CORNELL UNIVERSITY. THE Roswell P. Flower Library THE GIFT OF | ROSWELL P. FLOWER FOR THE USE OF THE N. Y. STATE VETERINARY COLLEGE. 1897 ft Ta CATECHISM SERIES. a Jha ez! sy at PHYSIOLOGY: | oer ‘ “Op e 4 F ~ LIBRARY, ~ s sis “p, i 6 Ss ATE VEL: CHIEFLY HISTOLOGY, a EDINBURGH: Boos SS, -LIVINGS FONE, 1892. & Q 1 PRINTED BY ; 4. oO E. & 8. LIVINGSTONE 4 MELBOURNE PLACE Py 7 EDINBURGH ‘usp Dre wa eo 4. Se | i ARY, PHYSIOLOGY.\e, YS are ve PART I. Name the Elementary Tissues. 1. So Ou C2 BS 7. Blood and lymph corpuscles (= cells suspended in a fluid intercellular matrix). Epithelial tissue. Connective tissue. Adipose tissue. Dental tissue. Muscular tissue. (a) Striped. (6) Non-striped or plain. Nerve tissue. Name the Connective Tissues. 1. Cartilaginous tissues. 2. Mucous tissue. 3. Retiform tissue. 4. Ordinary Connective tissue. 5. Bone, or Osseous tissue. What ts an Organ? It is an assemblage of two or more elementary tissues. What are the Parts of the Blood ? 1. The Plasma, or liquor sanguinis (not serum). 2. The Corpuscles, suspended in the plasma. 4 What are the Varieties of Coxpuscles ? Chiefly two— 1. White or colourless. 2. Red or coloured. What are the Special Features of the White Corpuscles? They consist of— 1. Nucleated masses of amceboid granular protoplasm. 2. They have no apparent envelope, as the processes they protrude may be observed to fuse at their apices, when they happen to collide: their shape, therefore, is indefinite. 3. Usually three nuclei. 4, Size yd5o to qeyo of an inch—or from the same size to twice the size of the coloured corpuscles, 5. They are inelastic and viscous, and tend to cling to the sides of the vessel. 6. They are lighter than the red corpuscles, 7. They envelop and eat solid particles. What ts the Granular Appearance supposed to be due to? It is due to a fine intercellular network, having small dots at the intersections of the net; these form the larger granules, while the fibres of the net seen endwise form the small granules. In the meshes of the network is a hyaline substance, What do you mean by “ Amceboid” Movements ? The movements are called amceboid because they are typically seen in the amceba. The movements consist in a protrusion of processes of protoplasm, which are again retracted, and other processes protruded. In this way the corpuscles can migrate from place to place, or even pass through the walls of capillaries into the surrounding tissues. What is this last Called ? It is known as DrIapPEpEsis. Who first Discovered this ? Augustus Waller in 1846, and again by Cohnheim in 1867. — This emigration is best marked during the process of inflam- mation. How are these Movements best Studied ? ‘The blood should be examined on a warm stage (100° F.). They only move so long as they are alive. During life they move, and are of indefinite shape; when dead they do not move, and are then circular in shape. The movements are said to be due to contractility of the protoplasm. How can the Nuclei be Shown ? By treating them with dilute acetic acid, or a dilute solution of a caustic alkali; by this means the protoplasm is rendered exceedingly transparent, and the nuclei are thus brought into view. What has the Entanglement of Solid Particles by the Corpuscles been used to prove ? It was made use of by Cohnheim to prove that many of the pus cells in inflamed areas are emigrated white blood corpuscles. Pus cells are also identical in structure with white blood corpuscles. What do you mean by the term “ Leucocyte?” It is a term applied to lymph cells (young white blood corpuscles), white blood corpuscles, wandering cells of con- nective tissue, and pus cells. What are the Special Features of Human Red Blood Corpuscles ? 1. They are circular bi-concave discs, but have no ameeboid movement. Red in mass, but pale yellow when seen singly. 2. They have a thin, clear, soft, extensible, but perfectly elastic envelope; they therefore do not protrude processes of protoplasm (pseudopodia), and their shape is definite. 3. They have no nuclei. 4. Size, as an average 5,45, of an inch. 5, They are extensible and perfectly elastic, and have a smooth non-viscous surface, and readily glide past each other in the blood-vessels. 6. They are heavier than the colourless corpuscles—sp. gr. 1088. 7. They do not envelop nor eat solid particles. Seen edgewise they are flattened and biconcave; seen. lying on its broad surface, the corpuscle has a shadowed centre surrounded by a light ring. What ts the Colouring Matter called ? It is called hemoglobin, and lies in the sponge-like mesh- work of the cell. Compare the Coloured Corpuscles of Man and the Lower Animals. In man, and all mammals, they are circular and bi-concave discs (in the camel they are oval) and have no nuclei. In all other vertebrates they are oval and bi-convex, and are nucleated. What happens when Blood is drawn ? The red cells tend to run together into piles or RoULEAUX. This is specially seen in inflammation. What is it due to ? The running together is said to be due to capillarity, the result of their partial submersion ; the running into rouleaux being due to their shape. What is the Composition of the Corpuscles ? They contain Water, Solids, and Gases. What ure the Solids ? 1. Heemoglobin, 2. Paraglobulin. 3. Lecithin. 4. Cholesterine. 5. Salts. What is the Composition of Hemoglobin ? It is an albuminoid substance, very complex, and consists of C.H.O.N.S.Fe. It forms 90 per cent. of dried red corpuscles, and is soluble in water and serum. Is t¢ Crystalline or Amorphous ? It is crystalline. In man it forms elongated rhombic prisms, octahedral in the guinea-pig, and hexagonal in the squirrel, What is its Chief Use ? It forms a loose compound with oxygen (independent of the oxygen in its composition), and acts as the chief oxygen carrier from the lungs to the tissues. It is therefore essential for the respiration of the tissues, It thus exists in two forms, oxy-hemoglobin and reduced hemoglobin. What are the Salts of the Red Corpuscles ? The salts are principally Potasstum Satts—Chloride and Phosphate. In what other Tissue do we find the same thing ? In Muscle. What Salts do we find in other parts of the Body ? In the serum of the blood, and in the other tissues of the body we chiefly find the salts of Soprum, not potassium. Note these facts— In the red blood corpuscles and muscles, potassium salts, In blood serum, and in other tissues of the body (except muscle), sodium salts. 8 How are the Red Corpuscles Developed ? They are all developed from the mesoblast. First Way.—The nuceli of certain cells multiply, and then this multi-nucleated mass differentiates into a central mass of nucleated young red blood cells, while the outer part becomes the wall of the future capillary. To form blood-vessels, pro- cesses grow out from this wall, at first solid, but become hollow and filled with plasma and corpuscles. Sreconp Way.—A vacuole forms in the centre of the multi- nucleated mass, and this forms the interior of the vessel, and is filled with plasma. The nuclei in the wall of the vacuole proliferate, and with some protoplasm grow in as buds and drop off as corpuscles. It will be observed, therefore, that all red corpuscles are at first nucleated. What are the Probable Sources of the Red Cells in the Feetus ? Before the development of the liver and blood glands, red blood corpuscles are produced— : 1. Directly from the mesoblastic cells. 2, From white blood corpuscles. 3. By fissiparous division of themselves throughout the body generally. What is the Fate of the Red Cells ? They are probably broken up in the spleen, from whence the pigment is conveyed to the liver to form the bile-pigments. Gwe the Number of Corpuscles both Relative and Absolute ? In the blood generally, the colourless are in the proportion of 1 to 500 of the coloured. A cubic millimeter of blood contains five millions (5,000,000) of coloured corpuscles, and about 10,000 colourless. 9 Mention some Exceptions and Variations. In the splenic vein, - lwhiteto 70 red. In the splenic artery, - 1 white to 2260 red. In the hepatic vein, - 1 white to 170 red. In the portal vein, - lL white to 740 red. In leucocythemia the white are very much increased ; and so also are they increased after a meal. What are the Functions of the Corpuscles ? The Rep are oxygen carriers from the lungs to the tissues by means of the loose combination between the hemoglobin and the oxygen. The Wuite produce the red, and in some cases may emigrate from the vessels and take part in the formation of new tissues. What is Epithelium ? It consists of cells placed on free surfaces, with a very small amount of intercellular substance. What are its Functions ? 1. Protective— (a) Protects skin and mucous membrane, and forms appendages, as hair and nails. (0) Protective, and moving on ciliated surfaces. (c) Protective, and secreting, as in the intestine. 2. It gives a smooth polished surface to serous and synovial membranes, blood and lymph vessels, and thus reduces friction. 3. It forms the secreting elements of all glands except blood glands. 4. It forms the terminal end organs for the nerves of special sense in the nose, mouth, and ears. How is it Developed ? It is developed from all three divisions of the blastodermic membrane. . 10 From the Epreiast we have the epithelium of the— Skin, mouth, nose, pharynx, cavities of the brain, and spinal cord. From the Mzsostast, the epithelium of the— Blood and lymph vessels, serous and synovial mem- branes, and the greater part of the genito-urinary organs. From the Hyposuast, the epithelium of the— Alimentary canal and glands, below the pharynx, lungs, and urinary bladder. Name the Varieties of Epithelium. 1. Squamous— (a) In several layers—stratified. (b) In a single layer—simple squamous epithelium, or endothelium. 2. Columnar. 3. Transitional. 4, Ciliated. 5. Glandular, or Spheroidal. Where is Stratified Squamous Epithelium Found ? Skin, alimentary canal above the stomach, anterior surface of the cornea, the conjunctiva, vagina, and lower half of the cervix uteri; also in the entrance to the nose and urethra. How are the Cells Arranged ? The Upper ones are flattened. The Mivpiz are more or less rounded. The Lowest layers are somewhat columnar. Where is Simple Squamous Epithelium Found ? In serous and synovial membranes, the heart, blood and lymph vessels, air vesicles of the lungs, posterior surface of the cornea, and the outer surface of the retina. 11 How are the Outlines of the Cells rendered Visible ? By the silver process: the fresh epithelial surface is treated for two or three minutes with a dilute solution of silver nitrate. After exposure to light, dark lines appear mapping out the, margins of the cells. The cement between the cells reduce the silver more rapidly than the cells, and hence the dark lines. Compare the Cells in Artertes, Veins, and Capillaries. In an Arrsry the cells are elongated, and the edges are not wavy. In a Vern the cells are not so elongated, and the edges are wavy. In a Capituary or lympathic the cells are very much elongated, and have remarkably sinuous outlines. Name the Serous Membranes. 1. Tunica Vaginalis of the Testicle. 2. Arachnoid Mater. 3. The Pleure. 4, The Peritoneum. 5. The Pericardium. Where is Columnar Epithelium Found. In the alimentary canal below the cesophagus, and ducts opening into it, including the gall bladder; in the olfactory region of the nose, the urethra, and the vas deferens. It exists as a single layer everywhere except in the urethra, where it is stratified. What is Peculiar about that found in the Intestine ? There is a clear band at the free end of the cell; this clear hem is traversed by fine vertical strie. Magenta stains the general cell substance but not the hem. { 12 What tukes place when Fresh Cells are placed in Water ? Clear blebs of mucin appear at the broad ends of the cells. This shows that the ordinary cells produce mucus. What are the Chalice, Goblet, or Cup Cells ? They are large cells found between the ordinary epithelial cells. At the free end is a large open mouth communicating with a large cavity ; the upper part does not stain with magenta. They are much larger than ordinary columnar cells. Where are they Found ? They are numerous in the small, but particularly so in the large intestine, a point of great importance in “ spotting” cross sections of the mucous membrane of the large gut. What is their precise Nature ? There are two theories— 1. Some say that they are merely old columnar cells under- going mucin transformation and breaking down. Their large size is against this view. 2. Others suppose that they are uni-cellular mucin-forming glands. This is the most likely view. Where is Transitional Epithelium Found ? It is found in the urinary bladder, ureter, and pelvis of the kidney. How are the Cells Arranged ? ' They are stratified, and usually arranged in three layers— often known as “ bridges,” “apples,” and “ pears.” 1, Bripegs, are the more or less cubical cells on the free surface. 13 2. Appizs, the middle layer, somewhat pyriform cells, with their broad ends towards the free surface. 3. Prars, the lowest layer, pear-shaped, with their apices towards the free surface, and fitting between the thin ends of the middle layer. Why is the Epithelium Stratified here ? Probably to prevent the absorption of urine into the blood- vessels. Where ts Ciliated Epithelium Found ? I. Respiratory Tract, and parts connected therewith—. . Respiratory region of the nose. . Upper half of the pharynx. Eustachian tubes, and part of the middle ear. . Larynx, below true vocal cords. . Trachea. Bronchi, except the very finest. Air sinuses of the skull. 8. Nasal duct and lachrymal sac. II. Male Genitals. 1, Vasa efferentia, forming the coni vasculosi. 2. Part of epididymis. III. Female Genitals. 1, Fallopian tubes. 2. Body of uterus, and upper half of cervix. IV. Cavities of the Brain and Spinal Cord. NO oP wpe What is the Appearance of the Cells ? The cells are columnar in shape, with a nucleus and finely granular protoplasm. The brush of cilia is planted in a clear band. In the respiratory passages, except in the finest bronchi, the cells are stratified ; everywhere else they exist as a single layer. 14 Describe the Cilia ? They are flattened tapering filaments, about yy'g5 of an inch long. They consist of a colourless and optically homogenous substance, continuous with the clear band. They are elastic and of definite shape, contract in a definite way, and are not stained by magenta. They seem, therefore, to consist of modified protoplasm. What are the Parts of the Ciliwm ? 1. There is the cilium proper. 2. The intermediate segment. 3. The basal piece, which corresponds with the char HEM. 4. The ampullated rootlet that passes down through the protoplasm of the cell, curving round the nucleus. Describe Ciliary Motion. It is a rapid lashing movement that throws the surrounding fluid into a stream. They vibrate at the rate of about 700 times per minute. Lach cilium simply bends during contraction, and then straightens itself; it does not shorten. There is a band of ConTRACTILE substance at one side, and an Enastic band at the other. They bend down with a greater velocity than they straighten, and hence they give rise to a current of a definite direction. What-is the Cause of the Movement ? It is automatic—z.e., the source of motion is in itself, and altogether independent of nerves: the nucleus is not essential. It is an example of an “ AUTOMATIC MOTOR APPARATUS,” What are the Effects of various Reagents ? Chloroform vapour and carbonic acid gas arrest their move- ment. Moderate heat, weak acids, or alkalies, and weak electric currents stimulate them. 15 How are they best Studied ? By taking a piece of the gill of the salt water mussel, and mounting it with sea water. What are the Functions of the Cilia? They move mucus from the lungs to the pharynx ; and from the Eustachian tube to the pharynx. In the Fallopian tubes they aid the passage of the ovum towards the uterus. What takes place when Epithelium is Irritated ? The cells proliferate rapidly: if the irritation is too great, pus cells may be produced. With moderate irritation, the physiological nature is not changed; with severe irritation, the physiological nature is changed, and may be replaced by pathological changes. How do the Connective Tissue differ from the Epithelial ? In the connective tissues the intercellular substance is much developed, and the cells seem to hold but a secondary position— at least so far as numbers are concerned: in epithelium, the reverse obtains. What are the Forms of Ordinary Connective Tissue ? 1. Areolar, as in skin. 2. Aponeurotic form, ensheathing muscles. 3. Forming ligaments and tendons. What is Cartilage? . Cartilage is a non-vascular substance consisting of cells imbedded in a strong, firm, continuous, fibrillated, or homo- genous matrix. The function of the cells is to secrete this matrix. What are the Varieties of Cartilage ? I. Temporary, as found in fetus and in young subjects, but is destined to be replaced by bone. It may be either cellular or hyaline. 16 II. Permanent. This may be— 1. Cellular (not present in man). In this form there is practically no matrix, being composed entirely of cells. It is found in the ear of the rat, mouse, etc. 2. Cells, with distinct intercellular substance— (1) Matrix homogenous, like ground glass, without distinct structure Hyaline cartilage. (2) Matrix fibrous— (a) With white fibrous tissue White jfibro- cartilage. (b) With yellow fibrous tissue= Yellow fibro- cartilage. Name a Situation where we find Cellular Cartilage in the Foetus ? It forms the “ chorda dorsalis.” Name the Varieties of Hyaline Cartilage ? 1. Hyaline proper—typical form. 2. Costal cartilage. 3. Articular cartilage. Where is Hyaline Cartilage Found ? It forms articular cartilages, also costal, ensiform, trachea, bronchi, thyroid, cricoid, arytenoid cartilages, and cartilages of the nose. What are the Uses of Cartilage ? The articular breaks shocks, and gives ease to movements. The costal give elasticity to the chest walls ; in other situations it gives strength and firmness without making the parts too rigid. Describe ordinary Hyaline Cartilage. It is elastic, pliable, and tough ; in mass it is opaque and pearly, in thin plates it is translucent. It consists of cells embedded in a hyaline matrix. 17 The Crtts consist of masses of finely granulated protoplasm, rounded or angular in shape, with nucleus and two or three nucleoli. The protoplasm is spongy and fills the space, though water makes it shrink, and then a distinct capsule is seen lining the cell space. The Marrix, or intercellular substance, is hyaline and faintly granular. It resembles ground glass, and srmems homo- genous. The part next the cell forms a distinct capsule in the first instance, though it soon fuses with the rest. As a matter of fact the matrix can be shown to consist of fibrils held together by a clear cement substance. Also from cell capsule to cell capsule, though the matrix are little delicate canals for the passage of lymph. How can the Structure of the Matrix be Shown ? By digesting it with trypsin (the ferment of the pancreas). Also, by prolonged soaking in a 10 per cent. solution of sodium chloride. How is the Matrix Produced ? The nucleus and then the protoplasm divide into two; each half then secretes a new capsule, while the old one becomes fused with the surrounding matrix—being transformed into fibrils and cement. Hoes does Articular Cartilage differ from the ordinary form ? The chief difference consists in the arrangement of the cells ; they resemble somewhat the arrangement of cells in stratified squamous epithelium. 1. Near the free surface, the cells are flattened and lie ' parallel with the surface. 2. Below this they form irregular groups. 3. Near the bone they form vertical rows at right angles to the surface. In articular cartilage the matrix is not prone to calcify, though close to the bone there is a zone where the cartilage is evidently fibrillated and impregnated with lime salts. A 18 How does Costal Cartilage differ from the ordinary Hyaline form? The cells are in groups, several cells being within one capsule. The matrix is more distinctly fibrillated, especially near the cell groups; the fibrils seem calcified, and don’t swell up on the addition of acetic acid. The cells are often fatty, and the matrix shows a strong tendency to the deposition of lime salts. What do you call the Membrane that surrounds Cartilage ? It is called the perichondrium. It is a vascular fibrous membrane. It does not cover the surface of articular cartilage. It consists chiefly of white fibrous tissue, and there is a gradual transition between it and the cells and matrix of the hyaline cartilage, the edge of which it covers. How do the two Differ then ? The fibrous tissue of the perichondrium when treated with acetic acid swells up and becomes transparent ; further, when boiled it yields gelatine. The fibrillated matrix of cartilage is not affected by acetic acid, and when boiled it yields chondrin. What Covers Articular Cartilage ? Before the joint has been used the surface is covered by a layer of endothelium continued from the synovial membrane. How is Cartilage Nourished ? It is non-vascular, and depends for its nutrient supply on the blood-vessels of the sub-adjacent bone and synovial membrane. It is porous enough to allow of the penetration of lymph from the neighbouring capillaries. What Takes Place when Cartilage is Irritated ? The cells proliferate, and a brood of young cells fills the - cell-spaces. If the irritation is not excessive, each cell secretes a capsule ; if excessive they do not, but the spaces are enlarged and the cells come to resemble pus cells. 19 Where is White Fibro-Cartilage Found ? Inter-vertebral discs, sacro-iliac-synchondrosis, symphysis pubis, inter-articular cartilages, glenoid and cotyloid ligaments, semi-lunar cartilages, etc. Classify the Different Forms ? 1. Connecting, as in the inter-vertebral discs. 2. Marginal, or circumferential, to deepen cavities, as in the shoulder and hip-joints—glenoid and cotyloid ligaments. . 3, Inter-articular fibro-cartilages, as in the temporo-maxillary articulation. 4. Encrusting, lining bony grooves, as in the case of the obturator internus. 5. Sesamoid, in tendons, as in the tendon of the peroneus longus. Where do we find Enter-Articular Carttlages ? 1. Temporo-maxillary articulation. 2. Sterno-clavicular articulation. 3. Acromio-clavicular articulation, 4, Inferior radio-ulnar articulation. 5. Knee-joint—semi-lunar cartilages. What are the Parts of White Fibro-Cartilage ? 1. It consists of cells resembling those found in hyaline cartilage. 2. A clear, homogenous capsule, surrounding the cells, just as in hyaline cartilage. 3. The matrix consists of fine colourless fibrils, resembling those of white fibrous, tissue, the fibrils being obvious without special preparation, owing to the small amount of cement substance. How do the Inter-Vertebral Discs differ from other forms of ' White Fibro-Cartilage ? In the centre of the disc the cartilage has no fibrillated matrix ; often, too, a single capsule encloses a brood of young cells. It is pulpy and elastic. 20 What is its probable Origin ? It is probably directly descended from the cells of the CHORDA DORSALIS of the embryo, which in the first instance consists of cellular cartilage. Where is Yellow Fibro-Cartilage Found ? In the epiglottis, cornicule laryngis, in the outer ear, and in the Eustachian tube. What other Names has it got ? Reticular, spongy, or elastic cartilage. How does it differ from Hyaline ? It is more flexible, has a yellow colour, and a sponge-like appearance. It is also tougher and more elastic, and never ossifies. Describe its Structure and Origin? An elastic fibrous network, like that of elastic tissue, appears in the hyaline matrix. In this the cartilage cells are found surrounded by a hyaline capsule. In appearance it resembles a sponge, some of the hyaline matrix filling the meshes. It is always preceded by hyaline cartilage in the embryo. It consists of Exastin which is insoluble in hot water, and unaffected by acetic acid. Name the Uses of Cartilage in general. 1. It forms smooth surfaces, and thus reduces: friction— é.g., in joints. . 2. It acts as a buffer to deaden shocks. 3. It binds bones together firmly, and yet allows of some movement—e.g., the vertebre. 4, It helps to form a firm framework, without undue rigidity, as in the outer ear, larynx, and chest wall. 5. It deepens cavities, as the hip and shoulder joints ; and grooves, as in the peronei tendons at the ankle. 6. It serves as models in the foetus, around or in which the future bones may be laid down. 21 Where is Mucous Tissue Found ? In the adult it occurs only in the vitreous humour; in pathological states it sometimes reappears, forming myxomatous tumours. It forms Wharton’s jelly in the umbilicial cord, What are its Constituent Parts ? 1. A clear homogenous jelly-like matrix. 2. Stationary cells, with long delicate anastomosing processes. 3. Amoeboid or wandering cells, resembling white blood corpuscles or leucocytes. What Changes may it Undergo ? 1. The matrix may disappear and the processes grow stronger and shorter, forming Retirorm Tissuz, resembling that found in the spleen, lymph glands, walls of the intestine, trachea, and bronchi. In the meshes, lymph corpuscles are entangled. 2. Fibrils of white fibrous tissue may appear in and replace the matrix, and in this way tend to produce ordinary fibrous tissue. 3. The cells may develop into ordinary fat cells, thus forming adipose tissue. What are the Structural Elements of Ordinary Connective Tissue ? . Connective tissue cells proper. . Wandering cells, or leucocytes. . Coarsely granular cells. . White fibres. . Yellow fibres— (a) Fivz, as in peritoneum, and surrounding white fibres. (b) Coarss, as in vertebral ligaments—subflava, and ligamentum nuche. CUR Oo bo eH What are the Uses of the Elastic Fibres ? Their chief use depends on their elasticity ; and hence their great use in the lungs, arteries and veins, vocal cords, and skin. 22 In what Forms are they met with ? (a) Fibrous. (6) Membranous. Where ts the Fibrous form Found ? In the ligamentum nuche and subflava, between the rings of the trachea, true vocal cords, stylo-hyoid ligament, thyro- hyoid and crico-thyroid membranes. Where ts the Membranous form Found ? Chiefly in arteries and, veins (inner coat). It may be either uniform or fenestrated—the ‘fenestrated membrane of Henle.” Observe then the distribution of the yellow elastic tissue, viz.— : 1. Ligamenta subflava of the vertebra. 2, Stylo-hyoid, thyro-hyoid, crico-thyroid ligaments, the vocal cords, and calcaneo-scaphoid ligament. 3. The middle coat of the larger arteries and veins. 4, In the trachea, air tubes, and lungs. 5. Capsule of the spleen, and wherever white fibrous tissue is found. 6. Forming the ligamentum nuche of the horse and ox. What are the Characteristics of the Yellow Fibres ? 1, Pale yellow in colour. 2. Length indefinite, and very curly at the ends. 8. Branch and anastomose with each other. 4. The fibres are large in size and refract light strongly, and have a well defined outline. 5. Resist chemical action very much, and are not affected by acetic acid or weak alkaline solutions. 6. They are not stained by carmine. 7. They are very extensible; and when relieved from the stretching force, they recoil to their original length. 8. Chemically, it yields Exasrin. 23 In what forms is White Fibrous Tissue met with ? 1. Areolar tissue in the skin. 2. The aponeurotic form. 3. Ligaments and tendons. What is tts Special Use ? It is almost devoid of extensibility, and is therefore specially fitted to form tendons, aponeuroses, and those ligaments in which stretching is undesirable. Give the Special Charucteristics of the Fibres ? 1. Colourless and transparent. 2. Length varies; are not curly at the ends. 3. They do not branch nor anastomose with each other, but form parallel wavy bundles. 4, Each fibre consists of a great number of fibrils held together by cement (mucin). The fibrils resemble threads of spun glass. Fibres feebly refractive, and often encircled by elastic rings. 5. Acetic acid causes them to swell and become very transparent, almost invisible. 6. Are readily stained pink by carmine. ‘7. Are almost inextensible ; and when it is stretched by a powerful force, it fails to gain its original length when the stretching is discontinued. 8. Fibres yield gelatine on boiling. Describe the Cells found in Connective Tissue. 1. The Orpinary CerLts are fixed, finely granular, and flattened. There is an oval nucleus surrounded by a little undifferentiated protoplasm. Each cell has branching processes that may anastomose with those of neighbouring cells. Seen edgewise, the cells are spindle-shaped. 2. WanbeERING CELLS, nucleated cells like lymph or white blood corpuscles, and most likely are such emigrated. 24 What is the Structure of the Omentum ? It consists chiefly of bundles of white connective tissue enveloped in endothelial plates. It is an example of the ArzouaR form of connective tissue. What is the Structure of the Cornea ? It is an example of the Compact form of fibrous tissue. How does it differ from the usual form of Connective Tissue ? Instead of being opaque in mass it is perfectly transparent. When boiled, instead of yielding gelatin, it yields chondrin. The fibres, too, are mostly arranged in layers, with the flattened branching cells between them. What are the Special Features of Bone ? It is HaRD, and thus protects delicate organs, as the brain and spinal cord; it supports the limbs and trunks, and acts as levers for muscular movements. It is also ToucH and ELASTIC, as well as hard. On what do these Properties depend ? The hardness is due to calcareous matter, and the toughness to fibrous tissue. The fibrous tissue may be destroyed by incineration, and it is then exceedingly brittle. The calcareous matter may be removed by maceration in dilute hydrochloric acid, and then it becomes exceedingly pliable and soft. What may be Observed when a Long Bone is Sawn across? The surrace of the bone is seen to be dense or comPacr, whereas the centre is spongy or cancellated. In long bones there is a central cavity called the Mupunnary Cana. At the articular end every bone consists only of cancellated tissue. Name the Essential Structural ‘Elements of Bone. 1. Cents imbedded in a dense matrix, or periplast, of calcified fibrous tissue in lamellic. This matrix is twofold, 25 2. Cell-spaces, or Lacuna, 3. Fine tortuous canals, called Canaticuni, that connect the neighbouring lacune. They penetrate the fibrous matrix and probably serve as lymph channels. The bone corpuscles resemble connective tissue corpuscles to a certain extent, but they have no processes extending into the canaliculi. Describe the Bone Periplast or Matrix. It consists of two parts— 1. A thin membrane lining the lacunz and canaliculi. 2. The great part of the matrix consists of calcified fibrous tissue, arranged in lamellee, super-imposed like the leaves of a book. Describe a Lamella. The ultimate lamellze consist of one or two layers, forming a fine reticulum of transparent fibres. The fibres intersect obliquely, and consist of fibrous tissue and lime salts in chemical union probably. Minute apertures are seen, probably the canaliculi torn across; here and there are larger openings, the sockets of the perforating fibres of Sharpey. The fibres swell up in acetic acid and yield gelatine on boiling. The lacune occur at varying intervals; usually two to five lamelle intervene between neighbouring lacune. What Openings are seen in Compact Bone ? 1. Haversian canals, for blood-vessels. 2. Haversian spaces. Both so-named from Havers, their discoverer. Are the Spaces Numerous ? In adult bone they only occur here and there, and are most numerous in young and rapidly growing bone, 26 What is found round the Haversian Canal ? Lamelle and lacune arranged concentrically: the whole forms an osseous cylinder called a Haversian system. How can you Explain this Concentric Arrangement ? It is due to the fact that the lacune and lamelle are deposited successively from without inwards in the Haversian SPACES, which are thus narrowed down into CANALS. It will be seen, therefore, that the “space” precedes the “canal.” It is important to remember this relation. What Direction do the Haversian Systems take ? They mostly run in the direction of the greatest strain. What are the “ Medullary Spaces” ? The cancellous or medullary spaces are large spaces, con- taining marrow, that are found in spongy bone. Give their Connections. They communicate on the one hand with the medullary canal, and on the other with the Haversian canals. How are Lamelle Arranged ? Into four sets— 1. Haversian, arranged concentrically around the Haversian canals. 2. CancELLous, similarly arranged round the medullary spaces. 3. PERIPHERIC, arranged parallel with the periosteum. 4, InrerMepiaTE, forming irregular groups between the | Haversian systems, and are probably the remains of the peri- pheric lamelle. What are Sharpey’s Fibres ? They are fibres that pierce and connect the peripheric and intermediate lamelle of bone with each other. Resemble nails, or pegs, in sockets. 27 What Purpose do they Serve ? They connect and strengthen these lamellee mechanically. They are best seen where a tendon is attached to the bone, and probably strengthen the attachment, and prevent the separation of the superficial layer of bone during the action of the muscle. What ts the Periostewm ? It is a fibrous membrane that everywhere covers the bone, except at the articular surface. It forms a medium for the subdivision of the blood-vessels before they enter the bone. What is its Structure ? It consists of two layers— 1. OUTER LAYER, composed of elastic and white fibrous tissue, mostly running longitudinally. 2. InnzR LAYER, or osteogenetic layer, composed of fine fibrous tissue with numerous cells, called OstEoBLasts, or bone- forming cells. The structure varies according to the age of the person. In what way ? In young growing bone the cells are much more numerous ; as age advances it becomes more fibrous, and the osteoblasts fewer in number. The deep layer of the periosteum is pro- longed into all the Haversian canals. What Structures are found in a Haversian Canal ? Fine connective tissue, enclosing blood-vessels, lymphatics, and nerves, and a layer of osteoblasts lining the canal. What else do we find ? Especially in young spongy bone we find here and there large multi-nucleated giant cells, called Osrmociasts, because they are concerned in the absorption of bone. What is found in the Interior of Bones? Marrow. 28 How many kinds are there ? Two; yellow and red. _ Where is the Yellow found ? In the medullary canal, and the larger cancelli of long bones. What is its Composition ? It chiefly consists of FraT-ceLLs—which gives it its yellow colour——blood-vessels, and a small amount of connective tissue. Where is Red Marrow found ? In the spongy tissue at the ends of the long bones of the limbs, in the clavicle, ribs, and in all the flat and short bones. What is tts Composition ? It consists of delicate connective tissue, many blood-vessels, and a great number of cells—medullary cells or proper marrow cells. It also contains some giant cells, and osteoblasts, as well as young red corpuscles and leucocytes. Red marrow has been regarded in the light of a blood gland, producing blood corpuscles. It contains very little fat, whereas yellow marrow is almost all fat. How ts a Long Bone nourished ? 1. The interior, medullary canal with the marrow, is nourished by the so-called “ nutrient artery.” 2. The compact tissue of the shaft is nourished by the periosteum. 3. The spongy ends are nourished by the arteries supplying the joint—articular arteries. What ts Peculiar about the Veins in Bone ? In the cancelli they are numerous and much dilated. In compact bone they have pouch-like dilatations, and sometimes occupy canals distinct from those containing the arteries, Most of the vessels have few or no muscular fibres. 29 What is the Composition of Bone ? The solids consists of about one-third organic, and two- thirds earthy or mineral matter. What forms the Mineral Matter ? It consists chiefly of calcium phosphate, carbonate and fluoride, with some magnesium and sodium salts. Is the proportion the same in every Bone ? No; some bones contain more earthy matters than others, and are therefore harder—e.g., the temporal bone, especially the petrous part. ‘ Does the Composition of Bone vary much at Different Ages ? No; it is almost the same from infancy to old age. Why are Bones then so Brittle in Old Age ? It is probably due to some crystalline change in the earthy matters, or molecular change in its fibrous tissue. What takes place when Bone is Boiled ? The animal matter becomes gelatine. What are the Modes of the Development of Bone? 1. Intra-cartilaginous. 2. Intra-membranous. Are these Two Modes always Quite Distinct ? No; the development of a long bone of the limbs is both intra-cartilaginous and intra-membranous. Give the Chief Steps of the Process of Intra-Cartilaginous Osstfication. 1. The cells near the ossific proliferate, and form longitudinal rows. Each cell secretes a capsule, and the matrix becomes infiltrated with lime salts. 30 2. The cells become much larger, and cause partial absorption of the matrix. 3. Below this the primary medullary spaces are formed, containing capillaries and cells, and occupying the site of the rows of cells, the transverse septa being absorbed by the growth inward of capillaries from the cellular layer of the perichondrium. The cells of the cartilage thus set free are said to disappear, and the cells found in the spaces are either white blood corpuscles emigrated from the blood-vessels, or modified connective tissue corpuscles. 4, Some of the foregoing cells become giant cells, and apply themselves to the sides of the calcified trabecule that bound the spaces, and cause absorption of the calcified matrix. 5. The trabeculae then become encrusted with primary spongy bone, secreted by the osteoblasts; these become bone corpuscles, and are enclosed in the spongy matrix. 6. Removal of the primary spongy bone by the giant cells in the interior, part passu with the deposition of periosteal bone. Finally, the deeper part of the periosteal bone becomes absorbed to complete the medullary cavity. How is the Epiphyses Formed ? It grows from separate centres of ossification. Before these centres are formed there is an inward growth of vascular periosteal processes, just as at the centre of the shaft. Define the word Epiphyses. ‘When the end of a bone ossifies from a centre, distinct from the centre from which the shaft (Diapuysis) arises, it is called an EPIPHYSIs. How does a Bone grow in Length and Thickness ? Its growth in THICKNESS comes from the osteogenetic layer of the periosteum. The growth in Lenara takes place in the layer of cartilage found at the point where the epiphysis joins the shaft. 31 How do you know that the Increase in Length is not due to Interstitial Growth ? Hales and Hunter proved that it takes place at the ends, and not interstitially, by boring holes and inserting shot or ivory pegs at a measured distance apart in the shaft of a young bone, and after a time found that, although the bone had grown longer, the distance between the pegs had not increased. Give a Short Account of Intra-Membranous Ossification. 1. The perichondrium becomes periosteum, and the fibrous matrix becomes calcified, while the cells at the deeper part become bone corpuscles. 2. The corpuscles proliferate rapidly, and thus we have the periosteum and its layers of osteoblasts formed. The osseous matrix is produced as clear fibres, and these interlace and form lamelle. 3. The osseous texture grows in the form of trabecule, which coalesce here and there, including portions of the deeper part of the periosteal tissue and blood-vessels and osteoblasts, and in this way spaces are enclosed—Haversian spaces. 4, In these the osteoblasts deposit bone in concentric layers, and thus narrow the spaces down to Haversian canals. What was Syme's Experiment in regard to the Periosteum ? He showed that the periosteum produced bone, by placing a silver plate between the periosteum and bone of the radius of a dog, a layer of bone was produced outside the plate. What was Ollier’s Experiment ? He showed that transplanted periosteum produced bone, by excising a piece of periosteum and planting it beneath the skin. What is the Effect of Madder on Growing Bone ? Madder everywhere stains growing bone, so that the ends of the shaft unDER the epiphysis, and a layer of bone under the periosteum, and around each Haversian space and canal, is reddened by the dye. 32 How is this? It is because the madder has a strong affinity for calcium phosphate. What is the Function of Osteoclasts ? It is to absorb bone: they apply themselves to bone and slowly hollow it out. ; What are the Pits called in which they lie? Howship’s lacune, or Howship’s foveole: so-called because Howship discovered them. What other Names have these Osteoclusts received ? They are called giant cells because of their great size, and also because they are multinucleated. They are also named Myenopiaxes by Robin. Kolliker was the first to give them the name of OsTEoc.asts. How do you know that they Absorb Bone ? After feeding with madder, a layer of reddened bone is seen under the osteoblasts, but not under the osteoclasts, showing that the former and not the latter are concerned in ‘the production of bone. What is Adipose Tissue ? It consists of cells whose function is to secrete fat. The cells are held together by a very small amount of areolar tissue, and between each cell and surrounding them there is a very close capillary network. Where is Fat chiefly Found ? It chiefly occurs in the deep layer of the skin, around the synovial membrane of joints, in the mesentery and omentum, and in the orbit. Where ts it not Found ? It is not found within the cranium, or between the bladder and rectum, or in the subcutaneous tissue of the eyelids, nor in the skin of the penis. Describe the Fat Cell. Its chief parts are— 1. A thin colourless envelope. 2. A central mass of yellow fat. 3. A nucleus placed eccentrically between the oil and the envelope. 4. In younger cells the envelope is lined by a layer of protoplasm, and which may also surround the nucleus, giving a peculiar “signet ring” appearance to the cell. The nucleus and protoplasm stain readily with carmine. In shape the cells are either spherical or polyhedral. How can the Envelope be Shown ? In various ways— 1. After blackening with osmic acid. 2. After washing the cells with ether, which removes the fatty matters. 3. By injecting a dilute solution of nitrate of silver into the subcutaneous tissue of a rabbit immediately after death. What ts the Nature and Constitution of Fat ? It chiefly consists of tri-palmatin, tri-olein, with a little tri- stearin—palmitic, oleic, and stearic acids united with glycerine. After death the palmatin and stearin often form colourless needle-shaped crystals, the so-called “‘ Margarin” crystals. The yellow colour of fat is due to a pigment. What are the Effects of Starvation on Fat Cells? The fat disappears from the cells, leaving the envelopes of the cells somewhat collapsed; the nucleus and protoplasm are also left, with the yellow pigment and a little clear fluid. The capillaries—many of them—atrophy and disappear. The cells thus left are often termed “szrous” fat cells. The nucleus sometimes proliferates. B 34 What takes place when Fat is Irritated ? The nucleus multiplies, and a brood of young cells appears between the fat and the envelope. How are Fat Cells Developed ? They are probably developed from connective tissue corpuscles, or some modification of them. The fat appears as fine globules amidst the protoplasm; these globules coalesce, and push the nucleus and the protoplasm to one side, which latter may, to a great extent, disappear, although at first it forms a continuous layer around the fat. Fat cells are largely supplied with blood-vessels, and are usually developed close to them. As the amount of fat increases, New blood-vessels are formed in one or other of the two ways already indicated on page 8. What are the Functions of Adipose Tissue ? 1. It forms a soft elastic cushion in the orbit for the eye; so also around the lower end of the rectum. It gives softness to the skin, and diffuses pressure, as in the sole of the foot and the gluteal region. 2. It retards the radiation of heat. 3. It forms a store of food for the needs of the economy— a store chiefly of carbon and hydrogen. How ts it probably Produced ? The protoplasm of the fat cells seem to have the power of producing rar from amyloids and proteids, and storing it up till required. It may also be stored up directly from the fat taken in the food. How ts the Fat Re-absorbed ? It may either pass from the cells to the blood-vessels unchanged, or it may be converted into soluble soaps and then removed, 35 Which is the more likely ? Probably the latter, as the yellow pigment of the fat is left behind. How many Sets of Teeth are there ? Two— 1. The temporary, deciduous, or milk-teeth —twenty in number. 2. The permanent set—thirty-two in number. What are the Names of the Teeth ? Incisors, canines, bicuspids, and molars. How are they Arranged in the Milk Set? Two molars, one canine, and two incisors in each half of each jaw. How are the Permanent Set Arranged ? Three molars, two bicuspids, one canine, and two incisors in each half of each jaw. What are the Parts of a Tooth ? It consists of a free part or Crown; a part imbedded in the jaw, called the Fane; and a part between the two, called the Neck. So there are three parts visible to the naked eye, without special preparation—Crown, Neck, and Fang. What are the Parts seen on Section ? It consists then of four parts— 1. The Puts, filling a central space, the pulp cavity. 2, The Deyting, surrounding the pulp cavity. 3. The Enamet, covering the dentine in the crown. 4. The Cement, covering the dentine in the fang. 36 How do Blood-Vessels and Nerves reach the Pulp? They enter the pulp through a minute aperture at the point of the fang. , 3 What is the Structure of the Cement ? The cement or crusta petrosa, is simply a thin plate of bone. It consists of bone corpuscles in lacune, with canaliculi embedded in a matrix of calcified fibrous tissue arranged in lamella. How does it Differ from Ordinary Bone ? 1. It is rather harder than ordinary bone. 2. There are no Haversian canals, as the plate of bone is so thin that they are not required. 3. The corpuscles are larger. 4. Sharpey’s fibres are more numerous. These fibres pass from the periodontal membrane, and serve to fix the tooth. Describe the Enamel ? The enamel covers the crown of the tooth. It is very hard, and consists almost entirely of earthy salts. It is composed of solid prisms set endwise on the dentine. On vertical section they are seen as wavy bands, closely set, and marked at regular intervals by fine clear transverse lines, probably from inter- mittent calcification.. On transverse section they are seen to consist of hexagonal fibres, but may be polygonal. What are the ‘‘ Brown Lines of Retzius ?” They are coloured lines seen crossing the enamel, and forming a series of arches, more or less complete. What is Nasmyth’s Membrane ? It is the cuticle of the enamel, a thin calcified membrane covering the enamel in young subjects. It soon gets worn away. 37 What ts the Structure of the Dentine ? It consists of tubules imbedded in a calcified matrix, chemically like that of bone, but structurally different, as the organic part is not fibrous but homogenous. The tubules open into the pulp cavity, radiate through the dentine, and end near the periphery. Their course is wavy, having two or three primary, and many secondary curves. The walls are formed by a fine homogenous yellowish membrane. What is Found in the Dentinal Tubules 2 Each tubule contains a fine fibre, the ‘dentinal fibre,” or “fibre of Tomes.” What ure these Fibres ? They are processes of cells, the odontoblasts, that lie in the pulp cavity close to the dentine. What ts the Inter-Globular Substance ? It is a granular-looking layer, and is seen to consist of “inter-globular spaces” and is probably formed of dentine that has escaped calcification. What ts the Structure of the Pulp ? In many respects it resembles the Haversian canal of a bone. The pulp fills the pulp cavity, and consists of a delicate con- nective tissue, containing numerous cells, vessels, and nerves. The cells lie close to the dentine, forming a regular layer, and are called odontoblasts. Name the Processes of the Odontoblasts. The processes consist of three sets— 1. The Externat, which are the dentinal fibres. 2, The Larerat, which connect neighbouring odonto- blasts. 3. The CznrraL, which join the odontoblasts to the connective tissue corpuscles in the pulp cavity. 38 What Nerve supplies the Teeth ? The fifth cranial. Give a Short Account of the Development of a Tooth ? They are developed from the mucous membrane of the maxillary ridges, the enamel being formed from its epithelium, and the remaining dental tissues from the sub-epithelial connective tissues—the whole part concerned being known as the DENTAL GERM. ‘The following are the chief steps of the process :— 1. About the seventh week of fcetal life the epithelium proliferates and forms two ridges—the DENTAL RIDGES—with a shallow groove between, called the SUPERFICIAL DENTAL GROOVE. 2. The deeper part of the epithelium grows down obliquely into the soft connective tissue, forming the DEEP DENTAL GROOVE. This extends all round the gum and is filled with epithelium, called the COMMON, OR PRIMARY, ENAMEL GERM, OR ORGAN. 3. Flask-like dilatations occur in deep dental groove, due to proliferation of the epithelial cells. These mark the site of the future teeth, and the epithelium filling each flask is known as the SPECIAL ENAMEL GERM, Or ENAMEL ORGAN. 4, A papilla grows up at the base of each flask and indents it, and is called the DENTINE GERM, as it forms the dentine and tooth pulp. The papilla consists of mucous connective tissue and. blood-vessels. How ts the Enamel Formed ? From the enamel organ that covers the dentine germ. It forms itself into four layers— 1. External epithelium, consisting of low cubical cells, ' 2. The enamel pulp, like mucous tissue, with stellate cells and branching processes, . 3. Stratum intermedium, a layer of rounded cells. 4. The internal epithelium, consisting of hexagonal columnar cells, which become the enamel prisms ; calcification proceeds from the inner end and involves the periphery first. 39 Give the Eruption of the Temporary Teeth ? The following gives the Montxs at which they appear :— Incisors. CANINES. Mo.ars. 7,9 18 12, 24 What Provisions are made for the Permanent Teeth ? There is an involution, or cavity of reserve, formed from the common enamel germ at the neck of the follicle of each of the milk teeth. These involutions remain quiescent till the proper time comes, when they develop in the ordinary way. At first the new tooth is separated from the other by a thin plate of bone, from the alveolus. As the new tooth grows it presses on this, and it is absorbed partly by pressure, but chiefly by odontoclasts. Not only is the thin plate of bone thus absorbed, but the fang of the milk tooth as well. Hence, when the milk teeth come out, they have no fang. Give the Eruption of the Permanent Teeth ? The following gives the years at which they appear :— INCISORS. CANINES. BICUSPIDS. Morars, 7,8 11 to 12 9, 10 6, 12 to 13, 17 to 25. What are the Varieties of Muscular Tissue ? 1. The unstriped or smooth, sometimes called involuntary. 2. The striped, sometimes called voluntary. Where does Non-Striped Muscle Occur ? Tn the alimentary canal below the middle of the cesophagus, in the trachea and bronchi, in arteries, veins, and lymphatics, in the bladder, ureters, urethra, and in the male and female genital organs ; also in the skin, iris, and ciliary muscle. What is peculiar about the Upper Half of the Pharynx ? In this part the muscle is striped. 40 Why is this ? Probably to allow of more rapid contraction, as in this situation the food has to cross or pass through the respiratory passage. Name another Striped Involuntary Muscle. The Heart. Notz—l. Ordinary striped muscle contracts most rapidly ; next comes 2. The heart; and 3. Ordinary non-striped muscle contracts most slowly of all. Are the terms “ Voluntary” and “Involuntary” correct as applied to Striped and Non-Striped Muscle respectively ? Not quite: for the heart is an involuntary muscle, but is composed of striped fibres; whereas the bladder, which mostly acts under the influence of the will, consists of non-striped fibres. Describe the Fibres of Non-Striped Muscle. Fusiform fibre-cells, tapering at the ends; in section they are elliptical or round: colourless and transparent. There is an axial band of very fine homogenous fibrils: a single rod- shaped or oblong nucleus near the middle with a membrane, and inside this a delicate reticulum. There is a vERY THIN elastic wall to the fibre (the sarcolemma) with fine annular corrugations, or thickenings; hence, its striated look. The length of the fibre varies from g$, to z45 part of an inch. What is the Special Appearance on Transverse Section ? In transverse section non-striped muscle resembles a mass of round cells, the special feature being that some of the apparent round cells have well marked nuclei, while others have not, 41 How is this ? It is due to the fact that some of the cells are cut at the level of the nucleus, while others are not. What are the Parts of Striped Muscle ? 1. A cell wall or sarcolemma: it is transparent, homogenous, elastic, and tough. At certain places it is connected with the sarcous substance. 2. Nuclei, or muscle corpuscles. These lie immediately beneath the sarcolemma in mammals, but in the frog they lie amid the sarcous substance, as well as under the sarcolemma. The nuclei are flattened, and occur at irregular intervals, and are surrounded by a little undifferentiated protoplasm, 3. The contractile matter or sarcous substance. This is composed of contractile fibrils. Describe the Sarcous Substance. It is crossed by clear and dim stripes alternately: the dim stripe is the wider. Through the centre of the clear stripe a dim line passes, known as “ Dobie’s line.” There is also a stripe across the middle of the dim band, known as “ Hensen’s stripe,” and is supposed to be due to a swelling in that position. Each fibre is striated longitudinally, these striations being the outlines of fibrils; each fibre is thus composed of a mass of fibrils. Each fibril consists of alternate segments of the dim and clear bands. The segments forming the dim stripe represent the “sarcous substance of Bowman.” Transverse clearage readily takes place between the dim and the clear stripes. The dim segments are not uniform, but have three swellings, one at each end, and one in the middle (forming “ Hensen’s stripe”). 42 What is Dobie’s Line ? It is a row of highly refracting globules, that crosses the clear stripe; there is one in each fibril, and it causes the clear stripe to bulge. The sarcolemma is attached to Dobie’s line. There is a row of dots on each side of Dobie’s line, known as “ Engelmann’s dots.” In what other respects do the Two Stripes Differ ? The dim band is contractile and elastic ; the clear band is only elastic, not contractile. ‘ What Chunges Occur when the Muscle Contracts ? The fibre shortens, at the dim segment chiefly, and the three swellings in this segment disappear. At first there is no change in the clear stripe, but when the muscle is fully contracted, it also is shortened, probably due to stretching by the thickened and shortened dim segment, as it is this segment alone that is contractile. Further, the clear stripe grows much dimmer than the dim stripe, and the globules of Dobie’s line disappear. The dim stripe also becomes a little dimmer than it is normally. These changes can only be observed through the microscope. How do the Fibres of the Heart Differ ? They differ— 1. In structure. 2. Functionally. What are the Structural Differences ? Though striped, they are involuntary. They have no sarcolemma, and usually only one nucleus in the centre of the fibre. The fibres consist of short cylinders, and anastomose with each other, either by short branches, or their longitudinal surfaces. The stripes are not so regular, nor so well marked, as in ordinary striped muscle. 43 How do they Differ Functionally ? The contraction takes place much more slowly, and is much more prolonged than in ordinary striped muscle. What are Purkinje’s Fibres ? They are peculiar looking cells found under the ventricular endocardium of ruminants. They are polyhedral, with a cortex of striated sarcous substance, enclosing a core of un- differentiated protoplasm, with one or two nuclei. They are believed to be cardiac muscle fibres arrested in development. What do you know of the Elasticity of Muscle ? The elasticity of muscle is small in amount, but perfect in quality; that is, it readily extends, and when the stretching power is removed it regains its former length, provided it has not been over-stretched, How does it Differ from an Elastic Band ? In an elastic band the extension is proportional to the weight applied ; in a muscle it is not so, but the first weight produces a greater effect than the second, the second than the third, and soon. The line of elasticity of an elastic band is a straight line ; whereas the line representing the elasticity of muscle is ~-almost a hyperbola, including both the curve of extension and the curve of recoil. What is the “ Limit of Elasticity” ? It is a point beyond which, if a muscle be stretched, it does not completely recoil to its former length: this being the case, it is said that its “limit of elasticity” has been passed. 44 What is meant by Elasite After Action ? When a weight is applied to a muscle, there is at first a sudden and then a more gradual elongation ; so likewise, when the weight is removed, there is at first a sudden and then a more gradual recoil. The slow or gradual parts are the two phases of “ elastic after action.” What is meant by the Tone of a Muscle ? Even when a muscle is relaxed it is not perfectly limp, but is in a state of slight tension ; hence it feels firm and not flabby. Also, when a muscle is divided, the ends retract and the wound gapes. This state of slight tension is spoken of as the “tone” or tonicity of the muscle. It is probably due to elasticity, as it does not disappear when the nerve is divided. Is the Tone of Sphincter Muscles due to the same Cause ? No ; this is a real contraction, kept up by nervous impulses passing from the spinal cord. What Conditions Lessen the “ Tone” of Muscles ? The elasticity, or tone, of muscles is diminished by— 1. Fatigue. 2. Defective nutrition. 3. Weak relaxed states of the system. What are the Functions of this Elasticity ? 1. The muscle is kept in a state of slight tension, or kept tight, so that at the moment of contraction time is not lost, nor energy wasted in bracing it up. 2. For the same reason the shock of contraction is lessened, as there is no “tight” to haul in. 3. It also lessens the dissipation of energy, as a force of short duration acts best through an elastic medium. 45 What ts meant by the Irritability or Excitability of Muscle ? It is a property in virtue of which it can be thrown into contraction by the application of various forms of stimuli. What form of Stimulation ts usually Used ? Electrical, either galvanic or faradic. How its this done ? The tissue to be stimulated is simply made a part of the electrical circuit, and the stream passes through it from electrode to electrode. What do you mean by “ Electrodes”? The electrodes are the points, or surfaces, that serve to convey the current into and out of the tissue to be stimulated. In ordinary cases they are a pair of insulated wires, or plates of copper or platinum. What are “ Non-Polarisable” Electrodes ? Ordinary electrodes, when in contact with moist tissues, generate feeble electric currents. Non-polarisable electrodes ‘are so made that they do not thus generate electric currents. Name some such. 1. Those of Donders, where sculptors’ clay is the terminal. 2. Those of Fleischl, where a small camel-hair brush forms the terminal. How is Galvanic Electricity Produced ? By means of a number of “cells” of various kinds. 