the outer part of the simple cell of mildew is composed, is the result of changes probably very similar in essential nature to those which end hi the production of the liighest and most complex cell in the neiwous system of man, and, when successive layers are to be demonstrated in the outer part of any cell, as is often the case, they have been deposited in the same order. We are as ignorant of the real cause and of the nature of the one process as the other. But it is reasonable to infer that if we could ascertain the natm’e of the changes which actually take place in the simplest living beings during then growth and multi- plication, the modifications winch occur in the most complex would very soon be understood. Although we cannot miderstand or explaui how phenomena, which we can observe \vithout difficulty, result, we can demon- strate certahi facts, ui comiection with cell formation, of the utmost interest. We may infer the com’se taken by the lifeless nutrient material when it is absorbed by the Iridng elementary part or cell, because we can see coloined flixid pursuing the same course when the cell is even detached from the living- body and placed under our microscopes. We can show where the inanunate pabulum becomes changed and acqrxu-es new and v/onderfnl properties which m turn it can communicate to new inanimate matter. We can observe actions hi this altered matter which we cannot explain, but which we may with reason refer to these newly-acc[uu-ed powers ; the actions and changes which take place m this matter are very different to anything fannliar to us apart from living beiugs, and hence to these we limit the term vital. We can demonstrate where the tissue is first produced, and the precise position hi which new tissue is added to that which already exists. We can show which is the yoimgest and which is the oldest portion of a tissue, and we can give some explanation of the mode in which the old tissue which has done its work is destroyed and removed. Lastly, in certain cases we can show how, after the old tissue has been removed, new and more complex structure takes its 74 OF THE CELL, ’ place. In short, we possess observations sufficiently complete, in some instances, to enable us to sketch, imperfectly it is tnie, the life histoiy of the texture, and give an account of its development, the changes occurring in it dming its fully- developed state, its gradual decay and removal, and the mamier in which its place is occupied by new tissue. We can also trace in some instances the modifications occrming in these processes under certain altered and exceptional conditions winch constitute disease. OF THE CELL, OR ELEMENTARY PART. Of the Cell . — The cell is even now considered by many to be a body consisting of certain essential definite and constant parts {cell ivall, cell contents^ and nucleus), to each of which a special office has been assigned by some vniters. Some have supposed that living cells exert an influence upon matter which surrounds them, or even upon other living cells at a distance from them. Others maintain that veiy active powers of pro- ducing chemical and other changes reside in the nucleus alone. The power of producing change has been attributed in tmm to the cell wall, to the matter within the cell, and to the inter- cellular substance. No well-ascertained facts have, however, yet been adduced in favorn of the ffiew, that any Ihdng structure whatever can influence matter at a distance fi-oin it, so as to alter its properties or composition, or in support of the notion that cell wall, cell contents, or intercellrdar substance possess any metabolic power whatever. The power of effecting changes in some mysterious or at least miexplained manner, has, however, been assumed to exist in the cell even by some of those observers who have most strongly advocated the phy- sical views of life. On the other hand, the wonderful changes occiming m the development of tissues have been spoken of as if they cordd be very readily imitated artificially. The fonnation of a cell tissue has been compared to the formation of a wall in which ready- made bricks (cells) are supposed to be cemented together by ready-made mortar (intercellular substance). The formation of the tissue has been described as if the cells were first formed and then arranged in their places, and the hitercellular sub- OR ELEMENTARY PART. 75 stance deposited between them. Bnt how diiferent is the process in nature ! At first there are no cells at all. There are hut small masses of transparent living germinal matter separated from one another by a little soft formed matter. From this anatomically simple material the fifily formed tissue results by gradual changes. New masses of germinal matter are produced by the chvision and multiplication of those existing before, in the manner represented in figs. 5 and 6. New formed material is formed fi-om these, and as they separate or move away from one another, it accumidates in the intervals between them. The relative proportion which the latter bears to the germinal matter gradually increases as the tissue advances towards its perfect state of development. See figs. 7 and 8. The changes go on in regular order uninterruptedly from the earliest peiiod when there was nothing but a little formless, structureless living matter, till the tissue or organ is formed, and its structm'e fully developed. It has been inferred by many wiiters, that in the formation of a fibre, elongated cells become joined together, and it has been supposed that in the production of a tube the walls of several cells coalesce, and thus the cavfity of the resulting tube corresponds to the cavities of the original cells. In the forma- tion of such a tissue as muscle or nerve, it has been assumed that the outer or membranous sheath is formed by coalescence of cell walls ; while the proper material (contractile tissue, or nerve fibre) is supposed to result from a modification occurring in the cell eontents. When processes are seen to project from cells, it is said that they have been shot out or protruded from the cell ; while, in a tissue composed of stellate cells, authorities have accormted for the arrangement by supposmg that the tubrdar processes of contigaious cells grew away tiU they met one another, and that when they met they coalesced, so that the cavity of one cell became coimected with the cavities of neighboming cells by tubular communicating channels. And yet no one has even attempted to explain how it happens that the processes or tubes supposed to grow from contiguous cells invariably manage to hit one another exactly, to meet, join, and at last to coalesce, without in any uastance overlapping one another, or ever failing to meet in the exact line. But if we examine such a tissue at an early period of its development, we find that 76 STRUCTURE AND FORMATION SO far from tliere being any indications of cells from wliicli out- growths are formed, the masses of germinal matter are con- tinuous with one another ; so that, in fact, the connecting pro- cesses or tubes are connected fi’om the first, and, as growth takes place, the connecting tubes become thinner and thinner, being as it were gradually drawn out as the masses of gei*minal matter become separated farther and farther fi’om one another, in the manner shown in figs. 11, 12, 13, and 14. Careful obseiwation of one particular tissue at different periods of its growth will comdnce the obseiwer that its forma- tion takes place in a veiy simple mamier, and that the fonnation of all tissues exhibits much in common. At no peiiod of tlie life of many tissues can the arbitrary definition usually given to the cell (^cell wall, cell contents, and nucleus) be correctly applied to the elementary parts of which the texture is composed, nor in any case are such bodies fii'st produced and then arranged in special positions and united together with a comiective sub- stance so as to form a mass of tissue. Nevertheless the term “cell” is short and convenient, and it may be still applied to the anatomical elementaiy part of every tissue at every peiiod of its life, if the meaiiuig be slightly modified. Instead of attemptmg to divide the cell itself into anatomical constituents, we may speak of it as consisting of matter in two very different states or stages of existence — matter which lives (^germinal matter') and matter wliich is formed and has ceased to manifest purely vital phenomena (formed mate- rial) (see Introduction, page 11). The simplest and most minute living particle as well as the most complex cell capable of growth or multiplication consists of matter m these two states, liut the relative proportions vary greatly at different periods in the lite of the cell and under different conditions. The physical and chemical properties of the formed material differ remarkably in different cases. In one case the fonned material may be perfectly flmd, in another soft and ^^scid, in another of intense hardness, and m some tissues a comparatively soft formed material is rendered very hard by being infiltrated with calcareous or siliceous matter. We shall now briefly describe the general structiue of the principal varieties of cells at different periods of their fife, and endeavour to show ho^v the fully developed forms in different PLATB X. GRANULES, GLOBULES, FIBRES, AND CELLS OR ELEMENTARY PARTS. Fig. 1. Fig. 2. Fig. 3. Fig. 4. a b Granules p, 69 Globules, p. 69. Fibrous Fibres, appearance. p. 69. Membrane. p.70. Fig. 5. Fig. 6. Fig. 7. Fig. 8. Complete division and sub-division of germinal matter, as in carbila|e, audtbe formation of formed material, Tbe space occupied by tbe three last drawings should be much larger than is represented, p. 75. Fig. 9. Fig. 10. Fig. 11. Fig. 12 . Division and sub-division of germinal matter, as in the production of a tissue with stellate cells (PI. Ill, Figs. 35 Sc 36). Each mass for a considerable time retains its connection with the other matter. — thus are formed the ' communicating tubes ‘ of some tissues. The space occupied by the three last Figures should be much larger than is represented, p. 76. Pig. 13. Fig. 14. Sub-division of masses of germinal matter in one direction, shelving how tubes and threads or filaments, differing from the ordinary formed material, may be produced, p. 76. Fig. 15. Most minute particles cf germinal matter, of ordinary mildew visi- ble under the of an inch, The smallest is less than the — of an inch, p. 77. Fig. 16. Pi'oduction of foimed material upon the s arface of germinal matter of mildew. X 1800. p.77. Fig. 17. Yig. IS. Further production of formed material in ordinary mildew. At a, a bad is formed by t±ie passage of some of the germinal matter through pores in the very thick layer of formed material. X 1800. p. 78. L. S. B.] [To. face p. 76. Harrisons' Impt.] OF THE SIMPLE CELL. 77 textures which exliibit such remarkable varieties of structure and arrangement, result. Of the structure and fonnation of the simple Cell. — The low microscopic fimgus which is known as common mildew is one of the simplest Kving tilings we are acquainted Avith, and well adapted for study. Some of the smallest particles of mildew capable of mdependent existence are represented in Plate I. figs 15 and 16, magnified 1800 diameters. The earhest conchtion of such a particle is shown in fig. 15. If the external mem- branous investment of a fidly developed spore, or of any of the growing branches (figs. 16, 17, 18, 19) was ruptm-ed, such minute particles would be set fi’ee m vast numbers and they constitute the living, growing matter, which may be coloured with carmine, w hil e the envelope, or outer part of the cells, does not become coloured. The sm’face of such a minute living particle becomes altered the instant it comes into contact with an or water. A tlfin layer upon the oirter part of the particle is changed hito a soft, pas- sive, transparent, homogeneous substance, exhibitmg a mem- branous character (cell wall), and this henceforth protects the matter withm, and at the same time, being permeable to fiuids, nutrient matter passes through it into the interior and under- goes conversion into living matter, which thus uicreases. The entne mass becomes larger. But this increase in size, it must be distuictly observed, is due not to the addition of new matter upon the external surface, but to the mtroduction of new matter into the interior. From tins it follows that as the mass increases in size the external membrane already formed must be stretched and rendered thinner ; indeed it would idtunately ruptme were it not that the same conditions which led to its production cause the formation of more new material of the same kind, which is continually added within that first produced. Thus the external membranous covermg is preserved, and m many cases very much strengthened by the new layers which are added. This process much resembles that by which upon a much larger scale the soft skins or hard shells of fruits are produced, and the rosy streaks upon the green covering of a yoimg apple probably mark the tissue which was first produced, although blending so com- pletely with the green portions which are probably of more recent formation. 78 THE SDIPLE CELL. From wliat has been already remarked it will have been infeiTed that the tluclmess which the formed material or cell membrane attains is determined mauily by the external cir- cumstances to which the living matter is exposed. If pabu- lum be abundant and external conditions (temperature, mois- ture, &c.) favourable, it passes tlmough the tlun external mem- brane and the living matter mcreases rapidly. If, on the other hand, external conditions be unfavorirable, a less proportion of pabulum passes tlmough the membrane, and at the same time the unfavom-able conditions cause the death of the living matter witlhn, layer after layer, mitil at last such a condition as that represented in figs. 17 and 18 results. It vull be obseiwed that the living matter is now reduced to a veiy small quantity and that the less this becomes, the more strongly is that wliich remauis protected by the increasing thickness of the envelope. Now, if the cell in the state above refeived to be exposed to the influence of a moderate temperature and moist atmosphere, and be placed under circumstances favoruable to growth, the external membrane vull become softened and expand. Under the influence of heat and moisture, the hard tissue will be rendered more readily permeable, and pabulum will reach the germinal matter in the interior more easily. The proportion of livhrg matter increases, and portions make theh way thi'ough natiual pores now opened, fig. 17, or thi-ough chance fissm-es in the softened envelope, and protrude fi-om the free surface, fig. 18. A very thin layer of tlie formed matter being produced on tlie surface of these protrusions, they are fr-eely supplied with pabu- lum, which readily permeates the thin layers of formed material, and grow very quickly ; and a vast extent of vegetable tissue may be produced, fr’om what was at first a very muiute particle of living matter, figs. 17, 19. From the above observations it seems clear that the formed material of which the envelope is composed results from the death of the living matter. This passive formed material was, in fact, once germhial matter, and m many structiues, especially at an early period of development, we may demonstrate the continuity of the germhial matter vuth the formed material. The successive layers of formed material are often veiy chstinctly seen in vegetable tissues, as, for example, in the sea-weed, fig. 21. The oldest tissue is most external, and this now dead EPITHELIAL CELLS. 79 tissue, is already being appropriated by organisms of another kind which are growing upon the surface, while within it passes iminterruptedly into the genxdnal matter. IMoreover from these observations it also ap]iears certain that the living or germmal matter is alone concerned in the active changes which take place. It may, therefore, be concluded that the smallest independent particle which exhibits vital phenomena consists partly of matter which is lifeless, but which at an earlier period was alive, and partly of matter which lives. If but the smallest particle of the latter remains in a living state, any amount of hvuig matter, and afterwards of hfeless tissue or formed material, may result. But if, on the other hand, all the living matter be dead, and only formed material remain, this is quite incompetent to exhibit the phenomenon of increase. In fact it does not live, it does not manifest any vital properties or powers, and although it is cer- tain that living matter must have existed a short tune previously, the formed matter has ceased to live, and can never again acquire the properties it has lost. Epithelial Cells . — Epithelial cells from the sm’face of the human tongue are represented in various stages of existence in figs. 20, a, h, c, and 22, a, b, c, cl. At first there is but a very thin layer of soft formed material upon the siu’face of the germinal matter. Fig. 20 a. The latter may divide, and each of the portions resulting would be uivested with a layer of this soft formed material. Thus the “ cells ” may increase in number. Each increases in size in consequence of the absorption of nutrient pabulum, which passes through the layer of formed material, as in the case of the mildew, into the germinal matter. Thus the latter increases. But at the same time a portion of the germmal matter undergoes conversion into formed material, which accmnulates, and as each new layer is formed iqDon the surface of the germinal matter, those layers of formed material already produced are stretched, and more or less incorporated with that last develojied, fig. 20, b and c. For a time the germinal matter increases, wliile at the same tune new formed material is produced. Both the constituent parts of the entu-e cell increase in amomit up to a certain period of its life, fig. 22, a, 5, c, but as new cells continue to be produced below, the cells already formed are gradually removed farther and farther from 80 EPITHELIAL CELLS. the vascular surface, while at the same time their formed material becomes more condensed and less permeable to nutrient matter. Hence each enthe cell ceases to increase in size. But as the mass of germinal matter still undergoes conversion into formed material, it becomes smaller as the cell advances in age, lig. 22, d. So that it is possible to judge of the age of a cell, irrespective of its size, by the relative amount of its component substances. In old cells there is much fonned material in pro- portion to the germinal matter, while young cells seem to he composed almost entirely of the latter substance. In veiy old cells the small portion of germinal matter still unconverted into formed material, dies, and the cell having by this time arrived at the surface, is cast off, a mass of perfectly passive hfeless formed material. It must not, however, he supposed, that formed material always exliihits the firm character of that present in the epithelial cell upon the sm’face of the sldn and some mucorrs memhrarres. iSoluhle formed rrraterial may be prodirced in vast quantity finm certain cells, which appear to rmdergo but very -slight change. Liver cells are represerrted hr fig. 23, a, h, c, d. These, hr health, are surromrded with a thick layer of very soft: formed rrraterial, the outer part of which is gTadually becomhrg dissolved and disintegTated, and probably oxidised ; par*t passes nff hr the form of very soluble biliary constituents, wlrile part is resolved irrto the albrrminous matter of the cell, and amyloid matter, which probably hr part becomes converted into sugar, fitill' even hr this case, there is a formation of new cells and a casting off of old ones, proceeding in the same definite direc- tion as irr the case of the epithelimn of the sru-face, but each individual cell, probably, lives for a much lorrger period of time. In figs. 24, 25 and 2(5, columnar cells of epithelium are represented. The orre from the rrrouth of the snake, in fig. 24, takes part irr the secretion of that slimy rnrrcus winch is formed in srrch ahrrrrdance in the mouths of many reptiles. Xutrient rrratter is taken up from the blood by the deep sru-face of the cell. This becomes living matter, and some of the particles of the latter upon the distal aspect, at a, become formed material, which pushes that which was produced before it, towards the mouth of the cell, at b. Straight lines are seerr passirrg towards the extremity, arrd the rrroverrrerrt of the particles, and PLATE II. AND POUMED, MATTIE OP Pig 20. b c THE CELL. Fig. 21. GEEMINAL OR LIVING. Fig. 19. Passage of germinal matter througli. pores in formed ■material, and foimation of tliin layer of formed mate- rial upon germinal matter, a. Showing the manner in which, fungi grow. X 1800. p. 78. Production and accumulation of formed material upon the sm’face of germinal matw;r in an epithelial cell, as m cuticle. X 700. p. 79, t Mnoos-FOHMiNG Cell, from the fauces of a hoa. showing germinal matter and the formed material within the envelope. The lower arrow shows the direction in which the nutrient pabulum flows towards the germinal matter, the upper one that taken by the formed material 13 it passes from the germinal mabter. p. 81. CoiTTiliTAR EpITEELTAL Ciiis, from the small inf^stine of a dog. showing the position of the germinal matter. a. the layer of highly refracting matter upon the surface. X 700. p. 8i. Fig. 22. Drawings illustrating the production of formed material from the germinal matter in epithelial cells, p. 79. Growing extremity of the stem of a sea-weed, show- ing the 'manner in which the germinal matter divides and the production of formed mater5.al, layer ■with- in layer, upon its surface The outermost layer is ihe oldest, and 5s undergoing disintegra'don X 3C0. p. 78. Ciliated, aitd Mucus- forming Cells from the fauces of a boa. X 700 p 80. Xi. s. S.] [To face p. SO. PORES IN CELLS. 81 the flow of nutrient matter, takes place constantly in one definite direction, as shown by the aiTOWs. These mucus- formmg cells are seen amongst the ciliated epithelial cells upon the tongue of the frog, and are very large and distinct upon the mucous membrane of the month of sei’pents, plate II, fig. 25a. It seems probable that the products of secretion fi-om these cells are wafted away by the vibration of the cilia of the adjacent cells, as they issue from the open end of the cell in which they were produced. In the case of the columnar cells covering the villi, lines are also seen, and probably depend upon the nutrient matter in the intestine being drawn towards the germinal matter of the cell in a linear direction (fig. 26a). These lines have been regarded by Kolliker and others, as pores in the layer of thick transparent material which seems to close what has been regarded as the free end of the cell, and it has been supposed that the fatty matter reduced to a state of very minute division by the process of digestion, passes through the pores in its way towards the lacteal ; but from the circximstance that this thick transparent matter forms in some cases a continuous layer over the free extremity of the cells, from which it may be peeled off, and the fact that it varies very much in thickness at different periods of the digestive process, it see:ns probable that the material in question is not a part of the cell at all, but is merely deposited fr'om the contents of the intestine, and caused to collect upon tbe free ends of the cells, perhaps by the currents of fluid which flow towards the “nucleus.” The fluid passing constantly in the same dii’ection would slowly dissolve the precipitated matter, and it would thus be trans- mitted to the germinal matter in the cell. That part of the germinal matter directed towards the opposite or attached extremity of the cell, woidd at the same time undergo change, and become converted into substances which would pass to the lacteal vessels upon the surface of the villus. The different position of the mass of germinal matter in these colrunnar cells, and those mucus-secreting columnar cells fi-om the frog’s or serpent’s mouth, should be noticed. In the intestinal cells, the pabidum flows from the free sm-face towards the attached extremity of the cells, but in the mucus-secreting cells it flows in the opposite direction, and it seems not im- G 82 CELL WALL — CELL CONTEXTS. probable tbat the different situation of the germinal matter in the two classes of cells may be determined by the difference ia the position of the pabulum in the two cases, figs. 25, 266. Many of the radiating lines apparent in cells seem to be due partly to the course taken by the pabulum as it flows in converging lines towards the geiminal matter, and partly to the manner in which the formed material is deposited layer within layer. In large masses of geiminal matter fissures or channels are sometimes seen by which the whole is mapped out into a number of smaller portions, each one of which will be batliedby the fluid as it passes along the channels. An example of the appearance alluded to is represented in plate III, fig. 27. In vegetable cells matter is deposited layer within layer, so as to thicken and strengthen the cell. This matter is, however, not deposited uniformly in every part, but the deposition is almost entmely prevented in the course taken by the cmrents of nutrient fluid which are continually flowing towards the germinal matter in the centre. As the process of deposition goes on, the channels gradually become narrower, but, as would be inferred, they are, except in veiy old cells, invariably of con- siderable width nearest to the germinal matter, and the “ cavity” of the cell, after the drjung up of the germinal matter, exhibits a stellate form, fig. 28. In fig. 32 is a portion of the thickened wall of one of the large cells in the potato which are desti- tute of starch, seen in fig. 31, under low power. These figm-es illustrate the same point. Cells or Elementary Parts consisting of tico or more kinds of formed material, -^Cell-^Vall and Cell- Contents. — In the mucus- secreturg cells referred to in the last section, two kinds of formed material were produced from the original geiminal matter of the cell, 1, that which has been called cell-wall, and 2, the pecuhar matter found in the interior usually teimed cell- contents. In plate III, fig. 29, are represented some of the young starch-holding cells of the potato. The so-caUed cell- wall is formed arormd, and now invests, the germinal matter, while the starch is deposited as small insoluble particles in its substance. In fact by the death of particles upon the sm-face of the livuig matter, the cellulose “ cell- wall” is produced, while, in consequence of the death of some of the particles frudher in- wards, and therefore under different conditions, starch results. STARCH AND FAT CELLS. 83 As the starch-holding cells increase in size, the starch granules become enlarged by deposition of layer after layer upon their external surface. They still lie embedded in the germinal matter, and are separated from the cell-wall by it. This outer portion of the germinal matter is Imown as the '•'•primordial utricle ” of the vegetable cell, see fig. 30. That the formation of the starch granules is a process closely allied to the produc- tion of the cell-wall seems proved by the circumstance that in some of the cells no starch is found in the interior, but the wall of the cell is greatly thickened by the deposition of a closely allied, but not identical material upon its internal sm-face, layer within layer, as represented in figs. 31 and 32. The fat cell, or adipose vesicle, is formed in precisely the same way, and fat may be deposited amongst the germinal matter of other cells, such as the cartilage ceU, and in nerve and other elementary parts in certain cases. The formation of fat in a fat cell, at diflerent stages of development, is repre- sented in plate III, fig. 33, a, b, c. Of Stellate Cells. — It has often been said that a cell sends or shoots out branches or processes at different parts of its circum- ference, and thus becomes star-shaped. The processes of stel- late cells are, however, never formed by any such process of growing or shooting “outwards” from the body of the cell. They are not as it were out-growths, which proceed from one cell and meet those protruded from neighboming cells, but the processes are drawn out as the masses originally close together become separated, in the manner aheady referred to in page 75, and represented diagrammatically in plate I, figs. 9 to 12. These diagrams are not, however, strictly true, for figs. 11 and 12 would really extend over a much larger space than in the drawing, for each of the numerous masses of germinal matter in figs. 7, 8, 11 and 12, corresponds to the larger masses seen in figs. 5, 6, 9, and 10. The large pigment cells of- the frog and other batrachia, and those forming the outer layer of the choroidal coat of the eye (lamina fusca), are good examples of stellate cells. The former vill be found in chap. Ill, the latter in plate III, fig. 34. Upon the sm-face of the fang of the tooth, in contact with the cementum or crusta petrosa, is a tissue of a very interestiug structm-e, which takes part in the formation of the cementum. G 2 84 OF STELLATE CELLS. It is composed entirely of branching cells, and is a most perfect example of a tissue consisting entirely of cells, the cavities of Tfliich, up to a certain period of development, communicate with one another by tubes. The stellate cells are here as distinct as they are in the pith of a rush. These cells and tubes do not, however, constitute an elaborate system of channels for the distribution of nutrient material to the tissue which intervenes between them, as Virchow and his school maintain. The struc- ture is represented in plate III, fig. 35. But pei’haps the most remarkable instance of the formation of fibres by the gradual separation of cells from one another occurs in the central organs of the nervous system. The fibres are structurally continuous with the body of the cell, and become ch-awn out as it were, as the cells, originally continuous, become separated fiuther and fui'ther from each other. At an early period of development the caudate cells in the cord and brain of man and animals, are represented by small and perfectly spherical cells, winch lie close to one another. The small quantity of formed material between them is so transparent that no structure can be discerned in it. As yet it exhibits no indications of fibres. It is, however, veiy probable that fibres exist even at this early period, but their transparency and delicacy of structure render them invisible. As development advances, the masses of germinal matter become separated from one another, while at the same time they increase in size, and the fibres, which, with the outer part of the cell, con- stitute the formed material, become more and more di-awn out in every part of then’ coiuse, mitil they are so very tliin as not to be recognizable vdthout the use of very high magnifying powers, and a special method of preparation. The numerous interlacing nerve fibres, of which the matter inter- vening between the cells of the adult brahi and spinal cord is almost entirely composed, are thus foimed. See fig. 36, plate III. Of Sphei'ical and Oval Nerve Cells . — A cell of highly complex structure connected with the sympathetic of the fi'og, is repre- sented in plate IV, fig. 40, but the manner in which this is produced will j)robably be understood if the principles already advanced have been carefully considered. This “ cell ” exhibits two fibres proceeding fi'om it, one being coiled sphally round the other. At an early period of development it consists only PLATE III. r GERMINAL OR LIVING, AND FORMED, MATTER OF THi CELL. Fig 27. Germinal Mattze. Cornea of tlie Salamander. X '<00 p 82. 30. A fully formed etavcb-holding cell of tlie potato. . X 350 p 33- Flg. 31. Pigment cells from tlie outer part of the choi'Oid. Human X 130. p. S3. Fig. 35. Stellate tissue on surface of fang of a human incisor tooth. X 700. p.84. Fig. 23. Vegetable cell, showing the manner in which secondary deposits are formed, and how the channels through- which currents flow to- wai'ds the 'nucleus' result. p 83 Fig. 31. One of the large cells, with thich walls, from the potato, containing veiy Uttle starch p.83 Fisf. 29. Five young starch-hold- ing cells Of the potato. showing OERMIKAL MAl TER. with small atai'ch globules precipitated amongst it. X 700. p 82. Fig. 32. A portion of the wall of one of the cells in Fig. 31, showing how the wall is thickened by the deposition of layer within layer. X 700. p. 82 Fig. 33. ■ Pat Ceiis,' showing the seat of formation of the fat ( foimed material), and the changes occurring in the cell as it advances towards its fully developed state. Prog. X 700 p.83. Fig. 36. a ' Cells.' Grey matter of human brain, showing ger- minal matter and formed material, a. capillary vessels. X 350. p. 8i [To face p. S4. L. S. E.] INTERCELLULAR SUBSTANCE. 85 of Rn oval mass of germinal matter, with either extremity of which a fibre is connected. The cell moves in a direction more or less at right angles to the line of the fibres, and as it moves it probably tui’ns round upon its own axis, in such a way that one fibre becomes coiled round the other, as represented in the drawing. This interesting form of cell will be described in the chapter upon the anatomy of nervous tissue, and it is only alluded to here as an illustration of the fact that every highly complex cell, like cells of very simple structm-e, consists of germinal matter and formed material. In the sympathetic gangha of the higher vertebrata the cells are more spherical and several fibres come off from each cell, but the peculiar twisting of one fibre round the other, as in the case of the cells from the frog, and some other batrachia, has not been observed. Of the so-called Intercellular Suhstance.—In. cartilage, tendon, and some other tissues there is no line of separation between the portions of formed material which belong to each respective mass of germinal matter as is the case in epithelium, but the formed material throughout the enthe tissue forms a continuous mass of tissue, matrix, or, as it has been termed, connective substance. From the apparent essential difierence in structure, it has been supposed that tissues of this character were developed upon a principle very different to that upon which epithehal structures were produced. It has been maintained by some that in cartilage a cell-wall, distinct fi:om the intervening transparent material, existed aroimd each cell, and it has been very generally concluded that the matrix was deposited be- tween the cells, and hence this was called “ bi^ercellular substance.” By reference to figs. 37 and 39, plate IV, it will be seen, however, that the so-called intercellular substance of cartilage and tendon exactly corresponds to the formed material of the epithehal cell, fig. 22, plate II. A “cell,” or elementary part of fully formed cartilage and tendon, consists of a mass of germinal matter with a pro- portion of the formed material around it. A line passing midway between the different masses of germinal matter would mark roughly the point to which the formed material corres- ponding to each particular mass of germinal matter extended, 86 FORMATION OF MUSCLE. and this wonld coiTespond with the outer part of the surface or houndaiy of the epithelial cell. In order to understand the tnie relation of the so-called intercellular substance of the cartilage and tendon to the masses of germinal matter, it is necessaiy to study the tissue at different ages. At an early period of development these tissues appear to consist of masses of germinal matter only. As development advances, the formed material increases, and the masses of germinal matter become separated further and fui-ther from one another. The appearances of a cell-wall arormd the germinal matter in the fully-formed tissue, and other alterations which occm-, and anomalous appearances which often result as age advances, can be even more readily mider- stood upon the view here advanced, than upon the intercellular substance theory which has been so strongly supported by some obseiwers. The above conclusions may be confinned by a careful exami- nation of white fibrous tissue. If equal portions of foetal and adult tendon be examined, the proportion of genninal matter in each will be foimd to be very different. There may be five or six times as much germmal matter in a certain bulk of foetal, as in the same bulk of fully formed tendon. The tendinous matter or tissue possesses no power of absorbing nutritive material and converting it into tissue like itself. All adchtions to its substance take place at those points only at which germinal matter exists. Yoiing tendon grows much faster than fully formed tendon, and in old tendon the masses of germmal matter have become reduced to very thin lines. In figs. 38 and 39, plate IV, specimens of foetal and fuUy developed tendon, fi-om the kitten and cat, are represented. Of the Formation of the Contractile Tissue of Muscle. — A. muscle “ cell” or elementary part, vfill consist, like that of car- tilage and tendon, of the so-called nucleus, with a portion of the muscular tissue corresponding to it. In general arrangement it closely resembles what is seen in tendon. The contractile material of muscle may be shown to be continuous with the germinal matter, and oftentimes a tliin filament of the trans- versely striated tissue may be detached with the oval mass of germinal matter still connected vdth it, showuig that, as in tendon, the germinal matter passes uninterruptedly into NUCLEUS — NUCLEOLUS. 87 the formed material. In the formation of the contractile tissue, the germinal matter seems to move onwards, while pos- teriorly, it gradually undergoes conversion into tissue. At the same time it absorbs nutrient material, and thus there may be no loss in bulk in a mass which has been instrumental in the production of a considerable amount of contractile tissue. The drawings represented in fig. 41, plate IV, will enable the student to understand the relation of the germinal matter to the contractile tissue, or formed material of muscle. On the Formation of Nerve Fibres. — Nerve fibres consist of formed material which is structurally continuous with that of the cells with which they are connected. At an early period of its development a nerve fibre appears to consist of a number of masses of germinal matter, linearly arranged. As develop- ment advances, these become separated fmther and fm-ther from one another, and the tissue formed between them con- stitutes the fibre of the nerve. Fig 42, plate IV, represents a dark-bordered nerve fibre from the frog at an early period of its development. Of Living or Geim^inalMatter. Of the ‘‘‘‘Nucleus’'' and “Nucleolus." — In the foregoing account of the structm-e and mode of forma- tion of tissue it has been shown that even the smallest living organism with which we are acquainted does not consist of matter in the same state in every part, but that the material within (germinal or living matter) possesses powers or properties of which the formed material, be it solid or fluid, is entii’ely destitute. Each mass of germinal matter with a proportion of the formed material around it, is a cell. All fiving cells consist of matter in these two very different states. The one state being an active condition vital; the other being a passive state in which no vital actions are manifested. The importance of this distinction is very great, because, as will presently be shown, the matter in the first or living state is that upon which all growth, multiplication, conversion, formation, in short life, depends ; wlule, in the second con- dition, the matter may exhibit very pecuKar properties, and it may have a most complex chemical composition ; but although it may increase by new matter being added to it, it does not grow or multiply, it does not convert or form — ^it does not 88 OF THE GERinNAL, OR LIVING live. Lastly, facts and arguments have been advanced -which show that all matter in the last or formed state -was once in the first or li-ving state, so that the properties it has acquired, and the characters it possesses as foimed matter, depend upon the changes which were brought about while the matter existed in the germinal or li-ving state. One mass of living germinal matter may dhdde into several, and thus cell- multiplication occurs. In all cases the multiplica- tion of the cell is due not to a growing in of the wall or formed material, but enthely to changes in the germinal matter. In many masses of germinal matter a smaller spherical mass, often appearing a mere point, is observed, and in many cases this divides before the di-rision of the parent mass takes place. This, however, is not necessary to the process, for it takes place in cases in which no such bocHes are to be seen, and it frequently happens that one or more of these smaller spots or spherical masses may appear in its substance, after a portion of ger min al matter has been detached fr-om the parent mass. These are to be regarded as new centres composed of Hving matter. 'Within these a second series is sometimes produced. The fii’st have been called nuclei, and those -within them nucleoli. Marvellous powers have been attributed to nuclei and nucleoh, and by many they are supposed to be the agents alone concerned in'tlie process of multiplication and reproduction. These nuclei and nucleoli are always more intensely colom-ed with alkaline coloiuing matters than other parts of the Ihdng or germinal matter, a fact which is alone sufficient to show the difference between a true nucleolus or new centre and an oil globule, which has often been vu’ongly termed a nucleolus. According to the view of cell- structm-e here advanced, nuclei and nucleoh are but new H-\ring centres appearing in pre-existing centres, and they may be sup- posed to mark the commencement of another series of changes in the matter in wliich they appeared, differing, perhaps, in some mhior particulars fr-om the fii’st changes which occiuTed. Sometimes a very defined fine shows precisely the limit of the two orders of changes. Although nuclei and nucleoh are germinal or li-ring matter, both are not undergoing conversion into formed material. The vital powers of nuclei are often not manifested at all, but under certain conditions the nucleus may increase, and exlhbit all the phenomena of ordinary PLATE IV. GERMINAL OR LIVING, AND FORMED, MATTER OP THE CEr.L. Fig. 37. E ig. 38. Fig. 39. <.:-iarir.6.GE. Prog. . Showing germinal matter and termed mai-erial ^inrer- c-’llular substance, of authors), with appearances resembhng a ceU-wall. X 700. p 85. Teitdon. Kitten at birth, X 215. p. 86. Teitoon. Young cat. X 215. p. 86. Showing germinal matter and formed material ( inter- cellular substance, of authors ) of tendon at different stages of development. Pig. 4i'). XfRVE Cft,!., with straight and spiral fibres. Fi'Og, p, 84. ■fig. 41. MoscLE. Germinal matter and formed material, a, the sarcolemma. 6, the contractile material. The arrows show the direction in which the masses of germinal matter are supposed to be moving. P 37. Fig. 4-2. a b c Fokmatton of Pus. To illustrate the changes resulting in the germinal matter of au epithelial cell from increased nutrition, showing the manner in which the geiminal mat-er of a normal cell, if supplied very freely vTith pabulum, may give rise to pus. p. 95. S. B.] [To face p. S3. AND FORSIED STATE OF MATTER. 89 germinal matter — new nuclei may be developed within it, new nucleoli within them so that ordinary germinal matter may become formed material, its nucleus growing larger and taking its place. The original nucleolus now becomes the nucleus, and new nucleoli make their appearance in what was the original nucleolus. The whole process consists of evolution from centres, and the production of new centres within pre- existing centres. Zones of colour, of different intensity, are often observed in a cell colom-ed with carmine. The outermost or oldest, or that wliich is losmg its vital powers, and becoming converted into formed material, being very shghtly coloui’ed, the most central part, or the nucleus, although fm-thest from the colouring solution, exhibiting the greatest intensity of colom\ These points are illustrated in plate III, fig. 36, and some other figmes. Germinal matter, in a comparatively quiescent state, is not unfrequently entirely destitute of nuclei, but they sometimes make their appearance if the mass be more freely supphed with nutrient matter. This fact may be noticed in the case of the connective tissue corpuscles, and the masses of germinal matter connected with the walls of vessels, nerves, muscular tissue, epithelimn, &c., which often exhibit no nuclei (or according to some, nucleoli), but soon after these bodies become supplied with an increased quantity of pabulum, several small nuclei make their appearance in all parts of the germinal matter. So far fi’om nuclei being formed first, and the other elements of the cell deposited around them, they make their appearance in the substance of a pre-existing mass of germinal mattei, as has been already stated. The true nucleus and nucleolus are not composed of special constituents differing firom the germmal matter, nor do they perform any special operation. They consist of living germinal matter. Small oil-globules, which invariably result from post-mortem changes in any germinal matter, have often been mistaken for nuclei and nucleoh. Of the increase of Cells . — Several distiact modes of cell increase or multiplication have been described, but in all cases the germinal matter divides, and is the only material in the cell actively concerned in the process of multiphcation. The process of division may, however, take place according to several different plans : — 1. The parent mass of germmal matter may simply divide into two equal parts, apparently in 90 OF THE INCREASE OF CELLS. obedience to a tendency of the portions to move away from one another after the original mass has reached a certain size. During this process, a constricted part is produced between the two separating masses, and this becomes thinner and thinner. This band, reduced to the thinnest line, may stiU connect the two, or it may break, and thus two independent living masses result from the division of one. 2. The parent mass, instead of dividing into two, may divide into three, four, or more equal parts. 3. From every part of the parent mass, protrusions, buds, or offsets may proceed, and however small these may be, each one, when detached, soon absorbs nutrient matter, and grows until it attains the same size as its parent. The formed material of the cell is perfectly passive in the process of increase and multiplication. If soft or diffluent, a portion of this may collect around each of the masses into which the germinal matter has divided, but it does not ‘ grow or ‘ move in and form a partition as has often been stated. When a septum or partition exists, it results not fr’om “ growing in,” but it is simply pro- duced by a portion of the geiTninal matter undergoing conversion into the foraied material of which it is composed. If the formed material of the ceU be hard and firm and unyielding, the germinal matter may make its way through some orifice in it, or at the weakest point, and escape in small particles which pass forth into the surrounding medium, or the separatmg portions may remain attached to the parent for a longer or shorter period of time, in the form of processes or outgrowths, as represented in plate II, fig. 19. In either case its outer part becomes converted into formed material, which protects it and modifies its rate of increase ; so that in no case can it be said that the cell, as a whole, divides, but the germinal matter alone is the material which is concerned in this as well as in all other active phenomena characteristic of cell life. If these simple facts be carefnlly borne in mind, the differences observed in the frilly formed textm-es, and the alterations occm-rmg in disease, receive a ready explanation. Of Development . — The greater number of Hviug beings result fr’om changes occin-ring in a minute body of apparently very simple structm'e, which is formed within the organism of the female parent, and in which active changes commence imme- diately after its impregnation has taken place. This body is tlie OF DEVELOPMENT. 91 ovum or egg^ wliich in many cases is provided -with a store of nu- txient matter, to be appropriated by the embryo dining tbe early period of its development. The essential portion of the ovum is exceedingly minute. It consists of germinal matter which, besides exhibiting special and peculiar characteristics in the com’se of its development, presents at every period of existence the same general characters, and possesses the same general properties as every other kind of germinal matter. The com- plete ovmn or egg of man and the higher animals exhibits a somewhat complex structure, and certain special parts have received distinct names which it may be well to give. Most externally is the homogeneous vitelline or yolk membrane^ which contains besides the yolk the essential parts, called the germinal vesicle, within which is the germinal spot, but these last probably correspond to parts found in the ordinary “ cell” — the centre of germinal or hving matter, termed the nucleus, within which is another centre termed the nucleolus. Before an embryo can be developed from the true ovum, im- pregnation must take place. It is now certain that in this process the male element (including the minute mass of ger- minal matter it contains ?) penetrates qmte into the substance of this small mass of living matter, and exerts an influence upon all the phenomena which are to succeed in it. The germinal matter of the ovum having thereby acquired new powers, divides and subdivides, and many series of new masses of germinal matter successively come into existence, disappear, and give place to new ones, each series being however the descendant of that which existed before, until at last a number of masses result, fr’om which the earliest traces of the new being or embryo are evolved. But there are many instances of beings of comparatively simple organisation fr’om which a new organism may result without the formation of a true ovum. Certain masses, and, in some cases, every mass of genninal matter in the body, may give rise to the formation of new and complete organisms. To this process there is some analogy even in the highest animals, and at all periods of life, in the development of simple masses of Hving matter into new tissues of very complex structm-e. We are quite unable to offer any clear and satisfactory explanation of the phenomena of development of a tissue or 92 DEVELOPMENT OF ORGANS. organ. It has been shown that the successive generations of cells produced are liueal descendants of the original cell or cells constituting the gerra-cell, while the arrangement, structure, and composition of the elementary tissue formed, differ materially as the development of the textme or organ advances. The successive production of formed material diflFering in com- position and properties from that previously produced may be accounted for upon the supposition that the successive series of masses of germinal matter possess different powers, but whether tliis power is acqufr-ed dm’ing the process of their development or transmitted directly fr-om the original germinal matter we have at present no positive evidence to show. That the new living centres which are developed within pre-existing Hving masses of germinal matter exhibit powers or properties not possessed by those within which they originated is certain, and it is probable that tliis origin of new centres within pre-existing ones takes place in all cases, and is an essential phenomenon in development. It is interesting to observe, that a mass of germinal matter which remains quiescent for a certain period of time and absorbs scarcely any pabulum, or perhaps actually none, may give origin to descendants from which special and complex structures and organs not previously formed may be produced ; w hil e if this very same mass were to be too freely supplied with pabulum, it would grow and multiply, and would exhibit the greatest activity, but not one of its very numerous descendants would be capable of giving rise to any structm’e. After existing for a very brief period they would die without leaving any evidence of their hairing possessed any structm-e- forming power whatever. Increase in power seems to be associated with the most limited change in germinal matter, while rapid change — increased vital action — seems to be in- variably connected with decadence in power. So that the formation of highly elaborate and complex tissues, organs, or organisms, is not in any way connected vith, or due to the influence of, the ordinary forces associated with lifeless matter, but it must be attributed to the influence of some peculiar power capable of controlling and directing both matter and force, and therefore of a nature very different to ordinary force. The laws governing vital phenomena are not yet understood. It will natm-ally be suggested that the different substances and THE CELL IN DISEASE. 93 different structures produced by germinal matter at different periods of development may depend upon tbe different sur- rounding conditions present when the changes occur. Tliis, however, is no explanation at all, for the sm’rounding con- ditions present, as well as the circumstances concerned in their production, are themselves complex. They are not simple external conditions, but are in part the result of external circumstances, and in part of a previous state of things in the establishment of which pre-existing vital powers associated with germinal matter played no unimportant part. Extending our inquiries still further back, we must at length discuss how the first formed material itself was produced, and it has been shown that this is due to the death of living matter under certain conditions, which is itself a highly complex phenomenon, and cannot be explained without supposing certain internal forces capable of causing the elements of the matter to arrange themselves in a certain definite manner, totally different to that in which the ordinary forces of matter would cause these elements to be arranged, — and certain influences operating from without (surrounding external conditions) tending to prevent the supposed internal forces from exerting their sway. The compo- sition, structure, and properties of the matter produced must, in fact, be referred to the influence of very different and antago- nistic forces acting upon matter from opposite directions. Of the Changes in the Cell in Disease. — It has been shown that of the different constituents of the fully formed cell, the ger- minal matter is alone concerned in all active change. This is in fact the only portion of the cell winch lives, while at an eai’ly period of development, the parts of the cell usually regarded as necessary to cell existence are altogether absent. The “ cell” at this period is but a mass of living germinal matter, and m certain parts of the body at all periods of life are masses of germinal matter, destitute of any cell-wall, and exactly resembling those of which at an early period the embryo is entirely composed. White blood and lymph corpuscles, chyle corpuscles, many of the corpuscles in the spleen, thymus and thyroid, corpuscles in the solitary glands, in the villi, some of those upon the surface of mucous membranes, and minute cor- puscles in many other localities, consist of living germinal matter. There is no structure through which these soft Hving 94 THE CELL m DISEASE. particles may not make their way. The destruction of tissue may be very quickly effected by them, and there is no operation pecrdiar to living beings in which germinal or hving matter does not take part. Any sketch of the structure of the cell would be incomplete without an account of some of the essen- tial alterations which take place in disease, and it is therefore proposed to refer very briefly to the general nature of some of the most unjDortant morbid changes. If the conditions under which cells ordinarily hve be modified beyond a certain hmit, a morhid change may result. For instance, if cells, which in then- normal state grow slowly, be supplied with an excess of nutrient pabulum, and increase in number very quickly, a morhid state is produced. Or if, on the other hand, the rate at which mrfltiplication takes place be reduced in consequence of an insufficient supply of nourish- ment, or from other causes, a diseased state may result. So that, in the great majority of cases, disease, or the morbid state, essentially dilfers from health, or the healthy state, in an increased or reduced rate of growth and multiplication of the germinal matter of a particular tissue or organ. In the process of inflammation, in the formation of inflammatory products, as lymph and pus, in the production of tubercle, and cancer, we see the results of increased mrfltiplication of the germinal matter of the tissues or of that derived from the blood. In the sh rinkin g, and hardening, and wasting, which occm’ in many tissues and organs in disease, we see the effects of the ger min al matter of a texture being supphed with too httle nutrient pabulum, in con- sequence sometimes of an alteration in the pabulum itself, sometimes of an rmdue tliickenhig and condensation of the tissue wliich forms the permeable septum, inteiwening between the pabulum and the germinal matter. The above observations may be illustrated by reference to what takes place when pus is formed from an epithehal cell, in wliich the nutrition of the germinal matter, and consequently its rate of growth, is much increased. And the changes which occur in the liver cell in cases of chrhosis may be advanced in illustration of a disease which consists essentially in the occur- rence of changes more slowly than in the normal condition, consequent upon less than the normal freedom of access of pabulum to the germinal matter. THE PUS CORPUSCLE. 95 The outer hardened formed material of an epithelial cell may be torn or ruptured mechanically, as in a scratch or prick by insects, or it may be rendered soft and more permeable to nutrient pabulum by the action of certain fluids which bathe it. In either case it is clear that the access of pabulum to the germinal matter is facilitated, and the latter necessarily grows " — that is, converts certain of the constituents of the pabiflmn that come into contact with it into matter like itself, — at an increased rate. The mass of germinal matter increases in size and soon begins to divide into smaller portions. Parts seem to move away from the general mass. These at length become detached, and thus several separate masses of germinal matter, which are embedded in the softened and altered foi-med material, result. These changes will be understood by refer- ence to flg. 43, a, h, c, plate IV. In this way the so-called inflammatoiy product pus results. The abnormal pus- corpuscle may be produced from the germinal or living matter of a normal epithelial cell, the germinal matter of lohich has been supplied with pabulum much more freely than in the normal state. It will be seen how easily the nature of the changes occur- ring in cells in inflammation can be explained if the artificial nomenclature of cell-wall, cell-contents, nucleus, be given up. In all acute internal inflammations a much larger quantity of inanimate pabiflum is taken up by certain cells and converted into living matter than in the normal state. Hence there is increase in bulk. Cells of particular organs, which hve very slowly in health, live very fast in certain forms of disease. More pabulum reaches them, and they grow more rapidly in consequence. In cells which have been grovdng very rapidly and are retimiing to then* normal condition, in zvhich the access of nutrient pabulum is more restricted than in the abnormal state, as is the case in normal cells passing from the embryonic to the fully-formed state, the outer part of the germinal matter under- goes conversion into formed material, and this last increases as the supply of pabulum becomes reduced. We will now enquire what alterations can be observed in cells, the formed material" of which, under normal conditions, be- comes quicJdy resolved into other soluble constituents if these cells be placed under cfrcumstances which caused the formed 96 THE CELLS IN PNEUMONIA. material to become harder and less permeable to nutrient matter than in health. The formed material which enters into the for- mation of the liver “ cell” is soft, moist, and readily permeable to certain nutrient matters. There is no cell- wall, but the outer part of the formed material is gradually resolved into soluble biliary matters, which pass down the ducts, and into amyloid and saccharine matters, which permeate the walls of the vessels and enter the blood. To make up for the disintegration of the outer part of the formed material, new formed material is produced in the interior of the cell from the germinal matter, and the germi- nal matter which undergoes this change is replaced by new ger- minal matter prodrrced from the pabulum that is absorbed. If such cells and their descendants are bathed vdth improper pabrrlurn, and especially Avith substances which render albu- minorrs matters insoluble, or possess the property of hardening them, they rrecessarily diminish in size, in consequence of the formed material becoming less permeable, less nutrient matter is taken up ; and of com-se, as the formed material becomes hardened, less disiirtegration takes place, the quantity of secre- tiorr, which really consists of the products resulting from disinte- gration, is much diminished, and the amormt of work performed by the cell is reduced. Under the supposed conditions the cells slnink in size and become more firm in textm-e. ]\Iany gradually waste, and not a few die, and at length disappear. These seem to be the essential changes which slowly take place in the hver cells in Cirrhosis, and to these changes in the cells, the striking shrmking and condensation of the whole hver, so charactei-istic of this disease are due. From these observations it follows that disease may result in two ways — either from the cells of an organ growing and multiplying faster than in the normal state, or more slowly. In the one case, the normal restrictions under which growth takes place are diminished ; in the other, the restrictions are greatly in- creased. Pneumonia, or inflammation of the lung, may be adduced as a strildng example of the fu'st condition, for in this disease millions of cells are very rapidly produced in the air cells of the lung, and nutrient constituents are diverted from other parts of the body to this focus of morbid activity. Contraction and condensation of the hver, Iddney, and other glands, harden- ing, shrinkhig, and wasting the muscrdar, nervous, and other MORBID CHANGES IN THE CELL. 97 tissues, are good examples of the second. The amount of change becomes less and less as the morbid state advances, the whole organ wastes, and the secreting structure slminhs, and at last inactive connective tissue alone marks the seat where most active and energetic changes once occurred. It is easy to see how such a substance as alcohol must tend to restrict the rapid multiplication of the cells if the process is too active, and how it would tend to promote the advance of disease in organs in which rapid change in the cells charac- terises the normal state. We shall necessarily be led by these considerations to the conclusion that the rate of growth of cells in disease may be accelerated or retarded by an alteration in the character of the pabulum wliich is transmitted to them, and we shall be led to search for remedies which have the property of rendering tissues more or less permeable to nutrient fluids, or which alter the character of the fluid itself. Such considerations are of interest not to the physiologist only, but they have a very important bearing upon the practical treatment of disease. It has been sought in this chapter to establish the fact that all formed matter results from changes in the germinal matter, and that the action of the cell consists really in a change from the livhig to the lifeless state of the matter of which it is composed. Tlois change takes place in the same definite chrec- tion in all cases. The changes in the germinal or living matter must be attributed to the influence of a supposed vital force or power by which the matter is temporarily affected. The products formed by the cell do not depend upon any metabolic action exerted by the cell-wall or nucleus upon pabulum, nor are they simply separated fr-om, or deposited by, the blood. The matter has passed through the living state, and by ceasing to live mider certain conditions, the lifeless formed materials in question have resulted. The view here advanced leads us to look upon the ‘living cell’ as a minute body, consisting partly of living matter influenced by vital force, partly of lifeless matter resulting fr-om the death of the first, in which chemical and physical changes occiu', and these may be modified by the influence of sm-rounding substances and external forces. H CHAPTER II. or coMPOSiTiorr . — chemical composition op geeminal mattee and EOEMED MATEEIAL. SKETCH OE THE CHEMICAL CHANGES OCCUE- EING IN THE SIMPLE LINING CELL. — CHEMICAL CHANGES IN THE OEGANISM AT DIEEEEENT PEEIODS OP DEVELOPMENT. — OP THE BLOOD. — OP THE CHANGES EESULTING FEOM OXIDATION. — OP THE POEMATION OP VAEIOUS COMPOHNDS IN DIFPEEENT TISSEES AND OEGANS OP THE BODY. THE COXTEESION OP PABULEM INTO BLOOD. ANlMiUj bodies are composed of solids, liquids, and gases, tlie last being held in solution in the liquids. Solids and Liquids . — The solid textures contain only about one- fourth of solid matter, the rest is 'n'ater. The great shi'inldng which they experience when dried, shows how much of then’ bulk they owe to tliis combination ; and parts thus shrunken swell out again, and assume then' natural condition on the addition of water. Nor does this swelling out after shrinking occur in water alone. The most soft and delicate tissues will regam then- former volume, even if placed in very viscid fluids as syrup or glycerin, of much higher specific gi-avity than the tissues immersed. This seems to be due to the inherent elastic property in the tissue itself, in virtue of which its anatomical elements tend to assume the position and form they originally held in the natmul state of the textm'e. The quantity of water existing, even in the hardest tissues, is far greater than would be supposed. The mummy of a large man is of very trifling weight. Blumenbach possessed the entire perfectly dry mummy of a Guanche, or aboriginal in- habitant of Tenerifie, presented to him by Sm Joseph Banks, which, with all its muscles and ^’iscera, weighed only seven pounds and a half Water is one of the most important constituents of animal bodies. It forms foin'-fifths of then- nutrient fluid, the blood ; and it gives more or less of flexibihty and softness to the various solid textiu’es. The loss of it in great quantity speedily puts a stop to vitaf as well as chemical and physical, action. Germinal matter is itself semi-fluid, and the very active move- OEGANIC AND INORGANIC IIATTERS. 99 ments of the portions of which it consists, which seem essential to the living state of matter, could not take place unless every portion of a living mass were free to move m fluid, or contained so much fluid as to be readily moveable, not only around, but through other portions. Water is a solvent of many organic and inorganic matters ; it is, therefore, a valuable medium for conveying these substances to and from the several textiles and organs. Moreover, it dissolves various gases. Oxygen is thus carried in solution to various parts of the body, where it acts upon certain of the insoluble solids, which are thereby oxidized and rendered soluble. The substances thus formed are carried away hi solution. Water plays a most important part in the various chemical operations of the body ; and by its addition to or subtraction from a particular compoimd, an alteration in its properties may be induced. The various methods at om- disposal for separating fr-om one another the different compounds formed by living beings, and of resolving these into their ultimate elements, belong respectively to the departments of proximate and ultimate analysis. (See page 5.) Organic and Inorganic Matters. — The solid textures and the soluble substances held in solution in the fluids of the body, consist of two classes of compounds, spoken of as organic and inorganic. But many of the so-called organic substances have been prepared artificially in the laboratory, and they cannot therefore be considered as pecuhar to living beings. The organic matters are decomposed by a red heat, while the inorganic or mmeral substances are not destroyed by incineration. Organic compounds are composed of certain of the non- metallic elements, and pidncipally of oxygen, hydrogen, nitrogen, and carbon. These elements, in the living body, are combined so as to form complex but often unstable com- pomids, and, under certain conditions, by hydration or by the appropriation of oxygen and other substances, these organic compounds may be afterwards split up, as it were, into much simpler but more stable bodies. The organic compounds which enter so largely into the composition of the various solids and liquids of living beings, differ fr’om one another, in composition and properties, in the H 2 100 THE CHEMICAL CHANGES most remarkable manner. Many have been placed by chemists in certaia artificial gronps, but liithei’to it has not been found possible to aivange more than a very few in a naturally connected chemical series. The corresponding substances in different animals exliibit differences of properties and com- position ; and in disease, the characters and composition of the chemical components of the tissues and fluids undergo remark- able variations. Nor has any definite relation been proved to exist between the chemical composition, form, structure, and properties of organic, any more than inorganic bodies. Of the different Constitution of the Corresponding Substances in different MjimaZs.— There are many modified forms of albmnen, fibrin, and casein, several different varieties of starch, sugar, fat, &c., numerous different forms of haemato-ciystallin, biliary acids, &c., and the difference is not explained by the varying conditions rmder which these substances have been produced, but must be ascribed partly to these and partly to the difierent properties and powers of the germinal or living matter taking part in their production. We have already observed that the tissues which precisely correspond to one another in different animals exhibit minute, but still very appreciable, differences in their stricture, and we should, therefore, be led to anticipate that differences in the an-angement of their elements, and in their chemical properties, would also exist. Nor are these differences in chemical constitution confined to allied organic compounds, they are found to obtain also in the case of many inorganic salts. Chemical Substances composing the Tissues, not found in the Blood. The chemical compounds entering into the formation of the solid tissues and liquid secretions have not for the most part been detected in the blood or nutrient pabulum, and there is reason to think that they have resulted, not from chemical changes taking place while the solutions traversed vessels or permeated membranes, but that they are the consequence of changes occurring in the temporaiy or living state, through which, as has been already shown, the various elements of the food must pass before they form a constituent part of the tissues or nutrient fluids of hAung beings. The germinal or living matter is alone concerned in this process, and different kinds of genninal matter, although, as far as we can tell, having the same com- OCCURRING m THE CELL. 101 position, and certainly nourislied by the same pabulum, may give rise to the formation of very different compounds. It may, indeed, be regarded as certain, that from a nutrient fluid common to them all, the masses of germinal matter of different textures take certam constituents which become converted into the tissues, or the constituents peculiar to the different secretions. The idea that these very substances existed in a modifled form in the blood, and were merely separated fi.’om it by a sort of attractive force existing in the cells, will probably soon give place to the doctrine now supported by so many facts, that, from the same chemical constituents, difierent kinds of hving matter may prepare or produce compounds very difierent in composition and properties from one another. F or the crude notion that the formation of tissues was akin to the process of crystallisation, we must substitute the conclusion that the real cause of the peculiar composition and properties of the substances formed, is to be sought for in the living matter itself. And as the evidence that the wonderful changes occmTuig in this matter are due to the influence of some pecuhar force or power, becomes stronger, it is to be hoped that com- parisons between living things, and crystals laboratories or steam-engines, will no longer be insisted upon. OF THE CHEMICAL CHANGES OCCURRING IN THE CELL. Before we can hope to form a correct idea of the complex chemical phenomena occurring in man and the higher animals at any period of existence, we must have a knowledge ef the general chemical changes occmTing in the cell. Regarding the “ cell” as consisting of — 1. Germinal or livhig matter. 2. F ormed matter ; and 3. F ormed matter midergoing disintegi’ation, the consideration of the chemistry of the cell naturally falls under three heads ; — The Chemistry of the germinal matter, the Chemistry of the formed material, and the Chemistry of the substances resulting from the oxidation of, or other changes in the formed material. This will, therefore, be discussed in the flrst place, and then we shall have to consider the more complex chemical phenomena occurring in man and the higher animals at difierent periods of existence. The Chemical Characters of the Living Germinal Matter. — Just as the various tissues of living beings result from changes 102 THE CHEMICAL CILINGES occurring in a perfectly transparent, structureless, germinal or living matter, so the numerous chemical compounds character- istic of different living organisms, and different tissues and organs, result from changes takuig place in this same trans- parent material. Few substances which enter the organism of a living being pass through unchanged, without having then' elements completely rearranged. There is reason to heheve, that even the elements of many mineral substances become separated from one another, and recombined in the body. It is remarkable that the germinal matter fi’om the most dissimilar living beings presents the same characters, so that it is not possible to premise, ff’om any microscopical or chemical examination, what will be the nature of the substances formed from any given mass of germinal matter. The general characters of germinal matter have been already refeiTed to, and the student will readily form a notion of its simple trans- parent, jelly-like appearance, if he examines, rmder a liigh magnifying power, a white blood corpuscle, or the transparent moving matter forming the substance (sarcode) of a common amoeba, specimens of which can ahvays be obtained ft'orn water, m which a little dead animal tissue has been placed, left to stand for some days m a light part of the room. There is no living or germinal matter which does not con- tain oxygen, hydrogen, nitrogen and carbon ; and although some of the other elements are often present and are, un- doubtedly, of great importance in special cases, the above are constantly foimd and seem essential to the very existence of vital changes. It is comparatively easy to ascertain Avhat elements exist in the h\dng matter, but it is not possible to demonstrate how these are combined, or if they are combined at all. Of the relation which these elements bear to one another in the living matter, we know indeed nothing ; but since every land of Ihdng matter exhibits the same characters, it seems probable that diuing this temporary hving state, the elements do not exist in a state of ordinary chemical com- bination at all. Their ordinary attractions or afiinities seem to be suspended for the time. That the matter is in a state of active molecular change, or ’^dbration, is certain, but it is doubtful if chemical combination is possible as long as the matter lives. No chemical compound or elementary substance, OCCURRING IN THE CELL. 103 as far as is yet known, exhibits life, or posesses vital properties or endowments. It is perhaps as impossible to conceive a living chemical compound as it is to conceive a living elementary atom. And the chemist who supposes that he can analyse living matter is in error, for he examines not the matter which is alive, but simply lifeless compomids resulting from its death. When the living or germinal matter is converted into formed matter, combination of its elements takes place, free oxygen being in some cases absorbed at the moment, and compounds of such complex nature result that the efforts of chemists to ascertain the chemical relations or the exact composition of many of them have not hitherto met with success. And it often happens that the chemical compound undergoes fru'ther change after it has been formed, so that the substance which we submit to examination in om’ laboratories, is not of the same chemical composition as when it was first produced by the cell. Of the Production of Chemical Compounds (formed material) from Germinal Matter . — It is remarkable that the elements of every kind of germinal matter, when its life is suddenly destroyed, should combine to form compounds closely alhedto one another in chemical composition and properties, and that an acid reac^ tion should be always developed. From every land of germinal matter a material which coagulates spontaneously, and one which is coagulated hy heat and nitric acid may be obtained. The first of these is fibrin, and the second is albumen. Fibrm, albumen, water and certain salts, may be obtained from every kind of germinal matter. All kinds of germinal matter also yield fatty matters, and these continue to increase in quantity for some time after death has occurred. As is well known, the “ nuclei” (germinal matter) of all organisms and tissues which have been kept for some time in preservative fluids become granular, and usually distinct globules are to be seen. These granules and globules are due to the formation of fatty matter from the germinal matter itself, or fr'om the albumen, fibrin, and other substances immediately resulting from its death. It is very remarkable that the general characters, if not the chemical composition, of this fatty matter, should be the same in the case of every kin d of germinal matter in both vegetable and animal tissues (see page 110). It would appear that the elements of every kind of germinal matter are so disposed or 104 SUBSTANCES RESULTING FROM arranged duiTQg the living state, that they may combine to form water, albuminous matters including fibrin, fatty matters, and salts. Although water may be obtained from every kind of Ibfing matter it is doubtful if water in its ordinary condition exists while the matter is alive, for this living matter may be ex- posed to a temperature considerably below the freezing point of water without becoming solid, and it is probable that death must occur before the actual congelation of the germinal matter, or of the water it contains, can take place. The formation of all chemical compounds seems to be con- nected with the death of the germinal matter, and different substances will result according as the death is sudden or gradual, that is, according as the germinal matter dies suddenly en masse or more slowly, particle by particle. And it is probable that in the comparatively slow molecular death, a certain amount of oxygen is taken up at the moment of combi- nation, and this alone would give rise to very different con- binations to those which occin- w'hen the living matter is suddenly destroyed, little or no oxygen being present. An altei’ation in the conditions under w’^hich death takes place will be associated with a difference in composition of the mateiials produced; but it must not be supposed that external condi- tions alone determine either the form, composition or properties of the resulting substances. When germinal matter becomes resolved into formed mate- rial, other compounds are produced besides the special ones which characterise that particular kind of germinal matter ; and a product wliich largely predominates mider certain ch-cum- stances may be produced hi mere traces under other conditions. For instance, the germinal matter of the fiver cell of some animals becomes resolved into amyloid matters and bihaiy matters -with mere traces of fat. In others, fat which accumu- lates seems to form the main portion of the formed material produced. In man, imder some chcumstances, bile and amyloid appear to be produced ; under others, fat seems to be the main product as in the fish. And various secondary morbid changes are brought about according as the formation of fatty, amyloid or sacchaiine matter predominates. The natime of the pabu- lum doubtless affects the composition of the formed materials THE DEATH OF GERMINAL MATTER. 105 produced by tbe cell, but tbis is only one of the many circum- stances influencing the result. The products resulting from the changes of germinal matter seem to be almost inflnitely varied, and those substances which exactly correspond in difierent animals do not exhibit the same composition. Even in the case of animals very closely allied zoologically, great differences are noticed. The bile, blood, milk, fat, &c., exhibit great difference in composition, although they possess many characters in common, and perform the same offices in the different animals respectively. There appears to be a resem- blance generically, associated with strikuig specific differences. The germinal or living matter of all living beings, vegetable as well as animal, contains nitrogen, and the broad difference between the changes in the animal and vegetable kingdoms seems to be that in the first a large proportion of the nitrogen entering mto the composition of the germinal matter, enters into combination with other elements in the resulting formed substance ; while m the latter, as a nfle, the nitrogen although necessary to the germmal matter, does not enter into combina- tion, so that while the animal reqnires a large quantity of nitrogen in its food to supply that which has been converted into various chemical compormds formed by the germinal matter, the plant needs but a very small proportion, because so httle enters into the composition of the formed material pro- duced. The tissues of fungi, however, contain a considerable proportion of nitrogen. Certain saline or inorganic substances form constant and very important constituents of the animal body. Although it is possible that vital changes may continue to go on in the ab- sence of saline substances, it is certain that the tissues, upon the integrity of which the dmution of life depends, could not be produced or nourished without them. Chloride of sodium is one of the most important. This salt is always present m large proportion in all embryonic tissues, and it is probable that it is mtimately concerned in some of the active changes taking place m the germinal matter itself. Whenever germinal matter is growing and multiplying very rapidly in the human organism, chloride of sodium is present, and it is probable that in the lower organisms and plants, other saline substances are of equal importance in corresponding processes. 106 OF THE CHEMICAL CHANGES Of the Chemical Changes taking place in the Formed Material after its production. — Most important alterations may occur in the formed material after it has been produced. In some cases it undergoes condensation, during which process structm-al pecu- liarities manifest themselves. Gradually, the formed material may become dry, after which, little alteration takes place. But in the soft, moist formed material, produced by many of the cells in the internal organs of the body, the most important changes occur. In some cases the formed material is perfectly fluid, and splits up into soluble or gaseous substances as soon as it is produced. In many instances, the elements of the formed material, although tliemselves insoluble, gTadu- ally undergo conversion into soluble compounds, in con- sequence of the action of oxygen, which combines with certain of the elements. If, in any case, the supply of oxygen be insufiicient to convert the whole of the matter present into fully oxidised and completely soluble compounds, its elements may combine to form less soluble substances, which accmmflate, and in many tissues give rise to morbid change. Hence it is of the utmost importance that the disintegrating processes in the intex’nal organs of the higher a nim als shoifld be in a state of due activity, for miless the formed material be constantly traversed by fluids rich in oxygen, the products necessaiily resulting from disintegration are not fully oxidised and quickly removed in a very soluble form, but yemain in the tissue in other states of combination, interfering with its function or even causing suspension of its action altogether. F or instance, by the imperfect oxidation of the elements resulting fi’om the disintegration of muscular and other tissues, fatty matters result, and if the conditions giving rise to their production continue, these accumulate, leading to various morbid con- ditions. Insufiicient oxidation seems to be the main cause of the accumulation of mic acid, oxalates and fatty matters in the blood. Leucine, tyrosine, sugar and many other sub- stances result from the orchuary chemical changes being hiter- fered with. Their formation is perhaps due to the existence of conditions which interfere with the combination of the due proportion of oxygen with the elements of the compounds wliich unites with them under ordinary chcumstances. IN THE SIMPLE CELL. 107 Sketch of the Chemical Changes occurring in the simple Cell . — Carrying out our inquiry according to the plan adopted in the chapter devoted to the consideration of structure, we may now consider the chemical changes which occm’ during the life of a simple cell, and we propose to select, for the purposes of inquiry, one of the lower microscopic fungi — the yeast plant. If a minute germ of this vegetable organism he placed in a solution containing a trace of albuminous matter, a small quantity of phosphatic salts, and sugar in the proportion of about 4 parts of sugar to 20 of water, and the whole be exposed to the air, at a temperature of about 80°, growth will take place. The germ will give rise, in a short time, to many bodies lilce itself, and the sugar will be gradually appropriated by the plant, which will increase in size, divide and subdivide, until the greater part of the sugar has been removed. Now, in this process, as the sugar disappears, and the yeast corpuscles multiply, while oxygen and albuminous matter are taken up, carbonic acid and alcohol are evolved in considerable quantity. This is the process known as alcoholic fermentation, and there is no doubt that the formation of the alcohol and carbonic acid is ultimately comiected with the growth and multiplication of the yeast cells, but the precise manner in which the decomposition of the sugar is effected is still unknown. Many chemists, following Liebig, probably regard the change as too purely chemical. Because putrefying blood, white of egg, &c., caused the fermentation of sugar, Liebig came to the conclusion that yeast was a sort of vege- table fibrin, albumen, or caseine in a state of decomposition. We now know that putrefying substances themselves cause fermentation, only because they contain living organisms. It was supposed that the yeast cells effected the decomposition of the sugar without necessarily coming into actual contact with every portion of sugar, by virtue of some action, the nature of which was not explained, but which was spoken of as metabolic action. Mitscherlich proved, however, that for the change to occur, the living cells of the yeast plant must come into actual contact with every particle of syrup to be decomposed. We may now consider this question from a somewhat different point of view. The germinal matter of yeast, like other kinds of germinal matter, contains nitrogen and exliibits 108 OF THE CHEMICAL, CHANGES an acid reaction. An albuminous substance may be obtained from it, as well as from all other kinds of germinal matter. The formed material of yeast — the envelope or cell-wall pro- duced from the germinal matter (see page 77), consists, according to Miilder, of a substance closely allied to cellulose in composition. It is, then, a fact, that by the grovdh and multiplication of the germinal matter of the yeast cell, cellulose, carbonic acid, alcohol, a little lactic acid, and some other sub- stances of less importance result ; but the precise manner in which all these substances are produced, has not been de- termined. From what has been already stated, in chapter 1, it would appear probable that the nutrition and growth of the yeast plant occur somewhat as follows : — the cell takes up a certain quantity of sugar, Avith a trace of albuminous matter salts and perhaps oxygen, and these imdergo conversion into germinal matter. At the same time the germinal matter already produced upon the sm’face undergoes conversion into formed material (^see page 77), and this formed matter im- mediately becomes resolved into cellulose, which is precipitated, and carbonic acid and alcohol, which are soluble. All these sub- stances probably result from the death of the germinal matter of yeast. The cellulose forms the insoluble capsule, envelope, or cell-wall, wliich is permeable to fluids in both dh-ections. The carbonic acid and alcohol being soluble, pass into the surrounding water, and at length escape. Under certain con- ditions, the proportion of carbonic acid and alcohol formed is great, and the amount of cellulose small, while other conditions seem more favom’able to the production of cellulose matter. The germinal matter of some vegetable cells gives rise to cellulose upon the surface, while vithin starchy matter is deposited. In other cases chlorophyl and other coloming matters result from changes occuning in the germinal matter (primordial utricle) in the ulterior of the cell, after the forma- tion of the cellulose wall upon its surface. In all these cases the formation of the peculiar and characteristic substance wliich accumulates, is accompanied by the formation of soluble and gaseous matters which escape. The germinal matter of the cells of the leaves and flowers of plants becomes resolved into pecuHar coloured compounds, and these are often diffused through the germinal matter, but sometimes collect upon its IN THE SIMPLE CELL. 109 surface. The germinal matter itself is never coloured, for the soluble coloured matter may be separated from the colourless germinal matter. The formation of chlorophyl from germinal matter may be studied in many of the lower plants, and its separation from the germinal matter effected. In like manner coloured matter may be separated from the colourless germinal matter of many of the young red blood corpuscles of mam- malian animals which consist principally of germinal matter. It is probable that in animal cells also, the formation of several chemical compounds from the germinal matter at the same moment occurs. In the liver cell, for instance, fom’ distinct classes of solid matters seem to be produced by the re-arrange- ment of the elements of the germinal matter — resinous biliary acids, fatty matter, albuminous matter and amyloid substance. The relative proportion of these different substances produced seems to vary according to different circumstances. Sometimes the quantity of fatty matter is enormous, while in other instances only a mere trace is produced, and the same remark applies to the other constituents. If, according to the view generally entertained, the different substances entering into the composition of a complex secre- tion, are separated from the blood and afterwards altered in composition by some unexplained action of the cell, or its nucleus, how are we to account for the fact of distinct classes of substances being separated, or separated and altered, by the agency of one and the same cell or nucleus ? The oily, saccharine, and albuminous constituents (butter, sugar, caseine) of milk, have not been discovered in the blood, and there is only one kind of cell to form these three classes of sub- stances. Does the same cell-wall or nucleus separate from the blood at the same time oily, starchy or saccharine, and albununous matters, and convert these into the particular con- stituents of milk, or are they separated one after the other? Upon either supposition it would be extremely difficult to accoimt for the actual facts, while, if, as has been rendered probable by different arguments already advanced, the con- stituents, absorbed from the blood, become first converted into germinal matter, which at length becomes resolved into these three classes of substances, at least a more plausible theory, if not a complete explanation, of the process, is arrived at. 110 CHEMICAL CHANGES OCCUKRING AT The study of the circumstances under which these different classes of substances are produced by a single cell, and more especially the careful investigation of the conditions which determine a variation in the relative proportion of the different constituents, will greatly contribute to advance our knowledge of many of the most important morbid conditions, and thus give to practical medicine a stronger title to be considered a science. OF THE CHEMICAL CHANGES OCCHREING IN THE ORGANISM AT DIFFERENT PERIODS OF DEVELOPMENT. Although we are quite unable to give even a veiy imperfect idea of the chemical phenomena occmTing in man at different periods of his development, we shall make the attempt to employ the imperfect data we possess, and consider some of the most important chemical changes occmTing in the organism from the point of view already indicated. At the earliest peiiod of its development, the simple mass or collection of masses of germinal matter of which the embryo is composed, exhibits a chemistiy simple as compared with that of the organism when its development is more advanced. The formed material resulting from the germinal matter, seems to consist prhicipally of albuminous and fatty materials, vdthout any substance capable of yielding gelatin. Saline matters may be detected, and it is certain that amyloid matter soon makes its appearance among the chemical substances produced in the embryo. The albuminous matter is closely allied to ordinary albumen, and with it is associated a small quantity of a coagulable matter, probably identical with fibini. Fatty Matter . — Little is known concernhig the actual chemical natine of the fatty matter developed at the earhest periods of embryonic life, but the compound substance known as myelin, makes its appearance very early. The oil globules so commonly seen in germinal matter of various kinds, especially at an early period of development, and which have been some- times termed nucleoli, consist of this foim of very peculiar fatty matter. I have ah'eady shown that cholesterin, one of its constant constituents, is present in the oil globules found in various cells m fatty degeneration, and more recent examina- tions, vdth the aid of the highest powers, have displayed the masses of myelm, exhibiting then- characteristic refraction, then- DIFFERENT PERIODS OF DEVELOPMENT. Ill double contours, and twisted forms amongst the germinal matter of pus, cancer, epithelial and other cells (plate VIII, figs. 73, 74), and there can be little doubt from the fact, that Beneke has detected myelin in the young shoots and actively growing buds of the potato, asparagus, and many other plants, that myelin is the particular form of fatty matter which imme- diately results from changes occm-ring in germinal matter. The reaction and chemical characters of this substance are described in page 148. The Saline Constituents consist principally of chlorides, but a small quantity of alkaline and earthy phosphates are also present. The chloride of sodium performs some important office in connection with cell multiplication, as we find this substance invariably present in considerable proportion at an early period of the development of all animal tissues, when the masses of germinal matter are growing and multiplying rapidly. It is possible that salt may be serviceable at the earliest periods of nutritive change, by its property of rendering albumen less viscid, more diffusible, and capable of being very readily appro- priated by the growing germinal matter. Amyloid Substance (CgHj^Oj). — As the formed material ex- hibits firmer consistence and structural peculiarities, a gelatin- yielding substance is produced. But vdth this is developed much matter of an amyloid or starchy character, sometimes called glycogen. This has been particularly studied by Kouget, who detected it in cartilage at an early period of develojiment, and also in fibrous and muscular tissues. The epidermic tex- tures exhibit a considerable proportion, although not a trace can be detected in the same textm'es in their fully developed state. The same is true of the dehcate textm-e which is at length to become ham, horn, or nail. Dr. McDonnell has shown that this amyloid matter exists in the lung tissue in very large proportion, increasing, as development advances, to nearly twenty per cent., while shortly before bmth the quantity is so small that it can scarcely be estimated. It is found in muscular tissue generally, but not in that of the heart, in which, probably from its reachmg a state of functional activity long before the muscles of the system generally, the proportion of amyloid is comparatively small. In the liver, the formation of amyloid slowly increases, and after bmth, its formation seems almost 112 GELATIN- YIELDING SUBSTANCE. restricted to this organ. Throughout life, large quantities of amyloid continue to he produced in the liver, and in certain morbid conditions it accumulates enormously. This production of amyloid is probably associated 'with rapid change in the germinal matter. If this substance were formed by the ger- minal matter of the tissues in the adult state, it would exist in such small quantity in proportion to the other matters pro- duced, that we might not be able to detect it by the processes at present at our disposal. With reference to the part played by the amyloid matter in the tissues in early life, it would seem probable, from the researches of Dr. McDonnell, that it appro- priates to itself nitrogen, and that in this manner a material is produced Avhich afterwards takes part in tissue fonnation. The same observer has advanced many arguments in favom' of the view, that the amyloid matter, as it slowly escapes from the liver cells in which it was formed, takes to itself nitrogen derived from the retrogressive metamoipthosis of fibrin in the blood, and that thus a protein substance, aided to casein and globuline and the matter of which the white blood corpuscles are composed, results. — (^Proceed. Royal Soc. 1863, vol. xii, p. 478.) The production of these substances allied to starch and sugar, seems to be associated with lunited oxidation. It is probable that the chemical elements which, in the embiyo, combme to fo]’m starchy matters, would, at a later period of development, combine with oxygen to form carbonic acid and other substances, which would be excreted m a soluble fonn. This view is confirmed by the fact that, in the fiver, in which amyloid matters are beiag formed throughout fife, oxidation is very limited ; wliile those morbid conditions in which the for- mation of the same substance occm’s in connection with many adult tissues, especially the smaller arteries and the nervous tissues, are characterized by a reduction in the activity of this process. Amyloid matter (glycogen) has been detected in the substance of the round worm of the pig (ascaris lumbricoides), by Dr. Michael Forster {Proceed. Royal Society, vol. xiv, p. 543, 1865), and it has been found in many of the lower animals, which five under conditions incompatible with a highly active state of the oxidizing processes. Gelatin-yielding Substance . — The tissues have assumed their permanent anatomical characters, and have commenced to per- OF GELATIN. 113 form their normal functions, when the substance which yields gelatin by boiling is produced. At an early period of develop- ment, although delicate transparent tissue may be detected, it does not yield gelathi. According to Hoppe, this substance cannot be detected rmtil after the embryo has left the egg. The proportion of the fibrous textiwe, and gelatin-yielding tissues allied to it, increases as age advances. Gelatin does not exist preformed in the tissues, and can only be obtained by artificial means. If the cutis or true skin, tendon, or bone, be subjected to continued boiling, this substance is obtained in solution in the hot water, and, upon cooling, assmnes the form of a solid jelly, which is the more solid as the quantity of water contained in it is less. The textiu’es which yield gelatin are, the white fibrous tissue, areolar tissue, skin, serous mem- branes, and bone ; glue, prepared from hides, &c., size fi-om parchment, skui, &c., and isinglass fi'om the swimming bladder of the stru’geon, are various forms of gelatin used in commerce. Gelatin, obtained by boiling, is in combination with a con- siderable quantity of water ; by a slow and gentle heat this may be driven off, and the gelatin obtained in a dry state. Dry gelatin is hard, transparent, colourless, without smell or taste ; of neutral reaction ; in cold water, it softens and swells up, and dissolves in warm water. It is insoluble in alcohol and ethei', but very soluble in the dilute acids and alkalies. When tannin, or the tinctru'e or infusion of galls, is added to its solution in water, a brownish precipitate is thrown down — -the tanno- gelatin, which may be precipitated from a solution of gelatin m 5,000 times its weight of water. Gelatin contauis in 100 parts C50-4 H7-1 N18T 0 23‘8 S 0‘6. The process of tanning leather, depends upon the affinity of gelatin for tannin. The skins of the animals, having been first freed from cuticle and hairs by soaking in lime-water, are tanned by submitting them to the action of infusion of oak-bark, the strength of which is gradually increased, until a complete com- bination has taken place. An msoluble compound is thus formed, capable of resisting putrefaction. If a solution of gelatin, in concentrated sulphuric acid, be diluted with water and boiled for some time, glycocoll may be obtained from it on saturating with chalk. Again, by boiling gelatin in a concentrated solution of caustic alkali, it is sepa- I 114 OF CHONDRIN. rated into leucine, CgHjgNOj, and glycin or glycocoll, C 2 HgX 02 . The latter product crystallises in pretty large rhomboidal prisms, is colomless and inodorous. Chondrin is a substance in many respects similar to gelatin. It is obtained in a state of solution, by boiling water, from the permanent cartilages and from the cornea ; also from the tem- porary cartilages prior to ossification ; it gelatinizes on cooling and when diy assumes the appearance of glue. It differs from gelatine, in not being precipitated by tannin, and in yielding precipitates to acetic acid, alum, acetate of lead, and the proto- sulphate of iron, which do not disturb a solution of gelatin. Chondi’in contains in 100 parts G49'9 H 6'6 N 14'5 0 28'6 S 0'4. Like fibrin and albumen, it contains a minute quantity of sulphur. The interesting researches of Dr. Roudneff, of St. Petersburg (Ai-chives of Medicine, vol. iv, p. 304), seem to show that chon- ifrin undergoes conversion into gelatin by oxidation. Prior to the formation of vessels in the temporaiy cartilage of the embryo, that substance yields chondrin, while, after this, gelatin is obtained from it. Chondi’in, obtained fi-om permanent car- tilages, was subjected to the action of oxidizing agents, and the resrdting mass it is stated gave the reactions of gelatin. The chemistry of early life differs fi-om that of the embryonic state enormously in the greater activity of the process of oxida- tion. The functions of Respiration and Ch'culation are more actively performed, and the quantity of matenal dishitegrated is considerably increased. Dm-ing the early periods of develop- ment there is comparatively sHght demand for oxygen. The amount of germinal matter produced is very great, and tissue is being formetl and accumulates, but there is no active discharge of frmction, and the amount of formed material oxicbzed and destroyed, is very small. Little icorh is performed at this period of life, for work results from the disintegration of mateiials which have been already formed. It is interesting to note how intimately an active condition of the oxidising process is con- nected with a healthy state and a frdl working condition of the various organs of the body, and how many morbid condi- tions of tissues and organs, which necessarily terminate in death, are due essentially to diminished oxidation. OF THE BLOOD. 115 OP THE BLOOD. As the tissues and organs advance towards maturity, the hlood becomes of vast unportance, and it is not possible to discuss even cursorily the general chemical changes in the oi’ganism without referring to the composition of the blood and the phenomena which are takmg place m it dmmg every moment of existence. Although the chemical components of the blood and the hlood corpuscles are more particularly con- sidered under circulation, it will he necessary to refer briefly to them in this place. Of the fluids of the body, the hlood alone yields the various mateiials required for the formation of the tissues and organs, and for maintaining them in a state of integrity after then- for- mation is complete ; and, through its agency, all the substances resulting fi'om the disintegration of textm-es which have already performed their work are carried to the different parts of the body at which their removal is effected. The blood must there- fore be considered as the medium, by wliich, at the same time, nutrient matters are carried to every tissue of the body, and products resulting from decay brought to the points at which they can be discharged. The consideration of the chemical changes taking place in the blood will comprise some of the most important chemical phenomena occmring in man and the higher animals dming all, except the very earliest periods of existence. The fluid which is concerned in distributing nutrient matter to the tissues of the lower animals, like the blood of man and the higher animals at an early period of development, is perfectly transparent and colourless. It contains some sphe- rical colomiess granular masses of germinal matter, which, when at rest, exhibit vital movements. These are the most important and the only consttrnt corpuscles of the blood. The fluid, or liquor sanguinis, m which these are suspended, besides water, salts, and fatty matters, contains two very important substances. Of these, one, i\\e fibrin, coagulates spontaneously when the fluid is removed from the living organism and brought into contact with any foreign matter. The other, albumen, is dissolved in the water, but on the application of heat, or upon tlie addition of a mineral acid, it passes into an insoluble condi- tion, forming a wliite clot or coagulmn. It is also precipitated I 2 116 WHITE BLOOD CORPUSCLES. by solution of tannin and by many metallic salts. ^^Tiite or colourless blood corpuscles, fibrin and albumen, which are in- cluded in the class of proximate principles (see p. 8), and water, are important constituents of the blood at eveiy period of its existence. The white hlood corpuscles, or masses of living germinal matter of the blood, are the direct descendants of the germinal matter of the cells which took part in the first development of vessels. The white blood corpuscle m fact coiTesponds to the germinal matter in the interior of a ‘ cell.’ There can be httle doubt that, at least in those instances m which the nutrient fluid contains no red corpuscles, these colom’less corpuscles are the agents concerned in the production of the albumen and fibrin, and there is every reason to beheve that the red blood corpuscles, specially characteristic of the blood of vertebrate animals, are formed from these bodies. It has been ah’eady stated that all forms of living germinal matter yield a spontaneously coagulable substance closely alHed to the fibrin of the blood, though perhaps not identical vdth it, and a soluble albuminous material which is precipitated by heat and nitric acid. It is probable that the pabulum required for the nutrition of the higher tissues is prepared and formed tlirough the agency of germinal matter of less special endowments, such as that found in connection with the capillary vessels ; and that the fi’ee germinal matter in the blood, representing that in the interior of the fully formed cell, itself in its turn gi'ows at the expense of materials formed from other kinds of germmal matter, especially that in connection with the intestinal mucous membrane. A lbumen is so called fi'om the white colour it possesses in its solid coagulated state ; ‘white’ of egg is largely composed of it. Besides formmg more than 30 per cent, of the sohd matter of the blood, albumen, more or less modified, enters into the com- position of many of the tissues of the body. It exists in two states ; fluid — being dissolved in the serum of the blood, and in some of the secretions ; and solid — forming a large propor- tion of certain of the tissues ; for example, of the dry cere- bral substance, which are for this reason called albuminous tissues. These are, the brain, spinal cord and nerves. It also enters into the composition of the muscles, and traces ALBUMEN. 117 are found in tlie aqueous and vitreous humours of the eye. It is present in the various kinds of serum and in pus, poured out under various cu’cumstances, and formed in the course of disease. Albumen contains in 100 parts C 53’5 H 7’0 N 15 5 0 22'4 S 1’6. It exhibits no tendency to assume spontaneously the solid form, except by the loss of the water which is com- bined Tvith it. By evaporating white of eggs, at a temperature not exceeding 1 20°, its water is driven off, and solid albumen, in the form of a yellowish transparent brittle mass, is obtained, with all its properties unimpaired. If a solution of albumen, m water, be exposed to a heat between 140" and 150°, it coagulates, and then becomes insoluble in water. Albuminous solutions are albaline, and it is probable that at least a portion of the alkali is chemically combmed. The mineral acids have the property of coagulating albumen. Of these, the nitric is most used in medical practice. A few di’ops of this acid will enable us to detect a small quantity of albumen dissolved in a clear fluid, by rendering it more or less opaque. Alcohol also has this property ; and hence any albu- minous textures submitted to its influence, become hardened and condensed. Bichloride of mercury exercises a similar in- fluence, and is a delicate test for albumen. It was Orfila who first employed this proximate principle as an antidote to the poisonous effects of the bichloride, which combines with the albumen, forming with it an innocuous compound. Accord- ing to Peschier, the white of one egg is sufficient to render four grains of the poison harmless. Another delicate test for albu- men is the ferrocyanide of potassium, wliich will precipitate it fi’om solution, provided a little acetic acid have been previously added, in order to neutralize the soda in combination with it. Albumen is also precipitated from solution by tannui. It coagu- lates at the negative pole of the galvanic battery, or at both poles, when a strong battery is employed. Many other re- agents will coagulate this principle, but enough have been men- tioned for all practical purposes. Albumen is soluble in caustic alkalies. By prolonged boiling in hydi’ochloric acid albumen is resolved into a substance allied to chondrin. The existence of sulphur as a constituent of albumen, is shown by the blackening of silver that has remained long in contact with it, or by boiling a little albumen in a solution of oxide of lead in potash. 118 PARALBUMEX AND :\IETALBUMEX. In disease it often happens that albnmen is earned off from the system in large quantities in the uiane. By any of the means above mentioned, its presence in that fluid may be detected. When heat is used it vdll always be advisable to ascertain previously whether the urine be acid or alkaline ; for the presence of alkali prevents the coagulation of albumen by heat. Hence it is a good rule in testing for this substance to employ both heat and nitric acid. If, however, only one or two drops of nitric acid be added the albumen vdll be pre- cipitated and then quickly re-dissolved by agitation. This acidulated solution, it must be remembered, is not coagulated by heat. The practitioner should, therefore, be careful never to test albuminous urine in a du-ty test tube, which may contain a little nitric acid.* Gigon states that there exists even in healthy urhie a substance alhed to albumen, and according to Dr. George Harley, the albmninous matter resembles that form of albumen which has been dissolved by gastric juice ; for, like this, it is not coagulable by heat or nitiac acid. Parallmmen and Metalhumen are modifications of albumen dis- covered by Scherer hi the fluid of ovarian dropsy and in an albuminous fluid removed by paracentesis. The first is very slightly coagulated by boiling. Alcohol precipitates flocculi, which are re-dissolved by water. The latter is coagulated neither by hydrochloric acid nor by ferrocyanide of potassium. Pancreatin from the pancreatic fluid is closely allied to albumen. In mammalia it is certain that many different cells can pro- duce a substance Avhich possesses all the chemical characters of albumen. From the cells of cuticle and many other structm-es a solution can be obtained which contains albumen. The cells of the follicles of the lacteal glands give rise to it, and those which occupy the GraafSan follicles also produce it, and in ovarian dropsy, when these follicles are enormously enlarged, there can be no doubt that the albumen is actually formed in the interior of the cyst, for, as above stated, it differs from the albumen of ordinary serum. ]\Ioreover, albumen is found in almost all animals, and m certain of the fluids of plants. The facts above enumerated render it probable that the * For the methods of testing albuminous urine, see “Erine, Erniarv Deposits and Calculi.” FIBRiy. 119 albumen of the blood results from changes occurring in the blood corpuscles. In many cases albumen results directly from changes in germinal matter, but it seems probable that in man and the higher animals, part, at any rate, of the albumen of the blood is formed from the red corpuscles which are them- selves formed material resulting from changes occm-ring in the white blood corpuscles. Albumen is one of the substances which forms the pabulum of cells, and there can be no doubt that from it many very different materials may be produced by the agency of the living or germinal matter of the various textcnes. Fibrin exists, in a state of solution, in the blood, formuig, with the serum of that fluid, the liquor sanguinis of Dr. Babing- ton, hi the lymph and in the chyle. It is a constituent of the exudation (coagulable lymph) which forms on certain surfaces, as the result of the inflammatory process, and it sometimes occurs in dropsical fluids. Fibrin is distinguished from the other substances allied to it by its remarkable property of spontaneous coagulation. When blood or fluid containing much flbrin is drawn from a vessel and allowed to rest, it speedily separates into a solid portion, the crassamentmn or clot, and a fluid portion, the serum. The clot of blood consists of flbrin, with the ^chite and red blood corpuscles entangled in it durhig its coagulation. It sometimes happens that owing to an unusual aggregation of the red parti- cles together, and to then more speedy subsidence, a portion of fibrin on the surface coagulates without enclosing the colouring matter. A yellowish white layer forms the upper stratum of the crassamentum, and this is called the huffy coat or in- flammatory crust. It is an example of nearly colourless fibrin, but like other forms of this substance, contains also the white corpuscles. We may obtain fibrin in a state of considerable purity, by cutting the crassamentum into slices, and washing them in clean water so as to dissolve out the colouring matter ; or by briskly sth’ruig with a bundle of twigs, blood as it flows from a vessel : the fibrin coagulates upon the twigs in small portions, which being washed, aflbrd good specimens of colourless fibrin ; by digesting afterwards, in alcohol and ether, the fatty matters are got rid of. Another mode of obtaining this substance in a 120 FIBRIN. state of purity is that suggested by Job. Miiller. Tliis consists in adding to frog’s blood a little syrup (one part of sugar to two hundred parts of water) which retards the process of coagulation for a sufficient time to enable us to filter it. The frog’s red particles being too large to permeate the pores of the filter, the liquor sanguinis passes thi-ough hi a coloiu’less state, and its fibiin coagulates free from colouring matter. iSometimes we obtain masses of fibrin, great part of which is colourless, from the cavities of the heart, and fi-om the large arteries after death. It is also accumulated and disposed in a peculiar lamellar form, in the sacs of old anemasms. Pure fibrin is white, tasteless and inodorous ; it tears into thin laminm. Under the microscope it is seen to consist of o, fibres crossing one another at every possible angle and inter- lacing in all directions ; and h, very numerous white blood corpuscles. It is not yet possible to obtain the fibrinous material in a perfectly pm'e state and free from the coiqiuscles. It contracts for some time after its fii’st precipitation, and retains remarkable elasticity, even after it has been for years immersed in preservative flmds. If fibrin be dried it becomes yellow, hard, and brittle, and loses three-foui’ths of its weight, but imbibes water again when moistened; it is insoluble in both hot and cold water, in alcohol, and in ether. By long- continued boiling in water its composition is changed, and it becomes resolved into a soluble and an insoluble substance, the first of which has been termed the teroxide and the second the binoxide of protein. Strong acetic acid converts it into a jelly-like mass which is sparingly soluble in water. A solution of nitrate of potash ui the proportion of 1 part to 5 of water, readily dissolves fibrin. It is also to some extent soluble in solutions of some other alkaline salts. All the alkalies dissolve fibi'in. Any of these solvents of fibrin vfill prevent the coagula- tion of blood which has been allowed to drop into it as it flows from the blood-vessels. Fibrin is dissolved by cold concen- trated hydrochloric acid, and if kept at a cool temperature for twenty-four hours, the solution acquires an indigo blue colour. Albumen similarly treated assumes a violet colom-. Caustic potash, common salt, carbonate of potash and many neutral salts, Avhen mixed in certain quantities with the blood, have the property of retarding or preventing the coagulation of its FIBRINO-PLASTIC SUBSTANCE. 121 fibrin. There still exists much difference of opinion con- cerning the mode of formation, origin, and. uses of this sub- stance. Dr. Richardson supposed that the fibrin was held, in solution by the ammonia present in living blood, but although there is no doubt that this substance will prevent the coagulation of blood, there are many facts opposed, to Dr. Richardson’s view, and. some observers have not succeeded, in detecting even traces of free ammonia in fluids in which fibrin existed in its uncoagulated state. It has been inferred by Mr. Lister that the chemical com- bination of globulin and fibrinogen, and the formation of fibrin was due to some mysterious and unexplained action of extra- neous matters and ordinary solids, upon the previously soluble materials. Others consider that the blood possesses a “ natural tendency ” to coagulate, but that as long as it remains within the body, if the vessels be in a healthy state, coagulation is pre- vented. Neither of these views are entitled to be considered explanations of the process of coagulation. Professor Andrew Buchanan, of Glasgow, observed long ago that the flrdd of hydrocele yielded a coagulum, if blood serum, probably containing a few blood corpuscles, were allowed to fall into it, although it might be kept for any length of time with- out coagulation, if no blood serum were added. A. Schmidt, of Dorpat, apparantly ignorant of Buchanan’s observations made twenty years before, has recently shown that for the formation of fibrin, a fibrino-plastic substance of the nature of globulin, must combine with another substance, which he terms fibrinogen. Either may be present without the occurrence of coagulation, but if the smallest proportion of the fibrino-plastic compound be added to fibrinogen, coagulation occurs. The fibrino plastic substance is globulin, and may be obtained from various sources, as saliva, synovia, the fluids of the eye, connective tissue, probably also from muscle, nerve, &c. Tliis view con- cerning the formation of fibrin has been accepted by Mr. Lister. According to some, the formation of fibrin is a purely chemical process, and results fi’om the direct oxidation of the albumen. Von Gorup-Besanez has shown that ozonized an* causes the formation of fibrin-like coagula in an albuminous solution, and that these coagula might be re-dissolved in the 122 COAGULATION OF THE fluid. The researches of Mr. A. H. Smee (^Proceed. Royal Society, 1863, vol. xii. p. 399), have proved that if oxygen he passed through a solution of albumen, for thu’ty-six hours, at a tempera- tme varying between 95 and 100° Fah., the solution becomes of firmer consistence, and when examined microscopically, numerous lines indicative of fibres are seen. Mr. Smee infers that the substance thus produced is fibrin, and that it has been formed dh’ectly from the albumen by oxidation. He states that it cannot be distinguished fi'om trae fibrin by the microscope. But although the new material agrees in many of its characters with what we call fibrin, it is doubtful if it is identical vdth it. One very remarkable character of fibrin is to contract gradually after its formation, but Mr. Smee has not stated if his fibrin exhibits this property. While the fibrin-like material was being produced, carbonic acid was evolved and phosphoric acid was formed. By the oxidation of gluten, from wheat from', Mr. Smee also obtained a substance wdiich he could not distinguish from orchnary fibrin. He was unable to obtain fibrin by pass- ing oxygen thi'ough urine which contained a large quantity of albumen. The fact that the quantity of fibrin in blood is increased by oxidation, may be explained, as well by supposmg that the oxygen acts upon the matter of the white blood coipuscles, as by inferring that albumen is oxidized; while its absence hi certain cases of asphyxia, in hunted animals, and in sudden death by lightning, would be accounted for by the too sudden death of the white corpuscles ensuing hi these cases, although it could hardly be attributed solely to deficient oxidation. We may now consider what may be actually observed under the microscope when fibrin passes from the fliud to the solid state. Observations with the aid of the very high powers and Ao) Tecently brought into use, have taught us many new and highly important facts which could not have been amved at without then aid. If the phenomena of coag-ulation be carefully watched as it occins under a power magnifying upwards of 2,000 diameters, the following points wiU be olDserved hi favom-able cases soon after the blood has been covered with the thin glass or mica. The fii'st change noticed is, that a film-like appearance is developed in the hquor san- guinis, and this is especially observable in the wake of those FIBRIN OF BLOOD. 