46 What takes place when a Nerve-Trunk is thus Stimulated ? When a current of galvanic electricity is applied to a NERVE-TRUNK, it only stimulates when it enters and when it leaves the nerve, but not during the flow, unless it undergoes changes in intensity. This is true whether the nerve-trunk be motor or sensory. What takes place when it is applied to Sensory Nerve Termi- nations ? These also are stimulated when the current enters and leaves, but also during the entire period of the flow as well. How are Muscles Affected ? When a muscle is stimulated directly by a weak galvanic current, we get contraction only at opening and closing the current; but when the strength of the current is increased, a state of constant contraction (tetanus) is produced. How can it be proved that the Galvanic Current Stimulates Muscles Directly ? By first using curara, which paralyses the motor nerve endings, and thus physiologically eliminates the motor nerves. What other Points are of Special Importance to Note ? That, in both nerve and muscle, stimulation occurs only at the Nzcative pole at cLosurE of the circuit, and only at the POSITIVE pole on OPENING it, and that the negative pole is the more powerful stimulus of the two. What do you mean by the Negative and Positive Poles ? Outside the battery the current always runs from the positive fo the negative PoLE; but inside the battery it is from the positive to the negative eLemunr. The zine pole is the negative one; while the carbon, copper, or platinum forms 47 the positive pole. Note, however, that while zinc forms the negative POLE, it is the positive ELEMENT; the carbon forming . the positive pole, but the negative element. What is the Principle of Faradic Electricity ? In this form a current of any strength can be secured from a single cell, It depends on the fact that if two electrical circuits be placed in proximity, but, not in contact, and a galvanic current be sent through one of them, an INSTANTANEOUS current is induced in the other at the moment when the galvanic stream enters and when it leaves its circuit. What are the Names of these two Streams ? The inducing current is called the Primary, while the induced is called the szconDaRY. What ts the Relation of these two Streams ? The secondary current, induced -at closing the primary circuit, or increasing its intensity, has a direction the REVERSE of that in the primary circuit; while that induced at opening, or from diminishing its intensity, has the same direction. How do the Wires of the two Cotls Differ ? The wire of the privary coil is thin and long, with a very high electrical tension. The wire of the secondary coil is short and thick, and has a very low tension. How do the two forms of Electricity Differ in regard to Stimu- lation ? The instantaneous currents of the induced form stimulate nerve tissues better than the slow galvanic. Induced electricity does not stimulate muscular tissue directly, it affects muscles whose nerves are healthy ; in other words, it only acts on muscle 48 through the nerves. The galvanic current, on the other hand, stimulates muscular tissue directly and altogether independently of nerves; so that in a muscle with paralysed nerves, the galvanic will stimulate when the faradic fails. What is the Effect of Curara ? It paralyses the peripheral terminations of motor nerves, especially voluntary motor nerves—i.e., the motor end organs. Sensory nerves and their end organs are not paralysed. Is Contractility an Inherent Property of Muscular Fibres ? Yes: muscular fibres themselves are capable of being directly stimulated without the intervention of any nerves. What are the Proofs? 1. It is manifested in a muscle which is isolated from the influence of the nervous system by division of its nerves, as long as the tissue of the muscle is nourished properly. 2. It is manifested in parts of muscular fibres in which no nerve fibres can be seen under the microscope. ; 3. Curara paralyses the motor nerve endings in muscle— a.e., it physiologically eliminates the motor nerves, but it does not diminish the irritability of the muscular tissue to any marked extent. 4, When a muscle is fatigued, a local stimulation is followed by a local contraction, without any regard to the distribution of nerves. 5. When the nerve has lost irritability, and refuses to respond to the strongest stimulus, contraction may be obtained by applying the electrodes directly to the muscle, even though the nerve has degenerated right into the muscle, so that it has lost all its nerve elements. 6. Ammonia stimulates muscular fibres to contraction, but kills the nerve without stimulating the muscle. On the other hand, glycerine, benzol, or creasote excite nerve, but not muscle. 49 What are the Parts of the Muscle Curve ? When a muscle is stimulated by a single induction shock four events follow :— 1. The “Larewr Periop,” the period between the entrance of the current and the appearance of the visible contraction. 2. The “ PERiop or Contraction,” when the electrical energy is transformed into mechanical. 3. “ Pertop oF Rapip RELAXATION,” said to be due to elastic recoil, after the current has been shut off. 4, The ‘ Pgriop or Stow ReLaxation.” Does the Length of the Latent Period vary ? Yes ; it varies— 1. With the strength of the stimulus. The stronger the stimulus the shorter the latent period; it is therefore shorter after an OPENING shock, as this is stronger than the closing one. 2. It also varies with the excitability of the tissues; when a muscle is tired and worn out, the latent period is increased. What occurs during this Period ? There is no change takes place visible to the unaided eye ; still, an electrical change takes place, called the “NEGATIVE VARIATION” of the muscle current. This change occurs in the latent period, and in the latent period only. What is meant by the Negative Variation ? It is believed by many, that in a normal healthy muscle there is a distinct, though slight, electric current being con- stantly produced, and circulating. When a shock or current of induced electricity is sent through such a muscle, this natural muscle current is diminished, and the needle of the galvanometer moves back towards zero. This diminution of the natural muscle current is spoken of as the negative variation of the muscle current. c 50 What is meant by Simple and Compound Contraction ? A sIMPLE is a single contraction, whereas a COMPOUND con- traction is a succession of single contractions. What is meant by Physiological Tetanus ? When faradic shocks are applied to a muscle or its nerve in quick succession, the relaxation of the muscle becomes incomplete ; and if the shocks are sufficiently rapid, the single contractions become so completely fused together that the line representing the contractions seems as if due to a single or simple contraction. This condition is known as “ physiological tetanus.” How can you prove that it is not due to a Single Contraction ? By the sound of the tetanized muscle: the sound produced is a MUSICAL note, and therefore due to a series of regular rhythmical vibrations, and not to a single impulse, which could only produce a NOISE. What is the Nuture of ordinary Voluntary Contractions ? Every voluntary contraction that is not instantaneous is a tetanus—+.e., a compound, not a single contraction. This is _known to be the case on account of the sound given forth by the contracting muscle. What ts the Pitch of the Note heard ? The note has a pitch of 39 vibrations per second, and is probably the first overtone—i.e., the octave—of the fundamental note produced by the muscle, which would therefore have a pitch of 194 vibrations per second. What is the Exact Significance of the Muscular Sound ? It indicates that every voluntary contraction, not instan- taneous, is a COMPOUND contraction, and is due to a succession of 194 nerve impulses projected from the brain every second, 51 What is the Velocity of the Contraction Wave ? It is 11} feet per second. Flow is it Measured ? It is measured in the curarized sartorius of a dog, by Marey’s myographic forceps and tambour levers. On what does the Amount of Contraction of any Muscle Depend ? 1. On the strength of the stimulus. 2. On the resistance to be overcome: up to a certain point the resistance tends to increase the amount of the contraction, though a limit is reached. 3. Length and energizing power of the muscle: the longer it is the more it contracts, but if stimulated again and again it becomes fatigued and the amount of the contraction decreases, What Changes take place in a Muscle during Contraction ? 1. Change in form: it shortens and thickens. 2. Microscopic changes (see page 42). 3. Electrical changes.—During the latent period we get the “ negative variation” of the muscle current. 4. Chemical changes— (a) Much carbonic acid is produced, and more oxygen used up. (®) Sarco-lactic acid is produced ; and this (c) Changes the reaction from neutral or alkaline to distinctly acid. (a) Glycogen in the muscle is used up. 5. There is a slight rise of temperature. 6. The blood flowing from a contracting muscle is more venous than that from a muscle at rest. 7. The muscular sound is produced. 8. Its elasticity lessens, and hence the “paradox of Weber.” . 52 Compare Striped and Non- Striped Muscle as regards Con- traction ? STRIPED— 1. When irritated, contraction takes place at the irritated part only. 9. The contraction is instantaneous. 3. It stops immediately the stimulus is withdrawn. Now-StrRipED— 1. When irritated the contraction extends beyond the part irritated, in waves. 2. The contraction ensues more slowly—that is, there is a long latent period. 3. It lasts some time after the stimulus is withdrawn. What is meant by “ Irritability” in Muscle and Nerve respec- tively ? 1. In Muscie it means a property in virtue of which it contracts upon the application of some stimulus: this stimulus rouses the energy into activity. 2. In Nerve it means that it (the nerve) is capable of transmitting along itself, without any visible change in form, certain molecular changes set up by some stimulus, called “ nervous impulses.” What is meant by Idio-Muscular Contraction ? When a muscle is struck sharply during the last stages of exhaustion, a LocaL contraction is produced ; it does not spread from the point struck. This may be done after the ordinary stimuli have ceased to act. It may also be produced on the living body, in wasting diseases such as phthisis. How does Temperature affect the Irritability of Muscle and Nerve ? Heat.—Up to a certain point this increases both in muscle and nerve. If the temperature be too high, however, the muscle passes into a state of rigor mortis. Cotp.—This lessens the irritability, both in muscle and nerve, 53 How does Fatigue affect Muscle ? A fatigued muscle requires a stronger stimulus to produce the same amount of contraction, What happens if the Flow of Blood be Arrested ? If the circulation be completely arrested, irritability gradually disappears, and in from one to seven hours the muscle passes into a state of rigor mortis. What is the Nature of Rigor Mortis? It is due to the coagulation of the myosin of the muscle from want of oxygen. The muscles become a little shorter and thicker, but this is not a real contraction. How are the Muscles Affected ? The muscles of the back of the neck and head are first affected ; then those of the arms, trunk, and legs. It disappears in the same order. What Conditions affect its Invasion and Duration ? In any condition that exhausts the muscle before death, its invasion is rapid, and its duration short, and vice versd. What are the Parts of the Nervous System ? It consists of cells and fibres, How many Kinds of Fibres are there ? Two— 1. The grey, pale, or non-medullated fibres, chiefly found in the sympathetic system. _. 2 The white, medullated, or tubular, found chiefly in the cerebro-spinal system. What is the Structure of the Grey Fibres? 1. They consist of a bundle of very fine fibrils—colourless, transparent, and soft—apt to be varicose or moniliform, These 54 fibrils form the axis cylinder, and are held together by cement. They are covered by 2. The grey sheath, a thin transparent homogenous mem- brane, with a nucleus here and there on its inner wall; it is structureless and continuous. Is this Grey Sheath found on all Nerves ? No; it ig not found on fibres within substance of the brain or spinal cord. Describe the Structure of the White Fibres. They consist of— 1. An Axis CyninpEr—a pale, grey, cylindrical band in the centre. It is formed by fibrils imbedded in a clear or finely granular interstitial matter. It is often the only constituent at terminations, and always appears first in development. 2. Tas Waits Sueats (medullary sheath, or white substance of Schwann). This covering is not continuous; is not found at the central nor peripheral end; and there are also gaps in it throughout its course, these gaps or interruptions being known as the “nodes of Ranvier.” The white sheath refracts light strongly and has a double contour. In consists of alternate tubular segments (Schmidt’s segments) overlapping each other, Traversing the white substance is a honeycomb- like stroma, the meshes of which are filled with PRoroconE or Mye.ivg. This is soft, semi-fluid, and easily broken up, and is FATTY in nature, containing both nitrogen and phosphorous (Leicithin). The honeycomb framework is formed of neuro- keratin. 3. Tae Grey or Primitive SHeatyH.—lIt is colourless, transparent, and structureless and continuous; it dips down a little at the ‘nodes of Ranvier,” giving the appearance of constrictions. It is more resistant than the white substance, 55 On its inner surface there is a clear oval nucleus surrounded by a little protoplasm; there is usually one between each node, on alternate sides, more or less indenting the protoplasm. 4, Between the axis cylinder and the white substance is an interstitial matter which surrounds the axis cylinder and accumulates at the ‘nodes of Ranvier.” Describe the Effect of Reagents on the Various Parts of Nerve Fibres. CarRMiINE stains the axis cylinder, but does not affect the white sheath. Curomic Acip stains the white sheath opaque or brown, and on transverse section shows a concentric lamination. Osmic Acrp stains the white substance black, on account of its fatty nature, and also reveals the “nodes of Ranvier.” Nitrate oF Sitver stains the interstitial substance black. It soaks in at the nodes and stains the accumulated mass, and also makes its way for a short distance along the axis cylinder and stains the surrounding interstitial matter black. In this way crosses are shown, known as the “crosses of Ranvier.” The axis cylinder is stained bright red by picro-carmine, and purple by logwood. On transverse section we therefore see a red (or purple) dot in the centre (the axis cylinder), surrounded by a broad band of colourless matter (the white sheath), and outside all a fine narrow line (the grey or primitive sheath). Stute the Arrangement of Connective Tissue in Nerve Fibres. 1. There is a GeneraL Perineurium (the “epineurium ” of Klein) around the nerve TRUNK, and between the BUNDLES of fibres. 9, A SproraL Psrinzurium (the perineurium of Klein) around each bundle of fibres. 3. The endoneurium inside each bundle, and round each fibre. 56 ‘Which is the Chief Part of a Nerve Fibre ? The axis cylinder. What are the Proofs of this? 1. The axis cylinder is always continuous (so is the grey sheath along the course of the fibre), and always present everywhere. 2. In the brain and spinal cord the grey sheath is wanting. 3. The white sheath is not continuous, but is interrupted at the “ nodes of Ranvier.” 4, At the peripheral and central ends both sheaths disappear, but the axis cylinder persists. 5. The axis cylinder appears first in development. Describe the Leading Forms of Nerve Cells. 1, The typical Muntipotar Nerve Cex, such as is found in the anterior horn of the grey matter of the spinal cord. Its shape varies, and it consists of a nucleated mass of protoplasm with numerous processes, (a) The grey or protoplasm processes divide and sub- divide, and form a fine plexus (plexuses of Gerlach). (0) One process at least does not divide, but becomes directly continuous with a nerve fibre, and hence has been named the axis cylinder process. 2. The small cells in the cortex of the cerebellum have only grey processes. 3. The cells of the Gasserian ganglion have only axial cylinder processes. 4, In the cerebrum we find characteristic pyramidal nerve cells, with several processes. 57 5. In the cerebellum we find globular or pear-shaped cells (Purkinje’s cells), with a slender central process; and from the opposite or peripheral aspect of the cell there are two strong, antler-like branching processes. 6. In the human sympathetic we find multipolar cells, stellate in appearance, surrounded by a capsule of connective tissue. 7. In the ganglion of the posterior root of the spinal nerves, we find bi-polar cells. The cell is globular in shape and seems to be rather a nucleated enlargement of the axis cylinder. What is meant by Automatic ? Motions that result in protoplasm and its modifications, from causes within itself, without the aid of any external stimulus or liberator. How do Nerve Cells and Fibres Resemble and Differ from each other ? Both are excitable by external stimuli, but the fibre can only conduct nervous impulses, whereas the nerve cell can produce these impulses. Give Examples of Automatic Action. The movements of the heart are due to automatic discharges, from the cardiac ganglia. They can be influenced from without, however, as irritation of the endocardium accelerates discharges from the cardiac ganglia, reflexly. In other cases automatic action is in abeyance till the cells are excited—e.g., the cells in the medulla.connected with pharyngeal movements during deglutition—i.e., the movement or action is purely reflex. So also in a frog without its brain, the cells of the spinal cord do not act automatically till stimulated from the skin—e.g., by vinegar. 58 How are the Functions of Nerves found out ? 1. By experiment— (a) Cut a nerve—eg., vagus—and watch effect on respiration and heart. (b) Cut, and stimulate the cut end. In this way Sir Charles Bell was enabled to demonstrate the functions of the two roots of the spinal cord. (c) Removal of parts—e.g., of the brain—and then observe the results produced. 2. By observing the results of disease, in this way, Broca discovered the centre for speech. 3. Tracing the ultimate distribution of nerves anatomically —e.g., the fifth nerve to the buccinator muscle. 4. By the study of development. 5. By the Wallerian method. What Takes Place when a Nerve is Divided ? If rapid reunion be prevented, degeneration of the medullary sheath occurs in the part of the fibres cut off from the nerve centre. The axis cylinder loses its excitability, but does not degenerate. Describe this more Fully. When the nerve is cut, the part supplied by that nerve is paralysed, whether motor or sensory. If it unites rapidly, everything will be quickly all right again; if not, degeneration occurs. Excitability is at first increased for a short time and then decreased, in both cases passing from the cut end to the periphery. The white sheath then seems to undergo fatty degeneration, and breaks up into little rounded oily-looking masses. In two or three months it becomes very granular, and the grey sheath looks as if it had been filled with dust. This disappears, leaving the grey sheath, nuclei, and axis cylinder . the nuclei of the grey sheath may proliferate. 59 Why does it Degenerate ? Because the nerve fibres are cut off from their trophic centres. Who Proved this ? Waller, by his experiments on the spinal nerves. Give a Short Account of his Experiments. 1. He divided the motor root and found that the PERIPHERAL end degenerated, but not the end next the spinal cord. 2. He divided the posterior root between the cord and the ganglion, and the end next the spinal cord degenerated, but not the end next the ganglion. 3. He divided the conjoined roots, and then found that, in the case of both motor and sensory fibres, the peripheral ends degenerated, whereas the ends next the spinal cord did not. 4, He divided the posterior root on each side of the ganglion, and found that the ends next the ganglion did not degenerate, while the other two did—peripheral in the one case, central in the other. What is the Cause of this Degenerution ? It is because the nerves are cut off from their trophic centres. What do you mean by Trophic Centres ? It means that there are centres that preside over the-nutrition of nerves: mere blood supply is not enough to keep the nerves healthy. Where are the Centres for the Roots of the Spinal Nerves ? The trophic centres for the anTERIOR root are in the anterior horns of the cord: the trophic centres for the PosTERIoR root are in the ganglion on that root. 60 To what Theory has this given rise ? That trophic centres are necessary for healthy nutrition, and that the ones above mentioned are probably only a part of a great trophic system of nerves. When part of a Nerve is Excised, does it Unite again ? Yes, unless the gap is too large—more than an inch. It grows from the central end. If the Ends do not meet what Takes Place ? The central end becomes bulbous. What is Necessary before the Function is Regained ? Not only is it necessary that the axis cylinder be restored, but the white sheath must also be restored. Whether do Motor or Sensory Fibres Regain their Function first ? Sensory fibres regain their function before motor fibres. Why is this ? Probably because the peripheral end is subjected to influences (stimuli) from the periphery of the body, and this serves to keep up its nutrition till the central end has had time to grow. to meet it, Motor fibres are subject to no stimuli. Give a Classification of Nerve Fibres. I. Errerent, Excipent, orn Centrirugat— 1. Motor. 2. Secretory. 3. Trophic. Il. Arrerent, IncipENT, orn CenTRIPETAL— 1. Sensory. 2, Excito-motor and excito-secretory. 3. Inhibitory. III. Inver-centrat. 61 How do Sensory Nerves Terminate ? They may terminate in :— 1. Networks, or Plexuses, 2. In Special Organs, as— (a) Pacinian bodies. (b) End-bulbs, (c) Touch corpuscles. (ad) Rods and cones in the eye. (e) Taste-buds in the tongue. (f) Cells of Schultze, in the nose. (g) Organ of Corti, in the ear, etc Where do you Find the Plexus Termination ? It is very well seen in the anterior epithelium of the cornea, Where are Pacinian Bodies Found ? In the digital, plantar, pudic, and infra-orbital nerves. How do Nerves Terminate in Muscle ? 1. Non-Srripep Muscis.—They end in plexuses ; and, from these, fibrils are given off and run between the cells; and some say twigs enter the nuceli of the cells. 2, Srripep Musciz.—First in plexuses, and then a nerve tubule enters individual muscular fibres: the primitive sheath becomes fused with the sarcolemma, while the axis cylinder loses its medullary sheath and passes. through the sacrolemma, The axis cylinder then ends on the surface of the muscle substance, becoming imbedded in a flat granular mass, the END-PLATE of Kiihne. The end-plates viewed in profile form “ Doyére’s eminences.” What are the Various Forms of Motor Action? It may be— 1. Automatic. 2. Sensori-motor. 3. Reflex. 62 What are the Varieties of Automatic Motor Actions ? They may be— 1. Nervous. (a) Involuntary, as the heart. (6) Voluntary, as in the movements necessary for speech. 2. Non-nervous, as in amceboid and ciliary motion. What is meant by Sensori-Motor Action ? When a voluntary motor action immediately results from sensation, it is termed a sensori-motor action. Give an Exaniple. Reading aloud. How is this Brought About ? The sensory impressions are conveyed from the eye to the brain, and so reach the speaking centre; from this impulses pass to the centre and muscles concerned in speaking. What further Change may Take Place ? A sensori-motor action may, after due practice, come to be performed without sensation and volition—e.g., reading aloud unconsciously. What ts it then Called ? A reflex-motor action. What is a Reflex Act ? It essentially consists of the transmutation, by means of the irritable protoplasm of a nerve cell or centre, of afferent into efferent impulses. The impulse, however, is not simply REFLECTED, but is intensified, 63 Name the Machinery necessary for a Reflex Act. 1. A sensory surface. 2, An afferent or sensory nerve. 3. A nerve cell or centvre. 4. Efferent nerve. 5. Muscles. That is the simplest possible mechanism, as found in the medulla oblongata. In many cases, as in the spinal cord, we may have two or more sets of nerve centres, with inter-central nerves. Give a few Examples of Reflex Action. 1. Contraction oF THE Iris. (a) Sensory surface — Retina. (b) Afferent nerve == The optic. (c) Nerve centre = Corpora quadrigemina. (d) Efferent nerve = Third. (e) Muscle = Circular fibres of iris. 2. WINKING. (a) Sensory surface — Retina, as from a bright light ; or cornea, from a particle of dust in the eye. (>) Afferent nerve = Optic (for retina) or fifth (from cornea.) (c) Nerve centre = Corpora quadrigemina. (ad) Efferent nerve = The seventh or facial. (e) Muscle = Orbicularis palpebrarum. 3. First Resprration at Birra, from the impression of cold air on the skin. (a) Sensory surface = Skin. (b) Afferent nerves = Sensory of skin. (c) Nerve centre = Inspiratory centre in medulla, (d) Efferent nerves = Phrenics and _ intercostals chiefly. (e) Muscles == Diaphragm and intercostal muscles chiefly. 64 4, VoMITING FROM TICKLING THE FAvuces. (a) Sensory surface = The fauces. (b) Afferent nerves = Glosso-pharyngeal and fifth. (c) Nerve centre = In the medulla. (d) Efferent nerves == Phrenics, nerves to abdominal muscles and the vagi. (e) Muscles = Muscles of extraordinary expir- ation. 5, SNEEZING. (a) Sensory surface = Retina (as from a bright light, or the snow), nasal branch of fifth (as from a dent of cold air.) (b) Afferent nerves = Optic (from retina), nasal branch of fifth (from nose.) (c) Nerve centre == Centre of expiration in the medulla. (d) Efferent nerves = Nerves for extraordinary expiration — intercostals, phrenics, nerves to abdomi- nal muscles, etc. (e) Muscles = Muscles concerned in extra- ordinary expiration. Edinburgh: Printed by E. & §, Livinastonz, 4 Melbourne Place. | Jp err Fie vol Oy Cy. LIBRAR ae Nee & LW si Part II. Parewias CIRCULATION (CHIEFLY). 7 EDINBURGH: BE, eS. LIVINGSTONE. 18093. PRINTED BY E. & 8 LIVINGSTONE 4 MELBOURNE PLACE EDINBURGH. PHYSIOLOGY. PART II. NERVES— (Continunp ys Give other Examples of Nerves of various kinds concerned in Reflex Acts. 1. Both nerves concerned are cerebro-spinal, as in deglutition, sneezing, and coughing. 2. One, a cerebro-spinal ; the other probably sympathetic, as in the secretion of saliva, secretion of gastric juice, blushing, and pallor of the face from emotional causes. In such cases the AFFERENT nerve is cerebro-spinal, and the EFFERENT, sympathetic. 3, AFFERENT nerve may be sympathetic and the EFFERENT cerebro-spinal, as in the convulsions produced by worms, and in convulsions of hysteria. 4. Both nerves sympathetic, as in the secretion of the intestinal - fluids. What is meant by Inhibitory Action ? By this is meant that there are impulses that may diminish, or even arrest the evolution of energy in various MorToR cells, Give Examples. It may be— 1. Voluntary, as seen in the influence of will in arresting respiratory action, and in coughing, ete. 2. Involuntary, as seen in the action of the inferior cardiac branch of the vagus on the heart. Is it known in relation to Secretion ? No; it only occurs in relation to motor action, but not in relation to secretion. 4 What are the Special Functions of Nerve Cells ? 1. To excite motor, secretory, and inhibitory nerve fibres. 2. To produce the conscious state. 3. To exert a trophic, or nutritive influence on nerve fibres and muscles. What is meant by “ Excitability” of a Nerve Fibre ? It means that the nerve fibre in question has the power of conducting impulses. On what does the Amount of this Depend ? The amount depends on, and varies with— 1. The intensity and duration of the stimulus. 2. The degree of excitability of the tissue. How does the Strength and Duration of the Stimulus affect it ? If the stimulus be weak, it must act for a much longer time in order to produce the effect of a stronger stimulus. Give an Example. The toes of one foot of a pithed frog are dipped into a solution of sulphuric acid, 1 in 20, when the foot is quickly withdrawn. The toes of the other foot are dipped into a more dilute solution, 1 in 1000, and the foot is only withdrawn after a much longer period. How is this Explained ? It is due to the effect of the “Summation of Energy.” When the stimulus is weak, wave after wave passes to the nerve centre, and stays there till the next comes, and so on till the combined effect is so great that the reflex is now excited. Each wave as it comes, makes it stronger and stronger, as it were; and at last it moves the barrier, and the movement is produced. Give other Examples. A fish-bone or a hair in the throat: at first there is not . very much irritation, but it soon grows intolerable. So, also, in tetanus due to a lacerated nerve. 5 What Conditions affect the Excitability of Nerve ? 1. Temperature. 2. Nutrition. 3. Chemical agents, as curara, atropia, strychnia. 4. An electrical current. How does Temperature affect it ? Within reasonable limits, a rise increases; whereas a fall diminishes, How does Nutrition affect it ? When slightly defective, it at first increases ; later, it is lost entirely. . What ts the effect of an Electric Current ? It is said to throw the nerve into a state of “ electrotonus.” What is meant by this ? In the region of the negative pole an increase of the excita- bility is produced, whereas in the region of the positive pole it is lessened. This change in the excitability of the nerve in the region of the two electrodes, respectively, is called ‘ electrotonus.’ The positive pole is said to produce ANELECTROTONUS (excitability diminished), while the negative produces cATHELECTROTONUS (excitability increased). How is this Ascertained ? By means of a nerve-muscle preparation. A drop of a saturated solution of common salt is placed on the motor nerve between the electrodes and the muscle. This produces a feeble tetanus which is increased by the negative pole and diminished by the positive pole. It can also be tested by means of induction shocks. How does the Strength of the Current affect the ‘ Indifferent Point” ? In a MEDIUM current it is midway between the electrodes. In a sTRoNG, 1t approaches the negative pole. In a WEAK, lt approaches the positive pole. 6 At what point is the Excitability of Nerve greatest. It is greatest near the nerve centre. How is this Shown 2? With a “nerve-muscle preparation.” Stimulate the nerve with current of same intensity—(1) near the muscle; (2) near the nerve centre. The effect produced in the muscle was greater when the nerve was excited near the nerve centre— i.e., far away from the muscle. What Theory was founded upon this Experiment? Pfliiger’s “avalanche” theory of nerve action. The current was supposed to gather strength as it proceeded, How its this Disproved ? It is disproved by testing the reflexes at the above two points. A frog is narcotised with opium or pithed; the sciatic nerve is exposed in its whole length, but not divided. With this preparation it is found that the afferent fibres give a greater reflex effect on limb of opposite side when stimulated near nerve centre, than when stimulated at a distance from it. Why ts this ? Because the nerve is more excitable near the spinal cord ; from this point the excitability lessens as we pass outwards. Why is the Nerve more Excitable there ? Probably because it is nearer to the trophic centres. Does a Nerve undergo any Visible Change during Stimulation ? Not exactly. The only objective sign when a nerve is stimulated is the negative variation of the natural nerve current—.e., the natural electric current evolved by the nerve becoming less during nerve action. This can only be shown by the needle of the galvanometer. ¢ What are the main Facts as regards the Action of Electricity on Muscle and Nerve ? GALYVANIC,— 1. Applied to a nerve trunk, it only stimulates when the ~ current enters and when it leaves the trunk. 2. To a sensory termination, and to muscle, all the time of the flow as well. 3. It affects the muscular fibres directly, even when the nerves are all destroyed or degenerated. 4. The negative pole alone stimulates at closing, while the positive pole alone stimulates at opening. 5. The negative pole is the more powerful stimulus of the two. Farapic.—It acts more powerfully on the nerves; but in a muscle where the nerves have .been paralysed, the Faradic current may entirely fail as a stimulus, although the galvanic stream remains efficient. In other words, to be efficient, the Faradic current requires that the nerves in the muscle should be healthy, not degenerated. How is the Velocity of a Nerve Impulse Measured ? It was first measured by Helmholtz in the motor nerve of a frog. The gastrocnemius was hooked to a lever to record its contractions on the smoked plate of a pendulum myograph. The pendulum during its swing breaks the primary circuit of the induction machine, and the induction shock is given to the sciatic nerve as near as possible to the muscle. The pendulum is again set at the same side as before, and again allowed to swing, again breaking the primary circuit. This time, however, the induction shock is given to a part of the nerve as far from the muscle as possible. Thus we have on the smoked plate of the pendulum, two curves of contraction, arising from the same abscissa——the first due to stimulation of the nerve close to the muscle, the second due to stimulation at a distance from the muscle. The interval between these curves indicates the time taken by the nerve impulse to travel between the two points. How ts this Time Measured ? By recording the vibrations of a tuning-fork on the plate, allowed to swing before the point of the chronograph, held exactly below the point of the myographic lever. All that is to do, then, is to measure the length of the nerve, and calculate the velocity. What is the Actual Velocity ? 1. In frog’s motor nerve, with a moderate stimulus, about 85 feet per second. 2. In human motor nerve, about 111 feet per second. 3. In sensory nerves, about 140 feet per second. Is this a very Rapid Motion ? Not so very rapid. ) Diminished in the region of the positive pole. These conditions affect it, just in the direct proportion that they increase or diminish the excitability of the nerve. State what you know about the Electrical Currents in Muscle. Electricity is produced by living, not by dead muscle. The longitudinal surface of a muscle is positive, and the artificial transverse section is negative. The centre of the transverse section is the most negative part; and in a cylinder or band 9 of muscle with parallel fibres, the most positive part is a zone midway between the ends of the muscle. The current is strongest when the electrodes of the galvanometer are placed at these points. When placed at equal distances from the centre of the transverse section, or from the centre of the longitudinal ' surface, the needle does not move, because the currents passing from the two sides are equal and neutralise each other. What ts the Negative Variation ? The natural muscle current is weakened when the muscle is stimulated to contraction. This weakening is called the “negative variation,” and occurs in the latent period, and is over before the contraction begins. How can the Negative Variation be well Shown ? By means of experiment with a frog’s heart. The apex is cut off, and this forms an artificial transverse section, to which one electrode is applied, while the other electrode is placed on the uninjured surface of the ventricle. The negative variation is well seen at each contraction of the heart, by watching the galvanometer needle. What is Dr Bois Reymond’s Theory as to the Muscle Current ? His theory is that the muscle consists of polarised particles arranged in pairs, and the explanation of the negative variation he regards as due to a rotation of the particles, so as to diminish the positive potential at the longitudinal surface. What are Hermann’s Views ? He says there is no evidence of any current in living muscle AT REST, provided that its fibres have not been injured by section or otherwise; and that when uninjured muscle is excited, a “current of action,” the so-called NEGATIVE VARIATION, appears and disappears when excitement is over. This current results from the excited part becoming negative to the unexcited part of the muscle. He further states that when muscular fibres are cut across, as in the experiments above mentioned, an artificial current appears, owing to the injured part becoming negative to uninjured part. This “current of action” due to stimulation, has a direction the opposite of the artificial current, and so diminishes it. i 10 pe What are some of the Objections to this ? 1. Galvani’s last experiment. 2. The leaves of Venus’ fly-trap even when uninjured give off a stream of electricity ; and in the same way, if stimulated, there is a negative variation. 3. The currents are not mere transitory flashes, but last for some time, and must therefore be kept going on account of changes in the muscle (probably chemical), They disappear - as the irritation vanishes, 4. The current is strongest from the Equator to the cut section. This fact seems opposed to the idea that the cutting or death gives rise to the current. 5. Lay a nerve of an irritable muscle on frog’s living heart (which is 1so-gLucTRIC): the muscle contracts when the heart beats—due to the negative variation. Are these Similar Currents observed in Nerves ? Yes; they are much the same in every respect as they are in muscle. What is the Velocity of the “ Negative Variation” of Nerve Current ? It has the same velocity as the nerve impulse, about 85 feet or 28 meters per second. CIRCULATION. What are the Divisions of the Vascular System ? 1. The Blood vascular system. 2. The Lymphatic system. Are the Forces concerned Mechanical or Vital ? They are both to a certain extent: thus we have to deal with— 1. The mechanical principles of an elastic, hydraulic | apparatus. 2. The vital action of a nervo-muscular apparatus in the ‘heart, arteries, and veins. 11 Give a short Sketch of the different Parts. 1.. The Heart beating regularly, acting both as a force pump and as a suction pump. Its nerves are partly within itself, but it is also acted upon and governed by certain centres in the brain. 2. The Arrerigs, elastic and contractile, the muscular coat increasing in importance as the arteries lessen in size. 3. The Capituariges; the walls are elastic, not contractile, thin and permeable. 4, The Veins are both elastic and contractile, their total capacity being much greater than the arteries. What is the Condition of the Blood in the Arteries ? It is “‘ heaped up” in the arteries. Why ts this ? 1. The semi-contracted state of the arterioles—the small arteries, with their thick muscular coat. 2. The resistance offered by the capillaries, on account of the minute sub-division ; there is greater surface exposed, and hence increased friction and resistance. What is meant by “ Arterial Pressure” ? It is the pressure with which the blood tends to escape from the arteries. How is it Measured ? By means of a mercurial manometer. What is the Actual Pressure in the Carotid ? Three pounds two ounces to the square inch, On what does Pressure Depend ? 1. The rapidity of the inflow—z.e., the force of propulsion. 2. The rapidity of the outflow—i.e., the force of resistance, viz., the friction of the fluid against the walls of the vessels, 12 How does the Inflow or the Outflow vary ? 1. The rapidity of the inflow depends on, and varies with the heart. 2. The rapidity of the outflow depends on the contraction of the small arteries. Note the immense importance of the muscular coat of the small arteries. What is the Position and Structure of the Pericardium ? It is placed in the middle mediastinum of the chest. It is a closed cavity, the heart being pushed in, invaginating it. Its base is attached to the central tendon of the diaphragm, wall of the cesophagus, and the pleure. It is a FIBRO-SEROUS membrane, and projects most to the left side. Describe its Fibrous Layer. This is the external layer and consists of strong interlacing fibrous tissue. It is continued upon the large blood-vessels for some distance as tubular prolongations, which are gradually lost upon their coats. There are in all eight such prolongations —viz., the superior vena cava, the four pulmonary veins, aorta, and the right and left divisions of the pulmonary artery. The inferior vena cava has practically no covering from this layer of the pericardium, as it enters the heart through the central tendon of the diaphragm. Thus fixed, it keeps the heart from rocking about too much. Describe the Serous Layer. This is the internal layer, and lines the fibrous part of the pericardium, and is then reflected over the heart. It encloses the aorta and the pulmonary artery ina common sheath. Each of the great veins has its own investment, though that to the inferior vena cava is very short. What is the “ Vestigial Fold” ? It is a fold in the pericardium placed between the left pulmonary artery and the sub-adjacent pulmonary veins, and marks the position of the left superior vena cava in the embryo heart. 13 What is the Structure of the Serous Layer ? It consists of a single layer of squamous epithelium (ENDOTHELIUM). Give a rough account of the Structure and Position of the Heart. The heart is a hollow muscle, and consists of muscular fibres and fibrous rings for their attachment. In shape it is like a blunt cone; the base points upwards, backwards, and to the right, opposite the 4th to the 8th dorsal vertebra. The apex is directed downwards, forwards, and to the left, between the 5th and 6th ribs. Describe the Fibrous Rings. They are four in number, and surround the right and left auriculo-ventricular orifices, the aorta and the pulmonary artery. The fibrous tissue is continuous with that in the segments of the valves, and also serves for the attachment of the muscular fibres. Those of the aortic and left auriculo-ventricular open- ings are close together, practically confluent, and on boiling run into one. What is the Position of the Four Openings ? 1. The pulmonary artery is most anterior. 2. Next comes the aorta. 3. Close beside it, and a little to the left, is the left auriculo- ventricular opening. 4, While to the right, and a little further back, is the right auriculo-ventricular opening. How are the Muscular Fibres arranged ? The muscular fibres of the auricles are distinct from those of the ventricles. How are the Fibres of the Auricles arranged ? They consist of a superficial set common to both, and a deep set proper to each. 14 Describe the Superficial Set. They pass round both auricles in a transverse direction, forming a thin layer, most distinct on the anterior surface. Some of them dip into the inter-auricular septum. How are the Deep Fibres arranged ? The deep layer consists of two sets of fibres— 1. The Loopep, which pass over each auricle, and are fixed to the corresponding auriculo-ventricular rings. 2. The avuricutar, which encircle the appendices and are continued upon the vessels opening into it, and they also surround them. Are these Fibres equally distinct on all the Vessels ? No; but they are specially distinct upon the superior vena cava, and in the case of the pulmonary artery extend up to the root of the lung. How are the Ventricular Fibres arranged ? They consist of many layers. The outer and the inner layers are specially well marked. The outer extends from the rings at the base, in an oblique direction from above downwards, and from right to left, and at the apex get a sudden twist in the same direction as the hands of a watch, forming a whorl—those of the anterior surface curving round and entering the heart posteriorly, and vice versa. The apex of the heart is formed exclusively by the first and seventh layers. These layers are continuous and thin, and those in the inside have a direction reverse to those on the outside. The great mass of the sub- stance of the heart consists of the fibres between these two layers, and which pass in various directions. The fibres of the anterior surface dip down into the inter-ventricular groove ; at the posterior part they pass over it. Describe the Right Auricle. It consists of the sinus (or aTRium) and auricular appendix, It contains about two ounces, and is rather larger than the left. The sinus is quadrilateral, and is placed between the two ven cave. The aPrpENDIx resembles a dog’s ear in shape, and hence 15 its name “auricular.” It is a conical muscular pouch projecting from the sinus, to the left side, overlapping the root of the pulmonary artery. InsipE it is quite smooth, except in the auricle and adjacent anterior wall of the sinus where there are MUSCULI PECTINATI—the muscular substance being thrown into parallel ridges. What are the Openings into this Cavity ? 1. Superior vena cava—no valves. 2. Inferior vena cava—imperfect valve. 3. Coronary sinus—perfect valve. 4, Foramina Thebesii (mouths of small veins). 5. The auriculo-ventricular, the opening into the right ventricle; it admits three fingers up to about the second joint. What ts the “ Fossa Ovalis” ? It is the remains of the foramen ovale in the foetus, an opening between the right and left auricles. It is bounded above and at the sides by the “annulus ovalis.” What is the “ Tubercle of Lower” ? It is a slight projection between the openings of the superior and inferior vene cave, like a “Delta” at the mouth of a river. What ts the “ Valve” of the Inferior Vena Cava called ? It is called the “ Eustachian valve.” It is a cresentic fold of the lining membrane in front of the opening of the inferior vena cava, one end being prolonged into the anterior end of the “ annulus ovalis.” What is its use in the Foetus ? It serves to direct the blood from the inferior vena cava through the “foramen ovale” into the left auricle. What is the Valve of the Coronary Sinus called ? It is called the valve of Thebesius: it is the only vein of the heart that has a perfectly closing valve. 16 What takes the place of Valves in the other Veins ? Sphincters of muscular fibre around the openings of the _ other large veins serve instead of valves. Auricular contraction BEGINS at these sphincters, and spreads to the appendices and sinuses to drive the blood into the ventricles. Describe the Right Ventricle. It forms about two-thirds of the anterior surface of the heart, and is therefore sometimes called the anTERIOR ventricle. It does not quite extend to the apex. The upper. and left angle is prolonged into a conical form—the CONUS ARTERIOSUS, and from this the pulmonary artery springs. What is the Shape of the Cavity ? It is crescentic or semi-lunar in form, as the septum between it and the left ventricle bulges in. Its walls are much thinner than the left, and its capacity is probably slightly greater. Name its Openings. 1. The auriculo-ventricular, guarded by the tricuspid valve (three segments or cusps to this valve, hence the name). 2. The pulmonary artery, springs from the conus arteriosus, and is guarded by the semi-lunar valves. What are the “ Strings” attached to the Valves called ? They are called cHORDE TENDINEZ, and are attached to the ventricular surface, and come from the musculi papillares. How are they Attached ? 1, Some reach the attached margin of the valve, and are continuous with the fibrous rings. 2. Others are fixed to the central thickened part. 3. A third set are attached to the edges of the segments. Describe the Inner Surfuce of the Ventricle. The inner surface is marked by muscular bundles called COLUMN CARNEA, except in the conus arteriosus, which is quite smooth. 17 Name the Varieties of “ Columne Carne” ? They consist of three sets— 1. Those attached throughout their entire length—ends and margin, like the musculi pectinati of the auricle. 2. Those attached by their ends, but free in the centre. 3. Those attached by one end only, the other being free and giving attachment to the chorde tendines. What are the Third Set called ? They are only three to four in number, and are called the MUSCULI PAPILLARES. What ts the “ Moderator Band” ? It is a band that sometimes passes across from the base of the anterior papillary muscle to the ventricular septum. What is its Use ? It is to prevent over-distension of the thin-walled right ventricle, and is much better seen in the heart of some of the lower animals. Describe the Left Auricle. It resembles the right auricle. The srnus is cuboidal and is only seen from behind. The aprenp1x overlaps the root of the pulmonary artery, and is the only part of the auricle seen from the front. The muscuLi PEcTINATI are fewer and smaller than those in the right, and are confined to the inner surface of the appendix, What are its Openings ? 1. The four pulmonary veins: these open into the posterior part of the sinus, and are destitute of valves. 2. The auriculo-ventricular: this is smaller than the corre- sponding opening on the right side, and only admits two fingers up to about the second joint. Is there anything else worth noting ? Yes; a thumb-nail-like depression is seen in the auricular septum. B 18 What is this? It is the remains of the foramen ovale. Describe the Left Ventricle. It is chiefly situated behind (and sometimes therefore called the posterior). It is oval or round on section (not CRESCENTIC like the right), and its walls are about three times as thick as the walls of the right. The coLuMN# caRNEm are smaller and more numerous. The musculi papillares are collected into two groups. What are its Openings ? 1. The auriculo-ventricular, guarded by the mitral, or bicuspid, valve. 2. The aortic, in front and to the right of the auriculo- ventricular, guarded by the semi-lunar valves. Why do the Walls of the Ventricles vary so in Thickness ? The thick-walled left ventricle has to carry on the systemic or greater circulation, driving the blood through all parts of the body. The thin-walled right ventricle has only to carry on the pulmonary or lesser circulation, only driving the blood through the lungs. What are the Uses of the Musculi Papillares and the Chorde Tendinece ? The chord tendines spring from the ends of the musculi papillares, and pass to be attached to the segments of the auriculo-ventricular valves. When the heart contracts the MUSCULI shorten at the same time, and this keeps the cHorDE& tense, notwithstanding the contraction of the ventricles; and in this way the segments of the auriculo-ventricular valves _ are kept from being forced back into the auricles, and thus regurgitation is prevented. Note, in regard to the auricles, that the contraction begins at the venous openings. In the case of the pulmonary veins . it begins at the root of the lung, and in this way there is no need of valves for the venous openings. Further, note the use and great importance of the annular fibres of the auricles being prolonged round the mouths of these veins. 19 . What are the “ Valves” ? They are double folds of the endocardium enclosing fibrous tissue, continuous with and attached to that of the rings. Describe the right Aurieulo-Ventricular. It is called the tricuspid, because it consists of three cusps or segments. It has the usual structure of valves. The cusps are placed anterior, posterior, and left, the left is the largest. The valves are thicker in the centre, but thin and jagged at the edges. The convex margin is attached to the fibrous rings. The auricuLar surface is smooth, but the ventricular surface is rough. Why is the Auricular Surface Smooth ? It is so that there may be as little hindrance as possible to the entrance of blood from the auricle; were it rough, friction would be much increased. What makes the Ventricular Surface Rough ? The attachment of the chord tendines. How are the Chorde arranged ? The chord from any one papillary muscle do not all go to the same cusp, but are usually divided between two contiguous cusps. What is meant by the “ Safety Valve Action” of the Tricuspid ? It means that regurgitation takes place normally at this valve. It closes less perfectly than the mitral, and a little blood is driven back into the right auricle, producing a slight regurgitant flow and venous pulse a little way into the innominate veins. In ordinary cases the pulse does not pass further because of the valves. But should the tricuspid valve be diseased, the pulsation may pass into the internal and external jugular veins at the root of the neck; disease of the valves of the right side of the heart, however, is not very common. 20 What is the Use of this ‘ Safety Valve” Action? It prevents over distension of the right ventricle—e.g., in cases where the circulation through the lungs is impeded, as in great muscular effort. This is of great importance, because if the heart be over-distended sudden paralysis is apt to result. Does a Similar State exist on the Left side ? No; not naturally, only in cases of disease. It would be specially injurious at this valve, because the regurgitated blood would be sent back to the lungs, thus interfering with the proper aération of the blood, and inducing chronic disease of the lungs themselves as well. Describe the Mitral, or Bicuspid Valve. It is not so large as the tricuspid, and has only two segments. The segments are of unequal size, the larger one being between the aortic and the auriculo-ventricular openings. The valve normally completely closes the opening, and does not allow of any regurgitation. It is, however, often diseased, and with it the contiguous aortic valve. How do the two Cusps differ ? The anterior one, placed between the aortic and the auriculo-ventricular orifices, is the larger, the more movable, and is smooth on BoTH surfaces. Why ts it Smooth on both sides ? Because, along one surface the blood from the auricle passes, while close beside the other the blood makes its exit at the aortic orifice; and, being thus smooth on both sides, all un- necessary friction is avoided. Describe the Semilunar or Sigmoid Valves. These valves are placed at the aortic and pulmonary orifices. Each has three cusps of the usual general valve structure. The free border of each cusp is nearly straight, and is strengthened by a tendinous band, and about the middle there is a slight cartilagenous thickening, known as the corPuS aRANTIL. The fibrous tissue arises from the attached border and runs to this, occupying all the valve surface, except two thin lunated portions 21 at the edge of the valve, on each side of the corpus, known as the LuNuL&. When the valve is closed the lunule are brought into close contact, and stand upright in the column of blood, and the little nodules (conPoRA ARANTI) completely fill up the space between the three segments. What do we find above the Valve Segments ? Three small pouches—the “ Sinuszs or VaLsava.” How do the Valves of the Aortic differ from those of the Pulmonary Orifice ? The aortic are larger, thicker, and stronger, the lunule are wider, the corpora arantii more prominent, and the sinuses of Valsalva deeper. What are the Uses of the “ Sinuses of Valsalva” ? They allow an eddy stream round the valve segments, and thus support them against the axial stream; they are thus pre- vented from sticking to the walls of the vessel, and the blood in the “sinus” also helps to close them during diastole. Another possible use is, that the presence of this pouch allows that the column of blood in the aorta, for example, is not sustained by the valves alone, but also by the thick upper edge of the ventricles, upon which the pouches of the distended artery and the outer part of the semilunar valves repose. What is the Endocardium ? It is a serous membrane, lining the interior of the heart. It consists of connective tissue, elastic fibres, and Purkinje’s fibres, with a layer of endothelium on the free surface. There may also be a few non-striped muscular fibres. What are the Parts of the Cardiac Cycle ? 1. Auricular systole = one-ninth of the whole. 2. Ventricular systole = three-ninths of the whole. 3. Pause = five-ninths of the whole. It will be noticed therefore that the pause, or resting time of the heart, is as least as long as, and probably longer, than its working time. This “pause” is the only way in which the heart gets rest. 22 Describe the Cardiac Cycle. 1. Pausz.—During the pause the blood is flowing into both auricles AND VENTRICLES, from the venz cave, and the heart is being dilated. This dilatation acts like a suction pump, and the blood rushes towards the heart. 2. AurtcuLar SystoLe.—The ventricles are partly, and the auricles are completely filled, and then the sharp sudden auri- cular systole takes place. In this case the contraction begins in the veins, and runs towards the auricles in a peristaltic wave, and in the direction of the auriculo-ventricular orifices. 3. VentRicuLaR Systote.—The ventricles are now turgid, and completely dilated, and the auriculo-ventricular valves closed by the first effort at contraction on the part of the ventricles, and then the continued contraction forces the blood out at the pulmonary and aortic orifices. The heart then begins to dilate, and the aortic and pulmonary semilunar valves once more closed, and thus the cycle begins again. What Changes take place in the Shape and Position of the Ventricles during Contraction ? The ventricles become shorter, thicker, and feel tense and hard, and the BASE OF THE HEART APPROACHES THE APEX, The apex twists a little, and moves from left and behind to front and right. The aorta and pulmonary artery expand and elongate. During diastole this state of affairs is reversed. The apex does not change place in vertical direction, because the shortening of the ventricles is compensated by the lengthening of the great arteries. How is this Proved ? By means of three pins. If three pins, inserted through the chest wall into the apex, middle, and base of the ventricles, are carefully watched during the beats of the heart, the heads of those pins will be seen respectively, that of the first one, the lower, merely to quiver, that of the second one to incline slightly upwards, and that of the third one to incline upwards a good deal more. This shows that the apex of the heart does not move in the vertical direction, but that the base moves downwards and towards the apex. 23 What is Marey’s Method of Recording the Heart Movements ? In the case of the horse, for example, a cardiograph is applied to the chest wall, small elastic bags communicating with separate tambours introduced through the internal jugular vein into the right auricle and right ventricle. The movements are recorded by the ordinary apparatus. Where ts the “ Cardiac Impulse” felt ? It is felt most distinctly between the 5th and 6th left ribs, one or two inches from the sternum. What are the Causes of the “ Impulse” ? 1. It is due to the sudden onset of hardness of the substance of the ventricle ; and also 2. To a tilting forwards of the apex in a screw-like manner, due to the spiral arrangement of the superficial fibres of the ventricle ; it rotates from the left and behind to the front and tight. 3. Another possible cause is the tendency of the aorta to straighten itself when distended by the action of the ventricles. This is a kind of “recoil,” like a shot from a gun. In this case the resistance is the blood pressure. The “recoil,” however, is not evident because of the shortening of the heart, and is therefore lost sight of. It assists the tilting forwards of the apex—e.g., a similar thing is observed when the legs are crossed, one knee over the other, the toe is observed to be tilted forwards at each beat of the heart. Describe the Endocardial Pressure. It is measured by a mercurial manometer. The pressure in the ventricles is pLus, and therefore fluid tends to escape. This pressure in the left ventricle of a dog during systole will raise a column of mercury, one inch in diameter, 54 or 6 inches. In the right ventricle it is about 2 inches. During diastole or immediately after systole the pressure is minus in both auricles and ventricles, which thus act the part of a suction pump—.e., the pressure there being less than that of the atmosphere, the atmospheric pressure forces the blood towards it. The pressure in the left ventricle may be one-fifth of an inch below that of the atmosphere. Part of this “negative pressure” may be due 24 to respiration, but the great cause is the elasticity of the ventricles, The negative pressure is most marked in the left ventricle. The heart thus acts both as a “force” pump and as a “suction” pump, helping to refill itself. This “ suction- action” of the left ventricle is specially useful in helping the circulation through the lungs. What are the Sounds of the Heart ? They are two in number, called the first and second ; they follow each other in quick succession, and are followed by a pause. Describe the First Sound. It is deep, dull, prolonged and booming, and coincides with the cardiac impulse and just precedes the pulse. Where is it best heard ? It is best heard in the fifth intercostal space of the left side, two inches below and one to the inner side of the nipple. As regards Time, to what does it Correspond ? The contraction of the ventricles, the closure of the auriculo- ventricular valves, the opening of the semi-lunar valves, and the projection of blood into the arteries. What are its Causes ? 