123 red corpuscles, wliich are being slowly moved across tbe field by the currents in tbe fluid produced by the unequal pressure of the thin glass cover. The appearance may be compared to that seen in the fluid circulating in the cell of vallisneria, except that in this latter innumerable and excessively minute spherical, colourless particles can be discerned ; while although many very transparent and scarcely visible corpuscles may be seen in the blood, the fluid does not appear to be almost entirely composed of minute spherical particles, moving about one another as in vallisneria. This film-like appearance is gradually succeeded by the formation of delicate threads, which are seen to cross one another at various angles, and apparently correspond to the lines which the blood corpuscles have traversed as they have moved about the field (plate V, fig. 44). The lines seem to acquire greater density and increase in refractive power for some time after they were first visible. I have never been able to demonstrate that the lines are formed by the actual coalescence and running together of minute particles. It seems to me more probable tliat the coagrdable matter exists in the first instance as a highly diffused plasma, probably formed by the white blood corpuscles, and the smaller colomdess corpuscles allied to them, which gradually separates fi-om the serum with which it was originally united, and contracts until it acquhes sufficient density and refractive power to be seen by us. During the process of coagulation many of the red corpuscles are seen to become stellate, and these refract more highly, are more dense and are of much less diameter than those which retain their smooth surface, and even, circular, outline. In this change, fluid, curtaining globulin (?), probably escapes. That fibrin may be formed directlii from the white blood corpus- cles seems to be proved by the fact that if a white blood corpuscle, which has become attached to a little elevation or depression upon the smTace of the glass, be caused to move in one dh-ection away from its point of attachment, it will develop a narrow thread, which gradually increases in length and appears to be di’awn out from the corpuscle. It becomes firmer, and more highly refracting. This tln-ead exhibits all the characters of fibrin, and is probably composed of this substance (fig. 45). In many cases the white blood corpuscles throw out exceedingly 124 COAGULATION OF FIBRIN. thin, thread-like processes, which gradually assume the appear- ance of filaments of fibrin.* White corpuscles, which, when first removed from the body, appear perfectly smooth and transparent, gradually become more or less granular, plate V, fig. 44, above a ; and the granules increase in number and size for some time, until the movements exhibited by the perfectly transparent germinal matter cease, and the white corpuscle dies, and forms a coagulum. The fibrin in the blood of some rodents appears perfectly gTanular imme- diately after coagulation has occm’red, and there is no indica- tion of distinct fibres, plate V, fig. 48. All recently formed fibrin is found to contain an immense number of the white blood corpuscles, as may be readily demonstrated in the beautifully transparent coloiu’less coagula not unfrequently found in the cavities of the heart, plate V, fig. 47. The substance, therefore, which we know as fibrhi, undoubtedly consists of the highly refracting, insoluble, and eminently elastic threads (fibrin) ; and the insoluble transpa- rent matter resvdting from changes in the living and eminently mobile material of tlie white blood corpuscle. It seems probable that the tlu’eads are originally formed from a substance produced by the wliite blocd corpuscle. The above observations are not opposed to the view of Buchanan and A. Schimdt, — for the fibiinogen, the material which is requu-ed in very large proportion, may be furnished by the white blood corpuscles and the minute corpuscles of the same nature ; while from the red blood corpuscles the fibrino-plastic substance, of which a mere trace seems to be necessary, may escape. The spontaneously coagulable matter may, however, in certain cases, remain difiused for months after it has been formed, vfithout coagidation taking place, and then an altera- tion hi the external conditions, exposure to air, &c., may cause it to assume the solid form. With reference to the uses of hhi-in there can be no doubt that it performs an unportant service in limiting hsemoirhage when vessels are divided, and that it forms, when effused ui internal parts, or on the surface of wounds, a temporary tissue, * “ On the germinal matter of the blood, with remarks upon the formation of fibrin.” — Trans. Mic. Soc., December, 1863. COAGULATION OF FIBRINE, Fig. 44. PLATE V a I rc.YHE ' Red and white corpuscles in blood from the fin$er. x 2300 linear The large smooth circulirVhj^diep, red corpuscles. Three very smallredcorpuscles areless than the of an inch in diameter T^e ism^ieis,t, j ^ particles ai'e composed of matter like that of which the white blood corpuscle (B) con^iSt^ Treads of fibrine undergoing coagulation are observed between the corpuscles in the upper and low^’pa-j^h^JJi.R^^ NT’ A, red corpuscle, exhibiting angular projections. Below it. and to the left, is another, with 's^Jnore pointed ' processes. September. 1863. . .tA'.Kv Fig. 47^C'' ., . " t iw Fig. 46. White blood corpuscle (human subject) , with thread of fibrine connected with it. x 1800. From a pale clot in the heart of a patient who died of exhaus- tion. showing white corpuscles and fibres of fibrine x 700. Fig. 43. Portion of a large mass of fibrine fi-om Guinea pig's blood the instant coagulation had occur- red. X 1800. Capillary vessel firom the mucous mem- brane ofthe epiglottis from a man aged 74. X 700, of an Inch X 700. X 1800. X 2,800. 3. B.] [To face p. 124. RED BLOOD CORPUSCLES. 125 a cementing or protecting substance, or bond of union, between separated parts, wbicb serves as a nidus for the development of the masses of germinal matter which are to take part in the formation of a higher, more elaborate, and more slowly formed, but much more durable textm'e. It has been suggested that fibrin is required for the nutrition of a special class of textures, as the gelatin-yielding tissues, but we find fibrui in cases in which there are no such textures ; and where these tissues do exist, they require such a small amoiuit of nutrient matter, and undergo such slight change, that we should scarcely expect to find the proportion of fibrin, which exists when the formation of these tissues is complete, as great as it is. Nor is it probable that such highly important elements of the blood, as the white blood corpuscles, should take part ui the nutrition of any one special tissue ; and if upon other grounds than those advanced we were disposed to accept such a view, we should hardly be inclined to assign to such highly important and pecuhar bodies the office of nourishing the lowest and simplest tissue in the body. Upon the whole, the facts known render it more hkely, as has been before advanced, that the various masses of ger- minal matter of the several textures, form, from the same nutrient materials compounds different in structure, property, and composition ; than that substances allied to the tissue to be formed, are simply selected, separated, and deposited from the nutrient plasma. There is indeed no evidence of the exist- ence of many different substances in the blood of man and the higher animals, in which the mnnber of different textm-es and secretions is very great. jRed Blood Corpuscles . — The blood of vertebrate animals con- tains numerous colom-ed corpuscles, which are known as the red blood corpuscles, and these contribute to the blood its most important characteristics. The red colour of blood is entirely due to these bodies, and the difference in colour between arterial and venous blood is caused by alterations occurring in the material of wliich the red corpuscle is composed. These corpuscles are probably derived from the white ones, so that the younger red blood corpuscles contain germinal matter, a fact proved by the circumstance, that in some instances, under high magnifying powers, this germinal matter has been seen to 126 lUEMATO-CRYSTALLIN. move away from the coloured material akeady produced.* A the corpuscle advances m age, the whole of the germinal matter becomes converted into the coloured lifeless formed material which very readily assumes the crystalline form. The red cor- puscle, in fact, seems to be composed of a small portion of soft matter, of a viscous consistence, very slightly soluble in fluid, but capable of undergoing solution in the seiuim xmder certain circumstances. In some animals the red matter retains its colloid semi-fluid state only while it is kept hi active motion in the circulation. The red blood corpuscles of the Guinea-pig pass into a crystalline state Avithin half-an-hoiu’ after they have been removed from the vessels, and vdthout the addition of any reagent or solution Avhatever. It is certain, at least in this case, that there is no rupture of membrane and escape of con- tents. The small mass of viscid matter of which each single corpuscle is composed may be seen to form a smgle crystal, while if the corpuscles be slightly Avarmed, they break up into many small portions, each one of Avhich assumes the tetra- hech-al form.* (See plate VI, fig. 49 ; plate VII, figs, 58 to 61.) It appears probable that the colom-ed material of AA’hich the fnlly-formed red blood corpuscle is composed is a hfeless chemical substance, which, under the conditions to AAdiich it is exposed during the cu’culation, becomes resolved into certain compounds which are of great importance in nutrition, and others, Avhich being readily soluble in fluid, with a high power of diffusion, or in a gaseous state, are readily remoA^ed from the organism altogether. It Avas formerly considered that the matter which enters into the formation of the red blood-corpuscle consisted of two siibstances, hsematin and globulin, biit later researches rather tend to the conclusion, that in the natural condition there is one chemical substance which, hoAA^ever, is readily decomposed. This has been termed Globulin, Ilcemato-globuUn, Hannato-crys- tallin, and Hmno-globulin. It is the ciystallisable material above referred to. V arious forms of hmmato-crystalhn, fr-om the Guinea- pig, human subject, cat, and mouse, are represented in plate VII. A solution of this substance, as well as of certain products of its decomposition, produces pecuhar absorption-bands in the * Observations on the Bed Blood Corpuscle. Trans. Mic. Society, Dec. 1S63. BLOOD CRYSTALS. PLATE VI. Fig. 49. Fig. 50. Human blcod crystals. X 215 Fig. 51. Crystals of bsematoidin from human liver, x 215. Fig. 52. Blood crystals. Human, x 215. Fig. 54. Blood ciysteQs. House Fig. 53. Pig. 55. a^MIfJ CRYSTALS. Human. X 215. Pig. X 215. o'’ I, V '51 ^ r Toad. X 215. V X Goldfinch. X 215. Fig. 56. Fig. 57. Rhomhoidal and feathery crystals of haematin, from a softened clot. Human X 215. ^ X 215. L. S. B.] [To face p. 126. H^MATIN. H^MATOIDIN. 127 solar spectrum. Hoppe was tlie first to demonstrate this inte- resting fact, and found that a very dilute solution of blood was sufficient for the purpose. The same bands were produced by the blood of different animals. Stokes proved that this colour- ing matter was capable of existing in two states of oxidation, and that a very different spectrum was produced according as the substance which he termed cruorine was in its more or less oxidised condition.* Protosulphate of iron,t or protochlo- ride of tin, causes the reduction of the colom’ing matter, and by exposure to air oxygen is reabsorbed, and the solution again exhibits the spectrum characteristic of the more oxidised state. In venous blood there is reason to believe that part of the cruorine exists in its purple or less oxidised condition, and that tliis, in passing through the lungs, is reoxidised and converted into the scarlet cruorine, plate VII, figs. 62 to 65. The different substances obtained fi-oin tlie normal blood colouring matter produce different bands. Thus, Hcematin gives rise to a band in the red of the spectrum between the lines C and D. Haimato-glohulin produces two bands, the second twice the breadth of the first m the yellow portion of the spec- trum between the lines D and E. The absorption bands differ accordmg to the strength of the solution employed, and the medium in which the blood salt is dissolved ; i but an exceed- ingly minute proportion dissolved in water is sufficient to biing out very distract bands, and in Iris new spectroscope Mr. Sorby is able to obtain the band from a single blood corpuscle. § The most important chemical compounds obtained from the red blood corpuscles are the following : — Hoematin, Hoematoidin, and Hcernin. Hcematin may be obtained from hoBmato-globuUn. It occm’S in old extravasations of blood, and may be detected hr the fteces. * “ On tlie reduction and oxidation of the coloui-ing matter of the blood,” by G-. G. Stokes. — Proceed. R. S., 1864, vol. xiii, p. 355. t The solution is made as follows. To a solution of protosulphate of iron, enough tartaric acid is added to prevent precipitation by alkalies. A small quantity of this solution made slightly alkaline by ammonia, or carbonate of soda, is to be added to the weak solution of blood in water. J On this subject the most recent observations wOl be found in F. Iloppe- Seyler’s Handbook of Physiological and Pathological Chemistry. Hirchwald. Berlin, 1865. This work is a very valuable one. § “ On the construction and use of the Spectrum Microscope,” by H. C. Sorby, F.E.S. — Pop. Science Review, January, 1866. 128 EXTRACTIVE AND SALINE JLVTTERS. It is not crystalline, and when dry it forms a brown powder, which contains nearly 9 per cent, of iron. A thin layer of a solution of hmmatin exhibits a gi’eenish colour, while a thick one is dark red. Hoppe-Seyler names another substance allied to IlcBmatin, Methdmo-globulin. This may be a mixture of haematiu and some albuminous substance. Ilmnatoidin is a modified form of haematin. It is not easily decomposed, is insoluble in water, alcohol, ether, and acetic acid, but readily soluble in alkalies. This is the substance which is found in old clots and extravasations, and not unfire- quently in the walls of some of the smaller vessels, perhaps marking the situation of old hsemoiThages. It crystallises in very beautifully defined rhombic crystals, plate YI, fig. 51. It also forms long filaments, and not unfrequently shghtly curved elongated crystals collected into bimdles, which sometimes take the form of oval or dumb-bell shaped masses, plate VI, figs. 56, 57. This substance seems closely alHed to a yellow ciystaUine material obtained from the bile. It woidd indeed be very diffi- cult to distinguish hsematoidin crystals found in clots from some crystals which have been produced in biliarj^ matters. Hsematoidiii may therefore be the same substance as that obtained from bile mider the names CholepyiTliin Biliphsein, Bilifulvin, and more recently Bilhubin. Zenker and F unke have shown that from the yellow crystals of bilifulvin red ciystals of h^matoidin may be obtamed. llcemin is a substance which was discovered by Teichmann. It is obtained artificially ft’orn haematin and hsemato-crystaUin. By the addition of a little glacial acetic acid to a small portion of clot of blood, the haemin is produced and crystallises in rhombic scales. Haemin crystals may be thus obtained from the red blood of man and the lower animals. Blood that has been kept for some time pelds these ciystals as well as fr-esh blood, and, with care, they may be obtained fr-om the smallest blood spot on clothes, &c., hence this reaction is of value in medico- legal mquiries, but, as a test, it is less dehcate than the spec- trum analysis already referred to. Haemin crystals fr-om the human subject, pig, toad, and goldfinch are represented hi fig 55. Extractive Matters . — It is probable that the so-called extrac- tive matter of blood consists of substances which result diuing PLATE VII. BLOOD CRYSTALS. CRUORINE. CAPILLARIES. Fig. 53. Blood crystals from the blood of the Guinea pig. X 700. B D E 6 F Fig. 59. Fig. 60. Disintegration of red blood corpuscles of Guinea pig's blood, and formation of crystals. After application of a gentle heat, x 700. Fig. 61. Absorption bands. Arterial and scarlet cruorine. Absorption bands. Venous blood and purple cruonne. Absorption bands. Blood treated with acetic acid. Formation of blood crystals from the red blood corpuscles of Guinea pig’s blood, shortly after removal from the body. No reagent added or heat applied. X 18C0. Fig. 65. II Absorption bands. Solution of heematin. Copied from ' Stokes, Proc. R. S., 1864. Fig. 67. Fig. 66. Capillary showing masses of germinal matter projecting into its interior. Areolai’ tissue Mouse, x 700. Fig. 68. Capillary, connective tissue. Cattle plague. The masses of germinal matter of the capillaty are very much enlarged, and are dividing and subdividing to form new masses. X 700. lo'o'o Inch X 700. Chloride of sodium Fig. 69. Margarine crystallised spontaneously After Kobin and Verdeil. L. 3. B.] [To face p. 128. EXTKACTIVE AND SALINE MATTERS. 129 the decay and disintegration of the blood corpuscles, and their resolution into various definite compounds. These indefinite extractive matters probably pass off in an altered form in the urine and other secretions almost as fast as they are produced, for the quantity of extractive matter in normal blood is very small, scarcely amounting- to more than '5 or -6 per cent., but in certain morbid conditions a much larger proportion is found. Of the saline constituents of the blood taking part dh-ectly in the nutrition of tissues, or subservient thereto, probably the chlo- rides and alkaline and earthy phosphates are the most important. The chlorides increase the fluidity of an albuminous fluid, and probably facilitate the access of the nutrient pabulum to the germinal matter of the cell. In all cases in which cell-develop- ment is going on actively a large quantity of common salt is present. During the development of the normal tissues in the embryo, and dm-ing the multiplication of the masses of germinal matter in disease, as in pneumonia, the formation of abscess, in cancer, and other morbid states, characterised by rapid cell growth, chloride of sodium is to be detected in considerable proportion. It is doubtful if the alkalme phosphates are devoted to nutrition, although there can be no doubt they are of service in givhig to the serum an alkaline reaction, and are, perhaps, to some extent, concerned in the absorption of car- bonic acid and other changes. The greater part of the phos- phate in the blood is probably derived from the bread and meat taken in the food. The earthy phosphate of lime winch forms 3'5 per cent, of the ash of blood is an important substance. Iron should also be enumerated among the salme constituents of the blood, of service in the nutritive process, but we are not yet acquamted with the exact part it plays in the chemistry of the body. The foregoing are probably the constituents of the blood which take part m the nutrition of the various tex- trrres, and from them the chemical comporrnds found in the tissues and entering into the compositiorr of the various secre- tions, are alone formed. There are many other substances in the blood, which probably result fr-om tire action of oxygen upon certain of the constituents of that flrrid or of the tissues, arrd are porued into the blood prior to their fur-ther oxidation and ultimate removal from the organism by the agerrcy of various excretory organs, K 130 ON OXIDATION. From an albuminous fluid of comparatively simple composition, but undergoing constant change by the action of oxygen upon certain of its constituents, textures and organs of very elaborate structure, capable of performing complex functions, are con- structed, but, indirectly, through the agency of germinal matter. The highly important part which the blood plays both in the nutrition and disintegration of the textures of man and the higher animals cannot be advantageously discussed, unless the general natm’e of the changes effected in it and in the textures, by the process of oxidation, is refeiTed to in the first place. We may then allude to the operations occm-ring simultaneously in different parts of the organism under the two following heads : — the production of peculiar compormds in the tissues and organs, from certain constituents of the blood of a veiy different composition ; — the manner in which new substances are added to the blood to take the place of those which have been removed from it and appropriated. OF THE CHANGES EFFECTED BY OXIDATION. By the dh-ect or indhect action of oxygen upon certain constituents, soluble matters fit for appropriation by the germinal matter of the several tissues are prepared, while at the same time insoluble substances which are to be got rid of are converted into highly soluble compounds, which are easily removed firom the body. It has been very generally concluded that oxygen is dhectly concerned in the processes of nutrition and growth. But many considerations render it probable that it is required in greater proportion for the conversion of products resultmg from death and decay into chemical com- pomids which may be readily and quickly removed from the organism, by which the access of new pabiflum to the germinal matter is facilitated, than for the dii’ect nutrition and increase of the germinal matter itself Oxygen is to be regarded as a destroyer of compoimds already formed, not as a pabulum. It seems subservient to the process of disiutegration rather than to that of construction. It has been observed that the activity of cell growth and multiplication is remarkable at an early period of development when the process of oxidation is far less active than in the fully developed state. The organs in which these processes are most active in the adult ai*e ON OXIDATION. 131 remarkable rather for a very limited, than for a very free, supply of oxygenated blood. In the case of morbid growths, like cancer, which are remarkable for rapidity of growth, the supply of arterial blood is often very small. In acute inflam- mation of^the lung, the air cells become rapidly filled with “lymph,” the formation of which is dependant upon minute masses of germinal matter, and these have grown and multi- plied under conditions which were quite incompatible with fi’ee oxidation. Lastly, we shall find that the anatomical distribution of the small arteries to certain secreting organs and then- arrangement in the muscular and nervous tissues is such as to render it more probable that the arterial blood which they carry, takes part in the process of oxidation and dishitegration of materials already formed, than that it is con- nected with nutritive operations. Although there can be no question concerning the great importance of oxygen in the changes taking place in living beings, we are still in doubt as to the precise manner in which this oxygen acts, and the particular substances with which it combines. It is possible that the oxygen may be in some pecuhar state of combination before it acts, for it is well known that many substances which are not affected by free oxygen, readily combine with this substance, if it be already in a state of combination. The absence of red blood corpuscles from the blood of many invertebrate animals proves conclusively that these bodies are not essential to the process of oxidation. All the nutrient juices which permeate the various tissues hold oxygen and carbonic acid gases in solution, and it is certain that in some cases the action of oxygen is brought about solely by its aqueous solution. Wliile on the other hand, it has been con- clusively shown that oxygen is directly absorbed and carbonic acid evolved by the tissues as well as by the blood ; and the experiments of G. Liebig have proved that fi’ogs’ muscles con- tinue to absorb oxygen and give off carbonic acid even after their removal from the body. It is therefore certain that neither for the absorption of oxygen nor for the production ot carbonic acid, are the red blood corpuscles essential, but that chemical combination takes place between the oxygen and certain elements of the tissues. It is not possible, however, to K 2 132 THE CHANGES EFFECTED state confidently whether combination actually occurs in the tissue itself or is effected only through the agency of the masses of germinal matter so abundant in every tissue, and found in connection with the capillary wall. With regard to muscle it must not be forgotten that upon the sui'face of each elemen- tary muscular fibre are numerous delicate nerve-fibres, ha^nng many masses of germinal matter connected with them, and it is therefore at least possible that the process of oxidation may be taking place in connection with this tissue instead of in the interior of the contractile material, as is generally supposed. If the oxygen combines with or decomposes substances entering into the formation of the tissues, or immediately resulting from their disintegration, the process is merely a chemical one, and might, one would think, be imitated out of the body, but if only with matters resulting from the immediate disintegration of germinal matter, it cannot he so easily explained, and the change may perhaps be due to the elements coming into contact with the oxygen m some very peculiar state. If the fluids distributed to the tissues in which active changes are taking place are only imperfectly charged with oxygen, or if, although fully saturated, there he some impedi- ment to then- free cuculation through the tissue, imperfectly instead of fully oxidised substances result, which, from being insoluble or only slightly soluble, cannot be readily removed from the seat of their formation, and if these conditions inter- fering -with free oxidation, persist, such insoluble compounds accumulate. Not only do such substances impafr the action of the tissue in which they are deposited, but they interfere, to some extent, vnth the equable distribution of fresh nutrient material. In the process knovui as fatty degeneration the sub- stances resulting from the disintegration of the tissue mider the influence of a too limited supply of oxygen, accumulate in its texture and seriously impafr its action. In many cases not only is the existuig tissue rendered soft and rotten, and prone to give way, but the process of formation of new tissue to take its place is partly or entfrely suspended. The actfrnty of the process of oxidation seems to be in- creased by the presence of alkah, as is well known to he the case with the oxidation of organic matters out of the body. In cases in which the quantity of alkali in the blood is less than normal. BY THE PROCESS OP OXIDATION. 133 various substances in that fluid are not fully oxidised, and the so-called extractive matters, together with uric and oxalic acids, and alhed compounds, result, instead of the more soluble highly oxidised substances, such as urea and carbonic acid, which are so readily removed from the system in the excretions. The value of alkalies and of their salts with the vegetable acids, in all those conditions which are characterized by the formation and accu- mulation in the blood, or tissues, of imperfectly oxidised sub- stances, is well known to all practical physicians. The blood and the fluids wliich bathe the tissues in health exhibit an alkaline reaction, due to the presence of soda in combination with albumen, and with carbonic and phosphoric acids. It is probable that substances resulting from the biliary matters exert an influence similar to that of alkalies, and perhaps perform a very important office in facilitating that intimate contact be- tween elements havmg a strong chemical attraction for one another, which immediately precedes chemical action. It has been sometimes imagined that oxygen at once com- bines with the carbon of certain constituents dissolved in the blood or fluids, or even entermg into the composition of the solids of the tissues, but it is very unlikely that this should be the case. Although the present state of chemical knowledge has led chemists to infer that in the body highly oxidised pro- ducts result from the combination of successive portions of oxygen with the same substance, so that portions of hydrogen and carbon are successively removed, until a highly complex organic compound is reduced to one of a comparatively simple composition, and finally into the raw materials of organic hfe, carbonic acid and water, it is extremely doubtful if chemical changes occur in this manner in the organism. A process of the kind has indeed been performed in the laboratory;* for * An example of this degrading oxidation is afforded by the action of oxidising agents upon glycol (a chemical analogue o: Glycol Glycolic acid Glyoxal Glyoxalic acid Oxalic acid .... Formic acid Carbonic acid Water alcohol). C2Hg02 C2H4O3 C2H2O3 C0H2O3 C.2H2O3 0 HjOj C O2 H3O These substances, -with the exception of glycol, are also formed by the decompo- sition of nitrous ether (C2H5NO2) in contact wnth water. — [Note from Prof. Bloxam.[] 134 THE CHANGES EFFECTED BY OXIDATION. example, by subjecting certain complex chemical substances to oxidising agents, bodies are obtained “ in which the number of the constituent atoms of hydi’Ogen and carbon becomes pro- gressively less and less, until we arrive at bodies containing only two, and finally at boches containing only one carbon atom.” By oxidising stearic acid CjgH3g0.2 with nitric acid of moderate strength, the following bodies are obtained Rutic acid Suberic CEnanthic Pimelic Caproic Adipic Butyric Succinic Oxidation Products. ^ 10 ^ 20^2 C, H, A Cg H, A C, Hg 0, ^8 H14O4 C, H, A C, Hg 0, It must however be borne in mind that no e^’idence has yet been adduced of the occurrence of this successive modif^ring action of oxygen in the animal body. The chemist obseiwes in the laboratory that a substance under the infiuence of oxidismg agents gradually descends in the scale of complexity as the oxygen successively bmns ofi’ portions of its hydrogen and car- bon ; but it seems much more probable that the formation of the chemical substance in the animal body is due to the action of oxygen upon germinal matter, and that, so far from there being a series of changes, a highly, moderately, or sHghtly oxidised substance results, accorchng to the conditions present when the change occurs. The facts of the case render the chemical view of successive oxidations untenable. There is no good reason for believing that starch as starch, sugar as sugar, or fat as fat, unites with oxygen in the body. The theory that several chemical compounds must be produced between the starch, sugar, or fat on the one hand, and the carbonic acid on the other, is merely a chemical hypothesis, for winch as yet no very good gromids exist, since no one has produced these hitermediate bodies by causing oxygen to unite dii-ectly with any of the above sub- stances, and such intermediate products have not been satisfac- * Odling’s Lectures on Animal Cliemistrj. 1866. P. 48. OF CARRYING OXYGEN. 135 torily traced in the animal body ; while anatomical facts render it more probable that in the disintegration and removal of all textures germinal matter is intimately concerned, and that in- stead of oxygen acting directly upon the materials of the texture these are first taken up by germinal matter which in its turn is destroyed, giving rise to the substances which are usually con- sidered to result directly from the disintegration of tissue. Of the carrying of Oxygen to all parts of the Body . — The red blood corpuscles of vertebrate animals are the agents principally concerned in carrying the oxygen introduced into the organism by respiration, to different parts of the body. They also take up carbonic acid from the tissues and deliver it at the pulmonary sm'face where they receive the oxygen in exchange. The material of which the red blood corpuscles are composed pos- sesses in a remarkable degree, as has been already stated (page 126), the property of absorbing and parting -with oxygen and carbonic acid gases. F ernet (Comptes rendus, August 2nd, 1858) showed that blood corpuscles absorbed twenty-five times as much oxygen as the same quantity of water, and that the oxygen could be again expelled in vacuo at 98° F. This tem- porary fixation of gases by the material of the red blood cor- puscles is interesting, and, as is well known, other substances behave in a similar manner towards gaseous bodies ; for instance, ferrous sulphate will take up nitric oxide, which it again gives up in vacuo. Cuprous chloride takes up carbonic oxide, which may be disengaged fi-om it by boiling. One per cent, of common phosphate of soda enables water to absorb twice the normal proportion of carbonic acid, which may be expelled by agitation with an-. And many other examples of bodies possessing similar properties might be adduced. It is probable that some of the constituents of the red blood corpuscles undergo oxidation, and, perhaps, in this way a cer- tain proportion of urea, carbonic acid, and other substances may be formed ; while in cases where the oxidation is imperfect, m'ic, oxalic, lactic, and perhaps other incompletely oxidised bodies may result. The property exerted by the blood cor- puscles of absorbing gases is, however, greatly influenced by various agents, and there can be little doubt that the deleterious effects of many poisons are due to the influence they exert upon the absorption and removal of carbonic acid. The experiments 136 OXIDATION AND THE PKODUCTION OF HEAT. of Dr, George Harley have shown that snaJce poisoii, uric acid, and some other substances accelerate the absorption of oxygen and the exhalation of carbonic acid; while sugar, hydrocyanic acid, nicotine, morphine, cldoroform, and alcohol exhibit a contrary effect, and diminish the property which the constituents of the red blood corpuscles exhibit to unite with oxygen and give off carbonic acid.* The action of oxygen on cruorine has been referred to in page 127. Besides the property of actmg as carriers of ordinaiy oxygen, it is possible that the red blood corpuscles may be very efficient caniers of ozone. This opinion has been adopted by His and other observers, who state that they readily take up and give off this peculiar form of oxygen wliich possibly is instrumental in combining with certain products resulting from the decay of animal substances, and thus preventmg their deleterious action in the organism ; but, at the same time, it should be remarked that at present we know very httle of a positive nature concerning ozone or its actions. f Relation of Oxidation to the heat producing process . — Xot only has the development of heat in the animal body been attributed to the combination of oxygen with carbon and hydrogen of some of the constituents of the blood and tissues, but it has been concluded that in all cases in which the temperature of the body rises above the normal standard the actmty of the oxidising process must be necessarily augmented; and this notwithstanding the fact well and Aridely known, that certain states of disease, remarkable for an elevated temperatm-e, are associated with conditions seriously interferhig Avith the free introduction and distribution of oxygen. The fact that the temperatm’e of the body has been knoAAui to rise several degrees after death, in diseases in which for some time previously the introduction of oxygen into the blood had been seriously * Proceedings of the Eojal SocietjA 1864. t Much difference of opinion still exists concerning the nature of ozone. Schonbein considers that oxygen exists in three different allotropic conditions, of which, two are actire and opposed to each other ; these are ozone and antozone, equal quantities of which neutrahze each other and foim inactive or neutral oxygen, which may be separated one-half into ozone and one-half into antozone. Neither ozone nor antozone, have however, yet been isolated in a state of piuity, but are always mixed with neutral oxygen. It appears that Brodie discovered the polar condition of oxygen, and his views were apphed to ozone by Schonbein about ten years afterwai’ds. — (See Proc. Koy. Soc., vol. xi. p. 442.) HEAT PRODUCING PROCESS. 137 interfered with, would seem to he fatal to this view, although it is still widely accepted and taught. In all those conditions of system wliicli are accompanied by an elevation of the temperatm-e there is an increased production of germinal matter of the tissues of the body generally, while in cases in which there is a local increase of germinal matter, as in the formation of a common abscess, there is invariably a rapid evolution of heat. In both conditions the activity of the oxidising process is far below the healthy standard, while the temperature is many degrees above the normal range, and it is therefore impossible to resist the inference that the elevation of temperature is due rather to changes accompanying the increase of this germinal matter than to increased oxidation. The elevation of temperature is, in fact, associated with suboxida- tion, and therefore cannot, as has been affirmed, he dependent upon per-oxidation. We must not omit to notice that it has been recently shown by Berthelot that, by the hydration and dehydration of organic substances heat results.* Thus, sugar, starch, and fatty matter, by decomposition give rise to increased development of heat; and when albuminoid matters are hydrated and decomposed, or dehydrated and caused to enter into com- bination, heat is set free altogether independently of the process of oxidation. And, lastly, it has been demonstrated by MM. Estor and St. Pierre (Memories de la Societe de Biologie, 1865) that the venous blood retinning from an inflamed part is of a brighter tint than ordinary venous blood, and contains sometnnes more than twice as much oxygen. So that, although the temperature is several degrees higher than in the normal state, these ob- servations prove that less oxygen is consumed. Many facts would indeed justify the inference that the red blood corpuscles are more intimately concerned in the carrying away and distribution of heat, and thus in equalismg the temperature in various parts of the body, than in the actual production of heat. Supposing heat to be set free during the increase of the germinal matter of the capillary walls, which is associated vrith its increase in adjacent tissues, as in an ordinaiy case of inflammation, the effect of the corpuscles commg into contact one after the other with the enlarged masses of germinal matter, as they traverse the capillaries, would be to carry *■ Memoires de la Societe de Biologie, 1865. 138 ACTION OF OXYGEN. away the increased amount of heat and diSiise it over the system. In this way a plausible explanation is afforded of the great importance of keeping up the heart’s action ui diseases characterised by a considerable elevation of temperature, the beneficial effects of which have been demonstrated by observa- tion and abundantly confirmed by experience. Of the suhsta?ices resulting from the action of Oxygen upon constituents of the Organism. — It is proposed to refer in this place very briefly to a few only of the many compounds wliich are formed in the organism by oxidation. Many others will be alluded to when the various liquid secretions in which they are found come under consideration. The action of organs is in great part dependent upon oxidation, and the amount of textm’e destroyed ; and the quantity of oxygen required for the formation of oxidised products varies according to the intensity of the action. In many cases the degree of activity, or the actual amormt of work performed withm a given time, can, in fact, be measured by estimating the amount of oxidised substances produced. By the artificial oxidation of certain albuminous matters, oxidised products similar to those found in the body may be formed. Van Been states that, by the action of nascent oxygen de- veloped fi'om water by a constant current of electricity, he suc- ceeded in obtaining luea, uric acid and allantoin from albumen, and the two first from gelatin ; sugar and lactic acid from glycerine and from inosite ; and m’ea and allantoin fr'om uric acid. Many of these bodies, he says, may also be obtained by the action of ozone upon the same substance, and it is probable that the electrolytic ozone is the real agent in the above experiment. It has been stated that a great number of the substances fotmd in li^dng beings have been produced in the laboratoiy, and that there is reason to think that eventually every one may be artificially built up. When, however, the various instances which have been adduced are carefully investigated, it is sur- prising bow the number usually advanced becomes reduced, and it is indeed difficult to point out a single product proved to result immediately fr’om direct tissue oxidation, which can be formed synthetically from substances taken exclusively from the morganic kiirgdom,* and the least consideration will satisfy * Berthelot’s synthesis of formic acid from carbonic oxide derived from carbonate UREA. 139 any one tliat so far from the conditions under which compounds are formed in living things resembling those present when similar substances are produced in the laboratory, they are totally different. There is not indeed, as far as is yet known, the slightest real analogy between the chemical operations in the laboratory and those taking place in living germinal matter.* Urea (CH^N20). Among the substances probably resulting from the oxidation of compounds allied to albumen, one of the most important is urea. This is a crystalline excrementitious substance, very soluble in water, and readily diffusible. In health it is separated from the blood as it passes through the vessels of the kidney so fast that only mere traces can be detected, even if a large quantity of healthy blood be operated upon. But if the action of the kidneys is impaired by disease, or if the organs are extirpated, or if a ligatui’e be passed round the artery, so as to prevent the blood fr-om passing through the kidney, urea may accumulate in the blood in sufficient quantity to be detected in the serum without diffi- culty. Urea is not found in the muscles, although it can be obtained by the decomposition of kreatine and other substances found in muscular tissue. Recent researches have rendered it probable that much of the urea which is excreted is not formed in the tissues or in the blood, and merely separated and eliminated by the kidney, as was formerly supposed, but that a considerable proportion is actually produced in the kidney itself. It seems probable that the oxygen dissolved in the water which filters away from the arterial blood as it slowly traverses the capillaries of the Malpighian tuft, oxidizes certain constituents of the cells which hne the xiriniferous tubes, and that urea is one of the substances resulting from this action. It would appear that for the formation of urea in quantity a large proportion of fluid is necessary, and in the case of animals living mider conditions which interfere with the intro- duction into and passage through the system of large quantities of water, mic acid, and other less soluble substances seem to be substituted for m’ea. Crystals of urea are represented in plate VIII, fig. 70. of baryta by tbe action of iron at a bigb temperature, does seem to be entirely inde- pendent of organic life. * See papers in tbe Medical Times and G-azette, especially April 7tb and 14th, 1866. 140 URIC ACID — HIPPURIC ACID — LEUCINE. Uric Acid (C 5 H 4 N 4 O 3 ), plate VIII, fig. 71, is a substance less highly oxidised than ui’ea, and there are reasons for beheving that the latter is formed from it by oxidation. The proportion of uric acid increases under various conditions, in ■which the oxidising operations are interfered with, or imperfectly performed. It has been detected by Dr. Garcod in the blood and other fluids of gouty patients, in decided qimntity, and it may be regarded as one of the products of incomplete oxidation. In birds and certain reptiles the renal secretion consists principally of salts of uric acid. By the formation of urate of ammonia a considerable proportion of the waste carbon is removed by the kidneys of bii’ds, instead of nearly the whole being exhaled by the pul- monary surface. Dr. Odling remarks that the lungs of bhds are required to discharge only f instead of of the carbon resulting from the metamorphosis of nitrogenous tissue, as in animals. “ On this view, the comparatively large kidneys of birds and insects vdll have reference not only to the absolute amount of tissue metamorphosed, but also to the relative increase in the proportion of carbon excreted by thefr kidneys to that excreted by their lungs.” Hippuric Acid (CgHgNOg) is found in large quantity in the uiane of the horse and many graminivorous animals, and seems to be formed under the conditions which, in carnivora, lead to the production of luic acid. Hippuiac acid is formed in the human organism, and is always present in the m-ine. Accord- ing to Weismann and Hallwachs, nearly thirty -five grains are excreted by a healthy man in twenty-four hours. The re- searches of Kiihne and Hallwachs render it probable that hippuric acid is produced from the glycocine formed in the liver. Crystals of hippuric acid are figured in plate VIII, fig. 72. Leucine (CgHj 3 N 02 ) and Tyrosine (CgHjjN 03 ). Among the substances resultmg from the oxidation and decomposition of albuminous matters hi the body, and capable of being formed hi the laboratory artificially, are two bodies, leucine and tyrosine, which are of great interest. They may be obtained from all substances allied to albumen or gelatine by prolonged boiling with mmeral acids or alkahes. Dr. Odling has well remarked that these two apparently opj)osite processes are the same in principle. “ In each case the acid, or alkali, merely enables the protein or gelatinoid substance to react -with water FORMATION OF COMPOUNDS FROM THE BLOOD. 141 whereby one portion of it becomes oxidised into lencine, tyro- sine, &c., while another portion is hydrogenised into divers products.” Lencine and tyrosine cannot be built up synthe- tically from inorganic matter. They have been found in the normal tissues and secretions in small quantity ; but in diseases in which certain physiological processes are seriously deranged they are found in comparatively large proportion. This is particularly the case in certain diseases of the liver, as was shown by Frerichs. Not only may both substances be detected in the liver after death from acute yellow atrophy of that organ, and some other affections, but large quantities are often excreted in the urine during the patient’s life. Leucine has been detected in the saliva, pancreatic fluid, bile and urine. It is present in the intestinal glands and in the spleen pulp, and it has been obtained fi'om the thymus, thyroid and lymphatic glands. Boedeker states that leucine is an ordinary constituent of pus. In most cases, tyrosine is asso- ciated with the leucine. Both substances have been obtained from the tissues of many of the lower animals ; and from the cochineal insect tyrosine may be obtained in quantity, as was first proved by De la Rue. And there can be no doubt that they are much more widely distributed than was formerly supposed. They have not yet been detected in muscular or nervous tissue. Leucine crystals aie seen in plate VIII, fig. 76 . The various substances resulting from the oxidation of starchy and saccharine substances and fatty matters will be considered in the proper place. Among these, perhaps water (H2O), oxalic acid (C2H2OJ, acetic acid (C2H^02), mucic acid (CgHjpOg), butyi’ic acid (C^Hg02), and succinic acid (C^HgO^), are the most important. It is probable that when the process of oxidation is fully performed, carbonic acid is produced in place of these less highly oxidised organic acids. OF THE FORMATION OP VARIOUS COMPOUNDS IN THE TISSUES AND OROANS, FROM THE BLOOD. The special changes produced in the blood as it cfrctfiates through the capillaries of the different organs will be referred to in their proper place, but it is desirable to consider at once the general phenomena of the process of nutrition as it occurs in the elementary tissues of the body. 142 COMPOUNDS FORMED FROM THE BLOOD. Before any tissue can be nourished, certain of the soluble substances formed in the blood and held in solution in the serum, must permeate the walls of the vessels, and traverse the texture. The nutrient fluid having perhaps imdergone some change in its course, reaches the masses of germinal matter of the several textures, by which it, or certain of its nutrient con- stituents are taken up. Thus the germinal matter increases by the formation of new germinal matter; and the loss of that which has already undergone conversion into tissue is to some extent, completely, or in certain cases more than, compensated for. These processes in the healthy condition occur at a definite rate, but if the capillary walls be imusually thin, or be stretched, they necessarily become more permeable to the flruds passing from the blood ; or if the soluble nutrient matters be formed m the blood in undue proportion, a greater amount ot pabulum must pass to the tissues than is sufl&cient to compensate for the waste occurring. Consequently, under such cu’cumstances, the masses of germinal matter increase in size. If this excessive proportion of soluble pabifliim were not veiy soon taken up by the living germinal matter it would, at the temperatm’e of the body, soon undergo decomposition, and the resulting products would, probably, veiy soon destroy all the living germinal matter in the neighbourhood, as well as the existing tissue. At the same time that the masses of germinal matter increase in size and nmnber from increased access of pabuhun, the tissue or formed material becomes softened and altered in consequence of being too freely permeated by the fliud. Changes affecting the quantity and quality of the soluble nutrient substances in the blood, and their distribution to the tissues, frequently form the starting point of many morbid processes which, after proceeding for a certain time, may cease, or be caused to stop, or they may be compensated for by actions of a different nature being excited in other parts ; or, nm nin g on to a certain degree, the entue destraction of a tissue which cannot be renovated or replaced, may result. If a considerable extent of the tissue of some highly important organ as brain, lung, liver or kidney is affected, the patient’s death may occur long before the changes have reached the degree to which they often attain when confined to a small cucumscribed COSrPOUNDS FORIVEED FROM THE BLOOD. 143 portion of comparatively unimportant tissue as skin, bone or connective tissue. There can be little doubt that from the same pabulum different kinds of gei’minal matter produce substances having a very different chemical composition. Nor are we able to explain why one form of germinal matter should produce muscle, another fibrous tissue, another nerve, and so on. On the one hand there can be no doubt that all these different kinds of germinal matter have descended from one, and on the other it is probable that from them all a common form of germinal matter (pus) might result ; while the germinal matter of muscle or nerve may cease to produce these higher kinds of formed material, and give rise to fibrous tissue alone. It would seem as if, by virtue of some original power, the germinal matter of the embryo evolved in due order the several kinds of geiminal matter winch, under conditions brought about at the proper time, give rise to the formation of their respective tissues, but that if, fi’om altered conditions, the production of the seiies were inter- fered with, the formation of the special compounds and tissues be- came impossible in that particular organism. The changes would go on in order until the perfect organism was produced ; but any interference or derangement of these would render the ultimate attainment of the perfect form in that particular case impossible. The great importance of the nuclei, or masses of germinal matter of the tissues, in connection Avith each special formative process has been ah-eady indicated, and the conclusions arrived at render it very improbable that those which are constantly, and in such great number, met A^th in connection Avith the capillary vessels are unimportant, or are connected only with the development of the vessel as has been supposed. These masses of germinal matter, varying in size and number in different capillaries, and in the same vessels mider varying ch’cumstances, often project into the cavity of the vessel, and on the other hand extend beyond the line of its external wall. In inflammations and fevers these masses sometimes increase to four or five times their normal size.* Moreover, it is well knoAVQ that fatty degeneration of these capillary nuclei, and * Microscopical Researclies on the Cattle Plague, a Report to Her Majesty’s Commissioners, by Lionel S. Beale, M.B., F.R.S., &e. May, 1866. See also plate Y, fig. 46, and plate YII, figs. 67 and 68. 144 FOKMATION OF MILK. other morbid changes, are associated with most important altera- tions in the character of the blood, and serious derangement in nutrition as well as in the actions of the tissues. It is, there- fore, almost certain that these bodies are intimately concerned in the changes taking place in the blood and in the tissues in health. It seems not improbable that the masses of Hving or germinal matter under consideration are concerned in the selection and distribution of materials to the tissues as well as in the removal of substances from them and then introduction into the blood. When they project considerably into the interior of the vessel, the red blood coi’puscles must, one after the other, come into contact with them, and probably part with some of the oxygen with which they are charged. This may combine with some of the elements just set free by changes in the living matter, and many of those chemical compmmds which are obtained from the blood result. Under ordinary circum- stances these bodies may take up nutrient matter from the blood into which they project, w^hile on the side directed towards the tissues, the genninal matter may become resolved into substances fitted for the nutrition of the various textures. Milk . — Some of the most important substances formed by the agency of special germinal matter fi'om the fluid constituents of the blood are those which enter into the composition of milk. This secretion contains, without doubt, all the materials necessary for nutrition and tissue-formation — albuminous, sac- charine matters scwl earthy salts, dissolved; a.n(\. fatty matters in a state of extremely minute subdivision, suspended in fluid. All these dliferent classes of substances are undoubtedly formed by the secreting cells of the mammary gland, and the pabulum of those secreting cells must be derived from the blood. The ari’angement of the vessels, the disposition of then- nuclei, and their relation to the secreting cells, differ in no essential respect from what is observed in other secreting organs, and there can be little doubt that the material distributed to the cells of the lacteal gland is a simple serous fluid, the elements of which are rearranged by the germinal matter, and caused at last to combine to form the peculiar substances characteristic of milk. Casein. — This principle has many properties in common ■with albumen and fibrin. It is found abundantly in milk. Its occuiTence in other fluids has not been positively determuied. SUG^m AND FAT IN MILK. 145 The curd 'which is formed by heating millc in which a free acid existed, consists of a combination of casein with the acid. Heat alone will not effect the precipitation; but the addition of a little acid of any kind will occasion it. When dilute sul- phiu’ic acid is added to skimmed milk a precipitate occurs which is sulphate of casein. By digesting the clot thus formed with water and caifronate of lime, the acid combines with the lime, and the casein, which is set free, though not in a pure state, dissolves hr the water and may be obtained by evapo- ration. It exists in the proportion of 3 to 4 per cent, in women’s milk and in cow’s milk, and 2 per cent, in asses’ milk. Casein is coagulated very perfectly by the action of rennet (the fourth or true digestuig stomach of the calf) aided by heat. This property of coagulating casein is not to be attri- buted to the acid of the calf’s stomach, but to the organic principle (pepsin) resident in it ; for the power remains after all evidence of acid reaction has been removed. Rennet is one of the most powerful agents in causing the coagulation of casein, and it has been employed ni domestic economy for the manufactm’e of cheese, which consists of the cm’d mixed with butter, compressed and dried. So perfect is its coagulatiug power that not a particle of casein in milk submitted to its action, will remain uncoagulated. Casein comports itself with reagents nr a maimer very similar to albumen. In the coagulated state, it is insoluble in water, but soluble in liquor 'potasm. It is not precipitated by heat alone, in which respect it differs fr-om albumen. Casein, unlike albumen, is precipitated both by acetic and lactic acids. The fatty matters present in milk, amount to about 4 parts in 100. They occur hr the form of separate globules, each of Avhich is protected by an envelope of casein, which prevents them from rmniing together. Chevreul obtained fi-om butter of cow’s milk, the glyceride of stearic, palmitic, oleic, capric, capryhc, caproic, and butyric acids, but it is doubtful if these bodies exist in this state in the fi-esh secretion. Sugar of milk (Ci2H2^0i2) is a crystalhsable substance exist- ing in the proportion of about 4 parts in 100 of milk. In women’s milk, the sugar varies from 3 to 6 per cent. In asses’ milk it amounts to 4‘5, and in mare’s milk to 8 '7 per cent. It is formed only in the secreting portion, and probably by the cells, 146 SALINE AND FATTY MATTERS. of the lacteal gland and does not exist in the blood. K cane sugar or grape siigar be injected into the blood of animals while suckling then- young, these forms of sugar do not find their way into the milk, but milk sugar is formed as usual; while, if this latter substance be injected into the blood of an animal, it becomes converted into grape sugar, and is excreted as such in the urine. The saline matters present in milk, consist of alkaline chlorides and phosphates, with potash and soda in combination vdth the casein, and phosphates of lime and magnesia, which are dis- solved in company with this substance. The proportion of the different constituents of milk varies much under different cir- cumstances and in certain acute diseases. Fatty matters, — are to be obtained in greater or less proportion from almost all the fluids and solids of the animal body. They exist in three different states in animal bodies — 1, dissolved; 2, in the form of minute granules, as in the chyle ; and 3, in quantity, forming large or small globides. PI. I, figs. 1 and 2. The production of fatty matter from germinal matter has been already alluded to (p. 103), and minute examination of the elementary parts of the various tissues seems to show that fatty matters may be formed luider certam cncumstances from any of them. It may be regarded as certain, that a perfectly trans- parent albuminous material may give rise to the formation of fat ; it is well known that fatty acids are found among the pro- ducts of decomposition of albuminous substances. Xot only may germmal matter, which at one time was perfectly clear and transparent, develop oil globules, but fatty matter may be seen to appear m perfectly transparent and structmeless germinal matter after it has been removed fi-om the body. Careful micro- scopical observation will comdnce any one that the fatty matter of ordinary adipose tissue results from changes occuning in its germinal matter. PI. Ill, fig. 33«, b, c. While, when the fat already formed is to be re-absorbed, it is probable that it is again taken up by the germinal matter, and its elements trans- ferred to the germinal matter of the blood. In the case of adipose tissue which undergoes absorption rapidly, as the fat bodies of the abdominal cavity of the frog and newt, the masses of germinal matter of the fat vesicles and of the capLUaiies are large, and those of the latter numerous. PLATE YlII. CRYSTALS. UREA. URIC ACID, &c. Ti^. 70. Eig. 71. Rig. 72. Fig. 73. Fig. 74. % ^ I EpiUielial cell. Air-cell of lung. Cattleplague. Myelin particles in outer part, x 1800. Myelin particles from the external portion of cells in air-cells of the lungs. Cattle Plague. X 2800 Fig. 77. Fig. 78. Fig- 76. itfeo of an Incli X 215. L, S. B.J [To face p. 146. SAPONIFIABLE AND NON-SAPONIFIABLE FATS. 147 The saponifiable fats occun’ing in the organism of man are Olein, Margarin, or perhaps more correctly, Palmitin, and Stearin. Margai-in is probably not a simple substance. PI. VII, fig. 69. Margaric acid consists, accordhig to Heintz, of a mere mixture of stearic and palmitic acids. The fatty acids are Oleic acid (CjgH3^02), Steanc acid (CjgH3g02), and Palmitic acid (C|gH3202). . Cholesterin (C2gH4^0), PL VIII, fig. 77, and Serolin, are the only non-saponifiable fats fomid in the organism. They are very widely distributed and exist in large quantity in connection with all parts of the nervous system. They are also present in the bile ; and cholesterin is not milrequently met with almost pure in certain kinds of gall-stones. These non-saponifiable fats in- crease as the textures in which they are found advance in age. In yomig textm’es the proportion is much smaller than in the adult, and at an early period of development mere traces are to be detected in nei-ve tissues, which in theii’ fully developed state yield a considerable proportion. Moreover, in many tissues in which at an early period, and even in a fully formed state, no cholesterm can be detected, this substance exists in considerable proportion in old age ; and in certain diseases in which morbid changes induce, at a comparatively early peiiod of life, altera- tions resembling those which occur under ordhiary cu’cum- stances in advanced age, cholesterin is one of the substances resulting fi-om the altered chemical changes. Myelin . — It has been recently shown, by some very interest- ing researches of Beneke’s, that the peculiar fatty matter termed myelin may be obtained fi.’om all the tissues of the body. In the liver it exists in large quantity ; it is found in all parts of the nervous system; and much maybe obtained from the yolk of egg. It is yielded even by albuminous matters and fibrin. IMyelin was fu'st described by Vu-chow, who showed that it was not an ordinary fatty matter, as it swells up and is soluble in water. Its peculiar characters are well known. It is colom*- less, glistening, semifluid, prone to form drops, and capable of being drawn out into long threads, which curve and twist into the most peculiar forms. The masses often exhibit double contoiu’s, and not unfL-equently many lines may be discerned equidistant from one another, but varying in their apparent thickness and intensity. Myelin is soluble in hot alcohol, ether, L 2 148 MUSCLE. and turpentine. It contains both nitrogen and phosphorus, like Fremy’s cerebric and oleophosphoiic acids. It yields the reaction characteristic of the biliary acids, with Pettenkofer’s test.