1. Its chief cause is the stretching and vibration of the auriculo-ventricular valves, and it disappears to a large extent, as the heart becomes empty. 2. The contraction of the muscular fibres of the heart itself, probably. 3. The shock of the heart against the chest wall. 4, The vibration of the blood itself. The first named, how- ever, is THE great cause—all the others are very secondary. Describe the Second Sound. It is shorter, sharper, higher in tone than the first sound, and has a somewhat flapping character. It immediately follows the pulse. 25 Where ts tt best heard ? It is best heard at the second right cartilage, close to the sternum. To what does it Correspond ? It begins with the diastole of the ventricles, and is only about half as long as the first sound. What is the Cause of the Second Sound ? It is due to the sudden tension and stretching of the fibres of the aortic and pulmonary semi-lunar valves as they are closed. This is believed to be the onzy cause, for if the - segments be hooked up the sound stops. To what does the First Sound Correspond ? It begins with the systole of the ventricles, and ends shortly before the ventricles begin to relax. Why is the Second Sound best heard at the Base? Because the aortic valve produces the greater part of the sound, and as at the second right costal cartilage the aorta comes nearest the surface, therefore the sound is best heard there. Where is the First Sound best heard ? At the apex of the heart. Why ? Because the mitral valve produces the greater part of this sound, and the blood flowing from the left auricle to the left ventricle carries the sound towards the apex. Where is the Pulmonary Valve Sound best heard ? It is heard best between the second and third left costal cartilages, Why ? Because at this point the pulmonary orifice is the most anterior, and nearest the surface of the chest wall. \ \ 26 ae Sete Where is the Tricuspid Valve Sound best heard ? It is heard best at the left side of the ensiform cartilage. Why so? Because the blood stream from the right auricle conducts the sound in that direction: here, therefore, “murmurs” are best heard. What are the Causes of Dilatation of the Heart ? The elasticity of the lungs aids the dilatation of the right side of the heart by drawing blood through the systemic veins into the chest. This force chiefly acts during INSPIRATION. The dilatation of the ventricles, in particular, is mainly due to the blood driven into them by the auricles, together with their own elastic expansion. The dilatation of the auricles is due to— 1. The suction of the relaxing ventricles. 2, Forces which impel the blood through the veins to the heart—z.e., the left ventricle. 3. The dilatation of the right auricle is also assisted by the elasticity of the lungs—the lungs cause a MINUS pressure, and thus the blood is forced by the pressure of the atmosphere towards the point of lessened pressure. INNERVATION OF THE HEART. State in a general way what you know of this. The beat of the heart is automatic—ie., it is caused by impulses that arise spontaneously in the heart itself. To what is this Automatism due ? It is due to the presence of ganglia in the walls of the heart. 27 Where is Bidder’s Ganglia? In the auriculo-ventricular sulcus of the frog’s heart. What is their Function ? They are motor centres for the ventricle. What is Descartes’ Experiment ? He separated the ventricle from the auricles by an incision on the auricular side of Bidder’s ganglia, and observed the effect on the movements of the heart. What was the Result observed ? Both auricles and ventricle go on beating, but the ventricle more slowly than the auricles. From this it is assumed that the ventricular ganglia can act independently, but appear to be more sluggish than the auricular ganglia: Describe the Experiment of Stannius. It consists of two parts. He first cut off the sinus venosus, with the ganglia of Remak, from the auricles. What was the Effect of this ? The sinus continues to beat, but the auricles and ventricle remain at rest. What was the next part of his Experiment ? The second part of his experiment was to cut off the ventricle with Bidder’s ganglia from the auricles. What took place then ? The ventricle resumed its beating, but the auricles remained at rest, although they still contain ganglia—viz., those of the auricular septum. 28 What is Bezold’s and Traube’s explanation ? They hold that the ganglia of Bidder and Remak are both motor, but that Remak’s are the more excitable and initiate the events of the cardiac cycle. That the ganglia in the auri- cular septum are probably inhibitory, though they are unable to inhibit Remak’s ganglia, unless aided by the inhibitory influence of the vagus; but that, when the ganglia of Remak are removed, they can completely inhibit the ventricular ganglia, as shown by the first part of the experiment of Stannius; and, further that when the ventricle with its ganglia is removed from the influence of the inhibitory ganglia of the auricles it again begins to beat, as shown by the second part of the experiment of Stannius, What are the other Cardiac Nerves ? Besides the ganglia in the heart there are the cardiac plexuses OUTSIDE the heart : from these, branches are sent in along with the arteries, and no doubt communicate with the intra-cardiac ganglia, Whence are these Nerves Derived ? From the cardiac branches of the sympathetics and vagi, and form the cardiac plexuses, Describe the Superficial Cardiac Plexus. It is formed by branches from the left superior cervical ganglion of the sympathetic, with the inferior cardiac branch of the left vagus, together with twigs from the deep plexus. It lies in the concavity of the arch of the aorta in front of the right branch of the pulmonary artery. In it we find the ganglion of Wrisberg. It gives off the anterior coronary plexus. Describe the Deep Plexus. It is formed by all the other cardiac branches of the sym- pathetics and vagi, together with branches from the superficial plexus. 29 Why does the Heart beat faster when one walks fast or runs ? On account of the muscular effort, more venous blood is brought to the heart in a given time; its temperature is also slightly raised. In this way the endocardium is stimulated by the blood, and this the ganglia are affected and discharge their energy faster, and hence the increased activity. It is probable that this stimulation of the endocardium by means of the blood is the chief cause of the so-called automatic discharge of energy by the intra-cardiac ganglia. At the same time the heart’s action is essentially automatic, though it can thus be affected by influences from without—e.g., as from the brain, by emotions, etc, What are the Cardiac Branches of the Vagus ? 1. The Inferior Cardiac. 2. The Superior Cardiac. Describe the Course of the Inferior Cardiac. It consists of one large branch which, on the riaut side, descends along the innominate artery and joins one of the cardiac, and through it passes to the DEEP cardiac plexus; on the Lert side, it crosses the arch of the aorta and joins the SUPERFICIAL cardiac plexus, What ts tts Function ? It is the inhibitory nerve of the heart. (Note the two I’s—Inferior—Inhibitory). What is the Effect of Cutting this Nerve ? THE HEART BEATS MORE RAPIDLY, as the impulses sent from the brain through this nerve to inhibit the heart’s action no longer, of course, reach the heart, and, therefore, since the restraining power is cut off, the heart beats faster. The same effect will be produced by cutting the vagi in the neck, as this cuts the fibres conveying the impulses down the cord from the brain. 30 What are the Effects of Stimulating the Cut Ends? 1. Stimulate the lower end— (a) Gently, the heart is again inhibited just as if the nerve impulses again reached it from the brain. (b) More strongly, the heart is slowed or stopped, as the inhibitory power is so much increased. 2, Stimulate the upper end—no appreciable effect. What is the Condition of the Heart when stopped by Stimula- | tion of the Inhibitory Nerve? If stopped by stimulation of the lower end of the cut inferior cardiac branch of vagus, it swells up and is brought to a state of repose in DIASTOLE, not systole. How ts this Effect Produced ? By the influence exerted on the cardiac ganglia, not from. any effect on the muscuLaR fibres. How is this Proved ? Because if the muscle of the heart be stimulated during this period the ventricles contract as usual. Might it not be due to Spasm of the Blood -Vessels ? It is not due to this, because in the frog’s heart there are no blood-vessels, and the same phenomena are observed there, It must thus take effect through the cardiac ganglia, arresting their evolution of energy — efferent impulses from the brain descending through vagi to heart. Is the Beat much Quickened ? In the case of the dog, it may beat one-fourth more rapidly, Is the Cardio-Inhibitory Mechanism always in operation ? Yes. 31 How is this Proved ? ‘When the vagi are cut in the neck, the heart always beats faster; or, when the cardio-inhibitory mechanism is paralysed by atropia, the same result is observed. Are the Cardio-Inhibitory Fibres found in the Vagus throughout tts entire Course 2 No, they are not found in the vagus at its superficial origin on the surface of the brain. Where do they come from, then ? They are found in the spinal accessory nerve, and enter the vagus with the large root of that nerve (the spinal accessory) near the base of the brain. How is this Proved ? Cut the spinal accessory at its root, and the heart beats more rapidly, just as when the vagi are cut in the neck. What is the Function of the Superior Cardiac Branches of the Vagus ? They form the sENSoRY nerves of the heart, (Note the two S’s—Superior—Sensory.) What is their Origin ? They arise from the upper and lower parts of the cervical portion of the vagus. What is the Effect of Dividing these Branches ? There is no noticable effect. What is the Result of Stimulating the Lower End of the divided Nerve ? There is no effect. 32 What are the Results of Stimulating the Upper End, then? 1. Pain is felt, as it is a sensory nerve. 2. The cardio-inhibitory centre is excited, and the heart therefore slowed, with a consequent slight fall in the blood pressure. 3. There is marked reflex dilatation of the abdominal blood vessels, with consequent great lowering of the systemic arterial pressure. How are these Effects Produced ? The nerve probably contains vaso-inhibitory fibres, as well as sensory, and the stimulation thus inhibits the vaso-motor centre. This centre is always in a state of activity, but the stimulation lessens its activity and retards its evolution of energy, and hence the dilatation of the blood-vessels of the abdomen, as the cells specially affected are those that preside over that large vascular area. What other Name ts given to this Nerve? It is called “Depressor,” because of this great lowering of the blood pressure. Is this Nerve constantly in Action ? No; but it is not known exactly when it acts. What are the Special Points about this Nerve (Superior Cardiac of Vagus), then ? 1. It is sensory to the heart. 2. It seems to contain fibres that can affect the cardio- inhibitory centre, stimulating it and slowing the heart. 3. It contains vaso-inhibitory fibres that affect the vaso- motor centre in the medulla, or that part that presides over the blood-vessels of the abdomen, and thus causes dilatation of these vessels. 33 What ts the Special Vaso-Motor Nerve of the Abdomen ? The great splanchnic nerve; when cut, there is a great dilatation of the vessels in the abdomen. What other Conditions may affect the activity of the Cardio- Inhibitory Centre ? 1. Stimulation of ordinary sensory nerves may increase its activity and slow the heart. 2. Increase of blood pressure in the brain increases its activity, and thus slows the heart and allows the blood pressure to fall again. 3. Retard respiration so as to produce a venous condition of the blood; and in the raBsir this excites the centre and greatly retards the heart. 4, Emotions, whether of joy or sorrow, may fatally inhibit the heart. Is the Cardio-Inhibitory Centre Automatic or Reflex ? It is not known, but it is probably automatic like that of the vaso-motor centre. How is the Efect of Blood Pressure in this Centre Studied ? By clamping the abdominal aorta when the pressure in the brain is much increased, and the heart slowed; but if the vagi are previously divided this effect on the heart is not observed. What do you know of the Cardiac Branches of the Sympathetic ? They probably arise in a cardio-motor centre in the medulla. The fibres pass down from the medulla, and then leave the cord by the last cervical or first dorsal ganglia of the sympathetic, and thence to the heart, either directly, or else through the superior cardiac of vagus. — What is the “ Nervus Accelerans” ? It is one of the above branches, and passes from the inferior cervical ganglion to the heart. c 34 Is this Nerve usually in a state of Activity ? No. How is this Proved ? When the nerve is cut, no change is observed in the move- ments of the heart. What takes Place if the Ends are Stimulated ? The heart is accelerated by stimulating the PERIPHERAL end of the divided nerve. How is this Nerve and Centre usually Excited ? Probably chiefly by emotions, and by reflex influences : as from an irritable state of the stomach, causing palpitation. Note therefore— 1. That the “Nervus Accelerans” is not always in a state of activity. 2. The Superior cardiac branch of the vagus (Sensory) is not always in a state of activity. 3. That the Inferior cardiac branch of the vagus (Inhibitory) is constantly in a state of activity. Further, that the heart has three sets of nerves— 1. From the ganglia in its walls, 2. From the vagi. 3. From the sympathetic. And lastly note the functions of ‘each set-— 1, The ganglia for the usual regular rhythmic movements. 2, The vagus (see page 29). 3. The sympathetic (see page 33), 35 Name a few other Conditions that affect the Heart’s action. 1, Temperature—heat tends to quicken, and cold to slow the heart’s motion. 2. Blood pressure. 3. Muscular exertion. 4, Atmospheric pressure—at the top of a mountain, it is quickened ; at the bottom of a mine, slowed. 5. Position of the body—most rapid in the erect posture ; slowest in the recumbent (difference, 12 to 15 beats per minute). 6. Age and Sex—fastest in young children, less so in adults —fcetus In uTERO, 140 per minute; adult female, 75 to 80; adult male, 70 per minute. 7. Various drugs and chemical agents. 8. Period of the day. What is the Effect of Increased Systemic Pressure ? The heart is retarded because the cardio-inhibitory centre in the medulla is made more active; and in this way the blood pressure tends to fall to normal again. In cases of diminished pressure the effect is the reverse. If the Pressure be suddenly Increased, what may be the Result ? In cases of suDDEN increase of the systemic pressure, as when the muscles are in a state of spasm, all the small peri- pheral arteries are compressed, and the blood is kept back in the aorta, thus increasing the pressure immensely. In such a case the left ventricle may not be able to contract, but become over-distended and paralysed, and sudden death result; this is all the more likely to happen should there be any organic disease of the heart present. What is the Effect of Increased Venous Pressure ? When the venous return to the heart is quickened, then the heart beats faster, probably because the venous blood stimulates the endocardium, and this in turn excites the muscular fibres. 36 What its the Effect of Muscular Eaxertion ? The heart’s action is quickened— 1. By quickening the venous return to the right auricle. 2. By raising the temperature of the blood. What are the Risks of Muscular Effort ? Should the heart be weak, sudden failure may be the result— 1. By increasing the resistance to the out-flow from the left ventricle. 2. By hastening the venous return to the right side, so that the heart is unable to expel it fast enough. In both cases the corresponding ventricle becomes over- distended and paralysed. State the action of various Poisons on the Heart. 1. Nicotinz, Curarz, and Conrum paralyse the cardio- inhibitory nerve trunks, but not the very peripheral terminations. How is this known ? Because stimulation of the trunk of the vagus is unable to slow the heart, but if the electrodes be applied to the sinus veNosus the heart is slowed as usual. 2, Piuocarpine and Muscarin stimulate the whole of the cardio-inhibitory mechanism, and so cause the heart to stop in a state of diastole. CaLaBar BEAN acts in a similar way, but will not stop it in diastole. 3. Arropia, Hyoscyamine, and Daturine, paralyse the whole inhibitory mechanism. Stimulation of the trunk of the vagus and of the sinus venosus are alike without effect. Atropia is directly antagonistic to Calabar bean and pilocarpine, and will restore the beat. It paralyses the part that the others stimulate 37 What is the Effect of Digitalis on the Heart ? It increases the force of contractions of the ventricles, not the auricles. Too large a dose will stop the ventricles in a state of spasm, while the auricles still go on beating. Mention some Pecultartties in the Circulation in different parts. 1. The Portan Vern, with its two sets of capillaries; it begins in capillaries in the intestines, and ends in capillaries in the liver. What other Vessel does this also ? The efferent vessel of the Malphigian tufts of the kidney. 2. In the Crantum.—Four large arterial trunks enter the cranium ; they are very tortuous and traverse bony canals and anastomose to form a circle at the base of the brain, and this secures a free and full blood supply, even though one or more of the trunks were blocked. The vessels divide in the pia mater, and LONG SLENDER capillaries enter the brain substance at all points: the supply is thus perfect and agzntLz. The veins are peculiar and are called sinuses; the cranium has unyielding walls ; and the vessels, therefore, are not subject to atmospheric pressure. 3. Pulmonary Circulation. — This is peculiar, in the fact that the veins contain arterial, while the arteries contain venous blood. The vessels do not anastomose much, have no valves, the capillaries are large, very numerous and very short, with very short loops. The velocity is great and the pressure less than usual. 4. The blood in the renal vein is probably the purest in the body, as it is purified arterial blood, and the quantity passing through the kidney is so great that it is not reduced to the venous condition. Describe the Structure of the Capillaries. They usually consist of nothing more than a layer of squamous endothelium ; the edges of the cells are very tortuous. In the cement substance between the cells, little apertures may 38 be seen during distension ; these are called stomata, and it is probably through these apertures that diapedesis takes place. The cells are elastic, and are CAPABLE OF ALTERING THEIR SHAPE, There is no muscular coat. Their size varies from y355 tO sso0 part of an inch. Name some Exceptions to the above. In the retina, pia mater, and ovaries there is, in addition, a thin layer of connective tissue as well. How many Coats has an Artery got? Arteries have three coats. What are the Coats Called ? 1. Internal or Tunica Intima. 2. Middle or Tunica Media. 3. External or Tunica Adventitia. Describe the Internal Coat. It consists of three layers, and can be readily stripped off the inner surface of the artery as a transparent, colourless, elastic, and brittle membrane. Its layers are— 1. An endothelial lining, consisting of a single layer of thin elongated cells with nuclei. The edges of the cells are not very tortuous (not so much as in the case of capillaries), and their shape varies. 2. A layer of sub-endothelial connective tissue, consisting of white fibres and delicate stellate connective tissue corpuscles. 3. The elastic lamina. This forms the chief thickness of the inner coat, and is formed by several strata. It consists of yellow elastic fibres in the form of a MEMBRANE; it is homo- geneous or perforated, and marked with longitudinal pale streaks. When stripped off, the ends curl up. The entire internal coat is very brittle. 39 What is this Elastic Layer sometimes Called ? The ‘fenestrated membrane of Henle.” Is it always like a Membrane ? No; in the basilar artery it is fibrous, not mombranous. Describe the Middle Coat. It consists chiefly of layers of non-striped muscular fibres, arranged transversly, so as to clasp the vessel. It also contains some white and yellow fibrous tissue mixed with the muscular bundles. This coat is also very brittle. Does it vary at all in different Arteries ? Yes ; in passing from the larger to the smaller arteries the MUSCULAR part increases in thickness—both relative and actual. But in passing from the smaller to the larger there is more and more elastic tissue—e.g., in the first part of the aorta the pro- portion of elastic to muscular tissue is very much increased. Describe the External Coat. It consists chiefly of longitudinal bundles of white connective tissue, with some elastic fibres mixed with them. This coat is very tough and resistant. Name some Peculiarities in regard to the Structure of Arteries. In the renal, carotids, and mesenteric, there is an external elastic lamina, and in these, therefore, the muscular coat is enclosed between elastic laminw. The arteries in the cavity of the cranium and spinal canal have thinner coats in proportion to their size than ordinary arteries. This is due to thinness of the external and middle coats. 40 Describe the Structure of the Veins. In structure they resemble arteries, only their coats are thinner, and they collapse when cut. The BNDOTHELIAL SCALES are shorter and broader than in the arteries. The MIDDLE coaT is much thinner, but contains more white connective tissue. The ovreR coat is relatively thicker. How else do the Veins Differ from Arteries ? Veins have valves. Describe their Structure. The valves consist of semilunar folds of the internal coat with some connective tissue; they usually consist of two flaps, the apices of which point towards the heart in the lower part of the body. What Purpose do they Serve ? They prevent reflux of blood towards the capillaries. Where are they most Numerous ? In the veins of the legs and neck. Are they present in all Veins ? No; they are absent for the most part in veins in the great cavities of the body, as the cranium, chest, and abdomen—as the hepatic, portal, renal, uterine, pulmonary, etc. What are the Vasa Vasorum ? They are the small vessels that nourish the coats of arteries and veins; they chiefly ramify in the outer coat. 4] Are Arteries Contractile ? Yes; all arteries and veins are contractile, and are always in a state of slight tension, spoken of as “tonic contraction,” or “tone.” They are also elastic. ' Are Capillaries Contractile ? No; they are not contractile, but they are elastic, and changes in calibre are due to changes in the blood pressure. When an Artery contracts, how is its Dilatation brought about again ? 1. By its own elasticity. 2. By the blood pressure. How are Changes in the Calibre of Vessels supposed to be brought about ? By the influence of vaso-motor (‘‘vaso-constrictor”), and vaso-inhibitory (‘“ vaso-dilator”) nerves. What ts the Position of the Vaso-Motor Centre ? It is placed chiefly in the pons varolii, and the medulla oblongata: it reaches from near the upper part of the pons to within five millimetres of the calamus scriptorius. Are there any other Vaso-Motor Centres ? Yes; there are some vaso-motor cells— 1, In the spinal cord. 2. There are also peripherally placed vaso-motor centres — ¢.g., aS in connection with the sub- maxillary gland. Note well, therefore, the THREE sets of vaso-motor centres. 42 Describe the Course of the Vaso-Motor Fibres. Some pass from the general centre in the pons and medulla into the fifth, vagi, and ninth cranial nerves. But most of the fibres pass down the lateral columns of the cord, and begin to leave it, chiefly through the anterior nerve roots, at the lower part of the neck, and also all down the dorsal and lumbar part of the cord. From the anterior nerve roots they pass into the sympathetic ganglia (by means of the “RAMI COMMUNICANTES”), and then pass to the blood-vessels, either directly from the sympathetic plexuses, or else rejoin the cerebro-spinal nerves, and then pass with them to the blood-vessels. In what Position are Special Ganglia Found ? In the nerves near the salivary glands, tongue, lung, and in the abdomen and pelvis. How can Vaso-Motor Action be Proved ? By means of Bernard’s experiment on the cervical sym- pathetic nerve of the rabbit. Describe this Hxperiment. First note the condition of the ear and side of the head and neck before division of the nerve. When the nerve is cut the ear of that side becomes red and gorged with blood, the vessels being enlarged, and so also with the vessels at the side of the head ; the temperature also of the parts is raised. There ‘is also an effect on the eye of that side. What does this Prove ? It proves that impulses are aLways passing from the vaso- motor centre to the blood-vessels and constricting them. What happens if the Divided Nerve be Stimulated ? If the peripheral end be stimulated the engorged vessels become constricted, the ear becomes paler than before and colder than the other one. 43 What other Experiments are performed to confirm this ? 1. Divide the nerve trunk below the lowest cervical ganglion, and there is no action on the ear. 2. Cut the “Rami communicantes” of the lowest cervical ganglion, and the result is the same as in cutting the sym- pathetic in the neck. 3. Also, by dividing the anterior nerve roots, the effect is the same. 4. Also, by cutting the cord just below the medulla, the effect is the same. In Division of other Nerves are similar Effects Observed ? Yes, Give Examples. Division of the great splanchnic nerve produces similar effects on the blood-vessels of the abdomen. So also, by division of the sciatic we see similar effects on the vessels of the foot. How is the Position of the great Vaso-Motor Centre ascertained ? In the first place, a manometer is placed in an artery, say the femoral, to measure the arterial pressure. A spinal nerve, say the sciatic, is next divided and the central end stimulated. As a result of this there is a rise in the blood pressure, owing to reflex stimulation of the vaso-motor centre in the pons and medulla. The brain is then sliced away above the pons, but there is no fall in pressure, and the sciatic reflex effect is as great as before; because the vaso-motor centre does not extend into the brain above pons. Pons and medulla are now gradually sliced away from above downwards, and the blood pressure falls, and the sciatic reflex effect, becomes less and less after every slice, because the vaso- motor centre is gradually removed. 44 Is the Centre Confined to the Pons and Medulla? No; though Ludwig and Owsjannikow believed that it was, because they found no further effect on slicing away the spinal cord. Whose Experiments Corrected this Error of Observation ? Those of Lister and Schiff, who showed that some vaso- motor cells are also found in the spinal cord. How did Lister prove it ? By watching the effect of successive sections of a frog’s spinal cord on the calibre of the vessels of the web. As the sections were made lower and lower down, the dilatation of the vessels of the web became greater and greater, because every section removed the foot from the influence of so many more vaso-motor cells in the grey matter of the cord. How did Schiff Experiment ? He noted the effect of successive sections of a dog’s spinal cord on the temperature of a hind foot. A thermometer was placed between the dog’s toes, and as the sections were made lower and lower down the temperature rose higher and higher. Do Vessels regain their Tonicity again after Section of Vaso- Motor Nerves ? Yes; and that too even in parts, as the skin and muscles, where there are no ganglia that can possibly act as vaso-motor centres. It is the same even when vaso-motor centres are removed — e¢g., remove the superior cervical ganglion in a rabbit, the vessels of the ear will nevertheless ultimately regain their usual size. Is the Vaso-Motor Centre always in action ? Yes, it is in constant activity, and this is probably automatic. It is constantly discharging automatic impulses. Rhythmical variations in size are seen in the vessels of the rabbit’s ear, and of the frog’s foot, not due to the action of the heart. 45 Name some of the Conditions that Influence the Activity of this Centre. 1. Tue State or tas Bioop.—If the blood contains too little oxygen and too much carbonic acid, the centre is excited, there is a general constriction of the blood-vessels and a con- sequent rise of the blood pressure. 2. Mentan States.—Fear or intense anger causes con- striction of the vessels, and the face becomes pale. Shame and anger sometimes cause dilatation, and the face flushes, as in “ blushing.” 3. StimuLation or Sensory Nervss, as stimulation of the cranial end of the superior cardiac branch of the vagus (the DEPRESSOR NERVE) inhibits the activity of the cells that preside over the blood-vessels of the abdomen: dilatation only is pro- duced, it does not cause constriction (see page 32). Is tt the same with ordinary Sensory Nerves. No; the effect in this case is usually double — inhibition of one set of cells, and excitement of another set. That is, inhibition of those cells in the general vaso-motor centre that preside over the vessels of the part to which the nerve is dis- tributed, and excitement of the other cells in the vaso-motor centre. What is the Result of this ? The vessels are reflexly dilated in the district to which the nerve belongs, and reflexly contracted in the rest of the body. Who first Discovered this Local Dilatation ? Bernard; on stimulating the cunrrat end of the divided great auricular nerve in the ear of the rabbit. What is the object of this Inhibition, and name a familiar Example ? When there is a necessity for more food (or blood) to the tissues, the afferent nerves are thrown into action and cause 46 reflex inhibition of the vaso-motor centre—eg., when food is introduced into the stomach the mucous membrane flushes with blood. Cut the vagus, the blood disappears; stimulate the lower end, there is no change in the blood-vessels, therefore, the effect was not due to efferent impulses: stimulate the upper end, and the blood-vessels again dilate. What follows from this ? That it is very unwise for anyone to undertake serious mental or physical efforts immediately after a meal, for the blood cannot be in two places at one time—eg., the brain and the stomach. How do the Vaso-Inhibitory Fibres probably act ? They may cause the muscular fibres of the wall of the vessel to contract TRANSVERSELY, not longitudinally, so that the fibres would be lengthened; or perhaps they may simply inhibit the state of tonic contraction of the arterioles and then the blood pressure would dilate them. What are the Effects of Dilatation ? Loca Errects.—More blood passes through the artery, and a pulse may appear in the veins, because the elasticity of the arterial wall, that converted the intermittent into a continuous flow, is lost: the blood passing through loses less oxygen, and is more arterial in hue. GENERAL Errect.—Lowering of. general arterial pressure. Name a supposed peripherally-pluced Vaso-Motor Centre. The sub-maxillary ganglion. What Efferent Nerves are Distributed to the Vessels of this Gland ? Two sets, viz.— 1. Sympathetic. 2. Chorda tympani branch of portio dura. 47 What is the Function of the Sympathetic ? It contains vaso-motor fibres from the general vaso-motor centre. The action of these fibres seem to be slight, because their division causes but little dilatation of the vessels in the gland. ‘ What are the Functions of the Chorda Tympani? It contains vaso-inhibitory and secretory fibres. What is the Result of Dividing this Nerve and Stimulating its Peripheral end ? 1. The vessels dilate to a marked degree. 2. There is increased secretion. Are these two acts interdependent ? No; for paralyse the secretory fibres by atropia, and stim- ulate as before: there is the same dilatation of the vessels, but no secretion. What is the Function of the Vaso-Inhibitory Fibres ? They inhibit the vaso-motor ganglia in the gland. How is this usually brought about ? Reflexly by stimulation of the terminations of the lingual nerve in the mouth. Compare the Innervation of the Heart and Blood- Vessels. In the heart the inhibitory nerve is always in action. In the blood-vessels the motor nerves are always in action, and not the inhibitory. Name the. Sets of Fibres in a Nerve going to an ordinary Muscle—e.g., the Mylo-hyoid of Frog. 1. Motor for the muscle itself. 2. Vaso-motor for the muscular coats of the arteries. 3. Vaso-inhibitory fibres. 48 What follows Division of such a Nerve? 1. The muscle is paralysed. 2. The vessels dilate for a time because the vaso-motor fibres are paralysed, but they soon recover their tone. What happens when the Distal end is Stimulated ? 1. The vessels dilate. 9. The muscle contracts. Ts it the same in a Curarised Muscle ? No; the vessels dilate as before, but the muscle does not contract, because curara paralyses the peripheral ends of motor nerves. How do Vaso-Inhibitory Fibres effect Dilatation ? 1. By acting on the general vaso-motor centre, or 2. By action on peripheral mechanisms. How is the Blood Supply to a Tissue Regulated ? The vaso-motor nerves are usually in a state of slight action, keeping the arterioles semi-contracted ; and it is supposed that when a tissue wants an increased supply of blood it throws some vaso-inhibitory fibres into action, and thus causes the vessels to dilate. What is the Objection to this Explanation ? That when the sensory nerves, which contain the vaso- inhibitory fibres, of a part have been divided, it is still possible by irritating the part to bring about a dilatation of vessels although the vaso-inhibitory fibres are no longer in action. What are the Powers that move the Blood ? 1. The heart. 2. The elasticity of the lungs. 3. Extraneous muscular compression. 49 What other Powers have been Suggested ? 1. Contraction of the muscular fibres of the vessels them- selves. 2. The attraction of tissues—“ vis a fronte.” How does the Heart act ? In two ways— 1. Asa force pump, forcing the blood into the arteries. 2. As a suction pump—.e., as the ventricles dilate, the pressure in their neighbourhood is lessened, and then the pressure of the atmosphere drives the blood through the veins towards the heart. How does the Elasticity of the Lungs assist ? Much the same way as the suction-pump action of the heart: they “draw” the blood into the chest through the superior vena cava, chiefly during inspiration. Further, part of the atmos- pheric pressure inside the lungs is counterbalanced by their elasticity, and thus the pressure on the vessels in the chest is that much less than the pressure on the skin, or the rest of the body. How does Extraneous Muscular Compression act ? It acts by compressing the veins—e.g., of the limbs, and the blood is compelled to move towards the heart on account of the direction of the valves. Which is the most important Power ? The heart. Muscular compression could be done without ; as, for example, it is absent in sleep. So also the elasticity of the lungs could be done without; for, open the chest wall, and the circulation will still be carried on. The heart is able itself alone to carry on the circulation. D 50 Does the so-called Contractility of the Vessels assist the Circulation 2 There is not sufficient evidence that the muscular fibres of the vessels of the vERTEBRATA assist in propelling the blood, except perhaps in the case of the bat’s wing, and the ear of the rabbit, where rhythmical contractions of veins may assist in moving the blood towards the heart. The contractions of the vessels, however, are not synchronous with the beat of the heart, and are as likely, therefore, to retard as to assist the blood-flow. They are due to variations of excitement of the vaso-motor centre in the medulla. What ts the “ Vis a Fronte” ? The supposed attraction of the tissues; but the only real “vis a fronte” consists of the elasticity of the lungs, and the suction-pump action of the heart. What gave rise to the “ Attraction of Tissues” idea ? 1. The arteries were found empty after death. 2, The increased supply of blood to places where active growth is in progress—e.g., the antlers of stag. Why are the Arteries Empty after Death ? 1. The suction power of the heart and lungs. 2. Contraction of the arteries after death. 3. Rigor mortis; the muscles squeeze the blood throuch the veins. t What is meant by the “ Blood Pressure” ? It is the force with which the blood tends to escape from any blood-vessel. ‘51 On what does it Depend ? On the amount of blood relative to the capacity of the blood-vessel. The total amount of blood is about constant, so that any variation of pressure in any given part of the body depends on the rate of blood-flow into and out of that part. In other words, the blood pressure in any part of the vascular system depends on the force of propulsion and the force of resistance. Where ts the Resistance most marked ? In the arterioles and capillaries. Describe the Pressure ? It is greatest by far in the arteries nearest the heart, less in the capillaries, and least in the veins. At the beginning of the aorta the pressure is greatest, and lessens as it proceeds; there is a decided fall in the capillaries, and a great fall in the veins. The pressure is positive in the arteries, capillaries, and veins, except in the systemic veins near and in the chest, in which the pressure is negative during inspiration. To what is this Negative Pressure due ? To the elasticity of the lungs and heart. What is the Actual Pressure in the Carotid Artery ? It is 3 lbs. 2 oz. to the square inch. How did Hales measure the Blood Pressure ? He allowed the blood to flow into a vertical glass tube, and noted the height of the columns supported by the blood pressure. 52 What is Poiseuille’s Method ? By means of a U-shaped mercurial manometer of which the short limb is connected, by means of a leaden tube and canula, with the interior of an artery. The canula, leaden tube, and closed limb of the manometer are all filled with a saturated solution of sodium bicarbonate to retard coagulation of the blood. The blood pressure is thus communicated to the upper part of the mercurial column, and the depth to which the column sinks in the one limb, added to the height to which it rises in the other, will give the height of the mercurial column which the blood pressure balances, the weight of the soda solution being deducted. What is this Apparatus, as it stands, called ? It is called Poiseuille’s HmMaDYNAMOMETER, and it is quite enough for merely estimating the arterial pressure at any given moment, What ts the Difference between this and the Kymograph ? To make it a kymograph, it must have added to it a registering apparatus—z.e., a recording apparatus moved by oscillations of the mercury in manometer, to register pressure and pulsations on revolving cylinder; a pen to record abscissal line; and a time-marking apparatus to record seconds on cylindey. Name another Kymograph. Fick’s Spring Kymograph. Name some of the Factors on which Variations of the Systemic Arterial Pressure depend. 1. The energy and rapidity of the contractions of the heart. 2. The state of the arteries, especially of the arterioles. 3. Extraneous muscular compression, 4, Respiratory movement. 5. Total amount of blood in the body. 53 How can the Arterioles be Dilated, and the Pressure thus Lowered? There are various ways— 1. By taking a warm bath; this dilates the superficial ects and lowers the pressure. 2. By stimulating the vaso-inhibitory nerves, especially he “depressor nerve”; in this case the blood-vessels of the abdomen are dilated, and the pressure falls almost to zero, 3. Certain drugs, as by inhaling amylic nitrite. 4. By dividing the spinal cord in the neck: this cuts off the great vaso-motor centre from its control over the arteries everywhere. Name some means of constricting the Arterioles, and ratsing the Blood Pressure. 1. A cold bath: this affects the vessels of the skin chiefly. 2. Stimulating the general vaso-motor centre—e.g., a venous state of the blood. 3. Certain drugs, as digitalis, How does Extraneous Muscular Compression act ? It raises the blood pressure everywhere, by directly squeezing the arterioles, and thus forcibly keeping the blood dammed back in the aorta. What are the Risks of this Rise of Pressure ? Weak vessels may give way—e.g., the small vessels of the brain; or the left ventricle may be over-distended and paralysed. How does Respiration affect the Blood-Presswure ? It is lowered during inspiration, and increased during expiration. 54 Why is this ? During inspiration the expansion of the chest walls relieves the aorta from compression to a certain extent, and hence the fall. Further, the elasticity of the lungs causes a great recoil. Reverse these conditions, and hence the rise in pressure. What is the Objection to this Explanation ? When the chest is opened, there is still a rise and fall. How do you Explain this ? The cardio-inhibitory centre in the medulla is stimulated during inspiration, the heart slowed and hence the fall. The vaso-motor centre is stimulated during expiration, the arterioles contracted, and hence the rise. The cardio-inhibitory centre is more excitable during inspiration ; the vaso-motor centre more excitable during expiration. Does the Total Amount of Blood affect the Pressure much ? A dog may lose about a third of its blood without any resulting change in the mean arterial pressure. On the other hand, its blood may be increased as much as a third without any permanent increase of pressure. In man this could not be done because of (1) his more highly organised brain; and (2) his erect posture. Does this hold good in Dog, if the Spinal Cord in the Neck be divided first ? No; for then there is a very marked effect on the pressure, the vessels then being cut off from the regulative influence of the general vaso-motor centre, which is probably the great regulator of the blood pressure. 55 What is the Function of the Muscular Fibres of Veins ? The great function of the muscular fibres of the veins and the largest arteries, is probably to accommodate the vessels to the volume of blood in the body, so that the mean arterial pressure may be kept constant. What part does the Heart play in the Regulation of the Blood Pressure ? A rise of pressure stimulates the cardio-inhibitory centre, and the heart is slowed through the vagi; in a fall of pressure, the opposite obtains. What other Nerve has a great part to play in the Regulation of the Blood Pressure ? The “DEPRESSOR NERVE” is probably thrown into activity when the blood pressure rises. Afferent impulses pass up and inhibit the vaso-motor cells presiding over the blood-vessels of the abdomen, and the blood-vessels there are dilated, through the splanchnic nerves. This lowers the blood pressure very much. Further, the heart is reflexly inhibited, so that not only is the outflow from the arteries increased, but the inflow is also decreased. What peculiar Point has been noticed about the Stimulation of the ‘‘ Depressor Nerve” ? There is a very long “latent period.” The effect takes a long time to develop, and lasts for some time after the stimulation has been removed. What other things affect the Blood Pressure ? Variations in the filtration and absorption of lymph. If the pressure be low, lymph is absorbed from the lymphatic spaces ; if high, vice versd. Variations in the vaso-motor centre itself, If the pressure be low, the vessels contract ; if high, they dilate. 56 What is the Effect of a Tumour pressing on the Portal Vein? It may cause rupture of the capillaries of the intestine, and passage of blood per rectum. What is the Effect of Food in the Stomach ? It lowers the blood pressure in the head and elsewhere. What is the Effect of an Embolus in the Pulmonary Artery ? Rupture of the capillaries and spitting of blood. . What is the Effect of Heat or Cold on the Skin, as regards the Blood Pressure ? In heat and perspiration the blood-vessels of the skin are much dilated, and the blood pressure falls. Sudorifices act in a similar way. Sudden cold to the skin contracts the capillaries, and increases the pressure in internal organs, and may be the cause of inflammation of internal organs, as the lungs, kidneys, peritoneum, pericardium, etc. THE PULSE. What is the “ Pulse”? It is a temporary expansion of a blood-vessel, due to variation in the amount of blood sent into it at each contraction of the heart, The artery is elongated as well as laterally expanded, because it is ELASTIC. Describe the Flow of a Liquid. (1) Tarover a Rie Tus. (2) TaRroucH aN Exastic Tus wita a Large ORIrIce OF EXIT. (3) THRoven an Exastic Tuse with a Smatt Oririce OF EXIT. 57 _ 1. Through a ric tupe.—lIf fluid be driven through a rigid tube interruptedly, the flow from the tube is always interrupted, however small the aperture of exit is made—as fluids are practically incompressible, and the tube, not being elastic, it is impossible to “‘heap up” the fluid in it. _ _2. Through an elastic tube with LarcE oririce.—If the inflow is interrupted, so is the outflow—as the elasticity of the tube is not called into play, since there is no resistance to the outflow. 3. If the orifice of exit in the elastic tube be smauu, then the outflow will be continuous, even though the inflow be interrupted. In this case, there is resistance to the outflow; hence, the tube being elastic expands to accommodate itself to the supply, and the fluid is thus “heaped up” in it; and being under constant elastic pressure the outflow .is constant, as it cannot get out so fast as it gets in, What is the Effect of Dilating the Arterioles ? The pulse then passes through the capillaries into the veins, because the peripheral resistance is removed; but if the arterioles are contracted, it is confined to the arteries. The blood is thus “heaped up” on the proximal side of the resistance, and the heart keeps up this oVER-DISTENSION of the arteries. Why is the Pulse confined to the Arteries ? The pulse is usually extinguished at the capillaries, and confined to the arteries, because of— 1. The resistance to the outflow offered by the contraction of the arterioles, 2. Elasticity of the arterial walls. 3. Further, the capacity of the capillaries is much greater than that of the arteries, and therefore they are not much dilated, and the flow through them is very much slower. s 58 What are the Effects or Uses of Arterial Elasticity ? 1. Accommodation of the artery to sudden variation in the quantity of blood; it allows accommodation of blood in the arteries. 2. It permits a continuous stream through the capillaries ; the pressure in the capillaries is therefore fairly constant, and this is specially useful, as for example in the lungs. The elasticity plays much the same part as the fly-wheel does to the engine— transforms the intermittent into a continuous flow. 3. It lessens friction of the blood, so that the heart need not exert so much energy as would be required were the arteries rigid—e.g., note the hypertrophy of the heart in the case of chronic Bright’s disease of kidney, or in old age when the arteries become more rigid or calcified. 4. It prevents vibratory shock to the system at every contraction of the heart. What are the Points to be attended to in Examining the Pulse? 1. Timz.—Corresponds to the contractions of the heart; may be regular or irregular, intermittent, etc. It is always a little irregular, due to respiration. 2. Strencro.—Strong or weak, corresponding to strong or weak ventricle. 3. CompressipiLity.—As in a hard or a soft pulse. This is due to blood pressure; arterioles contracted = hard, and vice versd. It also depends to a certain extent on the. state of the arterial walls. 4. Vorume.—Large and full, small and wiry, etc. The volume affords an indication of the volume of blood in the arteries. : How did Landois study the form of the Pulse Wave ? He allowed an opened artery to jet against a revolving cylindey. 59 Name a more Exact Method. Use one of the various sphygmographs, as Chauveau and Marey’s, Dudgeon’s, or Sommerbrodt’s, What are the Parts of a Pulse Wave ? It consists of a primary wave and secondary waves. Describe the Primary Wave. It consists of an upstroke almost vertical ( “ percussion stroke”). An apex, an oblique line of descent, on which we find the various secondary waves. How ts this Wave further Divided ? Into— 1. A systolic part, from the béginning of the primary wave to the beginning of the dicrotic wave—z.e., to the “aortic notch,” which corresponds to the closure of the aortic semi- lunar valves. 2. A diastolic part, from the beginning of the dicrotic wave to the end of the primary wave. Name the Secondary Waves. 1. Predicrotic or tidal, nearer the apex, and is in the systolic part of the sphygmogram. 2. Dicrotic, at the beginning of the diastolic part of the sphygmogram. — Between the two waves is the “aortic notch.” In what kind of Pulses do we find these Waves most marked ? In sort pulses we only find the dicrotic wave. In Harp pulses the predicrotic wave is most marked. 60 What is the Cause of the Dicrotic Wave ? It is due to a rebound of the sigmoid valves when they are suddenly stretched by arterial pressure when the ventricle begins to relax. Most marked in a soft pulse, and lessens as the tension increases. It is not seen in rigid calcified arteries ; in ordinary arteries it can always be produced by lessening the blood pressure, as in diminishing the peripheral resistance, or by loss of blood (‘splash pulse”). Are other Wavelets ever seen? © Yes, frequently, following the dicrotic wave, but these are due to elastic vibrations of the arterial walls. On what does the Height of the “ Upstroke” depend ? On the power of the left ventricle, and on the extensibility of the arterial wall. , What is the Cause of the Predicrotic Wave ? It is said to be due to the inertia of the elastic wall of the vessel oscillating about its centre of equilibrium. It is most marked when the arterial pressure is high ; it is diminished or absent when the arterial pressure is low. What are the Special Uses of the Sphygmograph ? 1. It gives accurate indications of the RuauLARITY of the pulse. 2. The state of the arterial tension—exaggerated dicrotic wave = low arterial pressure ; exaggerated predicrotic wave = high arterial pressure. 3. Strength of the left ventricle, as shown by the height of the upstroke. 4, The action of drugs. 61 What is the Velocity of the Pulse Wave ? About 30 feet per second. Weber estimated it at 28) feet per second. How is it ascertained ? By means of an experiment with cardiograph, to show the beat of the heart ; and tambour sphygmograph, to show pulse in radial or other artery ; revolving drum and tuning-fork, to mark time. In this way it is shown that the pulse appears at the wrist about ;45 of a second, and in the dorsal artery of the foot about 4 of a second, after beat of heart; and the distance from heart to foot about 5 feet, and 5 x 6 = 30. What is the Length of the Pulse Wave ? The pulse appears at the foot before the dicrotic wave begins at the heart. It lasts about one second at any point in an artery, and travels at the rate of 284 feet per second. Duration x rate = what would be the real length of the wave were it not extinguished at the capillaries—7.e., were there an artery long enough to show it? On what does the Velocity of the Blood Stream depend ? 1. On the breadth of the bed. 2. On the friction of the lining membrane. The arterial and venous systems may be compared to two cones as regards their capacity. The bases of the cones are at the capillaries; the capacity of the veins is about double that of the arteries. What ts the Actual Velocity ? In the carotid artery, 10 inches per srconp. In the capillaries, 2 inches per MINUTE. 62 Why is it so Slow in the Capillaries ? Because there the “breadth of the bed” is greatest ; but the chief cause of the slowness is the increased amount of friction from the minute subdivision. How is the Velocity of the Blood Stream estimated ? In the case of the capillaries by the microscope. In the case of arteries and veins, by the RHEOMETER or “hemodromometer” of Volkmann; or the RHEOMETER or “ stromuhr” of Ludwig. What is the estimated time for a Complete Circulation of the Blood ? It is twenty-three seconds in man, How ts this ascertained in the case of the Rabbit or Dog ? It may be done by injecting ferrocyanide of potassium into one jugular vein, and then drawing blood at short intervals from the opposite jugular and testing for the presence of the salt. In the rabbit it takes 7°7 seconds, and in the dog 16°6, to come to the opposite jugular vein, What is the nearest way from the Left to the Right Side of the Heart ? The shortest possible course which any blood corpuscle can take, in order to pass from one side of the heart to the other, is to leave the aorta by one of the coronary arteries, and return to the right auricle by the coronary vein. How can a Corpuscle pass through the Greatest Number of Capillaries ? It must leave the heart by the aorta and traverse the arteries that supply the alimentary canal, spleen, and pancreas, It then 63 passes through the capillaries of these parts, then the capillaries of the liver, then through the right side of the heart and the capillaries of the lungs; from which it returns to the left side of the heart, and again to the aorta—the point from which it started. Why ts the Blood Stream more rapid in the Centre of a Vessel? Because the friction is less: at the periphery it is slower, because of the increased friction. Why do the Red Cells flow chiefly in the Centre of the Vessel ? They are heavier than the white, and, further, they have smooth surfaces. The wits are lighter than the red and are pushed to the periphery, and “roll” along near the wall of the vessel ; further, they are viscous and stick here and there to the wall. The rapidity of the stream in the centre, and its slowness at the periphery, has also something to do with it. Who Discovered the Circulation of the Blood ? William Harvey, who published his work, ‘“ Exercirario ANATOMICA DE MOTU CORDIS ET SANGUINIS,” in 1628, though he made the discovery some years before that date, in 1619; but, afraid of the scorn of his narrow-minded contemporaries, he delayed publishing his discovery till 1628. Who Discovered the Capillaries ? Malpighii, in 1661. Till then there was a gap in Harvey’s doctrine—the connection between the arteries and veins. Edinburgh : Printed by E. & S. Livinastong, 4 Melbourne Place, Jorg or CATECHISM SERIES. LS Sly Pit Yo Oe Parr LUI, BLOOD — RESPIRATION. ? EDINBURGH: Ey oo LIVIN GS TOE; Kaa ~) A basement membrane of flattened epithelial cells. (c) A layer of lymphoid tissue, and capillaries. (d) A longitudinal layer of fine elastic fibres in bundles. At the posterior part the mucous membrane is in folds corresponding to the bundles of elastic fibres in the sub-mucous coat. Show in what respects the Structure of the Larger Intra-Pul- monary Bronchi differ from that of the Trachea. 1. The connective tissue does not form a compact fibro- elastic membrane, but is in the form of a loose layer of cellular tissue, through which the large blood-vessels run. 2. The Cartizaces now form irregular plates, and are not confined to one particular place, but are all the way round, so that no DEFINITE-space is left without them. 3. The Muscunar tissuz forms a complete ring inside the cartilaginous plates. 4, The lymphoid tissue is not in the form of a condensed layer, but in masses between the muscular coat and the cartilages forming the ‘lymph follicular cords.” 5. In regard to the mucous coat, the yellow elastic tissue is very distinct (in bundles) and throws the mucous membrane into ridges which project into the lumen all the way round, giving it a crenated appearance. In the trachea the ridges are at the posterior part. 23 Describe the Structure of the Minute Bronchi, or Bronchioles. Cartilages, mucous glands, and ciliated epithelium are absent. They simply consist of— 1. A fibrous sheath. 2, A well marked layer of elastic tissue. 3. An equally well marked layer of non-striped muscular fibres. 4, A single layer of cubical epithelium on a basement membrane. How do the Muscular Fibres end ? They are continued into the alveolar passages and in- fundibula, but do not surround the air cells. How are the Elastic Fibres Arranged ? They are continued on to the air cells, and help to form their walls, What are the “ Lobes” of the Lungs ? They are the primary divisions, the right having THREE, the left Two. What are the Coverings of the Lungs ? 1. A sERous covering, the pleura pulmonalis. 2, Sub-serous areolar tissue, with many elastic fibres: this layer is continuous with that within the lung. 24 How is a “ Lobe” of the Lung Formed ? Each lobe is made up of LoBULES of various sizes, usually about the size of peas; each lobule is pear-shaped, with the broad end to the outside. The lobules are best seen on the cut surface of afcetal lung. Between the lobules we find fine connective tissue with many elastic fibres. Each lobule may be regarded as a miniature lung, each one having a terminal bronchiole, and a branch of the pulmonary artery and vein. What ts meant by a “ Terminal Bronchiole” ? After repeated subdivisions, the bronchial tube when reduced to 1 mm., is called a terminal, or lobular, or respira- tory bronchiole. What becomes of this Terminal Bronchiole ? It branches into several wider tubes called aLvEoLaR DUCTS or INFUNDIBULA, and each of these again branch into several smaller ducts. All the infundibula are closely beset in their whole extent with polygonal vesicles—the air CELLS or ALVEOLI opening by a wide aperture into the infundibular passages but not communicating with each other. All the infundibula with their air cells, belonging to one terminal bronchiole, forms a LoBuLE of the lung. The infundibula are lined with cubical non-ciliated cells, with here and there some squamous epithelial plates. Give the Structures forming the Wall of an Alveolus. 1. It consists of a delicate fibro-clastic tissue with coiled elastic fibres continuous with the outer coat of the terminal bronchiole. 25 2. This is lined by a single layer of squamous epithelial cells, in the form of clear plates, with here and there masses of nucleated small polyhedral granular cells, probably young cells. The muscular coat of the bronchiole is not continued on to the air vesicles. 3. Surrounding each vesicle there is a dense network of capillary blood-vessels from the pulmonary artery and vein. There are also, in the alveolar wall, rootlets of lymphatic vessels, What are the Blood-Vessels of the Lung ? 1. The pulmonary artery and vein. 2. The bronchial artery and vein. Describe the Course and Distribution of the Pulmonary Blood-Vessels ? The pulmonary vessels run in the connective tissue that separates the lobes and lobules, towards the infundibula and air cells. Tach of these latter is surrounded by a sort of basket-shaped dense network of capillary blood-vessels. Some of the capillaries pass through the alveolar wall and he immediately beneath the epithelium lining the alveolus. The arteries of different lobules are independent. Give the Course and Distribution of the Bronchial Vessels. The bronchial vessels pass along with the bronchi, and chiefly serve for the nourishment of these tubes. There are usually three to each lung, and they arise from the aorta or intercostals. They may end in capillary networks either— 1. In the bronchial glands or coats of the large blood- vessels. 2. In the interlobular areolar tissue. 3. On the surface of the lung beneath the pleura. 26 How are these distinguished from Pulmonary Capillaries ? 1. They are very tortuous. 2. They form a very open network. In the pulmonary capillaries, the reverse obtains. Part of the bronchial blood supply is returned by the PULMONARY vein. How do the Pulmonary Vessels differ from the Systemic ? 1. The arteries contain dark blood, the verns red blood. 2, The veins are not more capacious than the arteries. 3. The veins have no valves. 4, The arteries of different lobules are independent, but the veins freely anastomose. How are the Lymphatics Arranged ? In two sets— 1, A sub-pleural set, communicating with the pleural cavity through the stomata. 