* Beneke obtained the reaction with the alcoholic extracts of almost all the tissues. Cholesterin is a necessary com- ponent of all forms of myelin, and it seems to be rendered soluble by the other constituent of this substance ; indeed, Beneke has shown that myelin is in fact a mechanical mixture of cholesterin and cholate of lipyl. It would seem not improbable that, as Beneke suggests, the oxide of lipyl (the hypothetical body which yields glycerine on hydi’ation) separated from the fatty acids by the action of the pancreatic juice, is presented in a nascent state to the biliaiy acids which then combine with it, forming a cholate of Hpyl. This then becoming mechanically mixed with the cholesteiin, myelin results. Myelin is repre- sented in plate VIII, figs. 73, 74, and 78. Muscle . — The germinal matter of both striped and imstriped (voluntary and involuntary) muscle produces contractile mate- rial, which consists principally of a substance termed syn- * The following are Pettenkofer’s directions : Pour a portion of the suspected fluid into a test tube^and add Enghsh sulphuric acid, guttatim, to about | the volume of the fluid, whereby the temperature is considerably raised. The addition must be made so gradually that the temperature shall at no time exceed 145° F., as otherwise tlie choleic acid is too much changed ; then add 2 — 5 drops of ordinary cane sugar solution containing 1 x^art sugar to 4 — 5 parts of water, and shake the whole. If choleic acid be present, a more or less deej) violet red colour will be produced according to the amount of bile in solution. Keukomni (ueber die Nachweisung der Gallensauren, &c., I860,) proposes the foUowing modification: “A single drop of a ^ j)®’’ cent, solution of choleic or glycochohc acid will yield a splendid pui-ple violet colour if it is brought in contact with a droj) of dilute sulx)hui'ic acid (4 water, 1 sulphuric acid) and a trace of sugar solution in a j)orcelain cup, and then gently warmed over a spirit lamp ; as 1 cubic centimetre equals about 8 drops, it is thus possible to demonstrate milligr. of bfliai’y acid with com^ilete accm’acy.” As a further test he suggests “ the biliary acid or salt is to be sprinkled with a small quantity of concentrated sulphuric acid moderately warmed and then water added. The resinous flocculi that subside are to be separated from the acid, washed with water, but not so as to remove all the sul- phuric acid, and then again gently heated in a porcelain cup till coloration ensues. If the residue be taken uq) in a small quantity of alcohol, and the green solution be evaporated, the interior of the cup will be coated with a deep indigo blue film, even when but httle acid has been used. If the bihary acids have been impure, or the sulphuric acid or the temperature react too long, the pigment film will be green.” See the abstract of Beneke’s Memoir “ On the Occmrence, Diffusion, and Action of the constituents of the Bile in the Animal and Vegetable Organism,” by Dr. Duffin, Archives of Medicine, vol. iv, p. 192, 1865. SUBSTANCES IN MUSCLE. 149 tonin, or muscle fibrin. The contractile material is associated with a small quantity of delicate passive texture, moistened with fluid holding several different substances in solution. Syntonin, from avvrovo'i, contains in 100 parts, C 54‘06, H 7 ‘28, N 16'05, 0 21‘5, S I'll. It resembles fibrin in many of its pro- perties, but imlike this substance it is insoluble in a 6 per cent, solution of nitrate of potash. Kiihne has obtained syntonur in a fluid state from striped muscle, and considers that this is its condition as long as contractility lasts, but that stiffening of muscle after death, or rigo7' mortis, is due to the coagulation of this substance. It dissolves readily in water containing joVo of hydrochloric acid. When the acid solution is neutralised the syntonin forms a jelly. Soon after death a free acid is formed in the juice of the muscular tissue, probably from changes in the syntonin. Du Bois Eaymond showed that no free acid was to be detected in the muscles in a state of rest. Indeed, as long as the muscle retains the property of con- tractility it appears not to exhibit an acid reaction, but after it has lost this property, acid is rapidly developed. The amount of acid to be obtained from the juice of muscles after death is remarkable, and Liebig has calculated that the voluntary muscles alone contain more than sufficient to destroy the alkalinity of the blood (Lehmann). The colour of the muscular tissue of animals with red flesh is an organic colouring matter. It is probably allied to hsematin, and the intensity of the coloiu- is increased by oxygen. Among the chemical substances obtained from muscle, and probably resulting fr'om disintegration consequent upon action, are the following : Kreatim, Inosite, and Phosphoric, Lactic, Butyric, and Inosic acids. Kreatine (C^HgNgO^, H 2 O) is a crystallisable substance, ex- isting in the proportion, according to Gregory, of about five grains in one pound of flesh. The muscles of birds, probably from their much greater activity, contain about three times as much kreatine as those of fishes. Kreatinine (C 4 HyN 30 ) is also found in the juice of muscle. Inosite (CgHi20g, 2 H 2 O), or muscle sugar, is soluble in alcohol, from which it may be obtained in crystals resembling those of gypsum. According to Scherer it is isomeric in its anhydrous state with anhydrous grape sugar. This substance hitherto - 150 CHEMICAL CONSTITUENTS OF NERVE. has only been found in the mnscnlar tissue of the heart in animals (Lehmann). Kidney-beans contain about 0'75 per cent., when unripe. Inosio acid (CiqHj^N^Ojj?) is not crystalline, but forms ciystallisable salts with the alkalies. Phosphoric, Lactic, and Butyric acids, obtained from the juice of flesh, have the same characters as those acids obtained fl-om other animal fluids. The fatty matters contain olein, palmitin and stearin, with oleo-phosphoric acid (Valenciennes and Fremy). The ash of flesh contains phosphate and sulphate of potash, chloride of potassium, earthy phosphates, and ii-on. Nerve. — The nervous tissues consist principally of an albu- minous substance combined with peculiar fatty materials, perhaps partially dissolved as soaps. The nerve cells contain more water and albuminous matter, but much less fatty matter, than the nerve fibres in connection with them, and at an early period of development the proportion of fatty matter present in the neiwous system is very small. The tubular membrane, or nerve sheath, is composed of a substance nearly allied to elastic tissue m composition. It appears probable that the albumino-fatty material existing in such large proportion in the medullary sheath, or white substance of Schwann, accu- miflates as the nerve fibres advance towards their fully deve- loped condition. This fatty substance seems to form a pro- tective covering to the axis cylinder vdthin, and probably acts as an insulator, by which currents passing along neighboining axis cylinders are prevented from acting and reactiug upon one another by induction. The fact that this fatty matter of the white substance is neither formed nor removed under the same circumstances as the fats of adipose tissue, woifld seem to show that its relation to the ordinary changes occuning in the body is of a very different kind from that of the ordinaiy fats. The axis cylinder of the nerve, which, like other textm-es, is formed from germinal matter, consists of a substance allied in its chemical properties to yellow elastic tissue. It seems a very passive kind of formed material, and at any rate in many instances resists the action of chemical reagents, wliich com- pletely destroy many other tissues. The nerve textm-es contain, besides ordinaiy albumen, modifications of albuminous matters, which are not precipitated EPITHELIAL TEXTUEES. 151 from their solutions by boiling. Von Bibra states that the brain fats consist of cerebric acid, a number of different fatty acids, and cholesterin. Cerebrin is of neutral reaction, and soluble in boiling alcohol and ether. According to W. Miiller it contains in 100 parts C 68‘35, H 11'30, N 4-69, 0 15’66. It is also found in the yolk of egg and in pus, and probably in the fat of blood serum (Gorup-Besanez) . Oleo-phosphoric acid was discovered by Fremy, and has been found in the brain, spinal cord, kidneys and liver. Olein, stearin, oleic and stearic acids, in part combined with soda, potash, or lime, and cholesterin, are also present in the nervous tissue. The substance known as myelin, which exists in connexion with the nerves in very large quantity, has already been referred to (p. 148). The chemical substances obtained from white fibrous tissue, cartilage and bone, have been briefly referred to in page 113. Yellow elastic tissue yields a substance which is very insoluble, not altered by prolonged boiling hi water, quite insoluble in cold strong acetic acid, and scarcely affected by potash and soda. By digestion in sulplimic acid, elasticin yields leucine, and by the action of nitric acid, xanthoproteic acid is formed. Bonders has arrived at the conclusion that all fully formed cell mem- branes are composed of a substance closely allied to yellow elastic tissue, which might be termed animal cellulose. At an early period, however, of the process of cell formation, no such substance exists in any cells, and in some, no cell- wall can be demonstrated at any period. The epithelial textures, as epithelium, epidermis, various kinds of nail, horn, and hair, wool, whalebone, feathers and tortoise- shell, consist of a substance allied to the protein compounds and containing from 1 to 5 per cent, of sulphm’. Associated with the protein compound, at an early period of life, is a certain proportion of amyloid (see page 111). The coloul’ing matter formed in connection with epithelial textures is produced at the same time as the soft, horny material. It is an organic colour- ing matter, which, lilce other natural organic coloming matters, results from changes occurring in a perfectly colomdess germinal matter. 152 CONVERSION OF PABULUM INTO BLOOD. THE CONVERSION OE PABULUM INTO BLOOD. The simplest organisms obtain their pabulum from the medium which surrounds them. This seems to be at once absorbed into the organism, taken up by the germinal matter, and converted into the pecidiar constituents of the body. But in more complex structures, the pabulum derived from with- out, is not already adapted for the nutrition of the tissues generally. It is, in the first instance, taken up by certain special masses of germinal matter which grow and multiply at its expense. The substances resultuig from the death of these particles, consisting of compounds not to be detected in the original pabulum, are afterwards taken up by the ger- minal matter of the various tissues. Thus the spongioles of the plant probably absorb the crude materials from the soil in a state of solution. These are converted by the living matter into new substances, wliich circulate in channels, and are taken up by the germinal matter entering into the formation of the cells of the various tissues of the plant. In like manner, it appears that nutrient materials in their cmde state, cannot be du-ectly appropriated by the tissues of man, but must pass through several stages of preparation, undergoing conversion entfrely into new substances which did not exist before, and which are peculiar to liis organism alone. Even substances closely allied in composition to the tissues to be nomlshed, and in a state of solution, are not dh-ectly appropriated by the tissues ; nor, if injected into the blood, would they be rendered by that fluid fit for this purpose. They must be first modified by various preliminary operations, taken up successively by two or tln-ee series of cells (masses of germinal matter), of com-se in a totally altered form, and not until then are compormds produced, which are adapted for the nutrition of the tissues. If either of these successive processes be modified by an altered action of the cells the pabidimi is not properly prepared and the textui’es suffer in nutrition. The new constituents, whether albuminous, starchy, saccha- rine, or fatty, which are to be added hi the blood, to supply the place of the materials which are being removed from it in the process of nutrition, are probably taken up from the intestinal surface in a soluble form, and appropriated by germinal matter, — CONVERSION OF PABULUM INTO BLOOD. 153 entering into the composition of the chyle corpuscles which grow and multiply in the lacteal vessels, as well as the white blood corpuscles, circulating in the capillaries. At the same time that these masses of germinal matter are increasing in size, and giving rise by division to new masses, a certain proportion of the mass probably becomes resolved into the various soluble substances which enter into the composition of the serous fluid. All the new pabulum must, therefore, pass into the blood in these two forms, as masses of living germinal matter, varying in size, which become the white, and at length the red blood coi-puscles, and serum which consists of a solution of albumen in water, with the so-called extractive matters, traces of fatty matter, and various kinds of salts. There is reason to infer that very few alimentary substances can be taken up dh-ectly by germmal matter of the intestinal surface. Most of the materials entering into the composition of our food require most important preparation and undergo great modiflcations before they can be appropriated by any living matter at all. Thus, starch is converted into a form of sugar by the sahva and pancreatic fluids — fatty matter is rendered capable of absorption by the action of the latter secretion and the bile. Insoluble albuminous matters are rendered very soluble by the action of the gastric juice, and most important changes, which are as yet very imperfectly understood, are doubtless effected in the contents of the alimentary canal by these and the other secretions poured into it in such enormous quantity. The sub- stances so prepared are appropriated by the germinal matter, and this appropriation mainly constitutes what has been termed primary assimilation. The germinal matter of the tissues, as has been already explained, undergoes conversion into the tissue itself. This tissue is often greatly modified after its formation. It may tmdergo condensation by the removal of water and the ap- proximation of its particles, or it may be rendered firm and hard by the deposition of calcareous or other salts in its sub- stance or in its interstices, and these may chemically combine with it, or be merely deposited. The organic matrix of bone, teeth, and some other tissues is first formed by germinal matter, and the earthy material to which its physical properties are entirely due, is subsequently deposited. The formation of the 154 ALTERATION OP FORIIED MATERIAL IN DISEASE. matrix itself is the result of a vital process, but the impregna- tion of this matter with saline matter is probably due to chemical changes alone. We may, then, conclude that in the preparation of the sub- stances required for the nutrition of the geiminal matter of the different tissues, the lifeless pabulum, after being rendered soluble, is appropriated by the living matter of the cells of the villi. Portions of this germinal matter then die, and the pro- ducts resulting from their death become taken up partly by the germinal matter in the lacteals, partly by that in the walls of the capillaries, and partly, perhaps, by the wliite blood corpuscles. These forms of germinal matter probably give rise to white blood corpuscles from which the red blood corpuscles are produced. By the action of oxygen upon these last, pro- bably two series of compormds result ; one which is capable of being appropriated by the gei-minal matter of the capillary walls and that of the tissues, while the other becomes resolved into carbonic acid, ru-ea, and other compounds which are eliminated by particular organs of the body. From the nutrient matters so prepared the germinal matter of the various tissues derives the substances for its nutrition, and these, when taken up, become part of its substance, and take the place of that portion wliich has recently undergone conversion into tissue. In the removal of old and worn out tissue and the intro- duction of its elements into the blood prior to their elimination by the various excreting organs, it is probable that similar operations occm*, the old texture being taken up by ger mi nal matter, this undergoing conversion into formed material, which is appropriated by the germinal matter of the vessels and the white blood corpuscles, until at last, by the disintegration of those substances which serve as pabulum to the secreting cells of various glands, imperfectly, or highly oxidised bodies, EU'e prepared, which are at once earned off. Alteration in composition of Formed Material in Disease . — The integrity of the formed material of many tissues is preserved, and the activity of its fimction maintained, by the continual passage of fluid through it. The disposition of the nuclei, or masses of living germmal matter in the healthy tissue, is such as to ensure the existence of currents through every part. If fi’om a change in the composition of the fluid itself, or in consequence ALTERATION OP FORjVtED MATERIAJj IN DISEASE. 155 of an alteration occurring in the masses of germinal matter, the tissue is no longer permeated, or permeated irregularly, by these cm-rents of fluid, most important changes soon result. The products of decay not being carried off as fast as they are formed, and not being converted mto readily soluble sub stances, accumiilate, and seriously interfere with the action of the tissue already formed. Such is, in part perhaps, the expla- nation of the changes which occm- in the formed material of various cells and elementary parts, winch are said to be affected by degeneration. The formed material of tissues is also sometimes modified in consequence of being bathed Avith fluids of composition different to that which obtains in the healthy state, and this alteration m composition may be diie, in part, to the characters of the pabulum, and partly to the conditions under which its preparation is carried on, or as frequently happens, to the cu'cumstance that certain excrementitious compounds, which ought to have been enthely eliminated, remain in the fluid. The character of the formed material Avill also be influenced by the rate of its formation, and this will, to some extent, depend upon the amount of pabidum which reaches it, and which, of course, varies much in different cases. [In the preparation of this chapter, the Author as received pinch valuable help from his friend and colleague, Professor Bloxam.] y ' / — ^'O V -/.< ]\1 CHAPTER III. OS' TISSUE, ITS STRUCTURE AND PROPERTIES. — TISSUE PERMEABLE TO ELUIDS. HARDNESS. ELASTICITY. — EIBROUS STRUCTURE. EPITHELIAL TISSUE. — CONTRACTILE TISSUE. NERTOUS TISSUE. Although the different tissues are apparently foimed in the same manner, they vary remarkably in then- structui’e, an'ange- ment, composition, and properties. It is the special province of the histologist (taro 9 , tissue, web) to investigate the structure and arrangement of the various tissue elements. We shall not, however, restrict ourselves to this alone, but in the course of oiu enquu'ies into structiue shall endeavoiu to learn some- thing about the development and action of the textm-e ; some observations upon structure have been already made in Chap- ter 1, and upon page 70 will be found a tabular view of the tissues of the human body. We propose in this place to offer a few general remarks upon the properties and minute structiue of tissues before we describe seriathn the individual characters of each. It has been shown that all formed material was once in the state of germinal matter. The characters manifested by the formed material, or tissue, after it has been produced, are dependent, in great measure, upon the changes wliich occurred dm'ing the living state. So also must we refer the structure which the formed material exhibits, as well as its properties and chemical composition, to the changes which occmued when the matter was living, mochfied by the influence of external circumstances at the moment it passed into the formed condi- tion. Nothing seems more ridiculous than to attribute the properties of tissues peculiar to things Imng to the properties of the lifeless elements entering into theu composition — to refer elasticity, contractflity, porosity, or other characteristic property to the properties of the oxygen, hydrogen, nitrogen, carbon, and of other elements of which the tissue is composed. To suggest that the addition of a little nitrogen or oxygen to a non-contractile mass might induce in it the property of contractility would be rightly considered, frivolous, and yet suggestions as absurd have been seriously advanced, if not TISSUE PERMEABLE TO FLUIDS. 157 really entertained, by some who it would seem are determined to force the acceptance of the dogma that all the properties of things living are due to the properties of the elements entering into then- composition, and to these only. Tissue 'perme.ahle to Fluids. — The tissues of living beings are in almost all cases traversed by fluid holding m solution cer- tain matters which are to take part in nutrition or which result from disintegration. In this way the integrity of the texture is preserved, and gradual changes in it are effected. Even the hardest tissues are not absolutely dry or impervious to fluid, and there is reason to think that the intimate structm-e of tissues so hard as bone, dentine, and enamel is preserved by the con- tinual passage of small quantities of fluid through it. In many soft and very moist tissues the very rapid circulation of fluid is continually going on, as may be proved by causing coloured fluids to traverse it. The natural fluid which passes to and fro in every part of the tissue through hiterstices too delicate to be seen, preserves it in a healthy state. If this process were to be suspended even for a short time, the tissue would suffer and in some cases be so damaged that it would no longer perform the function it was formed to discharge. In effecting the flow of these currents of fluid through the tissue the ger- minal matter is the active agent. And if a tissue be care- fully examined it will be found that the position of the masses of germinal matter with respect to one another, and to the source from which the fluid is derived, is such that not a particle of the intervening tissue can escape being bathed with new fluid as it flows towards or from the vessels which supply fresh pabulum and carry off the deteriorated matter. In this way changes are continually provoked in every part of a solid tissue. There is no stagnation anywhere, and every particle is successively bathed with fresh portions of fluid. If from change in structrne, or from the death of the germhial matter, stagnation does occur, the tissue soon suffers. It ceases to act, soon loses strength, and slowly degenerates, or is sud- denly destroyed, in which case it is soon separated fi-om the surrounding healthy parts, and is detached as a lifeless decom- posing mass, capable of being appropriated only by the lowest forms of vegetable life, which grow and multiply at its expense if the germs are brought into contact with it. M 2 158 PHYSICAL PROPERTIES. In some instances the exact paths taken by the nutrient fluid as it flowed towards the living matter duiing life can be demonstrated in a tissue removed very soon after death. In the mtervals between the converging lines which the fluid takes towards the centre of a cell, formed material has been deposited in such a manner as to give rise at last to a stellar arrangement of tubes which open into a central space originally occupied by gennmal matter. — See fig. 28, plate III, p. 84. Tissue, there is reason to think, is so constmcted in some cases as to allow certahi fluids only to travei’se it and to prevent the passage of others. And it may be formed in such a way that fluid will permeate it in one dhection only, or the internal structm-e may be such as to allow special fluids to traverse it in one direction, and solutions of another character in the opposite. Hardness . — The joroperty of hardness which is essential to certain textures is due either to the gradual desiccation of a soft protein formed material, or to the deposition in a soft matrix previously formed of mineral salts which undergo a^modification and hardening in the tissue vdth which they sometimes seem to blend, if not to chemically combine, but the salts never assume in the substance of the tissue their ordinary crystalline forms. Hair and horn and nail are examples of tissues of the fii’st class. Of such textures the external hard coriaceous coveiing of insects, and some Crustacea is as firm and hard and as serviceable for the fii’m attachment of muscles as bone itself. Bone which forms the basis of support for the soft parts in man and the higher animals, the dental tissues, the calcareous plates of the starfishes and echini, the external integument of some of the Crustacea, and the shells of many mollusca are tissues of ex- ceeding hardness in which this physical property is due to the impregnation of an organic matrix with hard calcareous salts. In some instances the firmness of the tissue is due to im- pregnation Avith sihca, or some other mineral substance. Elasticity . — Every kind of tissue, whether soft or hard, possesses the property of elasticity, so that it will return to its original bulk soon after it is released from moderate compres- sion or stretching to which it may have been subjected. Some tissues are more remarkable for elasticity than others, but even the very softest and most fragile are elastic. This may be ELASTICITY OF TISSUE. 159 shown by placing the tissue in a medium of much higher specific gravity than that which bathes it during life, when it will be found that although considerable shrinking may have at first taken place, the particles of the tissue by reason of their elasticity will gradually return to the positions they originally occupied. Thus the softest textures may be immersed in strong syrup or glycerine, which are highly efficient preserva- tive media, without any reduction in volume if only we are careful to increase the density of the fluid by slow degrees, and allow time for the gradual expansion of the tissue after the reduction in volume which it has undergone in consequence of the osmose of the fluid from its interstices into the dense surrounding medium which of course ensued immediately it was introduced into the dense fluid. A knowledge of this fact is of the utmost importance to all engaged in microscopical researches upon the minute structure of the tissues. — See the method of preparing tissues given on page 57. Some tissues are specially valuable for their elasticity, as for instance the different forms of elastic tissue, and it is very remarkable that as the fibres or laminee of this tissue gradually increase by the deposition of new matter upon the outside, this last is so laid down that as it contracts and acquires consistency and firmness, its elasticity accords with that of the texture pre- viously formed, so that there is no puckering or irregularity or unevenness to be observed in any part of the fibre, which how- ever curls up a little on the side opposite to that on which the new tissue was last deposited. In connection with the vascular system elastic tissues play a highly important part, and the due performance of the respu'atory act is dependent upon the elasticity of the prdmonary textures. Indeed, to such an extent is this the case, that if the structure of the elastic tissue of the lungs becomes impahed by disease, serious derangement of the respiratory function follows. The elastic membrane con- stituting the capillaiy wall not only permits the occurrence of great alterations in the mternal pressure of the blood without the danger of rupture, but allows varying proportions of nutrient fluid to escape into the surrounding tissues. The minute quantity of fluid w'hich permeates the capillary walls when these recoil upon a narrow quick moving stream, contrasts remarkably with the large proportion poured out when the capil- 160 FIBROUS STRUCTURE. laries are stretched to five or ten times their diameter, or distended to the utmost with scarcely moving or temporarily stagnant blood. Indeed to such an extent may the process of distension and engorgement be carried that longitudinal rents or fissures may result. Through these red blood corpuscles even, as well as the minute portions of livhig matter found in the liquor sanguinis, fig. 44, plate V, page 124, may freely pass. When, however, the distending force is withdrawn, the capillary, by reason of its elasticity, returns to its former diameter, and resumes its ordi- nary appearance of delicate homogeneous membrane, without an indication remaining of any rent or tear, or opening through which a very minute solid particle could make its way. Fibrous Structure . — Fibres may be dravm out, as it were, from a mass of germinal matter in one, or in two or more directions, giving the mass of germinal matter an oval, spindle-shaped, or stellate form. Thin structureless expansions may be produced directly by germinal matter, or fibrous-like membranes may be formed, in which the fibres run parallel, or cross at various angles, giving rise at last to a tissue of such extraordinary com- plexity that it seems almost hopeless to endeavour to um’avel it, and impossible to find out how fibi’es, running in so many different dh’ections, were developed. By careful examination at different periods of the development of such a tissue, the observer will however, in some cases, be able to form as clear a conception concerning the manner in which the interlacing fibres were deposited, as he may gain of the mode of formation of a complex spider’s web, by careful examination at short inteiwals during its formation, without having vdtnessed the creature actually at work. So delicate are the fibres in some tissues that they can only be detected by resorting to artificial colour- ing. Careful investigation leads us to think that in many cases in which a tissue appears perfectly homogeneous and structure- less, it is really composed of excessively fine fibres, which can- not be clearly discerned by aid of the methods of investigation at our disposal. The peculiar characters and ammgement of some structures can be accounted for by the movements of the germuial matter during then formation, and conversely we may learn much concerning the movements of germmal matter by a minute and care fid investigation of the elementary an-ange- ments of the tissue which has been formed by it. In the for- EPITHELIAL TISSUE. 161 mation of the elastic cartilage of the epiglottis, and some other textures, it seems probable that each mass of germinal matter revolves -while it forms delicate fibres, which accumulate, and at length appear to be arranged concentrically roimd the space in which it lies. The fibres, in this case, seem to be formed some- what in the manner in which the caterpillar spins its cocoon, except that in the case of the tissue, the process is mterrupted, while the last is a continuous operation. The attachment of the germmal matter to some of these fibres may be chstinctly seen hi the particular texture referred to, pi. XV, fig. 130. In comiection with the ganghon cells of the sympathetic of the frog, one of us (L. S. B.) has described a very remarkable sphaJ arrangement of the nerve fibres, which can be readily explained by supposing movements of the germinal matter, while we believe in no other manner can the facts be satisfactorily accounted for. So also by the careful study of the arrangement of the twistmg of nerve fibres in many tissues, we become convinced of the never- ceasing movement of the masses of germinal matter, not only during the formation and development of the fibres, but after- wards, dining the adult period of life. In this way only can the highly intricate structural arrangements, familiar to ns in many organs of man and the higher animals, be explained. Changes, however, take place m many kinds of tissue after the formative act has been completed. In some cases the part which was first produced dries up, and gives rise to ure- gularities or cracks, which appear as peculiar markings, and may be characteristic of the fully formed structure. Sometimes a tissue, which for a long time appears homogeneous and clear, gradually acquires a fibrous appearance from the tendency of the old tissue to split, or cleave in certain directions, which will m fact be found to correspond to the lines in ivhich new tissue was deposited at an early period of formation. Epithelial Tissue . — One of the simplest forms of tissue found in man and animals, and perhaps that which is produced most easily and most quickly, is cuticular epithelium. Possessing elasticity, and considerable extensile property, performing the passive office of protecting more important textures beneath it, upon which it rests, and with which it is often connected, this tissue is readily replaced, if removed, and when injured is quickly and effectually repafred. Epithelial tissues exhibit. 162 DIFFERENCES IN CHARACTER however, remarkable differences in property in different situa- tions. One may be dry and firm, hard and resisting, fonning a sharp point or cutting edge, as in certain kinds of nail and horn ; another may be supple and elastic, like the epidermis, or soft and moist, like the epithelial tissue of raucous membranes and internal passages, while some forms of epithelial tissue are semi-fluid, or more or less viscid, of the consistence of mucus. In hardness and resisting power different forms of epi- thelium differ from one another as much as any one of them differs from other tissues. The student would scarcely believe that the soft, moist epithehum of a mucous membrane was in any way related to the hard dry tissue of which nail, hom, and hair consist, or to the hard calcified textm'e of shell, dentine, or enamel ; but if he were to examine these textures at an early period of thefr development he would be convinced of their very close relationship, and would find that the formed material was produced in the same manner in all. It may be truly said that one thing can scarcely differ more fr'om another than the soft, moist epithelium of a papilla of skin or mucous membrane does from the fii’m cuticular tissue of hom or hair, and yet under modified conditions the former may become so altered as to constitute a tissue which any one would admit was closely allied to the latter structm-es. The fibre-hke cells con- stituting certain forms of hah, hom, and nafi. are very different from other fonns of epithelial tissue, but, as is well known, well-developed horns are occasionally produced on the skin, and the horny material consists but of modified epidermis. The long drawn out cells or fibres of enamel and denture are probably modified forms of epithelium, the formed organic matter of which has been gradually impregnated with cal- careous particles. Nor do epithelial textm-es differ fr'om one another less remarkably in stmctine and physical properties than they do in function. The cell which secretes bile, or mine, or gastric juice worrld seem to be very far removed from the epithelial cell of the cuticle or of a mucous membrane, for the former are instruirrental in the production of secretions possessing very peculiar properties and coirtairring much water, while the last produces oirly the dry horny matter which accumulates, or a softer material which, however, by gradual drying may be OF EPITHELIAL TISSUES. 163 converted into the same sort of passive substance. The relationship is however distinctly seen in disease, for there are conditions under which secreting cells cease to produce their characteristic secretions, shrivel up and waste, and are at last so changed that some of them might easily be mistaken for a very simple form of non-secerning cell structure. A gland follicle itself, with its included epithelium, is, in the first instance, hut a diverticulum from the duct ; which duct is hut an inflection of the general surface. In the formation both of the duct and the gland follicle epithelium is instrumental. Young cells may gTOW in a dii’ection fi-om the duct, and mid- tiplying in number may produce a httle collection like that seen in the gland follicle, or a long series may result, as in the formation of tubular glands. Eventually the permanent epi- thehum of the secreting part of the gland differs so much m form and action from that of the duct, that had we not watched the evolution of both we should not have been inclined to believe in their common origin. At an early period of development no structural differences can be discerned between the formed material produced by those masses of germinal matter on the surface which are to give rise to epithelial cells and that formed by those beneath which are to take part in the development of fibrous tissues, vessels, nerves, and muscles. But gradually the soft mucus- like formed matter disappears, and tissue exhibiting peculiar structiu’e, and manifesting special properties is slowly formed by the germinal matter. This constitutes the tissue of the epi- thelial cell, or of the subjacent textures, as the case may be. It is the outermost layer of the simple masses of germinal matter of which the germ consists that takes part in the production of cuticular and allied tissues. The process, having commenced, continues as long as life lasts, and the loss of old epithelial cells upon the smface is compensated for by the production of new ones beneath. But a modified form of cuticular tissue may be produced in another way altogether. Where the healing process proceeds over an extensive surface after the removal of a consider- able portion of skin, new cuticle is at last formed. The formation of new cuticular texture does not only spread gradually towards the centre of the space fi-om the intact cuticle at the margin of the wound, but new points of cuticle formation are seen to originate 164 CONTRACTILE TISSUE. as little islands even in the central part. This cuticular tissue must be formed by masses of germinal matter which have de- scended fi’om those of the subjacent connective tissue coi’puscles, or from particles of gei-minal matter descended from white blood corpuscles, of wliich a large number are usually found upon the surface of a healing wound, having escaped with the serum of the blood through the thin walls of the subjacent capillaries.* The fact of the very intimate connection between the epi- thelium and subjacent connective tissue which exists in some cases, and the gradual transition by which in other instances one tissue is seen to pass into the other, lends support to the view that the germinal matter of connective tissue, and pro- bably that of many if not all other tissues may, under certain circumstances, produce a tissue closely allied to simple cuticular textm’e. Some observers have arrived at the conclusion that the epithelial and nervous tissues are continuous — that the finest ramifications of the nerve fibres pass into and are stnicturally connected with the formed material of the epithehal cell. This view will probably turn out to be erroneous, but it shall receive full consideration when the structm'e of nerve texture is described. Contractile Tissue . — One of the most remarkable examples of peculiar structure familiar to us, and one which cannot be at all satisfactorily explained at present, is striped muscle. But we must not conclude that the transverse marlrings are essential to contractile tissues, for they are completely absent in the case of mvoluntary muscular fibre. Wliile, on the other hand, there are certain kinds of fibrous tissue, destitute of contractility, which possess distinct transverse markings. Nor are the strife of muscle seen at an early period of development. They do not make their appearance until contraction of the tissue has repeatedly occurred, but the fact of then- great regularity and constant uniformity in the same species precludes the possibility of these markings being due merely to some accidental variation in the refractive power of the muscular tissue. It is certain they depend upon the occm-rence of important structm-al changes, while the contractile material is in a very soft plastic state. They may be due to the rate of formation of the contractile material, and the rapidity of the successive actions of the nerve cm'rent * “ On the Germinal Matter of the Blood.” Mic. Journal, 1863. NERVE TISSUE. 165 instrumental in exciting contraction : and tlie depth of the contracting portions indicated by the varpng distances between the lines in different cases may he accounted for by the altered rate of performance of the operations above referred to. Nerve Tissue . — It has been generally considered that the tissue of the nerve fibre was peculiar and that its function was in some manner determined by the peculiarity of its structure, or by its chemical composition. Such a view is, however, not supported by facts. F or when we come to examuie the axis cylinder which is undoubtedly the active and really essential part of the nerve, being that w'hich is alone instrumental in transmitting the curi’ent, we find that this filament possesses an exceedingly simple structure, and, at least in some animals looks very like ordinary fibrous tissue. Indeed, if we were shown only a very small piece of an axis cylinder of a frog’s nerve fibre, and some pieces of fibrous tissue of the same shape and size we shoidd not be able with certainty to distinguish one from the other. Can the axis cylinder be regarded as any- thing more than a very elongated band composed of a texture closely allied to white fibrous tissue, but formed of perfectly parallel and continuous strata, not disposed as distinct fibres but nevertheless tearing in the longituchnal direction only? Anatomical observation would justify us in concluchng that if it were possible to replace an axis cylinder by a long filament of ordinary fibrous tissue, we should find that this would conduct the nerve crurent as effectually as the ordinary axis cyhnder itself. We doubt if the axis cylinder is capable of undergoing any remarkable changes in internal arrangement dtuing nerve action, and consider that whatever those changes may be, they are of such a nature that they might occur in other forms of tissue. The peculiarity of the nervous system upon which all its cha- racteristic phenomena depend, is probably not any remarkable arrangement in minute structure, bat simply uninterrupted continuity of conducting tissue. Nor have we reason to tliink that the germinal matter of nerve grows or hves very differently, from other forms of germinal matter. It receives its nutrient material from the same blood and is derived from the same masses of germinal matter winch give origin to other forms. Considermg the characters and arrangement of the germinal matter and its relation to the formed material in all tissues, it 166 NERVE TISSUE. is not unreasonable to conclude that currents, and, perhaps, of the same nature as those discharged by nerve organs, are set free. But perhaps the reason why these do not act in the same manner and cannot, indeed, be rendered evident, is this, that there is no continuous tissue along which the currents could be transmitted in definite directions and no pecuharly constructed apparatus adjacent to them which they could influence. It is probable that very shght differences in the molecular changes, which occur when hving matter dies, determine the form or mode which the force then set free shall assume. Heat, light, electricity, or active movement being manifested according as the vital power operates upon the material particles of the genninal matter which are about to undergo change. But the nature of this action cannot be explained. It must be accepted as an ultimate fact, and the structure and the properties exhibited by tissue must in like manner be referred to the peculiar influence of vital power temporarily associated vflth the particles of living or germmal matter without the agency of which not any kind of tissue can be formed. CHAPTER IV. FIBEOTTS TISSUE. SIMPLE EIBROUS CONNECTITE. — OP CELLS AMD IMTERCELLULAE SUBSTAMTCE. OF THE SO-CALLED TUBE SYSTEM OF CONMECTITE TISSUE. WANDERING CELLS IN CONNECTITE TISSUE. MUCOUS TISSUE OF UMBILICAL COED. VITREOUS HUMOUR OP THE EYE. — CORNEA. — -WHITE FIBROUS TISSUE. LIGAMENTS AND TENDONS. VESSELS AND NERVES OF WHITE FIBROUS TISSUE. REPARATION AND REPRODUCTION. CERTAIN CHANGES OCCURRING IN DISEASE. YELLOW ELASTIC TISSUE. FORMATION. AREOLAE TISSUE. INCREASE OF CONNECTIVE TISSUE AS LIFE ADVANCES. One of the simplest forms of tissue Avhich is most widely dis- tributed among other tissues of man, and the higher vertebrata appears imder the microscope to consist enthely of delicate fibres passing fi-om one point to another. It has been already stated that extremely delicate fibres may be formed by every kind of germinal matter, and that these result from its death. The substance known as fibrin consists of fibres Avhich interlace in all directions and which have been probably formed fi’om matter produced by the white blood corpuscles, p. 123. A white blood corpuscle, a mucus corpuscle, or other kind of germinal matter may move onwards, leaving behind it a trail of newly formed lifeless material consisting of a mucous-like mass of dehcate fibres. See Figs. 79, 80, 81, plate IX. Fibres of fibrin gradually acqume fii-mness by the closer approximation of the material of which they consist, and the gradual expression from its substance of more and more of the fluid existing in relation or combined with it at the time of its origin fi’om the germmal matter. The gradual production of these fibres may be studied under the microscope during the coagulation of a drop of liquor sanguinis, plate V, p. 124, figs. 44, 45, 47. The germ consists, at a very early period, of masses of germinal matter only, but soon a very delicately fibrous formed material makes its appearance, and in this very simple textui-e the formation of the new tissues from the germinal matter proceeds. In the development of muscle, nerve, and most other textm-es a delicately fibrillated matrix may be distinctly 168 SIMPLE FIBROUS CONNECTIVE. demonstrated before any indications of tlie special tissue which is to be produced subsequently, can be found. And even in the fully formed perfect tissue the reinains of this primary and very simple texture mav be discerned. When a wound in the substance of a tissue is repaired, fibrin is fii’st formed from the outer part of the white blood corpuscles. The germinal matter embedded in the meshes of tliis newly formed web of temporary tissue then grows and multiplies, and at length masses are formed from which a firmer and more lasting fibrous tissue results. This is deposited in definite layers, and in a definite direction, while the old temporary fibrin having served its pm-pose is slowly absorbed. The changes referred to have been carefully stuched ui the fibiin deposited from the blood in the repah of a wonnded artery. Some idea of the characters of the coagulum first formed, and the changes which take place m it afterwards may be gained by reference to figs. 82, 83, plate IX.* SIMPLE FIBROUS CONNECTIVE. This very delicate texture, the simplest of all the tissues, is very widely distributed in man and the higher animals. Indeed there is scarcely a part of the body in which traces of it cannot be discerned. From the chcumstance of its existing between the more important structural elements of higher tissues, and connecting them to one another, as well as to other tissues, it has been termed connective tissue. It has been supposed that this texture was designed to give strength and support to more important tissues, but it must be obvious to any one who examines any of the organs in question, that the various struc- tural elements afford the most efficient support to one another, and are not hi need of a special supporting fi-ame-work of any kind. It is indeed very remarkable that such a view should have been entertamed, as it is well kno'wn that at the time when the more elaborate tissue elements are softest, and there- fore most in need of support, that is at an early period of then- development, scarcely a trace of this connective tissue is to be foimd, while on the other hand, when the textures have acquired considerable firmness, and possess resisting power of * “ On tlie repair of Arteries and Veins after injury,” by Henry Lee and Lionel S. Beale. Medico-Cbirurgical Transactions. Yol. L. 1 NOT A SUPPORTING TISSUE. 169 their own, this “ supporthig ” connective tissue exists in very large quantity. The intervening connective, instead of being of advantage to the special elements of the tissue, actually interferes with their action, and its accumulation corresponds with the deterioration of the organ in which it takes place. Old texture differs from young in the greater proportion of its con- nective tissue, which results from changes occurring in the normal structm’e. And in many painful examples of chronic disease of important organs which come under the notice of the physician, the premature decay at a time when all parts of the body ought to be still in an active, vigorous state, is associated with abundance of connective, this being, in fact, the debris of the more important textme which has wasted. It is easy to understand how the connective tissue results during the development of textures in which the permanent type of stnicture is not manifested until several temporary textmes have occupied the place of that which is destined at last to remain. These temporary textures gradually disappear, leaving a small quantity of what we call fibrous connective, and tins collects, in most instances, at the outer part, because the formation of the new tissue takes place in a direction from within outwards. In studying the development of tissues, which consist of collections or bundles of fibres, as for example, muscular fibi’es, this point maybe demonstrated very conclusively. The new fibres origmate in the centre, and great differences in character between the outermost fibres, and those situated further inwards, vdll always be observed. From the first the masses of germmal matter, situated most externally, only pro- duce connective tissue, and the muscle itself resrdts from the deve- lopment of those occupying a more central situation. The same fact is noticed in the development of nerve fibres. The masses of germinal matter, situated at the outer part of the bundle, do not produce true nerve fibres, but from them is formed con- nective tissue only. Up to a certain period the formation of true nerve fibres may have been possible, but a sufficient num- ber of perfect fibres having been developed within, the marginal fibres degenerated, and took the low form of fibi’ous connective. But the nature of this connective, and the mode of its pro- duction, are very conclusively determined by investigating the changes which occur dmlug the development of a gland of higlxly complex structm-e like the kidney. The subject is so 170 OF THE FORMATION OF important that it is worth while to consider the matter some- what in detail. The essential structm’es in the fully formed kidney seem to he these — vessels for conveying the blood, — nerve fibres which govern the calibre, and thus determine the rate of flow of the blood from the arteries into the capillaries, — and epithelial cells which are arranged round the tubes so as to leave a channel by which the materials separated or formed by them may be readily carried away in solution in water. It is probable that these are the only anatomical elements which exist when the renal apparatus first begins to perform its active functions, and the only ones which constitute the simplest form of kidney. But as the growth of the body proceeds, the demand for a more extensive renal apparatus arises, and, as in the case of other organs in vertebrata, the increase must be gradual, and must take place while the organ is actively discharging its functions. The growth of the kidney necessitates a change in the relative position of the individual nerve fibres, vessels, and secreting structure in different parts of the gland, and the pro- gressive development of new elements as extensions from those already existing. The successive changes are not easily traced with accuracy, and it is very difficult to convey in words a clear idea of the phenomena which succeed and as it were over- lap one another. At an early period of development the secreting cells multiply and become arranged so as to form a hollow tube. By their division and subdivision the tube increases in length and cfrcumference, at least during a certain period, in every part of its extent. At the deep or external portion of these cells, adjacent to the vessels, matter is slowly deposited in an insoluble form, and thus a thin membranous boundaiy which corresponds to the outer limit of the futm-e uriniferous tube results, and this becomes extended as the cells grow, while at the same time it is increased in strength by the addition of new matter. Between the lines of masses of germinal matter from which the tubes are developed, and those which take part in the formation of vessels and nerves are a few masses which are not concerned in the formation of any definite structure, but which perhaps take part in the production of a small quantity of intervening substance. The membrane becomes fiu’ther modi- fied by its relation to the nerves and blood-vessels. These were very close to the cells at the earliest periods of development. PLATE IX. Kg. 79. Fig. 80. Lam-nat(=d fibrinous material, shown ip Si, more highly magnified. Showing masses of germinal matter (white blood corpuscles) now elon- gated : and fibrin-like substance, (formed material), which at length assumes the character of fibrous cis- * sue. X 700. p. 163. Section through one of the openings madem an artery of ahorse, three dav-s after puncture. Showing lamiuaced arrangement of fibrinous material which occupied the wound and proJec:ed above the internal surface of the artery. X 40. p. 16S. Fig. 81. Fis. 8'’. “White blood corpuscles (human subject) . with a thread of fihiin (g) being formed from it, X iSOO. p. 167. Mucus from the trachea during life, diameters, p. 167. magnified 700 f Fi£. S4. 5 I'endon from the finger of a child at birth. • The preparation has been altered by teasing and pressure. Prolongations from ''ach mass of geimiual mauer are seen at vaiious points, giving the masses a stellate appearance. These rro- iongaticns are seen to pass into the tissue of the tendon, into which they undergo conversion, X 100. pp. 174. 176. [To face 170. L. S. B.] FIBROUS CONNECTIVE. 171 and a very close relationship between them must be maintained thronghout life or the free action of the gland would be impaired. Moreover, as the gland which already actively per- forms its functions grows, new nerve fibres and new capillaries must be developed arormd the urmiferons tubes. The position which a capillary or an ultimate nerve fibre occupies at an early period -will at a later time be the situation where a bundle of nerve fibres, or small arteries and veins must be placed. The structural changes mvolved in all these alterations are con- siderable. Old capillaries and nerve fibres must be removed as new ones are developed to take then- place, and all the original gland cells will have disappeared probably long before the uriniferons tubes have acquired their fully formed characters. But these structural elements are not completely removed. There vdll remain a small quantity of matter which cannot be taken up by the ordinary processes at work. This is no doubt capable of being removed like every texture in the body, but its complete removal would probably involve the destruction of the gland, while its almost complete removal permits of the continuous development of the latter and does not interfere with its continuous action. The conditions of existence in the case of man and the higher vertebrata, with a few unimportant exceptions only, permit the very gradual but not absolutely complete removal and renovation of tissues. In insects, the state of things is very different, and in thefr textures there is an almost complete absence of connective tissue. The organs and tissues of the larva are entirely re- moved, while new organs and textrues of the imago or perfect insect are laid down afresh and developed ab initio, instead of being built up upon those first formed. Such complete change, however, necessitates a state of existence during which action or frmction remains in complete abeyance. In the pupa or chrysalis period of life, ftmctional activity is reduced to a mini- mum, and nothing is allowed to interfere with the develop- mental and formative processes. The new and more perfect being which is evolved does not probably retain a trace of the structm’e of its earlier and less perfect state. Although the elements of matter in the imago are, of course, those of which the larva and pupa were composed, they have been as com- pletely re-arranged as they would have been had they been 172 CONNECTIVE TISSUE. introduced into the organism of another individual altogether. Not only have the old tissues been utterly destroyed and new ones produced, but in many instances these new ones belong to a totally different type ; and were it not that observation has taught us that they have been really evolved at different periods during the life of one and the self-same individual being, we should have concluded not only that they belonged to different species, but in many cases to species far removed from one another. In vertebrate animals there is not an organ in the adult but retains, not only the form which it assumed at a comparatively early period, but some of the very same tissue which was active in early life remains in an altered but deteriorated state. Every adult organ may be said to contain as it were the imper- fect skeletons of organs which were active at an earlier period of life. This material which slowly accumulates, clogs and perhaps even in the most perfect state of things, slightly inter- feres with the free activity of the organ. If from any inter- ference with the changes this unabsorbed debris accumulates hi undue proportion the action of the organ may be very seriously impafred. It indeed soon grows old, while all the rest of the body may remain yoimg. Its imperfect action deranges other processes of the body, and these react upon it until further action become impossible, and death results. The gradual but conthiuous and regular decay and renovation of an organ is normal in the vertebrate animal. The changes exhibit wonder- ful elasticity within certam limits, according to the demand for functional activity of the organ, but these limits, narrow in some, wide in others, cannot be exceeded vdthout derangement and slow deterioration resulting. This continuous renovation of an organ and accumulation of the skeleton of its earlier periods of existence may, however, he almost suddenly mterrupted. In those changes which lead to the formation of pus the removal of every textm-e is as perfect as during the pupa state of the insect, hut the germinal matter constituting the pus corpuscles has no power to give rise to that which will take part in the development of new tissues, while the germinal matter taking part in the removal of the laiwal tissues dining the pupa state does possess this power, so that when in vertebrata this complete change occins the organ is destroyed, and a new one is never developed in its stead. A part CELLS AND INTERCELLULAR SUBSTANCE. 173 ' of a complex organ may be destroyed and removed, but it cannot be formed anew, so that in man the gradual or sudden destruction of a great part of an organ necessary to life cannot be repaired, although in many cases the patient may adapt himself to the altered state of things and live under the changed conditions. The above considerations afford, I think, an explanation of the formation of the so-called interstitial indefinite connective found in greater or less amount in all organs of all vertebrate animals, and of its increase as age advances. The more regularly, gradually, and perfectly the changes are effected, the smaller will be the proportion formed, and the more slowly will it accumulate. When this is the state of things in all the organs of the body, health and longevity result. The opposite entails disease and too early death. Of Cells and Intercellular Substance . — The connective tissues are supposed to form a class by themselves, and to consist of cells or cell forms embedded in an intercellular substance; and it has been held that the formation of the cells, and the production of the intercellular substance are distinct opera- tions, although it has been proved that in this, as well as in all other textm’es, masses of germinal matter (the so-called cells) existed before any vestige of the intercellular substance was to be demonstrated. The connective tissues include the various forms of connective and fibrous tissues, cartilage, and bone. But the matrix of cartilage, as has been pointed out by one of us, is no more intercellular than the walls of epithelial cells. The relation of the so-called cells to one another, and to the cell wall, or intercellular substance in the two tissues respectively, will be at once understood if we call to mind the fact that the masses of germinal matter produce upon their surfaces the tissue, be it termed matrix, cell wall, or inter- cellular substance. This tissue accumulates between the masses of germinal matter. Even m epithelial textures, at an early period of formation, the formed material does exist as a continuous mass, which occupies the intervals between the several masses of germinal matter just as occurs in adult cartilage and fibrous tissue ; but as growth advances, the por- tion of formed material belonging to each mass separates from its neighbours, and thus “ cells ” of epithelium result. The main difference, therefore, is at once perceived, for in the carti- N 2 174 CONNECTIVE TISSUE. lage each “ cell ” is not marked off from its neighbom-s, but is represented by a mass of germinal matter, including a pro- portion of the so-called matrix, or intercellular substance around it. Some forms of cartilage are, however, really composed of “ cells,” which may be separated from one another just as in epithelium. The distinction, therefore, which has been drawn between different tissues, based upon the presence or absence of “ cells ” in the fully-formed textm-e, cannot be sustained. Dark Fibres in Connective Tissue . — In every foi’m of the simple fibrous connective tissue may be seen certain fibres, some sharp and well defhied, others somewhat ragged and irregular, which are darker and more highly refracting than the rest. — PI. IX, fig. 84. From the cn-cumstance that the mass of the fibrous matter, of which fibrous tissue is composed, becomes perfectly transparent when treated with acetic acid, while these darker fibres are imaltered by this reagent, it has been Fig. 85. " Connective tissue fVora the embryo of .1 pig, after long-continued boiling,” x 850. After Virchow. inferred that two distinct textures exist in intimate relation with one another ; the one being a gelatin-jnelding substance, rendered perfectly transparent and structureless by acetic acid, the other allied to another form of fibrous tissue, the so-called yellow elastic tissue, which is not altered by this reagent. It has been maintained that the fibres exlubiting these different chemical reactions are formed separately, — that the gelatin- yielding fibrous tissue results from the “ fibrillation ” of an JUICE-CONVEYINa CANALS. 