2. A deep set-— (a) In the walls of the air cells, often peri-vascular. (2) In the walls of the bronchi, often peri-bronchial. Describe them more minutely. The lacune and canaliculi in the walls of the alveoli are the rootlets of lymphatic vessels; they accompany the pulmonary vessels and form a network around them: these are the deep or PERI-VASCULAR LYMPHATICS, They are also connected with the lymphatics surrounding the bronchi, the 27 PERI-BRONCHIAL LyMpHatics. The lymphatics of the super- ficial air cells empty themselves into the sUB-PLEURAL PLEXUS OF LYMPHATICS, a rich plexus of large lymphatics with valves. Finally, all these lymphatics lead by large trunks into the bronchial lymph glands, and thence to the thoracic duct. What are the “‘ Stomata” ? They are minute openings between the epithelial cells lining the alveoli, and lead from the cavity of the air cell into the lymph lacune of the alveolar wall. They are more distinct during expansion—7.¢., during inspiration. Through these stomata formed particles, such as soot, pigment artifici- ally injected, etc., may be carried into the alveoli from the bronchi by natural inspiration; and thus find their way into the radicles of lymphatics, thence to the peri-vascular and sub-pleural lymphatics, and finally into the bronchial glands. Give an Example of this. In “coal miners’ lung” we simply have an injection of the lymphatics of the lung with particles of carbon, taken up in this way. In a similar manner it is possible to inject the lymphatics of a living animal with coloured pigments. How does the movements of the Lung affect the Lymph movement ? Inspiration, by its expanding the lungs, and consequently also the lymphatics, greatly favours absorption and increases the movements of the lymph. It is the same also with the 28 movements of the diaphragm (the chief muscle of inspira- tion), and by placing a coloured fluid in the concavity of the diaphragm and keeping up artificial respiration, the fluid will be taken up by the lymphatics. But the respiratory movements also affect the lymph movement in another way: when the chest enlarges during inspiration, it exercises an “aspirating” effect, and is said to suck the blood in the large veins towards the heart ; the rapid motion of the blood in the subclavian (left) vein, past the orifice of the thoracic duct, will tend to make the contents of the duct discharge into the vein more rapidly ; and besides, the duct itself is subject directly to the same aspirating force. This is the vis-a-fronte of the lymph circulation. How are the Lungs supplied with Nerves ? From the vagi and sympathetics, which form the anterior and posterior pulmonary plexuses, and from these branches enter at the root of the lung and follow the course of the air tubes and probably end in the alveoli. There are many ganglia on these branches (of the sympathetic at any rate) of doubtful function. What are the Functions of these Nerves ? The SYMPATHETIC is vasomotor. The Vagus is motor to the bronchial muscles, and sensory to the bronchi and air vesicles. Why is there so much Elastic Tissue in the Lung ? Because it is of great use in assisting respiration. 29 What is the function of the Bronchial Muscles ? The function is very doubtful; they may help to expel mucus, though this is probably accomplished by the cilia. Give a short general account of the mechanism of Respiration. The lungs are compound elastic bags communicating with the outside air, and suspended in a semi-distended state, in an air-tight cavity with movable walls. When the chest cavity is enlarged by the action of certain muscles, the pressure within becomes less than that without, and there- fore the air rushes in to restore equilibrium, as it is impossible to create a vacuum. When the muscles relax, the lungs tend to collapse, and expel the contained air, by the action of the elastic tissue of the lungs and various other agencies. The cavity of the chest is thus lessened, the pressure within becomes greater than that of the atmosphere without, and therefore air is forced out. How is the Chest enlarged in Inspiration ? It is enlarged in three diameters by the descent of the diaphragm, and the elevation of the ribs— 1. In an ANrTsRO-PosTERIOR direction. The centre of motion is the spine: the ribs are placed obliquely; hence, if raised, the distance between them and the spine is increased, just as when one raises the handle of a bucket. The inter- costal spaces are also widened. 2. In the Transverse diameter, as the ribs rise they rotate round an axis uniting their vertebral and sternal ends; their external surfaces, which looked downwards and 30 outwards, now look directly outwards. In ordinary respira- tions the upper end of the sternum and the first rib do not move; in forced respiration, the sternum does move. In laboured respiration all parts of the chest move, the sternum is thrown forwards and upwards, and the ribs raised. 3. The third increase in size is in the VERTICAL diameter. This is affected by the contraction of the diaphragm. At rest the diaphragm presents a convex surface to the thorax ; in contracting, this surface becomes flatter, the floor of the chest is lowered, the cavity of the thorax enlarged, and the air enters to distend the lungs. What effect has this on the Abdomen ? The contraction of the diaphragm tends to press the abdominal viscera downwards, and causes the walls of the abdomen to project during inspiration. What do you understand by the “ Types of Respiration ?” In young children respiration is chiefly carried on by the diaphragm, and as this descends, it presses upon the contents of the abdomen, and pushes out the anterior abdominal wall very markedly. This movement of the abdominal wall being more manifest than that of any other part, this form is spoken of as the Aspominat type of respiration. In Msn, in addition to the above, the lower part especially of the chest is subject to a wide movement in inspiration ; this is spoken of as the INFERIOR cosTan type of respiration. In Women, on the other hand, the movement is less extensive in the lower part of the chest and abdominal wall, and more marked in the upper part of the chest, and this 31 is spoken of as the suPERIOR cosTaL type of respiration. Hence, speaking in a general way, the aBDominaL (dia- phragmatic ) type is more marked in matms, and the COSTAL type in FEMALES. What are the Muscles of ordinary Inspiration ? 1. Diarperacmu, the most important. It descends, be- comes flatter, by contraction of its fibres, and thus the vertical diameter is increased. The first two ribs are firmly fixed by the scaleni, then the sternum is thrown upwards and forwards the ribs raised and rotated by— 2. The Exrernat Intercostats: their fibres pass down- wards and forwards. 3. Levatores Costarum.—These small powerful muscles ARISE from the transverse processes, and are INSERTED into the ribs below ; being so near to the fulcrum, they elevate the sternal end very much. 4, Internat Intercostats.—The action of these muscles is somewhat doubtful, but they probably raise the ribs also ; the direction of their fibres is downwards and backwards. The results of experiment are purely negative. The part in front between the cortal cartilage at any rate are inspiratory —i.e., they raise the ribs. What are the means by which ordinary Expiration is brought about ? 1, The Exasticrry or Taz Lunes.—During inspiration the elastic tissue of the lungs is put upon the stretch, but when the muscles of inspiration relax, there is an elastic recoil, and part of the air is forced out. This elasticity cannot cause 32 the lungs to collapse, because it cannot create a vacuum in the pleural cavity. 2. The wetcut of the chest wall—z.e., gravity. 3. The sxasticiry of the costal cartilages; by being elevated they are slightly twisted, but when the muscles relax, they tend to untwist themselves. 4, The siasticiry of the abdominal wall: when the diaphragm descends, it presses down the abdominal viscera, and puts the abdominal wall on the stretch. When the muscles of inspiration relax, it tends to recoil, and press the abdominal viscera up against the diaphragm again. What is the great difference between the mechanism of ordinary Inspiration, and ordinary Expiration ? Ordinary Inspiration is a purely muscuLar action. Ordinary Expiration is a purely pHysica action. What is the possible Exception to this last statement ? It is the doubtful exception that perhaps that part of the internal intercostals between the Bony parts of the ribs may act as expiratory muscles. Describe the Respiratory movements of the Glottis. At every inspiration the glottis is opened by the Crico- ARYTENOIDEUS Posticus muscle. During expiration it is restored to its state of rest by an elastic ligament—the Crico-aryTENno1n, 33 Are the Nostrils specially concerned in Respiration ? The nostrils are expanded during inspiration by the dilator muscles. During expiration they return to their condition by the elasticity of the nasal cartilages. In some persons the movements of the nostrils during respiration are much more evident than in others. What are the Muscles of Forced Inspiration ? Every muscle that can, either directly or indirectly, raise the ribs is brought into play. Classify and name these Muscles. 1. Those that raise the hyoid bone (indirect elevators of the ribs)— (a) Genio-hyoid. (6) Mylo-hyoid. (c) Stylo-hyoid. (d) Digastric. 2. Those that raise the sternum directly— (a) Sterno-hyoid. (6) Sterno-thyroid. (c) Thyro-hyoid. (d) Sterno-cleido-mastoid. 3. Those that raise the upper ribs— (a) Scaleni. (b) Cervicalis ascendens. (c) Serratus posticus superior. 34 4, Those that pull the scapula upwards and backwards, and fix them— (a) Trapezius. (2) Levator anguli scapula. (c) Rhomboideus major. (da) Rhomboideus minor. 5. Those that pull up the ribs by taking a fixed point from the elevated shoulder bones— (a) Serratus magnus. (b) Pectoralis major. (c) Pectoralis minor. (d) Subclavius. What are the Muscles of Forced Expiration ? To be useful for expiration they must either— (a) Press up the contents of the abdomen against the diaphragm, or (6) Pull down the ribs. Name the Muscles of the First Group. (a) Obliquus externus. (b) Obliquus internus. (c) Transversalis abdominis. (d) Levator ani. What Muscles Depress the Ribs ? (a) Rectus abdominis. (6) Longissimus dorsi. (c) Quadratus lumborum. (d) Serratus posticus inferior. (e) Triangularis sterni. 35 Whether are the Muscles of Forced Inspiration or Forced Expiration the more powerful ? The muscles of forced expiration are the more powerful ; about one-third more. Why do the Lungs Collapse when the Chest is Opened ? It is due to the recoil of the stretched elastic tissue of the lung. It is not due to the atmospheric pressure. What is Meant by the “ Rhythm” of Respiration ? Each respiratory act consists of three periods— | Biter: oe 1. Inspiration. fe 7 =A ; 4 2. Expiration. 1€ ~ Cate 3. The so-called pause. \e& pes # Inspiration begins suddenly and advances rapidly to completion ; Expiration begins immediately after, and at first advances rapidly, and then very slowly. This slow part is the “Pause” of some physiologists: it is not a real pause, only a very slow expiration. Give the Relative Length of these Three Parts. If the whole act be represented by 10, then— Inspiration = 3 \ Expiration = 4 “Pause” = 3_ | 10 It will be seen, therefore, that inspiration is shorter than expiration. 36 What are the Respiratory Sounds ? In health, practically two— 1. Bronchial. 2. Vesicular. They are due to the friction of air in the respiratory passages, chiefly at two points—the glottis (producing the BRONCHIAL murmur), and at the point where the bronchioles join the alveoli (the vesicvLaR murmur). Describe the Bronchial Murmur. This is best heard over the trachea or between the scapulee, or over the upper part of the sternum. It is a soft, BLowiNG, to-and-fro sound, consisting of inspiratory and expiratory parts, with a distinct pause between; the expiratory part is as long, or longer, than the inspiratory. Its pitch depends on the size of the tube we listen over. Describe the Vesicular Murmur. It is due to the entrance and escape of air into and out of the air vesicles. It is a gentle “breezy” sound, which resembles the sighing of wind among leaves on a calm summer evening. It consists of two murmurs, the one corresponding to inspiration, and the other to expiration, and without any pause between the two parts. It is of very short duration, and in healthy persons the ExPrRaTORY part is often not heard at all. Give the Relative Length of the Two Parts. The inspiratory part is about THREE times as long as the expiratory, and is softer and higher in pitch. 37 N.B.—The longer inspiratory part of the vESIcULAR MuRMUR, though in the RESPIRATORY RHYTHM expiration is much longer than inspiration. When the expiratory part of the vesicular murmur becomes prolonged it often means IMPENDING PaTHISIS. What is the Relation of the Heart-beats to Respiration ? One respiration to every 4°5 beats of the pulse. NERVE MECHANISM OF RESPIRATION. Where is the Centre ? In the medulla: its position is ascertained by experiment. Respiration goes on in the absence of consciousness, and after the removal of the brain above the medulla; but destroy the medulla and it stops. The centre is bilateral— a bilateral inspiratory, and a bilateral expiratory — the similar centres are co-ordinated and act as one. The centre extends from near the root of the vagus to the “calamus scriptorius.” Give the Motor Nerves of Ordinary Inspiration. 1. Phrenic nerves to the diaphragm. 2. Intercostal nerves to the intercostal muscles and levatores costarum. 3. Inferior laryngeal nerves to the crico-arytenoid muscles, that open the glottis. 38 Give the Motor Nerves of the Auxiliary Muscles of Inspira- tion ? 1. Cervical and upper dorsal nerves to the various muscles of the neck and upper part of the chest. 2. The spinal accessory nerve to the sterno-mastoid and trapezius. 3. The ninth nerve to the genio-hyoid, sterno-hyoid, thyro-hyoid, and sterno-thyroid muscles. 4, The fifth nerve to the mylo-hyoid and anterior belly - of digastric. 5. The seventh nerve to the stylo-hyoid and posterior belly of the digastric. What are the Motor Nerves of Forced Expiration ? The lumbar and sacral nerves supplying the muscles of the abdomen, and those of the lower part of the back. What is the Result of dividing the Spinal Cord just below the Origin of the Phrenics ? Division of the spinal cord just below the origin of the phrenics (¢.e., the fifth cervical nerve) results in paralysis of all the muscles of expiration (forced) and some of the muscles of mspiration. What takes place when the Phrenics are Divided ? Divide one phrenic, and the diaphragm on that side is paralysed. Divide soru, the diaphragm is completely paralysed. Still death does not result at once because the muscles that raise the upper ribs are sufficient for a time to carry on respiration, but it becomes excessively laboured. 39 What is the Result of Division of the Spinal Cord above the Origin of the Phrentes ? Death ; because all the respiratory muscles are paralysed. The centre, however, is still active, because the respiratory movements of the glottis and nose still go on; but when the facial and recurrent laryngeal nerves are cut, these stop also. Is Respiration Voluntary or Involuntary ? The respiratory movements are usually involuntary, though many voluntary muscles are concerned in them. It goes on in the absence of consciousness, and after all the brain is removed above the medulla oblongata. What ts the Exciting Cause ? The exciting cause is referable to the state of the blood, especially to deficiency of oxygen, probably more than to any accumulation of carbonic acid. What is the Result of too much Oxygen in the Blood ? When the blood is hyper-oxygenated, the exciting cause of the respiratory movements is removed, and the animal therefore ceases to breathe, because there is no need for it. What is this Condition called ? Apnea. What takes place if an Animal be kept in a Confined Atmosphere ? In a confined atmosphere we soon get exaggeration of breathing, and it becomes deep and anxious — HyPerpna@a. 40 This soon becomes worse, and respirations become deep and hurried, giving us a condition of Dyspyaa, and this soon ends in AspHyxta. All this is due to the DEFICIENCY OF AVAILABLE Oxyaen, rather than to the accumulation of carbonic acid. Give some Proofs of this fact ? l. If an animal breathes pure nitrogen, carbonic acid does not accumulate in the blood; yet very soon there are mani- fested all the phenomena of hyperpncea and dyspnea, due to the deficiency of oxygen. 2. If an animal breathes a mixture of carbonic acid and oxygen, with the carbonic acid in it so abundant that carbonic acid does not diffuse from the blood, and with the oxygen sufficiently abundant to fully oxygenate the blood, there are no signs of excitement of the respiratory centre. There is an accumulation of carbonic acid in the blood, and yet we have none of the signs of asphyxia. At first the breathing is deeper and a little more frequent, but this passes off, and the animal presents the appearance of narcotic poisoning, sleepiness, drowsiness, stupor, etc. Does deficiency of Oxygen affect the Respiratory Centre directly or indirectly ? Chiefly directly; but it may also do it indirectly, through the pulmonary branches of the vagi. What are some of the Theories to account for the Periodic Activity of the Inspiratory Centre ? 1. That it may be due to an automatic discharge of energy from the nerve cells. : 41 2. That they are stimulated by some chemical condition of the lymph which pervades them. An oxidisable substance may be always produced either in the blood or in the respiratory centre that gives rise to the movements of respiration. This is as continually destroyed by the oxygen— if the respirations be slow then this matter increases, but if they be quick it does not. How is the Centre affected indirectly ? Through the pulmonary branches of the vagi. The vagi are stimulated, either by the condition of the blood in the capillaries, or the altered air in the air vesicles acting on the nerve endings, and impulses are then sent up to the centre in the medulla. Give some Proofs of the truth of this statement. Divide one vagus, and the respiration is slowed: the impulses passing up must therefore excite the inspiratory centre. Cut both vagi, there is great anxiety of breathing and a whistling sound, because the recurrent laryngeal is cut and therefore the posterior crico-arytenoid muscles are also paralysed. The animal is not suffocated, however, because, though the respiration is SLOWED, it is also DEEPENED, so that what is lost in rate is gained in extent. From these experiments it is assumed that— 1. During life afferent impulses are continually ascending the vagi, and modifying the movements of the respiratory centre. 2, That these impulses bear simply on the distribution in time of these movements, and not on their amount. 42 What is the Effect of Heat on the Inspiratory Centre? When the temperature of the blood is above normal, the centre is excited and hyperpnea and dyspnoea, are produced —e.g., overheat the blood in the carotid artery. In fevers also the same thing is seen, the rapid respirations being due to the high temperature, the heated blood acting directly in the centre. Wheat is the Liffect of cutting off the Blood Supply ? If we cut off the blood supply from the medulla (by tying the vertebrals and internal carotids) there is an increase of carbonic acid and a decrease of the available oxygen in that region, and the result is dyspnea. This shows that the oxygen affects the centre DIRECTLY. How is the Respiration affected by the Will ? The will can either excite or inhibit inspiration or expiration, even though the impulse has begun in the centre; it can even affect FORCED expiration—e.g., coughing. What is the Effect of Stimulation of the Vagus on the Centre ? The inspiratory centre is aLWays being stimulated through the vagi. Divide and stimulate the uppErR end— 1, Gently—Respiration is accelerated. 2. Powerfully—Respiration is stopped, with the dia- phragm brought to rest in a sTaTE or spasm as if it were a CONSTANT inspiratory effort, as indeed it is. 43 What Sets of Nerves are contained in the Pulmonary Branches of the Vagus ? The pulmonary branches of the vagus contain Two sets of fibres— 1. The Inspiratory, that go to the centre for inspiration: these are always in action, exciting that centre. 2. The Exprratory, that go to the centre for expiration : this set is brought into use when there is, for example, an accumulation of mucus in the bronchi, and the result is a coueH, to expel it. What are the Ejfects of Stimulation of the Superior Laryngeal Branch of the Vagus ? This is the sensory nerve of the larynx. Cut both, there is no change in the respiratory movement; and there- fore they are not usually in a state of activity, as far as respiration is concerned. Stimulate the upper end of the divided nerve, we note four effects— 1. Pain, as the nerve is a sensory one. 2. The animal swallows. 3. There is an inhibition of inspiration. 4, There is an excitation of expiration, and the diaphragm is brought to rest in a state of relaxation. Give a familiar Example of this. When a crumb of bread goes below the glottis—goes the “wrong way ”’—we note— 1. Inspiration is inhibited, so that the crumb is not drawn down. 2. Expiration is excited, a cough results, and so it is driven out. 44 What is the Effect of Experiments on the Cut Vagus above the level of the Superior Laryngeal ? When the upper end is stimulated, the result is the same as in stimulating the upper end of the divided superior laryngeal: its fibres, being the most powerful, mask the effects of stimulation of the pulmonary branches. What is the Effect of Stimulation of the Cutaneous Nerves? The inspiratory centre is stimulated—e.g., a dash of cold water on the face, or a cold bath. The effect is most powerful when the fifth nerve (face) is stimulated. What is Coughing ? It is a peculiar expiratory movement. There is a deep inspiration, followed by closure of the glottis; then a sudden forcible expiration, which bursts open the glottis, and the blast of air is driven through the mourTH. What is the nature of this act ? It is a REFLEX act. Give the Mechanism usually involved. 1. For the sensory surFace affected, see next question. 2. The afferent nerve is nearly always the vagus, 3. The centre involved is the expiratory centre. 4. The efferent nerves are those that supply the muscles of extraordinary expiration. 5. The muscles are those of extraordinary expiration. 45 At what Sensory Surfaces may the Irritation arise ? 1. The respiratory mucous membrane—eg., a pellet of mucus. 2. The alimentary mucous membrane—e.g., in dyspepsia, where the gastric filaments of the vagi are stimulated. 3. Irritation at the back part of the tongue. In this case the afferent nerve is a twig of the superior laryngeal (from vagus) distributed to the dorsum of the tongue at the sides and immediately in front of the epiglottis. 4, External anditory meatus: the nerve affected being the auricular branch of the vagus. 5. Cold acting on the skin of the throat or chest, or any exposed part of the body. Coughing may be inhibited voluntarily unless the stimulus be very powerful. What is Sneezing ? It is also a peculiar expiratory movement, almost the “same as coughing, except that the expiratory blast is driven through the Noss, the soft palate and anterior pillars of the fauces shutting off the mouth from the pharynx. Is tt a Reflex Act ? Yes. Give the Nerve Mechanism ? 1. The sensory surfaces are usually either the mucous membrane of the nose or the retina. 2. The afferent nerves: from the nose, the nasal branch of the fifth; this is the nerve usually affected in sneezing from the retina, the optic nerve. The other parts of the mechanism are the same as in coughing. 46 Give Examples of Irritation causing Sneezing ? A pellet of mucus in the nose, or from tickling the nose ; or other forms of irritation as snuff, etc. A bright light acting on the retina. Give a point of difference between Sneezing and Coughing ? Sneezing cannot be inhibited voluntarily, whereas cough- ing may. It is said that sneezing may be stopped, unless it has gone too far, by pressure on the side of the bridge of the nose ; by doing so a small twig of the nasal nerve is squeezed, and this seems to retard or check the transmission of impulses to the expiratory centre—z.e., afferent impulses. What is Hiccup ? It is a spasmodic contraction of the diaphragm, in the course of which the glottis closes suddenly, and further entrance of air into the chest is stopped; and the column just entering strikes against the closed glottis and gives rise to the sound. What Nerves are Concerned ? The afferent nerves are the gastric branches of the vagus: the glottis is closed by the inferior laryngeal; the phrenics to the diaphragm are of course involved as well. Hiccup may result from blood-poisoning. What means are used to arrest ordinary Hiccup ? | 1. A deep inspiration, kept in as long as possible to steady the diaphragm. 2. Swallowing pieces of ice, and allowing them to melt in the stomach. 47 What is the Rapidity of Respiration ? Usually from 15 to 20 times per minute in the adult., in the child, about 40 per minute. In diseased states it may range from 7 to 100 per minute. It is naturally slower in sleep. Express shortly the Law of Absorption of Gases by Liquids. When a liquid—e.g., water, is exposed to any gas, or mixture of gases, the gases will either escape from the liquid, or be absorbed by it, until equilibrium is established between the pressure of gases in the atmosphere above, and the tension of gases in the water below. This is the case with every individual gas, no matter how many may be present in the mixture ; the absorption or escape of any one is independent of the presence of others. The absorption of any gas, therefore, by a liquid, depends on the PaRTiaL PRESSURE of that gas in the atmosphere to which the liquid is exposed. The pressure is called “partial,” because the pressure of any one gas only forms a part of the general pressure. : What is the ‘‘ Partial Pressure” of Oxygen in the Atmo- sphere ? As oxygen forms one-fifth of the atmosphere, of which the total pressure is 30 inches of mercury, therefore the partial pressure of oxygen is one-fifth of 30 = 6 inches. What are the Gases of the Blood? Oxygen, carbonic acid, and nitrogen. 48 How are they extracted ? By means of the mercurial gas pump of Pritcrr. Give the Percentage of the Blood Gases. 100 volumes of blood contain 50 or 60 volumes of gas— Oxygen in arterial blood = 16 per cent. Oxygen in venous blood = 6 to 10 per cent. Carbonic acid in venous blood = 35 per cent. Carbonic acid in arterial blood = 30 per cent. Nitrogen, whether in arterial or venous blood = 1 to 2 per cent. How would you Analyse the Blood-Gas ? 1. First, shake up the gas in the test-tube with caustic potash ; this absorbs all the caRBONIC ACID. 2. Then add pyrogallic acid, and this absorbs all the OXYGEN. 3. The remainder represents the volume of NITROGEN. How is the Oxygen held in the Blood ? Almost the whole of the oxygen of the blood is in LoosE CHEMICAL COMBINATION with the hemoglobin in the cor- puscles ; only a very small proportion is simply dissolved. All the respiratory oxygen is removed by a vacuum. What are the Reasons for believing this ? The amount absorbed by the ssrum can be accounted for by pressure, just as water will absorb oxygen—a purely 49 physical phenomenon. In the corruscius, however, it does not follow the general law of absorption according to pres- sure. The amount they contain cannot be accounted for in this way. It can only be accounted for on the ground that the oxygen is in a state of loose chemical combination with the hemoglobin of the corpuscles. What further Reasons can you give ? If water in which oxygen is simply dissolved be subjected to diminished pressure in a mercurial air-pump, the gas begins to be given off immediately the pressure is reduced, and the amount given off is proportioned to the pressure ; in other words, it follows ‘“Dalton’s Law.” But if arterial blood be submitted in like manner to diminished pressure, no oxygen will be given off till the pressure sinks to one- sixth of an atmosphere (5 inches). The gas is then rapidly given off, and the blood becomes dark. In this case it does not follow “ Dalton’s Law.” How is the Carbonic Acid Stored in the Blood ? It is nearly all contained in the serum. The serum yields almost as much carbonic acid as the serum Pius corpuscles. It is partly absorbed by the water of the serum, but chiefly in chemical combination—part is FIRMLY com- bined as sodic carbonate, and more loosely combined with this to form the bicarbonate; a small part also is united with sodium phosphate. The sodium compounds are the chief carriers of carbonic acid from the tissues to the lungs. Volume for volume, serum yields as much carbonic acid as blood. D 50 How is the Nitrogen retained in the Blood? It is simply dissolved in the water of the blood. Compare Inspired and Expired Air. Nitrogen. Oxygen. Carbonic Acid, Inspired air contains 79:15 20°81 0:04 Expired air contains 79°587 16-03 4:38 Difference = 0°437 4°78 4:34 Give a Short account of the Gaseous Interchanges in Respiration. 1. BetwEEN THE BLooD AND THE TissuES— (1) The tissues rob the lymph of oxygen, and there- fore its tension in the lymph is lowered, and hence oxygen is disassociated from the oxyhemoglobin of the blood and carried out into the tissues: because oxyhemoglobin is not a very stable compound, and requires a certain tension of oxygen to keep it in com- bination. The oxygen in arterial blood has a high tension; the tension of oxygen in the tissues is kept low, because the tissues are constantly using it up, and hence the oxygen passes into the tissues and they stow it away. (2) The carbonic acid produced in the tissues from metabolic changes passes into the blood- capillaries. The tension within them is less than that in the tissues, because it is being constantly produced in the tissues, 51 2. BETWEEN THE Buoop anp THE AIR. (1) In the air vesicles of the lungs the tension of oxygen is greater than in the blood returned from the tissues, and therefore it passes into the capillaries from the air vesicles. (2) On the other hand, the tension of carbonic acid is greater in the venous blood returned to the lungs than in the air vesicles, and therefore it passes from the blood into the air vesicles. How the sodium bicarbonate thus gives up its carbonic acid in the lungs is not exactly known, as it is a comparatively stable body. It will be seen, therefore— 1. That the venous blood passes to the lungs with a low tension of oxygen and a high tension of carbonic acid. In the lungs the conditions are the reverse, for there the oxygen tension is high and the carbonic acid tension low. 2. That the arterial blood passes to the tissues with a high oxygen tension, and a low carbonic acid tension, In the tissues the conditions are the reverse, for there the oxygen tension is low and the carbonic acid tension high. Hence the exchanges. In the tissues the oxyhemoglobin is partially reduced; it then returns to the lungs and is there once more oxidised. What is meant by “ Tidal Air” ? It is the air which is constantly passing in and out of the chest during ordinary calm breathing. What ts its amount ? About 20 cubic inches. 52 What is the “‘ Complemental Air” ? It is the air that can be drawn into the chest, over and above the tidal air, by a forced inspiration. What ts its amount ? 120 cubic inches. What is the “ Reserve” or “ Supplemental Air” 2 It is the air that can be expelled by a forcible expiration, over and above the tidal air. What ts its amount ? 90 cubic inches. What is the ‘‘ Residual Air” ? It is the air that still remains in the lungs even after the most forcible expiration. What ts its amount ? 90 cubic inches. What is the “ Vital” or “ Respiratory capacity” ? It is the amount of air that can be driven out of the chest by the most forcible expiration, after the most forcible inspiration. 53 What is this amount ? 230 cubic inches. Whut does it include ? It includes— The Tidal air = 20 cubic inches. The Complemental air = 120 " The Reserve air = 90 un " Total, 230 Does that mean fur everybody ? No; it is for an individual of average height—5 feet 8 inches. How does the Height affect it? It varies about 8 cubic inches more or less for every inch over or under that height—7.e., in a man 5 feet 7 inches it will be 8 cubic inches less; in one 5 feet 9 inches, 8 cubic inches more; and so on. What other conditions affect it ? 1. The mobility of the chest walls. 2. The strength of the muscles of the chest. What Instrument is made use of in these Investigations ? The ‘“ Spirometer.” 54 Is the Air in the Vesicles changed directly at each Respira- tory Movement. No; the tidal air does not pass down pirectLy to the air vesicles at every ordinary respiratory act. It is intro- duced simply into the upper part of the pulmonary passages ; the gaseous interchange after this is by diffusion and is subject to the laws of diffusion of gases in general. State the Changes in the Air by Respiration. 1. It loses oxygen—4°77 per cent. 2. Gains carbonic acid—4°34 per cent. 3. It gains heat: if the temperature of the air be 20°C. then the expired air in the mouth will be about 33-9 C., and in the nose about 35:3°C.—7.e,, it gains about 14°C. 4, It gains moisture—9 ounces in twenty-four hours. 5, It gains various organic impurities—putrescible organic matters. How would you Detect the Organic Impurities ? Drive expired air through water, the water very soon gets a bad smell, and begins to putrify : or pass the expired air through a solution of permanganate of potassium, it is soon reduced and becomes less red. What is the amount of Carbonic Acid in ordinary Air? ‘O04 per cent.: if it rises to ‘08 it is unwholesome, not so much because of the carbonic acid, but because of the accompanying organic impurities. These are more or less unknown, and the amount of carbonic acid present is taken as their measure. 55 Is there anything peculiar about the loss of Oxygen and the gain of Carbonic Acid ? The air loses a little more oxygen than it gains of carbonic acid: all the oxygen does not pass to combine with carbon ; about 1 per cent. is “lost,” or stowed away in the tissues. What does this explain ? Why, when an animal breathes in a confined space, the atmosphere is absolutely diminished. Give the amount of Oxygen inhaled and Carbonic Acid exhaled ? 1346 cubic inches of carbonic acid are exhaled per hour, or about 636 grains. 1584 cubic inches of oxygen are inhaled per hour, or about 542 grains. Express this in another form. Amount of oxygen absorbed in twenty-four hours= 26 ounces. Amount of carBon excreted in twenty-four hours= 8 ounces. Give some of the Conditions affecting the excretion of Car- bonic Acid. 1. MuscuLar work: more oxygen absorbed, and car- bonic acid excreted during muscular work. 56 2. Foop: more oxygen is absorbed and carbonic acid excreted when food is taken. 3. Nature or Foop: most carbonic acid excreted on a flesh diet. In the dog, the reverse obtains. Alcohol, tea, brandy, and gin lessen the amount excreted. 4, Damy variation: less during the night. At night more oxygen absorbed than carbonic acid excreted. Least at midnight ; most at mid-day. 5. SEASON: maximum in April and May, least in Sep- tember. 6. AGE: increases till thirty years, is then stationary to forty, and after this diminishes till seventy years of age. 7. Sex: more by male than female. In the female the increase stops at puberty, and remains stationary during menstrual life (from fifteen to forty-five years), and after the change of life it diminishes. 8. LienT: more excreted in light: dark, gloomy rooms are unhealthy. 9. MoistuRE: increases the excretion. 10. Disease: increased excretion in chronie and organic disease of the lungs. Cholera, measles, small-pox. Lessened in chlorosis, and in typhus fever. In typhus it is lessened about one-half, and in small-pox it is almost doubled. What is the Source of the Heat added to the Atr ? Chiefly from blood-vessels of the respiratory passages : very little from the capillaries of the lungs or the pulmonary artery. 57 Why should one Breathe through the Nose? Because in it is a special heating apparatus—the very vascular inferior turbinated bone. When one _ breathes through the mouth, the air going to the lungs is two degrees colder than when it enters through the nose. What are some of the Effects of Breathing Air vitiated by Respiration ? ” Headache, muscular pains, drowsiness, and general im- pairment of health. What are these Effects due to? Due to the carbonic acid partly, but chiefly to the accompanying organic impurities. Amount of carbonic acid in ordinary air="04 per cent. When it reaches ‘06 per cent. there is a bad smell, due to putrescible organic matters. At ‘1 per cent. the effects are very bad, though it can be breathed for some time. What Breathing Space should be allowed ? 750 to 1000 cubic feet, and to keep this pure the air must be changed three or four times every hour—four times in the 750 cubic feet room, and three times in the 1000 feet space. What are the Causes of Asphyxia or Suffocation ? Anything that prevents the oxygen of the air reaching the blood, or the blood reaching the oxygen, such as— E 58 1. Breathing vitiated air. If the carbonic acid present be more than 50 per cent., there is sudden spasm of the glottis. 2. Obstruction to the entrance of oxygen to the lungs and blood. 3. Blood not passing to the lungs, as from an embolus. 4. Alteration of the hemoglobin, as in poisoning with carbonic oxide. 5. Loss of blood. What are the Symptoms of Asphyxia, in order ? 1. Hyperpneea, soon followed by dyspnoea, when both movements of expiration and inspiration are exaggerated. 2. A short stage, during which the desire for air dis- appears, the individual still remaining conscious. 3. Unconsciousness, convulsions, and paralysis of the respiratory centre. In the convulsive stage, the expiratory efforts predominate. 4, Paralysis of the heart, and death. In this, the stage of exhaustion, we find lingering and long drawn inspirations gradually becoming more and more feeble. What is the State of the Heart after Death ? The right side of the heart, and systemic veins near it are gorged with blood; the left half of the heart and arteries almost empty. The pulmonary artery is gorged. Give an account of the Circulatory Changes in Asphyxia. At first the systemic blood pressure rises greatly, but the pressure in the pulmonary artery only to a slight extent, 59 This rise is due to the venous condition of the blood stimu- lating the vaso-motor centre in the medulla. The heart is now enfeebled by the venous blood circulating in the coronary vessels, and the left side may come to a standstill for a time owing to the great resistance to its contraction. The vaso-motor centre becomes paralysed from want of oxygen, the systemic vessels then dilate and the blood pressure falls almost to zero, while the left ventricle resumes beating feebly. The blood now accumulates on the right side of the heart, as the weakened right ventricle is unable to drive it through the lungs. In ordinary cases, too, the violent attempts at inspiration draw the blood into the right side of the heart, and help greatly to produce its engorge- ment, What method is usually employed in Asphyxia ? Sylvester’s method of artificial respiration. What means are adopted to restore the Circulation ? Hot cloths or a hot sponge over the region of the heart ; rubbing the limbs ; sometimes venesection from the external jugular to relieve the engorged right heart. How does Carbonic Oxide cause Asphyxia ? It displaces the oxygen from, and itself combines with, the hemoglobin of the red blood corpuscles (see page 8). Sulphuretted hydrogen produces the same EFFECT, but it acts as a REDUCING agent. In what Tissues is Respiration most active ? In muscle, nerve-cells, and glands. 60 What is peculiar about Gland Respiration ? The blood from a gland at rust is dark venous; when the gland is active, the blood leaving it resembles arterial. Why ts this ? Because so much more blood passes through it in a given time ; hence, it is not reduced to the venous condition. How is Oxygen stored up in the Muscle ? It is not known. Muscle contains no free oxygen ; yet it takes it up and fixes it somehow, and will continue to discharge carbonic acid for some time even when it is impossible to obtain oxygen from without. This is called intra-molecular oxygen. On what does the Rapidity of Tissue Respiration depend ? Chiefly on— 1. The activity of the tissues. 2. Temperature : more rapid at a low temperature. 3. Age: most active in childhood and youth. Edinburgh: Printed by E. & 8S. Livinastong, 4 Melbourne Place. An Ley F a | it CATECHISM SERIES. (3 ee, PHYSIOLOGY: Part IV. DIGESTION (Including Mouth, Stomach, Pancreas, and Liver). 7 EDINBURGH: E. & S. LIVINGSTONE. PRINTED BY E. & S. LIVINGSTONE, 4 MELBOURNE PLACE, EDINBURGH. PHYSIOLOGY. PART IV. DIGESTION. Explain the two words ‘ Secretion” and “ Excretion.” Secretion.—The constituents of a secretion do not, as a rule, pre-exist ready-formed in the blood, but require special organs and a vital process for their elaboration—the products are formed in organs by a vital process, and serve some ulterior object—e.g., milk. Excretion.—The component parts of an excretion, on the other hand, exist ready-formed in the blood, and are simply abstracted therefrom—the educts are simply elim- inated from the blood by organs for that purpose and discharged as useless—e.g., urea. What does the word “ Nutrition” include ? J. The means by which new material is conveyed to the tissues of the body. 2. The transformations it undergoes in the tissues. 3. The means by which it is got rid of when it has served its purpose, and become effete or useless. 4 What are the Objects of Nutrition ? 1. To build up new tissues and repair the old. 2. To yield the various forms of energy—e.g., to produce heat—to do bodily work—to do mental work, ete. Is Mueus Digestible ? No, it is not digestible; it is always excreted, not ab- sorbed. Its chief uses are to keep the parts moist, lessen friction, etc. The sticky principle is called “ mucin.” How is it Secreted ? It is secreted by various glands from the one end of the alimentary canal to the other, by— 1. Mucous glands on the dorsum and sides of the tongue—lingual glands. 2 Labial glands, on the inner surfaces of the upper and lower lips, but not at the angles of the lips. Buccal, palatine (on the hard palate), and molar. Tonsils—very freely. Pharynx and cesophagus. Pyloric glands of stomach. Brunner’s glands in the duodenum. . Below this, chiefly by the “chalice cells,” which are specially marked in the large intestine. SAD TP Describe the General Characters of the Buccal Saliva. It is a colourless, viscous, frothy, alkaline fluid of sp. gr. 1004 to 1008, containing about 4 per cent. of solids. It contains detached squamous cells, and salivary corpuscles ; ° these latter are modified mucous corpuscles with a single nucleus. They do not exhibit an amceboid movement, but they do show a peculiar form of motion known as “Brownian movement.” Give its Composition. 1. Water, - - - - - 995.16 2. Organic solids— Epithelium, E 3 : 1.62 Salivary corpuscles, Ptyaline, - - Mucin. - - Albee. s- a Globulin, - - 3. Inorganic solids, - - - - 1:84 4. Gases—carbonic acid, oxygen, and nitrogen. Note specially the presence of PRrorzips. What is Ptyaline ? It is an albuminous body of the nature of a ferment, and has a special action on starch. Name a Special Salt present. Sulpho-cyanide of potassium, found in the PaRoTID saliva. If the teeth are decaying the quantity is said to be increased. How is it Recognised ? It gives a red colouration with neutral ferric chloride, which is unaltered by the addition of acids—e.g., hydro- chloric,—but bleached by mercuric chloride. 6 What is the Chemical Reaction of the Saliva? It is slightly alkaline. What Amount ts Secreted in Twenty-four hours ? About 34 pounds. What are the Functions of the Saliva? 1. It moistens the mouth and assists speaking. 2. It assists mastication and deglutition—the mucin is specially for deglutition. 3. It assists gustation, because. it dissolves substances, and the solution then affects the taste-buds. 4. As regards digestion, it transforms starch into grape sugar (or maltose) after various intermediate stages. Has Saliva any action on Fats or Proteids? Practically none. On what does its action on Starch depend ? On the presence of ptyaline. What is Ptyaline ? It is a hydro-lytic ferment, because it causes the sub- stance acted upon to take up water. It is not used up or destroyed in the conversion of starch into maltose, but can convert an indefinite amount provided the products of its action (dextrine and maltose) are removed as fast as formed. For this reason its action is spoken of as ‘‘cATALYTIC.” The squames and corpuscles present in the saliva have no effect on starch. 7 What are the Conditions of its action ? Its action is assistEpD by— 1. Moderate heat—about the temperature of the body, 100°F. A‘temperature above 140°F. kills it. 2. It is most active in a slightly alkaline or neutral medium ; it may also act in a sLicHTLy acid medium, though the presence of ;}, per cent. of hydrochloric acid is sufficient to stop its action. 3. Removal of the products of its action as fast as they are formed. 4, It acts much more quickly on cooked than upon raw starch. Its action is RETARDED by— 1. Cold—if frozen, its action is stopped at least for a time. 2. The presence of acids and strong alkalies. 3. The presence of excess of the products of its action. Is the Acidity of the Stomach sufficient to destroy its power ? No; the gastric juice contains ‘03 of hydrochloric acid, ‘ but this does not destroy its power. Why does it act more readily on Cooked Starch ? When starch is cooked, the cellulose coat of the granules is ruptured, and therefore the saliva gets at the starch directly, and has not to break down the cellulose coat first, as it must do when the starch is not cooked. 8 Can you Represent the Changes by Chemical Equations ? It is most probably something like the following :— The molecule of starch is probably more complex than usually represented (the usual symbol is C,H,,.0;)— viz., C,,H;,0,;—e., three times the usual symbol. It is supposed at first to take up one molecule of water thus— Cy sH3 001; +H,0 re C,H, 20¢ a 20H, 90;— this last being dextrine. Then dextrine takes up more water thus— 2C,,H,,0; + 2H,O =2C,H,,0,—grape sugar, or some prefer to call it, Manrosr. Its rotatory power is three times greater than grape sugar; its reducing power is less. Maltose is said to form 70 per cent. of the sugar produced by the action of ptyaline on starch. Note then about Pryating, that it is— 1. A ferment. 2. It is present in very small quantity. 3. Its activity depends on temperature. 4, A high temperature, strong acids, and alkalies destroy it. 5. It undergoes no change itself, it is not used up— called therefore ‘“ Catalytic.” 6. It is hydrolytic (makes the substance acted upon take up water) and amylolytic (2.¢., it converts the starcH into sugar). 9 How can the different Stages of its Action be demonstrated ? If saliva be added to starch paste, or jelly, and the whole kept at the temperature of the body, the following changes occur :— 1. lo Iodine at first will give a BLus colour, showing the presence of UNCHANGED starch. The paste or jelly becomes thin and watery; this is before any chemical change takes place. Iodine added to the soLuBLE starch now present, still gives a BLUE colour. . Iodine added later, gives a reddish brown, or dark sherry colour, from the presence of ERYTHRO- DEXTRINES. . Later, Iodine gives no colour at all—this is because of the presence of ACHROO-DEXTRINES. . In the last step of the process, when Fehling’s solution is added we get a rusty red precipi- tate—the sugar now present reducing the cupric oxide (in Fehling’s solution) to Cup- ROUS OXIDE. What Glands Secrete the Saliva ? It is secreted by three pairs of glands—parotid, sub- maxillary, and sublingual—as well as by smaller glands beneath the mucous membranes of the tongue and cheeks. To what Class of Glands do they belong ? To the compound racemose group. 10 Give a list of such Glands found in the Human Body. 1. The salivary glands. Lo Mucous glands of the mouth. . Brunner’s glands in the duodenum, Pancreas (?) . Sebaceous glands. OQ TR ow Mammary glands. ma Lachrymal glands. Cowper’s glands (in the male). 2 . Bartholini’s glands (in the female). How do the Salivary differ from each other ? They differ both in structure and secretion-— 1. The parotid is a TRUE SALIVARY gland. 2, The human sublingual is a TRUE MucoUS gland. 3. The human submaxillary is a muco-saLivarY gland. Describe the Structure of the Parotid Gland. a The ducts, traced back, end in fine branches, around which the terminal recesses of the gland are grouped, and into which they open. The saccules or ALVEOLI are formed by a basement membrane, which is reticulated and lined by a layer of short columnar or pyramidal cells with round nuclei. The cells are very granular, and almost fill the alveoli, no lumen being visible. The nuclei are towards the circumference of the alveoli. 1l How do the Cells differ during Rest and during Secretion ? During Rest the cells contain numerous granules which obscure the nuclei; they (the cells) almost fill the alveoli, no lumen being visible. After secretion the granules almost disappear, only a few remaining near the lumen, the cells have become smaller, and the lumen larger. Describe the Ducts. The smallest simply consist of a basement membrane, and flattened epithelial cells. The larger ducts contain white and yellow fibrous tissue, and in some cases, non-striped muscular tissue ; in this way they can squeeze out the saliva. They are lined by columnar or cubical epithelium ; the part of the cell nearest the lumen of the tube is very granular, and contains the nucleus, while the part next the basement membrane is striated longitudinally—like the teeth of a comb. Describe the Sublingual Gland. As compared with the parotid the tubes are larger, contain a larger lumen, and have larger cells lining them. The cells are of two kinds—(1) Mucous or cenrrat cells, which are transparent columnar cells with nuclei near the basement membrane. Like the corresponding cells in the parotid gland, they are very granular. (2) Semi-lunes of Heidenhain, or crescents of Gianuzzi, are cresentic masses of granular PARIETAL or marginal cells found here and there between the basement membrane and the central cells. They are small and very granular at rest. 12 How do the Cells differ at Rest und after Secretion ? The cENTRAL CELLS in their resting state contain a transparent substance called muciaen—the cells being large, transparent, spheroidal, and nearly fill the alveoli. When the gland is secreting, the mucigen is converted into mucin, the cells swell up, appear more transparent, and stain deeply with logwood. During rest the cells become smaller and more granular. The PARIETAL CELTS (semilunes) increase in size during secretion. What ts the Structure of the Submaxillary Gland ? It isa mixed or muco-saLivary gland, and parts present the structure of true salivary, and other parts of true mucous glands. Point out some of the Staining Reactions of the Gland Cells In the case of the submaxillary gland, the central cells when at rest do not stain readily, but the semilunar cells do. After secretion the central cells stain readily, and this is more marked the longer the stimulation. The cells of the parotid behave like the cubical cells of the gastric glands, when the sympathetic nerve is stimulated, but not from stimulation of its other nerve. Give the General Characters of the Saliva obtained from the various Glands, 1, Parotip.—-This is the most watery. It is clear, limpid, and not viscid, and not very markedly alkaline. On standing it becomes turbid from the precipitation ot calcium carbonate (from the escape of carbonic acid), It 13 contains globulin, but little or no mucin or corpuscles. Sulpho-cyanide of potassium is present. It has a less powerful action on starch than the secretion of the other glands, besides being less alkaline and more watery. The parotid is a TRUE SALIVARY or sEROUS gland. 2. SuBuincuat.—This is a TRUE mucous gland; its secretion is the most viscid of the three, and contains more solids than either of the other two, though it does not seem to be so powerful in its action on starch. 3. SUBMAXILLARY.—This is intermediate in composition between the other two. Its secretion is more alkaline and viscid than that of the parotid, though not so viscid as the sublingual secretion. It contains many corpuscles, and much proteid matters. It is the most active of the three in transforming starch into sugar. Name the Nerves of Secretion for the Submaxillary and Sublingual Glands, 1. Chorda Tympani. 2. Sympathetic fibres, from the superior cervical ganglion. Where does the Chorda come from ? It is a branch of the facial (seventh cranial) and joins the lingual branch of the fifth under the lower jaw, and finally leaves the fifth, and runs as a small nerve beside the duct of the gland to the gland. What Sets of Fibres does the Chorda contain ? l. It has secretory fibres to the secreting cells of the gland. 14 . 2. Vaso-inhibitory fibres passing to the submaxillary ganglion—which is probably a peripherally placed vaso- motor centre. How is the action of the Chorda studied ? Put a canula into the duct of the submaxillary or the sublingual gland, and then stimulate the chorda tympani. What takes place ? 1. There is a rapid flow of very watery, limpid saliva. 2. There is a great dilatation of the blood-vessels of the gland, so that— 3. The blood flowing through the veins is semi-arterial, and— 4. There may be a venous pulse. 5. There is, further, a production of heat during secretion. Is the Rapid Flow of Saliva due to the Dilatation of the Vessels ? No; they are concomitant but independent phenomena. How would you Prove this? Give the animal a dose of atropine; the secretory set of fibres of the chorda are paralysed, but not the vaso-inhibitory. On stimulation now the vessels dilate as before, but there is no secretion of saliva. Hence the flow of saliva is not the RESULT of the dilated state of the vessels, and is not there- fore a mere act of filtration, but is a vital process. 15 What reason is there for believing that the Submarillary Ganglia are Vaso-Motor Centres ? Because when the sympathetic fibres passing to the gland are cut, and even when the superior cervical ganglion itself is removed, this does not seem to produce much effect on the tone of the blood-vessels in the gland. When the chorda is stimulated the activity of the ganglia is inhibited, and hence the dilatation of the blood-vessels. Give another Proof tending to show that the Dilated Vessels are not the Cause of the Secretion ? It was shown by Ludwig that the pressure of the salivary secretion in Wharton’s duct may considerably exceed the blood pressure in the arteries; this being so, the rapid flow of saliva could not be due to mere filtration, nor directly dependent upon the dilated state of the vessels. The water is not secreted by filtration, but by vital action of the cells. What Effects are Produced by Stimulating the Sympathetic ? When the sympathetic is divided in the neck, and the upper end stimulated, we note— 1. The blood-vessels of the gland are very markedly constricted. 2, There is a scanty secretion of VERY VISCOUS saliva, rich in salivary corpuscles, and lumps of protoplasm; the specific gravity is high, and the action on starch is powerful. 3. A small quantity of dark venous blood escapes from the veins. It will be seen, therefore, that secretion takes place even though the blood-vessels are constricted, the gland cells deriving their nourishment from the lymph. 16 Compare the Effects of the Two Sets of Nerves on the Blood- Vessels ? 1. When the chorda tympani is stimulated, the vessels dilate much, because this nerve inHIBITS the peripherally placed vaso-motor centres. 2. When the sympathetic is stimulated, the vessels are much constricted, because this nerve sTimMuLaTEs the peri- pherally placed vaso-motor centres. What are the Nerves of the Parotid Gland ? 1. Fibres that pass from the glosso-pharyngeal, through its tympanic branch, through the tympanic plexus to the SMALL SUPERFICIAL PETROSAL NERVE and otic glanglion, and thence by the auriculo-temporal nerve to the parotid gland. 2. Sympathetic, from the superior cervical ganglion. What are the Exciting Causes of Salivary Secretion ? 1. It is usually a reflex act. 2. Emotional states. 3. Movement of the jaws. 4, Various drugs. Name the Afferent Nerves implicated. 1. The glosso-pharyngeal, to posterior third of tongue. 2. Lingual branch of the filth, to the anterior two-thirds of tongue. 3. Long buccal, to the cheeks. Ue What is the Position of the Salivary Centre ? It is probably at the lower part of the pons, or upper part of the medulla, but higher centres exist on the surface of the brain, where the sensation of taste is perceived by the mind. Give Examples of Emotional Causes. The mouth may “water” at the sight or thought of food. Fear may have an opposite effect, and stop the secretion entirely—e.g., in the ‘Rice ordeal.” What part does the Movement of the Jaws play ? These movements seem to increase the flow, but that is probably purely mechanical, the contraction of the muscles simply squeezing out the secretion. Name some Drugs that affect the Secretion ? PHILOCARPINE causes a great flow of saliva. ATROPINE has the reverse effect. AcETIc acipD, and chewing the root of the PYRETHRUM, also cause a great increase in the flow of saliva. What is meant by “ Paralytic Secretion” ? ‘When the nerves of a gland are all divided (¢g., the submaxillary gland, pancreas, etc.), two or three hours after that the gland begins to secrete continuously and abundantly ; it is very thin and watery, and goes on till the cells are exhausted—it may last a week. The gland grows less and may degenerate. B 18 What are the Causes of this Secretion ? The causes are very obscure. It may be due to— 1. Vascular dilatation, from division of the vaso- motor nerves. 2. Trophic changes in the gland itself. It seems that the vital forces of the gland thus set free from the influence of the nervous system run. riot. Note the following points in reference to the salivary secretion :— 1. Increased filtration is not the cause ; because when the nerves of secretion are paralysed by atropine, we still get dilatation, but no secretion, though the lymph spaces become distended with fluid. 2, It is not due to increased blood pressure, pressing the lymph through. This is shown by the fact, that the pressure in Wharton’s duct during the secretion of saliva, is GREATER than the blood pressure — may even be twice as great. 3. It is not due to endosmoses, because the mucin and ptyaline secreted have a very low en- dosmotic equivalent—not, for example, like sugar which has a very high endosmotic equivalent, but no such substance is secreted by the glands. 4. Cut off an animal’s head rapidly and stimulate the chorda tympani, the flow of saliva is very copious, and that too in the absence of blood supply. or . It can only be stated, therefore, that it is due to the viraL activiry of the protoplasm of the 19 gland cells, whereby water is moved from the lymph spaces into the cells and from these into the sacculi of the gland. The diffusion of water by electrolysis is supposed to be something analagous in Physics. Give a short description of the Glands of the Mouth. 1. Mucous Granps.—Compound racemose glands near the root of the tongue, and lined with low cubical epithelium ; the cells are mucin-forming. 2. Serovs Guanps (Ebner’s glands).—Also near the base of the tongue; the ducts open into the trenches around the circumvallate papillae, and in other parts where taste- buds occur. There are no clear mucin-forming cells in these: the cells are granular and secrete an albuminous fluid, and are specially related to the sense of taste. They are always secreting, and wash away substances from the taste-buds after they have stimulated the sense of taste — this is necessary in order to keep them properly sensitive and in good working order. 3. Sorirary Guawnps, also at the base (‘Lingual Tonsil” ). —tThese consist of collections of retiform tissue into little masses (“follicular glands” or “lymphoid follicles”). These nodules are placed in the walls of recesses or crypts in the mucous membrane—thus resembling the tonsils in structure, Give the Movements of the Jaws, and the Muscles causing them. 1, The jaws are closed by— (1) Masseter. (2) Anterior part of temporal. (3) Internal pterygoid. 20 bo . They are opened by— (1) Gravity. (2) Muscles that draw down the hyoid bone—sterno- hyoid, omo-hyoid, platysma. (3) Mylo-hyoid, genio-hyoid, and chiefly by the digastric. 3. The grinding movement— By the alternate action of the two external ptery- goids, combined with the action of the elevators and others. 4, Protraction by— The two external pterygoids acting together, assisted by the masseter and internal pterygoids. 5. Retraction by— ; The posterior fibres of the temporal. What other Muscles assist in Mastication ? The buccinator and orbicularis oris keep the food from passing into the interval between the teeth and the cheek. The tongue also moves the food from side to side, and squeezes the softer parts of it against the hard palate. What are the Nerves of the Tongue ? 1. Motor— Hypo-glossal, to all the extrinsic and _ intrinsic muscles. 2] 2. Sensory— (1) Common sensation. (a) Anterior two-thirds, lingual. (6) Posterior third, glosso-pharyngeal. (c) A twig from the superior laryngeal branch of the vagus supplies a part of the tongue at sides and front just close to epiglottis. (2) Special sense of taste. (a) Anterior two-thirds, chorda tympani. (b) Posterior third, glosso-pharyngeal. 3. Secretory— To the mucous glands in the dorsum, chorda tympani. Give the Intrinsic and Extrinsic Muscles of the Tongue. 1. The Intrinsic (confined to the tongue)— (1) Superficial Lingual—Longitudinal fibres just beneath the mucous membrane, from the apex back to the hyoid bone. These fibres turn up the tip of the tongue. (2) Inferior Lingual—A rounded muscular band along the under surface from base to apex, between the genio- hyo-glossus and the hyo-glossus. This muscle turns down the tip of the tongue. (3) Transverse fibres—These form the greatest part of the substance of the tongue. They lie between the upper and the lower linguals, and pass out from the fibrous septum of the tongue to the dorsum and edges. They narrow and elongate the organ. (4) Vertical fibres—These form a series of curves, with the concavity outwards, from the dorsum to under surface. 22 2. The Extrinsic (take their origin elsewhere, but are attached to tongue). (1) The Stylo-glossus—In deglutition these muscles raise the sides of tongue, and form a hollow on the dorsum of that organ. (2) The Hyo-glossus opposes the stylo-glossus, and makes the dorsum convex. (3) Genio-hyo-glossus— Posterior fibres protrude tongue. Anterior fibres retract it. The middle part, or muscle as a whole, depresses it. (4) Palato-glossus—This properly speaking belongs to the palate. Give a Short Description of the Tonsils. There is one on each side of the fauces, between the anterior and posterior pillars. Each tonsil is about the size of a hazel nut, being about half-an-inch in length and a third of that in thickness. The surface towards the fauces has ten or twelve openings ; these lead to little crypts like those in the dorsum of the tongue. The crypts somewhat resemble a Florence flask in shape. In the wall of the crypts are mucous glands and nodules of lymphoid tissue (“solitary glands”). The crypts are lined by the mucous membrane of of the mouth. Into these crypts the mucous glands open. The whole tonsil is surrounded by a fibrous capsule. What is the “ Pharyngeal Tonsil” ? It is a semi-circular belt of nodules of lymphoid tissue (“solitary glands”) extending across the pharynx, from one Eustachian tube to the other, on the same level as the tonsils, 23 Describe the Epithelial Lining of the Pharyna. The upper part (respiratory) is lined with ciliated columnar epithelium (to the level of the floor of the nose). The lower part and the csophagus are lined with stratified squamous epithelium. What ts the Fibrous Bug of the Pharynx ? At the upper part the submucous connective tissue is thickened, forming a membranous sheet of tissue, and this is called the “ fibrous bag of the pharynx.” What are the Muscles of the Pharynx ? 1. The three constrictors.—These are imbricated, the lower part of the superior being overlapped by the middle, and so on. They strengthen the wall of the pharynx, and contract in a peristaltic wave from above downwards. Nerves—from the pharyngeal plexus. 2. Stylo-pharyngeus (two).— These draw the larynx upward and forward during deglutition, so as to enable it to be closed by the epiglottis. Nerve—The glosso-pharyngeal. 3. Salpingo-pharyngeus (two),— They pass from the Eustachian tube to the substance of the palato-pharyngeus. They open the Eustachian tube during deglutition, assisted by the levator palati. 24 What are the Muscles of the Soft Palate ? fibres from great superficial 1. Levator palati Nerves from Meckel’s ganglion ; | petrosal, from facial. 2. Azygos uvule 3. Tensor palati—nerve from otic ganglion; fibres from third division of fifth. 4. Palato-glossus—form anterior pillars of fauces, and are lost inside of tongue. They constrict the fauces and shut off the bolus from the mouth. 5. Palato-pharyngeus—form posterior pillars of fauces. Between the “pillars” of the fauces we find the tonsils. The Nerves of the “pillars” are the palatine branches from Meckel’s ganglion (from second divison of fifth). What are the Stages of Deglutition ? ! 1. A voluntary stage. 2, An involuntary stage. What other Division is sometimes adopted ? Ist Stage —Voluntary. 2nd Stage—Involuntary and automatic—i.e., where the food and air passages cross each other: it is as perfectly performed in the new-born child as in the adult. | 3rd Stage—Involuntary and reflex. Describe the Voluntary Stage. 1, The food is made into a round bolus by the tongue. 2. The jaws are closed to give the hyoid bone and the muscles that act on the tongue a fixed point. | @- : ape oF Ven +f, 25 3. The mass is moved towards the pharynx, being pressed between the tongue and the palate, and forced back by the former in a peristaltic wave. The tongue is shortened and the tip raised by the intrinsic muscles, and partly by the stylo-glossus. The dorsum at the posterior part is made convex, and the hyoid bone drawn forward and upward by the mylo-hyoid. Describe the Involuntary Stage. This stage begins when the food reaches the posterior third of the tongue—i.e., the region of the glosso-pharyngeal nerve. 1. To prevent the food from pussing into the windpipe, the larynx is drawn up to meet the epiglottis, and the epiglottis is pulled or pushed down so as to cover the larynx—the vocal cords themselves at the same time being closed. In this way there is a double safeguard. 2. To prevent the bolus from passing into the nose, the soft palate is raised and made tense, and is‘met by the wall | of the pharynx (the superior constrictor coming forward to meet it). The muscles forming the posterior pillars of the fauces tend to meet in the middle line, while the uvule fills up the gap between. Thus the entrance into the posterior nares is blocked up, and the soft palate forms a sloping roof, guiding the bolus down the pharynx, as it cannot pass back into the mouth because of the contraction of the anterior pillars of the fauces. 3. Lastly, the stylo-pharyngeus and the palato-pharyngeus contract, and the pharynx is drawn up to meet the descending bolus, just as a glove may be drawn over the finger. Once in the grasp of the constrictors, it is forced down by their peristaltic contraction from above downward. 26 Describe the Structure of the Gsophagus. It extends from the cricoid cartilage, opposite the 6th cervical vertebra, and passes through the diaphragm on a level with the 9th dorsal vertebra. It has a general fibrous covering outside, then the following coats :— 1. Muscutar—in two layers. (1) External longitudinal layer, which is at first in three fasciculi, but soon forms a continuous layer round the tube. (2) Internal circular—aAt the upper and lower parts the direction is horizontal; in the middle it is slightly oblique. The upper fourth of the muscular coat is striped muscle ; the middle two-fourths are mixed ; and the lower fourth almost all non-striped. 2. Susmucous coat—Consists of areolar tissue: here ' the compound racemose glands are embedded. 3. Mucous coat—This coat has papille like the skin It is firm, and paler than that of the pharynx or stomach. When not distended, it is thrown into longitudinal folds. There is also a “‘ muscularis mucose.” It is lined by stratified squamous epithelium. The glands are most numerous at the lower end of the tube. Give the Motor Nerves of the Voluntary Stage. The 5th to the muscles that close the jaws. The 9th to the muscles of the tongue. What are the Motor Nerves of the Involuntary Stage ? Besides the above, we have— The pharyngeal plexus, to the constrictors. 27 The glosso-pharyngeal, to the stylo-pharyngeus. The 5th, to tensor palati. The 7th, to the levator palati and azygos uvule. Meckel’s ganglion to the pillars of the fauces. What is the Position of the Centre for Deylutition ? it is situated in the medulla above the respiratory centre. This can be proved by slicing away the brain and medulla above this point. Name the Hucito-Motor Nerves of Deglutition. 1. The chief one is the glosso-pharyngeal, to the posterior third of the tongue. The lingual nerve has nothing to do with it. 2. Lingual filament of the superior laryngeal branch of the vagus. When the superior laryngeal nerve is divided, and its upper end stimulated, deglutition is excited. 3. Branches of the fifth. How would you excite Deglutttion in an Unconscious Person ? By placing the food on the posterior third of the tongue— Z.e., in the region of the glosso-pharyngeal ; but in profound coma, swallowing becomes impossible. Why is the Upper Part of the Muscular Coat of the Esophagus “ Striped” Muscle ? Because in this region muscular contraction must be RAPID, as the food at this point has to cross the orifice of the larynx. 28 GASTRIC DIGESTION. What are the Coats of the Stomach ? 1. Serous coat, derived from the peritoneum. It covers the entire stomach excepting along its two curvatures, where it is loose and where the large blood-vessels pass. 2. Muscular coat. 3. Submucous coat—This lies between the muscular and mucous coats, and consists of areolar tissue and fat cells. It is the seat of the passage and division of the blood- vessels. 4, Mucous coat. Describe the Muscular Coat. It consists of THREE sets of non-striped muscular fibres— 1. Loneirupinat—directly continuous with the longi- tudinal fibres of the cesophagus. It is spread over the cardiac end, and then chiefly along the curvatures (especially the lesser). On the anterior and posterior surfaces, it is almost absent. At the pylorus it forms a thick uniform layer, passes over it and becomes continuous with the longitudinal layer of the duodenum. 2. Crrcutar—These fibres from a complete layer: it is specially marked at the pylorus, forming its sphincter. This layer is not continuous with the circular layer of the esophagus. 29 3. INNER or OBLIQUE LAYER.—It is incomplete and chiefly marked at the cardiac end, and towards the pylorus. At the sides, the fibres are spread out and blend with the circular fibres. This layer is continuous with the circular fibres of the cesophagus. Give a general description of the Mucous Coat. It is thickest at the pylorus and thinnest at the great cul-de-sac, and is but loosely attached to the tissues under it, so that when the stomach is empty, it is thrown into ruc&. It is pale or pink in colour; but during digestion it is bright red, and after death a dirty brown. It consists of epithelial and sub-epithelial tissue and is mostly com- posed of glands. When examined with a simple lens, ALVEOLI are seen, and in each of these the mouths of three or four of the gastric glands. It is lined by a single layer of columnar epithelium with a clear, vertically striated hem ; there are also many mucin- secreting chalice cells. The epithelium is continued a little way into the mouths of the glands. Describe the Glands of the Stomach. The mucous membrane consists of the tubuli arranged close to and parallel with each other. The tubuli are shortest at the cardiac end, and are usually simple; at the pylorus they are longer and, though mostly simple, yet the closed end may be cleft into many branches. The glands are of two kinds— 1. Pytoric or Mucous Guanps. — These are mos numerous towards pyloric end; the duct is long and is lined by epithelium, the same as that covering the mucous 30 membrane. But in the deeper parts they are short and cubical, like the a-DELAMORPHOUS or central cells of the peptic glands. During secretion they become finely granular. As compared with the Puptic Guanps, the ducts are longer, the lumen larger, the branches shorter and probably more numerous ; they are lined by cells, resembing the central cells of the peptic, but there are no large ovoid or parietal cells. 2. Peptic Guanps.—Tubular in shape, and simple or compound: the duct is short. In these glands there are two kinds of cells (excluding those lining the duct)— (1) At the upper part (neck) large, coarsely granular, ovoid cells, the so-called “peptic cells”; tovtards the lower end of the gland they only occur here and there. They occur at the circumference of the tubule, resting on and bulging out the mucous membrane. The nuclei are very light in colour. They are known as DELAMORPHOUS or PARIETAL cells. (2) At the lower part of the gland, between these, the space is occupied by finely granular, polyhedral, or angular cells. These are known as A-DELAMORPHOUS, CENTRAL OY CHIEF CELLS, so-called because there is reason to suppose that they, and not the “ peptic,” secrete pepsin. The lower end of these glands is usually slightly covered. The cells are occupied by numerous granules during fasting, which mostly disappear during a period of activity—like the cells of the salivary glands. The cells rest on a basement membrane. Between the mucous membrane and the submucous coat is the ‘“ mus- cularis mucose”; this consists of two layers of non-striped muscular fibres, the outer being longitudinal and the inner circular. This coat also sends bundles of muscular fibre 31 up between the gastric glands towards the mucous membrane. Near the mouths of the glands, these fibres run transversely, forming a network. Perhaps these muscular fibres express the juice from the follicles. Give a Short Account of the Blood-Vessels, Nerves, and Lymphaties. The Arteries divide and sub-divide in the submucous coat, and then pass up between the tubuli and form a fine capillary plexus on their walls, round their mouths, and in the alveoli. The Vutns pass in a similar manner backward. The Nerves come from the vagi, with twigs from the sympathetic, through the solar plexus. The Lympuatics arise by a fine network of vessels in the mucous membrane, and amongst the tubules. They then pass into a fine plexus just beneath the glands, pierce the muscularis mucose, and form another network in the submucous coat. What is the “ Pylorus” ? It consists of a circular fold of the mucous membrane, and in it a strong band of circular muscular fibres. Describe the Gastric Juice. It is a thin colourless acid fluid, of sp. gr. 1005, con- taining 4 to 1 per cent. solids, in man. The daily amount varies—an average being 13 lbs. in twenty-four hours. 82 Name its chief Constituents. 1, Pepsin. A milk-curdling ferment. . Free hydrochloric acid. Mucin. . Salts (chiefly phosphates and chlorides). . Water, 99°5 per cent. a oR wl What is the amount of Hydrochloric Acid present ? The Free acid varies from ‘2 to ‘3 per cent. Is the Hydrochloric Acid all free? No; but there is more present than could be neutralised by the bases present. If we add carbonate of calcium, car- bonic acid gas is given off. But, add oxalate of lime, it is not dissolved, though hydrochloric acid dissolves it. It is therefore likely that all the acid is not quite free, but united with some feeble base present—perhaps LEUCIN. Are there other Acids present ? DuRING DIGESTION various organic acids appear—acetic, malic, lactic, and butyric. The last two are formed by the fermentation of sugar to some extent, during digestion, and this may be stopped by giving dilute sulphuric acid. The acid reaction of normal juice is due to the presence of hydrochloric acid. What is the action of Pepsin ? This is an albuminoid substance of the nature of a FERMENT; it is soluble in dilute hydrochloric acid or glycerine. Pepsin, AIDED BY HYDROCHLORIC ACID (or some 33 other organic acid), Nor PEPSIN ALONE, transforms proteids into peptones. This is the essential property of the gastric juice ; it dissolves the ENVELOPES of the fat globules, but has no action on fat itself. How is the Special Relation between Pepsin and an Acid proved ? 1. To water and fibrin add 0°3 pepsin, and keep at 100°F. Resutt—No change. 2. To another of the same add 0-2 hydrochloric acid, and keep at 100°F. Resutt—Soon becomes syntonin, and is slowly transformed into peptones. 3. Again to water and fibrin add 0:3 pepsin, and 0-2 hydrochloric acid, and keep at 100°F. Resutt—Rapidly changed into peptones. How does the Fibrin behave ? It first swells up and becomes transparent, and then falls into flakes. So also albumen becomes transparent on the surface and is dissolved from without inwards. How does Peptone differ from other Proteids ? 1. Its solution is diffusible. 2. It is not coagulated by heat or mineral acids, like albumen ; but, like albumen, it is precipitated by tannic acid, mercuric chloride, and excess of alcohol, and lead acetate. 3. It is not precipitated by yellow prussiate of potash and acetic acid. : 4, Peptones give a pink colour on the addition of caustic potash, and a trace of cupric sulphate or Fehling’s solution. c 34 What are the Conditions that favour Gastric Digestion ? 1. It goes on best at the temperature of the body. _ 2. Too much acid, or neutralisation, will stop the action. 3. Concentration of the products of its action will stop it. 4, When the substances to be digested are minutely subdivided. If the products are removed as fast as they are formed and the acidity kept normal, a given amount of gastric juice will convert an unlimited quantity of proteid into peptone, as pepsin is not used up during digestion. How does Pepsin differ from Ptyaline ? Pepsin must have an acid present; there is a special tie between the two. Pryatine acts best in an alkaline medium, but there is no special tie between it and the alkali. What other Ferment is present in the Gastric Juice ? A milk-curdling ferment—Rennet. Is the Juice always being Secreted ? No; only when the mucous membrane is stimulated. The “curve of secretion” resembles that of the pancreas. How may tt be Stimulated ? 1. MecuanicatLy.— Stimulate the mucous membrane with a feather or glass rod. The presence of food is the normal stimulus, and this is most marked when it is semi-solid. 2, CHEmicaLLy.— Ether vapour, dilute alcohol. Dilute 35 alkalies excite it much, probably because they excite osmosis. Saliva (because it is alkaline), pepper, mustard, etc. 3. Agreeable emotions stimulate the flow; hence the value of jesters or music during dinner. 4, A painful stimulus may stop flow. 5. In febrile states it is diminished. What is the Daily Amount of Juice Secreted ? Thirteen pounds. Describe the behaviour of the Glands during Secretion. 1. Pepric Guanps.— Before secretion the central or a-delamorphous cells are pale and finely granular, and stain readily. During digestion they become swollen, turbid, and more coarsely granular, and stain much more readily, At a later stage they become smaller, shrunken, and more granular, and stain much more still. They become loaded with some granular material during secretion. (In the pancreas the reverse obtains.) The delamorphous (‘ovoid” or “peptic”) become enlarged and project more on the out- side of the gland, and become clearer. 2. Prroric Gianps.—The cubical granular cells become more granular and enlarged; they behave just like the a-delamorphous cells of the “peptic” glands. How are the Constituents Formed ? The Pxrsin is probably produced by the cubical cells of the pyloric glands, and by the “central” cells of the “peptic.” The Acrp, though its formation is obscure, is probably produced by the delamorphous cells (the ovoid or “peptic” 36 cells) of the “peptic” glands. This is rendered likely, for the following reasons :— 1. In the long tubular glands of birds, the upper part is acid, the lower part alkaline. 2. In the frog’s stomach (where there are many “ ovoid” cells) the contents are acid. At the lower part of the cesophagus there is a pepsin-like fluid, and here there are many of the cubical cells, 3. Inject yellow prussiate of potash into the veins, and a blue colour is produced only at the surface of the mucous membrane—z.e., at the mouths of the glands. Whence is the Acid Derived ? It is derived from the splitting up of chlorides; the alkali is secreted by the pancreas, while the acid is secreted by the gastric mucous membrane—especially from common salt—the Na goes to the pancreas, the HCl to the stomach. What are the Nerves of the Stomach ? 1. The Sympathetic. 2. The Vagus. What is the Function of the Sympathetic ? It is the vaso-motor nerve of the stomach. Plexuses and ganglia are found between the two layers of the muscular coat, and in the submucous coat. The great splanchnic passes to the semi-lunar ganglion of the solar plexus, and from that fibres pass to the stomach. Cut the great splanchnic, the blood-vessels are paralysed and the mucous membrane becomes red; stimulate the peripheral end, and it becomes bloodless and pale. 37 What ure the Functions of the Vagus? 1. It is moron to the cardiac end of the stomach; the | motor centres for the rest of the stomach are the ganglia — in its own walls. 2. It is also the SENSORY nerve. 3. Some of the afferent fibres are VASO-INHIBITORY. 4, It is also SECRETORY. , How is its Vaso-Inhibitory action shown ? When food enters the stomach the mucous membrane becomes red, because impulses pass to the vaso-motor centre and inhibit the activity of some of its cells, and we thus get reflex dilatation of the blood-vessels. How would you prove this ? Cut the vagi during digestion, and the mucous membrane becomes pale. Stimulate the peripheral end, there is no change, because impulses do not pass down. Stimulate the central end, the vessels again dilate. How is Secretion affected by Division of the Vagi? If the vagi be cut during digestion, the secretion of gastric juice stops. If food be introduced into the stomach a day or two after, this secretion will begin again, even though the vagi are divided. Hence, it is supposed that there are some ganglia in the wall of the stomach that are centres of secretion, and there action is excited, by the presence of food in the stomach, through the vagi. Why should Division of the Vagi stop Secretion? Perhaps, because of the anemic state of the wall of the stomach; but there are probably peripherally-placed 38 vaso-motor centres subordinate to the great centre in the medulla, and these soon gain so much power that they can command the blood-vessels alone. Distinguish between Albumen and Peptone. ALBUMEN. PEPTONE, 1. Fairly soluble. 1. Very soluble. 2. Precipitated by nitric acid. 2. Is not precipitated. 3. Precipitated by acetic acid 3. Is not thus precipitated. and yellow prussiate of potash. 4, Coagulated by heat. 4, Is not. 5. Not diffusible. 5. Is diffusible. 6. With strong solution of 6. With the same reagent, a red caustic soda and a_ trace of | or pinkish colour is produced. cupric sulphate, a violet colour is produced. How does Peptone resemble Albumen ? They are both precipitated by tannic acid, lead acetate, and by mercuric chloride. What is Parapeptone ? It differs from peptone in being precipitated by neutral- isation, and is either a by-product in the change from proteid into peptone, or a stage between the two. For example, in the conversion of albumen into peptone by the gastric juice, if we neutralise the fluid, so much of the proteid is precipitated (= parapeptone) and so much remains in solution (= peptone). What are the great objects of Gastric Digestion ? 1. To render proteids diffusible. 2. To render coagulated proteids soluble. 39 Is the Pepsin used up in Digestion ? No, it is not used up ; its action is catalytic. The hydro- chloric acid is used up; it combines with the proteid molecules, and the action of artificial gastric juice will soon stop unless we add more acid. Give the action of the Gastric Juice on various Foods ? ; Crete Mik is first coagulated by the milk-curdling ferment; / after this it is dissolved and converted into peptone in the | usual way. HYALINE CARTILAGE is converted into peptone, and a sugary substance, WHITE FIBROUS TISSUE is converted into gelatine, but gelatine is not converted into peptone, so that feeding on gelatine means starvation. The SaRcOLEMMA OF MUSCLE, envelopes of fat cells, are converted into peptone in the usual way. Exastic TIssvz, epidermic tissues, mucin, nuclei, are not digested at all. CoaGULATED ALBUMEN, if minutely subdivided, is more easily digested than raw. Mixx is not affected (as to digestibility) by boiling. Mzat is more digestible by boiling or roasting, if not over-done. Fat and Srarcu are not affected by the gastric juice ; but the fat envelopes are dissolved and the fat thus set free. The juice is too acid for the conversion of starch into sugar (started in the mouth) to go on. CaNE suGaR is partly converted into grape sugar, probably due to a ferment in the mucus. 40 What Conditions affect Gastric Digestion ? It is affected by— 1. The nature of the food. 2. The amount of the food. 3. The state of division of the food. If minutely subdivided, it presents a greater sur- face to the aetion of the gastric juice. Food should be well masticated. 4. Perfect admixture of the food with the juice. 5. It goes on best in the absence of mental and muscular exertion. 6. Food at regular times, as the stomach must have rest. 7. Weak digestion may be aided by a little dilute alcohol or bitter substances; also by liquor pepticus (Bencer), or dilute hydrochloric acid, before a meal. 8. Retarded by alkalies, because they neutralise the acidity of the gastric juice. 9 9 0 8) In artifical digestion, it is necessary to remove the products as fast as they are formed and keep the acidity normal. What is “ Chyme” ? The gastric digestion changes the food into a grey fluid, and this is called “‘chyme.” After about three hours the plyorus opens, and it is discharged into the duodenum. There the acidity is neutralised by the pancreatic juice. What are the Gases of the Stomach ? Nitrogen, Carbonic Acid, Hydrogen. 41 What is their Origin ? Some are swallowed in the saliva, but others are produced during digestion—e.g., CO, and H are produced by the butyric fermentation. Why ts the Wall of the Stomach not Digested ? There are various theories— 1. Itis protected by epithelium and mucus (BERNARD) 2. The wall is kept alkaline by the blood (Pavy). 3. Due to an inherent vital activity of the tissues, where- by it resists the action of the juice. This is much the same as Hunter's theory of the ‘vital principle.” If this vitality be diminished, the wall may be digested, the same as any other dead tissue—e.g., in post-mortem digestion, or where a part of the stomach wall is injured, or where a part is cut off from the circulation as in thrombosis of one of its small blood-vessels. Gastric ulcer may originate in this way. What are the Movements of the Stomach ? During digestion the contents of the stomach are kept in constant motion by the peristaltic action of its walls; currents are set up in this way, the food travelling along the large curvature and returning by the lesser, or along both curvatures, and then returning along the centre of the viscus. What is Vomiting ? It is usually a retlex act, whereby the contents of the stomach are expelled through the cesophagus and mouth. 42 Describe the act. At first there is salivation and nausea, then a deep in- spiration is taken and the glottis closed to fix the diaphragm and press it against the stomach. The wall of the stomach itself contracts in peristaltic waves, running from the pylorus to the cardiac end; the cesophagus is shortened, and the sphincter, at its junction with the stomach, is suddenly opened by fibres in the stomach wall continuous with the longitudinal fibres of the cesophagus. The muscles of the abdominal wall contract, and the stomach, being fixed by means of the diaphragm, the contents are forced into the cesophagus ; the mouth is open and the neck stretched out so as to make the passage as straight as possible, and just as the contents are coming up there is an additional expira- tory movement which prevents the food from entering the glottis and sends it through the mouth or nose. What are the Chief Events ? 1. Dilatation of the cardiac end of the stomach. 2. The extrinsic pressure of the abdominal wall, against the fixed stomach, in an expiratory effort. What are the Nerves concerned ? Motor, such as the phrenics, lumbar, intercostals, and sacral nerves (nerves to muscles of the abdominal wall). Vagus, to dilate the cardiac end of the stomach. Insalivation, facial, along chorda tympani. Motor nerves of the various muscles of the cesophagus, and arytenoideus. 43 Where is the Vomiting Centre ? In the medulla, in the neighbourhood of the respiratory centres: it seems as if it were a combination of inspiration and expiration. What are the Exciting Causes ? 1. Irritation of the terminal fibres of the vagus from the presence of irritants in the stomach, or from an unhealthy state of its walls—e.g., catarrhal conditions. 2. Irritation of the terminal fibres of other branches of the vagus or sympathetic, as in tickling the fauces, peritoneal or uterine troubles. 3. The cause may be cerebral—e.g., as a tumour in the brain, and from the subcutaneous injection of certain drugs, as apomorphia. 4. By disgusting smells, sights, or tastes. What are the Afferent Nerves ? These depend on the cause: they may be the glosso- pharyngeal (as in tickling the fauces or posterior part of tongue), the vagus (as in cases where the contents of the stomach are the exciting cause), the sympathetic (as in strangulation of the intestine, passage of renal or biliary calculus), the first cranial (as from disagreeable smells), the the second cranial (as from disagreeable sights), the nerves of taste, ete. What is peculiar about the Glosso-Pharyngeal ? When it is excited in a normal manner, then we get DEGLUTITION. When it is excited in an abnormal manner, we get vomitinc—the reverse of deglutition. 44 What is the Cause of the “ Air Appetite”? It is due to the condition of the centre in the medulla oblongata, and not so much to the condition of the lungs, because an animal desires to breathe quite as much when the vagi are cut as when they are uncut. It is a very powerful appetite, and can hardly be resisted more than one minute, and three to five minutes would mean death. This is because the store of oxygen in the system is so small, and the respiratory centre soon becomes paralysed. What ts the cause of the “ Water Appetite,” or Thirst ? It is usually referred to dryness of the mouth and fauces; it is not due to that alone, for the mouth may be dry and yet no thirst, or vice versd. 1. It is partly due to dryness of the mucous a eee because when the mouth is wetted it is allayed for a time, but very soon returns. 2. It is chiefly due to deficiency of water in the blood. Inject water into the blood, it is allayed, though when taken by the mouth, the effect is more marked and lasting. Name some Conditions that cause great Thirst. Excess of saline matters in the blood; hemorrhage, especially after gunshot wounds; usually also it is marked at some stage of most fevers. What takes place when Water is withheld too long ? One may do without for two or three days; but, if it is not relieved, delirium, mania, and death result. Is it wise to drink Sea-Water under such cireumstances ? No; for it would only hasten death. 45 What is the Cause of the Hunger Appetite ? 1. It is partly due to emptiness of the stomach, and may . be allayed for a time by introducing even indigestible sub- stances, as clay, etc., but it soon returns again. 2. It is chiefly due to the state of the blood, or perhaps rather to the state of the tissues, wanting certain substances that the blood is unable to supply. If the vagi be cut, the sensation is still felt ; in this case the sensation cannot come from the stomach, but must arise in the central nervous system, probably from cells near the root of the vagus. That it is due to the state of the blood is shown by the fact, that if enemata be injected into the bowel, or nutrient material into the blood directly, the feeling is allayed. Food cannot be done without longer than three weeks, seldom so long. INTESTINAL DIGESTION. Describe the Position and Relations of the Pancreas. It is narrow, long, and flattened, and les obliquely across the posterior wall of the abdomen behind the stomach, and opposite the first lumbar vertebra (see “Anatomy,” Part IV., page 32). What ts its Structure ? It is a compound racemose gland, closely resembling the parotid, though of a looser texture. It has a long wHITE duct (the “canal of Wirsung”) that stands out in marked contrast with the creamy colour of the pancreas itself. It consists of lobes and lobules, and the main ducts are called “lobar” ducts. 46 First, we have— . The “canal of Wirsung,” the pancreatic duct. Lobar ducts—then Lobular ducts, which end in Intermediary ducts—and these end in SS Se . The acini or follicles. The intermediary ducts enlarge and become. convoluted tubes lined by low columnar cells; the bases of the cells stain most readily. The pancreas is really intermediate in structure, between a compound racemose and a compound tubular gland. The small ducts, instead of dilating into acini, dilate into a convoluted tube or follicle. Describe the Cells at Rest and during Secretion. When at rest the cells consist of an outer narrow zone that stains slightly with carmine, and an inner large granular zone that does not stain. During secretion the inner zone grows less and less till it disappears, and the outer one grows correspondingly larger until the whole cells stains readily. The granular part does not stain readily, and the granules appear during rest and disappear during stimulation (compare with the gastric glands). ie ee What is the Composition of the Juice ? ‘Water. Organic matters—as Albumens —serum-albumen, alkali-albumen, cesin. Ferments. Leucin. Salts—Curbonate of sodium, chlorides of sodium and potassium, phosphates of calcium, magnesium, and sodium. 47 What are its Characters ? It resembles saliva, and is a clear, viscid, strongly alkaline fluid. It contains a large quantity of carbonate of sodium, associated in a peculiar manner with albumen. Sp. gr., 1010 to 1015. At first it does not contain leucin; but if it stands, then leucin and tyrosin appear. Serum- albumen, alkali-albumen, are present as well as cesin; if the juice stands these are digested, and hence the leucin and the tyrosin. What is the daily amount produced ? From twelve to sixteen ounces. How is tt obtained for Experimental purposes ? It is usually obtained from the dog by means of a pancreatic fistula; the abdomen is opened, the duct exposed, and then attached to the skin surface. Describe its Secretion. It is not constant; it begins soon after food is introduced into the stomach, and continues all the time that the food is there, and for one or two hours after it has passed into the duodenum. The maximum rise occurs just after food is taken; then there is a fall, and again a slight rise when food passes into the duodenum. Like other glands, when its nerves are all cut, we soon get a continuous “ paralytic secretion.” How many Ferments are there in the Juice? It contains four ferments. 48 Give their respective actions. 1. A rat-spLittine ferment ; this emulsifies and saponifies: fats. This is the great action of the pancreatic juice: to a slight extent it splits up neutral fats into glycerine and fatty acids. 2. A suGAR-FoRMING ferment, changes starch into dextrine and maltose. : 3. A PEPTONE-FORMING ferment (¢rypsin), changes proteids. into peptones. 4, A MILK-cuRDLING ferment. What becomes of the Fatty Acids? They unite with the alkalies of the juice to form soaps, and the soaps thus formed assist the emulsification of the undecomposed fat. What is the nature of an Emulsion ? It consists of a very minute mechanical subdivision of the fatty matters. Probably the presence of albumen is the chief cause, and the soaps produced assist the action. Oil, albumen, and soap, produce an emulsion; there must be an attraction between the bodies forming the emulsion. An alkali assists—e.g., carbonate of sodium. There must be an alkali or albumen present, or perhaps both. In what Animal is the Emulsifying action of the Pancreatic Juice easily observed ? In the rabbit, because in this animal there is a great distance between the entrance of the bile and pancreatic ducts into the intestine. Above the pancreatic duct there is no milkiness in the lacteals, but below its entrance they are milky and white. 49 What is the action of the Juice on Starch ? It converts starch into dextrine and maltose even more rapidly than the saliva. What is its action on Proteids ? It converts them into peptones without the aid of any acid. The action is helped very much by the presence of an alkali, though this is not essential. Compare and Contrast Gastric and Pancreatic Digestion. VANCREATIC, 1. Fibrin or other proteids are dissolved without preliminary swelling; they remain opaque as before, and are simply corroded away. 2. Essentially an alkaline diges- tion. 3. Much leucin, tyrosin, indol, ete., produced from the decomposi- tion of formed peptones. 4, Arrested by acidification. 5. Contains 1 per cent. of car- bonate of sodium. 6. No special tie between the juice and the alkali; alkali could be done without. 7. By-product, a kind of alkali- albumen. GASTRIC, 1. Proteids swell up, become transparent, and seem to slowly pass into solution. 2. Essentially an acid diges- tion. 3. Only a small amount of these bodies produced. 4, Arrested by neutralisation. 5. Contains -2 per cent. of free hydrochloric acid. 6. Special tie between the juice and the acid ; apid gourd not be * done without. Ao. [ 7. By-product, a kind of ‘acid- albumen. PEPTONISED FOODS. Would the Liquor Panereaticus be of any use in the Stumach? No; because it is seized upon by the ferments and the hydrochloric acid, and rendered useless D ctf Ber “ 50 Which Juice should be preferred in Peptonising Foods? Trypric (pancreatic juice) is to be preferred to Prpric (gastric juice) for peptonising foods ; because that peptonised by peptic digestion has a very disagreeable taste, whereas that by tryptic digestion has not. Name a good Maker. Benger. How is Peptonised Milk made ? Add a table-spoonful of liquor pancreaticus (Benger) and 20 grains of sodium bi-carbonate to a pint of milk ; heat to 100°F., and keep at that temperature for two hours; then boil for a few minutes to arrest further digestion. How is Peptonised Mulk-Gruel prepared ? Half a pint of thick oatmeal gruel is prepared in the usual way, and boiled for a few minutes. Then add an equal volume of cold milk to it, then a tablespoonful of liquor pancreaticus, and 20 grains of sodium bi-carbonate. Keep warm under a tea-cosy for two hours, and then stop further digestion by boiling for a few minutes. How would you prepare Peptonised Beef-Tea ? Half a pound of minced beef, half a pint of cold water, and 20 grains of sodium bi-carbonate are mixed together, and allowed to simmer gently for an hour and a half, and then cooled to about 100°F, A table-spoonful of liquor pancreaticus is then added, and the mixture kept at about 100°F. for two hours; it is then strained and boiled for five minutes. 51 THE LIVER. What are its Coats ? It has two— 1. Serous. 2. Fibrous. Describe the Coats. 1. The Sprovs.—This is derived from the peritoneum, and covers the entire organ except at the posterior border, portal fissure, and fissure for the gall-bladder. 2. The Fisrovus.—This invests the entire gland. It is very thin and is united to small processes between the lobules. At the transverse fissure it becomes continuous with a sheath of areolar tissue that surrounds the branches of the portal vein, hepatic artery, and bile-duct as they ramify in its substance. This prolongation is known as the ‘capsule of Glisson.” State the Leading Features observed by the Naked Eye on the Cut Surface of the Liver. 1. A number of patent openings, with very thin walls— the HEpaTIC VEINS. 2. Other little strands of tissue (‘capsule of Glisson”’)» and in the track of these three vessels — portal vein, hepatic artery, and bile duct. 3. The Loputss of the liver; these give a torn surface of the liver its granular appearance. 52 Describe a Lobule. The liver is made up of Loses (see “Anatomy,” Part IV., page 38), and these in turn are composed of Loputes. Each lobule is about j; inch in diameter, oblong or polygonal in shape, and closely packed one upon another. Sometimes there is a little connective tissue between the lobules, but in man this is very scanty, though in the camel and pig it is well marked. Each lobule consists of cells compactly arranged around branches of the HEPATIC VEIN (=INTRA- LOBULAR VEIN), and each lobule rests on a vein by its base (=SUB-LOBULAR VEIN) into which the central vein of the lobule opens. Each lobule is thus penetrated from the circumference by a close network of capillaries, and the minute beginnings of the bile ducts. The circumference of the lobule is surrounded by the inter-lobular veins, which are branchlets of the portat vein. In each lobule we find three networks— 1. Of hepatic cells. 2. Of blood-capillaries. 3. Of bile-capillaries. Describe the Heputic Cells. In shape they are rounded or polygonal: they have a yellow granular appearance, and a well-marked prominent nucleus ; there is an inter-nuclear network and an exceed- ingly dense inter-protoplasmic network. There is a very thin delicate cell-wall. They are joined together by an albuminous cement, which contains fine channels for bile- capillaries. During digestion the cells contain minute oil- globules and glycogen. The cells are arranged in a net- work of anastomosing columns, which may seem to radiate from the centre of the lobule. 58 Describe the Hepatic Vein. It begins in the centre of the lobules as the intra-lobular vein, by the convergence of the capillaries of the lobule: this opens into sub-lobular veins, and these in turn unite to form hepatic venous trunks, and these unite and pass to the posterior border of the liver and end in the vena cava inferior, The hepatic veins are not accompanied by any other vessel; the walls are very thin and firmly adherent to the liver substance, and they have no valves. On the other hand, the portal vein, the hepatic artery, and bile duct lie together in canals in the liver substance (=‘“ portal canals”) and are surrounded and separated from each other by fibrous tissue (= “capsule of Glisson”). Describe the Portal Vein in the Liver. It subdivides into branches that ramify between the lobules and anastomose freely (=INTER-LOBULAR VEINS). Small twigs pass into the lobule and ramify in its outer zone; the blood is returned by the hepatic vein. Describe the Hepatic Artery. It is chiefly nutritive to the connective tissue. It ends in three sets of branches— 1. Vaginal, to supply the walls of ducts and vessels and ‘“Glisson’s capsule.” 2. Capsular, to fibrous coat of liver. 3. Inter-lobular twigs, that ramify chiefly in the MIDDLE ZONE of the lobule. How is this last Statement proved ? Tie the portal vein and inject a solution of carmine into the blood-vessels; the pigment can only be carried to the liver by the hepatic artery, and only the capillaries in the middle zone of the lobule are stained. 54 Name the “ Zones” of the Lobule. 1. PeripHeraL—portal vein capillaries. 2. MippLte—portal vein and hepatic artery capillaries. 3. CentRaL—hepatic vein capillaries. Describe the Bile Ducts. They commence in a fine plexus of capillaries which run between and surround each individual cell forming the lobules of the liver. In a very fine section minute openings may be seen between the cells, which are apertures of the capillary ducts. They never lie close to blood-vessels, but are always separated by part of a cell. From the lobules they pass to the inter-lobular plexus, and then join with each other to form the larger ducts, and finally leave the liver as one large duct. The larger bile ducts are lined with columnar epithelium, their coats being formed of fibrous tissue with many elastic fibres, with a mixture of non-striped muscular tissue as well in the larger ducts. In the larger ducts there are many mucous glands. How could you Inject the Bile Capilluries ? By injecting indigo-carmine into the blood-vessels. It is excreted by the liver; if the animal be killed in about an hour, the pigment will be found in the bile capillaries ; if killed in about ten minutes, the blue pigment will be seen in the hepatic cells—thus showing that they must fill the bile capillaries. How can the different Zones of the Lobules be shown ? 1. Tie the Huraric artery and inject indigo-carmine as above ; when the animal is killed and the liver examined, it is found that the pigment is being excreted by the cells at the periphery of the lobule, the central zone being colourless. 2. Tie the PorraL very, inject and examine as above; the periphery is almost colourless while the middle zone is coloured, 55 ‘What other potnt does this prove ? That part of the capillary network of the lobules is supplied by the hepatic artery. What are the Nerves of the Liver ? The nerves come from the solar plexus, and the left vagus; the branches pass along with the hepatic artery. The vagus is sensory; the sympathetic, vaso-motor; the secretory nerve is doubtful. Give the Course of the Bile. 1. From the liver cells, into the 2. Bile capillaries round the cells. 3. Then into the inter-lobular plexus, and other bile ducts within the liver. 4, It leaves the liver by the right and left hepatic ducts. 5. Through the common hepatic duct—formed by the union of right and left hepatic ducts. 6. Passes up the cystic duct, to 7. Gall-bladder. 8. Down cystic duct. 9. Through common bile duct—formed by the union of the cystic with the common hepatic duct. 10. Into duodenum. During digestion it need not pass up to the gall-bladder, but go straight into the duodenum at once. What are the Functions of the Liver? 1. To secrete bile. 2. To secrete glycogen. 3. It is supposed to have some special action on albuminous substances. 4. In the foetus it is believed to give origin to white blood corpuscles. 56 What are the Physical Characters of the Bile ? It is an alkaline, golden or brownish-yellow fluid, of a bitter taste, and specific gravity 1018. If it remains long | in the gall-bladder it becomes viscid from the presence of 'mucus. In graminivorous animals—e.g., the ox—it is a golden-green colour. What ts the Source of the Mucus ? It is secreted by the general epithelium and mucous glands of the larger bile-ducts and gall-bladder—especially the latter. How would you show its Presence ? It is precipitated by dilute acetic acid. What is the Composition of Bile? Per Cent. Water, . ; ‘ . 85:92 Sodium salts of the ‘pile ats ‘ 9-14 Fat, ; : 5 : : ! 0:92 Cholesterine, . 3 : ‘ 5 0:26 Mucin and pigments, . ‘ 2°98 Inorganic salts, sulphate of icant iron phosphate, and chloride of sodium, . ‘ i ‘ i 0-78 Leucin, Terosin, Urea, Xanthin, Ebmnokeaithin, ; \ traces, Note the absence of proteids, and the presence of calcium sulphate, and iron. Name the Bile Acids. 1. Tauro-cholic acid—the chief. 2. Glyco-cholie acid. 57 Give one murked Difference in their Composition, / Tauro-cholic acid contains sulphur. [ Glyco-cholic does not. Whence is the Sulphur derived ? From the breaking up of proteid molecules. What takes place when they are Boiled with Dilute Mineral Acids ? 1. Guyco-cHotic acrip takes up water, and splits into— (1) Glycocin. (2) Cholic acid—thus Glyco-cholie Acid. Cholic Acid. Glycocin. C,,H,,NO,+H,0=C,,H,,.0; +C,H;NO, Note that cholic acid does not contain nitrogen, while glycocin does. 2. TavRo-cHoLic acrp also takes up water and splits into— (1) Cholic acid. (2) Taurin—thus Tauro-cholic Acid. Cholic Acid. Taurin. Cy,H,;NSO, + H,O=C.,H,,0;+C.,H,NSO; Note the presence of sulphur in taurin, and its absence in cholic acid. What is the Composition (rational) of Glycocin and Tuurin ? Grycocin—is Amido-acetie acid— [C,H (NH,)0(0H)] Tavurin—is Amido-ethyl-sulphonic acid— (80. (0H)(C.H, {NH.})] ae 58 Does the Proportion of the Acids vary in different Animals ? Yes; in the ox, for example, we chiefly find sodium- glyco-cholate. In carnivora, it is chiefly sodium-tauro- cholate. What becomes of the Bile Acids ? They are to a small extent excreted in the feces. Taurocholic acid is not found, because it is decomposed into cholic acid and taurine. Most of the acids are re-absorbed from the alimentary canal, and pass to the liver again by the portal vein. This is proved by analysing the faces ; they only contain about one-eighth of the daily amount of sulphur secreted by the liver, so that about seven-eighths are re-absorbed, probably in the form of taurine, and pass back to the liver, to be perhaps again reconstructed into its former compound. What is Pettenkofer’s Test for the Bile Acids ? To dilute bile is added a few drops of a solution of cane- sugar, and after that some strong sulphuric acid ; the solution becomes first cherry-red, and then of a purple colour. What is Cholesterine ? It is the only free alcohol found in the body under normal conditions, and is composed of carbon, hydrogen, and oxygen. It is insoluble in pure water, but is held in solution by the bile salts; it sometimes becomes precipitated and forms gall-stones. It is soluble in ether, chloroform, and boiling alcohol. It occurs in white crystals, usually in the form of rhombic plates—very often with a bit out of one corner. 59 Give a Chemical Test for it ? With strong sulphuric acid and a trace of iodine, it. becomes a violet colour, which afterwards changes to green and then red. Name the Bile Pigments. 1. Brumvsis—the cause of the reddish colour. ! 2. Bitiverpin—the green pigment. How are they affected by Oxidising Agents ? When treated with oxidising agents, bilirubin takes up. O. and becomes biliverdin. The pigments are excreted in the form of hydro-bilirubin. What other Substance has a similar composition ? Urobilin—found in urine. What Ovidising Agent ts usually made use of ? Fuming nitric acid—z.e., nitric acid holding in solution some nitrous acid. Whose Test is this? It is Gmelin’s test for the BILE Piaments; a play of colours is the result, but the green colour is the most evident. . What is the supposed Source of the Bile Pigments ? It is supposed that the red pigment comes from the hemoglobin of the blood. The red blood corpuscles are destroyed in the spleen and the hemoglobin set free, and carried by the portal vein to the liver. 60 Name some Points against this view. 1. Iron is not a constituent of the bile pigment, whereas it is a part of hemoglobin. 2. Bile pigment has a very simple composition, while that of hemoglobin is very complex. 3. Bile pigment has no absorption bands in its spectrum ; blood pigment has two such bands. Where is the Pigment formed ? Some hold that it is pre-formed in the blood, and that the liver merely abstracts it therefrom—because 1. Hematoidin, which bile pigment closely resembles, is produced from blood pigment without the aid of the liver. 2. The injection of a solution of hemoglobin into the blood-vessels is followed, not merely by increased excretion of bile-pigment by the liver, but also by excretion of bile- pigment by the kidney. Also, when the red corpuscles are broken down in the blood, as by injecting water, or phosphoric acid, or by the inhalation of ether or chloro- form, bile-pigment appears in the urine. Others maintain that the bile is not pre-formed in the blood, but that it is produced in the liver—because When the liver is excised, bile-pigment does not accu- mulate in the blood, nor does it appear in the urine; and once at least, in the human subject, the liver was so disorganised that it secreted no bile, and yet there was no jaundice, and neither bile-pigments nor bile-acids were found in the blood or in the urine. Name the chief Inorganic Salts of the Bile ? There is much sodium chloride; also some sulphate of calcium, and some phosphate of iron. It should be noted therefore that the iron is not in the pigment (as in the case of the blood) but in the sarrs, 61 What is the Source of Cholesterine ? It results from the metamorphosis of nervous tissue and protoplasm generally. It is purely an effete matter; it is found in the blood, and the hepatic cells abstract it therefrom. Where are the Bile Acids formed ? They are produced in the hepatic cells, as they are not | formed in the blood; they are produced from the metamor- phosis of proteids, especially taurocholic acid. Taurine is found in the blood, lungs, and spleen. Cholie acid is only found in the liver. What are the possible Causes of *‘ Biliousness” ? 1. It may be due to defective activity of the liver, and the consequent non-withdrawal of bile pigment from the blood, but is more likely to be due to— 2. A catarrhal condition of the bile ducts, impeding the exit of the secreted bile and so causing its absorption into the blood. It is very easily absorbed, as the secreting pressure is low. What ts the action of the Liver on Albuminous Substances ? The “circulating” albumen—i.ec., which has played its part in the economy and is now unfit for further use—is broken up-in the liver into— : 1. Glycogen. | 2. Fatty acids, which are oxidised to carbonic acid and \ water, and escape by the lungs. 3. Nitrogenous substances—as urea, uric acid; these | re-enter the circulation and are eliminated by the kidneys. | There is more urea formed in the hepatic cells than in . any other tissue. 62 State what you know of the Secretion of the Bile ? Its secretion is continuous, though it is not always ‘flowing into the intestine. The bile duct perforates the wall of the duodenum very obliquely, and though it has no sphincter, this probably acts as a valve, and closes the duct when the pressure of the secretion is small or wanting; when the pressure increases it is forced into the duodenum. ‘When the animal is not digesting, the bile is stored away in the gall bladder; during digestion the gall bladder is emptied, and after digestion it is quite flaccid. The secretion pressure is very low (unlike the saliva) and any obstruction to the outflow is speedily followed by its re-absorption into .the blood (Jaundice). The secretion is specially active during digestion. When the food from the stomach passes over the orifice of the bile duct at ‘“‘ Vater’s Ampulla” a gush of bile takes place—probably due to the acip fluid; alkaline fluids won’t cause a flow. There isa rapid rise after meals, reaching its maximum in from 4 to 10 hours: there is then a slight fall, and afterwards a slight rise. What Amount is Secreted in Twenty-four Hours ? About forty ounces. How does Food affect its Secretion ? Food rich in proteids, it is increased. Great increase when liver is used as an article of diet. Less with ' vegetable food. Lean meat with a little fat is better than when there is much fat. What are the Supposed Causes of Secretion ? It is probably due to substances absorbed from the alimentary canal. The liver is not excited reflexly from 68 the stomach or duodenum ; nor is the secretion due to an increase in the stream of blood passing through the portal vein to the liver. How is this proved ? Place gamboge in the intestine, and we get a great dilatation of blood-vessels but no increased secretion of bile; and mustard in the stomach or duodenum does not increase the secretion. What are the Nerves of Secretion ? They are not known. The sympathetic and the left vagus supply the liver, but these divisions make no differ- ence to the secretion. What are the Causes of the Inflow of Bile? fluid to the duodenum, and the bile flows out, because the 1. Muscular fibres of the gall-bladder—e.g., apply an acid ( muscular fibres are stimulated to express the fluid. 2. Pressure of the secretion itself. 3. Extraneous muscular compression — e.g., muscular } exercise causes a flow of bile into the intestine; the liver | is like a sponge, and the bile is squeezed out. It is important to distinguish between the bile-secreting, ' and the bile-expelling mechanism. What ts the destiny of the Bile? 1. It plays a part in digestion. } 2. Part of it is excreted. \ 3. Part of it is re-absorbed. 64 What ts the part played in Digestion ? , 1. It assists the absorption of fatty matters; when the _ mucous membrane is wetted with bile, the passage of oily ' matters is facilitated. 2. It helps the pancreatic juice in the emulsification of fats. 3. It stimulates the muscular fibres of the intestine, and causes the villi to contract reflexly, and thus pump or squeeze out the absorbed fatty matters into the under- lying lacteals. | 4. It is antiseptic to the intestinal contents. | | What part is Excreted ? Cholesterine—as stercorine. All the bile pigments—as hydro-bilirubin. Cholic acid (though taurocholic acid is not found). Probably taurocholic acid is decomposed into cholic acid and taurin; the former is excreted, while the latter is Heabaotbed: What part is Re-absorbed ? ' Most of the bile acid, especially raurin and its allied ' substances—i.e., sulphur-containing substances. . . Aol oa ence eka an. Seine ee ee Edinburgh : Printed by E. & S. Livinastonz, 4 Melbourne Place. Za /; be ee ee oe > 3 tf a= CATECHISM SERIES. Cr gL PHYSIOLOGY». PART V, THE INTESTINES, BLOOD GLANDS, AND KIDNEYS. 7 EDINBURGH: Ee @ S LIVINGSTONE. PRINTED BY E. & S. LIVINGSTONE, 4 MELBOURNE PLACE, EDINBURGH. oy Sy PART V. SMALL INTESTINE. What are the Main Parts of the Small Intestine ? The small intestine extends from the pyloric end of the stomach to the large intestine. Its length is about 20 feet ; it becomes a little narrower as it passes downwards. It has three main parts— 1. The duodenum—the first 10 or 12 inches. 2. The jejunum—the upper 2 of the remainder. 3. The ileam—the lower 2. How does the Duodenum differ from the rest ? It is the widest and most fixed part of the small gut, as well as being the shortest of the three parts (for Relations, etc., see ‘ Anatomy,” Part IV., page 31). Where does the Jejunum begin ? Where the duodenum ends—viz., at the point where the gut is crossed by the superior mesenteric artery. 4 What are the Coats of the Small Intestine ? 1. External Szrous or Peritoneal.—Covers most of it, but only the anterior surface of descending and transverse parts of duodenum. 2. Muscunar coat—two layers— (1) Outer longitudinal, entire but thin. (2) Inner circular, thicker and more distinct, with clefts here and there between the bundles. The muscular coat is thinnest at the lower part : the muscle is non-striped. Peristaltic movement is chiefly due to the inner layer of muscle. 3. Susmucous.—Loose connective tissue and fine elastic fibres: the blood-vessels divide in this coat before entering the mucous membrane. 4, Mucous MEMBRANE.—This has a velvety appearance from the presence of villi. It is covered by columnar epithelium with clear hem on free edge, with chalice cells. Next the submucous coat is the muscularis-submucose. What are the “ Valvulie Conniventes” ? They are PERMANENT folds of the mucous membrane of the small gut. They are crescentic and transverse, and each passes about } round the gut. They consist of two layers of the mucous membrane placed back to back and united by areolar tissue. What are their Uses? They increase the absorbent surface and delay the passage of food. Where are they found ? They extend from about 2 inches from the pylorus, and ’ end about the middle of the ileum. What are the “ Willi” 2 They are small processes of mucous membrane, conical and flattened, and about } inch in length. Where are they found ? Only ‘in the small intestine: they are largest and a numerous in the duodenum and jejunum, and grow smaller and are less numerous in the ileum. Give the Structure of a Villus from without in. 1. Columnar epithelium with the clear hem, and some goblet cells here and there. 2. Basement membrane, consisting of a layer of squamous endothelium. 3. Retiform connective tissue, with spaces and clefts lined with squamous endothelium. 4, A capillary network of blood-vessels. 5. A few longitudinal non-striped muscular fibres; at the apex of the villus these become continuous with the retiform fibres. 6. A lacteal in the centre; its wall is formed by squamous endothelium, Do the Villi absorb matters from the Intestine ? Yes ; diffusible substances like grape sugar, peptones, and water, pass directly through the columnar epithelium and so into the blood-vessels. Fatty matters are not diffusible, and so they pass through the interstitial clear cementing substance BETWEEN the cells, and pass into the central lacteal; they do not pass through the strize of the clear hem. | i | i | 1 6 How is the Lacteal Empticd ? The longitudinal non-striped muscular fibres in the villi contract, shorten the villus, and squeeze out the contents ; afterwards the villus is elongated again by the blood pressure in the capillaries. What are the Crypts of Lieberhiihn ? They are simple tubular glands; they have a basement. membrane supporting columnar epithelium of the usual type, mixed with goblet cells for secreting mucin. Beneath the basement membrane we find adenoid tissue. Where are they found ? They are found all through both small and large intestines. In the small intestine they open between the villi. In the large intestine they contain a great many more goblet cells than in the small. ' What ts thetr Function ? They secrete the ‘succus entericus.” What are Brunnei’s Glands ? | They are compound racemose glands, placed in the sub- . mucous coat; the ducts pierce the mucous membrane. In structure they resemble mucous or salivary glands. Where are they found ? They are only found in the duodenum. LIgBERKUHN’s crypts and Brunner’s GLANDS are the only two intestinal glands that pour their secretion into the _ small intestine. Glands from without, that empty themselves into the small intestine, are the Liver and pancreas. 