175 intercellular substance, while the dark fibres, closely allied to yellow elastic tissue, are supposed to represent the cellular element of connective tissues. In some of the plans adopted for the demonstration of the supposed cellidar element most important textures would be completely destroyed. Thus in fig. 85, taken from Vu’chow, and representing the connective tissue from the embryo pig after long-continued boiling, and supposed to show the connective tissue corpuscles imbedded in then- basis substance, most im- portant textures, like nerves and blood-vessels, as well as the masses of germinal matter, taking part in the production of these, and of the white fibrous element, and of fat cells, and other structures, have been utterly destroyed by the process of preparing the tissue. It is unreasonable to suppose that any- thing can be learnt from examming the pulp of long boiled embryo skin, except the fact that of the many textiu’es entering into its composition all are destroyed except the yellow elastic tissue. By such operations, as long-continued boihng, harden- ing in strong alcohol, drying, and the like, we cannot hope to gain anything but very erroneous ideas concerning the struc- ture, arrangement, and offices of tissue elements. Tube System of Connective Tissue. — Virchow has propounded the doctrine, that the fibres above referred to, and represented in fig. 85, which resist the action of acetic acid, constitute a Fig. 86. ** Elastic networks and fibres from the subcutaneous tissue of the abdomen of a woman.” After Virchow. a a “Large elastic bodies (cell bodies), with numerous anastomosing processes, h b, Dense elastic bands of fibres, on the border of larger meshes, c c, Moderately thick fibres, spirally coiled up at the end. d rpeitdicular section. Cornea rabl p. lf^3. : rnea. X ‘-JI0. [To face p. 132. EADIATINa CELLS. 183 ceils of the cornea. These were discovered by Mr. Toynbee in 1841. They have since been looked upon as peculiar to unde- veloped elastic tissue, and, like those already considered, are supposed to be connected with channels for conveying the nutrient juices. Even Kolliker, who nevertheless inaintams that white fibrous tissue is developed fi’om cells, considers these cells or nuclei to be distinct from the fibrous tissue, and accepts Virchow’s explanation of their office. He remarks : — “ It is probably beyond doubt, that the nutrient flmd, which con- tinually saturates the cornea in large quantity, is chiefly con- ducted and distributed further into the interior by the cells in question.” If this be so, the nutrient flmds must be circulating in channels wliich lie between the fibrous bundles that are to be nourished. On this supposition it is not easy to explain by what process the fluid is made to pass into the innermost parts of the bundles, and by what forces constant interchange of fluid is effected. These so-called radiating cells, the branches of which anas- tomose freely with one another, are the masses of germinal matter of the cornea. They are dhectly concerned in the formation of the proper fibrous tissue of the cornea, and are much more numerous in a given bulk of young, than of fully developed tissue. The arrangement of these bodies is shown in fig. 94 and in fig. 94*, pi. X. The Jluids attracted towards these masses of germinal matter pass through the substance of the fibrous bundles, and thus the mtegrity of the tissue is preserved. They have nothmg in common with yellow elastic tissue, except that, like tins tissue, they resist the action of acetic acid. See observations on page 177. In the adult corneal tissue fluid may be forced into the spaces in which the germinal matter and its prolongations are situated, and may be forced fi’oin these between the lamellated fibres. In this Avay the “ corneal tubes,” which can be readily injected Avith mercury, are produced.* * Tlie corneal tubes may be injected in the cornea of the ox by proceeding as follows : after the muscles aud tlieir attachments have been carefully dissected from the globe, the epithelium and remains of the conjunctiva are to be scraped from the corneal surface, the eye being held firmly in the hand and pressed moderately. A large needle or sharp pointed knife may now be introduced into the corneal tissue at the side, and carried a little way into its substance and then horizontally for about a 184 WHITE FIBROUS TISSUE. It is doubtful if any actual tubes or cavities exist in the cornea during life, but by the arrangement above indicated, the corneal tissue is rendered much more permeable to fluids than ordinary flbrous tissue is. Fig. 94. Corneal corpuscles, and nerve fibres; Cornea of the green tree frog. The former are seen to be unconnected with the nerve fibres. X S50. The nerves ramify in the proper substance of the cornea amongst the ramifications of their cells, but are not connected with them. The relation of the germinal matter of the corneal corpuscles to the nerve fibres is represented in fig. 94. WHITE FIBROUS TISSUE. Tendons, ligaments, and fasciae, owe their fiiurmess and unyieldnrg properties to the white fibrous tissue of which they are composed. This white fibrous tissue is veiy vddely distributed, but it difiers materially in character in different parts. The three structures above named are all composed of white fibrous tissue, having well-marked characters. Cylindrical bundles, consisting of finer fibres varying somewhat in diameter, are bound together with indefinite or simple fibrous connective tissue, to constitute quarter of an inch, so as to enter the lamellate d tissue, care being taken not to perforate the cornea. A small globule of mercury may now be introduced into the channel which has been made, with the aid of a glass tube drawn off to a capillary oriSce. A knife is to be applied to the aperture of the wound made in the cornea in such a way as to prevent the escape of the globrde of mercury which at the same time is to be firmly pressed into the comeal tissue. It soon spreads and may then be made to pass to every part of the cornea. Some other forms of fibrous tissue may be injected by the same plan, but the spaces filled are not so regularly arranged as those in the cornea. PHYSICAL PROPERTIES. 185 the tendon, ligament, or fascia. The few vessels and nerves distributed to this tissue, pass amongst these bundles, which in ligaments and tendons run parallel to one another, so that in a transverse section different parcels are seen packed together, with the vessels and nerves hi the slight intervals between them — figs. 95, 96. In fascia, the bundles cross one another at differe,nt angles and form flattened bands. Physical Properties . — White fibrous tissue is inelastic, and, under ordinary cncumstances, inextensihle ; though it does admit of being somewhat stretched by the influence of long-continued and slowly-acting force, as is seen occasionally when an effusion of fluid has taken place into an articular cavity, protected by a fii-m, fibrous capsular ligament, or where a tumour has slowly grovTi under a fascia. Its force of cohesion is the most valuable and characteristic quality of the white fibrous tissue, and to this its various important uses are chiefly due. Mascagni cal- culates the force requisite to ruptm’e the tendo Achhlis as equal to 1,000 pounds’ weight. Instances are constantly seen where muscles are torn or bones fractured, while the tendons or ligaments, through wliich the force has acted, have escaped ; thus the malleoli are often dragged ofi’ by twists of the foot acting on those processes of bone through the lateral ligaments of the joint. It is entirely devoid of contractility or irritability; and its sensibility is very low, so much so that tendons hanging Fig. 95, Pig. 96, Transverse section of tendon, showing bundles of fibrous tissue divided transversely with vessels and nerves in the intervals, x SO. Longitudinal section of tendon. Bundles di- vided longitudinally to show direction of fibril- lated structure, x 80. 186 LIGAMENTS AND TENDONS. out of a wound have been cut without the patient being aware of it. The flexibility of fibrous tissue is owing to its containing a small proportion of water. A tendon, ligament, or fibrous membrane, will dry readily ; it then becomes bard and rigid ; it resists the putrefactive process when not kept moist, and even then putrefies less readily than the softer textures. Acetic acid causes it to swell up, instantly removes its peculiar appearance of wavy fibres, and displays the remains of the masses of germinal matter concerned iu its development. Gelatine may be extracted in considerable quantity from white fibrous tissue by boiling. Of the different Forms of White Fibrous Tissue. — A. Ligaments. — Ligaments are connected with joints. They pass in deter- minate directions from one bone to another, and serve to limit certain movements of the joint, while they permit others. They therefore, constitute an extremely important part of the articular mechanism in preserving the integrity of the joint in its various movements. — There are three principal kinds of articular liga- ments : — 1. Funicular, rounded cords of white fibrous tissue, of which we may give as examples the external lateral hgament of the knee-joiut, the perpendicular ligament of the ankle-joint, &c. : 2. Fascicular, flattened bands, more or less expanded ; ex. internal lateral ligament of the knee-joint, lateral ligaments of the elbow-joint, anterior and posterior ligaments of the wrist- jomt, and, indeed, the great majority of ligaments m the body: 3. Capsular; these are barrel-shaped expansions, attached by their extremities around the margm of the articular surfaces composmg the joint, and forming a complete but a loose invest- ment to it. The capsular ligament is .highly developed in the enarthrodial or ball-and-socket joiut, and permits the very free movements required. Good examples are found in the only two perfect examples of that form of articulation, namely, the shoulder and hip j omts. B. Tendons . — Tendons serve to attach muscle to bone, or some other part of the sclerous system. We may enumerate thi-ee varieties of tendon, as regards form: — 1. Funicular, e.g. long tendon of the biceps cubiti; 2. Fascicular, short tendon of the same muscle, and most of the tendons of the body; 3. Apo- neurotic, tenchnous expansions, sometimes of considerable extent. MEMBRANOUS FIBROUS TISSUE. 187 and very tisefi;! in protecting tlie walls of cavities. The ten- dons of the abdominal muscles afford good examples of this variety. The tendons are for the most part implanted by separate fascicles into distinct depressions in the bones, and are also closely incorporated with the periosteum ; so that in maceration, when the latter is separated, it becomes easy to remove the tendons. In some birds whose tendons are black, the peri- osteum is black also ; and in the human subject we may often see the tendinous fibres coutimied on the surface of the peri- osteum, as a shining silvery layer, following the primitive direction of the tendinous fibres, from which they were derived ; a marked example of this may be seen on the sternum in fi-ont of which the tendinous fibres of the opposite pectoral muscles meet and decussate, and thus form the superficial layer of the periosteum covering that bone. The length of the tendons is beautifully adapted to the quantity of contractile fibre required to perform a certain movement ; thus, in the biceps cubiti, were the whole length between the scapula and radius occupied by muscular fibre, there would be a great waste of that contractile tissue, as there would be much more than is wanted to produce the required motion ; tendon is, therefore, made to take the place of the superfluous muscle : in this way we may explain the differences in length of the tendons even in the same limb. C. Membranous .- — In the form of an expanded membrane white fibrous tissue is used to cover, protect, and support various parts. Under such chcumstances we often find that it not only forms an external covering to them, but that it sends in pro- cesses or septa, which separate certain subdivisions or smaller parts. Thus, the fascia lata of the thigh not only invests the muscles of the thigh, but sends in processes which pass down to the periosteum, and separate the several muscles from each other ; and the dura mater of the cranium sends in processes by which certain portions of the encephalon are separated from one another. Structure of Tendon . — When the areolar tissue has been dissected off, the surface of the fibrous tissue exhibits a beau- tiful silvery white aspect, and seems composed of bundles of fibres, which in some are arranged parallel to each other ; in others are disposed on different planes and interlace or cross in 0 188 TENDON. different directions. On placing a veiy thin piece of the fihrons tissue under a high power of the microscope, we observe what may be considered the characteristic feature of this textru’e. The piece under examination, fig. 97, pi. XI., seems to be composed of a leash of exceedingly delicate fibi-filae, running parallel to one another, and if not stretched, disposed to take a wavy course, like a skein of silk. But, on more accui’ate inspec- tion, it is found impossible to distinguish tlneads of a deter- mmate size ; these seem, indeed, to be of various sizes according to the degree of splitting to which the whole has been submitted, and many are to be seen so very mumte as at first almost to elude the eye. In other parts the mass splits up into membra- nous rather than filiform fi-agments ; so that it would appear incorrect to describe this tissue as a bimdle of tlmeads. It is rather a mass with longitudinal parallel streaks (many of which are creasings), and which has a tendency to slit up almost ad infinitum in the longitudinal dh-ection. The correctness of this view is further shown by the action of acetic acid, winch obliterates, for the most part, all appearance of fibrillEe, and causes it to swell up as an enthe mass. But the ordmary fibril- lated structure reappears if the acid be carefully neutralized. Tendon is generally subjected to examination after ha^■ing been chied, or partially chied, and then remoistened with fiifid, but it has been found that these processes caimot be carried out without some considerable alteration in the characters of the tissue bemg produced. With the exception of fig. 97, in which the germinal matter is not shown, the specimens represented in plate XI have been prepared without any desiccation at all. They have been soaked in carmine solution, and after- wards mounted hr glycerme, according to the method ah-eady described in page 60. If a thin longitudinal section of tendon be examined, numerous narrow elongated bodies connected together by narrower lines, and arranged parallel to each other, and nearly equichstant, vuU be observed tlu-oughout the fibrous sribstance of the tendon. These are the “nucleated fibres of the tendon,” or the parallel nucleated fibres, the kern-fasern of the Gei’man writers. — Figs. 98 to 102, pi. XI. The parallel, wavy, and dehcately fibrillated matter between them is the white fibrous tissue of the tendon, the so-called matrix or intercellular substance, which is considered to be formed iudependently of, and NUCLEAR FIBRES. 189 not to be connected with, the nuclei. The proportion which the “ nuclear fibres” bears to the fibrous substance is different at different periods of development. If we examine the tendon of a foetus, that fi’om a yormg hadividual, and one from an adult of the same species, we shall find that the “ nuclear fibres” are nearer together in the foetus than in the young animal, and closer together in the latter than in the adult. In other words, as the tendon grows, the fibrous tissue or intercelhdar substance urcreases in proportion to the nuclear fibres ; or in a given bulk of tendon, the nuclear fibres are much more nume- rous in embryonic tissue than in the same amount of that of the adult. — Fig. 101, a, 6, pi. XI. If the tendon be stretched longitudinally, the nuclei become narrower and appear as mere lines. — -Fig. 100, c, d, e. On the other hand, if the structru’e be stretched laterally, the mass of germinal matter assumes an oval form, and the extension may be carried so far as to cause the masses to be wider fi-om side to side than fi-om end to end. — Fig. 100, /, pi. XI. The germinal matter thus extended forms but an exceedingly thin layer. The cir- cumference is not so darkly colomed as the central part. Pass- ing in a longitudmal chrection are a number of lines (or rather the particles of which the germmal matter is composed, exhibit a hnear ai-rangement) which run parallel with the fibres of the tendon, and these lines in the germinal matter may be seen, if a very high power be used, to be continued into the tendon, as im- perfectly formed tendinous tissue.— Fig. 84, pl.IX,page 170. The direction of the fibres of the tendon is indicated by the arrange- ment of the particles of the germinal matter. These points which are of importance with reference to the natm-e of the so-caUed “ nuclear fibres” can be demonstrated very distinctly in specimens of tendon which have been prepared in the manner described, and afterwards subjected to stretching and pressm-e without being previously dried. The appearances just referred to lead to the inference that the “nuclei” are continuous in all cases with the fibrous tissue ot ■the tendon, and this may be positively proved to be the case in certain specimens, for the “nucleus” maybe separated with fibrous tissue still connected with it. — Figs. 89, 91, pi. X, page 182 ; figs. 98, 99, 100, pi. XI. The fibrous tissue (intercellular substance) nearest to the nuclei or masses of germinal matter, is that 0 2 190 RELATION OF GERMINAL MATTER which was most recently formed; while that which is most distant is the oldest portion of the tendinous structure. Con- tinuous with the particles of germinal matter is imperfectly formed fibrous tissue. As the germinal matter is exceedingly soft, and undergoes changes soon after death, and is destroyed by the action of water, it is not surprisiug that the continuity between the germinal matter and the firm fibrous tissue of the tendon should not have been generally recognized ; but if care be taken to colour and harden the germinal matter, tliis con- tinuity is made out very readily in every kind of fibrous tissue. If tendon well prepared be carefully torn up vfith needles, very delicate bundles may be separated ; and it is not uncommon to find the oval masses of germinal matter with portions of wliite fibrous tissue projecting from either extremity. From the fact that these oval bodies are colom’ed by car- mine like the germinal matter of other tissues, and the fibrous tissue of the tendon is in direct continuity vfitli them, we can- not but conclude that they are the masses of germinal matter of the tendon, and bear the same relation to the fibrous tissue that the germinal matter bears to the formed material of other tissues. That tills view is correct vdll be admitted, if allied tissues prepared in precisely the same manner be subim'tted to examma- tion. As is well known, white fibrous tissue is m many cases immediately continuous with cartilage and bone. The matrix or intercellular substance of all these tissues is continuous, and if a section be made at the point where the fibrous tissue of tendon joins the cartilage or bone, one tissue can be traced into the other. The fibrous appearance of the first will be seen to gradually give place to the almost homogeneous or slightly granular tissue characteristic of the last. In fig, 129, pi. XY, page 230, is represented a very thin section through the tendo Achilhs and 08 calcis (in that part which yet remains cartilaginous) of a kitten soon after bhth. As the cartilage grows the masses of germinal matter divide, and the two portions at once separate from one another. In the tendon, however, the two masses resultmg from division remain connected together by a thin line of germinal matter. Between the cartilage and the tendon is a layer which eventually becomes the periosteum. The stellate character of the masses of germinal matter in this situa- tion is very distinct (under b in the drawing). Fig. 97. Fig. 98. PLATE XI. Fig. 99. Fig. 100. Tendou. Fini^er; old man, age 74. Sbow^lng different appearances produced in tbe oval masses of germinal matter (nuclei) by sti’eLcbing in different directions, a appearance of prolongation of germinal matter, stretched longitudinally (nuclear flbie) , under a power of 1700 diameters b, appearance of fine fibre of yellow elastic tissue’under the same power, c. fibre stretched in a lougxtudinal directi, n d. appearance generally observed in unsLrctched tendon, e. fibre sligbtlv stretched latei'ally. f. appearance produced when the fibre was stretched laterally and subjected lo pressure, x 700. p ISO. Fig. 101. a h Tendon. X,itcen at birth, x ^15- Tendon. Touug cat. X 215. Showing germinal matter and formed material (intercellular sub- stance ot'auLhors) of tendon at different stages of development, p. 130. Fig. 102, ” Infiammaticn " of tendon. Shew- ing great increase in the size of the masses of germinal matter. Por- bions are detached from time to time and make their way into the fibrous material, growing at its expense and destrtjying it' x 215. p. 197. [To face p. IfO, L. S. B.l TO FIBBOUS TISSUE OP TENDON. 191 A very different interpretation of these appearances has, however, been given by some authorities. The masses of germinal matter in tendon and allied tissues have been re- garded by Virchow as connective tissue corpuscles, “hmde- gewehskorperchen,” and he states that they are connected together by tubes. In a longitudinal section he admits that nothing like the stellate arrangement, seen m a thin trans- verse section, is observable. If an attempt is made to cut a transverse section of tendon, the stellate bodies are undoubtedly seen, but it is impossible to obtain a very thin transverse section of tendon with these in their natural position. In trying to do so, short pieces of tendon and the mcluded nuclei are removed, with then’ prolongations of germinal matter and imperfectly developed formed material which resists the action of acetic acid, and being altered in relative position by the pressure to which the specimen is subjected, appear like stellate cells or corpuscles with radiatmg processes. In properly pre- pared specimens, however, the continuity of structure between the nuclei or masses of germinal matter, imperfectly developed formed material, and fully formed fibrous tissue, can be demon- strated. In some specimens of young tendon these pi’olongations from the masses of germmal matter {cells or nuclei) are well seen, and their commmiications are tolerably numerous. The processes are distinct enough in some places, but most of them gradually become lost among the wavy fibres with which all are connected, and of which they are but the early stage. Although they somewhat resemble fibres of yellow elastic tissue in their general appearance and in their power of resisting the action of acetic acid, they are not of this nature ; their outline is irre- gular, and when examined with very high powers they have a granular appearance, which is very different from the sharp out- line and homogeneous appearance of true yellow elastic tissue. Moreover, it must, too, be borne in mind that the appearance so remarkably distinct m certain specimens is not constant. It is not seen hi a specimen of adult tendon where fibres of yellow elastic tissue are found, nor in that of a kitten ; and hi the fascia of the frog, fig. 99, pi. XI, there is no more iiichcatioii of such an arrangement than there is in cartilage. In some specimens of the tendon of the child which have been stretched and 192 ENCIRCLING FIBRES. pressed, the appearance of stellate cells and communicating tubes is most distinct, hut that it depends upon an alteration produced in the germuial matter, and iipon the displacement and tearing away of some of the young tissue coimected -ndth them is sufficiently proved, — by the appearance in question being produced by pressure, by its absence in parts of the specimen not subjected to pressure, by the great variation of the appearance when it is seen, and by its enthe absence in certain specimens. The oval nuclei and intervening lines may be regarded as spaces and tubes in tendon some time after death, but in living tendon, and in tendon shortly after its removal from the dead body, the oval nuclei are composed of living gemiinal matter which extends from one to the other in the form of a very narrow line. Some time after death this germmal matter becomes broken down, and there remain oval spaces and narrow tubes containing fluid and the products of disintegration of the germinal matter. Encircling Fibres . — Encircling the bundles of some forms of wliite fibrous tissue are to be seen, more especially after treat- ment by acetic acid, sharply dethied fibres like those of yellow elastic tissue. — Fig. 104, pi. XII. It has been too hastily assiuned that these elastic fibres are m connexion with the so-called nuclei and nuclear fibres (germinal matter) in the substance of the tissue. The existence of these fibres is rmdoubted, but they are not in sufficient number to be considered as essential con- stituents of the tissue, nor are they to be detected in all forms of white fibrous tissue. They vund round the bundles. By great patience we may occasionally succeed in fiLnding a mass of germinal matter connected with some of these fibres, but when this is so, it is very small, and quite distinct fr‘om the masses amongst the white fibrous tissue. The delicate fibres of which the yellow elastic tissue is composed form a lax network on the sm-face of the bundles of white fibrous tissue. This is well seen in fig. 104, pi. XII. But what is the nature of these encfrcling fibres of yellow elasti<; tissue which do not penetrate hito the substance of the fibrous bundles ? If the tendon of man, or any small animal be examined while development is going on, the vessels of which liave been well and carefully injected according to the direc- DETi^LOPJilENT OF TENDON. 193 tions given in pag'e 62, the true explanation will, we think, at once occui- to the observer, who will probably be much sur- prised at the great vascularity of the texture. He vdll find numerous capillary vessels arranged around the fibrous brmdles, as in the case of the elementary fibres of muscle. As the tendon gradually becomes fully developed, these vessels waste, and, as it seems to ns, the delicate encncling fibres which have been described by so many authors alone remain to mark the channels in which blood once fi-eely cnculated.* Sketch of the Changes occuring during the Development of Tendon and Allied Tissues . — Regarding the oval nuclei as the masses of germinal matter, and the fibrous stnicture wliich is in all cases connected vdth these, as the formed material, it is not difficult to account for the actual appearances observed in the different forms of fibrous tissue. At an early period of development these tissues like all others are composed almost entnely of germinal matter. The small masses increase, divide and subdi- vide in the soft imperfectly developed formed material which exists between them at this early period. In some tissues the masses of germinal matter soon become quite detached and entirely separated fi-om each other, in which case the tissrre ■will consist of formed material with the separate masses of germinal matter embedded in it, as cartilage. In others the masses of ger- minal matter divide in one particular direction, and separation of the resulting masses occm-s laterally, while longitudinally they still remam intimately connected vdth one another. As the tissue advances ui age, and the masses of germinal matter become separated from each, other by gradually increasing distances, the formed material accmmdates in parallel layers between the oval masses of germinal matter. These are con- nected by distmct lines of germinal matter and imperfectly developed formed material, and laterally, by finer and less ob'ffions lines produced in the same manner. In those cases in * I have demonstrated in vei’y many tissues the fact that fibres having the reac- tion of yellow elastic fibres result from the wasting of vessels and fine nerve fibres. In the bladder and mesentery of a starved frog, the process of degeneration may be actually observed step by step, and in the serous pericardium and peritoneum of a very young mammahan animal positive evidence of a similar change may be obtained. The capillaries gradually ti-ansmit less and less blood, and as they contract in diameter the walls become more distinct. Slowly the cavity becomes completely obliterated and an apparently solid cord of elastic tissue alone remains. — (L. S. B.) 194 VESSELS OF TENDON. wliich the expansion of the tissue takes place equally in all directions, or equally in length, breadth, and depth, and the masses of germinal matter do not become detached, the tissue will consist of a matrix in which stellate masses of germinal matter are embedded. The radiating processes gradually become finer and finer as the tissue advances in age, until at last they quite disappear or leave narrow lines of imperfectly formed tissue which differs in chemical characters from that external to it, and resists the action of acetic acid like yellow elastic tissue. In tissues which are fundamentally composed of white fibrous tissue the most different appearances may be produced, according to the directions in which the structm-e expands, the rapidity of its growth, and the influence of stretching or pressure. In the various forms of fibrous tissue in the human organism, wide differences are observ^ed, but hi some of the corresponding tissues of the lower animals the differences are so great, that if only theh anatomical characters in the fully developed state were studied, one would hardly suppose they were fibrous tissue at all. Vessels . — AVhite fibrous tissue when fully formed probably undei’goes little change. It contains few vessels, but is never- theless more vascular than is generally supposed. The majority of the capillaries of tendon under ordmary circumstances only transmit liquor sanguinis, ivith a very few blood corpuscles, and many appear as mere solid threads, and under ordinary circumstances no blood passes through them. If, however, the tissue becomes inflamed, the blood-vessels are ob\-ious enough, and the tissue in this condition would be regarded as highly vascmlar. The alteration, however, is due, not to the rapid development of new vessels, but only to the passage of blood through many which before transmitted none. AA Idle tendon is undergoing development, it is highly vascular, indeed the vessels appear to be as numerous as they are in many other- tissues. As development advances, many being no longer- required, shrivel, and as has been already explained, dehcate lines of elastic tissrre rernairr in the sitirations in which they once ramified. Alarry forms of fibrous tissue are almost destitute of vessels in the adult state, undergo scarcely any charrge, arrd require for their rrutritiorr a very small quantity of nrrtrient pabuluirr. NERVES OF TENDON. 195 Nerves . — It is generally stated that white fibrous tissue is destitute of nerves, but in every form numerous nerves which, however, form meshes of considerable diameter are to be detected. In the dm-a mater, in the perichondiium of cartilage, and the periosteum of bone, in the cornea, and some other fibroiis textures, nerves are exceedingly numerous, and perform important offices. In tendon, however, the greater number of the delicate nerve fibres present are those which belong to the capillary vessels, to the small arteries, and to the veins. The first are often seen in considerable number, and not rmfre- quently a delicate fibre is observed running on either side of the capillary vessel, connected with one another by transverse branches at short intervals. Reparation and Reproduction . — When a solution of continuity takes place in wliite fibrous tissue, it readily heals by the inter- position of a new substance, every way sunilar to the original tissue, excepting that it wants its peculiar glistening aspect, and is softer, more bulky, and transparent.* In this process the changes are analogous to those described in page 193. When the tendon is chvided, the cut ends separate, and the space between them is occupied by blood and lymph. This contracts somewhat, and thus the divided ends of the tendon are to some extent drawn towards one another. In the coagulum, thus formed, numerous masses of germinal matter are formed, which separate from one another, while soft formed material is produced by them. This gradually undergoes condensation, and at last assiunes the characters of orduiary tendon. The changes which take place during the formation of this new tendinous tissue resemble in all important particulars those which occur in the development of the tendon itself at an early period of life — so simple is this texture, that it may in fact be developed at any period of life, and in almost any part of the body. Certcdn changes occurring in White Fibrous Tissue in Disease . — In health the normal changes occurrmg in fibrous tissues seem to consist of the gradual increase in the quantity of the fibrous formed material, and the condensation of that which has been already produced. The fibrous tissues of the adidt and of aged persons contain a higher percentage of solid matter than those of the child. * We ascertained tliis in a case of a divided tendo Achilles. — T. & B. 1843. 196 CHANGES IN DISEASE. The changes above refen’ed to occur very slowly, and it is probable that very slight, if any, absolute disintegration and complete removal of white and yellow fibrous tissue takes place during life in the healthy state. These tissues are supplied with a very small proportion of nutrient matter, and the ger- minal matter is very slowly converted into fibrous tissue. But the fibrous material to retain its healthy state must be per- meated in every part by fluids, which slowdy pass to and fi-om the masses of germinal matter. In certam cases, fatty matters are precipitated from the fluids amongst the fibrous tissue, or result fi-om the degeneration of the imperfectly developed foi-med material around the masses of germinal matter, and in con- sequence the tissue deteriorates. In the low form of soft fibrous tissue in the umbilical cord, and in the placenta, this change uivariably occurs towards the termination of the period of gestation. Very numeroiis oil globules and pigment gramdes are deposited amongst the fibres and precipitated amongst the particles of germinal matte i'. No such appearances are obseiwed in the early months of pregnancy when the formation of tissue is actively taking place. In the higher forms of fibrous tissue corresponchng changes are observed in advanced age — changes which are so constant that we are almost entitled to consider them as occurring normally ; but in persons of healthy and vigorous constitution they are postponed to a much later period of life than in those whose nutrient processes have been im- paired by disease and modified by the altered composition of the nutrient fluid. We have many opportunities of obserwng such a change in the case of the cornea. We have observed the arcus senilis wide and distinct hi a man of forty years of age, while in the cornea of an old lady of upw'ards of ninety- eight the change had only just commenced. Whether“these changes result from the power of the ger- minal or liwng matter beiog impafi-ed, or fi-om an alteration in the composition of the fliuds which are transmitted to it, cannot be discussed here ; Mr. Edwin Canton has sho-wn that con-e- sponding changes occin- in many other tissues of the body. That such tissue changes do not in all cases lead to fatal results is no more than would be expected, but this does not in any measure diminish then- significance. Arcus senihs never occurs at the age of forty in strong constitutions, and it is very seldom YELLOW ELASTIC TISSUE. 197 fully developed in persons wlio have lived very carefully, or Avho have weak stomachs and are dyspeptic, and have therefore been compelled to be careful, at the age of fifty or sixty. Of Suppuration and Sloughing . — When the vitality of the nuclei of fibrous textures is destroyed, either from their not being supplied with nutrient matter, or in consequence of being bathed with fluid of an abnormal nature, the fibrous tissue becomes softened, and undergoes decomposition, and the dead portion is detached — in fact, sloughing takes place. If the germinal matter (nuclei, connective tissue corpuscles) be sup- plied with an increased quantity of nutrient matter, owing to the formed material, fibrous tissue, being rendered more per- meable or otherwise modified, tliei-e is at first a tendency to the formation of new elementary parts (germinal matter and connective tissue), but if the change once commenced increases, the germinal matter multiplies so rapidly that no formed material is produced. — Fig. 102, pi. XI., p. 190. There is not time for the formation of any fibrous tissue whatever — in truth, the process of suppm’ation becomes established. Those soft connective tissues which contain the greatest number of nuclei (masses of germinal matter), and are most freely supplied with blood- vessels, and receive a large proportion of nutrient matter, are most liable to suppuration. The process of suppuration is, on the other hand, often arrested by a living fibrous tissue, as tendon or fascia. This fibrous tissue, resisting the tendency of the pus corpuscles to grow at its expense, retains its vitality, while softer and more succulent textures are destroyed. YELLOW ELASTIC TISSUE.. Yellow elastic tissue differs from the white fibrous element in anatomical characters as well as in physical and chemical pro- perties. Of a yellowish colour, very flexible, generally, com- posed of fibres vary mg much in diameter, it is eminently elastic, and it retains its elastic power after removal fi’om the body. In man it exists in the fascicular, funicular, and mcnibranous forms, and is often disposed in bundles of fibres covered by a thin sheath of areolar tissue, which lilrewise sinks in among its fibres. This tissue may be preserved for many years in preservative fluids without its important physical property 198 YELIiOW ELASTIC TISSUE of elasticity being in any way impaired. The action of this tissue is often antagonized by muscles, and the delicate move- ments of the ponderous head of the ruminant are effected by the contraction of the flexor muscles of the neck, which over- come the elevating action of the elastic ligamentum nuchm. In the following situations true yellow elastic tissue is found with well-marked characters : Ligamentum nuchce : ligamenta subjiava : chordce vocales : many ligaments about the larynx. The internal lateral ligament of the lower jaiv, the stylo-hyoid ligament, and the transversalis fascia of the abdomen, are also, in a great measure, composed of it. The suspensory ligament of the penis also consists of this tissue, and a modified form is found in the elastic coat of arteries, ui the trachea and bronchial tubes and pulmonary tissue. Fibres of elastic tissue occur in con- nection with the subcutaneous, submucous, and subserous areolar tissue ; and fibres generally considered to be of the same nature exist in connection with tendon and almost all forms of white fibrous tissue. Among the lower animals it is very extensively used for mechanical purposes as a soft elastic pad or buffer, or as strong elastic cords like the retracting ligament of the claw' of feline animals, and the ligamentum nuchce of quadrupeds. The true elastic tissue is in every case connected with, and developed from, nuclei (bioj)lasts), but there are many fibres, ordinarily regarded as yellow elastic fibres, which are but the remains of tissues (nerves and vessels) which w^ere active at an earlier period of life. &e.e page 214. Although elasticity is the property which is universally characteristic of yellow elastic tissue, this structure does not exhibit an anatomical arrangement which is constant. As there are many different forms of white fibrous tissue distingnished from each other by the arrangement and general characters of the texture, and by the manner hi wdiich it w'as produced, so also we find a diversity in structure, arrangement, and mode of production of the elastic tissues. Under the microscope ordinaiy elastic tissue is found to consist of fibres, which are romid m some, flattened hi other specimens. These fibres are ver\' variable in diameter, usually from 5 - 5 ^ 0 -g- to , oo^oo 'o inch hi diameter. In one bundle there are fibres varying much in age, the youngest as a scarcely ^dsible line, the oldest of considerable thickness. The fibres bifurcate, or even cUvide into thi-ee ; and OF THE COAT OP ARTERIES. 199 the sum of tlie diameter of the branches considerably exceeds the diameter of the trunk. Filaments of elastic tissue anasto- mose freely with each other. They are prone to break under manipulation, and the broken extremities are abrupt and dis- posed to curl up. — Fig. 107, pi. XII. ; when many of these broken ends exist together in the same piece, they give it a very peculiar and characteristic appearance, which renders it almost impossible to mistake this tissue. The parallel fibres of the ligamentum nuchse, figs. 107, 108, pi. XII., of the vocal cords, of the ligamenta subflava, and other pure elastic ligaments, differ -widely from the lax network of long fine fibres of elastic tissue present in the areolar tissue beneath the skin and mucous Fig. 109. Fig. 110. Finely fibrous layer of the longitudinal tissue of the aorta of Coarsely fibrous layer ofthe longitudinal fibrous the horse, x 200. tissue ofthe aorta of the horse. X200, membranes, fig. 115, p. 205, among muscular fibres, connected with nerve fibres, &c. Both these forms are totally unlike the thin delicate longitudinal fibrous layer which lies just beneath the epithelium of an artery, fig. 109, and this again differs in important chai'acters from the elastic tissue beneath, fig. 110. The circular fibrous coat of the larger arteries contains a number of very coarse fibres, and in this situation is often seen Fig. 111. Fig. 112. A portion of the circular fibrous tissue ofthe aorta of A portion of the circular fibrous coat of an artery, the horse, to show the reticulation formed by the inter- showing the penniform branching of the large rods lacement of its fibres, x 200. of elastic fibrous tissue, each large rod giving origin to multitudes of small interlacing fibres, x 200. a form of tissue which can scarcely be termed fibrous. The elastic structure seems to form a very coarse network which is 200 LIGAMENTUM NUCH®. often sj^read out in a membranous form with numerous spaces or holes hi it, figs. Ill, 112. Mr. Quekett found that the large fibres of the hgamentum nuchm of the giraffe, exliibited transverse markings equidistant fi’om each other, almost like striped muscle. These marks are not to be seen in all the fibres, and they are most distinct in the oldest. They do not extend quite across the fibre, but appear to arise fi'om a shrhiking of the central part, which causes it to break up transversely into smaller segunents, fig. 113. Eig. 113. Fig. 114. Large fibres of elastic tissue. Flakes from a large artery found in the stools, scarcely altered by with well-developed transverse digestion.— Natural size. See figs. 105, 106, pi. XII. markings. Ligamentum nuchse. Giraffe. Xl30. It is remarkable that fibres of elastic tissue from the sheep and ox, which have passed thi’ough the alimentary canal, without having undergone digestion, should sometimes exhibit transverse marldngs as distinct as those ordinarily observed in the fibres of the ligamentum nuchce of the gu-affe. In fig. 114 some flakes of yellow elastic tissue from an artery of a sheep or pig which had been passed by the bowels, are represented of the natural size. Fragments showing the structm'e are seen in figs. 105 and 106, pi. XII. Vessels and nerves are to be demonstrated in some forms of adult yellow elastic tissue, but even in the ligamentum nuchrn they are very few in number. The yellow elastic tissue of the arterial coats seems to be noiu'ished by imbibition only, and is completely destitute of nutrient vessels. The nerves for the most part belong to the capillary vessels, except in cases where muscular fibres are associated with the yeUow elastic tissue, as FORMATION OP YELLOW ELASTIC TISSUE. 201 in the arteries, when nnmerons fine nerves are seen to ramify amongst the former fibres. This may be proved by examining the larger arteries of any small animal (frog, particularly the hyla, mouse, rat, rabbit. — L. S. B.) Formation of Yellow Elastic Tissue. — With regard to the for- mation of yeUow elastic tissue, different views are entertahied. In his “Manual,” published in 1860, and in former echtions, Prof Kolliker states, that these fibres are formed from cells, and he has given a drawing of “ stellate formative cells of fine elastic fibres from the tendo Achillis (!) of a newly-born child.” He says, that “ in all parts of the embryo wliicli afterwards con- tain elastic tissue, pectdiar fusiform or stellate and sharply- pointed cells can be recognized, which, by their coalescence, produce long fibres or networks.* The fibres not unfrequently persist in this condition of stellate anastomosing cells, or con- nective tissue corpuscles (Vhchow), as e.g., in the tendons and the cornea, in ligaments and ligamentous discs, in the corium, in mucous membranes,” &c. Kolliker agrees therefore with Virchow, in considering that these cells and fibres correspond to the canalicular systems of bones and teeth, and he proposes to call them pZasm-cells, and tlieh’ processes pZasm-tubes, because they are supposed to convey plasm or nutrient juices. In 1861, however. Prof. Kolliker completely abandoned his former views as to the fibres being formed from cells, and now maintains that the cells or nuclei which exist in such number at an early period of development have notlung whatever to do with the formation of the elastic fibres. He differs from Virchow as to the relation of the elastic fibres to the cells, and, so far from believing that they are continuous, maintains that the yellow elastic tissue represents intercellular substa?ice. In the development of the ligamentum nuclise, he says that the cells seen at an early period of development assist in the formation of an interstitial substance, “ from which by independent dif- ferentiation both the connective tissue and the elastic fibrous networks proceed.” By this term “ differentiation,” it is implied * It may be remarted here tbat cells never coalesce during the development of tissue. Cells divide, and tbe subdivisions separate from each other — a fibre in many cases connecting them. This fibre of course increases in length as the cells become separated farther and farther from each other. Cells neither coalesce, nor do tubes or processes grow away from them and coalesce with tubes or processes from neigh- bouring cells, as has been asserted very positively by some authorities. 202 STEUCTURE AND FORMATION that from an interstitial substance originally homogeneous, con- nective tissue arid yellow elastic tissue separate, or are deposited, or ‘ formify ’ (Owen), just as from a clear solution composed of two or more substances, may separate definite compounds ex- hildting totally different forms and chemical properties. There is not, however, the slightest analogy between the two cases, and it is not remarkable that a view so strangely at variance with facts should have received little attention. It has been already shown that the apparent fibres (Virchow’s tubes) which resist the action of acetic acid and are embedded in the substance of the tendon, are not composed of elastic fibres at all, but merely consist of imperfectly fonned tendon which, like other tissues at an early period of formation, resists the action of acetic acid. The formation of these apparent fibres is therefore to be accounted for without supposing, that like the gelatine-yielding fibrous 1 issue in which they lie, they result fi'om the “ diff'erentiation ” of an mtercellular substance. It is not possible, nor would it be advantageous, to consider fully this long and very complicated question ; but with regard to a form of true elastic tissue, one of us (L. S. B.) has remarked : — 1. That in the adult ligamentum nuchse (sheep), masses of germinal matter (nuclei), are continuous vfith the material of which the yellow elastic tissue is composed, fig. 108, pi. XII. 2. Tliat these nuclei bear to the thick elastic fibres precisely the same relation which the “ nuclei ” bear to the white fibrous tissue of the adult tendon. 3. That in the hgamenturn nuchm of the lamb and young sheep, fibres of different ages and sizes may be obtained. The mode of development of the fibres may, in fact, be studied as well as in an embryonic tissue. 4. That in all cases the elastic substance results fi-om the gradual conversion of germinal matter into this structm-e. In the ligamentum nuchse and other parts where yellow elastic tissue is formed in quantity, the tissue may be traced into the masses of germmal matter. Elastic tissue never results from the differentiation of an intercellular substance. The genninal matter passes gradually uito very soft, and this last into the fully-formed, tissue. The oldest portion of the tissue is that which is most distant from the germinal matter, as hi other cases. PLATS XII. Fi^. 103. Portion of a fibre of yellow elastic tissue. Liga* meutum nuciise, lamb. Tlae mass of germinal mat- ter is moving in tlie direction of tlie arrow. It lias been said that this tissue is formed without the agency of nuclei or cells (germinal matter), but a great, number of these bodies can be demonstrated in properly prepared specimens, p J02. F i^. 105. "yellow elastic fibres ; a portion, probably, of an artery Passed by tliebowel. Showingtraneverse markings like those of the lig. nuchse of the gii’affe. Fig. 113. p. 200. X 215. p. loo: Lig. 107. c Yellow fibrous tissue. Showing the curly and l-'ianched disposition of the fibres, their definite outline and abrupt mode of fracture. At e. the structure is not disturbed as an the rest of the spscimen. x 320. p. 191. Fibres of yellow elastic tissue encix’cling bundles of white fibrous tissue.' From beneath the mucous membrane of the ileum. Human subject, adult. X 215. p. 192. Fi^. 106. Fibi'es ofyellow elastic tissue. ligamentum nuchse, sheep. Showing masses or germinal matter not hitherto demonstrated, and its relation to the formed mateiial of the tissue The new matter is deposited upon the surface of each fibre, as shown in Fig. 103. pp. 199, 202.' X 700 p. 202. Yellow elastic tissue. Showing the cracks or transverse markings. Passed by bowel, x 550, P ^00. [To face p. £0C. k.K L. S. B. OF YELLOW ELASTIC TISSUE. 203 5. What appears to be an ultimate fibre of such a tissue as the lig'amentum nuchse is not really so. It may be readily torn into very much finer fibres. In the case of young fibres, the nuclei are observed to be -wider than the fibres themselves. After the elastic tissue has been formed, it gradually loses water and contracts, and the diameter of the fibre must necessarily be less than that of the nucleus up to a certain period of its growth. As the fibre grows in thickness, however, the “ nucleus” is seen at its side just as in tendon. One of the thick fibres of the liga- mentum nuchm with “nucleus,” therefore, corresponds to one of the small bundles of fibrillated tissue of tendon with its “ nucleus.” Compare figs. 103, 108, pi. XIL, -with fig. 100, pi. XI. Fibres of Elastic Tissue ivhicli are not formed directly from Nuclei . — We have ah-eady seen that fibres closely resembling elastic tissue are embedded in a delicate transparent matrix with undoubted nerve fibres, and we have been able to trace fibres in various transitional conditions, from the nerve fibre to a structure resembling a fibre of yellow elastic tissue. There are, in mucous membranes, in the papillse of touch and taste, outside the sarcolemma of muscle, and in other textures, fine fibres Avhich form networks closely resembling the fibres of elastic tissue in general appearance, which are not formed fi’om cells or nuclei, but which ’must be regarded as the remains of tissues, especially nerve fibres and vessels Avhich were functionally active at an earlier period of life.* In yellow fibrous tissue, fi-om many situations, prolongations of germinal matter may be demonstrated as in other textures, but we have completely failed to prove the tubular character either of the fine or coarse yellow elastic fibres. Over and over again the nuclei amongst the fibres of yellow elastic tissue have been stained with carmuie, as shown in figs. 103, 108, pi. XII, while not a single fibre exhibited the slightest alteration. Instead of the nuclei leading towards the central part of the fibre, they are invariably seen to be connected with the surface. Not a trace of germinal matter (nucleus) is to be found in the substance of any fibre of elastic tissue. It is therefore not probable that these fibres at any period of then development really consist of tubes for the transmission of nutrient juices. * On the distribution of the nerve fibres to the mucous membrane of the epiglottis of man. — “Ai-cbives of Medicine,” No. XII, page 250. P 204 AREOLAR TISSUE. The portions of transparent material extending from the masses of germinal matter consist in fact of imperfectly for’med tissue. Similar extensions from oval nuclei may be seen in some forms of voluntary and uivoluntary muscle. In some of the large elementary fasciciili of the voluntary muscles of the limbs of the old frog, they form quite a firm network, everywhere in the substance of the muscular tissue. This network has been regarded by some as constituthig a system of nutrient tubes, by which the several nuclei are comiected together as m tendon. By others the facts have been interpreted in a veiy different manner. These same lines have been regarded as nerve fibres, ramifyhig amongst the sarcous particles, with many of which they come into chrect contact. Both views are, however, erro- neous and untenable. The lines in question merely show that as the muscular fibre gradually increased in size, the masses of germinal matter which were originally continuous did not become completely detached from one anofher as the distance betAveen them increased. We do not, however, consider that the facts allow us to regard them as of importance otherwise. In chemical constitution, elastic tissue differs remarkably from the white fibrous tissue. It is unaffected by the weaker acids, or by boiling, and will resist putrefaction, and preserve its elasticity dui’ing a very long period. By very prolonged boiling, however, a muiute quantity of a substance, soluble in water, which has been called teroxide of protein, and a trace of gelatine, derived from the areolar tissue and vessels, which always penetrate spaiingly among its fibres, and cannot be separated by dissection, may be extracted fr'om it. AREOLAR TISSUE. In almost all parts of the body there exists a tissue consist- ing partly of the white and partly of yellow fibrous element. This texture alloAvs great fi-eedom of movement between different parts of an organ, and permits one textm'e to glide for a certam distance over another. It is a compoimd tissue, and has been called fr-om its arrangement areolar {areola a small open place); but was formerly known as cellular ov filamentous tissue. Microscopic Characters. — When a fi-agment of well-developed areolar tissue is examined, it presents an mextricable interlace- ment of tortuous and wavy threads intersecting one another in MICROSOOPIO CHARACTERS. 205 every possible direction. Tliese are of two kinds. The first are chiefly in the form of bands of very unequal thickness, and inelastic. Numerous streaks are visible in them, not invariably parallel with the border, though taking a general longitudmal direction. These streaks, like the bands themselves, have a wavy character, but they are rendered straight by being stretched. The streaks seem to be marks depending upon longitudinal creasing, rather than the result of a true separation of the texture into actual threads. It is impossible by any art to tear up the band of fibrous tissue into filaments of a deter- minate size, although it manifests a decided tendency to tear lengthwise. The larger of these bands are often as wide as of an inch ; they branch, or unite with others, here and Fig. 115 . Fig. 116 . The two elements of Areolartissne.in their natural relations to one another;— c. The white fibrous element, with cell-nuclei, I, sparingly visible on it. b. The yellow fibrous element, shewing the branching or anastomosing character of its fibrilise. c. Fi- brillae of the yellow element, far finer than the rest, but having a similar curly character- d. Nucleolated cell-nuclei, often seen apparently loose.— From the areolar tissue under the pectoral muscle, magnified 820 diameters. Development of the Areolar tissue (white fibrous element):— e. Nucleated cells, of a rounded form. /. ff. h. The same, elongated in different degrees, and branching. At h, the elongated extremities have joined others, and are already assuming a distinctly fibrous character. — After Schwann. there. The smaller ones are often too minute to be visible except with a good instrument. These are the white fibrous element. Fig. 115«. P 2 206 WHITE AND YELLOW ELEMENT The others are long, shigle, elastic, branched filaments, 'udth a dark, decided border, and disposed to curl when not put on the stretch. Tliese interlace with the others, and sometimes coil spirally round the bundles of white fibrous tissue, but appear to have no continuity of substance with them. They are for the most part about the of an inch in diameter ; hut we often see, in the same specimen, others of much greater thickness. These form the yellow fibrous element {Wbh). These two tissues, as already mentioned, may be most easily discriminated by the addition of a di-op of dilute acetic acid, which renders the first clear and transparent without producing any alteration in the other. After the action of the acid upon the bands of white fibrous tissue, there often remains in them an appearance of more or less wavy transverse lines at pretty equal distances, remotely resemblhig those on the fibre of striped muscle. These are found to be very distinct, clear, and regular, and situated within short distances of one another in the fibrous tissue from the subcutaneous areolar tissue of the human embryo. In the earliest period at which the areolar tissue can be examined, it consists of masses of germinal matter having offsets which are connected with one another. The formed material produced by these is at fii’st homogeneous ; the longi- tudinal streaks and the wavy character appear subsequently. We have observed frequently among the threads of areolar tissue taken from adult subjects a number of corpuscles, fig. 115d, either isolated or havuig very dehcate prolongations among the neighbouring threads. These seem with great probability to be either advancing or receding stages of the tissue (T. and B. 1843). By the endless crossing and tunning of the microscopic filaments, and of fasciculi of them, among one another, a web of amazing intricacy results, of which the hiterstices are most irregular in size and shape, and all necessaiily communicate with one another. This is well seen by forcibly filling the tissue with air or water in any region. In the living body this is very ob^dous in oedema and anasarca, and in traumatic em- physema, as hi the remarkable case related by Dr. W. Himter in his celebrated paper (Med. Obs. and Inquu'. vol. ii. p. 17), where the whole body was blown up so tensely as to resemble a drum. OF AREOLAR TISSUE. 207 The interstices are not, however, cavities possessed of definite limits, because they are open on all sides, and ultimately con- stituted out of a mass of tangled tlireads. The meshes which are formed are disposed so as to constitute secondary cavities, Fig. 117. Portion of Areolar tissue, inflated and dried, shewing the general character of its larger meshes. Each lamina and filament here represented contains numerous smaller ones matted together by the mode of prepara- tion.— Magnified 20 diameters. having a somewhat determinate shape and size, and which are visible to the naked eye. These sometimes contain fat, and may be admirably studied in most parts of the subcutaneous tissue. They communicate fi’eely, as the smaller interstices do, their walls being everywhere cribriform, and capable of giving passage to ah- or fluids. Some forms of connective tissue are represented in plate XIII. In fig. 119 is a drawing from a specimen of connective tissue covering one of the voluntary muscles of the hyla or green tree frog. The capillary vessels with their fine nerve fibres and the networks of fine nerve fibres distributed to the muscular fibres are well seen. The masses of germmal matter (nuclei) of the nerves are not connected in any way with those belonging to the connective tissue. The three figures 118, 119, and 120, in this plate should be attentively studied with the aid of the explanations beneath. The areolar tissue is the most extensively diffused of all the tissues of the body, and its chief purpose seems to be that of connecting together other tissues hr such a way as to permit a greater or less fi-eedom of motion between them. To do this, it is 208 AREOLAR TISSUE placed in tlieir interstices, and is more or less lax, more or less abundant, according to the particular exigency of the part. This form of areolar tissue, at least in all the larger annuals, invests the exterior of the muscles iu a profusion proportioned to the extent to which these organs move as a whole upon neighbouring parts, of which the best examples may be seen, between the great muscles of the extremities ; between these and their enveloping fascim (not their fasciee of origin) ; under the occipito-frontalis muscle and its tendon; and in the upper eyelids. The areolar tissue is also present in immense quantities under the skin of most parts of the body, and especially where great mobility of the integument is required, either as a protec- tion to deeper organs agamst external violence, or to facilitate the various movements of the frame. Such are the regions of tlie abdomen, and of several of the articulations, and the eyelids. Around internal organs which change their form, size, or position in the routine of then- functions, and which are wholly or partially without a free surface, as the pharynx, oesophagus, lumbar colon, bladder, &c., this tissue is abundant, and its filaments so long, tortuous, and laxly interwoven, as to admit of a ready and extensive motion on the neighbomiug viscera. This tissue likewise forms a layer lying under the mucous and the serous membranes in almost every situation ; though presentiug great variations of quantity and denseness, it renders the movements of such parts easy. It also closely invests the exterior of every gland and parenchymatous organ, and enters more or less abundantly into its inner recesses, along with its vessels, nerves, and absorbents : but there is no doubt that it has been supposed to have a much gi'eater share in the Formation of this numerous class of organs than an ultimate anatomical analysis of them, conducted with carefid precision, wiU at all wari’ant. — (T. & B. 1843.) In all these cases it is a more or less copious attendant on the vessels ; but wherever, either fi-oin the intricacy of the interlacement of the capillaiies with the other essential elements of the particular organ, or the greater strength of these elements themselves, the firm contextm-e of the whole is provided for, wliile little or no motion is requhed between its parts, this interstitial filamentary tissue wfil be found to be PLATE XIII. Eig. 118. Simple fibrous connective tissue from tlie subperitonial connective tissue of a kitten two days old. Two fibres of yellow elastic tissue are seen. The propoixion of germinal matter is very considerable. The manner in which the masses separate and form the intervening fibrous tissue is well shown X 2 I 0 p. *20.. Fig. 119. a Connective tissue covering part of the mylohyoid muscle of the hyla or greeu tiec irog. a. CapiUai’y vessels, with their nerve-fibres. 6. Bundles of fine dark-bordered nerve fibres, from which fine pale nerve fibres may be traced to the capillaries, and to their distribution in the connective tissue, where they form networks of exceedingly fine but nevertheless compoityid fibres. This drawing shows the arrangement of neives in voluntary muscle ; the muscular fibres having been removed, the course of the nerves can be readily traced. Magnified 70C diameters and reduced to 110. p 207. Fig. 120. Connective tissue. From the submucous aieoiar tissue .^duli human auujcct. Inemasses of germinal matter taking part in the formation of tbe yellow elastic tissue, as well as those concerned in the producticn of ihe white fibrous element, are well seen, x ”00. p, 207. [To face p. 205. IN THE MAMMA ANT) LIVER. 209 confined to the larger blood-vessels, and to the surface of the natural subdivisions of the organ. For the present, it may be sufiicient to illustrate this remark by contrasting two important glands, in reference to this point. The human liver is well screened fi-om injury by its position ; it is liable to no change of bulk ; it consists through- out of a continuous and close network of capillaries, the inter- stices of which are filled by the secreting cells. The lobules resulting from the distribution of the vessels and ducts blend together at numerous points, and have no motion on one another. Here the areolar tissue is in small quantity, and is almost limited to the larger ramifications of the vessels and ducts. The mamma, on the other hand, is, by its situation, peculiarly exposed to external injury. It is broken up into numerous subdivisions, Avhich move with the utmost freedom on one another, and it is, moreover, liable to great temporary alterations of bulk. In this important gland not only is there a common investment of peculiar density, but an exti’aordmary abundance of areolar tissue disseminated throughout its interior. Thus, this tissue, so widely spread tlmoughout the body, whether it serve the purpose of an investment to large segments or masses, under the form of a membrane, streugthenuig and protecting them, and escorting their vessels and other com- ponents into and from their substance, or as a web of union between the simplest elements of their organization, is to be regarded as rather taking a subordinate or ministering share in the constitution of the frame, than as being of primary impor- tance in itself. It is a connecting medium, that allows of separation between what it binds together ; and it accomplishes this double purpose in a manner suited to the necessities of diverse parts, by a variety so simple in the number, intx'icacy, and closeness of its threads, as to be worthy of the highest admiration, while it is wholly inimitable by art. The great value of areolar tissue in facilitating the motion of parts between which it is situate, is shown by the effects of inflammation or other diseases which injure its physical proper- ties. It is well known that when the subcutaneous areolar tissue is the seat of phlegmonous mflammation, the movements of the part affected are stiff and painful, or altogether impeded, because the subjacent muscles cannot move freely by reason of 210 INCEEASE OF AKEOLAK TISSUE the loss of elasticity in the areolar tissue. When this tissue becomes mclurated by an effusion of coagulable material, the movements of the parts adjacent are similarly impaired. Where great elasticity is required, the yellow element preponderates ; while the white fibrous element abounds in parts demanding tenacity and power of resistance. In all cases the openness of the network is proportioned to the extent of mobility requhed. Where the meshes are small, the threads composing them branch and anastomose with one another vdth much greater frequency. The texture of the cutis affords the most characteristic example of this condition. Physical Properties . — These have oidy been studied hithei’to in those situations where the tissue exists in great ahimdance, as in the subcutaneous fascia, the sheaths of muscles, &c. It has here a whitish hue, especially when steeped in water. It is extensible in all directions, and is very elastic, returning to its original chsposition after stretching. In many situations it contains numerous fibres of unstriped or involuntary muscle, passing in dift'erent dhections, which give to it the property of contractility, and in some of the lower animals voluntary muscular fibres are associated vdth it. These are very remark- ably developed in the snout of the pig and in the nose of the mole, and are found in great number amongst the areolar tissue, beneath the loose parts of the skin of many other smaller animals frat, mouse, mole). Nerve fibres are abundantly dis- tributed in it, and its capillary vessels are more numerous than those of tendon. This tissue, like many other soft solids, contains a large quantity of liquid, by which the filaments are kept moist and their physical properties maintamed in a normal state. A morbid increase of this fiuid in the subcutaneous areolar tissue occasions the condition called oedema and anasarca, which may be known by the skin pitting. Under the pressure of the finger, the fluid is cbiven into the sm-rounding areolas or spaces, and a pit is made, but after the pressure is withdrawn the fluid retmiis slowly and the pit, or depression, disappears. hen dried, areolar tissue becomes hard and transparent, but resumes its former state if placed ui water. It undergoes the putrefac- tive process very slowly. It yields gelatin by boiling, but this substaoce is derived from the white fibrous element only. AS AGE ADVANCES. 211 Areolar tissue is in most cases associated with a certain proportion of adipose tissue, which will be described in chapter VII. In the following situations, however, we find areolar tissue without any traces of the adipose texture. Beneath the skin of the eyelids, in the median line of the abdomen, beneath the epicranial aponeui’osis. The areolar tissue of the scrotum and penis is also destitute of adipose tissue. It has been supposed that the nutrition of the areolar tissue, like that of the white fibrous tissue, is conducted through the intervention of tubes composed of yellow elastic tissue, but this question has been already referred to in page 203, and need not be further considered in this place. Of the increase of Connective Tissue as Age advances . — The consideration of this subject of areolar or connective tissue has been much complicated by the chcumstance that the areolar tissue just described, which is developed as a special structure for definite purposes, the fibrous connective referred to at the commencement of this chapter, and the connective tissue which is formed after the various organs and tissues are fully developed, have been included together under one head, as if they were all of the same nature, designed for similar purposes, and formed in the same way. It must be clear from what has been already stated that, although these textures resemble one another m some characters, they are not produced under the same cir- cumstances, nor do they originate in the same manner. They also exhibit many remarkable differences in structure which rr;quire careful consideration. Of these three forms, the last has not yet been considered at all ; we therefore propose to refer to it in this place. Con- nective tissue appears to result in adult life from the decay of various textures, and the proportion increases as the indi- vidual advances in age. The change may be stuched in many situations ; for example, beneath the abundant plexus of dark- bordered and fine nerve fibres distributed to the mucous mem- brane covermg the epiglottis, are numerous parallel fibres cross- ing and recrossing one another, which exhibit the reaction and general characters of yellow elastic tissue. These are found with numerous undoubt(;d nerve fibres ; amongst them are numerous delicate cords and bands of wavy tissue, like the cords of white fibrous tissue already referred to. Similar appear- 212 FORMATION OF CERTAIN ances have been observed in certain of the papillae ot the human skin and tongue, and hi other situations where plexuses of nerve fibres and vessels are abundant. In the beautiful papilla of the tongue of the hyla the structures in question are very distinct.* By alterations occurring in nerves and capillary vessels, fibres like the yellow elastic fibres of connective tissue result. The fact has been demonstrated in many different situations and in different animals, as man, the mouse, the cat, frog, and some others. The actual alteration of neiwe fibres into fibrous tissue has been very carefidly studied in many localities. In the human organism the sole difficulty of following out the distribu- tion of the nerves arises fi-om the abundance of the connective tissue about them, and the difficulty mcreases as age advances. Fibrous tissue also forms the residue of many other struc- tm-es besides nerves and vessels ; in fact, the variety which we are now considering is composed of the remains of various tissues which cannot be entirely removed by absorption. The connective tissue between the ultimate follicles of glands, that which surrounds vessels and nerves, and the fibrous tissue of which the so-called capsrde of certain organs, liver, kidney, spleen, &c., are all iu part or entirely of this natm-e. No wonder that in man, whose tissues pass thi-ough so many phases before they reach maturity, and in whom such active changes continually occur after this period, there should be a large amount of such a texture. This tissue, which is absent in the embryo at an early period, exists in very small quantity in the young child, but the proportion gradually increases as age advances. In small animals there is less than there is m large animals, and in yomig animals there is less than in old animals. In creatures of the simplest organization, whose tissues are, so to say, embryonic throughout the whole period of their ex- istence, there is none. In all the higher animals whose textures uninterruptedly pass without cessation through many stages before they attain their perfect form, there is a large quantity. This form of connective tissue also results in the com'se of certain degenerative processes occmTing in higher tissues in disease. In various glandular organs which have undergone * “New Observations upon the Minute Anatomy of the Papillte of the Frog's Tongue.” — Phil. Trans. June, 1864. kinds of areolar tissue. 213 degeneration, a form of fibrous tissue remains behind. In cirrhosis of the liver, the fibrous matter which is present results not merely from the effusion and fibrillation of lymph, but is the remains of degenerated vessels, nerves, capillaries, ducts, and secreting tubes. In livers in this condition, properly pre- pared for investigation, vessels and slirunken secreting struc- ture can always be demonstrated in the substance of the so- called “fibrous tissue” (L.S.B.).* The same remarks also apply to the kidney in certam cases of disease, and to other organs. It is not to be wondered at, therefore, that this indefinite and unimportant connective material should have been made to play so very important a part in modern pathology. But if we are not mistaken, future observers will be much astonished at the rapid spread and general acceptance of the connective tissue doctrines. Connective tissue has been regarded as the actual seat of the active changes of inflammation and various forms of degeneration. It is supposed to become hypertrophied and then to contract, and by thus compressing glandular tissues to cause them to waste and bring about their destruction. We cannot, however, subscribe to these views, for careful observa- tion compels us to conclude that in many forms of inflammation the connective tissue is passive, while the phenomena which have been wrongly attributed to it are mainly due to the presence of particles of germinal matter which have been detached from the white blood corpuscles, and have passed through the vascular walls into the meshes of the connective tissue, where they have grown and multiplied very quickly. These, and not the connective tissue corpuscles, are the bodies from which, m many instances, those collections of granular cells or corpuscles, pus corpuscles, and allied bodies, familiar to all who have studied the alterations occurring in tissues during the early stages of inflammation, originate. After the lapse of some little time, the germinal matter of the connective tissue corpuscles, as Avell as that of adjacent tissues, nerves, and vessels, participates in the changes, and in consequence of being freely supplied with nutrient matter, all these masses of germinal matter increase, divide and subdivide, and at length produce pus-corpuscles,f which do not result exclusively from the connective tissue * “Archives of Medicine,” vol. i, page II9. + “ On the Germinal Matter of the Blood,” Microscopical Journal, 1863. 214 CORD-LIKE FIBRES OF corpuscles or from white blood corpuscles only, but may be formed by any germinal matter wbicb is very actively grovdng, and is tbe seat of increased nutrition. Cord-like Fibres of Connective Tissue . — There are certain cord- like fibres in different locabties in which we are able to study the mode of production of certain appearances which are ob- seiwed in connection with some specimens of fibrous tissue of the higher animals, pi. XIV., fig. 121. The peculiarity refen-ed to is this, that elongated fibres of a structure resembling elastic tissue seem to be embedded in a mass of white fibrous tissue. Many of these elastic fibres are connected together, and here and there nuclei are found. Often two branches seem to diverge fi’om a nucleus, and the fibres vary much in diameter. Fig. 104, pi. XII ; fig. 122, pi. XIV. In several specimens of these cord-like fibres connected with the arteries, from the abdominal cavity of the fi'og, the following points may be observed : — A bundle of nerve fibres is perhaps seen running in the external coat of an artery. Some of the fibres leav^e the large trunk of the nerve and imn in the central part of a fibrous cord, wliich is continuous with the areolar coat of the artery. A portion of one of these cords with most distinct nerve fibres may be seen in one part of a specimen, and hr another, a transition may be traced from most undoubted nerve fibres to the very narrow branching elastic- like fibres just alluded to (figs. 121, 122, pi. XIV). These fibres are not altered by acetic acid, but by careful examination it is clearly proved that they may be split up into still finer fibres if they are not really composed of several delicate fibres collected together. They are not, therefore, merely fibres of yelloAV elastic tissiie. Some of the finest of these cord-like fibres of connective tissue consist of a transparent matrix ui wliich two or three nerve fibres are embedded. The transparent tissue has been considered to be the so-called tubular membrane of the neiwe fibre, but the term is inappropriate, hiasmuch as the structure is of considerable depth and is not membranous. In some cases, several ganglion cells which were once connected with nerves, have wasted, and their remains, with those of the nerves proceeding fi-om them, may be detected in one of these cord- like fibres of connective tissue. It seems to us, therefore, that PLATE XIV. Pig. 121. Cctmeccive tissue forming a network of rounded cords continuous witti tti? areolar coat of a small artery. From tlie abdominal cavity of a frog, A part of the muscalar coat of the artery ia shown at a. A nerve is seen at 6 running in the external areolar coat. At c the bundle of nerve fibres are seen to divide X 130. p. 211. Fig. T22. Small piece of one of the cords represented in the upper part of Pig. 121 at c. Several nerve fibres are seen, and in the lower part of the drawing some very fine fibres, prcbably altered nerve fibres, are shown Ate another portion of a true but very fine nerve fibre is represented. From a portion of one of the finest cords in Pig. 121, Nuclei with branching fibres are seen at "• 'XLlBFV,Ry ’> -s./- _ ! J ;• ■ ■; j- 4 -! OF BOIfE OR OSSEOUS TISSUE. — CHEMICAL COMPOSITION. — COMPACT TISSUE AND CANCELLATED STRUCTURE. — OF LITING AND DEAD BONE. AN ELEMENTARY PART OF BONE. OF THE LACUNA AND CAN ALICULI.— FORMATION OF LACUNiE AND CANALICULI. CANA- LICULI NOT PROCESSES OF A CELL. ULTIMATE STRUCTURE OF OSSEOUS TISSUE. VESSELS OF BONE : RELATION TO OSSEOUS TISSUE. — HAVERSIAN SYSTEMS AND RODS. LAMELLA. — HAVER- SIAN CANALS AND SPACES. DR. SHARPEY’s PERFORATING FIBRES- PERIOSTEUM AND MEDULLARY MEMBRANE. MEDULLA OR MAR- ROW OP BONE. — MYELOID CELLS. NERVES OF BONE. DEVELOP- MENT OF BONE.- — GROWTH OF A LONG BONE. REPAIR OF BONE. GROWTH OF GERMINAL MATTER OR BIOPLASM OF BONE. IN- FLAMMATION OF BONE. CARIES. NECROSIS, Bone clifFers from every other texture -which has yet been brought under notice, in the important character that the formed material, matrix, or soft tissue, is impregnated with calcareous salts, which are intimately incorporated with it. A very firm unyielding tissue thus results, which, however, possesses a certain degree of elasticity, and although hard and of great strength, is by no means brittle. It often withstands violent shocks without fi-actm'e, and being for the most part covered -with soft tissues is in a measure protected ; for the skeleton (bony or cartilaginous) of the higher animals, is in- ternal; it is clothed by the muscles and other soft parts. The fii’st example of this aivangement is met with in the cephalo- podous mollusks, in which certain cartilagmous plates are enclosed in the body of the animal, protecting certain parts of the nervous system. The skeleton of the lowest organized fishes, although much more extensive, is soft and yieldhig, and is placed but little above that of the animals just referred to. It is composed of cartilage,, which, however, in arrangement of its several parts, approaches the bony skeleton of the higher classes. Bone is the substance employed to form the internal skeleton of the osseous fishes, of reptiles, bhds, and mammalia. It R 236 COMPOSITION OF BONE. forms organs of support, or levers for motion, or it encloses cavities, affording protection to soft tissues and to organs of vital importance. In some members of the vertebrate series, bone is found associated -with various tissues, as the skin, ten- don, and certain forms of fibrous tissue, as the sclerotic coat of the eye. To a superficial examination, bone presents the follovdng properties ; hardness, density, a whitish colom-, opacity. An examination of its physical constitution vdll explain these characters. Bone contains less water than most other tissues in the body ; and exposure to ah, even for a short time, removes much of the fluid by evaporation ; to this, in part, may be attributed its hardness. It is easy to prove that bone consists of soft organic tissue, exhibiting structure, and hard calcareous matter deposited in its substance. These may be separated by a very simple process. The soft organic matter may be obtained by steeping a bone for some time in dilute hydrochloric acid (one part of acid to three of Avater), for this acid dissolves the calcareous salts, and leaves the tissue of the bone. The decalcified tissue is so soft, that a long bone treated in this Avay may be bent hi any direction, or even tied in a knot. Yet every eminence, eA^ery minute canal, and even the slightest hiequalities of the surface are as distinctly marked as they AA'ere before the action of the acid. Upon the addition of excess of ammonia to the acid solution, the calcareous salts maybe precipitated in an insoluble form, and by applyhig appropriate tests, phosphates of lime and magnesia, a little carbonate of lime, with traces of fluoride of O ' calcium, may be detected. Again, the calcareous salts of the bone may be made eAudent by another process Avhich causes the destruction of tlie organic matter. If a bone be subjected to a red heat hi a crucible, it becomes charred and black ; but if kept for some time at this high temperature, exposed to the air, the carbon is gradually burnt off, escaphig as carbonic acid, AA-hile the calcareous salts remain behind in a pui-e state. If the process is conducted AAdth care, altliough the bone slninks a little, its form is un- unaitered, and er’ery eminence and every hole is as distinct as in the recent bone, or in the bone treated A\rith acid ; but the cohesion between the earthy particles is extremeh' slight, so EARTHY MATTERS OF BONE. 237 that the least touch will destroy the continuity of the texture ; a fact which obviously points to the animal matter as affording to bone its strength of cohesion. Bone may also be deprived of its animal matter by long- contmued boiling, under strong pressure, in a Papin’s digester. The animal matter is extracted, in combination with water, in the form of gelatine; and the weight of the quantity which may thus be obtained will; owing to this union with water, exceed by three or four times that of the bone itself. We subjoin the following process, by which the qualitative analysis of the inorganic matter of bone may be readily effected : — The earthy matters are best examined by treatmg a portion of burnt bone with nitric acid, diluted with from four to six times its bulk of water ; brisk effervescence ensues, proving the presence of carbonic acid. Filter the acid liquid after diluting it with water, and add solution of caustic ammonia as long as the precipitate at first formed continues to be redissolved by agitation ; then add solution of acetate of lead till it no longer occasions any precipitate. The dense white precipitate tlius produced consists of phosphate of lead, which melts before the blow-pipe, and on cooling assumes its characteristic crystalline structure. Through the solution, filtered from the phosphate of lead, pass a stream of sulphuretted hydrogen to remove the excess of lead ; warm the liquid, to drive off the superfluous gas, and filter : then neutralize by ammonia, and add oxalate of ammonia as long as any precipitate occurs ; abundance of oxalate of lime will fall as a white powder. Evaporate the filtered liquid to chyness ; ignite the residue, and wash with hot water ; the magnesia will be left behind in a pure form. We shall see that in the formation of bone, the produc- tion of the soft tissue is one process, and the precipitation of lime salts from the fluid which permeates it, and their incor- poration with the soft matrix, another p>rocess. The first cannot be brought about except by vital actions. The last is due to chemical changes, and can be, to a certain extent, imitated arti- ficially. Soft bone tissue is formed in certain instances, but in consequence of the secondary process of calcification not having been completed, it remains perfectly soft and useless for the the purposes for which bone is wanted. In the formation and R 2 238 ANIMAL AND EARTHY MATTER, growth of this tissue, we can therefore define with great pre- cision the results of the vital processes, and distinguish these from the effects of the purely physico-chemical changes. A certain proportion between the organic and inorganic constituents of bone is necessary to the due maintenance of its physical properties. To the earthy part it owes its hardness, its density, its little flexibility ; but it is equally necessary for these properties that the animal portion shall be healthy, and in proper quantity ; for the cohesion of the particles of the former is secured entirely by it. A due proportion of the animal part gives bone a certain degree of elasticity ; and, were it not for the earthy matter, bones would be exceedingly flexible, as may be shown in a bone deprived of its calcareous matter by acid. Hence old bones, in which the animal matter is less abundant, as well as perhaps defective in quality, are more brittle than young ones, and the bones of old persons are more liable to fi’acture. But in the yoimg, in whom the organic l^rocesses are active, and whose animal matter is fully adequate in quantity and quality to the wants of the system, the bones possess their due degree of flexibility, and hence in them frac- tures are less frequent ; the cohesive force of the bones being sometimes so considerable, that they ■will bend to a great degree before yielding. The following table from Schreger illustrates the relative proportions of the two constituents, at three periods of life, iu 100 parts of bone : — chnd. Adult. Old. Animal matter . . 47-20 20-18 12-2 Earthy matter 48-48 74-84 84-1 or it may be ‘stated in general terms, that in the child the earthy matter forms nearly one-half the weight of the bone, in the adult is is equal to four-fifths, and in the old subject to seven-eighths ; a conclusion agreeing in the main with that drawn from the analyses of Davy, Bostock, Hatchett, and others. It had long been known that certain bones of the body con- tained these constituents in other proportions than those named ; for example, the petrous portion of the temporal bone had been shown by Davy to owe its stony hardness to an exceptionally large proportion of earthy matter. But Dr. G. 0. Rees has KICKETS. 239 pointed out some interesting particulars as to the relative proportions of these elements in the composition of different bones. The long bones of the extremities have, according to Dr. Rees’ analyses, more earthy matter than the bones of the trunk. The bones of the upper extremity have a larger pro- portion of the same material than those of the corresponding bones in the lower ; the humerus has more than the radius and ulna ; the femur more than the tibia and fibula ; while the bones of the fore-arm, as well as those of the leg, are respectively alike in constitution. The vertebrse, ribs, and clavicles are similarly constituted. The ilium has more earthy matter than the scapula or sternum ; the bones of the head have more of this material than those of the trunk. In the foetus the same law prevails as regards the relative quantity of the earthy matter, excepting that the long bones, and the cranial bones, do not contain the excess of earthy matter which characterizes them in the adult. The diseased state, called Rickets, so common in the children of scrofulous parents, and in the ill-nomished ones of the lower orders, consists in a deficient deposit of earthy matter ; the animal matter bemg probably of an unhealthy quality. In this disease the bones are so flexible, that they may bend imder the weight that they are called on to support, or under the action of the muscles. The lower extremities exhibit deformity first, and to the greatest degree, and the direction in which they become bent is evidently influenced by the superimposed weight ; the bend almost always appears as an aggravation of the natural curves of the bones. The rickety femur has always its convexity duected forwards ; the tibia is convex forwards and outwards, and the fibula follows the same direction. When the nutritive powers of the system are fully restored, the deposition of earthy matter goes on in its healthy proportion, the animal matter becomes healthy, and the bones acquire their due degree of strength and hard- ness. In the tibia of a rickety child. Dr. Davy found, in 100 parts, 74 parts animal matter, and 26 earthy; and Dr. Rostock found in the vertebra of a similar subject 7 9- 75 animal, and 20‘25 earthy. The brittleness of the bones in old age is due to an opposite cause, namely, the gradual removal of animal matter, so that 240 MOLLITIES OSSrUM. the earthy matter nnduly preponderates. But this state can- not be looked upon as morbid ; it is the natural result of the feeble condition of the powers of nutrition, aiid the di-ying up and hardening of the tissues which ensue as age advances ; and it will vary in different incbviduals, according to the original strength of constitution of each, and according to the fi’eedom from exposure to debilitating influences. In that rare form of disease, known as mollities ossium, which occurs m adults, the bones are sometimes so soft that they may be indented by pressme with the Anger. The nutritive pro- cesses concerned in the formation of the bone seem affected, for not only is the osseous tissue deficient in earthy material, but the animal matter is not in a healthy state, and in many instances fatty matter is present in unusual proportion. In these cases, the pathology of winch is very obscm’e, earthy phosphates are often excreted in the urine in abnormal quantity. Analyses of the urine in two different cases are given below.* In 100 parts In 100 parts Analyses. of solids. of solids. Water . . . . . 971-9 — 960-88 — Solid matter 281 100 00 39-12 100-00 Urea Extractives Fixed salts Earthy phosphates precipitated by 50 10-22 12-88 1 1-185 17-7 36-3 45-81 4-21 5-25 •4 13-42 1-02 ammonia Alkaline phosphates precipitated by sulph. magnesia and ammonia 1 1 13 4-21 1-3 3-32 Triple phosphates filtered from the 1 _ lu’ine I The large proportion of earthy phosphate hi these analyses is a very interesting fact. lu the fii-st, the earthy actually exceeds the alkaline phosphate ; and, in the second, it is nearlv equal to it. In healthy lu-ine the alkaline phosphate usually amounts to from ten to fifteen tunes as much as the earthv phosphate. The inorganic salts generally, in these specimens of urine, were in considerable excess. Bones possess a remarkable power of resisting decom- position. Even the animal part seems to acquh-e this power * See “ On Kidney Diseases, Urinary Deposits and Calculous Disorders,” bv Lionel S. Beale. M.B., F.E.S. Third Edition, page 217. CHEMICAL COMPOSITION. 241 through its combination with the earthy. This is manifest from analysmg bones which have been long kept, or fossil bones. Cuvier states that the latter bones exhibit a considerable car- tilaginous portion ; and Bichat found that clavicles, which had been exposed for ten years to the wind and rain at the cemetery of Clamart, presented, under the action of acid, an abundant cartilaginous basis. In an old Roman frontal bone, dug up from Pompeii, Dr. Davy found 35'5 animal parts, and 64‘5 earthy; and in a tooth of the mammoth, 30’5 animal, and 69’5 earthy. Chemical Composition . — The animal part of bone consists of cartilage basis, with vessels, medullary membrance, and fat. The former is readily convertible into gelatine, according to Berzelius, after three hours’ boiling ; and, when this has been removed, there remain only four grains out of 100, which may be considered to have been composed of blood-vessels. The earthy part of bone consists of phosphate and carbonate of lime, with a small quantity of phosphate and carbonate of magnesia. The phosphate of lime forms the piincipal portion of the earthy part : in 100 parts of bone, Berzelius found 51’04 of this salt. It was discovered by Gahn, and the discovery announced by Scheele, that bone-earth consisted of “ phos- phoric acid and lime.” According to Berzelius, the phosphate consists of eight atoms of lime and three atoms of phosphoric acid ; but Mitscherlich regards it as composed of three atoms of lime with one of phosphoric acid (a tribasic salt). It may be formed artificially by dropping chloride of calcium into a solu- tion of phosphate of soda. It appears as a gelatinous precipi- tate, which does not crystallise, and is readily soluble in acids. The existence of fiuoride of calcium in bone was announced many years ago by Berzelius, who found as much as 2 per cent. According to Berzelius, the following represents the composition of bone. The accuracy of these results have been confirmed more recently by Mr. Middleton (^Phil.Mag. vol. xxv., p. 18). Animal matter .. .. .. .. .. 33 30 Bartliy matter . . . . . . . . . . . . 66'70 Phosphate of lime .. .. .. .. 51'04 Carbonate of lime .. .. .. .. .. 11 30 Pluoride of calcium . . . . . . . . . . 2 '00 Magnesia . . . . . . . . . . , . 1'16 Soda and chloride of calciiun . . . . . . . . 1'20 242 COMPACT AND CANCELLATED TISSUE. Compact Tissue and Cancellated Structure. — In examining a section of almost any bone, we observe two varieties of osseous substance : the one dense, firm, compact, always situated on the exterior of the hone, either as a thin layer, or as a dense, thick structure possessed of great strength ; the other loose, reticular, spongy, arranged so as to exhibit spaces or cells, which com- municate freely -vdth each other, and which, being called cancelli, give to this kind of osseous tissue the name cancellated. These cancelli are formed by an interlacement of nume- rous bony fibres and lami- nm, superficial observation exhibiting an indefinite arrangement, have never- theless, in those bones which have to support perpendicular direction. The cancellated stnic- ture of bone is always situated in its interior, enclosed and protected by the compact tissue. The relative situation of these varieties may be well seen hi a vertical section of one of the long bones (fig. 144). At the extremities, the cancellated texture is accumulated, invested by a thin lamella of compact tissue, giving expansion and light- ness to those parts of the bone. In the intermediate portion, or shaft, tlie compact tissue is highly developed, affording great strength in the situation where that quality is the most needed. The compact external sm-face of bone (except on its articular aspects) is covered by a firm tough membrane, termed the periosteum, which, like the perichondi’ium investing cartilage, consists of white fibrous tissue, densely interwoven in all directions (see page 269). The cancelli are filled with fat, or medulla, the marrow of bone. They are lined by a delicate membrane, called the medullary membrane, which serves to weight, a more or less which, although to a Vertical section of the upper end of the Femur, showing the cancellated and compact tissues. OF LIVING AND DEAD BONE, 243 support the fat. In the shaft of the long bones the medulla is contained, not in ordinary cells, but in one great canal, which occupies the centre of the shaft, the medullary canal. Here the medullary membrane lines the compact tissue that forms the wall of the cavity. Both the periosteum and the medullary membrane adhere intimately to the bone. Both are abundantly supplied with blood-vessels, which, after ramifying upon them, send numerous branches into the bone. These membranes are of great import- ance to the nutrition of the bone, masmuch as they support its nutrient vessels ; and, if either of them be destroyed to any great extent, the part in contact with them necessarily perishes : and they not only cover the outer and inner surfaces of the bone, bxit also send processes, along with the vessels, into minute canals traversing the compact tissue, and are, through the medium of these, rendered continuous with one another. When the periosteum or medullary membrane is torn away fi-om the surface of a fresh bone, the vessels may be seen very readily passmg fi.’om the under sm’face of the membrane into the tiny channels (Haversian canals) which pass obliquely into the com- pact tissue. The vessels of the bone ramify throughout its substance, and if they have been injected previously to the removal of the calcareous matter by the action of acid, they will be distinctly seen ramifying through the semi-transparent animal substance. A preparation of this kind di'ied, and after- wards preserved in spirits of turpentine, serves beautifully to exhibit the disposition of the vessels in bone. Of living bone and of dried dead bone. — The authors of many manuals and treatises on minute anatomy have described the structure not of living or recently dead bone, but of bone which has been dead for a long time and has undergone desiccation. The student is thus led to acquire a notion of the structure of bone as imperfect and incorrect as would be that which he would form of the structm-e of skin, nerve, or muscle, were he to examine dried specimens of these tissues only. We desne to learn what is the structure of tissues, and how they live and grow and decay in the living body ; but the structm-e of bone and teeth has been described, not as it may be demonstrated in these tissues when they are fresh, but only as it appears after 244 AN ELEMENTARY PART OF BONE. they have been altered by drying, and after they have been completely deprived of their living matter. An elementary part of dead dried hone . — An elementary part of fully-formed dead and dried hone consists of a space (lacuna), occupied in the recent state with genninal matter, with a certain portion of hard osseous tissue which is traversed by numerous pores or channels (canaliculi) passing from one little space (lacuna) in a tortuous manner to adjacent lacuna, fig. 145. An elementary part of living hone. — An elementary part of fully-formed living hone consists of a mass of germinal matter, surrounded on all sides by, and continuous with, a thin layer of soft formed material, which passes uninterruptedly into the hard calcified formed material (matrix or intercellular suhstance of authors) pi. XVIII, fig. 164. This hard material is in the fully formed bone penetrated everjAvhere by very fine channels (canaliculi) through which the nutrient fluid passes towards the masses of germinal matter ; for, as the hard material in its fully formed state is almost impermeable, nutrient fluid coidd not reach the germhial matter were it not for these little canals or canaliculi in its substance. An elementary part of every kind of bone at a very early period of its formation, consists of a mass of germinal matter, surrounded by a certain proportion of granular, homogeneous or more or less fibrous formed material. This last becomes the seat of deposition of calcareous matter, which proceeds in a direction fr-om without inwards. The formation of the canaliculi takes place in the same du’ection. One of us (L. S. B.) has shown, in opposition to the generally received opinion, that the formation of these tubes commences not at a point nearest to the germinal matter or “ cell,” as has been repeatedly stated, but at a distance from it. See pages 249, 254. The ditference between dead hone and living hone is simply tliis : in the tu’st, formation of tissue has everywhere ceased ; while in the last, it is still proceeding, and around each mass of bioplasm the production of matrix and the deposition of calcareous salts in the matrix already formed is going on. These changes may proceed very slowly, but in all living bone they are taking place. The only matter in a hving bone which is actually alive is that which is ordinarily termed the “ nucleus" LACUNA AND CANALICULI. 245 01’ the “ bone cell ” in the space or lacmia, and which is here spoken of as the germural or li’^dng matter or bioplasm. Plates XVII to XIX. The fully-formed osseous tissue around, on the other hand, is to all intents and purposes, as devoid of life while the bone yet remains a part of the living body, as after it has been removed, or after the body has died. This small mass of germinal matter, perhaps not more than one-twentieth of the bulk of the proportion of bone tissue which belongs to it, alone possesses active powers. This only can grow and give rise to the formation of matrix. Bone cannot produce bone any more than tendon can give rise to tendon or muscle form contractile tissue, but the germincd matter or bioplasm only is instrumental in the formation of every one of these tissues, and without this the production of tissue is impossible. Of the Lacunce and Canaliculi . — All the osseous tissue with which the human anatomist is concerned is of such bulk as to contain the series of pores and cavities already alluded to for the conveyance of fluid. These pores always advance into the bone from open orifices on its vascular surface. They are arranged in sets, each of which, after anastomosing with neigh- bom-uig ones, discharges itself uito a small cavity or lacuna, in Two lacunse of osseous tissue, seen on their surfaces, showing the disposition of their pores. The granular aspect of the tissue both on their walls and around them is well represented.— Magnified 1200 diameters. Drawn from a preparation of the cancelli of the Femur made by Mr. Tomes. Transverse section of a part of the bone surrounding an Haversian canal, showing the pores commencing at the surface, a, anastomosing and passing from cavity to cavity. —Magnified about 300 diameters From a preparation made by Mr. Tomes. which its mdividual pores coalesce. From the sides of this lacuna other pores pass off to similar cavities in the vicmity, and, fr’om its opposite sm-face, others proceed to penetrate still deeper into the tissue. These pour themselves into another lacuna, or 246 BONE CORPUSCLES. divide themselves between two or three, which are connected in like manner by lateral channels, fig. 146. From these again pass others ; and so on, until the whole substance of the bone is perforated by them, so that no particle of the hard osseous tissue is distant more than the loooo of an inch fi'om one of these fluid carrying canaliculi. When this beautiful system of microscopic pores and cavities was first seen, it was not recognized as such. The lacunae were imagined to be solid corpuscles (a name still commonly applied to them), and the lines radiating from them to be branctdng threads of the earthy constituent of bone. In the dry bone the lacunae and canahcidi are both filled with ah’, and in conse- quence of the great difference in refi’active power between the air and the transparent bone tissue, the fight is sc bent out of its course in passing from one medium into the other, that the cavities and tubes appear blach, as a small air bubble in water appears like a mass of dark solid matter. It was tliis solid appearance which led Purkinje, their discoverer, to call them “ bone corpuscles.” They may be proved in many ways, however, to be real excavations in the tissue. With a sufficiently high power then- opposite walls can be distinctly seen, as well as their hollow interior ; but the most conclusive evidence lies in our being able to fill them with fliud. If a dry section of bone, in which they are very apparent, be moistened with oil of turpentine while in the field of the microscope, the course of this penetrating material can be vdtnessed, as it advances mto the tissue. It is seen to run quickly along the pores from the Haversian canals, and from the surface of the specimen, where they have been cut across. Havfiig entered a lacuna, it sud- denly extends along the pores radiating fi-om it, and, through these, reaches other lacrmaj ; rendering the tissue transparent by fillmg up its vacuities. In parts where air has previously occupied the vacant spaces, and the tiupentine cannot displace it, the characteristic appearance of minute bubbles is often present. The refractive power of the turpentine so nearly corresponds to that of the osseous tissue, that the whole section appears homogeneous, and it is only with great difficulty that either lacunse or canaliculi can be discerned: so different are the appearances produced by different processes of examination in the same dead (filed tissue. OF THE LACUNA. 247 Tlie lacunae of osseous tissue, if examined extensively in the vertebrate class, are found of very various shapes : sometimes scarcely to be distinguished from the pores, of which they are simple fusiform dilatations; at other times large and bulky, and forming the point of junction of a great multitude of pores. Mr. Tomes has allowed us to represent the principal varieties which he has met with in the human subject; and some re- markable ones from the lower animals are appended (fig. 147.) Fig. 147. Form of various lacunae, and their pores:— a. Simple irregular cavities, without pores; from an ossifica- tion of the pleux*a ; 6. from healthy bone of the human subject, b'. One of the outer lacunae of an Haversian system, with the pores all bending down towards the H canal, c. Other forms from human bone, showing the lateral connecting pores. d. From the boa. External lacunae of an H system, with unusually large pore.s dipping towards the vascular surface, d'. Cavity intermediate between a lacuna and a pore. e. Another variety from the same reptile.— From Mr. Tomes. But though varieties are occasionally met with, yet, in the true bone of man and mammalia, the lacunae possess a very constant form ; being somewhat oval and more or less flattened on their opposite surfaces. The two surfaces look respectively to and from the nearest surface of the tissue and meet in a thin edge. As pores pass off equally from all parts of the lacunae, it follows that by far the greater number pass to or from the surface of the bone ; an arrangement admirably adapted for the transmission of the nutritious fluids which transude through the walls of the vessels. In fig. 145 the lacunae are seen on their surface; in fig. 146, on their upper edge. The lacunae have an average length of -f^Vo inch, and they are usually about half as wide, and one-third as tlfick. 248 OF THE FOKMATION The diameter of the pores is from Ywi'oo i^ooo inch. In growing hone the canalicnli are probably occupied by the original matrix of the cartilage or organic textm-e, but in bone which has ceased to grow the organic material contracts and becomes dry. The canalicnli are in that case true tubes, with- out any soft material occupying then’ cavity. Air is sometimes fomid in the lacunae and canaliculi even of recent bone, pi. XIX, fig. 184 ; and there is reason to think that dming life this is the case in certain parts where the osseous tissue is fully formed and old. The osseous tissue thus studded by thousands of flattened lacunae, which lie for the most part in planes parallel to the surface, has a decided disposition to split up into lamince, fol- lowing the same dkection. This is more erident in the bones of old persons, and may be promoted by maceration m dilute acid. It is most apparent where the mass of material between tAvo vascular surfaces is great, and the series of lactinae nume- rous. This lamellated structure, there is reason to think, is due to the manner in which the development and groAvth of the osseous tissue proceed. See page. 265. Of the formation of Lacunce and Canalicidi. — The investi- gation of the formation of Incnnse and canaliculi in growing bone presents difficulties, and many of the conclusions which have been arrived at upon the matter have been based rather upon hypothesis than iipon actual obserA'ation. It is remarkable that some of the mews entertained upon this subject ai’e opposed to actual facts which may be readily demonstrated by a careful anatomist. It is desu-able, therefore, that Ave should study the changes which may be obseiwed to take place in simple cartilage during its coiiA’ersion into bone. Noav, in the frog, the phenomena occur much more sloAvly than in mammalia, while the elements of the tissue are upon a larger scale, and in properly prepared specimens AA’e can trace the various stages through which the cartilage tissue passes in its conversion into bone Avith great accm'acy. If the reader will attentively examine the figures referred to, a very short de- scrijAtion AAnll enable him to grasp the actual facts. Fig. 148, pi. XVII, represents a A’ery thin section of cartilage at the edge of one of the cranial bones of a common fi'og, not quite OF LACUNA AND CANALICULI. 249 full grown, prior to the commencement of ossification. The germinal or living matter and the matrix or cartilaginous tissue are well seen. The drawing represented in fig. 149 was copied from a part of the tissue fm’ther inwards, or in other words, nearer to the bone tissue ah-eady formed. Here globules of earthy matter may be seen deposited in the matrix so as to form imperfect rings around the cartilage cells. The calcareous matter it will be observed has been deposited in the matrix (formed material) at a point midway between adjacent masses of germinal matter, that is, m the oldest 'portion of the formed material of the cartilage. The deposition gradually proceeds from roitliout, imcards. See also figs. 163, 164, pi. XVIII. This is invariably the case in every form of bone. While this process is going on, the outer part of each mass of germinal matter gradually undergoes conversion into matrix, which in its turn becomes impregnated with calcareous matter. The next stage is seen in fig. 150, where the calcareous globules have encroached still nearer to the bioplasm, and in figs. 151 and 153 the incorporation of the earthy matter with the organic matrix is almost complete. Distinct globules are no longer to be seen, and the tissue is fast assuming the characters of fully formed bone. The calcareous matter is precipitated in distinct globules, which are well seen in the drawings, and these may be detected, with the aid of very high powers, in the formation of the osseous tissue of mammalia. Indeed, for some time after the first deposition of the cal- careous matter in the formed material, the very thin fragments of the bone, which may be torn away, and exhibit the appearance of fibres (a fact pointed out many years ago by Dr. Sharpey), show many minute globules, pi. XVII, fig. 154, but slowly the calcareous matter becomes more homogeneous, in consequence, probably, of changes occurring in its substance, and its more perfect incorporation with the organic matrix ; and rdtimately the hard mass appears even in textm-e, uniformly transparent, and as has been already stated, penetrated everywhere by minute canals. During the progress of the changes above described nutrient material and calcareous matter in solution have been con- tinually flowing towards the germinal matter, and fluid de- prived of its elements of nutrition and earthy salts, m the opposite 250 FORMATION OF LACUNA. direction. The soft matrix of the cartilage is everywhere per- meated by these fluids ; but as its calcification proceeds, the area of the tissue, which is permeable, becomes more and more restricted, until at last the only peianeable textm’e which remains in the bone is that thin portion which lies between the globules of caicareous matter. These lines being continually traversed by currents of fluid the deposition of calcareous matter is prevented and free channels for the conveyance of the nutrient fluids are thus retained, pi. XVII, fig. 153. These tubes or channels are therefore the altered spaces which are left between the calcareous globules oiiginally depo- sited. They were at first triangular in outline, but gradually they have become altered by the filling up of the angles, until at last they become pores, the section of which is nearly ch- cular, fig. 1 64, at «, pi. XVIII. The views here advocated accord more nearly with the teachmgs of Henle, who compared the formation of the lacimae to the changes which occur in the walls of certain vegetable cells through the secondary deposits of which pores are left (pi. Ill, p. 84, fig. 28), than with those of any other observer. Thus, the deposition of the calcareous matter is tnily a physico-chemical operation, but the formation of the matrix cannot be thus explained nor can the precise seat of commence- ment of the deposit, and its gradual encroachment towards a centre, be thus accounted for. Mr. Rainey* has described the phenomenon as if it Avere pm-ely physical, because he found that calcareous particles could be deposited in a previomly formed matrix artificially, fig. 158, pi. X^ III. Now, Mr. Ramey’s drawing, fig. 160, though fairly representing the arrangement of a portion of dead bone, gives no idea of the manner in which the tissue is formed, for the most important element, that Avhich is never absent in growing bone — that A\dthout which the formation of such a tissue is impossible, has been ignored, as if it did not exist. Mr. Rainey has entirely omitted the ger- minal or living matter, or bioplasm, which is to be seen in every specimen of actually growing bone, shell, and every other tissue. In eA'ery one of the spaces represented in Mr. Rainey s figm'e a mass of germinal or liAung matter, or “ nucleus,” existed when the specimen was fresh. See figs. 159, 163, 164, pi. X^ 111. * “ On the Mode of Formation of Shells of Animals, of Bone,” &e. Mg. 14S. FORMATION OF LAGUNA. PLATE XV: Cax’tila^e of the temporal bone of an adult frog, prjox* to ossification, showing bioplasm and formed material. X 700 p. 218. Fig 149. Anotner portion of the cartilage near ossifying surface, from the same specimen as Fig. 118, showing globules of calcareous matter, a, deposited in matrix, p, 249. Fig. 150. A further stage of the same process as that represented in Fig. 149. p. 249. Fig. 151. Two lacunse from the frontal bone of the adult frog in process of formation. The mode of formation of canaliculi is shown, p. 249. Fig. 152. One third of the innerparc of the wall of a fully- formed laci'ina. magnified 1,700 diameters, p. 250, Fig. 153. Fig. 154. Two recently-formed Lacunse from the frontal bone A fragment of osseous tissue torn from perfectly of the frog. As the lacunae advance in age, the formed bone, from the frog. The canalicular tubes canaliculi become narrower. X 700. p, 260 between the particles of calcai'eous matter are well seen. X 1.700. pp. 249, 266. Fig. 155. Fig. 156. Fig. 1,57. Two lacunse from the femur of the kitten at birth. X 700. p. 250. Two lacunae in the recently formed bone of the femur of thekitten. The bioplasts have undergone division, p. 287. A small lacuna kitten. Almost perfectly formed- Magnified 1,700 diameters, p. 250, L. S.B., 1861.] Tiioo of an inch X 7‘30. X 1,700. [To face page 250. VIE^YS OF KOLLIKER A\D YIRCUOW. 251 If the growing bone of any animal be examined, after having been properly prepared with carmhie fluid, the masses of bioplasm vdll be demonstrated Avithoiit difficulty in the lacnnal spaces. The fact of the presence of germinal matter or bioplasm in the lacnnm of folly formed bone has however been generally admitted by anatomists since 1850. Under the name of “ nucleus ” the bioplasm had been observed in the lacnnge of many specimens of osseous tissue, and Tomes and De Morgan demonstrated indications of these bodies in the lacuiim of fossil bone, in then- paper published in the Phil. Trans, for 1853. The masses of bioj)lasm are as necessary to the production of bone as they are to the formation of every other tissue. They are not dh-ectly concerned in the precipitation of the calcareous matter, but in them absence the production of matrix would be impossible. It is alone by the instrumentality of these masses of bioplasm that the regular circulation of fluids holding m solution the calcareous salts, is maintained throughout every period of bone fonnation. By this process the regularity in the formation of osseous tissue, which is so remarkable, is secixred. See pi. XVII. It is desirable in this place to refer briefly to the AueAvs generally entertained by recognized authorities concerning the formation of lacunae and canaliculi of bone. Tlte views of Kolliker and Virchow . — Kolliker considers that the capside of the cartilage cell and the intercellular matrix become impregnated with calcareous matter, Avhile the granular cell corresponding to the primordial utricle of the vegetable cell, remains AAnthin unaltered. He thinks that the canaliculi extend through the matrix by resorption. VirchoAv says bone contains, “in an apparently altogether homogeneous basis-substance, peculiar stellate bone-cells dis- tributed in a very regular manner.” According to this Anew it is maintained that tlie matrix is formed as a true intercellular substance, Avhile from the “ cells it is supposed that processes groiv out, and that these gradually make their Avay through the matrix and anastomose with corresponding processes from neighbouring cells. The “ lacuna ” is said to be occupied by a “ cell ” Avith stellate processes wliich pass into the canaliculi.* * In the following note, copied from page 417 of Dr. Chance’s translation, Vir- S 252 CANALICULT OF BONE There are few points in minute anatomy upon which such different views have been advanced as the one under con- sideration, for observers differ not only in the explanations and opinions they have put forward, but there are iri’econ- cdable differences regarding their statements of fact. To assert that the cells throw out processes, is merely fanciful, for there are no facts whatever to justify such a statement. Al- though it has been repeatedly stated that the bone “ cell ” vdth its canalicular prolongations may be actually detached fl’om the matrix into which its processes have bored then' way, we have never seen any specimens which appear to us to justify such an inference, "while we have utterly failed in every attempt to prepare specimens which would lead us to infer the existence of the slightest grounds for such a conclusion. With regard to Virchow’s view, it may be remarked that although it is true that in certam cases in which the bioplasm or germinal matter is more or less stellate, the so-called pro- cesses project a very short distance from the mass, they never, as far as can be ascertained, correspond in number with the canaliculi which exist in the fully formed bone, the latter being twice as numerous as the processes in question. Almost any form of bioplasm may exhibit this stellate appearance, but it has nothing whatever to do with the formation of the canali- chow expresses liimself very clearly as to tlie maimer in ■which the supposed processes are formed from cells : — “ The cartilage cells (and the same holds good of the marrow cells) during ossification thro'w out processes (become jagged) in the same ■v\'ay that connective tissue corpuscles, ■which are also originally round, do, both physiologically and pathologically. These processes, •wliieh in the case of the cartilage cells are generally formed after, but in that of the marrow cells frequently before, calcification has taken place, bore their way into the intercellular substance, like the villi of the chorion do into the mucous membrane and into the vessels of the uterus, or like the Pacchionian granulations (glands) of pia mater of the brain into (and occasionally through) the calvarium.” Again, “ the cells which thus result from the prohferation of the periosteal corpuscles are converted into bone corpuscles exactly in the way I described when speaking of the marrow. In the neighbourhood of the surface of the bone the intercellular substance grows dense and becomes almost cartilaginous, the cells throw out processes, become stellate, and at last the cal- cification of the intercellular substance ensues.” This view of the fonnation of the canaliculi will be understood by reference to figs. 161, 162, pi. XYIII, in which the processes of the cell are represented as “ boring ” them way through the already calcified tissue. In fact, however, canahculi exist long before the formation of the calcified tissue has taken place. NOT PROCESSES OF A “CELL.' 253 cnli in Lone for that part of the canaliculus nearest to the lacuna is the last that is /ormef/, whereas if the canaliculus were a process of the bioplasm, that portion nearest to the bioplasm must be fu’st developed. In cases m which a portion of a lacuna with part of its canaliculi are detached from bone tissue which has been de- calcified, it is probable that the circumstance is correctly- explained as follows : — The inmost layer of tissue constituting the wall of the lacuna and of its canaliculi differs in consistence and resisting property from that which is external ; not that this tissue is developed separately fr-om the general mass of the bone texture. Its greater hardness is probably due to its very slow formation as in the case of the so-called wall of the dentinal tube which affords another instance of the same sort of artificial clistmction of texture, and which has led to a similar view concerning its formation as a textine distinct from the so-called “intertubular tissue.” The size of the lacuna and the diameter of the tubes of the canaliculi diminish as the formation of the osseous tissue ad- vances towards its mature state. How then can the large “ cell- wall” of the young lacuna and of the wide canaliculi be the very much smaller “ cell-wall ” of the same lacuna and narrower canaliculi of the fully-formed tissue ? But it is evident on other grounds that the views under examination have resulted from very artificial notions concerning the structure and growth of connective tissue, and these have themselves been based upon erroueous observation, and the belief in a structural analogy between bone and connective tissues, which exist only in the imagination. Canaliculi not processes of a CellJ ^ — “Although many ol> servers have described and somewhat faintly expressed in their drawings the growth of the processes of the cell above referred to, all agree that they are most difficult to see in healthy growing bone. My ovm observations compel me to dissent from the statements generally made vdth regard to these pro- cesses. As far as I have been able to see, neither the cartilage cell, nor the medullary cell, nor the periosteal cell, nor indeed * The observations in this paragraph were first published in my Lectures on the Tissues, in 1861. [L.S.B.J See also “Archives of Medicine,” No. XVII. 1870. s 2 254 FORMATION OF LACUNiE. any cell in the organism becomes stellate by the ‘ shooting-ont process.’ That cartilage and the other bioplasts or ‘ cells ’ may become angular is perfectly true, and that a few little projec- tions may be seen from different parts of their surface is also true, but these projections and angles have nothing to do with the formation of canaliculi, nor do they correspond to them in number. The appearance is exceptional instead of being con- stant, and a lacuna with numerous canaliculi may be produced without the existence, of an angular cell at all. The mass of bio- plasm is oval from the period when it first existed as a separate object to the time of its enclosure in the lacuna, figs. 163 and 164, pi. XVIII. Into each lacuna forty or fifty or more canali- culi open, and these commimicate with those of adjacent lacunae. Surely, if these were formed in the manner described we ought to be able to demonstrate growing diverticula during the forma- tion of the lacunae, but nothmg of the sort has been seen, and the warmest advocates of the theory have only been able to ob- serve a very faint indication of the arrangement which they believe actually exists. Then- di-awings only show these processes projecting a very short distance from the cells, and no one, I believe, pretends to have seen processes fr-om two neighbouring cells in process of communicating with each other, as shown in the fanciful explanatory drawing in fig. 161, pi. XVIII. I wordd ask, why, if the tubes grow ceutrifugally from the cells, they do not pursue the shortest route and pass in straight lines ? By what force of attraction do the opposite tubes come into contact, and how is the barrier interposed between the tAvo dissolved? But the impossibility of such a theory is shoAvn in tins way. Its advocates only pretend to account for the structure of the friUy-formed bone, and do not attempt to explain by their theory the changes through which the tissue passes during the earlier periods of its formation. It is not only very difiicadt to conceiAm such channels formed by an out-growth, but it is inconsistent AAfith Avhat is generally observed. The tissue requu’es channels for the transmission of nutrient matter during its formcdion, just as much as after its formation is complete. The portion of the canahcidus which is first formed is that AAdiich is most distant from, not that which is nearest to the lacuna and its contents. The formation of of canaliculi takes place in a direction tou-ards and not rOE'./IATION OF LACUNA. PLATE XVIII. Fig. 15S. Deposition of calcareous naaLter in ttie matrix of cartilage. After Mr. Rainey. Tire bioplasm is omitted, p. 260. Fi2. 161. Fig. 159. Bioplast around wlaich the calcareous particles are deposited, and towaids which current.s of nutrient fluid converge. In Figs. 158 and 160 a bioplast should be repi'esented in every space. p.250. Fig. leo. "Bone cells," after Mr. Rainey These are supposed to he formed without any bioplasm in the central spaces, p. 260. Fig. 162. Diagrammatic representation of the imaginary "bone cells” supposed to exist ; and tbeir processes which are supposed to " bore their way” through the already formed hone tissue, p. 252. Diagrammatic representation of fully formed bone, showing the supposed " hone cells ” with their processes which are now supposed to have bored through the hone and to have united with the processes of contiguous cells, p. 252. Fig. 163. Fig. 164. Two bioplasts of hone with imperfectly formed lacunse and canaliculi. These are left during the deposition of calcareous matter in the previously formed xnatiix- p. 254. A further stage of the process represented in Fig. 163. The tissue is now hone. The only matrix left uncalcified is that which corresponds to the canaliculi. The bioplasts have become smaller and now lie in spaces or lacun®. p 25l. [To face page 254. FORMATION OF LACUNA. 255 from the bioplasm of the tissue — the so-called ‘bone-cell’ or ‘nucleus.’” Figs. 150 to 155, pi. XVII. If the canaliculi were formed as supposed it is quite im- possible that every observer should have failed to see the pro- longations of the cell undergoing development and coalescing with those of neighboming cells. The extremities of these tnbes which were gradually extending through the matrix wotdd be rounded, as represented in pi. XVIII, fig. 161, and would contain germinal matter which would absorb the solid matrix, and thus the tube would extend thi’ongh its substance, fig. 162. No such appearance has ever been seen. The canaliculi are no more processes of the cell which bore their way through the hard material than the canals which are left in the masses of secondary deposits m the hard walls of certain vegetable cells are processes pushed out from the germinal matter ui the centre of the cell. It may be said that the growmg matter extending from a spore of mildew “ bores ” its way into the soft material, at the expense of which it grows, bnt in this case the soft material is clearly appropriated by the mildew, and becomes converted mto the germinal matter of the plant. This process, and the con- ditions under which it occurs, are totally different fi-om those which obtain m the case under considei'ation. No stellate “ corpuscle ” has been found in bone, but the stellate appearance of the lacuna, with its radiating canaliculi has resulted from the circumstance that the calcareous matter has been deposited in the matrix in such a manner as to leave intervals arranged in a more or less stellate manner, as has been explamed. There is, however, room for some difference of opinion with regard to the contents of the canaliculi. In dead dry bone it is certain the canaliculi are tubes containing air. In young bone it is clear that all nutrient matter which reaches the bio- plasm must permeate the matrix, and no air exists in the tubes. The organic matrix of the original tissne must remam as the diameter of the canaliculus becomes reduced by the gradual encroachment of the calcareous matter upon it, and it is pos- sible, and indeed likely, that after a time, by the constant passage of fluid, it may be gradually dissolved away, and thus a tube, traversed by nutrient material and always containing OF THE ULTIMATE STRUCTURE 25() fluid, may result. But supposing it to remain, the portion of the matrix which occupies the canalicuh cannot be con’ectly termed “• processes of the bone cell.” ■ Any organic matrix remainmg in the canaliculi is no doubt sufficiently permeable to transmit the nutrient fluids, but as time goes on, it no doubt loses its original firmness and by the constant action of the fluids becomes softened, and the soft tissue is in some cases at last completely dissolved away. After boue has existed for some time, the bioplasm in the lacuna dies and becomes comparatively dry. In some cases ah’ collects in the lacunae and canaliculi. I have seen in the bones, par- ticularly of old persons, a very short time after death, many lacunae and canaliculi thus filled with air, so that no doubt the air was actually in these little cavities of the bone during life. Such bone could not grow, and reparation could not have taken place had it been injured. Under no cii’cumstances could it have passed into a state of inflammation, and had fractm'e oc- curred, union Avould have been impossible. Of the ultimate structure of osseous tissue . — There has been much difference of opinion concerning the ultimate structure of bone tissue. According to some the ultimate osseous tissue is granular, while others consider that it is fibrous in character. It has been supposed that the calcareous material becomes not only thoroughly incorporated but chemically combuied with the material of which the matrix of the cartilage consists. But it has been believed by other authorities that the latter is merely impregnated with the earthy salt,— that the msoluble particles are precipitated in the interstices of the tissue just as might be effected artificially in many organic substances, as, for example, thick gum or ordinary jelly. It must be admitted that arguments are not Avanting in faA^our of both opmions upon this question. In some instances bone may be torn in the longtitudinal direction, AAdiich lends support to the xie^y that the tissue has been, as it were, laid down in plates or superposed lamiuie, haAung a fibrous structure, pi. XVII, fig. 154. On the other hand, Mr. Tomes concluded from his researches that the ultimate structure of the osseous tissue Avas granular. The granules of bone are often very distinctly Ausible, without any artificial preparation, in the substance of the delicate spicidae of the OF OSSEOUS TISSUE. 257 cancelli, viewed with a high power, and in various sections of all forms of bone. Grannies maj certamly be obtained from cal- cined bone, either by bruising a fragment of it, or by soaking it in glycerine or syrup. They may also be made very evident by prolonged boiling in a Papin’s digester. Those represented in fig. 165 were obtained m the latter mode. The grannies vary in size fr’om y oooo tWotto an inch. In shape they are oval or oblong, and often angular. In some few instances, Mr. Fig. 165. of Ultimate sranules bone, isolated and in small masses, from the Femur. {From a preparation of Mr. Tomes.) x 320. T omes has met with, a dehcate fibrous network, which seems adapted to I’eceive the granules in its interstices ; but Mr. Tomes feels that there are some serious objections to this view. A frequent appearance of the granrdar-like textru'e of bone is represented in fig. 165. When bone has been decalcified by immersion in acid, thin shreds corresponding to the lamellse may be removed in a longi- tudinal direction. In these the minute aperture of the canaliculi which have been torn across may often be discerned. In many instances delicate transparent fibres crossuig each other at different angles will be seen, showing, as Dr. Sharpey was the first to point out, that the organic matrix of bone has a fibrous structure, and is more closely allied to fibrous tissue than to cartilage in microscopical characters, as well as in chemical composition. If bone be soaked for a long time in pure glycerine it becomes sufficiently soft to be torn without its structure being altered, as is necessarily the case when it is decalcified. Such a specimen is represented in pi. XVII, fig. 154, in which an indis- tinctly fibrous material has embedded in, or disseminated through, its substance a number of minute rounded particles of calcareous matter, collections of granules of Mr. Tomes. The intervals between these particles constitute the canaliculi. A careful examination of bone at different stages of de- velopment, and under the highest magnifying powers which have been made leads us to form the following conclusions regarding its ultimate structure. The calcareous matter is at first deposited in the organic matrix m the form of minute granules which gradually mcrease in size and form rounded or oval particles. In the batrachia these are of considerable 258 GLOBULES OF BONE TISStTE. dimensions. PL XVII, figs. 149, 150. It is not surprising that we should occasionally meet Tifith indications of these in adult bone. Such appearances have been referred to by Dr. Shai’pey, Gegenbauer, Allen Thomson, and others, but different explana- tions have been offered. Such globules, formed no doubt by the gradual coalescence of smaller ones, are sometimes traversed by canaliculi, and in dentine such globular masses are some- times so arranged as to interfere, during development, with the passage of nutrient juices to the matrix which lies between them. This, consequently, remains soft and uncalcified, and when the tooth is dried, spaces result between the several glo- bules. These spaces, of course, then contain air, and appear black when the dentine is examined by ti’ansmitted light. Dr. Sliarpey states that he has found layers of rounded nodules, near the surface of the shaft of long bones, lyuig among the circumferential lamimse, and accepts the explanation of C. Loven, of Stockholm, who thinks that these botryoidal masses correspond to depressions made in a corresponding portion of bone by the process of excavation. In a cross section of a large serpent’s rib. Dr. Sliarpey noticed an outer and inner series of concentric lamellse, which could be easily peeled from one another after decalcification. The detached surfaces showed elevations and corresponchng depressions. Many of the former contained one, two, or three lacunas in their substance. Whenever earthy salts are deposited m an organic matrix they tend to form these nodular aggregations and botryoidal masses, as was first shown by Mr. Rainey, who caused cal- careous salts to be deposited in gum, gelatine, and other trans- parent organic matters of tlie same kind. ^Vhether bone tissue should be regarded as an organic matrix merely infiltrated with the earthy salts, — a mere admixtm-e of the organic and earthy matter, or a true chemical combination of earthy and animal matters, is a qnestion which still remams open to discussion. Of the Vessels of Bone . — We now proceed to inquire mto the manner in which the distribution of blood to bone is pro- vided for. A texture undergoing constant change, containing much animal matter, and needing a constant sujiply of nior- ganic material, must necessarily be largely supplied with blood, the common source of the nutrient materials of all tissues. VESSELS OP BONE. 259 The blood-vessels of bone are very numerous, as may be satisfactorily seen on examining a well- injected specimen. The arteries of the compact tissue are in great part derived from those of the periosteum, and pass into the canals obliquely. If the periosteum be torn from the bone, these vessels can always be seen without difficulty. The vessels which penetrate the cancellated texture of the extremities of the long bones are very large, and their branches ramify freely among the cancelli. The vessels of the membrane of the medulla which is con- tained in the shaft, receive their blood from a special artery that pierces the compact tissue through a distinct canal, known as that for the nutritious artery. This vessel immediately divides on entering the medullary canal ; of the branches, one ascends, the other descends, and both break up into a capillary network, anastomising with the plexuses in the extremities of the bone, derived from the arteries that penetrate there. From the copious vascular network tlius formed 'vvithin the bone, the innermost part of the compact substance of the shaft receives its blood-vessels. Haversian systems, and rods . — The arrangement of the vas- cular canals was discovered by Clop- ton Havers, who showed that these chamiels were pretty unifoianly dis- tributed through the compact tissue, and inoscidated everywhere with one another. In the long and short bones they follow the same general direction as the axis of the bone, and are joined at intervals by cross branches. The meshes thus formed are more or less oblong (fig. 166). The deeper ones open into the contiguous cancelli, with the cavities of which they are continuous. The arteries and veins of bone usually occupy chstinct Haversian canals. Of these the venous are the larger, and com- monly present at irregular intervals, and especially where two or more branches meet, are pouch-like dilatations (c, fig. 166), calculated to serve as reservoirs for the blood, and to delay its H aversion canals, seen on a longitu- dinal section of the compact tissue of the shaft of one of the long- bones x—a. Arte- rial canal, b. Venous canal, c. Dilata- tion of another venous canal. 260 HAVERSIAN CANALS. outward flow. In many of tlie large bones, particularly in the flat and irregidar ones, the veins are exceedingly capacious, and occupy a series of tortuous canals of remarkable size and very characteristic appearance. These are well described bv Bres- chet in his elaborate work on the venous system ; from which vary in diameter fr-om ^5^0^ to the of an inch, or more, the average being about 3-^^. Their ordinary distance fr-om one another is about -pi-g- of an inch. They may be regarded as invokitions of the surface of the bone, for the purpose of allow- ing vessels to ramify in its substance in great abundance. It is evident that the cancelli, and even the great medullary canal itself, are likewise involutions of the osseous surface, though for a partly different end. These larger and more irregular cavities in bone may be considered as a dilated fui-m of Haver- sian canal. They contain vessels not only for the nutrition of the thin osseous material forming their walls, but also for the supply of the fat enclosed within them. Thus the true osseous substance may be described as lying in the interstices of a vascular membrane, or of a network of blood- vessels. The most interesting points in the minute ana- tomy of bone relate to the mode in which nutrition is provided for in those parts not in immediate contact with the blood- vessels. We have already seen that considerable masses of cartilage derive their nutriment fr-om vessels placed on their exterior only, apparently by a kind of imbibition ; but bone, Avhich is of a far harder and denser nature, is unable to imbibe Fig. 167 . the accomjianying figure (fig. 167 ) is taken. The canals run, for the most part, in the cancellated structure of the bones, and are lined by a more or less complete layer of com- pact tissue, AA'hich itself often contains minute Haversian canals. The A'eins they contain dis- charge themselves sepa- rately on the surface. Venous canals in the diploe of the cranium.— After Breschet. The Haversian canals OF COMPACT TISSUE. 261 its nourishment so easily. Hence its surface is greatly aug- mented by the arrangements already detailed ; and, in addition to this, as has been already shown, the osseous tissue itself is provided with a special system of microscopic cavities, “ lacwice^' and “ canaliculi" or pores, by which its recesses may be h'rigated, to a degree greatly exceeding what could have been effected by blood-vessels alone, consistently with the compactness and density required in the tissue. The bony tissue with its canaliculi and germinal matter always has a certain definite relation to the vessels. It may exist as a simple thin lamina, covered upon each side with a highly vascular membrane, or as solid cylindrical processes often arranged so as to form a network, also invested Avith a vascular membrane ; or the osseous tissue may be arranged in concentric laminae round the central vascular canal of Havers, which in the living bone is occupied by a minute vessel, around which are numerous small living particles, masses of germinal mat- ter or bioplasm. These living bioplasts are concerned in the growth and removal of the osseous tissue. See p. 278. Of a tliin plate of bone the tissue in the central part is the oldest. Of a solid cylinder, that in the centre was first formed, while of the laminae of the Haversian system, those at the cir- cumference are the oldest, and the laminae close to the central vessel were the last developed. The first two forms of bony tissue constitute the cancellated structure, and the last (Haver- sian systems) make up the compact tissue of bone ; but, as would be supposed, transitional forms exist, and if the thin laminae of bone forming the boundaries of spaces be very much thickened by the formation of new laminae within them, the arrangement of the Haversian system is approached; while, on the other hand, if the canal in the centre of several adjacent Haversian systems be very much increased in size, in conse- quence of the multiplication of the bioplasts and the removal of the bone tissue, we should get an arrangement very like that seen in the cancellated texture. These differences are not fanciful, but such transitions can actually be demonstrated in almost all bones. A section of a growing stag’s antler affords a very beautiful example of Haversian systems, and shows how the bony tissue groAvs around the blood-vessels (fig. 168). In the central part are 262 AXTLER OF STAG. tlie vessel becomes less, just as the ring of bone is seen to be in- creased in thickness, until near the surface of the antler the central cavitj or Haversian canal is reduced to a mere line. The vessel has wasted, and the blood has ceased to flow. Simi- lar changes gradually proceed in every part of the antler, which at 1 ength becomes a mass of bloodless and perfectly dead osseous tissue. This being cast off, is replaced by a new anfler which passes through all its stages of development like the one that preceded it. In or- dinary perennial bone the vessel in the Haversian canal often becomes very small, but it is very seldom that it ceases to transmit blood or completely wastes. A portion of fig. 168, representing four Haversian rods near the circumference of the antler is seen in fig. 169. A longitudinal section of the antler will give the student a very correct notion concerning the arrangement of the Fig. 169. Haver.sian systems fully formed from the outer part of Fig. 168. but magnified 215 diameters, showing lacinije and canaliculi. Section of the antler of the stag near the tip of one of the cusps. T he centre is marked a. At the outer part, 6, the formation of Haversian systems is nearly complete, bat towards the centre enormous Haversian canals are occupied by air-vessels, black in the drawing. From a specimen prepared by Mr. White- x 20- seen enormous vessels separated by very thin layers of bony tissue. As we pass towards the circumference the diameter of Fig. 168. Arrangement of osseous tissue. 263 Haversian vessels, and the manner in which they are connected together by transverse branches, figs. 169 and 170. The draw- PIG. 170. Circumference, Centre, Longtitudinal section from the same specimen as fig, 108, showing the communications between the very large vessels in the Haversian canals. X 20. ings have been copied from beautiful preparations which were made by our friend Mr. T. Charters White. The reader will now readily comprehend the apparently complex arrangement of the compact osseous tissue. Let us take for example one of the long bones. The entire vascular smfiace consists of — 1, the outer surface, covered by the perios- teum ; 2, the inner surface, lined by the membrane of the medullary cavity and of the cancelli ; 3, the Haversian surface, or that forming the canals of the compact tissue, and having in contact with it the vascular netAvork that occupies them, and which has been already described. These involutions of the surface are so arranged that no part of the osseous tissue is in general at a greater distance than inch from the vessels that ramify upon them. There is a layer of tissue upon the exterior of the bone deriving its nourishment from the periosteum, and which may be called the -periosteal layer. The periosteal pores of the super- ficial lacunre of this layer open upon the surface. There is another layer, forming the immediate wall of the medidlary cavity, and termed the medullary layer. Its lacunae, in like manner, face this cavity ; and the pores of the inner ones open upon it. This layer may be said to be folded so as to invest the plates and fibres of the cancelli ; and all the lacunae of these 2(34 HAVERSIAN CANALS. face these irregular cavities, and theii’ pores open into them. The Haversian surface, too, being an involution of the outer and inner surfaces, and serving to connect them has been said to be formed by an mvolution of the periosteal and medullary layers, and to unite these with one another. Where a vessel enters the compact tissue from the exterior, it carries Avuth it a sheath of bone from the periosteal layer. The lacunae of this osseous sheath, instead of being turned outwards, like those of the periosteal layer, preserve then’ relation to the vascular surface to which they pertain, and face inwards towards the vessel. Wherever the vessel penetrates, whatever direction it takes, and however it branches, it is everywhere accompanied by this sheath from the periosteal layer, or by offsets from it ; and, when it enters the medullary canal, its sheath expands uito the medullary layer. As the vessels of the compact tissue take a longtitudinal direction, a transv^erse section of the bone (fig. 171) will appear pierced by numerous holes, Avhich are the Haversian canals cut across. Each hole appears as the centre of a roundish area, which is the section of an involuted periosteal layer now become Eig. IVI. Fig. 172. Transverse section of the compact tissue of a long bone; shewing, a, The periosteal layer; h, The medul- lary layer.and theintermediate Haver- sian systems of lamella, each perfo- rated by an H. canal.— Magnified about 15 diameters. Pait of the preparation represented in the last figure, more highly magnified; shewing the package of the Haversian systems, and also the light spaces between neighbouring ones. The system, a, appears to fill up an interval between the others. The lacun® are seen facing the Haversian canals, and the pores taking a general radiating direction. At t, an irregular lacuna. a vertical rod, coiitaiuing a vessel in its axis. The Haversian ctmals vary considerably in size, and do not maintain a very close relation to the thickness of them respective osseous walls. LAjMELLiE. 2G5 They are frequently eccentric, owing- to their wall bulg’ing more in one direction than another, to fit in between others in the vicinity ; for though the rods of bone, containing the vessels, affect the cylindrical form, they often present an oval, or even a very irregular figure, on a section ; their close package having modified their forni.'^ The periosteal and medullary layers are also well seen on the same section, the latter cui-ving inwards to constitute the walls of the cancelli. These two layers are of very h-regular thickness. The lamellate, d character of bone can be distinguished in the periosteal, medullary, and Haversian layers ; and, in general, wherever several successive series of lacunae exist. The Haver- sian rods, however, are remarkably prone to exhibit this ap- pearance. Their lamellae, however, are not concen- trie, as commonly des- cribed. The fissures which disclose them are indeed concentric, but they are always incomplete, never extending completely round the canal ; so that the lamellae run into one another at various points. This results from the fact that the lacunae are not arranged in sets equidis- tant from the centre, but are scattered, as it were, independently of one another, at every possible variety of distance from the canal (fig. 146, p. 245 and 172). The larger concentric cracks, which generally run through the lacuna, seem to occur wdiere two or three of these happen to lie nearly in the same curve. Bone is very apt to crack in the interval between the rods ; and each of these rods is really so distinct from those near it, that it may be designated con- veniently, for the purposes of description, as an Haversian system of lamellce. Transverse section of the compact tissue of a tibia from an aged subject, treated with acid ; showing the appearance of lamellae surrounding the Haversian canals- Portions of several systems of lamellae are seen. The appearance of the lacunae, when their pores are filled with fluid, is also seen, as well as the rad'ation from the canals which then remain— From Mr. Tomes. * The irregular size and outline of the Haversian canals thus noticed by Todd and Bowman have been fully explained by the researches of Tomes and De Morgan. See page 267. 266 PEKIOSTEAL AND MEDULLARY LAYERS. In a longtitudinal section of the compact tissue of a long hone the appearance of lamellation (fig. 173) is generally less evident, except where a longtituchnal canal happens to He exactly in the plane of section. This lamellated arrangement appears to be due to the cu’cumstance that the osseous tissue is formed in successive layers, a process which was first satis- factorily described by Messrs. Tomes and De Morgan in their memoir already referred to (Phil. Trans, 1853). The description now given of the intimate texture of the compact tissue of long and short bones A\fill apply, in all essen- tial respects, to every other example of the compact tissue ; the chief difference consisting in the direction taken by the Haver- sian canals, which is Hregular Avhere the tissue follows an in-e- gular course. In general, however, the canals, with the Ilavei'sian rods forming their sheaths, run in the direction in which the tissue needs the greatest strength. Thus, in the long bones it is vertical ; and in those flat bones, which have to support Aveight, it is also more or less vertical ; Avhile in those designed to sustain the action of forces of other lands it is liable to corresponding Amriety. So beautifully mechanical is this disposition of the Haver- sian systems in the compact tissue, that Ave need not smile at the descri]otions of Gagliardi, who, AA’ith imperfect means of observation, appears to have been at least faithful in his attempts to delineate nature. The periosteal and medullary layers are true plates of bone, and the Haversian systems are true fibres or jniis, all connected with one another by dmect continuity of tissue, and most artfidly arranged for the mechanical ends in vieAv ; and Ave cannot sufficiently admire the skill AA'hich has caused the means, employed for these ends, to conspire with those Avhich were indispensable for the due nutrition of the tissue. In the ordinary cancellated texture, each cancellus must be regarded as a little medidlary cavity, containing, as it does, medidla and highly vascular medidlary membrane. The plates of bone Avhich form its walls consist of lamellee, among Avhich lacunm, with their pores, are scattered ; and they sometimes, Avhen thick, contain HaAmrsian canals. Usually, however, the pores of these laminse communicate directly AA’ith the caAnty of the cancellus to Avhich they belong. HAVERSIAN SPACES. 2(57 Haversian Spaces. — Not only does the compact tissue of bone gradually pass into cancellated structure, as described on p. 261, but comparatively large spaces, like cancelli, are to be demonstrated in the compact tissue of a long bone. These are the Haversian spaces of Messrs. Tomes and De Morgan, who have proved most conclusively that, during the life of the bone, the canals become larger, and are converted into spaces by erosion, the removal of the bone tissue taking place in a direc- tion from Avithin outwards. In adjacent spaces the opposite processes may be going on at the same time. The formation of bone takes place from without inwards. An Haversian space therefore gradually contracts to form a canal. The Haversian canals and spaces are seen in a section of dry bone as openings, but in the recent bone they are occupied by a vessel which is surrounded by soft pulpy matter, consisting of a little connec- tive tissue near the vessel, but composed mainly of small living bioplasts. These bodies are also found on the deep layer of the periosteum and medullary membrane, as has been described. They exist in considerable number wherever bone is being formed, and are, in fact, the active agents concerned in the removal of the old bone tissue, and in the formation of the new osseous lamellae. Now, the process of erosion or removal of an Haversian system does not take place quite regularly, for part of an Haversian system may be left while neighbouring systems may be entirely removed. When the formation of the new Haver- sian system commences in the space scooped out, it is obvious that new laminge will be deposited over those which originally belonged to the old system. This is why “interstitial laminae” are always seen between the Haversian systems in a section of the compact tissue of bone, and Ave are indebted to Messrs. Tomes and De Morgan for their very clear and satisfactory ex- planation of this most important fact. When bone is I’emoved by absorption, as in the excavation of Haversian spaces, the surface is sometimes irregularly exca- vated, so as to give rise to a number of small pits or depres- sions which, after a time, are filled up by the deposition of neAv bone. If this laxter be removed it xvill be found to form as it were a cast, and appears nodulated or covered AAoth botryoidal masses of bone tissue. This fact has been referred to by T 268 PERFORATING FIBRES. Starpey, who accepts the above explanation, which was first suggested by Loven, of Stockholm. (Quain’s Anatomy, seventh edition, 1866. “ General Anatomy,” by Dr. Sharpey, page xcviii.) Perforating Fibres of Bone. — Dr. Sharpey has discovered some very peculiar fibres which perforate the lamellae, and as it were pin them together. These have been termed by him Fig. 174. perforating fibres. The holes through which they pass are often seen in detached laminae. They are most easily demonstrated Fig. 175. Magnified view of a perpendicular section through ihe external table of a human parietal bone, decalcified. At a, perforating fibres in their natural situation ; at b, others drawn out by separation of the lamellae ; at c, the holes or sockets out of which they have been drawn* ( H. ilQller, Quain's Anatom 3 ', "th ed.) Tiamellse torn ofiT from a decalcified human parietal bone at some depth from the surfHce; a a. lamellff, showing- reticular fibres; 6 6, darker part, where several lamellte are superposed; c c, perforating fibres. Aper- tures, through which perforating fibres had passed, are seen, especially in the lower part of the figure. Magnified about 200 diameters, but not drawn to scale. (Altered from a drawing by Dr. Allen Thomson, in the 7th edition . f Quain’B Anatomy . ) PERIOSTEUM AND MEDULLARY MEMBRANE. 2()9 in the parietal bone, but are to be found in other situations. They have been observed by Koiliker to exist in great numbers in fishes and Amphibia, and Sharpey has no doubt of their existence throughout vertebrata. H. Muller, of Wiu’zburg, has stated that some of these fibres are of the nature of yellow elastic tissue, and he explams the tubes which are occasionally met with in bone, and were described by Tomes and De Morgan, by supposing that the uncalcified perforating fibres which originally occupied them had become dried up. Sharpey con- curs in this explanation. It is not improbable that some ap- pearances occasionally seen in the perpendicular sections through the compact tissue of the flat bones of the cranium may be due to a modification of the ossifying process occurring in the remains of the vessels and connective tissue which existed at an early period of embryonic life, and formed a temporary tissue, in which the development of true bone was subsequently carried out. Penosteium and Medullary Membrane.— T \\q periosteum is usually described as a fibrous membrane, which gives support to numerous nerves and blood-vessels. Its outer layers exhibit a simply fibrous structure, but its deeper portion, which is con- tinuous with the bone tissue, exhibits a totally different ana- tomical arrangement. Here are seen a number of elementary parts of unossified bone tissue, each consisting of an oval mass of bioplasm invested by a soft formed material. The deeper layer of the periosteum of a young animal is the seat of the formation not only of new bone but of complete Haversian systems. The elementary parts multiply and the capillary vessels are gradually enclosed by the growth of tissue, v/hich at length undergoes ossification, see fig. 187, p. 282. This process has been fully described by Messrs. Tomes and De Morgan. The vessels from both periosteum and medullary membrane pass into the openings of Haversian canals, and when these membranes are gently torn away from recent bone, the small vessels may be seen without difficulty, extending fi’om the deep surface, and penetrating into the canals of the compact tissue. It has been shown by M. Ollier, of Lyons,* that if portions of the periosteum be transplanted to various parts of the organism, * “Journal de la Physiologie,” tom. ii., pp. 1 and 169. T 2 270 MEDULLA OR MARROW, bony tissue will be formed in the new situation. Tbis process is due to tire growth and development of the masses of bio- plasm which exist in such great number at the deep sm’face of the fibrous periosteum. These grow and multiply, and pro- duce formed material, just as if they had remained in the original seat of their development — a striking proof that the hind of tissue formed by living matter depends upon iifi powers rather than upon its position or the conditions to which it is exposed. In certain forms of bone cancer very minute portions of actively growing bioplasm are sometimes carried to the lungs, and grow and multiply and give rise to bone cancer in the pulmonary tissue^ proving that the bioplasm possesses the peculiar property or power of forming this particular tissue if supplied with pabulum. Of the medulla or marrow of hone. — The medulla of bone is a form of almost pure adipose tissue, wdiich contains very httle areolar tissue associated with it. It is a question of great interest how" this adipose tissue is produced. It fills the can- celli, and exists in quantity in the medullary ca’city, and is even found in large Haversian canals. There is no doubt that the elementary parts Avdiich form at length the fat cells of the marrow, are the direct descendants of the bioplasts which gave origin to the cells converted into bone. The proper marroAV cells (myeloid cells) may become converted into bone-tissue or into marrow^ During development, as would be supposed, these myeloid ” cells contain little or no fat, but as the bone attains its permanent character, many of the cells become “fat cells ” instead of being converted into bone-tissue. In the majority of birds these cells do not form fat, but as the bones are freely penetrated by air, the matter which would be fat under other circumstances, is probably oxidised as fast as it is produced, and caused to be eliminated as carbonic acid. Of Myeloid Cells and of the formation of the plates and spiculee of the Cancellated Tissue. — The little plates or cylindrical spicrdes of bone which enter into the formation of the cancelli are represented at first by soft masses, consisting of several ele- mentary parts of bone. These masses may often be detached, Avhen they are found to have the appearance of large compound cells, consisting of many smaller ones. They are met Avith in numbers beneath the periosteum as well as in the medullary NERVES OF BONE. 271 cavity, and in disease the soft spongy tissue which is formed in connexion with the bone consists of soft masses of this kind. These are the so-called myeloid cells, which are really composed of the bioplasts of bone. At an early period of development, the myeloid cell consists only of several small oval masses of ger- minal matter, the outer part of each of which is undergoing- conversion into soft formed material. This compound mass gradually increases, and at a subsequent period becomes impregnated witli calcareous matter, and thus a tliin plate, or a cylindrical column or a dehcate thread of bone-tissue is formed. In fig. 185, pi. XIX, p. 278, a good specimen of the so-called myeloid ceils from one of the cancelli of the bone of the great toe is represented. Two or three of the masses are elongated and much bent. These might become ossified and converted mto the spicules of bone which form the imperfect septa between the cancelli. Around these are many small granular cells, and it is interesting to notice the fact, that while the first structures have a dark- red colour in the specimen, the latter are scarcely tinged with the carmine, although both have been exposed to the influence of the fluid in the same way. The first was growing actively, the last was comparatively inactive, and there can be no doubt that it was being gradually removed as the former strxicture advanced in development. What remained would then become the medulla, and many of the “ cells ” would eventually assume the character of “ fat cells.” Nerves of hone . — In the periosteal membrane of the frog fine pale nerve fibres may be detected ramifying here and there in the tissue itself, in addition to those which are distributed to the vessels. A similar arrangement is seen in the dura mater, and in the sclerotic coat of the eye, and in tendinous expansions composed of white fibrous tissue. Nerve fibres are distributed to the vessels of bone, as well as to the vessels of other tissues, but it is doubtful if the bone tissue itself is supplied vdth nerve fibres. It is true that bone like many other textures which in a state of health are almost insensitive, becomes, when inflamed, intensely sensitive, but this fact may be explained, as in other cases, by changes which have affected the nerves which are distributed to the capillary vessels in great number. [L.S.B.] 272 OSSIFICATION OF CARTILAGE THE DEVELOPMENT OP BONE. In the earliest period of life at which the skeleton can be detected amongst the soft pulpy tissue of which the embryo is constituted^ it is found to consist of “ cells ” or elementary parts forming the simplest form of cartilage. The formed material which at first is so soft as to be destroyed by very slight pres- sure of the finger^ gradually acquii-es consistency, loses water, and slowly increases m density and fii'mness. The temporary cartilages of the mammalian skeleton have the same general shape before as after their ossification ; and as this process is slow, and not finally completed until adult age, they share during a considerable period in the functions of the bony skeleton. In mammalia, bone commences to form at a very early period of intrauterine life in two ways : 1. By the ossification of tem- jwrary cartilage. 2. By the ossification of fibrous membrane. The temporary cartilage exliibits the same shape as the future bone is to assume, but it contains no medullary cavity. It gradually undergoes conversion into a temporary and imper- fect kind of osseous tissue, which is afterwards removed, and true bone formed in its stead. The formation of the permanent bone in mammalia corres- ponds in all essential and important particulars Avith the pro- cess Avhich occurs m fibrous membrane {see page 280), and which results in the formation of osseous tissue. Tliis fibrous textine is not preceded by any form of cartilage. Noav, ill the frog, the changes Avhich occur during ossifica- tion accord AAuth those Avhich haA^e been described as taldng place in the tempoi-ary cartilage of the bones of the skeleton of man and mammalia ; but the changes proceed gradually until the bone is complete, instead of ceasing at a A’ery early period, before, in fact, true bone is formed, as occurs in the latter. In many of the lower vertebrata, AAdiich continue to groAv as long as they live, the bones gradually increase in extent during a considerable period of life, and the formation of the perfect bone results from gradual and uninterrupted changes occurring in the cartilage, neAV cartilage tissue being produced beyond the bone already completely deA^eloped. A.ND FIBROUS TISSUE. 273 In man the temporary cartilages increase in bulk by an interstitial development of new cells until the full growth is attained, A few vessels^ also, shoot into them at an early period, occupying small tortuous canals, which subsequently become obliterated. Ossification commences in the interior of the temporary cartilage at determinate points, hence called points or centres of Fig. 176 . Pig. 177 . Human fcetus, about the eighth or ninth week of intrauterine life, soaked in alcohol and soda, and preserved in glycerine, a, heart ; h, stomach ; c, in- testine, not yet much longer than the body. The branch below the letter is the remains of the om- phalo-mesenteric duct, d, lungs; e, supra- renal capsules kidneys ; g, remains of Wolffian bodies, with ovaries and genital ducts. Points of ossifica- tion are observed in the humerus, radius, ulna, last phalanges of the fingers, femur, tibia, and ribs. The ossification of the clavicle is advanced, but no ossific points ai*e yet to be detected in the feet. Natural size. Human fcetus, about the eleventh or twelfth week. Ossific points are observed of considerable size. But one point exists in the os innominatum and two are seen in the scapula. The shading in the head and face indicates the formation of bone. The ossification of the first and third phalanges of the fingers and metacarpal bones has advanced, but at present there is only one point of ossific deposit in the tip of the great toe and one for the middle toe. In both drawings the development of the anterior extremities is much more advanced than that of the legs. Soaked in soda and alcohol for a few days, and pi*eserved in spirit. Not changed since 1853-4. Natural size. ossification. From these the process advances into the suiTouud- ing substance. The period at which these ossific points appear varies much in the different bones, and in different parts of the same bone. The first is the clavicle, in which the primitive point appears during the fourth week : next is the lower jaw ; the ribs, too, appear very early, and are completed early ; next, the femur, hnmerus, tibia, and upper jaw. The vertebrae and pelvic 274 OSSIFICATION OF bones are late, as Avell as those of the tarsus. See figs. 17t), 177. Some bones do not begin to ossify till after birth, as the patella. It is not possible to demonstrate by the ordinary process of dissection, or by maceration, Fig. 178. the points of ossification which are first formed at a very early period of development of the embryo, but if the soft tissues be made transparent, every spot of earthy matter in the skeleton maybe observed most distinctly as soon as it appears, and liy condensmg a strong light upon the various parts of the skeleton properly prepared, the youngest ossific points are beautifully seen. Figs, 176 and 177, which repre- sent foetuses at the eighth or ninth week, and at the end of the thu'd month, respectively, have been copied from speci- mens prepared by soaking some tune in an alkaline fluid.* In many bones the ossifica- begins at more than one point. Thus, in the long bones, fig. 178, there is a middle point, to form the future shaft ; and one at each extremity, to form the articidar surface and eminences. That in the shaft is the fii'st to appear, and the others succeed it at a variable mterval. The central part is termed the diaph^sis, and for a long period after birth there remains a layer of uuos- sified cartilage between this and the epiphyses, as the ex- tremities are then styled. Pro- cesses of bone have usually their * I liave obtained excellent results from tlie use of a fluid composed of alcohol Vertical section of the knee-joint of an infant; showings the points of ossification in the shaft and epiphysis of the femur and tibia, and in the patella. A few vascular canals are also seen in the cartilage. Natural size.— From the Museum of King’s Col- lege. tion of the temporary cartilage Fig. 179. Scapula of a foetus at the seventh month the progress of ossification. Natural size. The light parts are epiphyses as yet cartilaginons.--From the Museum of King's College, London. TEJiIPORARY CARTILAGE, 275 own centres of ossification, and are termed epiphyses mitil they are finally joined to the main part, after which they receive the name of apo- 2 )liyses. Ossification generally extends in the direction that the future laminae and Haversian rods are to assume, and which corre- sponds in a great measine to that in which it is designed that the chief strength of the struc- ture may lie. Thus, in the hones composing the vault of the cranium, there is always a very de- cided radiation from the most prominent part of the convexity of each, fig. 177. In the scapula this direction is indicated by the lines of shading in the accompanying fig. 179. The outline marks the limits of the temporary cartilage at the time, but these wmuld have extended had the bone been left to grow. Vertical section of cartilage near the surface of ossifica. Of the early changes occur- ordinary appearance otnhe temporary cartilage, a', Per- J «7 «/ tiou of the same more highly magnified. 6, The cells beginning ring during the ossification of assume the linear direction. V, Portion more magnified. C o J *■' Opposite c, the o.ssification is extending in the intercellular Tp.) 1\X>0V(XVV CdVtilciQP, TllG spaces, and the rows of cells are seen resting in the cavities so J '* formed; the nuclei being more separsted than above, c'. Portion of til© same more highly magnified. — From a new-born rabbit ^ which had been preserved in spirit. foetus undergoes very im- portant changes prior to the deposition of the calcareous matter and solution of caustic soda, in tlie proportion of eight or ten drops to each ounce of alcohol. Many tissues are, at the same time, rendered very hard and transparent in such a mixture. It is especially useful in tracing the stages of ossification in the early embryo. It renders aU the soft tissues perfectly transparent, but exerts no 276 PRODUCTION AND REMOVAL ill the matrix. In the vicinity of the point of ossification, for example, m one of the long bones, the “ cells ” are seen to become gradually arranged in linear series, wliich run doMUi as it were towards the ossifying sm’face. The appearance they present on a vertical section is represented in fig. 180. At first their aggregation is irregular, and the series small {h V ) ; hut, nearer to the surface of ossification, they form rows of twentv or thirty. These rows are shghtly undulated, and are separated from one another by the matrix or intercellular substance. The masses of germinal matter or bioplasm of temporary cartilage are small, and pretty unifonnly scattered through a sparing homogeneous matrix, but as they become arranged in rows they increase in size, c' , are closely apphed to one another, and are compressed. This is observed near the ossifying sur- face, and it is probable that as change ad- vances in this situation, the matrix becomes more permeable to nutrient matter, and hence the bioplasts increase in size. The nuclei or new centres of growth are often large and very distinct, especially in the elementary parts which have become em- bedded in the temporary bone. The lowest row of bioplasts appears to dip mto, and rest in the deep narrow cups of bone, formed by the osseous transformation of the “intercellular substance,” between the rows. These cups are seen in a verti- cal section in fig. 180, c c\ and in a trans- verse section on the level of the ossifying surface in fig. 181. As ossification advances between the rows, these cups are of com-se converted into closed areolm of bone, the walls of which are lamelliform, and at first extremely thin. Pig. 181. VI Horizontal section of the ossi- fying’ surface of a foetal hone; shew- ing the cups of bone cut across, with the granular nuclei of the in- cluded “cells.” G, New bone. 6, Nu- cleus.— From the rabbit. Taken from a drawing of l\Ir. Tomes. action on the earthy matter of the developing bone. The most minute ossific points can therefore be very readily discovered. A fcetns, prepared by being soaked for a few days in this fluid, and preserved in weak spirit, forms a very beautiful prepara- tion. The specimen figured was prepared eighteen years ago (1S53-4), and still preserves its transparency. The practical advantages of such a plan over the usual very laborious process of dissection, in investigating the periods of ossification in various bones, are obvious. This fluid will also be found very useful in studying the structure of many soft granular organs. I found it of special service in investigating the anatomy of the liver. [L.S.B.] OF TEMPORARY BONE. 277 The calcareous matter is mainly deposited in the formed material between the lines of cells, so that a network of tempo- rary and brittle spongy bone tissue is formed. In these erypts or spaces the cartilage cells remain, and their ‘nuclei’ still retain their vitality. Calcareous particles are also deposited in the material of which the outer portion of the elementary part consists, and which has been termed the “ cell- wall.” The vessels advance close to the seat of these changes, a]id it is possible that the passage of the nutrient pabulum from the vessels, for the most part in linear streams parallel to the long axis of the bone, as from a base, may determine the linear arrangement and the enlargement of the cells already spoken of. Moreover, as the calcareous matter must have been carried in a state of solution to the matrix, where it is precipitated, it is obvious that at the point where the cells are the largest, much fluid has been set free, and it is probable that this maym part be taken up by these cells. Temporary cartilage contains many vascular canals, and the youngest cartilage cells are situated nearest to these. The rate of growth of the cartilage cells and the formation of matrix gradually dhniuishes as we j^ass from the canals. The vascu- larity of the hone is, however, far greater than that of the car- tilage, and thus the greater supply of pabulum and the more rapid change at the ossifying smTace are explained. The ‘production and removal of Temporary Bone . — The changes which have been already described result in the formation of a soft spongy network of very brittle temporary bone, pi. XIX, fig. 182, at a. Such a tissue, though useful for a short time, when strength was not a requirement, would be quite unser- viceable for supporting the weight of the body, or for the attachment of muscles to move the limbs. This temporary bone is so fragile that it may be easily crushed between the finger and thumb. It consists merely of the soft matrix of the temporary cartilage nregularly infiltrated with calcareous matter, which has been very quickly precipitated. No sooner is this brittle tissue formed than changes begin to take place in it. If we examine the shaft of a long bone in which ossification has just commenced in the central part, as represented in fig. 177, we shall find that calcareous matter is deposited throughout the entire thickness. The temporary cartilage, 278 FORMATION OF HAVERSIAN SYSTEMS. which the shaft of the bone was first constituted, Avas solid. There is no cavity in the cartilage corresponding to the medul- lary caAuty in the permanent bone. The temporary ossification therefore affects the whole thickness of the shaft. In the sub- sequent changes, not only is temporary bone removed, but that which occupied the central paid of the shaft is never re- placed by bone at all. A permanent space is found which m most of the bones of birds is filled vdth air, but in those of other vertebrata is occupied with a form of adqiose tissue, the marrow, myelon, of the bone. As the bone grows in cii’cumference it is clear that all the sjiongy bone first formed must be removed by absorption, for the medullary cavity with its mairoAi' oc- cupies the very spot Avhere the temporary cartilage was first developed. The formation of IlaA’ersian systems and the exact position of the vessels is determined by the changes proceeding beneath the periosteum, which are figured in pi. XIX, figs. 183, 184, and in fig. 187, and Avhich are described on page 282. The ger- minal matter or bioplasm of the original cartilage is instru- mental in effecting this change. The spaces or crypts of the soft brittle temporary bone were of course occupied by many of the cartilage bioplasts, pi. XIX, fig. 182. Soon after the spongy bone is produced, these, or at any rate many of the biojffasts situated in the central part, where the process of calcification commenced, increase in size and number, while at the same time the spicules of temporary bone are eroded and become reduced in thickness. They get soft, and in places actually undergo disintegration into granules. The originally smooth surfaces are now rough, and scooped out into little pits in consequence of the eroding action of the liAung growing bioplasts. These in fact live and grow at the expense of the spongy temporary bone, and at last a cavity is formed, Avhich is occupied by mul- titudes of bioplasts, the descendants of those of the temporary cartilage ; bounding this is a thin shell of temporary bone, which has been formed beneath the periosteum, and lastly, and most externally, is this membrane itself. We see then what becomes of the so-called nuclei of the original cartilage cells after the formation of the temporary bone in the foetal cartilage. That they remain active Avhile the disintegration of the temporary bone is proceeding, has DEVELOPMENT OF BONE. PLATE XIX. Fig. 1S2. Fig. 155. Ossification proceeding beneath the periosteum. a of the scapula, human fcetua at the 5th month showing the mode of formation of the permanent bone. In the lower part of the drawing are seen two lacunse and their canalicuU filled with air X 300. p. 282. Another drawing from the same specimen as that represented in Fig. 183. Two lacunse with their canaUculi are seen to contain air. The shell of bone yet formed is so thin that portions of cancelli are included in the specimen and one cancellus, a, is entirely occupied with bioplasts. The permanent bone in- creases by the formation of new bone tissue immediately beneath the periosteum, a.ta a. x 3U0. p. 282. of an. inch — x 130 — X 700. LTo face page 273. A portion -of cancellated structure with contents of the cancelli " from the first phalanx of the great toe of a girl about 16 years of age. a. portion of the fully formed osseous tissue About the central part of the figure is a spot where it would appear that the bone is being gradually removed. On a line with 6 are several bioplasts witbmatrix which has not yet undergone calcification, c. a capillary vessel with bioplasts, d. the soft material round the bioplasts has a slightly fibrous character, eand/, collections of bioplasts from which the bony plates and spicules of the caucelli are formed. These are the so-called ■■ myeloid cells.' X TOO. p. 271, O.ssifying cartilage and formation of temporary spongy bone (a), from the scapula of the human foetus at the fifth month. In the crypts or spaces of the temporary bone are seen numerous bioplasts, which are probably descendants of the bioplasm of the temporary cartilage. b.A capillary vessel. X 130. pp. '278, 282. Fig. 183. fig. 1S4. FORMATION OF MEDULLARY CAVITY. 