7 What are the Solitary Glands ? They are isolated clumps of delicate retiform tissue, with spaces filled with lymph corpuscles. They have an envelope of condensed retiform tissue covered by squamous epithelium. They are placed chiefly in the submucous tissue but extend up and cause a slight bulging of the mucous membrane. Sometimes on the upper surface we find villi and crypts. Where are they found ? In both large and small intestine. What are Peye’s Glands or Patches ? They consist of groups of glands resembling the solitary glands in structure. They are oblong and placed lengthwise in that part of the circumference of the intestine most distant from the mesentery. Size, 1 to 3 inches x } inch. Open the gut, therefore, along the attachment of the mesentery. Where are they found ? Chiefly at the lower end of the ileum, and become fewer in number as we approach the jejunum. What other Tissue is largely found in the Intestines ? Lymphoid tissue is found in many places in the sub- mucous tissue in addition to that of the solitary glands and Peyer’s patches. What are the Lymphatics of the Intestine called ? Lacteals : these begin in the centre of the villi. What are the Blood- Vessels ? The Mesenteric Arteries: they anastomose VERY FREELY, because the intestines turn and twist about so much. What are the Nerves ? They are chiefly derived from the SUPERIOR MESENTERIC PLEXus—branches from the cceliac plexus, semilunar ganglia, and vagus. Final branches pass—one set between the layers of the muscular coat and is called AUERBACH’S PLEXUS, consisting of a close gangliated plexus. From this branches pass to form a second richly gangliated plexus in the sub- mucous coat, called MBISSNER’S PLEXUS. Give the Internal Characters of the various parts of the Small Intestine. DUODENUM. JEJUNUM. ILEUM. 1. Villi present. 1. Villi present. 1. Villi present. 2. Brunner’s glands. 2. None. 2. None. 3. Lieberkiihn’s follicles. 3. Lieberktihn’s follicles. | 3. Lieberkiihn’s follicles. 4. Solitary glands. 4. Solitary glands, 4. Solitary glands. 5. Valvule conniventes. 5. Many at upper part. 5. Few. 6. Opening of bile and pan-| 6. Not found. 6. Not found. creatic ducts. 7. No Peyer’s patches. 7. A few present. 7. Many present. The duodenum is also the widest and most fixed part of the small intestine. Note the position of the various structures— 1, Vittr—From about 2 inches from the pylorus to about the middle of the ileum, becoming fewer and smaller as we pass downwards. 2, Brunner’s GLanps—found only in the duodenum. 3. Crypts or LizserktHn—in both small and large intestines. 4. SoLITARY GLANDS, in both small and large intestines. 5. Pryer’s paTcHes, found chiefly at the lower end of the ileum, and grow fewer as we pass upwards towards the jejunum. 6. LyMPHoID TISSUE, in both small and large intestines. 9 What is the Digestive uction of the Secretion of Bruuner’s Glands ? The cells resemble those in the deep part of the pyloric glands of the stomach. The nature of the juice is not fully known: it contains mucin. When a part is isolated and a watery extract made from it, it is found that the juice can digest fibrin in the presence of hydrochloric acid, probably from the presence of pepsin. It has no action on fats or ° starches. In action, as well as structure, they thus resemble the pyloric glands of the stomach. How can we get the Secretion of Lieberkiihn Glands ? By Thiry’s method of artificial fistula. What are the Characters of the Juice ? It is a thin straw-coloured sTRONGLY ALKALINE fluid, containing albumen, mucin, ferments, and salts. What are its Digestive actions ? 1. It peptonises proteids, but not very rapidly. 2. It converts starch into dextrine and maltose. 3. It has an inverting ferment, changing cane into grape sugar. 4. It has a slight emulsifying power (Scuirr). 5. It assists the pancreatic juice to neutralise the acid chyme. What is Moreau’s Experiment on Paralytic Secretion ? He isolated a part of the small intestine, and then cut all the nerves passing to that section of the gut; the part was very soon filled with a fluid—the so-called ‘paralytic secretion.” 10 What Changes occur in the Contents of the Small Intestine ? They become mILKY after passing the opening of the pancreatic duct: aLKaLIny, about the middle of the small intestine ; and acquire a FECAL opouR at the lower end of the ileum. Describe the Lleo-Cecal Valve. The ileo-czecal valve (or more properly ILEO-CcOLIC VALVE) is placed at the junction of the small and large intestine. The ileum is, as it were, pushed through into the larger gut. The opening is slit-like and almost transverse to the direction of the large intestine. The surfaces towards the ileum are covered with villi; those towards the large intestine are smooth and without villi. It prevents reflux into the ileum but the intestinal contents can easily pass from the ileum into the large gut. The valve segments consist of two layers of mucous membrane enclosing a little areolar tissue, with many CIRCULAR muscular fibres (see “ Anatomy,” Part IV., page 28), Compare the Outward Characters of the Small and Large Intestines. LARGE, SMALL. 1. The external muscular layer 1. The external muscular layer in three longitudinal bands. uniform over entire circumference. 2. Puckered ; saceuli. 2. Not puckered ; no sacculi. 3. Appendices — epiploicee. — 3. No appendices epiploice. Little projections of serous coat filled with fat. 11 Describe the Coats of the Large Gut. 1. The Szrovus coat has little projections filled with fat, called APPENDICES EPIPLOICA. 2. The Muscunar coat— (1) The external longitudinal layer is collected into three flat longitudinal bands (except in the rectum)—anterior, posterior, and lateral: from the latter are the appendices epiploice, These bands are shorter than the whole length of the intestine, and hence the sacculi; when stretched the sacculi disappear. (2) The internal circular layer is much the same as in the small intestine. 3. The Susmucous coat.—Like that of the small gut. 4. The Mucous coat. — Is smooth: no villi, valvule conniventes, nor Peyer’s patches. Lieberkiihn’s follicles are larger, more numerous, and contain very many chalice cells, and hence secrete more mucin. The solitary glands are less prominent. In other points it resembles the corresponding coat of the small intestine. What Changes occur in the Large Intestine ? There is still a little digestion going on; absorption is very active and the contents are rendered semi-solid. The passage | of the contents is very slow, because of the indentations be- | tween the sacculi. Absorption goes on even in the rectum ; | and on this depends the fact that we may feed a patient with peptonised foods per rectum. In this case it does not matter much (so far as TASTE is concerned) whether we use the Liq. pepticus or the Liq. pancreaticus, nor need we destroy the ferment at a certain stage by boiling. To the food to be given, add the ferment; inject it into the rectum —the rectum acting as the “ tea-cosy.” 12 : Of what do the Feeces consist ? 1. Propucts OF DIGESTIVE SECRETIONS—as mucin, choles- terine, hydrobilirubin, pigments, cholic acid, stercorine, iron of the bile, and salts. 9. INDIGESTED PARTS OF Foop—as elastic tissue, hairs and other corneous substances, cellulose, chlorophyll, starch corpuscles, ete. 3. Propucts OF DECOMPOSITION OF FOOD — as indol, _ phenol, scatol, ete. The reaction is acid, due to acetic, butyric, and caproic ( acids—from fermentation. INTESTINAL PERISTALSIS. Describe this Movement. Peristaltic or vermicular movement is due to the combined movement of the two layers of the muscular coat of the gut. It is chiefly due to the circular coat; both layers of muscle alternately contract and relax, but work down the intestine in waves so as to propel the contents downwards. There is thus a rhythmic contraction of the circular fibres, a to-and-fro movement of the longitudinal, and a passive movement of the fluid to and from the loops—the whole constituting the worm-like or VeRMICULAR or peristaltic action. Under ordinary conditions they only move when there is a certain BULK of material inside. In the small gut the movement is rapid, while in the large it is slow. What is the Direction of the Movement ? It travels from above downward, but it can also be made to pass in the opposite direction—e.g., pinch the lower part of the gut, and the movements travel upward. 13 Where are the Centres for this Movement ? Ganglia in the walls of the gut. What Conditions excite this Movement ? 1. The condition of the blood—want of oxygen and increase of carbonic acid increase the movement very much. 2. Cold, to the abdomen—either cold air or water in- crease it. 3. Purgative agents increase it, as nux vomica, Calabar bean, senna, nicotine, etc. 4. Stimulating the lower end of the divided vagus will increase it. This must not be done in a fasting animal, or the experiment will fail. Fibres of the vagus pass to the solar plexus, and thence to the intestine. What Conditions diminish it ? 1. Over-oxygenated state of the blood. 2. Heat to the abdomen. 3. Drugs, like morphia, belladonna, henbane. 4, Depressing emotions. 5. Stimulation of lower end of the divided splanchnic. This inhibits the ganglia. It is not due to vaso-motor spasm and consequent anemia, because anemia per se quickens it. What are the Sphincters of the Anus ? These are two— 1. The external sphincter. 2. The internal sphincter about one inch further up: this is about half-an-inch in breadth, and is simply the circular coat prolonged further down than the longitudinal and very much thickened. 14 What ts their usual State ? In a state of tonic contraction. What ts this due to ? To the automatic action of an ano-spinal centre in the lumbar part of the spinal cord. How was this proved ? By Goltz’s experiment on dogs. What are the Exciting Causes of Defecation ? Superficially, it is the result of will, but it is carried out by an involuntary mechanism. Describe the Chief Steps of this act. It is initiated by peristalsis of the intestine, forcing the intestinal contents into the lower part of the rectum. The sensations due to their presence there leads to the voluntary part of the act. The ano-spinal centre is inhibited and an expelling mechanism brought into play—viz. : 1. Deep inspiration to force down the diaphragm. 2. Glottis closed, to give it a fixed point. 3. Muscles of abdominal wall contract, and + . Levatores ani contract and pull up the lower part of the rectum over feces. May it become purely a Reflex Act ? Yes; when the spinal cord is cut or destroyed in the dorsal region. In this case it is probably excited by the presence of feeces in the rectum, and the whole act due to peristaltic action entirely. 15 ABSORPTION FROM THE ALIMENTARY CANAL. What are the Two Paths of Absorption ? 1. The BLoop Caritisries—absorb peptone, sugar, water, and salts. 2. The Lacreats—absorb chiefly emulsified fats. The villi are the great agents of absorption. What ts the Essential Nature of Digestion ? It is the change of the non-diffusible proteids and starch into diffusible peptones and sugar, and the emulsification ~ - of various fats. What are the Causes of Absorption ? 1. Dirrusion.—This is the cause of the absorption of soluble matters. Fatty matters are not thus absorbed because they are not in solution, but only in a state of suspension. 2. Firrration.—This is the passage of fluids through ; a membrane, under the influence of pressure, and is’ the great cause of the absorption of fatty matter. It is assisted by— (1) Peculiar peristalsis of the intestine—causing a | form of forced pressure. (2) Capillary attraction when the surface is wetted with. bile. (3) Contraction of the muscular fibres of the villi: they contract and squeeze out the contents of the lacteal into the underlying lymphatic plexus, and thence to the mesenteric glands and thoracic duct. 16 What becomes of the absorbed Peptunes ? After entering the blood, they are almost immediately transformed into albumen. If peptone be injected into a vein, it very soon disappears. , How are Fatty matters absorbed ? The lacteals in the centre of the villus consist of a delicate layer of endothelium, the cells being connected with the branched cells of the retiform tissue, and these again with the basement membrane. The lacteals begin in blind ends, and communicate with smaller lymph spaces in the adenoid tissue around. The fatty particles pass through the interstitial clear matter between columnar cells cover- ing the villus, pass through the small lymph spaces in the adenoid tissue, and thence into the lacteal. GLYCOGENIC FUNCTION OF THE LIVER. What is the Essential Nature of this ? | The transformation of sugar of the blood of the porta? vein into glycogen, and storage of it into the hepatic cell The sugar absorbed from the alimentary canal disappears and glycogen appears. Does the Blood normally contain Sugar ? Yes; a small but pretty constant quantity. Is Glycogen found elsewhere than in the Liver ? | Yes; in muscle, and in amceboid protoplasm wherever it is found. 17 What are the Characters of Glycogen ? It is an amorphous white tasteless powder resembling starch ; soluble in cold water, giving an opalescent solution ; is insoluble in alcohol. It is a colloid, and is isomeric with starch. Jodine gives a red colour with it, which disappears “1 warming, and reappears on cooling. How is it transformed into Glucose ? By means of a ferment that appears in the blood, and | in the hepatic cells at death. Boiling water destroys this | ferment. How is it produced ? It is produced during the absorption of food by the metabolic activity of the hepatic cells (= ‘‘glycogenic function of the liver”). Produced from grape sugar by aehydration by the hepatic cells— Glucose. Glycogen. C,H 12 O,—H,0 =C,H409; It is stored up in the hepatic cells during digestion, and *3 used up during the interval. What are the Sources of Glycogen ? 1. The chief source is caRBo-HyDRaTES, though inosite and mannite do not produce it; glycerine produces it sparingly. 2. A small amount is produced from PROTEIDS. 3. Fats do not produce any. This is peculiar, because glycogen is produced from sugar: fat can also be produced from sugar, but fat cannot be transformed into glycogen. Bt 18 Why is Glycogen stored up in the Liver ? It is laid up during digestion, and used up in the interval—it is stored up in the form of granules. It forms a carbo-hydrate store, and is laid up when carbo- hydrates are abundant in the alimentary canal; this store is then drawn upon during the intervals as the needs | of the economy may require. This is because excess of sugar in the blood is injurious and would produce disease ; the amount in the blood is small but constant. What becomes of it at Death ? It is rapidly changed into glucose by means of a special ferment, that seems to increase in the blood after death. What is the Source of this Ferment ? 1. Destruction of blood corpuscles at death. 2. Stagnation of the blood at death. What is the destiny of Glycogen ? It leaves the liver during fasting, but in what form is not exactly known. What is Bernard’s Theory ? That glycogen is gradually transformed into glucose, and leaves the liver by the hepatic veins, and so supplies the systemic blood with sugar, which is constantly used up for the purposes of nutrition as the blood flows through the systemic capillaries. What Special Fact lends support to this Theory ? It is harmonious with what is known regarding trans- formations of sugar and starch in plants—e.g., the potato. 19 WVame a Weak Point in the Theory. The theory is based on analyses of blood in Frastine animals. Bernard found more sugar in the hepatic vein than in the portal vein: less sugar in the femoral vein than in the femoral artery. Hence, he concluded that sugar is produced in the liver, and disappears in the systemic capillaries. Who Opposes this Theory ? Dr Pavy, more especially. On what grounds ? On the ground that his method of analvsis was not sufficiently delicate. While he (Pavy) admits that the blood always contains sugar (whether glucose or maltose is doubtful) to the extent of 0°5 to 1 part per thousand, yet he states that he finds no sensible difference between the amount of sugar in the blood of the portal and that of the hepatic vein in a fasting animal, or between that of the femoral vein and the femoral artery. What is Pavy’s Chief Argument ? It is that glycogen does not, in the normal condition of the system, become transformed into sugar to more than a trifling extent. What is incomplete about Pavy’s Theory ? He does not state in what form glycogen leaves the liver, though he seems to incline to the idea that it leaves the liver as glycogen; but the amount of glycogen in the blood is not more than the amount of sugar above stated. This being so it is still an open question whether the glycogen leaves the liver in the form of sugar or glycogen, or some other amyloid substance, or in all these forms. 20 What ts the ultimate fate of Glycogen ? 1. It leads directly to the production of fat—ey., the food of bees is sugary and much fat (wax) is produced. 2. It may also, by its decomposition, assist in the pro- duction of heat. 3. It may also be a source of lactic acid. What ure the forms of Diabetes? 1. Diabetes Insipidus. 2. Diabetes Mellitus. Keplain their meaniny. D1sBETES INSIPIDUS is the persistent discharge of pale urine of /ow specific gravity, containing neither albumen nor sugar. DIAaBETES MELLITUS.—In this condition there is a per- sistent passage of grape sugar in the urine; the urine is large in quantity, pale, and of high specific gravity. What are Pavi’s Experiments in this direction ? He produced diabetes mellitus artificially by sending a stream of arterial blood through the portal vein, and by hyper-oxygenation of the blood in the body generally. The same thing occurs when the portal vein is tied, for then the liver is fed only by arterial blood—from the hepatic artery. What are the possible Causes of Diabetes Mellitus ? 1. Incomplete removal of sugar from the blood of the portal vein at each meal—ie., the liver does not transform it fast enough : the ‘‘glycogenic function” is too slow. 2. From the increased production of sugar by the liver. 21 Give a proof that this Function is affected by the Nervous System. Puncture the floor of the 4th ventricle in a rabbit, between the auditory root of the 7th nerve and the origin of the vagus, diabetes mellitus or diabetes insipidus may result (BERNARD). How ts this Explained ? DiaBETES MELLITUS is probably due to dilatation of the hepatic artery (so that the liver gets a superabundance of arterial blood) resulting from paralysis of the cells in the general vaso-motor centre presiding over that vessel. DiaBeTES iNsipipus probably results from paralysis of the cells in the vaso-motor centre that preside over the renal artery, and so giving rise to hyperemia of the kidney, with the consequent local increase in the blood pressure, the amount of urine passed depending directly upon the blood pressure in the kidney. Give the Course to the Liver of the Nerve Fibres thus concerned, They descend the spinal cord from the 4th ventricle and leave it at the lower part of the cervical and upper part of the dorsal region, pass into the lower cervical and upper dorsal ganglia, and thence through sympathetic to the liver. This is inferred from the fact that destruction of the inferior cervical and upper thoracic ganglia on the right side is followed by diabetes mellitus, probably owing to dilatation of the hepatic vessels. If the Splanchnics are cut, do we get Diabetes Mellitus ? No. Why is this ? Because in this case the general blood pressure is so lowered that the stream through the hepatic artery is not increased. By what other means muy this condition (Diabetes Mellitus ) be produced ? Ly dividing the vagus and stimulating its upper end: also by giving such drugs as nitrite of amyl, chloroform, chloral, ether, morphia, and curara; carbonic oxide poisoning also induces it. What Rapid Change sometimes takes place in Diabetes ? The sugar may suddenly disappear, and fat take its place in the blood and suffocation result, because the oil drops occlude the pulmonary capillaries. Note then the various circumstances that may induce i Diabetes— . Tie portal vein, or , Send arterial blood through it. . Injury to the 4th ventricle. . Stimulation of the upper end of the cut vagus. . Certain drugs. whee OUR What are the Special Features of the Blood in the Hepatic Vein? 1. It is the hottest in the body. 2, Less water than that of the portal vein. 3. Also less fibrin. 4, More glucose than any other vessel. 5. More corpuscles, especially white. 23 Compare more fully the Blood in the Hepatic Vein. The blood, in passing through the liver, Loszs— 1. Albumen. 2. Fibrin. 3. Cholesterine. 4. Blood-colouring matters. 5. Red corpuscles. It cains— 1. Heat. . Urea. . Uric acid. . Glycogen or sugar. OO LS State the Contents of the Lymphatics of the Intestine during Fasting and during Digestion. DURING DIGESTION. DURING FASTING. (Dr REEs)— (Chyle) (Lymph) Water, = - - 2 - - 90°237 96°536 Proteids, including serum-albumen, fibrin, and globulin, - 3886 1:320 Extractives (sugar, urea, leucin, cholesterine), - - - 1565 1559 Fatty matters, - - - - 3601 a trace. Salts, - - - - - O711 0585 100-000 © 100-000 What are the main points of difference ? In the “fatty matters” and ‘“ water.” 24 State what you know of the Movement of the Chyle. 1. It can only flow in one direction, on account of the presence of valves: it flows towards chyle-receptacle. 2. The peristaltic movements of the small intestine, as well as the muscles in the villi, assist greatly in propelling the chyle (see ‘“‘ Movement of Lymph”). What are the Microscopic Characters of Chyle from the Thoracic Duct ? 1. It shows many oil-globules with albuminous envelopes. 2. Lymph corpuscles—nucleated masses of protoplasm. 3. Young red blood corpuscles. As a rule these are not coloured, but when exposed to the air they become pale yellow, and the lymph or chyle as a whole becomes pink. How does the Chyle of the Lymphatics of the Intestine differ From that of the Thoracie Duct ? It is much the same, except for the changes produced in it by passing the mesenteric glands—v.e., it gains 1. Lymph corpuscles. 2. Young red blood corpuscles. LYMPHATIC SYSTEM. Where do the Lymphatics end ? Most of them end in the /eft lymphatic duct. The right duct receives the lymphatics only of the right side of the head and chest, and the right arm. Both ducts open into the respective subclavian veins, just where the internal jugular joins them. 25 Give the Structure of Lymphatic Vessels ? 1. Lancer Lympuatic Vessrirs.—The different coats resemble those of veins, only they are thinner and transparent— (1) Inner coat.—Layers of longitudinal elastic fibres lined by oblong endothelial cells with serrated edges. (2) Middle coat.— Circular non-striped . muscular fibres, mixed with circular elastic fibres. (3) External cout.—White fibrous tissue, and a few longitudinal elastic fibres; also, a few longi- tudinal and oblique non-striped muscular fibres. 2. THoractc Duct.—It is much the same as the above, except that we have— (1) A sub-epithelial layer in the inner coat, as in arteries and veins; and (2) In the middle coat a longitudinal layer of white connective tissue and elastic fibres just internal to the muscular coat. 3. LympH Capiniaries.—These consist of a single layer of endothelial cells with very wavy borders. Have these Vessels Valves ? Capillary lymphatics have no valves; the others have. They resemble the valves of veins, but are more numerous. Just above the valves are swellings, and when they are distended, the vessel has a beaded appearance — like a number of Florence flasks placed end to end. How do Lymphatic Vessels differ from and resemble Veins ? 1. They resemble veins— (1) They pass from the periphery to the centre. (2) They have valves. (3) They are usually divided into superficial and deep sets. 26 2, They differ from veins—- (1) In having glandular enlargements in their course —lymphatic glands. (2) The coats are thinner. (3) They are almost uniform in size, and are usually smaller than veins. (4) Do not as a rule unite to form larger vessels in their course. (5) Convey lymph, not blood. (6) Valves are more numerous, and immediately above them is a sinus: hence, the beaded appearance when distended. Lymphatics do not form a closed system like blood-vessels. What ts meant by “ Peri-vascular Lymphatics” ? Sometimes lymphatic vessels entirely surround blood- vessels; hence, they are called ‘‘PERi-vaAscULAR”—eg., in the brain and spinal cord, lungs, ete. Describe the Oriyin of Lymphatics in Serous Cavities, They begin at ‘‘stomata.” Each “stoma” is surrounded by two or more cells ; these cells are finely granular, cubical in shape, and arranged more or less radiately. They are in direct communication, and indeed placed over an under- lying lymph channel. The cells are called germinal cells, because they proliferate when irritated, and may drop off and assume the form of pus cells. Explain more fully the Effects of Irritation on these Cells. A mild irritation increases their germinal activity without altering their physiological character. A powerful irritation profoundly alters them, giving rise to pathological conditions. Ze How cun these Lymphuties be Injected ? Remove all that part of a rabbit behind the diaphragm, suspend the animal with the concavity of the diaphragm upwards, and pour on a solution of Prussian blue and keep up artificial respiration. The solution then flows into the lymphatics through the stomata; when watched under the microscope little eddies can be seen over the stomata. How do Lymphatics originate in Tissues generally ? 1. The Lacreats in the villi of the intestine is one mode of origin. 2, PLexirorm origin.—Begin in irregular networks which communicate with the cell spaces of the connective tissue corpuscles—e.g., beneath the skin and mucous membrane. 3. Lacunar origin—e.y., in the testicle.-—Begin in shape- less spaces or lacune between the several structures of the gland ; these spaces may be lined by endothelial cells. What are the Causes of the Movement of the Lymph ? 1. It is chiefly due to the force of the heart. 2. Aspiration.—At every inspiration the pressure in the veins at the root of the neck is minus, and therefore the lymph is “sucked” in from the thoracic duct. 3. Extraneous muscular compression. The muscles when they contract squeeze the vessels, and the contents must flow towards the heart, because of the presence and direction of the valves. 4. The pumping action of the muscular fibres in the villi. 5. In many of the lower animals — v.g., frogs and serpents, and in some birds, there are “ lymph-hearts” to propel it. 28 What is the Composition of Lymph ? 1. Parts from the blood. It resembles diluted blood plasma and contains white corpuscles, elements of fibrin, albumen, salts, and water. It contains less proteid matter than blood plasma. 2. Effete matters from the tissues, as creatinin, urea, carbonic acid (53 per cent), and extractives. What Changes occur in passing through Lymph Glands ? Before the lymph passes through lymph glands it shows but little tendency to coagulate; after having passed through, many white corpuscles are added to it, and it then shows a marked tendency to coagulate. Compare Lymph, Chyle, and Blood. Lympu is, broadly speaking, blood mdnus its red corpuscles and slightly diluted. Cuyte is lymph plus a large quantity of minutely sub- divided neutral fat. BLOOD GLANDS. Give a List of these Glands. _ . Red marrow. 2. Lymph-follicular tissue. 3. Solitary glands. 4. Peyer’s glands. 5. Thymus gland. 6. Lymph glands. 7. Spleen ; and some also add 8. The thyroid gland. 9. Pituitary body. 29 What Glands are known more particularly to produce Blood Corpuscles ? 1. Red marrow. Lymph follicular tissue. Solitary glands. . Peyer's glands. . Thymus gland. oO mm oO LY . Lymphatic glands. Describe the Structure of a Lymphatic Gland, There is a capsuLe of fibrous tissue, mixed with non- striped muscle ; the capsule is incomplete at the hilus. It sends in processes to form a supporting framework to the gland. In the cortical part the processes are lamelli-form, but in the mEDULLARY part they break up into cords or flattened bands. In both cases, the alveoli thus formed freely communicate. The cortical part is incomplete at the hilus. In the atvzour we find the proper substance of the gland—“ follicular tissue.” Between the capsule, and sides of the trabeculew is a clear space—the LYMPH SINUS ; the sinus is traversed by retiform tissue, and its boundaries are lined with endothelial cells continuous with the cells lining the lymphatic vessels. The “follicular tissue” (in the central part of the alveoli) is made up of densely packed lymph corpuscles, in process of proliferation, be- tween the meshes of the supporting retiform tissue. The blood-vessels do not pass into the lymph sinus; the lymph corpuscles pass out of the follicular tissue into the lymph sinus by amceboid movement, perhaps assisted by contraction of the gland. The arrERENT VESSELS open into the lymph sinus of the cortical part; the efferent vessels take origin in the medullary part, and pass away at the hilus. 30 Note, then, the different parts— 1. Fibrous capsule and trabeculze. Cortical part. ; Medullary part. Lymph follicular tissue. The lymph sinus. Hilus. Afferent and efferent vessels. STOR So ko How do Lymph Glands differ from other Blood Glands ? In the fact that they have opvious DuoTS. What Changes occur in the Lymph in passing through the Glands ? The out-going lymph contains— 1. Many young red blood corpuscles. 2. Many white or lymph corpuscles ; and therefore 3. It shows a tendency now to coagulate. What 2s the result of too great activity of the Lymph Glands ? We get lymphatic leucocythemia—z.e., a superabundance of white corpuscles. This is to a slight extent the case after every meal. Pigment granules are often entangled in lymphatic glands. Describe the Structure af the Spleen. 1. Ssrous coat.—Incomplete at hilus, and at its reflec- tions on to the stomach and diaphragm. 2. Tunica propria.—Consists of elastic tissue and non- striped muscular tissue. At the hilus it is reflected into 31 the interior over the largest arteries, ensheathing them, and ramifying with them to their finer sub-divisions; it then passes off, and joins the trabecule sent in from the capsule. ? 3, “ INTRA-VASCULAR NETWORK,” or “‘supporting cells” of the pulp. This corresponds to the sinus of the lymphatic glands, only it is filled with blood instead of lymph. In lymph glands, further, the lymph simply flows through the sinus, but in the spleen the blood in its passages undergoes important changes. 4, The pute.—Like grumous blood, it bathes the “sup- porting cells.” There are also yellowish pigment granules, and blood corpuscles are seen in every stage of regressive metamorphosis. Describe the Blood-Vessels of the Spleen. Both arteries and veins are very large compared with the size of the organ supplied. They divide and sub-divide, at first, as blood-vessels do in other organs. The smaller branches of the arteries leave the trabecule, and suddenly end in tufts or pencils of very small vessels. In the smaller arteries the outer coat and sheath becomes transformed into lymphoid tissue, and becomes expanded here and there into what are known as “MaLricHian coRPuscLEs.” In structure these resemble the solitary glands of the intestine. The small arteries end in capillaries, but these do not form a closed system as in other organs. The cells of the capillary wall become branched and connected .with the supporting cells of the pulp, so that the blood flows directly into the spaces of the pulp: the veins take origin in a similar way. The muscular fibres of the spleen have motor nerves belonging to the vaso-motor system. 82 What is the effect of Dividing the Left Splanchnie Nerve ? The spleen dilates just like an artery when the vaso-motor nerve is divided. What is the effect of Stimulating the Distal End of the divided Nerve ? The spleen contracts, again resembling a blood-vessel. What other Conditions or Drugs affect the size of the Spleen ? AspHyxt1a makes it contract spasmodically, just as it does blood-vessels. STRYCHNINE | QUININE all cause it to contract. Ergot or Rye J Evcatyrtus makes it dilate. Digestion also dilates it, just like the blood- vessels of the stomach and pancreas. It also contracts rhythmically once a minute, and the contraction lasts for about half-a-minute. How are these latter best studied ? By means of Roy’s Oncometer. Describe the Curve thus produced. The splenic curve shows undulations due to respiratory movements; the heart’s beats are not seen. This is because the small arteries in the spleen are few, and most of the blood is contained in the capillaries and meshes of the splenic pulp; hence the flow through the spleen is more even than through the kidney, and the effects of variations 33 in pressure from distension of arteries and vaso-motor changes are less felt. The curve also shows rhythmical contractions and dilatation, due to its nervous mechanism. What are the Functions of the Spleen ? 1. It produces blood corpuscles. 2. It destroys red blood corpuscles. Give the Reasons for believing that it produces Blood Corpuscles. 1. When the spleen is enlarged, we get splenic leucocy- themia (Pathological proof). 2. There are more white corpuscles in the blood of the splenic vein than in the splenic artery. Coloured corpuscles are also produced, for the blood of the splenic vein contains young red blood corpuscles; these are not so biconcave, or red, or so large as the ordinary red corpuscles, but when exposed to the air they become coloured (Physiological proof ). What are the Reasons for believing that it destroys Red Blood Corpuscles ? 1. The blood of the splenic veins has fewer old red corpuscles than the blood generally. Some of the pulp cells take the red corpuscles into their interior, break them down, and remove the hemoglobin. 2. The blood of the splenic vein has a red serum, due to the blood pigment liberated by the above mentioned cells. 3. The pulp is very rich in extractives, and other waste products, probably from the breaking down of the red blood corpuscles. ot 34 THYROID BODY. Describe this Gland. It consists of two lateral lobes situated on each side of the trachea and larynx, and joined by an isthmus which crosses in front of the trachea at the level of the third and fourth rings. It weighs from one to two ounces, and is larger in the female than in the male; it often increases in size about the menstrual period. What is tts Structure ? It is surrounded by a very vascular capsule, and consists of a number of closed vesicles; each vesicle is surrounded by a plexus of capillaries, and lined by a single layer of cubical epithelium resting on a basement membrane; each vesicle contains a clear, yellowish, albuminous, viscid fluid, and sometimes white corpuscles and degenerated red corpuscles, What Arteries supply tt ? The superior and inferior thyroid arteries, and sometimes the “thyroidea ima.” What is its Function ? It is not known, though it is included amongst the blood glands. It is concerned in the various forms of goitre. 35 SUPRA-RENALS. Describe their Structure. 1. They have a fibrous coat. 2. On section they are seen to consist of— (1) A cortical part. (2) A medullary part separated from the cortical by a layer of loose connective tissue. Deseribe the Cortical Part. It consists of a fibrous stroma in the meshes of which are cells arranged in columns which radiate from the centre of the gland. The cells are granular, yellow, and nucleated, and contain oil-globules. Small arteries run between the columns. From without inwards, we find— 1. Zona glomerulosa. 2. Zona fasciculata. 3. Zona reticularis. Describe the Medullary Part. It consists of a delicate reticular stroma, in the meshes of which we find granular cells, some of them branched, but they do not contain oil globules. The nerves supplying the supra-renals are exceedingly numerous—from the solar and renal plexuses. What are their Functions. Nothing is known for certain. They are concerned in “« Addison’s disease.” 36 CHEMISTRY OF STRIPED MUSCLE. Deseribe the State of Muscle in Life and in Death. In life the ‘“sarcous substance” is semi-fluid. At death it coagulates and forms clot and serum. This is due to the coagulation of Myosin; it is in this change that “ rigor mortis” consists. Living muscle is alkaline or neutral, but in rigor mortis it becomes intensely acid and much CO, is given off, though there is no consumption of oxygen. How does the Clot differ from Blood Clot ? The clot is not fibrous, but is loose, granular, and gela- tinous; blood in clotting only undergoes a slight change in reaction. What ts “‘ Myosin” ? it belongs to the globulin family, and is therefore not soluble in pure water, but requires about 1 per cent of chloride of sodium to make it soluble. It coagulates at a lower temperature than serum-albumen. Dilute acids, as HCl, change it into syntonin or acid albumen: dilute alkalies change it into alkali-albumen. There is no myosin in Jiving muscle. What is the Composition of the Serum ? It contains water, albumen, and extractives. 37 What is the Cause of the Acidity in Dead Muscle ? It is due to sarco-lactic acid. It is possible that the myosin, sarco-lactic acid, and carbonic acid result from the splitting up of some complex substance. In rigor mortis, although the muscle gives off much carbonic acid, there is no corresponding consumption of oxygen, and, further, muscle contains no free or loosely combined oxygen. The same changes would occur in an atmosphere containing no oxygen. How can Muscle Plasma be obtained ? 1. From dewd muscle: remove all the fat, tendon, etc., and wash in water until the washings contain no trace of proteids. Then treat with a 10 per cent solution of NaCl, which will dissolve a large proportion into a viscid fluid. Filter, and then drop the viscid filtrate little by little into distilled water, when a white flocculent precipitate of myosin will be thrown down. 2. To get the plasma proper from living muscle: freeze and rub up in a mortar with snow and a 1 per cent solution of NaCl, when a fluid will be obtained (the muscle plasma). Filter: at first the fluid is liquid, but slowly coagulates spontaneously : the clot is myosin. How can the Chemical Changes taking place in Muscle be studied ? In four ways— 1. Analysis of muscle at rest and after prolonged contraction. 2. Analysis of blood entering and leaving the muscle during contraction. 38 3. Analysis of the excreta, especially from the lungs and kidneys during rest and exercise. 4. The kind of food best adapted for muscular work. Which of the above has yielded the best results ? The third method. What is the chief product of Proteid Metabolism ? Urea is the great azotised derivative of proteid meta- bolism. On what does the Amount Exereted depend ? 1. On the amount of proteids in the food. 2. On the amount of tissue metabolism. When Proteids are left out of Food, what is the result ? The urea excretion greatly falls, but still continues, because it is produced by proteid waste continually going on. More work done, more food is required, and more urea excreted. What is necessary before we can prove that muscular work, PER SE, produces increased Excretion of Urea? It is necessary either— 1. To omit proteids from the food both before and during muscular work ; or 2. To keep their amount in the food constant. 39 Give a Short Account of the Experiments of Fick and Wislicenus. They omitted proteids from their diet, before, during, and for some hours after the performance of severe mechani- cal work, done in ascending a mountain. They estimated the total amount of nitrogen excreted by the kidneys before, during, and after the work, and found that it was not increased. What was Parkes’ Experiment ? He made experiments similar to the above on soldiers doing mechanical work on a non-azotised diet. He esti- mated the total nitrogen excreted in the urine and faces, and found that it was not increased by mechanical work. Describe Pettenkofer and Voit’s Experiments. They made experiments on a man placed on a fixed diet containing the normal amount of proteids. This was done in a large “respiratory chamber.” They found that mechani- cal work does not affect the excretion of urea, but greatly increases the excretion of carbonic acid. What did they infer from these Fucts ? That muscular energy springs from the metabolism of carbo-hydrates or fats, or both, but not from proteids. What takes place in a Muscle during Contraction ? It respires more rapidly: the excretion of CO, is more rapid, and there is a greater amount of oxygen consumed. The glycogen in the muscle disappears and probably gives origin to muscular energy. Sarco-lactic acid is produced. 40 What Food is best fitted for Muscular work ? Food in which muscle itself enters largely—i.e., proteid. Great exhaustion usually ensues in most persons if they attempt to do severe muscular work on a diet that does not contain proteids in some form—though many labourers can do severe work day after day on a diet consisting of oatmeal, milk, and bread. CHEMISTRY OF NERVE TISSUE. Give the Composition of Grey and White Nerve Matter. GREY, WHITE. Water, - - - 816 684 Solids, < - - 184 31:6 100-0 100-0 In 100 parts of the solids. GREY. WHITE. Albumen and gelatine - 554 24°8 Lecithin, - - - 17-2 9-9 Cerebrin, - - - 0-5 9-5 Cholesterine and fats, — - 18-7 51:9 Extractives, - - - 67 3°3 Salts, - - - 7 15 0-6 100-0 100-0 Grey matter has more albumen, lecithin, and lactic acid (this giving it its acid reaction) ; less cholesterine, fat, and cerebrin than the white matter. or neutral. White matter is alkaline 41 What is Lecithin ? It is a nitrogenised and phosphorised fatty body, and consists of C. H. O. N. and P.. It is a white crystalline substance, soluble in hot alcohol and ether. What takes place when it is Boiled with Acids ? It takes up water and splits into glycero-phosphorie acid, stearic acid, and neurin. What Change do we find in the Urine in waste of Nerve Tissue ? There is an increase of phosphates in the urine in wasting diseases of the nervous system. The phosphorus probably comes from the decomposition of lecithin. The chemical changes taking place in nerve tissue are, however, but little known. Give the Conditions affecting the Nutrition of Tissues. 1. BLoop suppLY— (1) Cut off the supply suddenly, the part dies by GANGRENE, or fatty degeneration. (2) Slowly cut off, while the tissues get plenty of oxygen, ATROPHY results. (3) Increase the supply, we find increased growth under certain conditions. Cut the sym- pathetic in the neck of a young rabbit, that side grows faster than the other (as the hair, ear, etc.). If the animal be old this will not take place; probably because the trophic energy is deficient. 42 2. THE CONDITION OF THE BLOOD— (1) Deficiency of certain constituents —eg., FAT, emaciation results: ALBUMEN, weakness and a tendency to inflammatory conditions re- sult: tron, deficiency of coloured corpuscles : VEGETABLE SALTS, scorbutus results. (2) Excess of certain constituents—e.g., IRON, dilata- tion and disease of blood-vessels: PHOSPHORUS, fatty degeneration and waste of nerve tissue: WATER, proteid matters break down more rapidly, and more urea excreted: Fat, adi- posity. (3) Introduction of poisons, as syphilis, small-pox, eruptive fevers, etc. 3. THE MOLECULAR CONDITION OF THE TISSUE ITSELF.— Assimilation is due to trophic energy of tissues; tissues reproduce their like, and unless healthy they cannot reproduce healthy tissues. They must have a_ vital capacity for assimilation and growth — self-maintenance and self-repair. 4, INFLUENCE OF THE NERVOUS SYSTEM. What Conditions affect the Trophic Energy ? 1. Gentle heat increases. 2. Mechanical stimuli also increase—e.g., drive a seton through articular cartilage: the cells proliferate rapidly. Hard work hardens the hands. Irritate the peritoneum, the germinal cells around the stomata proliferate. 3. Functional activity, if within moderate limits, in- creases—e.g., the blacksmith’s arm. Excessive activity leads to pathological conditions—e.g., in cartilage, when the proliferating cells come to resemble pus cells. 43 What Considerations oppose the idea of Trophic Nerves? There are no nerves in vegetable tissues, cartilage (1), tissues of the embryo, and yet these tissues are all well nourished, How does the Nervous System affect the Nutrition of Tissues ? It may be by— 1. Paralysis. 2. Irritation of nerves. State what you know of the Results of Paralysis of Nerves on Nutrition. 1. Division of sciatic nerve in an adult mammal is followed by atrophy of the limb. The muscles lose their contractility and undergo fatty degeneration: the skin atrophies and becomes thin and glossy: bones may lose their lime salts and become soft. These effects are said to be due to loss of trophic influence. The formation of acute bed sores in cases of accidental division of the spinal cord, and consequent paralysis of the legs, supports the “ trophic ” theory. Against it we have the fact that the lower part of the spinal cord may be removed from kittens and yet the hind legs continue to grow; but this may be because the ganglia or posterior roots are not destroyed. 2. When both vagi are divided in the neck, death always results, the lungs becoming congested and the air vesicles and bronchi filled with frothy serum. These results are said to be due to the loss of “trophic” influence, but it is probably due to the entrance of foreign matter through the paralysed glottis. Division of one vagus is not followed by trophic changes in the lungs, because the entrance to- 44 the larynx is still closed during deglutition, if one vagus be intact. 3. When the ophthalmic branch of the 5th nerve is divided in the rabbit, there is paralysis of common sensi- bility in the eye and its appendages, and inflammation with destruction of the eyeball may ensue. This is probably due to the entrance of foreign particles, as proved by stitching a piece of leather in front of the paralysed eye when inflammation does not ensue. 4. Cut all the nerves supplying a gland, we get “paralytic secretion,” and degeneration of the cells of the gland. State what you know of the Effect of Nerve Irritation on Tissue Nutrition. Stimulation of the Gasserian ganglion produces hyper- zesthesia of the nerves of the face, eye, nose, and mouth; it may even lead to ulceration of the parts. Samuel said this was due to irritation of the trophic nerves, causing nutritive excitement in the tissues: Charcot and others, that it was due to inflammation extending along the sheath of the nerve to the parts in question. Partial division of the ophthalmic branch of the 5th is sometimes followed by inflammation of the eye, even though there is no paralysis of sensibility: Charcot said this was due to inflammation extending along the nerve sheath to the tissues of the eye. Herpes zoster is supposed to be an example of the same thing—inflammation extending along the nerve to the tissues at the periphery. Samuel ascribed it to irritation of the trophic fibres. The changes in muscle taking place after division of its nerves seems to support the “trophic” theory, though the question is still an open one. 45 EXCRETION. How may Effete Substances leave the Blood ? By the— 1. Kidneys. 2. Skin. 3. Lungs. 4. Liver. THE KIDNEYS. What kind of a Gland ts the Kidney ? It is a compound tubular gland. What is its General Structure ? It has a thin fibrous capsule, but loosely adherent to the kidney substance. On section it shows— 1. A cortical portion. 2. A medullary portion. What is the Structure of the Medullary portion ? It consists of a number of pyramids— the pyramids of Malpighi. These pyramids are separated by cortical substance, 46 What are the Columns of Bertini ? The cortical portion sent down between the pyramids. The cortical portion is incomplete at the hilus; the medullary portion is denser, and striated from the presence of tubules. What are the Medullary Rays? They are bundles of straight tubes that extend into the cortical portion of the kidneys, continuous with the straight tubes in the medullary part. What are the different divisions of the Cortical and Medullary portions ? The corticaL portion is divided into— 1, Subcapsular stratum. 2. The cortex proper. 3. The inner stratum of cortex. The MEDULLARY portion is divided into— 1. The boundary layer with its well-marked striations due to the vasa-recta, and bundles of straight tubes. 2. The papillary layer: this is of a uniform dull red colour. Describe the Course of one of the Tubuli Uriniferi. l. They begin in the cortex in an expansion called Bowmay’s capsuLe; into this is pushed a tuft of blood- vessels, invaginating one side of the capsule. This tuft is 47 called the GLomeruLUS or MaLpricHIAN corPuscLE. These are only found in the cortical portion of the kidney. In structure they consist of a basement membrane, and a single layer of squamous epithelium. 2, The neck of the tubule.—Strweture as above. 3. PROXIMAL CONVOLUTED TUBULE.—Ends at inner border of cortex. Straucture—Lined with short columnar cells; some- times irregular in shape, with clefts between. 4. SPIRAL TUBULE OF ScHAcHOWA passes down in a spiral manner, and is of the same size and structure as the last. This leads to the 5. Descenpine timp of Henue’s Loop in the boundary layer of the Malpighian pyramid ; then 6. The Loop itself in the papillary layer; and then 7. The thick part of the asceNDING LIMB OF HENLE’s Loop: this part is wider than the other parts of the Loorzp TUBULE of Henin. Structure—The narrow part resembles a capillary—basement membrane, and a layer of squamous epithelium with large nuclei projecting into the lumen, giving rise to a spiral appearance. The broad part is lined with imbricated epithelium. 8. About midway in the boundary layer the ascending limb narrows again, forming the ASCENDING SPIRAL OF Henue’s Loop. The tube now re-enters the cortex, and forms 9. The narrow ascending limb in the medullary rays. Structure—Lined with cells more or less flattened, but both in this, as in (8), the cells are in places angular, branched, and imbricated. This joins the 10. IRREGULAR TUBULE, which has a very irregular and angular outline, and is lined with angular and imbricated cells, with exceedingly well-marked striz. 48 ll. The tube next becomes convoluted, forming the DISTAL CONVOLUTED TUBE, or “intercalated section of Schweigger-Seidel. Structwre — Resembles the proximal convoluted tube. 12. CURVED COLLECTING TUBULE, opening at right angles into the 13. STRAIGHT COLLECTING TUBULE.—In both cases lined with cubical or columnar epithelium. It passes down through the Malpighian pyramid, joins with others to form larger tubes, and finally opens at the apex of the papilla as the 14. Ductus papituaris.—The collecting tubes are lined with transparent nucleated columnar or cubical cells, What are the Secreting Parts of the Tubule ? . The glomeruli. . Proximal convoluted tube. . Spiral tube. Broad part of Henle’s loop. . Distal convoluted tube. oa RP wp o What are the “ Pyramids of Ferrein” ? They are groups of straight or collecting tubules in the cortical part of the kidney. The tubes in the centre of the group are the longest, and reach almost to the surface of the kidney—while the external ones are shorter—thus forming a pyramidal-shaped group, with its base to the base of the Malpighian pyramids. Several such groups (“pyramids of Ferrein”) may correspond to a single Malpighian pyramid. 49 Describe the Blood Supply of the Kidney. The renal artery on entering the kidney breaks up into numerous primary branches, which pass up between the Malpighian pyramids in the columns of Bertini, and are called the arteriw propric renales. At the bases of the pyramids they form incomplete arches, and from these are given off— 1. InreRLOBULAR ARTERIES.—These arise at right angles, and run up between the pyramids of Ferrein, and give off the afferent vessels of the Malpighian tufts. 2. Branches passing downwards into the pyramids, running between the bundles of collecting tubes, and called the vasa-recta or arteric- rectee, Describe the Vessels of the Tuft. Before the afferent vessel enters there is a dilatation ; when it enters the capsule it breaks up into capillaries round the periphery, and from the centre part of the capillaries the efferent vessel arises. After leaving the capsule the efferent vessel again breaks up into capillaries, which form a close network around the convoluted tubules, and also to a certain extent around the straight tubes. What ts peculiar about the above ? The blood has to pass through Two sets of capillaries. pt 50 What other Vessel is the Efferent Vessel of the Tuft said to Resemble ? The portal vein of the liver, as it also begins in capillaries, and breaks up again into capillaries. Describe the Veins of the Kidney. They arise from three sources— 1. The INTERLOBULAR VEINS correspond with the arteries, and into these the STELLATE VEINS beneath the capsule open. 2. The vENH RECT® run along the pyramids with the corresponding arteries. 3. The VENEZ PROPRIZ RENALES pass along the columus of Bertini, after having been joined by the venz interlobulares and venz rectz. Describe the Ureter and Pelvis of Kidney. At the hilus the ureter dilates into the “pelvis,” this divides into two or three primary divisions, and these end in a larger number of calices into which the apices of the Malpighian pyramids are pushed. The mucous membrane being reflected over them. The ureter has three coats— 1. External or fibrous. 2. Muscular, two layers—longitudinal and circular. 3. Mucous coat, lined with stratified transitional epithelium. 51 What are the Constituents of the Urine ? 1. It consists of 95 per cent of warErR ; and 2. Azotised organic matters, as urea, uric and hippuric acids, creatinin and creatin. 3. Non-azotised organic matters, as traces of sugar, oxalic and lactic acids. 4. Pigments. 5. Mineral matters. Most of the constituents are in the blood, and probably the chief function of the kidney is to remove them. What are the Characters of the Urine ? It is a clear yellow fluid, of specific gravity 1020, of peculiar odour and acid reaction. The daily amount is 52 ounces, but this varies— 1, With the amount of water in the food. 2. The amount of excretion by the skin. The solids excreted are about 2} ounces daily, but this varies— 1. With the kind of food eaten—e.y., proteid food increases. 2, With variations in tissue metabolism. How does its Reaction vary ? It is usually acid, due to the presence of acid sodium phosphate, as there is no free acid. During digestion it may become neutral or slightly alkaline. 52 Why is this? 1. It may be due to the liberation of alkali into the blood during digestion, as a result of the secretion of gastric juice. 2. Absorption of alkaline phosphates from the food; this is specially marked in a vegetable diet: in this case the acidity is much diminished. In HERBIVOROUS animals it is always alkaline. In carnivorous animals it is very acid. What are the Relations of Urea? It is related both to carbonic acid and ammonia. It is regarded as the diamide of carbonic acid; thus carbonic acid may be written in the hydrated (hypothetical) form— co<0 Replace the hydroxyl groups by ammidogen (NH.,), and we have urea— NH CONG? “=i, Urea is further isomeric with ammonium cyanate. How much Ureu is Excreted in Twenty-four Hours ? About 500 grains; it forms rather more than one-half the total solids. It is the great azotised derivative of proteids and their allies, the lowest term as it were to which it is possible to reduce them. What are its Sources ? ~ 1. Tissue metabolism. 2. Proteid matters of the food. How does Food affect its Exevetion ? Mixed diet, - = - 500 grains daily. Animal diet, - : - 821 " Vegetable diet, - - - 847 " Non-azotised diet, - - 237 " Excess of water, common salt, increase its excretion, because these help to break down proteids. It is increased in diabetes mellitus, chiefly because of the large amount of animal food taken. It is increased in fever and inflammatory affections, because of the increase in tissue metabolism. How does the State of the Liver affect its Excretion 2 Although urea is probably formed to a certain extent in most tissues, yet the hepatic cells are the great seat of its formation ; because, if the liver be washed free from blood, more urea will be found in its cells than in any other tissue. Also, in acute yellow atrophy of the liver, the urea is im- mensely diminished in the urine; but instead of it we find abundant deposits of leucin and tyrosin, and probably these substances are its antecedents. No more urea is formed in the kidney than in any other tissue. What is Leucin ? It is ammido-caproic acid, and is probably transformed into urea in the liver. If it be injected into-the alimentary 54 canal, the amount of urea is increased directly in proportion to the quantity of leucin injected ; but as there is only one (NH,) in its composition there must be synthesis as well as decomposition, as there are two in urea. Ts it the same with Tyrosin ? No; when it is injected into the alimentary canal there is no increase in the amount of urea excreted, though it also is an ammido-acid, What is known about Urie Acid ? Tt is usually combined with potassium and sodium; the urates thus formed are very soluble in hot water, and as the urine cools, they are thrown down as the “ brick-dust” deposit, especially if the urine be concentrated by eva- poration from the skin (sweat), as after a brisk walk, ete. About 10 grains daily is excreted ; in Herbivora very little is found. Xanthin and Hypoxanthin are probably the antecedents of Uric Acid—thus Hypoxanthin = C;H,N,O Xanthin = CLAN, Os Uric Acid = C.F N Os When oxidised it splits up into urea and mes-oxalic acid: this change takes place in the body—e.g., when uric acid is injected into the alimentary canal, more urea and more oxalic acid are excreted by the kidney, State the Conditions that Inerease or Diminish Urie Acid in the Blood. It is INCREASED in— 1. Ague and gout. 2, Enlarged spleen. 3. Flesh diet. It is Diminisoep by— 1. Quinine. Caffeine. . Potassium iodide. . Sodium sulphate. . Sodium chloride. . Vegetable diet. . Excess of water. AMO wr State what you know of Creatin and Creatinin. Fifteen grains daily of each are excreted. CrREATIN is increased by flesh diet, but it also comes from tissue metabolism. CreaTInIn is creatin minus H,O, and may be got by boiling creatin. What do you know of Hippuric Acid ? It is not found in Carnivora, but much is found in Herbivora, especially the horse (hence its name), In human urine the amount is small; but vegetable diet increases it. — It is supposed to be derived from a substance resembling benzoic acid in the cuticular parts of plants. Give benzoic acid, it is much increased ; benzoic acid unites with glycocin to form hippuric acid. vu What are the Pigments of the Urine ? 1. The chief is UROCHROME. 2. Urosiin (hydro-bilirubin)—probably absorbed from the alimentary canal. 3. Inpican—a blue pigment; much found in dog’s urine. What is the Test for Indican ? Boil urine with + volume of hydrochloric acid, to which a little nitric acid has been added, and a violet colour is produced. What ts the Origin of the Mucus found in the Urine ? It is secreted by the urinary passages, and not by the kidney. What are the Chief Salts of the Urine ? CHLORIDE oF Sopium and CuHLorIDE oF Potassium.— These come from the corresponding salts of the food, and but slightly from tissue metabolism. Puospuates (ortho-phosphates) from the food, and also from tissue metabolism, especially nerve tissue—e.g., from lecithin, from the oxidation of its phosphorus. They are increased in overactivity and disease of the nervous system. SunpHatTes—chiefly from the salts of the food; a little from tissue metabolism—e.g., oxidation of the sulphur of albumen. of What is the Effect of Excising one or both Kidneys ? Excise one, no harm results, provided the other one be sound. Excise both, and death follows very speedily : and the same result follows if both ureters are tied—coma, convulsions, and death from uremia. What is the Cause of Urwmia? It is not definitely known; may be due to the accumula- tion of urea, potassium, or water in the blood. How does the Blood in the Renal Vein differ from ordinary Venous Blood ? It is not the colour of venous blood, but is bright red ; this is because the kidney is small, and the quantity of blood sent to it so great. All the blood in the body passes through the kidneys about six times every hour. The blood in the renal vein is therefore the purest in the body, because it is purified arterial blood. What information is gained, relating to the Circulation in the Kidney, with Roy’s Oncometer ? The curve produced almost resembles the blood pressure curve ; variations due to the heart’s beat, and to the respiration, are both seen. This is probably because of the number of small arteries in the kidney, and the large amount of blood contained in them; hence, the pressure changes are very easily felt. What parts are concerned in the Secretion of Urine? The glomeruli, the epithelium of the convoluted tubes proximal and distal, and probably the broad part of Henle’s loop. 58 What is Bowman’s Theory ? That it is a double process, partly mechanical, and partly vital— 1. The mzcHanican part is the filtration of fluid through the capillaries of the glomeruli. 9. The virat part is the excretion of the solids by the vital activity of the protoplasm of the epithelial cells lining the above mentioned tubules. Give some Reasons for this latter Belief. 1. The anatomical relations and position of the glomeruli. 2. Crystals of uric acid are often found in the epithelium of the convoluted tubules of the kidneys of birds, and in the newly-born child. 3. In “Bright’s disease,” the renal epithelium is de- stroyed, and the excretion of solids in the urine is much diminished. What is the action of the Glomerult ? The water filters through the capillaries, holding in solution a small amount of mineral matters. How is their action affected by the Blood Pressure ? It varies directly with the blood pressure: the higher the pressure, the more urine filters through. The pressure in the glomeruli is naturally higher than that in the capillaries in the other parts of the body, because the blood 59 has to pass through two sets of capillaries. The presswre varies according to the contraction or relaxation of the renal arteries; if relaxed, there is a local increase of pressure, and therefore more urine filters through: when constricted, the opposite obtains. What is the effect of Cutting the Renal Nerves ? The secretion of urine is increased, but there is no increase in the solids; the arterioles are dilated, and there is an increase of pressure, and more urine filters through. What is the effect of Lesions in the Medulla? Puncture the floor of the 4th ventricle, there is increased filtration of urine (see page 21). What is the effect of General Vaso-motor Paralysis ? In this case—from section of the spinal cord below the medulla—the filtration of urine stops, because the blood pressure in the glomeruli: is lowered too much: this being the case, there is a general fall of pressure, instead of a local increase. Cut the renal nerves first, there is increased filtration of urine: then cut the spinal cord in the neck, the secretion almost stops. Stimulate the lower end of the divided cord, there is a great secretion of urine, because there is a great increase in the blood pressure both generally and locally. In this latter case, if the renal nerves are intact, there would be little or no urine, because the renal arteries would be too much constricted for the blood to get through. 60 How do Emotions affect the Secretion ? In many emotional states, such as hysteria, fear, ete.— probably due to flushings of the blood-vessels of the kidney by direct action on the renal nerves, or to contraction of the peripheral capillaries (in the skin, etc.),—there is no increase in the solids. How does the state of the Skin affect it ? If the skin be warm, then the secretion is less, because the dilated vessels on the surface lowers the pressure in internal organs, and therefore there is less filtration through the glomeruli. Cold has the reverse effect: surface capil- laries are constricted, and the pressure in internal organs raised. What is the effect of Injecting Water into the Blood ? Even though there be no change in the blood pressure, yet there is an increased flow of watery urine. Why ts this ? It is not known. How is it that Albumen sometimes passes through the Capillaries of the Glomeruli ? When the blood pressure is normal no albumen filters through, probably because the molecules are too large: but raise the blood pressure sufficiently, then albumen will pass hrough, and even blood corpuscles. Yet, egg-albumen 61 or a solution of liberated hemoglobin, if injected into the blood, will be excreted by the kidney under ordinary conditions of blood pressure. This may be done by the epithelium of the convoluted tubes as a “vital” process, and not by mere filtration. What are Heidenham’s Experiments in regard to the action of the Renal Epithelium ? He showed that most of the solids of the urine are excreted by the epithelium of the proximal and distal convoluted tubules; the broad part of Henle’s loop being doubtful. : 1. Inject indigo-carmine into the jugular vein of a rabbit, and kill the animal after one hour, and harden the kidneys in alcohol, and examine. The tubules are filled with pigment, excreted by the epithelium of the convoluted tubes (not glomeruli), and washed down by the water filtering through the glomeruli. That is what takes place when both tubules and glomeruli are secreting. 2. When the tubules are secreting, and the glomeruli are not.—Cut the spinal cord in the neck, this stops all filtra- tion. Inject carmine as above, and examine the kidney : the medullary part is colourless, but the cortical part is deeply stained. The blue has been moved through the epithelium of the convoluted tubes, but has not been washed down. No blue pigment is found in the glomeruli. Had the broad part of Henle’s loop been secreting, there should have been some blue streaks in the medullary part. What is the Pressure of the ordinary Secretion ? About jth of the blood pressure. 62 Describe the passage of the Urine to the Bladder. It is forced down the ureter by the peristaltic contraction of the circular layer of the muscular coat; though the middle third of the ureter has no nerves, yet the fibres are organically connected, and the wave passes from fibre to fibre. The ureter perforates the wall of the bladder very obliquely, and this acts as a valve and prevents reflux. What are the Coats of the Bladder ? 1. SzRovs coat—only partial. 2, Muscutar coat—three layers— (1) External longitudinal (detrusor urine). (2) Middle or circular; part of this forms the sphincter vesicce, (3) Internal longitudinal, 3. SuBmucous coat—marked everywhere, except at the trigone. 4, Mucous coat—loosely connected and often wrinkled, except at the trigone, where it adheres directly to the mus- cular coat. It is lined by stratified columnar epithelium— stratified probably to prevent the absorption of urine. How is the Urine retained in the Bladder ? By the contraction of the sphincter, due to the automatic activity of the centre in the lumbar part of the spinal cord. Who proved that the Centre was there ? Goltz, by experiments on dogs. 63 Describe the Mechanism of the act of Alvcturition. Bladder full, and a desire is felt to make water. Micturition itself is a reflex act, but one which is more or less under the control of the will. There are probably two centres concerned, in the lumbar part of the cord— 1. For the sphincter—automatic. 2. Centre—which when stimulated, excites contraction in the detrusor urine. When the bladder becomes distended, there is an efferent impulse sent from the mucous membrane of the bladder, that reaches both the lumbar centres and the brain. This leads to— 1. Voluntary inhibition of the sphincter centre ; and 2. Stimulation of the detrusor centre. The contractions of the detrusor are assisted by the contraction of the muscles of the abdominal wall, which thus press upon the full bladder, and the water is forced through the urethra—its passage being assisted by the contractions of the accelerator urine. If the spinal cord be cut or diseased, micturition may become purely reflex, being managed entirely by the centres in the lumbar region of the cord without any help from the brain. Sometimes the sphincter centre is paralysed, and the urine trickles away. Edinburgh : Printed by E. & 8S. Livineastonn, 4 Melbourne Place. a he el an CATECHISM SERIES. C/ /? of ie PHYSLOLOGY:, . \ Ao 4 nae PART VI. THE SKIN—ANIMAL HEAT—VOICE AND SPEECH—SMELL—TASTE. 7 EDINBURGH: Bowe 3. wiviInNGs TONE. PRINTED BY E. & 8, LIVINGSTONE 4 MELBOURNE PLACE EDINBURGH. {_ LIBRARY Vz aH VPs t \y AY PHYSLOUOGY. “== PART VI. THE SKIN. What are the Layers of the Skin? 1. The epidermis or cuticle. 2. The dermis, corium, or cutis vera. What are the Appendages of the Skin ? Sweat glands, nails, hairs, and sebaceous glands. Describe the Epidermis. It consists of— 1. A horny layer: hard flattened scales, usually without nuclei, insoluble in acetic acid, but swell up and become soft in caustic potash. At the lower part there is a clear homogenous layer, known as the 2. Stratum lucidum. Below this we find 3. The rete mucosum or rete Malpighii. The cells are of irregular shape—the deeper are elongated and placed endwise, the middle ones are more or less rounded, while the upper ones are more or less flattened, the long diameter being parallel with the surface. At the upper part of the “yvete” is a thin layer, that stains very readily with picro- carmine, and is known as the 4, Layer of Langerhans. 4 Why was this Layer named Rete Mucosum ? Because of its net-like arrangement, and because it was thought to yield mucin. Note then— The horny layer, with its stratum lueidum. The rete mucoswm, with its layer of Langerhans, What ts found at the very lowest part of the Cuticle ? The “spinous” or “prickle cells” of Schultze. The cells have a denticulate appearance, the apparent spines being continuous at their apices, and not interlocked as Schultze maintained. When stained with osmic acid, the spaces and prickles are best seen. The spaces are probably lymph channels through which the lymph percolates. What are the Parts of the Dermis or True Skin ? It is composed of — 1. A PAPILLARY LAYER.—This consists of a tough strong framework of connective tissue raised into papille. The papille may be simple or compound, and vascular or nervous. In the nerve papille are the end organs of the sense of touch; in the vascular papillz are found blood- vessels and lymphatics. 2. The RETICULAR LAYER.— Here the connective tissue is loose, and in its meshes are hair follicles, sweat glands, and masses of fat. What is the Cause of the Ridges and Furrows on the Hand? They are caused by rows of papille: at the top of the tidges we find the openings of the sweat glands. The papillee are most numerous where the sense of touch is most acute. 5 Describe the Blood-Vessels and Lymphaties. The blood-vessels are very numerous, and form plexuses round the fat cells, sweat glands, and hair follicles. They everywhere divide and anastomose, and form a fine net- work, and send minute branches into some papillae. The lymphatics are also numerous, and form a network just beneath the blood capillaries, and communicate with larger vessels. Describe the Nerves of the Shin? Many of the papille are seen to contain well-marked nerves and “end organs.” There is also a superficial plexus immediately beneath the epithelium, and this sends minute non-medullated varicose nerve fibrils upwards, to end in knob-like swellings. What are the various “ End Organs”? 1. End-bulbs—e.g., in the glans penis, and red borders of the lips. 2. Pacinian bodies, in the subcutaneous tissue, on plantar and palmar nerves. 3. Tactile corpuscles in the papille of the skin where touch is most acute. Describe the Nuits. The nail consists of a Root and Bopy. The root is that part which is covered by the skin; the body, the uncovered part, which ends at the free edge. The whitish portion, near the root, is the Zunula—this appearance being due to opacity of the substance of the nail at this point, and also because the part beneath is less vascular. 6 What is the Structure of the Natls. The nail closely resembles the epidermis, and is in fact a modification of that structure. The Harp and Dry part. corresponds to the horny layer of the skin (or more probably to the stratum lucidum), the Matrix or nail-bed to the rete Malpighii. The matrix is very vascular, and the papille are large and numerous. At the root and sides, it is con- tinuous with the cuticle. Posteriorly, the nail fits into a groove, like the rim of a watch-glass. At the Lununa the papille are irregular : in front of this they are in longitudinal rows; hence the grooves or lines on the nails, corresponding to the ridges on the skin. How does a Nail grow ? By constant generation of cells at the root and under surface, and each series is followed by others, and are thus. pushed forwards and become flat and horny, hard and dry. Describe a Hair. It consists of— 1. The Stem.—This is cylindrical, and is made up of a cuTicLe of finely imbricated scales; a corTEX, translucent with longitudinal streaks; and a pirH (not always present), formed by little clusters of angular cells with pigment granules and spaces between the cells. 2. The Root.—This is softer than the stem, and swells out below into a root-bulb resting on a papilla. The bulb. consists of soft growing cells; the papilla is very vascular, and it is here the cells proliferate during the growth of the hair, The hair is lodged in a recess of the skin, called - the hair follicle; the follicle receives the ducts of the sebaceous glands. Hairs are not found on the palms of the hands, soles of the feet, upper eyelids, nor ungual phalanges, What are the Coverings of that part of the Hair in the Follicle ? 1. Dermic coverings, continuous with the DERMA or CUTIS VERA— (1) Longitudinal fibrous layer. (2) Transverse fibrous layer. (3) Hyaline layer, transparent, homogenous, with transverse markings. 2. Epidermic coverings, continuous with the cuTicLE— (1) Outer root sheath, being a continuation of the rete Malpighii or mucosum. (2) Inner root sheath, corresponding to the horny layer of the skin, and has the following layers— (a) Henle’s layer. (b) Huxley’s layer. (c) Cuticle of the root sheath; a single layer of imbricated columnar cells. They are imbricated from below upwards. What is the Cause of Hairs turning Grey ? The grey colour is due to air bubbles in the interstitial matter of the cortex. 8 Describe the Sebaceous Glands, These glands open into the hair follicle, usually two into each follicle. They are compound racemose glands, and are lodged in the substance of the true skin. They are very large in the region of the nose, and often contain a parasite—the “ demodex folliculorum.” The secretion consists of epithelial cells that have undergone fatty degeneration — the protoplasm being changed into fatty matter. The secretion lubricates the surface of the hair, and prevents it falling to pieces. How are the Hairs planted in the Skin ? They are planted obliquely. What do we find on the Sloping Side ? A small bundle of non-striped muscular tissue. The fibres arise from the cuTIS vpRA, and are inserted into the outside of the follicle below the sebaceous gland. What is the result of their Contraction ? The hair is straightened. Cold, electricity, or fear may cause them to contract, and produce the ‘ cutis anserina,” or ‘ goose-skin,” What is the Nature of the Sweat Glands ? Simple tubular glands, very much coiled at the lower part, situated in the cutis vera. ‘The true eLanp is the lower two-thirds of the coiled up part. 9 Give the Structure and Arrangement. In the cutictr the duct is corkscrew-like, and has no special wall, simply the flattened surfaces of the general epidermal cells. . In the cutis vera the duct is not tortuous, and consists of a basement membrane, and inside that two or three layers of cubical epithelial cells; while inside that again is a delicate homogenous membrane: this is the structure of the straight part and upper 4 of coil. The lower # of coil, the gland proper, consists of from within outwards— 1. Columnar epithelium, with linear striations. 2. Layer of non-striped muscle. 3. Basement membrane. Contrast this with the structure of the puct— 1. Transparent homogenous membrane. 2. Two or three layers of cubical cells. 3. Basement membrane. (tive the General Facts of the Development of the Skin, and its Appendages. The cuTis vera, with its nervous and vascular structures, are derived from the MESOBLAST. The EpipErmMis, hair follicles, sebaceous and sweat glands, are derived from the BPIBLAST. What are the Functions of the Skin ? 1. Protective to the delicate structures beneath. An organ of the tactile sense. Excretory apparatus. A regulator of temperature. It may also absorb certain substances, though in man this power is slight. Ps Go ke 10 What is the Composition of the Sebaceous Secretion ? It is an acid secretion and consists of fatty matters and fatty acids. The skin of the foetus has a thick coating of this substance—the “ vernix caseosa.” It consists of saponified fats, cholesterine, epidermic cells, stearin, caproic, butyric, and other acids. What is tts Function 2 It helps to prevent the hair from falling to pieces by its agelutinating character, and makes the hairs and skin soft and flexible; it protects the skin from water and cold, prevents too free evaporation, and thus renders it a more effectual organ of defence and protection. How may Sweat be obtained Pure ? From the palm of the hand or the sole of the foot, as there are no sebaceous glands in these parts. To get sweat in quantity, wash the arm and then place it in a caoutchouc bag. What are the different kinds of Perspiration ? 1. Inszensiste.—This passes away at once in vapour, and is always taking place. 2. SensiBLe.—This part remains on the skin and forms visible drops of fluid. What are the Characters of the Perspiration ? It is a clear acid, colourless fluid, with a peculiar odour. It contains nearly 2 per cent. of solids: its specific gravity 11 is 1004. It is usually more or less mixed with the sebaceous secretion, and contains— J. Salts (sodium and potassium chlorides). 2. Fatty acids (acetic, formic, butyric, ete.) 3. Fats, and cholesterine. 4, Nitrogenous bodies (as ammonia, urea, etc.) What abnormal Constituents may tt contain ? It may contain uric acid, bile pigments, grape sugar, or albumen, What amount is Secreted daily ? One to two pints or more in twenty-four hours; but the amount is affected by many circumstances, as temperature of the surrounding atmosphere, temperature of the body, nature and quantity of food and drink taken, exercise, etc. What Nerves are concerned in its Secretion ? Two sets ; in this respect resembling the salivary glands— 1. Vaso-inhibitory to dilate the vessels. 2. Secretory nerve proper. How can this be shown ? Cut the sciatic nerve of a cat or a dog, and stimulate the lower end, we find— 1. Vascular dilatation of vessels. 2. Secretion of sweat. 12 What /s the Effect of Atropine ? Give an animal atropine, and then perform the above experiment, we only find — Vascular dilatation, but no secretion of sweat, as the atropine paralyzes the secreting nerves. That there are two sets of nerves concerned seems supported by the fact that the skin may be red and hot and yet perfectly dry, or again pale and cold and ae covered with sweat. Whut is the normal Excitant of the Sweat Glands ? Heat is the normal stimulus. How does this act ? It acts upon the sweat centres, not upon the sweat glands directly, nor the peripheral end organs of the nerves presiding over them. How is this shown ? Divide the sciatic nerve of an animal, and place it in a hot chamber: the animal sweats everywhere except on the limb with the cut sciatic. Where are the Sweat Centres ? in the lower part of the spinal cord. How is this proved ? Cut the spinal cord in the dorsal region, and place the animal in a hot chamber, the pads of the feet sweat: 18 cut the roots of the nerves going to the limbs, and there is no more sweat. Hence, the lower part of the cord must contain sweat centres. Why does Heat dilate the Vessels ? When the surrounding atmosphere is warm, the cutan- eous vessels are dilated, the amount of sweat increased, and the amount of evaporation augmented; and all these tend to cool the blood. The dilated vessels also expose a larger amount of blood to the air. When the. atmosphere is coup, the cutaneous vessels are constricted, perspiration is scanty, evaporation less ; so that there is less heat lost. It is in these ways that the skin acts as the great regulator of temperature. Though vascular dilatation usually accompanies _ per- spiration, yet the secretion of sweat is independent of this dilatation, there being special secretory nerves. What is the Effect of Emotions ? Emotions may either give rise to or repress sweat: they may stimulate the sudoriferous nerves directly. Name other Conditions and Drugs that affect Perspiration. Measures and drugs that tend to increase the venosity of the blood cause perspiration, as dyspncea, opium, chloral, chloroform, etc.; also, nicotine and pilocarpine, in part. These measures seem to act upon the cENTRES for secretion. Pilocarpine also acts upon the terminations of the nerves in the sweat glands themselves, and causes an exceedingly profuse and rapid flow of sweat. 14 What is the danger of Sudden Arrest of Sweating ? Some internal organ may become congested—e.g., the lungs, causing pneumonia; or the kidney, causing acute catarrhal nephritis—due to the sudden chill, forcing the blood in upon internal organs. Has the Skin a Respiratory Function ? Cutaneous respiration is marked in the frog. In man it must be very slight, because the epidermis is too thick. Still, if the body be placed in an air-tight bag for some time and the air be analysed afterwards, it is found that the oxygen is lessened and the carbonic acid increased. It -excretes about 120 grains of carbon in twenty-four hours, while the lungs excrete 8 ounces. What is the result of Injecting Sweat directly into the Blood-Stream ? 1. Fever is produced. 2. Albumen is passed by the urine. What is the Effect of Varnishing the Skin ? 1. In the case of the Rasert.—It always dies in a day or two. This is not due to the loss of heat, because even though it be covered with cotton wool, or kept in a warm chamber, it still dies. It is due to the retention within or the re-absorption into the blood of the constituents of the sweat, and a kind of blood-poisoning with fever results. The mode of death is just the same as when sweat is injected directly into the blood. 2. In the case of a Doc.—It does not die, at any rate within a reasonable time. In the dog the sweat glands open into the hair follicle, and not on the surface as in man. 15 Does the Skin absorb Substances ? Gases are absorbed; also some substances applied in a fatty vehicle, and rubbed in —eg., mercurial ointment. Watery fluid and substances in solution are very readily absorbed in places where the horny layer is thin, or when it is removed—e.g., infusion of digitalis applied over the region of the kidneys. What other Method may be used to cause Substances to pass through the Skin ? Diffusion of substances through the skin by means of electricity. What are the Different Ways by which Effete Matters leave the Body ? . By the kidneys. . By the skin. . By the lungs. . By the liver. 5. By the alimentary canal: this is chiefly the refuse matters of food, also cholesterine, hydrobilirubin, part of the pile acids, and mucus. em wh re What are the Chief Waste Products ? 1. Urea, chiefly by the kidneys. 2, CaRBonic acip, chiefly by the lungs. 3. Saurs, chiefly by the kidneys. 4, Water, by the kidneys, lungs, and skin. Thus— The Sxkin—much water, little CO 2, little urea. The Lunes— much water, much CO .z, very little urea. The Kipyeys—much water, very little CO,, much urea, 16 What various agenctes affect the Composition of the Blood ? Food, its amount and kind. State of the digestive organs. Action of the blood glands. . The activity of the excretory organs. . The amount of muscular and nervous activity. Pregnancy—a condition of hyperinosis induced. Diseased condition of organs. Introduction of foreign matters. WAAR wwe DIETETICS. (See also ‘‘Marernta Mepica,” Part I., page 47.) Give the Characters and Composition of ATfilk. It is the type of human food. It is an emulsion of oil globules, and to this its whiteness is due. The globules are very small and protected by a thin envelope of cesin, they are suspended in a colourless fluid. On standing, milk turns sour and curdles; this is due to the production of lactic acid, which precipitates the cesin. The acid is pro- duced by the lactic acid fermentation of the milk sugar, this being caused by the bacterium lactis found in the air of the dairy, adhering to vessels, etc. It is not found in perfectly fresh milk. The specific gravity of milk is 1028 to 1034; its reaction is alkaline, due to the presence of alkaline potassium phosphate. Cows’ milk is also alkaline, but soon becomes acid. How can the Envelopes of the Milk Globules be shown ? 1. Treat them with osmic acid: the fat is blackened and shrinks a little, while the envelope is hardened and comes into view. 17 2. Add acetic acid, the envelopes are dissolved and the fat runs together. 3. Press the cover glass, and this ruptures the envelopes, shreds of which may be seen in the field. Compare the Composition of different kinds of Milk in parts per 1000. Woman. Cow. Goat. Mare, Ass. WATER, . : . 890 860 868 888 907 Soups, . i . 110 140 132 112 93 (1) Proteids, . 35 66 40 16 16 (2) Fat, . « 25 38 33 8 12 (3) Sugar, . . 48 30 53 (4) Salts, | 6 es What are the Proteids of Milk ? Cesin and serum-albumen : mostly cesin. In cows’ milk there are nine parts of ceesin to one part of albumen. Cvesin is potassium albumen. It is chiefly in solution, but part is precipitated and forms envelopes for the milk globules. It is easily coagulated by ferments in the pancreatic and gastric juices (not trypsin nor pepsin). Acids (most) coagulate it. The serum-albumen is not coagulated by rennet, but is left in the whey along with the sugar and salts; hence, the use of this fluid for invalids, and in some cases for infants. What are the Fats of Milk? Margarine, palmatine, olein, and glycerides of butyric, capronic, caprylic, and myristinic acids. When exposed to the air, the fat increases at the expense of the cesin ; this is also seen in the “ripening” of cheese, where the proteids are converted into fat. B 18 What is Milk Sugar ? It is lactose, and belongs to the cane-sugar class, having the composition C,,H,.0,,. It can undergo the “lactic” fermentation, producing lactic acid C,;H,O3;. What are the Salts of Milk ? Salts of the alkalies and alkaline earths —and, like those of the blood, potassium salts predominate,—potassium chloride and phosphate, a good deal of phosphate of calcium, chloride of sodium, and traces of iron phosphate. Describe the Mammary Glands. They extend from the 3rd to the 6th or 7th ribs on each side, and from the sternum to the axilla. Srructure.—They belong to the compound racemose group of glands. Each mamma is made of from fifteen to twenty separate glands gathered together; each of these parts has a separate duct opening on the nipple— galactophorous ducts. Beneath the nipple each duct is dilated somewhat (the sinus or ampulla); the dilatations serve as temporary reservoirs of milk. The ducts, traced back, lead to sacs; and these again to smaller subdivisions or acini ; the acini are lined by short columnar epithelium, and inside these cells oil globules are often found. Give the Structure of the Ducts. 1. Columnar epithelium—non-secreting. 2. Basement membrane. 3. Non-striped muscular fibres.—These fibres also form concentric circles around the base of the nipple, and some bands radiate from the base to apex of the nipple. 19 What Changes occur during Pregnancy ? The breasts enlarge ; the state of the uterus brings about a reflex dilatation of the blood-vessels; hence, hyperemia and growth of gland tissue. There is probably also some special trophic influence at work. The breasts begin to secrete about the third month of pregnancy, though this is but slight till after parturition. What minute Changes occur during Pregnancy ? The alveoli become increased in size and number, and distended with a serous secretion. The epithelial cells enlarge, oil globules are formed in their interior, which gradually pass into the fluid in the lumen to form the milk globules. Each oil globule receives an albuminous coating or cell wall. What is the Effect of Atropine on Milk Secretion 2 It paralyzes the nerves that preside over the secretion of milk. What is peculiar about the Milk of the First Week aster Parturition ? It contains little cesin, but mucH albumen; it also contains a number of compound granular corpuscles—“ Colo- strum corpuscles”—those corpuscles are simply epithelial cells undergoing fatty degeneration. Before secretion begins, the acini are filled with epithelial cells, and these undergo fatty degeneration and flow away with the first milk or “colostrum.” The oil found in milk after the first week is not formed by fatty degeneration. 20 What Changes oceur in the Cells during Secretion ? In the cubical cells lining the aciv1, the nucleus is pushed to one side by the formation of a vacuole, which then becomes filled with oil globules, which are then discharged into the lumen of the acini, probably by a contractile extrusion of the protoplasm. What is the Source of the Fat thus formed ? It is formed at the expense of the protoplasm of the epithelial cells, and not from the fat taken as food. Do Emotions affect the Milk Secretion ? Yes; very much so. Anger, grief, terror, may produce serious modification in the composition of the milk, or suspend its secretion altogether. Milk secreted under these powerful emotions may throw the child into convulsions, and violent passion may actually make it poisonous. Is the Secretion under the Influence of the Nervous System ? Yes: when the nipple is irritated there is a rapid flow ; and when the attention is fixed on the breasts this serves to keep up the flow. The sight or thought of the child causes a rapid flow = “the draught.” The centres for milk secretion are probably in the spinal cord, and the special secretory nerves are probably contained in the intercostal nerves. IWhat is the Source of the Cesin of Milk? It is probably derived from the albumen by the metabolic activity of the cell-protoplasm. When milk is kept at a 21 temperature of 35°C., the ewsin is increased at the expense of the albumen; and when the activity of the gland cells becomes less, albumen is in excess of cesin in the milk. IVhat is the Source of the Fat in Milk? It is derived from the breaking down of proteids by the vital activity of the cell-protoplasm. Give some Proofs of this. 1. Feed a bitch on lean meat (without fat), the amount of fat in the milk is not lessened. 2. Feed her on fatty food, there is no increase of fat in the milk. Proteid food may increase it, but not fat. 3. Fat globules can be seen inside the epithelial cells. What kind of Food is best for Milk Secretion ? A diet rich in animal food and carbo-hydrates. IV’hat ws the Source of the ‘‘ Lactose” ? From the amyloid matters of food, as starch and sugar : it is also found to a slight extent from the metabolism of the cell-protoplasm. Give a Proof of this. Feed a bitch on flesh diet, the milk still contains much lactose—more than can be accounted for by the quantity in the flesh food. 22 What Abnormal Constituents may be found in Milk ? Lactic acid, urea, blood pigment and corpuscles, bile pigment, and various drugs, as iodide of potassium, mercury, morphia, etc. Any or all of these may affect the child. IVhat is the Position of Milk as Food ? It is an example of a typical and complete food: it. contains all the necessary constituents of a perfect diet. IVhat other Food resembles it in this respect ? Eggs. What is the Special Action of the Colostrum ? It has a purgative action, and causes the meconium to be discharged from the alimentary canal. It is secreted for about a week. Compare the Milk of the Goat, Ass, Mare, and Cow, as Food for a Child, Goat’s milk is nearest to human as far as composition is concerned; but it has a bad odour, and forms a very dense curd in the stomach. Marez’s milk contains much sugar. Asses’ milk is good for infants, because the cvesin is easily precipitated, and the curd is delicate. Cows’ milk is most used because it is easily procured and comparatively cheap, but the proteids are in excess, and there is too little sugar (see page 16). 28 How would you prepare Cows’ Milk for a Child ? 1. It has to be diluted—say one-third milk and two- thirds water. 2. Add sugar of milk—this is not so likely to ferment as common white sugar. 3. Heat to about 100 °F. It should not be skimmed, nor should there be any lactic acid present—z.e., it should not be sour, as this may cause diarrhcea in the child. Name the Chief Alimentary Principles. 1. Proteids. 2. Albuminoids, 3. Fats. 4. Amyloids or carbo-hydrates. 5. Mineral constituents— water and various salts. 6. Accessory principles—tea, coffee, alcohol, pepper, mustard, ete. Give Examples of Protetcds. Albumen. Ceesin. Myosin. Fibrin. Gluten (in flour). Legumin (in peas, beans, etc.) ’ 24 Give Examples of Albuminotds. Gelatine—in isinglass and calf’s-foot jelly. Chondrin in cartilage. What is the Value of Gelatine in Nutrition ? It is not nearly so nutritious as proteids, and cannot be entirely substituted for them. Fed on it alone, the animal will die of nitrogen starvation. The consumption of fat is lessened by the use of gelatine; hence, it is of some use. It is supposed to split up into urea and a sugary substance, thus far resembling proteids. It does not form peptone, and cannot take part in the formation of living tissues. The nitrogen equilibrium is said to be established at a lower level of proteid food when gelatine is given. Give Examples of Fats. Suet. Lard. Marrow. Butter. Liver Oil. Olive Oil, and other Vegetable Oils. Give Examples of Amyloids. Cane Sugar. Grape Sugar. Milk Sugar. Starch in Sago. Tapioca. Arrowroot. Iceland Moss. Rice and Potatoes. 25 From whence is Mans Food derived ? Partly from Plants and partly from Animals. Purgty ANIMAL Foop (other than milk) does not main- tain perfect health; salts are too deficient, especially tartrates and nitrates, and scorbutus results. Pure_y VEGETABLE DIET is not sufficient either to main- tain good health. The coloured blood corpuscles become fewer, and the nervous and muscular systems lose their accustomed force. The best diet consists of a proper mixture of vegetable and animal food. Mention a difference between “ Meat Extracts” and Beef- Tea. ‘Meat extract” does not contain albumen, but beef-tea does. IVhat is the place of Alcohol in Dietetics ? Alcohol is partly excreted unchanged by the lungs and kidneys, but most of it is oxidised within the body. Its use leads to the accumulation of fat, though it is not con- verted into fat; it probably interferes with the oxidation of fat, but it does not appear to affect proteid metabolism, and does not affect the excretion of nitrogen by the kidney. Alcohol is not required by an individual in health, but is of great use in cases of weak circulation and defective appe- tite ; it increases the force of the heart’s action, stimulates the nervous system, and promotes digestion. Ale is the most economical alcoholic drink. 26 Give an average Diet—one for Severe Labour and one for Rest. Average. Severe Labour. Rest. 1. Proteids, ‘ 44 ounces. 6-7 ounces. 2-24 ounces, 2. Fats, . . 3 u" 84-43 " 3-1 " 3. Amyloids, . 144 tt 16-18 " 1g u 4. Salts, : . 1 " 14-14 " $ ' 5. Water, . . 80-90 90-100 4 80-90 4 Give the Diet of the British Soldier on Home Service. Met t iwiccid dvkacieas deena ees 12 ounces. IBre add jai cicis saaan has se datemsentve ose hene 24 " POtabOesiecnencsaases anperaneslsraeeness 16 " Other Vegetables .................4. 8 " MAK a iced dectdandsueveansiaeon onsen 3°25 on Sugar i Baia ate Stow: Qianelocsate’ widis\ Seana ara, Fake wustale 133 on CG HC En aco pvomasoheana acs aabedante os 0:33 on MG ariniee olives n racine deanannaweses 016 4 DALE cok toe sium anedensowanuaaadiua iad san 0°25 ou Nabi ci tresses daaca tac camesenentemnade 6 ounces. Oa bin Gali atone cuiAdueoasaau nen naenies 6 on BECCA. ccwkasaanagcstnnndbcnuntcaeatadee 12 " Potatoes cniswnzawisee des eaayenoue sae 8 " METS sate Suis na ha dae Sieided ener i ee Butter vsceitvathcmaaeeaaa os eivedaucnau. 1 " SUGPAT. chssnlsee aie ein sereatnndonnesaatnn a 27 What hind of Diet is best for Training for Muscular work ? Lean meat and mutton, dry toast and potatoes ; no pastry or sweets, and as little fluid as possible. What Diet is best suited for Cold Climates ? One containing a large proportion of prorsmps and especially of rats. The total amount required will also be greater as increased oxidation is necessary to develop the extra heat required. IV hat Diet is best suited for TV’ arm Climates ? In warm climates the digestion becomes less able to digest fats and animal foods. A large proportion of vegetable food is therefore best—e.y., rice. What is the Result of want of Food? Starvation: the animal loses about two-fifths of its entire - weight, and then probably dies. Give the order of Tissue waste ? AGIPOSE: TISSUE: ica scirovsian ee oie mew erica 97 parts lost. I PlOBNs.eesks debs singalageinaldaanehiwtents 63:1 " TaIVOresaiirue imu danamarevnatinniunstale a vitaben tan 566 " Muscle (except Heart)................... 30°2 " IBIGOUL) sxcaoaas nan dated apo menie dau an aie 17°6 " Brain and Spinal Cord................45 0 " Adipose tissue suffers most; next the glandular. The nervous system loses little or nothing, because it is fed 28 at the expense of adipose and muscular tissues. The heart, though a muscle, loses very little, because of its great im- portance, and is therefore fed at the expense of other parts. The same is true of the brain and spinal cord. What is the chief Cause of Death ? Probably the Loss oF HEAT. Hyperesthesia of the nervous system also sets in, and soon ends in delirium. What are the Effects of Variations in the quantity of Proteids ? 1. Wuen wantinc.—Urea and uric acid are diminished, though not entirely absent. Nitrogen must be got somehow, either from the tissues themselves; hence, if absent in the food, the body feeds on itself. 2. DEFICIENT BUT NOT wantTING.—This leads to mus- cular and nervous weakness, and a tendency to low forms of inflammation and fever. 3, WHEN IN EXCESS ALONG WITH PROPER FOOD.—There is a gain in weight, due to the accumulation of fat. The proteid food is split up into a substance that gives rise to urea and fat; the fat is stored up, and the urea passes off by the urine. Therefore, in an exclusively meat diet, the urea is much increased. IV hat Classes of Foods can be best done without ? Life can be maintained for a long time on mineral and proteid foods alone, because amyloids and fats are produced to a certain extent within the body by the breaking up of proteids. 29 What Elements enter into the various Food principles ? Proterps consist of C.H.O.N.S. Fats (or hydro-carbons) C.H.O. (80 per cent of carbon). AmyLotps (or carbo-hydrates) C.H.O. (40 per cent of carbon). How do the Fats and Amyloids differ ? In Fars there is a large excess of hydrogen—more than enough to form water with the oxygen present. In Carpo-Hyprates, there is just enough of hydrogen to form water with the oxygen present. What are the Chief Functions of these Classes of Foods ? Protgips are the “tissue formers”’—build up the new and repair waste. Fats and CarBo-HYDRATES are ‘“ energy-producers,” whether it be muscular energy or heat, or any other form of energy. How do these Foods differ in their Metabolic Effects ? PROTEID FOOD increases the metabolic activity of the tissues, not only of itself but of non-nitrogenous food also—hence the “Banting” treatment of corpulence—but it loads the body with the products of tissue waste. 30 Fats and Carpo-Hyprates differ, in that they are not provocative of tissue metabolism, and can therefore be stored up for future need, and do not give much trouble to the excretory organs. How much Carbon and Nitrogen ure required by the Body in Twenty-four Hours ? Nitrogen, 300 grains | —i.e., the amount of N. required Carbon, 4000 grains} is = 74 the amount of Carbon. Ts it wise to attempt to live on Albumen alone ? No. Why ? Albumen contains 34 grains of carbon for every grain of nitrogen. Hence, to get the proper amount of carbon, 7547 grains would have to be consumed, and this contains 1132 grains of nitrogen, or almost four times too much. In other words, to get 4000 grains of carbon, one must eat 4 lbs. of fatless meat; whereas, 1 lb. will give 300 grains of nitrogen. To get rid of the excess of nitrogen much profitless labour is thrown upon the excretory organs, espe- cially the kidneys, consequently the health breaks down and gout or kidney disease (or both) result. Amyloids supply the necessary amount of carbon without introducing an excess of nitrogen. Can one live on Bread alone ? No; not if health is to be maintained. 31 Why is this? In bread the proportion of carbon to nitrogen is 30 grains of carbon to 1 grain of nitrogen. Hence, in order to get 300 grains of nitrogen, 9000 grains of carbon would have to be consumed, or more than double the necessary amount; here also there would be a great deal of profitless labour thrown upon the excretory organs, especially the lungs. From all this we see the necessity of a mixed diet. What are the Sources of the Fat found in the Body ? It is derived from proteids, from fat itself, and from carbo-hydrates. Give Proofs of its Proteid Origin. 1. A direct proof is the formation of fat in the mam- mary gland from proteid matters. 2. In the “ripening” of cheese, and in milk on standing for some time, fat is produced at the expense of cesin. 3. Feed a bitch on lean meat, far more fat is stored up than could possibly result from the fat of the food taken : she will also give off more in her milk than she could possibly have taken in her food, and that too while she is increasing in weight, so that the fat could not be derived from the store in her body. 4, Fatty degeneration of muscle—where the muscular tissue is transformed directly into fat. 32 Give some Proofs to show that Fat is derived from Carbo- Hydrates. The starch is transformed into sugar, and then the molecules of sugar are probably transformed directly into fat— 1. In feeding a pig 472 parts of fat were stored up for every 100 parts present in the food, and of the non- nitrogenous food 21 per cent. was retained in the body as fat. 2. The food of bees consists chiefly of sugary matters (honey), and much fat (wax) is produced. 3. In diabetes mellitus there is sugar excreted in the urine; this sometimes suddenly disappears, and a great excess of fat appears in the blood. Note.—Fats possess great heating power. CARBO-HYDRATES great fattening power. What Dietetic measures may be adopted to lessen Fat ? 1, Abandon milk and eggs. 2, Abandon butter. 3. Diminish the supply of starch and sugay. 33 ANIMAL HEAT. How may this be Measured ? 1. By the ordinary thermometer, or by the “surface” thermometer. 2. By the thermo-electric method. Which method is usually employed in Physiology ? The thermo-electric method, because by this method one can measure very small amounts—e.g., the heat produced by a single muscular contraction, or the difference in tem- perature between the two sides of the heart. What Apparatus is necessary ? The Thermopile and Galvanometer. Explain the Principles involved. It depends on the fact that, when a circuit, composed of two different metals soldered together, has one of its junctions heated, an electric current will be produced ; further, a magnetized needle will always, if free to move, place itself at right angles to an electric current—e.g., as in the galvanometer. C 34 How are the Thermo-Electric Needles made ? Two different metals soldered together, and then brought to a point; when this junction is heated an electric current is produced, and this is shown by the movement of the needle of the galvanometer. How is the Heat-equivalent of deviation of the Galvanometer Needle measured ? If both the thermo-electric needles are exactly heated to the same temperature the needle of the galvanometer stays at zero, because the two currents are equal and opposite, and thus balance each other. To estimate the “heat- equivalent” (or how much heat the deflection of the galvanometer represents), take two beakers of water with two thermometers, and make the water in one hotter than that in the other, say half a degree, and note the deflection of the needle of the galvanometer. Suppose the deflection of the needle is 50 degrees of surface, then 50 degrees on the face of the galvanometer is equivalent to half a degree of temperature. How would you measure the Heat evolved by a Contracting Muscle ? Put one thermo-electric needle into the muscle, the other into a beaker of water, and then heat the water till the galvanometer needle comes to zero; after that, measure the temperature of the water by an ordinary thermometer. 35 How would you measure the Temperature of an Internal Organ ? One thermo-electric needle is placed in a vuleanite case, and passed into the organ, say the heart; the other needle is placed in a beaker of water, and the temperature estimated as above, IVhich Side of the Heart is the Colder? The err side. This has been said to be due to the fact that the liver is nearer the right ventricle; but that is not the case, the left side being actually colder than the right. Vhat are the Sources of Heat ? Tissue metabolism, and wherever there is friction. Oxida- tion is the great cause, but it also results from the splitting up of complex molecules—eg., as in the liver; the heat produced in the liver is not due to oxidation, because it is chiefly supplied with venous blood, so that the heat produced in that organ is chiefly due to the splitting up of complex molecules. Injestion of hot food and liquids is another source of heat. What Tissues produce most Heat ? 1. Muscres.—Much is produced in muscle; not much perhaps in any one muscle, but taking into account the great mass of muscular tissue in the body, this tissue stands jirst as a heat-producing tissue. 36 2, Guanps, especially the liver.—The hottest blood in the body is found in the hepatic vein (105°F), while the blood in the portal vein is 100°F, A great deal of blood has to pass through the liver; and in order to raise it all 5°F., the liver must produce a great deal of heat—much more bulk for bulk, than muscle. Other glands produce heat to a less extent. 3. Brain anp Nerve tissur.—The blood leaving the brain is hotter than that going to it. The heat is chiefly produced in the nerve cells, because there chemical changes are always taking place. There is a close relation between the amount of heat and the amount of carbonic acid produced, because heat is derived from tissue metabolism. How is Heat Lost to the Body ? 1. By the skin, 77°5 per cent. 2. By the respiratory passages, 20 per cent. 3. The rest is lost by the discharges, as the urine and feces. How is the Loss by the Skin affected ? It varies with the dilatation of the blood-vessels and the secretion of sweat. When the vessels are contracted, less flows through them, and therefore less is cooled ; when they are dilated, the reverse obtains. Increased secretion of sweat favours the loss of heat, because of its evaporation. 37 How is it Lost by the Respiratory Passages ? Chiefly from the blood-vessels of the nose, pharynx, trachea, and bronchi; and very little from the blood in the pulmonary capillaries: there is a little lost, however, in the way last named, for the blood in the left ventricle is colder than the blood in the right ventricle. How does Muscular Exercise affect the Guin and the Loss of Heat ? There is much heat produced, but much also is lost, because— 1. Respiration is quickened, and therefore more is lost by the lungs. 2, The circulation is quickened and the vascular areas dilated, and more blood therefore is exposed to the cooling effect of the atmosphere. 3. There is free perspiration. How does the Body withstand External Cold ? External cold defeats its own ends, because the surface vessels become constricted, while the splanchnic areas are dilated, and blood is thus drawn from the surface to the interior of the body. External warmth produces the opposite effects; for in this case the surface vessels dilate and heat is carried off quickly, and at the same time the skin is bathed in per- spiration. By these means the temperature of the body is kept pretty uniform, notwithstanding unequal loss and unequal production of heat. 38 What .is the Mean Temperature of the Body ? In the axiuia, 98°6°F. Under the tongue, from 99-100°F.—i.e., about a degree higher than in the axilla. Give some of the Causes of Variations of the Temperature of the Body in Health, 1. Acr.—Up to 14 years it is about 1°F. higher : later, it is only about $°F., and gradually falls till 40 years of age, and then stops. In old age it may again rise a little. It is higher in the child, because of the more active tissue metabolism. 2, PgRIoD OF THE DAY.—Lowest between 2 and 6 a.m., and highest between 5 and 8 p.m. It may vary from 1 to 3°F, 3. Foop.—A rise after meals. 4, Loss or Broop.—lIf great, the temperature falls from 3 to 5°F.: the red corpuscles are lost, and therefore less oxygen is carried to the tissues. 5. MuscuLaR EXERTION.—A marked rise. 6. CLIMATE AND SEASON,—This causes but little variation. Why is this ? 1. Because the temperature is to a great extent self- regulating. 2, Because one can put on or take off clothing according to circumstances. 39 What do you mean by Cold-blooded and Warm-blooded Animals ? “Cold-blooded ” animals are those in which the tempera- ture of the body is but slightly raised above, and varies with, the temperature of the medium in which they live. All classes of animals are cold-blooded, except birds and mammals. ‘*Warm-blooded” animals are those in which the bodily temperature is considerably above that of the surrounding medium, and it is so regulated that it remains constant, notwithstanding variations in the temperature of the sur- rounding medium. What are the means for Regulating Temperature ? 1. Variations in the loss of heat. 2. Variations in the production of heat. How are Variations in Loss brought about ? 1. Loss THROUGH THE SKIN— (1) The blood-vessels are dilated. (2) Much sweat is produced, and much heat is abstracted from the blood to evaporate it. In perfectly pry air the body can stand a temperature of even 260° I, because the rapid evaporation from the surface keeps the temperature low. The skin presents a large surface for radiation and con- duction of heat, and evaporation of sweat, as well as 40 exposing a large volume of blood to the cooling effect of the atmosphere. 2. Loss py Resprration.—The breathing becomes more rapid, as the warm blood acts on the respiratory centre, and we get a form of “HEat-pyspnaa.” This is very easily produced in the dog or rabbit. It also occurs in ' fevers. How are Variations in the Production of Heat brought about ? 1. By the nature and the amount of the food eaten— e.g., much fat is consumed in cold countries; and carbo- hydrates (rice) in warm countries. 2. By the amount of physical exercise. 3. By the nature and the amount of clothing. State the Effects of Heat and Cold on the Tissue Metabolism of Cold-blooded and Warm-blooded Animals. In “cold-blooded” animals, cold LEssEns, and heat INCREASES, the general metabolism of the body: and there- fore, if the medium be warm, so are they; and if cold, they are cold also. Expose a “warm-blooded” animal to hot or cold sur- roundings, within moderate limits, the temperature does not vary perceptibly. This is because cold mncreasss and heat Lessens the general metabolism of the body. Cold increases the absorption of oxygen and the production of carbonic acid, and thus increases the production of heat, while hot surroundings lessens it. 41 Has the Nervous System any relation to Heat Production ? Yes: it is possible that there may be a thermogenic mechanism. Give Reasons. 1. Injury to the cerebro-spinal axis may cause a rise or a fall in the temperature. In one recorded case it rose as high as 120°F. and remained so for several days. This was neither due to dilatation of the blood-vessels nor to diminished loss of heat. 2. Expose an uninjured rabbit to cold, and there is an increased production of heat. Paralyse by curara and expose to cold, there is only a very slight rise of tem- perature. This is probably because the efferent nerves are paralyzed and impulses are unable to pass to the muscles to increase the metabolism. It is possible, therefore, that the nerves of muscle are constantly affecting heat production in that tissue. 3. In fever the temperature is raised, probably because there is a thermotaxic inhibitory mechanism; and in fever this is paralysed, and hence the metabolism of the body runs riot. What is the Effect of a very High Temperature ? It makes the heart-beat rapid and irregular, and finally stops it. Respiration is also increased: this is due to the action of the hot blood on the respiratory centre. In mammals 6° or 7°F. above the normal (if continued) is fatal—say 107:5°F. 42 What is the Effect of Lowered Temperature ? A low temperature is more easily borne than a very high one. A warm-blooded animal tends to go to sleep, and pass into the condition of an hybernating mammal: these may be cooled down almost to the freezing point with impunity. Does the Temperature ever Rise after Death ? Yes; this is due to the setting in of rigor mortis. VOICE AND SPEECH. Name the apparatus of Voice and Speech. 1. Bellows—viz., lungs and chest. 2. Vibrating membranes—viz., the vocal cords. 3. Chambers for resonance and articulation— chest, pharynx, mouth, and nose. Name the Cartilages of the Laryne. They are three paired, and three single— 1. Sinete— (1) Cricoid. (2) Thyroid. (3) Epiglottis. 2 2. Parrep— (1) Arytenoid. (2) Cornicula laryngis (Santorini). (3) Cuneiform cartilages (Wrisberg). 43 Give a Short Description of the Thyroid. The origin of the name is due to its shield-like shape. It consists of two lateral plates united in front at an angle—the “‘ Pomum Adami.” is sliced off to allow it to rise behind the hyoid bone in deglutition, and is covered by a bursa. sponding excavation in the hyoid bone. What Muscles are attached to it ? OUTER BORDER— 1. 9 as 3. Thyro-hyoid (origin). Sterno-thyroid (insertion). Inferior constrictor (insertion). PosTERIOR BORDER— Stylo-pharyngeus (insertion). INFERIOR BORDER— Crico-thyroid (insertion). Name the Parts attached on the inner aspect of Angle. From above downwards— 1. . Apex of epiglottis. Poe OE OP BS Anterior thyro-hyoid ligament. False vocal cords. True vocal cords. Origin of the thyro-arytenoids. Crico-thyroid ligament. The upper part of the angle There is a corre- 44 What are the Cornua ? The posterior border is prolonged into cornua — the superior give attachment to the posterior thyro-hyoid liga- ment ; the inferior articulate with the cricoid by a perfect joint. The axis of movement is a transverse line through both joints. Describe the Cricoid Cartilage. It resembles a signet ring, being deep behind and narrow in front. What Muscles are attached to it ? To THE sIDE— Crico-arytenoideus lateralis (origin). Crico-thyroid muscle (origin) and membrane. Inferior constrictor (origin). PosTERIOR PART— The two posterior crico-arytenoid muscles. Describe the Arytenoid Cartilages. They resemble pyramids, having three surfaces, a base, and apex. The Base is seated on the cricoid, its anterior angle giving attachment to the true vocal cords, and its external angle to the crico-arytenoideus posticus and lateralis. The posterior surface gives attachment to the arytenoids; the ANTERIOR to the false vocal cords and thyro-arytenoids. ~ 45 Describe the Epiglottis. It is shaped like an obovate leaf, and situated behind the tongue, and in front of the superior opening of the larynx. What kinds of Cartilage do we find in the Laryne ? Epiglottis ................ | Cornicula laryngis...... = yellow fibro-cartilage. Cuneiform cartilages... | All the other cartilages are hyaline. What are the Ligaments of the Larynx ? 1. Extrinsic— (1) Thyro-hyoid membrane. (2) Lateral thyro-hyoid ligaments. 2. InTRinsic— (1) Crico-thyroid membrane. (a) Mesial part. (b) Lateral parts. (2) Superior thyro-arytenoid ligaments. What are the True Vocal Cords ? They are two bands of yellow elastic tissue covered with mucous membrane, attached in rront to the angle between the ale of the thyroid, and Beainp to the anterior tubercles at the base of the arytenoids. They are formed by the 46 upper free edge of the lateral parts of the crico-thyroid membrane, and their free edges are directed upwards. They are sometimes called the “inferior thyro-arytenoid ligaments.” The mucous membrane over them does not contain mucous glands, nor is it covered with ciliated epithelium. What are the False Vocal Cords ? A few fibrous fasciculi in the mucous membrane, forming projecting folds, and situated above the true cords. They are also called the “superior thyro-arytenotd ligaments.” What do the terms “ True” and “ False” mean ? The “TRuE” are immediately concerned in the production of the voice: whereas the “razsm” are not immediately concerned in voice production. Give the Appearance of the Larynx as seen by the Laryngoscope. 1, At each side two rounded elevations corresponding to the cartilages of Wrisberg and Santorini. 2. In the middle line, in front, a rounded swelling—the “cushion of the epiglottis.” 3. A narrow fissure—the rima glottidis. 4. Above this the false vocal cords, and between the false and the true cords we find— 5. The ventricles of the larynx, leading to the laryngeal sac, 6. In deep inspiration one may see the bifurcation of the trachea. AT What is the ‘* Rima Glottidis” ? It is the chink between the true vocal cords and the inner surfaces of the arytenoid cartilages. What are its Divisions ? 1. Vocal part—the anterior two-thirds, bounded by the true vocal cords. 2. Respiratory part—the posterior one-third, between the arytenoid cartilages. How does the Size of the “ Rima” vary ? 1. In the production of voice, or of a high note, it forms a narrow slit. 2. In easy respiration, it forms a long triangle, with its base behind. 3. When fully dilated, as in taking a deep breath, it is lozenge-shaped, the posterior angle being truncated, What are the Ventricles of the Larynx ? Narrow openings (one on each side), between the false and the true vocal cords. They communicate with the laryngeal sac and a pouch between the true and false cords, but especially up behind the false cords. Each pouch contains from 60 to 70 mucous glands. 48 Give the Origin, Insertion, and Action of the Intrinsic Muscles of the Larynx. 1. CRICO-ARYTENOIDEUS pPosTicus. — Arises from the posterior part of the cricoid cartilage, and is inserted into the posterior external tubercle of the arytenoid. Action— It opens the glottis by rotating the arytenoids round a vertical axis. 2. CRICO-ARYTENOIDEUS LATERALIS. — Arises from the upper border of the lateral part of the cricoid cartilage, and is inserted into the posterior external tubercle of the arytenoid. . Action—It closes the glottis, being antagonistic to the former muscle. It is assisted by— 3. The ARYTENOIDEUS, a transverse band of muscle pass- ing from the posterior surface of one arytenoid cartilage to the other. 4. Crico-rHrroip.—Arises from the side of the cricoid cartilage, and is inserted into the lower border of the thyroid, including lesser cornu. Actton.—It is the chief tensor, by pulling the thyroid cartilage forwards and downwards. 5, THYRO-ARYTENOIDEUS.—Arises from the angle between the ale of the thyroid, and is inserted into the front surface of the base of the arytenoids; some of the fibres are also inserted into the true vocal cords. Action—They relax and support the true vocal cords. What are the Laryngeal Movements during Deglutition ? It is drawn up by the stylo-pharyngeus, the thyro-hyoid, etc., to meet the descending epiglottis, which is pushed down and partly drawn down by the aryteno-epiglottideus. The glottis is also closed during deglutition, so that there is a double safeguard against the entrance of food into the larynx. 49 What are the Joints of the Luryny ? 1. Crico-THyror : between the inferior cornua of the thyroid and the posterior part of the sides of the cricoid cartilage. It is a perfect diarthrodial joint. The axis of movement is a transverse one, passing through both joints. 2. Crico-aRYTENOID: between the base of the arytenoids and the superior facets of the cricoid. It rotates round a vertical axis, and the anterior angle of the arytenoids is moved inwards or outwards, so as to open or shut the glottis. What other Movements take place at the Crico-Arytenoid Joints ? In addition to the rotation round a vertical axis, we have also— 1. A sliding lateral movement. 