279 been most conclusively demonstrated, and in all probability, they afterwards multiply and produce tbe “ myeloid cells ” which take part in the formation of walls of the cancelli, and the bony spicules in the medullary cavity, while others degenerate and only produce the marrow fat cells, as already stated. These active changes could not occur unless the bioplasts were freely supplied with nutrient matter. We find that the blood supply to the soft temporary bone is abundant. Capillary vessels are indeed more numerous while the temporary bone is undergoing disintegration than they are in the original cartilage. It will no doubt have occurred to the I’eader to ask if every cell in the temporary cartilage and in the ossifying fibrous matrix is represented by a lacuna in the perfect bone? From what I have seen I think it probable that, as a general rule, this is the case ; but it is quite possible, as indeed occurs in cartilage, in tendon, and in muscular fibre, that some of the “ nuclei ” situated at the greatest distance from the nutrient surface may gradually undergo transformation into the formed material, with the exception of a very small portion of bioplast matter which dies and leaves a small space oc- cupied with fluid. In this case these particular bioplasts would be obliterated, and would not be represented by lacunse. Of the formation of the Medullary Cavity, and its contents . — Amongst the pulpy germinal matter occupying the crypts of the temporary bone, capillary vessels which were to be detected in very small number prior to calcification increase considerably, and it is not unlikely that the bioplasts which take up the cal- careous material may transfer it to the blood circulating in the vessels. Or, on the other hand, it may be retained by the bio- plasts for a time until required again for the development of the permanent bone which is being formed beneath the periosteum. However this may be, there is no doubt about the fact that the temporary bone is removed, and that the little bioplasts are the agents concerned in its removal. The vessels which are developed amongst these masses, and which are formed by development from the original vessels upon the cartilage have upon their outer surface little bioplasts, of which some take part in the formation of nerve fibres, while others are concerned in the production of connective tissue 280 OSSIFICATION OF MEMBRANE. which exists in a small quantity in every part of the medulla. Thus is formed that vascular membrane which lines every part of the inner surface of the bones, known as the medullary membrane, fi*om which offsets pass and ramify amongst the medulla, and line all the cancelli of the cancellated structure of the extremity of the bones. The bioplasts remaining be- tween the vessels, and in the reticulee, formed by the aivange- ment of the medullary membrane, undergo further change. Some increase in size and form soft fatty matter, which con- tinues to accumulate until an ordinary fat vesicle results, the development of which is described in page 300. Others grow and multiply, forming little collections varying much in shape and size, which have been already described as myeloid cells, fig. 1 85, pi. XIX. The term “cell” is however inappropriate, seeing that they are destitute of anything like a cell-wall, wlrile many are much elongated, and form plates, processes, spicules, or branching threads. These undergo change, and a matrix is developed, in which calcareous matter is at length deposited, and the walls of cancelli and bony spicules result. Lastly, some of the bioplasts which originally occupied the medullary cavity of the bone die, and disappear altogether. Of Ossification as it proceeds in the fibrous membrane of the Cranial Bones. — As the changes whiclt result in the development of permanent bone beneath the periosteum, after the removal of the temporary bone, exactly accord with those which occur when fibrous tissue is converted mto bone primarily, it will be well to describe this latter process in the fii’st instance. The bones of man, not represented at an early stage of development by temporary cartilage, which in its turn is con- verted into a soft spongy form of bone, are the flat extended portions of the cranial bones ; for instance, the parietal, fi-ontal, and the expanded portion of the temporal and occipital. The only bones and parts of bones of the cranium existing originally as cartilage, are the base of the occipital, the sphenoid, except the external pterygoid plate, the mastoid and petrous portions of the temporal, the ethmoid, the inferior turbinated bones, the ossicles of the ear, and the hyoid bone. The flat bones at first appear to be composed of a form of tissue closely allied to fibrous tissue. This membranous struc- ture grows at the edges, just as the cartilage increases at the FORMATION OF PERMANENT BONE. 281 Fig. 186. edges of the cranial bones of the frog. Thus the gradual increase in the size of the flat cranial bones is provided for, fig. 177. The deposition of the calcare- ous particles in the matrix between the masses of bioplasm, their gradual encroachment upon these, and the formation of the canaliculi and lacunse have been fully discussed ; nor do the changes which oc- cur during the develop- ment of these bones difier in their nature from those which may be observed in the process of ossification. as it occurs in some of the fibrous tissues, in old age, or in Ossification in fibrous membrane. From the parietal bone of the foetus at the eighth month. Human subject, x 15. The gradual extension of the bone tissue into the fibrous membrane is well seen towards the risrht of the drawing. The mode of CCr’tO.lIl mOrloicl formation of cancelli, and their transition towards Haversian systems is well seen in the drawing. growths. The process of formation of lacunse may indeed be more easily investigated as it proceeds during the ossification of the fibrous walls of certain cysts, than in normal bone. Of the production of secondary or pernmnent hone . — While the changes already described, which result m the removal of the temporary bone are proceeding, bone development of a different kind is slowly progressing beneath the periosteum, where a thin cylinder of osseous tissue, the future shaft or diaphysis of the loug bone is formed. This grows in thickness by the development of new bone upon the outer surface in the manner discovered by Duhamel, and described m page 284. The minute changes which take place in the development of the permanent bone beneath the periosteum were first described by Messrs. Tomes and De Morgan in their well- known memoir.* As there are several points of detail which the writer of this chapter has since succeeded in determining, a short account of the processes as observed by him will be given. In the main, this will be found to accord with the description * Philosophical Transactions, 1853, rol. i., p. 109. 282 HAVERSIAN SYSTEMS. Fig. 187. given by the distingnished authors above named. The forma- tion of the matrix of the permanent bone beneath the periosteum of the young animal takes place as has been already described in page 269, and it becomes calcified in the same manner, each Httle bioplast separating from its neighbours, while the for- mation of matrix proceeds upon its surface, and accumulates between the neighbouring bioplasts. When the formation of matrix is complete, cal- careous particles are deposited mid- way between adjacent bioplasts, which gradually become encroached upon, and are at length enclosed in the spaces or lacunse in the manner described in pages 248 to 254, and represented in the drawings, figs. 149, 150, and 151, pi. XYII, from the frog. The vessels beneath the perios- teum are at length enveloped as it were by folds of the bone-forming bioplasts, which gradually encroach upon them until the vessel is completely surroimded. It now occupies the centre of a cylinder of bioplasts, the growth of which proceeds Tuitil a layer of some thickness is formed. At tlie outermost part of the soft cylinder ossification commences, and proceeds lamina within lamina until the formation of the Haversian system is complete, fig. 187. New Haversian systems are formed circumferentially beyond them until the bone has reached its permanent diameter. The minute changes which occur have been carefully studied in well-prepared specimens taken from the growing scapula of the human foetus at the fifth month of intrauterme life, and ac- curate chuAvings have been made from two of these specimens. The appearances observed are represented in figs. 183 and 184, pi. XIX, under a magnifying power of three hundred diameters. The changes aauII be understood if the reader will attentiA'ely examine the illustrations, and a more correct idea of the process will be formed than Avould be afforded by a minute and neces- sarily tedious description of the changes which take place. Section from the diaphysis of the meta- tarsus of the calf, after KOlliker To show the mode of development of permanent Lone beneath the periosteum, as described by Messrs. Tomes and De Morgan, a, perios- teum : b, tissue, undergoing ossification ; c, spicules of bone, which, as they grow gradually encompass a vessel w’hich becomes the Haversian vessel; rf, completely formed Haversian systems. X 45. GROWTH OF BONE. 283 Groivth of Bone . — But it must not be imagined, that -when bone is once deposited in a certain form, it thenceforward per- manently maintains its original form and size. In the first place, a most important process of growth is continually gomg on in the cartilage, especially near the surface, by the multiplication of the cells ; and, in the latter situation, by the increase in their dimensions already described (page 276, j)l. XIX, fig. 182). In the long bones this takes place chiefly in the longitudinal direc- tion which is that in which growth is most active ; and it con- tinues, till adult age. This fact has been long ascertained, though its real purpose appears to have been overlooked. Hales and Hunter both inserted metallic substances along the shaft of a growing bone, in a young animal, at a certain .distance apart, and found, after an interval of time, that the distance between them remained the same, or nearly so, while the extremities of the bone were much further apart, thus proving that the principal growth had taken place near the extremities. Secondly, bones increase in dimension by an accession of new osseous substance on their exterior, this new substance consist- ing not merely of new laminte, but of new systems of lammse, and of new involutions of the vascular surface to form new Haversian canals, so that the earlier systems of lamime are covered over by the more recent ones, see fig. 187. But before the observations here recorded, were made, the fact had been proved by experiments with madder. It was ascer- tained accidentally by Belchier that the rubia tmctorum, or madder, mixed with the food of pigs, imparted its red colour to then’ bones, and this circumstance has been ingeniously taken advantage of by several physiologists in the prosecution of researches on the growth of bone.* Duliamel, Himter, and * The colouring of bone by madder results from an aifiuity of the colouring principle for the phosphate of lime. This opinion was distinctly broached by Haller (El. Phys. t. viii. p. 329), and it was subsequently proved by Eutherford, who shewed it experimentally. To an infusion of madder in distilled water add calcic chloride : no change takes place. Then add sodic phosphate in solution. By double elective affinity calcic phosphate and sodic chloride are formed. The phos- phate is insoluble, and subsides in union with the colouring matter as a crimson lake. When madder is given as food, its colouring priuciq)le is absorbed, and cir- culates with the blood ; and it colours first that part of the bone which is in course of formation from that fluid, or which has been last formed, i.e., which is nearest the vascular surface. U 284 STAININa BY MADDER. many others, have performed multiphed experiments of the kind. In the museum of King’s College are some good pre- parations of bones so acted upon. It is found that, in very young animals, a single day suffices to colour the entire skele- ton, apparently in an uniform manner ; in these there is no osseous material far from the vascular surface. But, if we make a transverse section of one of the long bones so treated, we observe the deejoest, or even the only colour, to be really on the vascular surface ; the Haversian canals are each encircled by a crimson ring. This beautifid illustration is due, as far as we know, to Mr. Tomes, who has long possessed some very elegant specimens prepared m this way. In full-grown animals the bones are very slowly tinged, because the great mass of the bone is not in contact with blood- vessels ; each Haversian system, for example, has only its small innermost lamella in contact vdth them, and besides, the osseous matter is altogether more consolidated and less permeable by fluids than at a very early period of life. In the bones of half grown animals a part of the bone is nearly in the perfect condi- tion, while a part is new and easily coloured. Hence, it is easy iii them to distinguish the new fi'om the old by means of madder. Now, madder given to half- grown animals colours the long bones most deeply in the interval between the shaft and ex- tremities, and on the surface of the shaft, immediately beneath the periosteum, where the most active changes are proceeding. When madder is given at intervals, the tints in the bone are interrupted, the layers in course of formation during its ad- ministration are coloured, while those formed during the inter- vening periods are colomless. The long period during which bones retain the madder tinge, shews that the colourmg matter is not readily resumed by the blood, fl’om its combmation with the calcic phosphate. Perhaps few questions have more divided the mhids of physiologists than that regarding the share taken by the periosteum in the growth and regeneration of bone, for these last are essentially the same process. Duhamel placed a ring of silver round a bone of a young pigeon, without injiuing the periosteum. After some time, diniug which the bone had increased in diameter, he found the ring in the medullary canal, which had acqumed a capacity equal to the previous diameter CHANGES IN FORM DURING GRO^YTH. 285 of the whole shaft. In this case, the first effect is upon the periosteum which cannot grow where it becomes tightly grasped by the ring. Immediately beyond the foreign body there is, however, redundant growth, and the sub-periosteal bone-forming texture hicreases in ^gg amount, and gradually, overlaps the ring which is after a time embedded in the newly-formed bone. In early life the cancelli are small, and there is no medullary ca\dty. Gradually the cancelh enlarge, and those within the shaft blend more and more with one another, by the removal to a greater or less extent of the intervening osseous walls, until at length a medullary canal is formed, around which the cancelli are very open, large, and UTegular. This augmentation of the vascular cavities of bone is attended with a development of adipose vesicles and their capillaries in the new space. The fat contained in the medullary canal gradually accumulates so much, that a special artery becomes enlarged to supply it, assuming the very in- appropriate title of “ the nutrient artery of the bone" Of the changes in form which occur during growth of a long hone in length and circumference. — The long- bones ^ , O Diagram to show the mode of growth of a grow in length by the formation of new cartilage cells at the point where the shaft (diaphysis) joins the ^‘epiphy- sis" dcZ,fig. 188. The cartilaadnous por- growth is seen, and the . ^ ^ o Jr lines pro tion of each “ epiphysis " increases in all du’ections by the formation of new cells at every part of its ch'cum- ference, and by the slow multiplication of those already pro- duced. The central part of the shaft (diaphysis) of a growing U 2 Size soon after commencement of ossification, b 6, Epiphyses ; c. Shaft or Diaphysis; d, layer of cartilage between -the epiphyses and dia- physis, which is the last to undergo ossifica- tion. The change in outline of the .shaft at lines prolonged from the shaft of the youngest bone to the epiphyses of the latest indicate the form which the bone would have assumed had growth taken place at the extremities of the shaft only, and not beneath the perios- teum. Altered from Kolliker and others. 286 REPARATION OF BONE, long bone, midway between tlie growing extremities, is clearly the part which was first formed, or the oldest portion of the shaft. The oldest part of an epiphysis must be the centre. The several stages through which a long bone passes during its growth vrill be understood if fig. 188 be carefully examined. In each of the outlnie figures a represents the ossific centre of the epiphyses, and the Ihies prolonged fi'om the extremities of the largest bone indicate the form this would have had in its fully developed state had growth taken place at the extremities of the shaft only, and no provision been made for its increase in diameter by the development of new bone, layer outside layer, around the entire circumference of the shaft beneath the perios- teum, as has been described in page 282. Reparation of Bone . — The great importance of this subject to the surgeon has led to many very interesting researches from the time of Duhamel to tlie present day, and by tliese the several ste]is of the process by which new bone is deposited have been ably elucidated in all that relates to them more obvious characters. AVhen a fracture occurs, blood is, of coimse, effused into the wound, both from the ruptured vessels of the bone itself, and from those of the surrounding structm’es par- ticipating in the injury. This blood soon undergoes change. Its colouring matter is absorbed, and its bioplasm particles (white blood corpuscles) multiply. The fibrin at length dis- appears, being appropriated by the developing bioplasts, and in its place a form of fibrous tissue is produced. This at length undergoes calcification, and from the fomdh to the sixth Aveek a soft temporary bone, termed by Dupuytren provisional callus, results. This is slowly replaced by the development of per- manent bone {permanent callus) from the groAvth and mutiplica- tion of the bioplasts of the torn periosteum of the original bone. The spongy temporary bone invests the exterior of the broken extremities, and extends between them in the foi’m of a case, by AAdiich they are fii'inly held together. If the medul- lary canal has been broken across, and the broken ends evenly adjusted, there Avill be likewise an interior stem of neAv bone connecting the medullary canal of the fi’agments ui the axis of the bone ; the opposed surfaces of the compact tissue being as yet ununited. It Avould appear that new bone is formed more INFLAMMATION OF BONE. 287 exuberantly in the situations of the provisional callus because of their greater vascularity, just as we may suppose the func- tion of ordinary nutrition to be more active in those parts than m the compact tissue of the bone. The permanent callus has all the characters of true bone. When the reparative process in bone is interfered with, either by mal-apposition of the fragments, or by constitutional fault, a spru’ious union may occur by the medium of a ligamentous substance, or even a diarthrodial joint may be formed at the seat of fracture. The ends of the bones become altered in form and adapted to one another, a kind of false capsular liga- ment is developed, and sometimes even an imperfect car- tilage, and a lining membrane furnishing a lubricating fluid. Of Inflammation of Bone, of Canes and JS'ecrosis. — In the development of bone, in the removal of old Haversian systems, and in the formation of new ones, in the union of fractured ends of bones, in caries, and in the formation of bone cancer, the bioplasts or masses of living germinal matter are the active agents. If bone is to be absorbed these little masses of germinal matter multiply very rapidly and increase at the expense of the surrounding bone. On the other hand, if bone is to be formed, it has been shov/n that the masses of bioplasm having increased in number for a time, cease to multiply, but each increases in size, and the outer part of each slowly under- goes conversion into formed material, which in its turn becomes gradually impregnated with hard calcareous salts. The harder the bone is to be, the slower must this process proceed. In inflammation of bone the bioplasts of the lacunm increase in size, and appropriate the formed material adjacent to them. Thus, a lacuna becomes much enlarged, and is found to contain several small spherical masses of bioplasm instead of one (PI. XVII, fig. 156, page 250). The bone tissue between several lacrmm may be disintegrated and removed, and thus a space of considerable extent may be scooped out even in the com- pact tissue, and may be occupied by masses of bioplasm, re- sulting from the division of those belonging to several lacunge. This is one way in which an abscess in bone may originate. In rickets, caries, and cancer, the vital, changes going on in osseous tissue are much more active than in healthy bone which lives and grows but slowly m comparison. In these mor- 288 OF CARIES AND NECROSIS. bid processes the bioplasm increases too fast, and the con- densation of the tissue which is requisite for the production of true bone does not take- place. Here, as in all other cases, rapid change is associated with bi’ief duration, while the well- developed normal lasting tissue is formed very sloAvly, and the changes succeed each other in the most gradual, orderly, and regular manner. In caries, the bioplasm of a part of a bone receives too large a supply of nutrient matter, it grows too fast, and liAms upon the sm-rounding tissue which has been already formed. In necrosis, the death of the bioplasm of many lacunae takes place. It is easy to conceive that such a result must ensue if the supply of blood be cut off, for the currents of fluid, which during life flow thi’ough the canaliculi, and permeate every part of the bone, cease, and the bioplasts die. Changes in the small trunks which supply the Haversian vessels, enduig either in their obstruction, as, for example, by clots, or their oblitera- tion by pressure, exerted upon them, as from the growth of adventitious tissue around, may cause necrosis of a consider- able extent of osseous tissue. Thus elfrision uito the deeper and more spongy portion of the periosteum, as occurs in the formation of a node, may cause the occlusion of some of the vessels passing from this membrane into the compact tissue. The passage of blood through these vessels being interfered with, the bioplasm of all that portion of bone recehung nutri- ment from them must die, and a piece of bone of considerable size may become “ necrosed.” Immediately around this the nutrient matter would flow more fr-eely, but of coiuse less regularly. In consequence the bioplasm of the neighbouring lacunae would grow much faster, and thus a vast number of bioplasts Avould result. These would eA*eu eat away, as it were, but of course A^ery slowly, the dead bone, which soon becomes surrounded by them. After the bioplasts have accumulated to a certain extent, many increase in size, produce formed material, which in its turn ossifies, and thus the piece of dead bone is at length embedded in new irregularly formed bone. This process goes on, unless the AAdiole of the dead bone (sequestrum) is removed by the process aboA^e referred to, or by surgical inter- ference. Before the dead bone can be removed by the surgeon, he has in many cases to cut aAvay very much of the new bone IRRITATION, EXCITATION. 289 which has been produced. Now, it has been said that the dead bone acts as an irritant — as a foreign body — and that this is the reason why the bone increases around it. Such a doctrine is still strongly maintamed, although no one has been able to show exactly what is meant by the supposed “ irritation.” It has been assumed that an irritant or excitant is always necessary to increased action, that by this “ irritant ” the living cells are “excited” to live faster than usual. But for this increased activity all that is really required is a more free access of nutrient matter. The so-called “nritant,” instead of “ exciting,” acts in the most passive manner possible. It allows pabulum to have freer access to the living bioplasm. By it the restrictions imder which growth normally takes j)lace are to some extent removed. There is no “ excitation to increased action ” at all. The more freely living matter is sujiplied with pabulum the faster it grows. “ Increased action ” in a living structure results from the removal of restrictions, as occurs when the rupture, perforation, or softening of the “ cell- wall ” or “ intercellular substance,” takes place. The nutrient pabulum comes more readily into contact :^vith the bioplasm which grows faster, but not in con- sequence of “ stimulation,” “ excitation,” or “ irritation.” The following works may be consulted on Bone : — The systems of Gleneral Anatomy and Physiology ; Meckel, Anat. Grenerale Descript, et Patholog., tom. i. ; Henle’s Anatomy ; Dr. Bostock’s Physiology contains an excellent and learned sum- mary of the observations of preceding physiologists on the structure and growth of bone up to the year 1836 ; Mr. Paget’s paper on the influence of Madder on the Bones of growing Animals, Bond. Med. G-azette, vol. xxv. ; Deutseh, de penitiori Ossium structure, observationes, 1834 : Miescher, de inflammatione Ossium eorumque anatome general!, 1836 : Muller’s Physiology by Baly, vol. i. M. Flourens on the growth of Bone ; Todd and Bowman, the Physiological Anatomy and Physiology of Man, 1843 ; BruUe et Hugueny, in Annal. des scienc. nat., 1845 ; Beck, Abb, lib. einige in Knochen verlaufeude Nerven. Freiburg, 1846; Votsch, Die Heilung der Knoohenbruche per Primam intentionem. Heidelberg, 1847 ; Kolliker in Mittheil. der Ziirch. nat. Gessellsch. 1847 ; Flourens, Theorie expe- rimentale de la formation des os, Paris, 1847 ; Rokitansky, in der Zeitschrift der Wiener Aerzte, 1848 ; Leidy, J., in Amer. Journal of the Med. Sc. 1849 ; Kru- kenberg, in Mull. Arch. 1849 ; F. Bidder, in Mttll. Arch. 1849 ; Robin, in Mem. de la Society de Biolog. 1850, und Gazette Med. d. Paris, 1857, Journal de I’Anatomie et de la Physiologie, 1864; Kolhker in Wiirzb., verb. i. ; Luschka, die Nerven in den harten Hirnhaut Tiib. 1850 ; Die Nerven des Wirbelcanales und der Wirbel. Tiib. 1850, in Zeitschr. f. rat. Med., in Vu’chow-’s Arch., in Miill. Arch. 1855 ; Wagner, A., Ileber den Heilungsprocess nach resorption und exstirpation der Knochen, Berl. 1852 ; Tomes & De Morgan, Phil. Trans. 1853 ; Hilty, U. Der innere Callus und seine Entstehung, Zurich. 1853 ; Redfern in Monthly Journal, 1854 ; 290 LITER ATUKE OF BONE. Maier, R., Das Wacbstlium der Knoclien nacR der Dicke, Freiburg im Br. 1856 ; Kaufmann, F. J., iu Vireli. Archiv. ; Hein, E., De ossium medulla, Berol. 1856 ; Eougct, Ch., Developpement et Struct, du Syst. osseux, Paris, 1856, Journal de la Physiologie, 1858, p. 764 ; Muller, H., in Wiirzb. Med. Zeitsch., band i. ; Weber, C. O. Die Knochengescln^iilste, Bonn, 1856 ; Fiirstenberg, in Miill. Arcb, 1857 ; Lacbmann in Mull. Arcb, 1857 ; Aeby, Cb., in Gott. Nachr., 1857 ; Baur, A., in Miill. Arcb, 1857 ; Eiidinger, Die Gelenknerven d. Menscbl. Kbrpers Erlangen, 1857 ; Vircbow, in Verbandl. d. Wurzb. pbys. Med. Ges. Bd. 1, Nr. 13 und Enters, iiber die Entw. d. Scnadelgrandes, Berlin, 1857 ; Freund, W. A., Beitr. Z. Norm, u. Patb. Histolog. d. Eippenknorp)el, Breslaw, 1858 ; Muller, H., in Wiirz. Verbandl., 1858 ; Aeby, C., in Zeitsobr. f. rat. Med. Bd. iv, 1858 ; Ollier, L., in Jour, de la Pbysiol. vols. ii. and iii., in Gaz. Medic, de Paris, 1859 ; Beale, Lionel S., tbe Structure of tbe Simple Tissues of tbe Human Body, 1861 ; Lieberkubn, N., in Berl. Monatsber aus-dem Jabre, 1861 ; Welcker, H., Enters, iib. Wacbstb. u. Bau. d. Menscbl. Scbadels, Leipzic, 1862 ; Bucbbolz, R. in Yircb. Arcb. ; Strassman, F. Nonn Obs. ad ossium increment, pert. Berol. 1862, Diss. ; Eomer, H. W. z. Entwickl. d. Ellbogengelenks Marb. 1863, Diss ; Volkman, in Vircb. Arcb. und Deutsche Kbnik, 1864 ; Beale, L., On tbe Structure and Groirtb of tbe Tissues and on Life, 1865 ; Rauber, A., Vater-sche Korpercben der Bander, und Periostnerven, 1865, Diss ; Robin, in Journ. de I’Anat. et de la Pbysiol. und. Gaz. iMed. 1865 ; Gegen- baur, C., in Jenaiscb. Zeitscbr. ; ElFelmann, in Deutcb. Klinik. 1864, und Anat.-Cbir.- Stud. ad. Beitr. z. d. Lebre v. d. Enocben jug, Indiy. Hameln. 1865 ; Hutcr, C., in Vircb. Arch.; Kubne, Physiologiscbe Cbemie, 1866 ; Quain and Sbarpey’s Anatomy, 1867 ; Frey, Histologic and Hisfocbemie, 1867 ; Eeber die innere Architectur der Knocben und ibre bedentungs fiir die Frage vom Knocbemvacbstbum, Dr. Jubus Wolff, Virchow’s Archiv. Band 50, 1870 ; Beale, L., on tbe formation of Lacunae and Canabcub, Archives of Medicine, No. xvii, 1870. CHAPTER VII. OF ADIPOSE TISSUE. THE ADIPOSE TESICLE. VESSELS OE ADIPOSE TISSUE. OE EAT. DISTEIBUTION OE ADIPOSE TISSUE. ORIGIN AND PRODUCTION OE EAT. OE THE REMOVAL OE ADIPOSE TISSUE, AND THE ABSORPTION OE EAT. — ABNORMAL DEVELOPMENT OE ADIPOSE TISSUE. This tissue has no alliance either of structure, function, or composition with the areolar tissue, but it is usually associated with it. Malpighi, W. Hunter, l\Ionro, and, more recently, other distinguished anatomists, have pointed out the distinct- ness of these two tissues. Adipose tissue may he very rapidly formed and removed. It may he regarded as one of the lower simpler tissues of the body. An individual may experience the greatest alterations in regard of the amount of adipose tissue in his organism, and change may even occur several times during life, without any serious derangement of the health being necessarily occasioned. This tissue is found in connection with many textures of the body besides the areolar or connec- tive. Bone, glandular organs as the mammary glands, the liver, and pancreas usually exhibit more or less adipose tissue. A com- mon use of this tissue being to occupy spaces of various dimen- sions left in the interstices between organs, and thus to facilitate motion and contribute to symmetry, it is very commonly closely associated with the areolar tissue ; but the connection is not an essential one. In the cancelli of bones there is a large deposit of fat, but no areolar connective or filamentary tissue ; and in numerous situations, as the eyelids, beneath the epicranial aponeurosis, between the rectum and bladder, under the mucous membranes, and in the whole of the cutis, the areolar tissue exists without being ever accompanied by fat. A distinction is to be drawn between the fat and the adipose tissue. Under the latter head may be comprised a greater or less proportion of areolar tissue (in the meshes of which the adipose vesicles with them contained fat are situated), vessels, which ramify very freely, and a few nerve fibres distributed to the 292 THE AHIPOSE VESICLE. A fat cell after SchwaiiD, showing the bioplasm or nucleus, d, and the mem- brane, c latter. The fat is the material contained within the vesicles, fig. 189. The Membrane of the Adipose Vesicle does not exceed the Soioo of ^’^oh in thickness, and is quite transparent. It is moistened by watery fluid, for which, as Mr. Paget has suggested, it has a greater attraction than for the fat it contains. It is perfectly homogeneous, having no appear- ance of compound structure, and consequently belongs to the class of simple or elementary membranes. Each vesicle is complete in itself ; is from the to the of an inch in dia- meter, when fully developed ; and is supplied on its exterior with capillary blood-vessels, having a special disposition. MTien the fat of adipose tissue is absorbed, the vesicles shrink somewhat but remain, and it is probable that fatty matter may be removed from and subse- quently be deposited in the very same fat vesicle. The fat vesicles are usually found in great numbers together, and as they increase in dimensions they become flattened on their contiguous aspects, and assume a polyhedral figure more or less regular, as may be noticed in ordinary suet, fig. 190. But, if isolated, their form is roimded, as may be seen in eminent beauty in the double series of them which fi.-equently accompanies the minute vessels traversing membranous expansions of the areolar tissue, and other structures, particularly the mesentery of small animals. The vessels are thus attended by fat vesicles, for the manifest purpose of protection from the pressure to which they would be exposed in their open course, and they throAV aroimd each vesicle a capillary loop, fig. 194, pi. XX. Where the adipose tissue is in considerable quantity, it is commonly subdivided uito a number of small fragments or lobules, fitted accurately to one another and invested with areolar tissue, for the purpose, chiefly, of permittmg motion Pig. 190. Fat vesicles, assuming the poly- liedral form from pressure against one another. The capillary vessels are not represented. —From the omentum ; magnified about 800 dia- meters. VESSELS OF ADIPOSE TISSUE. 293 bet-ween the parts of the mass, but, also, for the convenience of the distribution of its blood-vessels. Vessels . — In fig. 194, pi. XX, the vessels of a lobide of adi- pose tissue are represented, the artery being coloured red and the vein blue. The blood-vessels enter the chinks between the lobules, and are soon distributed through their interior, under the form of a solid capillary network, whose vessels occupy the angles formed by the contiguous sides of the vesicles, and anastomose with one another at the points where these angles meet. This is one of those situations where the capillary vessels can be most unequivocally proved to possess distinct membi'anous parietes. Fat is a white or yellowish soft substance, exhibiting no structure whatever, entirely unorganized. The chemical com- position of fats has been very carefully studied, but there is still some difference of opinion among chemists concerning the exact nature of the components of fat. By decomposition fatty acids, principally palmitic, and stearic, may be separated from human fat. These were in combination with glycerine to the elements of which they seem to have been united as to an organic base. By boiling oil or fat with a solution of caustic alkali, the acids unite with the potash, forming soap, and the glycerine remains dissolved in the liquid. By evaporating this liquid (in which any excess of alkali had been previously neu- tralized by tartaric acid) to a thick syrup, the glycerine may be separated fi’om it by solution in strong alcohol, but this sub- stance is now obtained by another process in an exceedingly pure state. It is manufactured upon an enormous scale by Messrs. Price and Co., and is much used. Its value as a medium for preserving microscopical preparations is great. See page 58. We may often detect a spontaneous separation of the crys- talline from the oily fat within the fat vesicle of the human subject. The solid portion collects in a spot on the inirer sur- face of the cell-membrane, and looks like a small star, fig. 191, h h b. The elaine occupies the remainder of the vesicle, except when the quantity of fat in the cell is smaller than usual; in which case we may often discern a little aqueous fluid between the elaine and the cell-membrane on the side farthest fi’om the star (fig. 191, a a) ; a coirdition, by the way, which is very 294 COMPOSITION OF FAT. favourable for the demonstration of the membrane itself. The Fig. 191. fatty matter contained in the fat vesicle, even in the case of very hard fats like suet, is always in a soft liquid state while the body is alive. The softer kinds of fat were denomi- nated by the older anatomists pinguedo, lard ; and the more sohd sehum or sevum, suet, tallow. Hrmter distinguishes fom- 86 ° F. Tallow at 104° F. Spermaceti is fluid in a heat above 115° F.,and solid at 112 °. Oil is elaiue with little or no stearine, as the neat’s foot oil, obtained from the hones of the ox. Ill lard, the stearine is in abundance, but the elaine slightly predominates. In tallow there is a predominance of steaiine. Ileintz showed that human fat contahied tripalmitin, from which palmitic acid may be obtained by saponification. The other constituents of human fat are stearine and elame. The acids are the palmitic^ stearic, and oleic. The composition of the fatty constituents in human fat is as follows : — Tripalmitin, CjoaHggOis: which corresponds to thi'ee equivalents of palmitic acid 3 (C 32 II 32 O 4 ) -I- one equivalent of glycerine (CgHgOg) — 6 HO. Tristearin, Ci, 4 HiioOj 2 , which represents three equiva- Fig. 192. Fig. 193. Stearine. After RoHn and VerdeiL DISTRIBUTION OF FAT. 295 lents of stearic acid (CggHggO^) + one equivalent of glycerine (CgHgOg) - 6HO. Triolein, wliicli corresponds to three equivalents of oleic acid (CggHg^O^) + one equivalent of glycerine (CgHgOg) — 6H0. Human fat according to Chevreul, consists of Hydrogen .. 11-416 Carbon . . 79-000 Oxygen 9-584 100-000 Distribution . — The adipose tissue is met -with very exten- sively in the animal kingdom. It is found in larvae as well as in the perfect insect ; also in the inollusca. It prevails in all the tribes of the vertebrata. In fish it occurs throughout the body ; hut in some, as the cod, whiting, haddock, and all of the ray kind, according to Hunter, it is only met vdth hi the liver. In reptiles it exists chiefly in the abdomen. In the frog, toad, &c., it is found in the form of long appendages, something like the appendices epiploicm of man, situated on each side of the spine. In birds, it exists chiefly between the peritoneum and abdominal muscles ; but there is also a considerable deposit in the bones of the legs, feet, last bones of the ufings, and of the tail, especially of the swimming tribes, the oily principle being more abundant than in mammals. In mammalia it is very generally diffused. This class, as a whole, has the greatest quantity under the skin, and about certain of the abdominal viscera ; but the hare forms a remarkable exception, it being sometimes difficult to find a particle of adipose tissue in the whole body. It usually abounds most in the beginning of winter ; and this is especially the case with the hog, and with hybernating animals, which, dmang their dormant state, absorb it into the system. It is ordinarily accumulated in large masses about the kidneys, more particularly in ruminants, where it furnishes the best example of that variety of adipose tissue termed suet. Among mankind many I’emarkable Amrieties exist as regards this tissue. In general, Avomen are fatter than men. The healthy human foetus, after the middle of the period of gesta- 296 ACCUMULATION OF FAT. tion, accumulates fat in considerable quantities ; towards middle age, there is a similar disposition, which has not escaped or- dmary observation, “Fat, fair, and forty.” In old age and decrepitude, the adipose deposit greatly diminishes. Differences are also constantly seen in individuals, which can be referred only to an original constitutional bent. Thus young children are occasionally so overloaded with this tissue as to be unable to follow their sports ; and it is not uncommon for a similar tendency to manifest itself towards the adult period, particularly in girls. In elderly persons, fat is especially prone to be accumrdated over the abdomen, and betAveen the layers of the epiploon and mesentery. Instances where it attains the thickness of three or four inches rmder the skin of the belly are not unfrequent in corpulent persons. A similar abundance occasions the “ double chin.” On the other hand, there are certain individuals who cannot be made fat. Xo matter in what manner the diet may be changed in quantity or quality, there are persons whose adipose tissue cannot be in- creased. It is perhaps possible for the body to grow so egregiously fat as to become lighter than water ; but whether implicit faith is to be placed in the stoiy of the Italian priest Paolo Moccia, who Aveighed thirty pounds less than his bulk of water, and therefore could not sink in that fluid, we do not pretend to decide. The excessh^e deposit of this substance constitutes a disease, which has been not A^ery correctly called polysarcia. John Bull is celebrated for his proneness to accumulate fat ; M. BlainAulle remarks, with naivete, “ We haA^e seen many indi- viduals of the English nation whom embonpoint had rendei'ed almost monstrous ; and I remember among others, a man exhibited at the Palais Royal who AA-eighed fiA'e himdred poimds. He was literally as broad as he AA^as long.” But this tendency is by no means peculiar to Englishmen. Among the Hottentot women, the fat is apt to gather in the buttocks, and is considered a prominent mark of beauty ; but this does not usually occur till after the fii’st pregnancy. A somewhat analogous formation exists in a A'ariety of sheep,* reared by the pastoral tribes of Asia, in which a large mass of fat covers the buttocks and takes the place of the tail, appear- * Oi'w fat-buttocked slieep. Pallas. PRODUCTION OF FAT. 297 ing when viewed from behind as a double hemisphere, in the notch of wliich the coccyx is buried, hut is just perceptible to the touch. These protuberances, when very large, fluctuate from side to side, and sometimes attain the weight of thirty or forty pounds. The quantity of fat in a moderately fat man is estimated by Bedard at about the twentieth of the weight of the body, but in many it amounts to much more. Fat is found in the following situations in the human body ; in the orbits, in the cheeks, the palms of the hands and soles of the feet, at the flexures of the joints, and between the folds of the synovial membranes of joints, around the kidneys, in the mesentery and omentum, in the appendices epiploicse, on the heart, in the subcutaneous layer of areolar tissue, but especially that of the abdomen, and of the mammary region, and in the cancelli and canals of the bones forming the medulla. It never occurs in the areolar tissue of the scrotum and penis, or of the nymphse, nor in that between the rectum and bladder, nor along the median line beneath the skin, nor in sundry other situations. Fat is found in the liver even in health, and a large quantity may be obtained from the brain and nerves. In these organs it is not enclosed in vesicles of delicate membrane, but is asso- ciated with the matter of the tissues themselves. Oily matter exists in greater or less proportion m all the textures of the body, fi’om which it may be extracted by alcohol and ether, although not a trace can be detected by microscopical examination. Seepage 146. Even the transparent fluids of the organism are not destitute of fatty material, and, as is well known, the chyle contains a very considerable proportion. Origin and Production of Fat . — There can be no doubt that fat is derived from the blood. All the most recent analyses of that fluid assign to it a certain proportion of both the crystallisahle and the oily portion of the fat; according to Lecanu, about four parts in a thousand. In many instances, the fatty matter accumulates in the blood ; cases of which have been recorded by Morgagni, Hewson, Marcet, Traill, and Babmgton. In such cases the serum is opaque and nearly as wlnte as milk, and, on standing a short time, a film forms on the surface like cream. On the addition of ether, the creamy pellicle is dissolved, and the serum loses its opacity. M. Blainville relates, that, in 298 FATTY MATTER IN THE BLOOD, dissecting tlie last elephant that died in the Jardin des Plantes, he happened to wound the jugular vein, and the next morning he found that the stream of hlood, which flowed from the vein, had deposited on each side a considerably quantity of a free fatty matter, which on analysis he found to have exactly the compo- sition of ordinary fat. A similar fact may he often observed in the hlood from slaughtered animals, which we find to be sometimes loaded with fat. From what source is this fatty material famished to the blood ? Mahily, no doubt, from fatty matters introduced into the system in the food, whether animal or vegetable substances, hut fat may be formed, and in considerable quantity, from nuti’ient materials winch do not contain it. F rom many non-nitrogenized articles of diet, starch, gum, sugar, alcohol, beer, fat may be formed, and in large quantity, by the agency of the bio- plasm of the body. From the constituents of meat and other nitrogenous foods, fat may also be formed in the or- ganism. If the system be imperfectly supplied with oxygen, while organic compounds containing carbon are furnished to it in considerable quantity, the most favomable conditions will exist for the develojnnent of fat. On the other hand, exercise and labour, winch increase the supply of oxygen, diminish or prevent the formation of fat. “ The production of fat,” says Liebig, “ is always a consequence of a deficient supply of oxygen, for oxygen is absolutely indispensable for the dissipation of the excess of carbon in the food. This excess of carbon, deposited in the form of fat, is never seen in the Bedouin or in the Arab of the Desert, who exhibits Avitli pride to the traveller his lean muscular sinewy limbs altogether free fi’om fat ; but in prisons and jails it ^ipears as a puftiness in the inmates, fed, as they are, on a poor and scanty diet; it appears in the sedentary females of oriental countries ; and, finally, it is produced under the Avell-knoAvn conditions of the fattening of domestic animals.”* A good illustration of these views is afforded by the carni- vorous animals. In the wild state, Ihung entirely on azotised food, and enjoying abundance of air and exercise, they are lean ; but, Avhen domesticated, liAung on a mixed diet, taldng * Liebig’s Organic Chemistry. ADIPOSE TISSUE. Fig. 194. PLATE XX. Blood vessels of adipose tdssae. Artery red. Vein blue. A is a minute lobule in whicli the vessels only are represented, a. terminal artery, r. the primitive vein. 6, fat vesicles at edge of a lobule as seen in an uninjected specimen, x 100. B. Plan of the arrangement of the capillaries around the vesicles, more highly magnified, p. £93. Fig. 195. Fig'. 196. Fig. 197. Connective tissue corpuscles in which fatty matter is being deposited, a- The latter in some cases increases until a body like a fat vesicle results. X 215 p. 303. Fat bioplasts from the frog, showing the mode of format Lion of the oily matter. The youngest one is at the top. The vesicle is so thin as to be not yet visible, x 700. p. 300. Cartilage from the ensi- form cartilage of a young white mouse, showing the deposition of fatty ma'tter in the bioplasm. X 700 p. 302. Fig. 19S. Fat vesicles of various sizes from the growing adipose tissue of the frog. As the fatty matter accumulates, the bioplasm is pushed to one side and in many cases passes unobserved, unless it is coloured, x 215. p. 302. To'oo of an inc'n X 215. inoo of an inch X 700. [To face page 298. DEVELOPMENT. 299 little exercise, and being imperfectly supplied with oxyg’en, they gTow fat. In animals that hybernate, fat is deposited in enormous quantity just prior to the hybernating period, and during that time it gradually disappears, supplying nutriment to the sys- tem, and carbon for the respiratory process. These facts were clearly ascertained in hedgehogs by the celebrated Dr. Jenuer. It is generally admitted that the disintegration of fat is attended with the development of heat, the oxygen mriting with the carbon, an amount of heat is generated proportionate to the quantity of carbonic acid formed. But it may be fairly questioned whether the high temperature of the body can be thus explained, seeing that in many conditions in which the temperature rises many degrees within a very short period of time, the oxidising process is completely at fault, and the quantity of oxygen consumed is far less than in health. Although ordinarily much fatty matter is concerned inchrectly in the changes which take part in the development of animal heat, the large amount of fat existing in every form of nerve tissue clearly shows that the action of the nervous system so essential to the maintenance of life is in some way dependent upon the due supply of a sufficient quantity of nutrient mate- rial containing the elements from which fat may be formed. Lastly, fat being a bad conductor of heat, is usefol for re- taining it in the bodies of animals. Those animals that have little hau- on their skins, and are at the same time exposed to the mfluence of extx’eme cold, have a great quantity of sub- cutaneous fat. This is remarkably the case in the whale tribe, most of which have a thick layer of adipose tissue (blubber) between the smooth bare skin and the muscle beneath. In man, the subcutaneous fat, which is so generally met with, even in apparently lean subjects, is doubtless a most valuable protec- tion against the cooling effects of arctic cold. The Developrnerit of Adii^ose Tissue . — The process of forma- tion of adipose tissue may be studied m the embryo of any vertebrate animal. Long before fat is actually produced, the embryonic matter (bioplasm) which is to take part in its formation can be distuiguished from that Avhich is to give rise to other textures. But the several stages through which adipose tissue passes in its development may be as clearly X 300 THE develop:mext made out in any young mammal at the time of its birth as during the earlier periods of development. And there is this advantage in conducting the examination at this later time, — that fully-formed adipose tissue may he contrasted with the same texture in its embryonic state in the same micro- scopic specimen, for the development of this tissue continues long after birth. Nay, in certain cases it may be studied in an embryonic condition even in the adult. Thus we have obtained excellent specimens which illustrate every stage of the process, taken from the fidly formed frog. PL XX, figs. 196, 198. Indeed, in hybernating animals new adipose tissue is formed just prior to each recurrent period of hybernatiorr, but it is probable that in some instances fatty matter is also reformed in the very same old cells from which it had been previously removed. It would be supposed that a tissue which altered its volume' so quickly and to so great an extent as this, would have a very intimate relationship vith the blood from which the elements entering into its formation are derived, — and this is the case, for adipose tissue is very largely supplied with blood, and in corpulerrt persorrs who make fat fast, the greater part of the blood of the body is probably distributed to the adipose tissue, arrd other tissues and orgarrs suffer in nutrition. The muscles become weak, and waste, and the nerwes are impaired. Vessels, arteries, capillaries, and veins, are developed pari passu with adipose tissue. And there is not an hrstarrce among vertebrate animals of the occm'rence of adipose tissue destitute of vessels. The vascularity of the medulla or marrow of borres is remarkable. The rate at which adipose tissue grows, in certain cases, is very strikirrg, and probably the animal m which it is produced most quickly is the yoimg pig, Avhose adipose tissue doubles in weight in the course of a very few weeks. In the meshes of the capillary network of very yormg adipose tissrre may be seen the little masses of bioplasm, Avhich are concerrred in the production of fat. These, at a still earlier period, are in contact with the external surface of the vascular wall. It certairrly is not possible to determine by any appear- ance manifested by the numerous bioplasts in the immediate neighbourhood of the vessels, which of them are to take part in the development of new capillaries, and which are to become OF ADIPOSE TISSUE. 301 connective tissue or fat. The 'capillaries themselves multiply as the adipose vesicles grow, and the vascular network increases as in other situations, hy the extension of bioplasts in a loop- like form from the capillaries already existing. The changes taking place in the development of an indi- vidual adipose vehicle will be understood if figs. 196, 198, pi. XX be referred to. At first all that is to be discerned is a small oval or spherical mass of bioplasm or living matter, perfectly naked, that is, entirely destitute of a cell wall. This little bioplast usually e xh ibits one or more new centres of growth (nuclei) embedded in it. The formation of the fatty matter occurs in this way : — in the very substance of the bioplasm, but always outside and away from the new centre or nucleus, a little oil globule makes its appearance. It results from changes in the living matter itself. A portion of this bioplasm dies, and among the substances resulting from its death are fatty matter, which being insoluble, remains, and soluble substances which are carried away in the blood. Starch globules and other secondary deposits formed in the interior of elementary parts are produced in the same manner by the death of the bioplasm. The fatty matter does not come from the blood as fat, and deposit itself in the cell, nor is it formed by the collec- tion and aggregation of excessively minute granules, which traverse the vascular walls suspended in serum ; nor is it pre- cipitated from the nutrient fluid after the manner of crystals. But it invariably results from the transformation of living matter, and different kinds of living matter, as is well known, will pro- duce different kinds of fat. The properties and composition of fat in different animals differ, because the powers of the bio- plasm or li\dng matter of each animal are so different. The bioplasm of the fat-cell does not diminish in proportion exactly as the oil increases, because the conversion of pabulum into bioplasm proceeds as fast as the conversion of the latter into formed material takes place, as has been already explained in page 79. In 1861 one of us showed the relation of the oil or fat to the included nucleus or mass of living germinal matter or bioplasm, and pointed out that the fat of the fat cell and the starch of the starch cell were formed by the bioplasm itself. Nevertheless many who have written since have affirmed that 302 THE DE\T5LOPiIEXT we still remain completely ignorant concerning the relation of the fatty matter to the bioplasm of the cell. By aid of the plan of preparation already referred to, the change in amount of the bioplasm and the relation of this substance to the formed fatty matter may be so distinctly deteiTuined m cells at different stages of development that not a doubt can be enter- tained concerning the mode of formation of the fat, and the true relation which tlie bioplasm bears in all cases to this sub- stance. The little globule of fat having been once fomred in the substance of the bioplasm, pi. XX, fig. 196, may increase in size by the addition of new particles to it, until the globule becomes larger and larger, being at last, perhaps, fifty times the size of the bioplast that remains, fig. 198, pi. XX ; or the number of globules may increase until a compound mass, con- sisting of hundreds of separate little oil globules, results. In most mammalia and man, the globule is single, but m some of the reptiles (lizard, snake, chameleon) the fat cells in many of the tissues consist of numerous se^parate oil globules, almost uniform in size. And in some parts of the organism of some mammalia (rat, mouse), and even in certain cases in man him- self, the same fact has been noticed. In insects the “ fat cells” are often of enormous size, consisting of aggregations of very small oil globules, which collect around the mass of bioplasm that has taken part in their production. In the livers of many fishes, particularly the eel, a someAvhat similar arrangement may be observed. In these cases the nutrient matter passes in tlie interstices between the already formed oil globules to the bioplasm in the centre. The circumferential portions of tlie latter die, and undergo transformation into fatty matter AA'hich is deposited within that already produced. The globules on the outside of the cell or on its surface are therefore the oldest. To recur to the development of the adipose vesicle in man. At the same time that the oil globule deposited in the bio- plasm of the developing adipose tissue increases, a change of another kind is taking place upon the surface of the mass. The living matter in this situation dies and becomes changed. BO as to form a delicate transparent structureless membrane, Avhich mcreases in extent as its contents become augmented by the absorption of nutrient material into the included bioplasm. OF ADIPOSE TISSUE, 303 and its appropriation. The so-called wall of the adipose vesicle is therefore formed in accordance with the mode of production of formed material generally. But the wall of the adipose vesicle is of excessive tenuity, and readily permeable to fluid in both directions, so as to allow for the very frpe passage of nutrient material to the bioplasm within and that of fluid resulting from the changes of the bioplasm in the opposite direction towards the blood. In this way the rapid increase and removal of adipose material is rendered possible. But the mode of development of fat may be studied in other textures besides the adipose tissue itself. Thus, in con- nective tissue it is sometimes found that fatty matter is formed in the bioplasm of the connective tissue corpuscle, and an elementary part at length results which closely resembles an ordinary fat cell. Some connective tissue corpuscles from the fi’Og are repre- sented in flg. 195, plate XX, magnified 700 diameters. In the upper one an oil-globule is seen, and in many parts of the preparation from which the drawing has been made, connective tissue corpuscles were seen Avhich illustrated every stage of change up to the formation of a fat cell, resembling that of ordinary adipose tissue. Some observers, indeed, consider that the adipose tissue is not a distinct texture at all, but that the fat cell is developed from the corpuscles of connective tissue — a view which is cer- tainly erroneous, for, in many cases, at an early period of development, collections of bioplasts can be detected -without difficulty, in relation with which not a trace of connective tissue can be found ; while around the vessels of the mesentery of young annuals the bodies in question are seen as well as the corpuscles of the connective tissue of the mesentery, but quite distinct from them. While, therefore, it is certain that the connective tissue corpuscle, the cartilage, and some other elementary parts, may be transformed into fat cells, it is also an unquestionable fact that, in the development of adipose tissue special bioplasts are concerned which are quite distinct from those engaged in the formation of connective tissue. The bioplasm of cartilage in highly fed animals often pro- duces oil globules which accumulate in the so-called cartilage cell, and the bioplasm becomes pushed to one side, and so 304 REMOVAL OF ADIPOSE TISSUE. compressed tliat it may entirely escape notice. In the young mouse such a change is commonly observed, and, not unfre- quently, the fat accumulates to such an extent that the tissue might almost be described as adipose tissue, in 'which the ordinary vesicle or cell 'wall is replaced by firm cartilag-inous tissue. In fig. 132, pi. XV, is represented a small portion of the cartilage tissue of the thinnest part of the ear of a young ■white mouse. Each spherical capsule of cartilage tissue is occupied by a large oil globule, bet'iveen 'which and the inner Avail of the capsule the remains of the bioplasm that has taken part in tlie formation of both fat and cartilage may be dis- tinctly seen if the specimen has been properly prepared by previous soaking in carmine fluid, page 6U. In fig. 197. pi. XX, two “cells” from the ensiform appendix of the Avlfite mouse are figured, in Avhich fatty matter is being formed. That condition which is termed fatty degeneration of the liver, and which is very common in phthisis also affords a good illustration of the changes winch occnr when fat is formed. To such an extent does the change sometimes proceed, that a sec- tion of the fatty liver could not be distinguished fi'om certain forms of adipose tissue. Not a particle of biliary colouring matter or other e\fidence by AATich tlie real nature of the tissue may be identified remains. In some adult fishes tliis is the ordinary condition of the hepatic organ, and without great care in the preparation of specimens, not a vestige of hepatic tissue will be discoAmred. In all these instances, however, the stages tlu'ougb A\diich the gland-elementary part passes may be stuched without difficulty, and specimens may be obtained AAdiich sIioaa* eA’ery degree of alteration, from a transparent elementary part, completely destitute of fatty matter, to a body which appears to consist only of a huge oil-globide. It is surprising how large an accumulation of fat may occur in the INer in some of these cases. As much as 65‘19 per cent. Avas found by one of us (L.S.B.) in one case, recorded by Dr. Budd.* Of the removal of Adipose Tissue and the absorption of Fat . — Not less interesting than the consideration of the mode of deAmlopment of adipose tissue is the question concerning the manner in which its removal is effected. It is well known that large quantities of fat Avhich liawe been stored up in the body * “ Diseases of Hie Liver,” 2ud eel., p. 284. ABSORPTION OP FAT. 305 and have been collecting for a considerable time, may quickly disappear, in consequence of the fat being absorbed, and its elements applied to assist in the nutrition of tissues whose waste coidd not occur without consequences very damaging to the organism, and in maintaining the requisite temperature. The adipose tissue may, indeed, be regarded as a sort of storehouse, in which fat is accumulated as long as the body is abundantly supplied with food,, from which it may be removed and appro- priated, should a period of scarcity occur. In the winter, when the fat of the fat bodies of the frog are being absorbed, the bioplasm of each vesicle can be seen spread- ing around the fatty matter, which gradually diminishes in amount in consequence of its conversion into bioplasm. On the distal side of the vesicle, phenomena of another kind are proceeding. The bioplasm is there undergomg change, and becoming resolved into substances, which are immediately taken up by the bioplasm of the blood and blood-vessels. As has been already described (p. 152), all nutritive operations are conducted through the intervention of bioplasm alone. As every kind of fatty material is formed from bioplasm, so its re- moval is effected only through the instrumentality of this living matter. It cannot be removed until it has been again taken up and converted into bioplasm. Moreover, the same bioplasm is instrumental in both operations : — in the one case taking certain constituents from the blood, increasing at their ex- pense, and then undergoing conversion into fatty and other matters : — in the other, growing at the expense of this fatty matter already produced, and then becoming resolved into sub- stances which find then.' way back again into the blood, and which are at length appropriated in part by other forms of bioplasm of the body. This view has been recently confirmed by Czajewicz, in some observations upon the adipose tissue of rabbits (Reichert and Du Bois Reymond’s Archiv., 1866, p. 289). In animals which have become rapidly emaciated, the fat cells of the adipose tissue are seen to be shrunken, and, instead of containing fatty matter, fluid, with some granules and one or two oil globules, are alone found. This interesting fact was first observed by Kolliker. The amount of fat in an individual vesicle may vary from time to time. The processes of forma- 306 FATTY TUMOURS. tion and disintegration of the fat which has been already formed alternating Mnth one another. Abnormal Development of Adipose Tissue . — The rmiform de- velopment ' of adipose tissue is sometimes distm-hed, and in consequence of a circumscribed redundant growth, a tumour of enormous size may result. It is not uncommon to find this unusual growth sprmging fi-om the subcutaneous adipose tissue of the limbs or trunk. In one particular spot the circumstances which determine the regular and even growth of the tissue are somehow altered, and growth having once bm’st its ordi- nary bounds, continues unce^i^mgly, and often at an increasing rate, until a tumour of large size is produced. The structure of simple fatty tumours exactly accords with that of normal adipose tissue, and the arrangement of the capillary vessels is precisely the same. It is possible that the fonnation of these tumours may be due to the circumstance of a collection of bioplasm, which would under ordinary conditions, form a lobule of ordinary adipose tissue, being displaced at an early period of its development. Subjected to the influence of unusual conditions, the little lobule grows very quickly, and once but a germ, soon becomes developed into one of those, often huge, morbid growths. Not only is the constantly growdng fatty tumour like adipose tissue in its general characters, but in many instances the minute structure of the morbid growth could not he distin- guished from that of the normal tissue.