2. A gliding backwards and forwards. Give the action of the Muscles. Crico-THYROIDS — make tense the true vocal cords ...........cc.c cee ceseeee re .,. pgovern pitch. THYRO-ARYTENOIDS have an opposite OO Cb peinerestacgniaiicubec a Sdeame anes These movements occur at the crico-thyroid joints. Crico-arytenoideus posticus—open glottis Crico-arytenoideus lateralis Arytenoideus idth. | close glottis ee These movements occur at the crico-arytenoid joints. D 50 What are the Arteries of the Larynx ? Superior and inferior thyroids. What are the Nerves of the Larynx? INTERNAL Brancu.—NSensory to the mucous membrane of the larynx, and also sends a fila- Superior Laryngeal ment to the root of the tongue (from ganglion of trunk) in front of the epiglottis. EXTERNAL Brancu. — Motor to Wins crico-thyroid, and part of arytenoideus. Motor to all the intrinsic muscles Inferior Laryngeal | except the crico-thyroid, and part of the arytenoideus. What Lifects result from Division of the Inferior Laryngeal Nerve ? Cut the nerve on one side, then all the muscles on that side are paralysed except the crico-thyroid. The voice becomes very imperfect, though one can still speak a little. Cut both, the voice is lost. There is a peculiar choking sensation as the glottis closes, and there is also a peculiar whistling sound produced during inspiration. What takes place when the Superior Laryngeal is divided ? There is a loss of sensation and paralysis of the crico- thyroid, and the power to produce notes is lost. Stimulate 51 the upper end, there is instant reflex closure of the glottis, and a movement of deglutition—because of the filament to the tongue. How is Voice produced ? By the larynx, after the manner of a reed instrument —i.e., the stream of air is modified from a state of uniform tension into a stream of alternately increased tension and diminished tension (the condensation phase and the rare- faction phase of a sound wave) backwards and forwards in the line of propagation. What Points have to be noted in studying “ Voice” ? 1. Pitch. 2. Loudness. 3. Quality, timbre, or clang-tint. On what does Pitch depend ? It depends on the rapidity of vibration of the vocal cords: the rapidity depends on their tension and on their length. How does Voice differ in the two Sexes ? In the male the vocal cords are longer, and the “ pitch” is lower than in the female. On what does “* Loudness” depend ? It depends on the amplitude of vibration of the vocal cords. 52 On what does the “ Timbre” depend ? 1. On the state of the vocal cords. 2. On the state of the resonance chambers. 3. On the number of over-tones thrown in. If the cords are congested or thickened, the voice is muffled. What is the principle of a Resonator ? It is a hollow body which, along with its contained air, vibrates in unison with the note produced. It “speaks to the sound,” takes it up and gives it out- again, and thus increases the effect. Name the Voice Resonators. 1. Lower resonators—the chest and trachea. 2. Upper resonators are the mouth, pharynx, nose, antrum of Highmore, and frontal sinuses. How do the Resonators affect the Sounds ? They chiefly affect the quality of the note produced, especially by alterations in the size and shape of the mouth and pharynx. What is noted when the Vowels are all sounded on the same key ? They seem to rise in pitch, in addition to alterations in their quality. To what ts this clue ? From the different conditions in the upper resonators, and to the number of over-tones thrown in. 53 What Sound gives the richest Tone ? The broad AH! This is because of the distinct marking of many of the over-tones. What are the hinds of Musical Tones ? 1. Simple. 2. Compound (= a “ clang”). What is meant by “ Simple” ? That there are no over-tones. Give an Hvample. A tuning-fork gives a simple tone, if sounded with a bow ; but if struck, it is complex. Give an Example of « Compound Tone. A string always gives a compound tone, and so do the vocal cords; the compound tone, or clang, thus pro- duced consists of a fundamental tone and of harmonies or over-tones. What zs the Relation between the Fundamental Tone and the Over-Tones ? If » indicate the number of vibrations of the funda- mental note, the over-tones are multiples of its vibrations in arithmetical series, thus— Fundamental Tone. Over-Tones. Ln. 2n, 3n, 4n, 5n, 6n, Tr, Sn. The vowel sounds are all “ clangs.” 54 In what way can the “ Clangs” of the different Vowels be analysed ? By means of the brass resonators of HenmHoLrz, attached to the manometric flame apparatus of Konic, and revolving mirrors. How ts the Falsetto Voice produced ? Some say it is due to the vibration of the thin edge of the vocal cords only ; others, that they may vibrate in nodes. The pitch is always high, and much air is required to produce them. How do the Vowels differ from Consonants ? The vowels are musical notes, while the consonants are mere noises produced in the resonance chambers by the lips, tongue, soft palate, and nose. What is the difference between Voice and Speech ? Voice can be produced in the larynx alone. SPEECH requires the mouth and lips, as well as the larynx. Is the Tongue absolutely necessary for Speech ? No; even when the tongue is cut out, one can still speak tolerably well. How are Consonants Classified ? Labials. Linguals. Palatals. IN asaS setae amen M. N. Ng. Explosives .......... BeP: D.T. G.K. Aspirates ............ WAVE. 2.8. L. Ch. J. Vibration sounds... Br. = R (English) R (French) 55 To what is Stammering due ? Irregular actions of the nervous centres: produced by temporary spasm of the glottis, associated with temporary embarrassment in other parts concerned in articulation. What Points have to be specially attended for its Cure ? 1. Avoid all excitement. 2. Careful practice of the difficult syllables, with a clear knowledge of their correct substitutes. 3. To stop and take breath and recover self-confidence. THE SENSES. What are “the Senses” ? They are the means of communication between the mental or inner world of the individual, and the world around him—the outer world. What is necessary for this ? 1. Peripheral end organs specially adapted for stimulation by the requisite kind of mechanical energy—e.g., light for the eye, sound for the ear, etc. 2. Nerves to convey the excitement thus produced to the— 3. Central organs, or sensorium. What is Sensation ? It is a state of consciousness. VV Where is the seat of Sensation ? The brain, and it alone. On what does the Intensity of Sensation depend ? 1. The intensity of the stimulus. 2. Duration of the stimulus. 3. Excitability of the sensory apparatus. What is meant by “ After-Sensation” ? A sensation lasting after the usual stimulus has come to an end. Describe the kinds of ‘‘ After-Sensation” ? 1. The Postrive.—This is best observed after a mo- mentary stimulus. Look at an object for an instant, and then close the eyes: the object is still seen and its parts have the same form and colour, and it is therefore called “ positive.” 2. The Necative.—This is best observed after a long stimulus. In this case, the object seen would not have the same colour or form, and the after sensation would be called ‘ negative.” What is meant by ‘ Subjective Sensations” ? Sensations felt without the usual cause or stimulus— e.g., light seen or sounds heard, when there is neither light nor sound. 57 SENSE OF SMELL. What are the purts of the Nose ? 1. A part on the face. 2. Nasal fossee, separated by septum. 3. Posterior nares, opening into pharynx. What is the Mucous Membrane called ? The pituitary or Schneiderian membrane. It is firmly united with the periosteum and perichondrium, over which it lies. It is thickest and most vascular over the inferior turbinated bones. What are its Connections ? It is continuous with— 1. The skin, through the nostrils. 2. The mucous membrane of pharynx, through posterior nares. . The conjunctiva, through the nasal duct and canaliculi. 4. With the several sinuses of the skull. eo When inflamed, therefore, the inflammation may spread to any of these parts. : JO Describe the “ Regions” of the Nose. 1. REGION OF EXTERNAL NOSTRILS (the part on the face). This part is lined with stratified squamous epithelium. 2. OLFactorY REGION.—The roof of the nose, superior and middle turbinated bones, and the upper two-thirds of septum. The epithelium in this region is non-ciliated and columnar, and contains the peculiar “ olfactory cells.” 3. Resprratory REGION.—The floor of the nose, inferior turbinated bone, and lower third of the nasal septum. Here the epithelium is columnar and ciliated. Describe the “ Olfactory Cells.” They are sometimes known as Schultze’s cells. Each consists of a spindle-shaped cell, with a large clear nucleus, surrounded by a little granular protoplasm. Lach cell has two processes— 1. A peripheral process, rod-shaped, and passes up be- tween the columnar cells, and ends abruptly about the same level as the columnar cells. In man, there are no hairs at the end of this process, though in some animals there are —e.g., the frog. 2. Central or deep process; this is very slender and ampullated. It probably becomes directly continuous with the fibrils of the olfactory nerve. Name the Conditions of Simell. 1. Odorous particles are transported to the olfactory region of the nose by sniffing. 2. They must be conveyed to the mucous membrane in a gaseous, not a fluid medium. 59 3. The membrane must not be too dry, or too wet, nor too cold. 4. The particles must be dissolved in the moisture of the membrane, and stimulate the “olfactory cells.” Wht is the supposed Cause of different Smells ? It is supposed to be due to different modes of stimulation of the olfactory cells, or to wave motion of different lengths. Some think that there are special nerve endings for each smell. Stimulate by electricity, a smell of phosphorus is the result. How would you classify Smells ? 1, Agreeable. 2, Disagreeable. Bad smells are usually deleterious, though this is not always a good guide—e.g., carbonic oxide has no smell, and is very dangerous. Smell is more closely related to alimentation (flavour) than to respiration. What are the Nerves of the Nose? 1. Olfactory—Ist cranial—special sense of smell. 2. The 5th cranial, common sensibility, heat and tactile sensibility. What ts Anosmiu ? It is want of the sense of smell. In such cases the olfactory nerve is usually atrophied or wanting. It may be congenital. When the olfactory nerves are cut in a dog, and his eyes tied up, he does not smell a piece of meat when held to his nose—z.e., smell is destroyed. Ammonia will produce an effect, but this is because it stimulates the 5th nerve. When the fifth alone is cut, even then smell is somewhat impaired. What are the Results of Stimulating the Fifth Nerve ? 1. Reflex secretion of tears (excito-secretion). 2, Sneezing (excito-motor). 3. Sensation. TASTE, Describe the Papille of the Tongue. They are all compound in character— 1. Fittrorm.—These are the most numerous and smallest; they are minute, conical, and tapering. They are arranged in lines diverging obliquely from the central raphe. The secondary papille contain elastic fibres, are not obscured as in the case of the other papille, and are covered by dense imbricated epithelial scales. These papille are very marked in carnivora, and are useful for rasping bones, ete. 2, Funerrorm.—These are not so numerous, are scattered over the dorsum, especially at the sides and tip. They are of a deep red colour; the base is contracted, and the apex rounded and club-shaped. 3. CrrcuMvALLATE.— The least numerous and largest ; they are from 7 to 12 in number, and are arranged in a V-shaped manner, the apex being at the “foramen cecum.” They are placed in cup-like depressions, and are surrounded by a trench. Embedded in the sides of the papillae are many flask-shaped bodies, called TAsTE-BUDS, being the end organs of the nerve of taste. 61 Describe the Taste-Buds. Their apices appear as pores opening into the trench. They are formed of two sets of cells— 1. The outer corricaL or investing cells are elongated, flattened, and tapering at the ends, much like the staves of a cask; they have a single oval nucleus. 2. The cenrraL, or enclosed, or gustatory cells are spindle-shaped, and form a core within the other cells; each cell has an oval nucleus, and at each end delicate hair-like processes. One projects into the gustatory pore ; the other is branched and is continuous with the nerves © of taste. Where ure the Tuste-Buds found ? 1. In the sides of the circumvallate papille, not in the outer wall of the trench. 2. A few in connection with the fungiform papille. 3. Posterior surface of the epiglottis. 4, Anterior pillars of the fauces. What parts of the Mucous Membrane are concerned in Taste ? 1. Posterior third of tongue. 2. A line, about a quarter of an inch wide, round the edge of the upper surface of the tongue. 3. Under part of the soft palate. 4, Anterior pillars of the fauces. 5. Posterior part of the hard palate. 6. Posterior surface of epiglottis. What are the Conditions necessary for Taste ? 1. Substances must be in solution (compare with “Sense of Smell”), or be capable of being dissolved by the saliva. 2. It is best when they are swallowed, for then the substances are pressed into the taste-buds. 3. It is best about 40°C.: above or below this, taste is impaired. How would you Classify Tastes ? 1. Sour Anterior part of tongue—sour 2. Sweet \ the edge, sweet the tip. 3. Bitter 4. Saline Different tastes, probably due to different modes of stimulation of the nerves of taste—wave motion of different lengths. \ Posterior part of tongue. How do we judge of Flavour ? Chiefly by the sense of smell. What about the Duration of a Taste ? Gustatory impressions take a little time to develop, but they last for some time. There is no relation between the chemical constitution of a substance and the taste it produces. What ts the Function of Ebner’s Glands ? They are washing apparatus. They pour a watery secretion into the trench around the circumvallate papilla, and wash away spent substances. 63 What are the Nerves of the Tongue ? 1. CoMMON SENSATION— (1) To anterior 2, lingual branch of 5th cranial. (2) To posterior 4, glosso-pharyngeal, and lingual filament, from the superior laryngeal branch of vagus. 2. SPECIAL SENSE OF TASTE— (1) To anterior 3, chorda Tympani, from portio dura of 7th cranial. (2) To posterior 4, glosso-pharyngeal. 3. Motion— The 9th cranial. Give some Proofs of this. 1. When the glosso-pharyngeal is cut, taste is lost in the posterior 4 of tongue. 2. Cut lingual above its junction with the chorda, sensa- tion is lost—taste is not. 3. Cut after their union, both taste and sensation are lost. 4. Cut portio dura, taste is lost in anterior 2 of tongue. 5. Touch the chorda tympani with caustic as it passes the tympanic membrane, there is a sensation of taste. If the nerve be destroyed in ulceration of the membrane, taste is lost in the anterior 2 of the tongue. Edinburgh : Printed by E. & 8S. Livinesroys, 4 Melbourne Place. eae ad CATECHISM. SERIES. .6? 7 BN a Pid io eos OuGi PART VII. EYE, EAR, AND CRANIAL NERVES. 7 EDINBURGH: Boe & LIVINGSTON E. PRINTED BY E. & 8, LIVINGSTONE 4 MELBOURNE PLACE EDINBURGH, a + iy > LIBRARY. 4 "L + 4- acs “ee PHYSIOLOGY. PART VII. THE EYE. What are the Couts of the Eye? 1. Cornea and sclerotic. 2. Choroid, ciliary body, and iris. 3. Retina. Describe the Cornea. It forms about one-sixth of the whole circumference, and is the arc of a smaller circle than the sclerotic. It is overlapped by the sclerotic (and also joined to it by continuity of tissue), like a watch-glass by the edge of the groove into which it is received. (tive its different Layers. 1. ANTERIOR EPITHELIUM—squamous and stratified. 2, ANTERIOR BLASTIC LAMINA—modified basement mem- brane. 3. PROPER CORNEAL SUBSTANCE—a compact form of fibrous tissue, but is perfectly transparent, and on boiling yields chondrine; fibres are in layers, and in the anterior part 4: , we find “binding fibres ”—analogous to “ Sharpey’s fibres’ in bone. Between the layers are flattened branching cell spaces. Cells are of two kinds— (1) Fixed branching cells. (2) Amesboid cells or leucocytes. 4, PosTERIOR ELASTIC LAMINA (membrane of Descemet or Demours). It is thicker than the anterior, and at the circumference breaks up into fibres that pass over the front of iris, forming the ‘‘ pillars of the iris.” 5. PosTERIOR EPITHELIUM—a single layer of squamous cells. How are the Nerves of the Cornea arranged ? In the form of very fine plexuses that penetrate as far as the anterior epithelium. The cornea is non-vascular. Describe the Selerottc. The sclerotic (‘white of the eye”) forms five-sixths of a circle: it is thickest at the back, and thinnest about 4 inch from the cornea. It consists of ordinary fibrous tissue, with elastic fibres and connective tissue corpuscles. Its inner surface is light brown in colour, and is known as the ‘lamina fusca.” It is pierced behind by the optic nerve. What is “ Tenon’s Space” ? It is a large lymph space outside the sclerotic, towards its posterior part, like a bursa. What is the “ Ligamentum Pectinatum Iridis” ? It is a structure on the inner aspect of the sclero-corneal junction, and is chiefly formed by the “ posterior elastic 5 lamina” of the cornea, and is covered by the posterior epithelium. It is reticulated in structure, there being spaces between the fibres (‘‘spaces of Fontana”). What is the Cunal of Schlemm ? It is a lymph space (‘sinus circuluris iridis”), outside the ligamentum pectinatum, in the sclerotic, close to its junction with the cornea. It communicates with the cavity of the aqueous through the ‘spaces of Fontana” in the “ligamentum pectinatum.” It is said to com- municate with the sclerotic veins. Describe the Choroid. This is the vascular, pigmented, and muscular coat of the eye. It reaches forwards nearly to the cornea, and ends in a series of plaits or folds—the “ciliary processes.” These folds fit into corresponding depressions in the sus- pensory ligament of the lens. What are its Luyers ? From without inwards— 1. The stroma, or “LAMINA FUSCA,” connects it with the sclerotic; and in it ramify the blood-vessels and nerves. 2. Venaz Vorticosz—veins form the chief part of this coat; they are arranged in curves that converge to four or five principal trunks, which pierce the substance of the choroid. 3. Tunica Ruyscuiana—a very fine capillary plexus. 4, Lasava Vitrea—very thin and transparent, probably corresponds to the “lucidum tapetum” of oxen, horses, etc. 5. HexaGoNaL PIGMENT CELLS, which some regard as belonging to the retina. 6 What is the Chief Use of the Choroid ? It is to absorb, by means of its pigment, those rays of light that pass through the retina, and thus prevent their being thrown again upon the retina, so as to interfere with the distinctness of the images there formed. Hence, animals in which the choroid is destitute of pigment, and human albinoes, are dazzled by daylight and see best in the twilight. Describe the Entrance of the Optie Nerve. It pierces the sclerotic about ;'; inch internal to the axis of the eyeball, and its fibrous sheath blends with the sclerotic, and the nerve fibrils pass through in several bundles, giving rise to a cribriform appearance. What is this Part called ? The “ Lamina Crisprosa.” Describe the Iris. It is a circular contractile diaphragm in front of the anterior surface of the lens. It is attached by its cir- cumference to the cornea, sclerotic, and ciliary processes (by the “ligamentum pectinatum iridis”). Its inner edge forms the pupil, and is bathed in the aqueous humour. The pupil is not quite in the centre, being a little internal to the centre. The iris gives the peculiar tint characteristic of each eye. What ts its Structure ? 1. A layer of cells, continuous with the posterior epithelium of the cornea, z 2. It has a stroma of connective tissue cells and fibres. 3. Two sets of muscular fibres— (1) Circular (spaincter), close to the pupil. (2) Radiating (piLaTor), passing from the circular fibres to the ciliary margin. 4, The posterior surface is covered by dark pigment, with a deep purple tint (=uvea). It is this pigment that gives the colour to BLUE eyes: in eyes of other colours there is in addition pigment scattered through the stroma. The iris is very vascular, almost partaking of the character of an erectile structure. The arteries are—the long posterior ciliary and the anterior ciliary. The long form two arterial circles, major and minor. Describe the Ciliary Body. It consists of— 1. The ciliary processes (see page 5). 2. The ciliary muscle. Describe the Ciliary Muscle. It arises by a thin tendon from the posterior surface of the anterior part of the sclerotic, close to the canal of Schlemm and spaces of Fontana, opposite scrlero-corneal junction. The fibres pass backwards and outwards, and are inserted into the choroid opposite the ciliary processes. It is a fan-shaped muscle, and consists of circular and radiating fibres. The circular forms a ring round the inser- tion of the iris—the “ring muscle” of Miiller. The muscle tends to pull the choroid and ciliary processes forwards— tensor of the choroid. What is the Retina ? It is the peripheral termination of the optic nerve. It rests on the hyloid membrane, and extends forwards almost to the outer edge of the ciliary processes, and ends in a finely indented border—the “ora serrata.” From this point there passes to the tips of the ciliary processes a layer of columnar cells without pigment—the ‘pars ciliaris retin.” What is seen on its Surface ? 1. In the centre we find the yellow spot (macula lutea). 2. In the centre of this we find a depression, the fovea centralis—the thinnest part of the retina. 3. The optic disc, #5 inch to the inner side of the yellow spot—the entrance of the optic nerve or ‘blind spot.” The central artery of the retina enters at the “ blind spot.” What are the Layers of the Retina? 1. Internal limiting membrane. 2. Layer of nerve fibres— sheaths wanting, consist simply of axis cylinder. Layer of nerve cells. . Inner molecular layer. . Inner nuclear layer. Outer molecular layer. . Outer nuclear. External limiting membrane. TO oR oo 9 Rods and cones. 10, Hexagonal pigment cells (already mentioned under the “Choroid”). 9 What ts the Connective Tissue of the Retina called ? The “fibres of Miiller”; these fibres pass through the whole thickness of the retina, and support and bind together the different layers. How does the Structure differ at the ‘ Yellow Spot” ? There are no rods, but the cones are more numerous, longer, and narrower. All the other layers are much thinned at the “fovea,” though at the margin they are thicker. Blood-vessels are almost wanting; the layer of nerve cells are from six to eight deep—in the rest of the retina they are only one deep. The outer granular and outer nuclear layers are well marked: the “fibres of Miiller” are absent in the ‘“ fovea.” The larger vessels bend round and seem to avoid the yellow spot. Nume the “ Refracting Media of the Eye. " 1. Aqueous humour. 2. Crystalline lens. 3. Vitreous humour. What is the Vitreous Humour ? It consists of layers of mucous tissue containing mucin, with lymph between the layers. The part next the retina is in distinct layers; the central part is very fluid. There are some stellate corpuscles, and wandering cells. Has it any Blood- Vessels ? Not in the adult. In the foetus a vessel passes through it to the capsule of the lens—the HYaLoIp aRTERY ; this is a continuation of the central artery of the retina, and dis- appears at seven months, though the canal is always there. The canal is called the ‘canal of Stilling,” and is lined by a prolongation of the hyaloid membrane. 10 What is the “ Hyalotd Membrane” ? A membrane that surrounds the vitreous humour, except in front where it passes on to the anterior surface of the lens, forming the “zonule of Zinn,” or suspensory hgament of the lens. It is transparent and homogenous. The sus- pensory ligament is locked to the ciliary processes by the grooves and projections—like a cog-wheel. Give the Attachments of the Suspensory Ligament. It is attached to— 1. The hyaloid membrane, being a part of it. 2. Inner limiting membrane of retina. 3. Connective tissue of the choroid. What is the Canal of Petit ? It is a triangular space surrounding the lens, between the suspensory ligament in front and the vitreous behind. When inflated with air, it has a sacculated appearance. Describe the Crystalline Lens. Tt lies in a thick strong capsule. It is bi-convex, though more convex behind. In front, we find the iris and aqueous; behind, the vitreous; and round the circumference, the canal of Petit. It is composed of concentric lamin, but these are not continuous all round. The outer portion is soft; the central part is harder. There are faint white lines, three in number, diverging from the centre at angles of 120°; the lines of opposite poles alternate, and are not over one another. In the hardened lens, concentric lamine may be detached like the coats of an onion. 11 How are the Lamine formed ? They are composed of hexagonal ribbon-shaped fibres, with finely serrated edges; the fibres are really elongated cells. They pass in a curved direction from the intersecting planes. How does Age affect the Lens ? In the Farvs, it is almost spherical, vascular (‘“ hyaloid artery”), and reddish in tint, and soft. In the Aputt, the posterior surface is more convex: it is colourless, transparent, and firmer. In Op Acs, it is flattened on both surfaces, yellowish in colour, tougher, and denser. Where is the Aqueous Humour ? It fills the space between the lens and cornea—anterior and posterior chambers. It resembles water, with a little solid matter, chiefly chloride of sodium. In the adult, the two chambers communicate through the pupil. In the foetus, up to seven months, they are separated by the MEMBRANA PUPILLARIS. Describe the Lymphatics of the Eye. 1. Posterior systemM.—The coverings of the optic nerve are like those of the brain— (1) Dura mater. (2) Prolongations of the parietal and visceral layers of the arachnoid, with arachnoid and sub- arachnoid spaces. (3) Pia ‘mater. 12 There are thus two lymph spaces round the optic nerve, continuous with those of the brain. They open into the perichoroidal lymph space, and also communicate with Tenon’s space. 2, ANTERIOR SYSTEM.—Aqueous humour in anterior and posterior chambers is practically lymph. This can flow away, through the “spaces of Fontana” in the ligamentum pectinatum, into the “canal of Schlemm.” What is meant by “ Intra-Ocular Tension” ? The pressure in the eyeball, due to the blood and lymph; the cornea and sclerotic are not extensible, though pressure on the sclerotic of a healthy eye will cause dimpling, as the lymph is forced through the lymph spaces. When the Tension is very much Increased, what is the Condition called ? Glaucoma: the pressure may be so great that the retina is paralysed. What are some of the Signs of Glaucoma? 1. Pressure fails to dimple the sclerotic. 2. Pulsations may be seen in the verns of the retina. What are the Nerves of the Eye? 1. Optic, or nerve of special sense. 2. Also branches of the 6th and 3rd, and sympathetic, through the “lenticular ganglion.” ' 18 What are the Roots of this Ganglion ? 1. Long or sEnsory root—from the nasal branch of the 5th, nerve of common sensation. 2. Short or moror root—from the 3rd (from nerve to inferior oblique) motor to the ciliary muscle, and circular fibres of iris. 3. Sympathetic—motor to blood-vessels, and radiating fibres of iris. From the anterior part of the ganglion ten or twelve ciliary nerves pass to the eyeball. What are the “ Lenses” of the Eye ? 1. Cornea. 2. Aqueous humour. 3. Crystalline lens. 4, Vitreous humour. Are these Distinct in Practice ? No; practically there are only two— 1. Cornea and Aqueous humour. 2. Crystalline lens. The “refractive indices” of the cornea, and aqueous humour are almost exactly the same; there is therefore no refraction worth speaking of at the posterior surface of the cornea. Name the Surfaces where Refraction takes place ? 1, Anterior surface of the cornea. 2. Anterior surface of the lens. 3. Posterior surface of the lens. Lh What is the “ Reduced Eye” ? One without the lens: the lens is not essential for sight, the anterior surface of the cornea would cause sufficient refraction, only one could not see NEAR objects—z.e., only parallel rays could be brought to a focus, divergent rays could not. What ts meant by ‘ Accommodation” of the Hye ? It is the power the eye possesses of adapting itself to vision at different distances; hence, objects placed at various distances from the eye can be seen with almost equal distinctness, not at the same time, but one after the other. It is this special provision, by which the eye is enabled to adapt itself for varying focal distances, that is called “accommodation.” How is this accomplished ? By altering the curvature of the lens. For a distant object, the lens becomes flatter; for a near object, more convex. Which Surface of the Lens undergoes most Change ? The aNnTERIOR surface. How is this Proved ? By means of ‘ Sanson’s images.” edt 15 Explain this. To perform the experiment one must be in a darkened room with a candle. Hold the candle a little to one side of another person’s eye, and then look into the eye from the opposite side. Three images of the candle are seen, two erect and one inverted. The MIDDLE one undergoes most change, as the individual looks at a near or a distant object. How are these Images formed ? At the three refractive surfaces of the eye, viz.:— 1. Anterior surface of cornea : erect. 2. Anterior surface of lens 3. Posterior surface of lens—inverted. The middle one undergoes the most change in accom- modation—z.e., the one formed by the anterior surface of the lens; the others undergo but little change. In what other way may the Experiment be demonstrated ? By the use of the “* Phakoscope.” How ure the Radii of the Curvatures of the Refracting Surfaces calculated ? From measurements of ‘‘ Sanson’s images” by the ophthal- mometer. Name the kinds of Accommodation. 1. NeGative—passive or distant. 2, Positive—active or near. 16 What is meant by “ Near” and “ Distant” ? A NEAR OBJECT is one nearer than 18 feet—the rays from such a object are divergent. A DISTANT OBJECT is one 18 feet or more distant from the eye—the rays from such an object are paraillel. Give the Mechanism of Positive Accommodation. 1. The ciliary muscle contracts. 2. The choroid and ciliary processes are drawn forwards and inwards, 3. This relaxes the suspensory ligament. 4. The anterior surface of lens bulges forwards by virtue of its own elasticity, and thus increases its convexity. Keplain the Mechanism of Negative Accommodation. It is due to the elasticity of the suspensory ligament. When the ciliary muscle is relaxed, the ligament again becomes tense and flattens the anterior surface of the lens. This is the condition of the eyes in sleep, or when they are closed. What ts the Action of Atropine and Physostigmine on Accommodation ? ATROPINE paralyses the filament of the third nerve that supplies the ciliary muscle (the muscle of accommodation), and stimulates the sympathetic; so that the normal eye is unable to see near objects distinctly. Puysostieminz (Calabar bean) has an opposite effect ; but it does not paralyse the dilator, only stimulates the third; and hence near objects alone are seen clearly. 17 State the Conditions that affect the Size of the Pupil ? The pupil contracts— 1. When light falls on the retina—the brighter the light the greater the contraction. 2. In accommodation for near objects. 3. When the eyeball is turned inwards. 4. By the action of certain drugs, as opium, Calabar bean, ete. The pupil pitates— 1. In passing into a dim light. 2, When the eye accommodates for distant objects. 3. Through the action of certain drugs, as atropine. 4. In dyspneea. What is the “Near Point” in Accommodation ? It is the point where the object looked at is most distinct. State the Distance ? In the apuxt, about 10 inches. In the cHiLp, about 3 inches. How can the “ Near Point” be determined and measured ? By means of Scheiner’s experiment. Describe this Experiment. Two small holes are pricked in a card with a pin; these should not be more than a line apart, or at least not exceed i B 18 the diameter of the pupil. The card is held close in front of the eye, and a small needle viewed through the pin holes. Ata moderate distance it can be clearly focussed, but when brought nearer, beyond a certain point, the image appears double or blurred. The point where the needle ceases to appear single is the near point. The distance from the eye is then measured. What is the “ Emmetropic” Eye ? The normal eye—the near point being about 10 inches distant from the eye, the far point 18 feet or over. What are the forms of Long-sightedness ? Two forms— 1. Prespyopia—long sight of old people, due to an error of accommodation. 2. Hypermerrop1a—the naturally long-sighted eye, due to an error of refraction. What is Presbyopia ? The “near point” of vision is removed to more than 10 inches. The focussing of parallel rays not affected. What are its Causes ? It depends on defects in the accommodative mechanism. Its chief causes are— 1. Flattening, and alteration in density of the crystalline lens. 2. Weakness of the ciliary muscle. 19 What ts Hypermetropia ? The “near point” is removed from the eye, as in Presbyopia, but the “far point” is also removed or does not exist—z.¢., even PARALLEL rays are focussed on the retina only by Positive accommodation, and it is not possible to focus DIVERGENT rays—i.e., to see a near object. Here the power of accommodation is good, and the trouble is due to a natural structural defect of the eye—an error of refraction, not of accommodation. What is its Cause ? A structural defect of the eye. The image falls behind the retina, because the antero-posterior axis of the eye is too short and the lens too flat. How is the Defect Overcome ? Both forms of ‘“‘long-sight” are corrected by using CONVEX glasses, which render the rays of light more convergent ; such glasses are specially needed for NEaR objects, as in reading, etc. What is the Effect of Atropine on this Eye ? Under the influence of atropine the hypermetropic eye can see NOTHING clearly, either distant or near, because the ciliary muscle is required to bring even parallel rays to a focus. What ts Myopia ? It is “short-sight,” and exactly the reverse of hyper- metropia: the near and far points are both nearer to the eye. Rays from an object not many feet away are brought to a focus in the vitreous humour. The range of distinct vision is very limited. 20 What is the Cause ? It is due to structural defects. There is an elongation of the antero-posterior of the eyeball, and increased con- vexity of the lens. How is it Corrected ? By the use of concave lenses, which cause the rays of light to diverge; hence, they do not come to a focus so soon. What is Astigmatism ? It is a defect due to unequal curvature of the cornza, the curvature being greater in one meridian than the other. The meridian of greatest curvature is usually at right angles to the meridian of least curvature. Thus vertical and hori- zontal lines, crossing each other, cannot be focussed at once ; one set stands out clearly, while the others are blurred and indistinct. This defect is present to a slight degree in all eyes. Sometimes it may be due to unequal curvature of the Lens. How ws this Defect Corrected ? By the use of cylindrical glasses—z.e., curved only in one direction. What is meant by Spherical Aberration ? One cannot see every point of an object at once with equal clearness. The focus for the middle is not the same as that for the ends; when the ends are seen clearly, the middle part is blurred ; and vice versa. 21 How is this ? The refraction of the rays passing through the circuM- FERENCE of an object is greater than that of the rays traversing its central part: they therefore cannot all come to a focus at ONE point, and hence the blurring. How is this Corrected in Optical Instruments ? By means of ‘a ‘‘ diaphragm,” to shut off the more circum- ferential rays—e.g., as in the microscope, telescope, etc. How ts it Overcome in the Eye ? By means of the iris, which forms a contractile diaphragm, altering its size according to the intensity of the light. Further, the posterior surface of the iris is pigmented, to prevent rays passing through its substance in any part except the aperture of the pupil. The pigment of the choroid and ciliary processes also absorb light, and prevent it being reflected to retina. What is Chromatic Aberration ? The various rays composing white light are not of equal refrangibility—e.g., violet rays are very refrangible, and are brought to a focus sooner than red rays. Hence, a colourless object may seem coloured at its edges; because, if we focus the red rays, the violet are out of focus, and vice verst. What are the Causes of “ Musce Volitantes” ? It may be due to opacity of the vitreous humour, or to specks floating through it (corpuscles in the vitreous humour). It may also be caused by tears or other secretions in front of the cornea. 22 What are the Functions of the Iris? 1. It regulates the amount of light reaching the retina —if the light be intense, it becomes smaller. 2. It changes in size in accommodation, and thus lessens spherical aberration by cutting off the peripheral rays of light. What are the Nerves of the Iris ? 1. SympatHetic to the dilator pupille.—Its centre is always in action and is automatic; its probable position is in the floor of the front part of the aqueduct of Sylvius. 2, The Turrp nerve to the sphincter pupille.— Its centre is reflex, and is probably placed in the corpora quadrigemina. Give the Course of the Sympathetic to the Iris ? It resembles that of vasomotor nerves in general. From its centre in the aqueduct of Sylvius it passes down the spinal cord, and leaves by the last cervical and first dorsal nerves; it then passes up the cervical sympathetic, and emerges from the upper cervical ganglion into the ophthalmic division of the fifth nerve, where it joins the nasal branch, and then passes through the long ciliary nerves to the radiating fibres of the iris. Hence division of the long’ ciliary nerves, of the nasal, of the trunk of the sympathetic in the neck, and the cervical part of the spinal cord—the dilator is paralyzed. A tumour in the neck, pressing upon the sympathetic, may piwatTE the pupil because ib irritates the sympathetic ; but if it presses too much, then the nerve is paralyzed, and great contraction is the result. 23 Give the Course of the Third Nerve to the Iris. It passes from the centre in the corpora quadrigemina into the trunk of the third, through the short root of the ophthalmic, and from this through the short ciliary nerves to the circular fibres of the iris. Why does the Pupil contract when the Eye is turned inwards? Because the third nerve supplying the muscle also supplies the sphincter, and the stimulus “spreads” to the sphincter centre. How can Purkinje’s Figures be shown ? Go into a dark room, having its walls covered with grey paper, and move a candle to and fro at the side of and close to one eye, while the eyes look steadily forwards into the darkness. Remarkable branching figures, like the roots of trees are then seen floating before the eyes, like dark lines on a reddish ground. These are ‘“ Purkinje’s figures,” and are the shadows of the retinal blood-vessels. The light entering the eye obliquely throws the shadows of the retinal blood-vessels on the sEEInG Part of the retina— the rods and cones. What is the Significance of these Figures ? It is a proof that the light-perceiving elements of the retina must be BEHIND those vessels, and therefore not in the fibres of the optic nerve, but some of the external layers of the retina, probably the rods and cones. 24 How may the “ Yellow Spot” be seen in one’s own Eye ? By looking into a solution of chrome alum. On looking into this solution a reddish spot is seen, because the yellow pigment of the macula lutea absorbs the greenish-blue rays, but the red pass through to Jacob’s membrane. Whose Method is that ? Clark Maxwell’s. Which is the most Sensitive Part of the Retina ? The “yellow spot.” If we wish to see any object very clearly, we always try to look straight in front so as to focus it on the yellow spot. It is about 150 times as sensitive as any other part of the retina. What is the Blind Spot ? The “blind spot,” or the optic disc, is that part of the retina where the optic nerve enters. This spot consists entirely of optic nerve fibres, and therefore these fibres are insensible to light. How can this Spot be demonstrated ? By means of Mariotte’s experiment. Describe this Experiment. ih e (Close left eye and look at the cross.) Fix one eye on the cross and close the other, and then move the dot sideways over the paper towards the outer side of the field of vision. The dot is first seen, then it disappears for some time (because focussed on the “blind spot”), and is then seen again as the paper is slowly moved in the direction indicated. 25 What is the Duration of a Retinal Impression ? qoth part of a second. How ts this Proved ? By means of a white spot on a revolving disc. Tum slowly, the spot can be seen quite well. Turn rapidly, only a grey circle is seen because the spot comes round to its former position in less than ;,th part of a second. What ts meant by “ After-Images” ? After-images may be— 1. Positive.—Look at a window for a second, and then close the eyes; if of the same colour as before, then it is a positive after-image. 2. Necative.—lIn this case the after-image is changed in colour—e.g., look at the sun and then close the eyes, a BLACK image is seen. Wheat is the “ Visual-Purple” ? It is a reddish-purple tint, seen in the outer segments of the rods. How does Light affect this ? Light bleaches it; it is quickly restored in the dark by the hexagonal pigment cells. Throw a bright light in the form of a cross on the retina of an animal, and then rapidly kill and examine. A bleached cross is seen in the visual purple of the outer segments of the rods. 26 Is this Essential to Vision ? No; because vision is most acute where there is no pigment—i.e., at the ‘“‘yellow spot.” How does Light affect the Electrical Current of the Retina? It causes a “negative variation” to take place; at first, however, there is a slight positive variation, but this quickly becomes negative. The effect varies directly with the intensity of the stimulus. Give Reasons for believing that the Rods and Cones are the parts affected specially by Light? The evidence of— 1. The blind spot. 2. Macula lutea. 3. Purkinje’s figures. 4, Changes produced in Jacob’s membrane by light. What ts Colour ? Colour is a sensation, and not a property of light. Only those rays of light which have a medium wave length stimulate the retina. The red rays are the longest (heating rays), while those at and outside the violet end of the spectrum are the shortest. What are the “ Primary” Colours ? 1. Red. 2. Green. 3. Violet. All the other colours are only mixtures of these in varying proportions; a proper mixture of all = WHITE. Each of these three primary colours probably have special nerve endings (Young-Helmholtz theory). 27 What are the Vurieties of Colour-Blindness ? 1. For Red (Daltonism). 2. For Green. 3. For Violet. In Red, for example, the special nerve endings for the red rays are wanting, and hence white seems a bluish-green, and a red object dark-green; in this case, a cherry is known among green leaves only by its shape. What other Points support the Young-Helmholtz Theory ? The peripheral parts of the retina have no perception of red; and the area of the retina, which is capable of receiving impressions of colour, is slightly different for each colour. Are the other forms of Colour-Blindness common ? No; Green and Violet blindness are very rare. Santonin causes violet blindness, as it paralyzes the violet nerve end- ings for the time being. At first everything seems violet, and after this becomes yellowish. Compare the Functions of the Rods and Cones? The Rops enable us to determine the zntensity of the light—distinguish light from dark, or night from day. The Congs enable us to perceive Conour sensations— (Note Cones and Colour). What are the Axes of Movement of the Eyeballs ? 1, An Antero-posterior. 2. A Vertical. 3. A Horizontal. 28 Give the Movements of the Eye and the Muscles causing them. Superior rectus pulls up and in. Inferior oblique pulls up and out. —Acting together, pull straight up. Inferior rectus pulls down and in. Superior oblique pulls down and out. —Acting together, pull straight down, External rectus pulls directly outwards. Internal rectus pulls directly inwards. All the other movements are but combinations of the above four. ELEVATION { DEPRESSION \ How are the Eyelids Opened and Closed ? Opened by the levator palpebree (3rd nerve). Closed by the orbicularis (facial nerve). Give the Structure of the Eyelids. 1. Skin. 2. Orbicularis muscle. 3. Loose connective tissue. 4. Tendon of levator palpebre (in upper lid only). 5. Tarsal cartilage, into anterior surface of which the levator is inserted. . Palpebral ligament. 7. Meibomian glands. 8. Conjunctiva—palpebral part. a What are the Parts of the Lachrymal Apparatus. 1, Lachrymal gland and its ducts. 2. Puncta lachrymalia, the openings of the 3. Canaliculi, which leads into 4, Lachrymal sac, from which the 5. Nasal duct descends to open into the inferior meatus of the nose. 29 What are the Secretory Nerves ? 1. Sympathetic—secretion, viscous and small in quantity. 2, Lachrymal branch of the 5th—secretion, watery and profuse (ordinary tears). What Nerves supply the Extrinsic Muscles of the Eyeball ? External rectus by 6th nerve (abducens). Superior oblique by 4th nerve (trochlearis). All the other muscles are supplied by the 3rd (motor oculi), viz. — . Levator palpebree superioris. . Superior rectus. . Internal rectus. . Inferior rectus. oR WwW LD oe . Inferior oblique. THE EAR. Describe the External Auditory Meatus. Length, 1} inch: the lower wall is the longer, because of the oblique direction of the membrana tympani. It passes obliquely forwards and inwards, and is curved upon itself, the concavity pointing downwards, so that the floor is convex. In shape it is oval, with the long axis vertical, and it is narrowest about the middle. Rather less than one-half its length is formed of cartilage, the rest of bone. Describe the Appearance of the Membrana Tympani. It is transparent, and is smooTH and SHINING, and of a slate-blue colour; it is concave from the outside. Shining 30 through it, we also see the handle and short process of the malleus, and the “triangle of light” on its surface. Give the Structure of the Membrane. It consists of three layers— 1. The ovrsr or cuticular layer, a continuation of the skin of the meatus. 2. The InTERNAL or mucous layer, which is continuous with the mucous membrane of the tympanic cavity. 3. The mrppis or fibrous layer, consisting of connective tissue fibres arranged both radially and circularly— (1) The radial are the more numerous, and radiate from the point of attachment of the handle of the malleus. (2) The circular form a dense ring near the circumfer- ence, and are lodged in a bony groove which is deficient at the upper part (‘notch of Rivinus”). The layer itself is also defective above; and here, therefore, the membrane con- sists only of the cuticular and mucous layers —the ‘membrana flaccida,” or Shrapnell’s membrane. Describe the Middle Ear or Tympanum. It is a small six-sided cavity, situated in the substance of the temporal bone, filled with air, and containing three small bones. It communicates with the pharynx by means of the Eustachian tube. It is placed aBove the jugular fossa: in FRONT, we find the carotid canal, with the internal carotid artery; BEHIND, the mastoid cells, and the internal jugular vein; EXTERNALLY, the membrana tympani; and INTERNALLY, the labyrinth. 31 Give the Boundaries more fully. 1. The Roor.—A thin plate of bone and dura mater. 2. The Fioor.—Meeting of the outer and inner walls, just above the jugular fossa. There is a small aperture in it for the entrance of “Jacobson’s nerve” (from the glosso- pharyngeal). 3. The OureR WALL is the membrana tympani.—At the lower part are three openings—the ‘‘Glaserian fissure,” which gives passage to the laxator tympani muscle, the tympanic vessels, and lodges the processus gracilis of the malleus; and the iter chordce posterius et anterius, being the aper- tures of entrance and exit of the chorda tympani nerve. The iter chorde anterius is the beginning of the “canal of Huguier.” 4. The INNER waLL.—Note (1) Fenestra ovalis—a depression which leads to the vestibule, but which is closed by a membrane similar in structure to the membrana tympani. The depression is occupied by the base of the stapes. (2) Fenestra rotunda—leads to the scala tympani of cochlea, and is also closed by a membrane of similar structure. (3) The Promontory—caused by the first turn of the cochlea, and grooved by the nerves of the tympanic plexus. (4) A bulging, caused by the aqueductus Fallopii, which lodges the facial nerve. (5) The Pyramid—containing the stapedius muscle, and has a small opening at its apex for the exit of its tendon; also a small canal for the nerve to the stapedius (from the facial). 32 5. Posterior waLL.—The openings of the mastoid cells. 6. ANTERIOR wALL— (1) Canal for tensor tympani. (2) Processus cochleariformis. (3) Eustachian tube. Name the Contents of the Tympanum. 1. Air. 2. Chain of ossicles—malleus, incus, and stapes. 3. Muscles acting on the ossicles. 4, Chorda tympani nerve. Describe the Course of the Chorda Tympani. It crosses the cavity from back to front, close to the outer wall, between the handle of the malleus and the long process of the incus, being invested by a fold of the mucous membrane, forming the most internal layer of the membrana tympani—the iter chorde posterius and the iter chorde antertus being its apertures of entrance and exit. Describe the Eustachian Tube. It is from 14 to 2 inches in length, and its direction is downwards, forwards, and inwards. It consists of— 1, An osszovus part, about half-an-inch in length, situated in the temporal bone. 2. The cartilaginous part is about an inch in length, is A-shaped, and composed of yellow elastic fibro-cartilage. The open part below is completed by a fibrous membrane, and a layer of voluntary muscle. It is lined by ciliated epithelium : it is usually closed, but is opened at the moment of swallowing by the DILATOR TUBA. 33 What is the “ Dilutor Tube” ? It is a part of the tensor palati, both muscles contracting together. What are the Uses of the Eustachian Tube ? To get rid of the secretions from, and to ventilate the tympanic cavity. By its means the pressure of air in the cavity is kept the same as in the external auditory meatus, so that the pressure on the two sides of the membrane is the same, a condition necessary for the clear perception of sound waves. How is Sound transmitted in Birds ? It is transmitted from the membrana tympani through a single ossicle, the columella, to the “fenestra ovalis,” where it is communicated to the fluid of the inner ear. Why should Sound not be transmitted directly from Air to Fluid ? It is very difficult to transmit sound from air to solids or fluids directly. The membrana tympani, however, is easily thrown into vibrations by sound waves, which it transmits to the ossicles, and they in turn to the fluid of the inner ear. Further, the sound waves are concentrated, as the membrana tympani is larger than the membrane covering the “ fenestra ovalis.” What are the Bones of the Mammalian Ear ? 1. Mattevs (hammer), with its head, neck, handle, and processus gracilis. c 34 2. Incus (anvil), like a bicuspid tooth with the fangs widely separated. It has a body, with a long and a short process. The long process ends in the os orbiculare, and through this articulates with stapes. 3. Stapes (stirrup), with its head, neck, base, and two erura: the base fits the ‘fenestra ovalis.” Describe the Incus-MMalleus Joint ? It is diarthrodial and saddle-shaped, with capsular liga- ment. When the handle of the malleus is drawn in, this joint is locked and the bones vibrate as one. The lower margin of the articular surface of the incus has a well- marked projection, which catches against the prominent border of the articular surface of the malleus; in this way the joint is locked, when the membrana tympani moves inwards. When the handle of the malleus is moved out too much, the joint is UNLOCKED, so that the incus need not follow, but the malleus moves outwards alone, and this prevents the stapes from being dragged out of the “fenestra ovalis.” What Muscle lochs this Joint ? The tensor tympani, this being the special function of this muscle ; it contracts, when the ear is strained to hear faint sounds. Why is the Membrana Tympani Curved ? It is to enable it to vibrate to a greater variety of tones. It can take up an immense range of tones, produced by vibrations ranging from 30 to 5000 per second. This would be impossible were it an evenly stretched membrane. 35 Give the Origin and Insertion of the Tensor Tympani ? Jt arises from the apex of the petrous portion of the temporal bone, and cartilage of the Eustachian tube ; it is inserted into the handle of the malleus near its root. What is its Nerve ? A twig from the 5th, through the otie ganglion. Give the Origin and Insertion of the Stapedius. It arises within the pyramid, and is znserted into the neck of the stapes. Nerve—from the facial. What is its Function ? It tilts out one part of the foot of the stapes, and thus lessens its amplitude of vibration ; and in this way protects the internal ear from painful stimulation by loud sounds. Name the Nerves of the Tympanie Plexus. 1. The tympanic branch of the glosso-pharyngeal (Jacob- son’s nerve). 2. A twig from the carotid plexus of the sympathetic. 3. A twig from the great superficial petrosal. 4. It sends a twig, also, to join the lesser superficial petrosal. 36 How may the Tympanum be Inflated ? 1. Vausatya’s MeTHoD.—Hold the nose between the finger and thumb of one hand, close the mouth and expire forcibly as in “ blowing the nose,” and try to swallow at the same time, as this opens the tube. 2. Potirzer’s metHop.—This method depends on the fact, that during deglutition the opening from the mouth into the upper part of the pharynx and posterior nares is closed, while at the same time the Eustachian tube is opened by the dilator tubce. During swallowing, therefore, air is forcibly introduced into the nose by means of an air-bag. This increases the pressure, and some is forced up the Eustachian tube. What are the parts of the Internal Ear or Labyrinth ? 1. OssEOUS LABYRINTH—consists of (1) Vestibule. (2) Semi-circular canals. (8) Cochlea. 2. MEMBRANOUS LABYRINTH—consists of (1) Utricle and saccule (in vestibule). (2) Membranous semi-circular canals. (3) Cochlear canal. And tubes connecting these parts, viz.— Ductus Vestipuui and Canauis Reuniens. “Ductus vestibuli” connecting the utricule and saccule ; the “canalis reuniens” connecting the saccule with the membranous cochlea (scala media). 37 OSSEOUS LABYRINTH. What is the Osseous Labyrinth ? It consists simply of cavities scooped out of the temporal bone, and lined by a thin membrane. What are its Contents ? It contains perilymph, and the membranous labyrinth, which contains endolymph. What are the Communications of the Vestibule ? In FRONT, with the cochlea (scala vestibuli). Bean, the semi-circular canals (five openings). OUTER siDz, the tympanum. INNER SIDE, meatus auditorius internus. Describe its Walls. Its OUTER WALL is perforated by the “fenestra ovalis.” On the InNER watt, note the fovea hemispherica, with many small perforations for the auditory nerve: the crista - vestibuli, and behind it an opening—the aqueductus vesti- buli (this last transmits a small vein). In the Roor, note the fovea hemi-elliptica. 38 What are the Semi-Circular Canals ? Three bony tubes above and behind the vestibule— named superior, posterior, and external; they are placed in three planes of a cube. The superior and posterior blend at one end; they are ampullated at one end, lined by endosteum, covered by endothelium, and contain peri- lymph. The superior and posterior are both equally inclined to the middle line, and the superior of one side is parallel, in direction, with the posterior of the other. Describe the Cochlea. It consists of a central axis or modiolus, and a canal wound for 24 turns round it. The canal ends in a cul-de- sac, the cupola; in the middle is the osseous spiral lamina, partially dividing it into two, the division being completed by a membrane (basilar). In this way two compartments are formed, the scula tympani and the scala vestibuli. The two scala communicate at the apex through the helicotrema. The basilar membrane is attached to the outer wall of the tube by the spiral cochlear ligament. The periosteum at the end of the osseous spiral lamina is thickened into a denticulate crest, C-shaped in section = limbus lamine spiralis, This ends in a grooved border, the sulcus spiralis. From the limbus a membrane arises, the ‘‘membrane of Reissner,” and stretches across to the outer wall of the cochlea, dividing the scala vestibuli into two—scala vestibuli and scala media or (membranous cochlea), The membrana tectoria also springs from the extremity of the limbus. 39 MEMBRANOUS LABYRINTH. What ts the Membranous Labyrinth ? It is much smaller than, and lies in the osseous labyrinth, and contains endolymph. Describe the Vestibule. It consists of UTRICLE and SACCULE,— The wéricle is the larger, and into it open the semi-circular canals; it occupies the fovea hemi- elliptica. The saccu/e lies in the fovea hemispherica; it is connected with the membranous canal of the cochlea by the ‘“canalis reuniens.” The utricle and sacculi are connected not directly, but by means of a Y-shaped tube, the aqueeductus vestibuli. Describe the Semi-Circular Canals. They are about one-third the size of the osseous; one side is fixed to the wall of the bony canal, and the other side (concavity) is free. What is their Structure ? 1. An outer fibrous layer continuous with the periosteum. 2. Tunica propria, a clear glassy continuous membrane. 3. A layer of flattened epithelial cells. 40 Describe the Cochlea, This is the “scala media.” It ends in a blind pointed extremity, and follows the windings of the osseous tube. Near its base it receives the canalis reuntens from the saccule. It is somewhat triangular in shape being bounded by— 1. The basilar membrane, below. 2. The membrane of Rezissner, on the inner side. 3. The outer osseous wall of the cochlea, externally. What Special Structure is found upon its Floor ? The “organ of Corti” (see page 42). Give the Structure of the Basilar Membrane. From below upwards, we find— — . An endothelial layer. Ww . Hyaline basement membrane. 3. Striated membrane. 3 4, Hyaline basement membrane, just below the ‘‘ organ of Corti.” Describe the Vestibular part of the Auditory Nerve. lt divides into five parts, going to the utricle, saccule, and the three ampulle of the semi-circular canals, and ends in the “auditory cells.” The ampulle, saccule, and utricle agree in structure with the canals (see page 39); but at the part where they are connected with the osseous 41 wall there is a thickening or projection into the lumen, the “crista acustica.” At this. part the epithelium is columnar, and between the cells are other spindle-shaped cells ending in delicate hair-like processes, which project into the endolymph=‘“ auditory cells.” These cells are in direct communication with the auditory nerves. In con- nection with these hair cells are the ofoliths or otoconia ; these consist of crystals of carbonate of calcium embedded in a jelly, and the whole surrounded by a delicate limiting membrane, called the cupula. The hair cells project into the jelly, and touch the otoliths. What are the Parts of the Invertebrate Ear ? The saccule and utricle correspond to the invertebrate ear—a little sac with jelly, otoliths, hair cells, and nerve fibres. Otoliths are always present. What is the Function of the Otoliths ? To stimulate the auditory hair cells more rapidly: the jelly acts as a ‘‘damper,” and controls the vibrations. What is the Structure of Reissner’s Membrane ? A layer of connective tissue, covered on both sides by a layer of endothelium. What ts the Ligamentum Spirale ? It attaches the basilar membrane to the outer wall of the cochlea, and is a modification of the periosteum. 42 Name the Parts of the Organ of Corti. 1. Rods, or pillars of corti (between them the “arch of Corti”). 2. Inner hair cells (one row). 3. Outer hair cells—‘ cells of Corti” (three or four rows) with cells of Deiters. 4. Reticular membrane. 5. Supporting cells of Hensen. 6. Membrana tectoria. Give the Course of the Nerve to the Organ of Cortt. It is the cochlear division of the auditory. It passes through a canal in the modiolus, and then through a gap in the osseous spiral lamina and is distributed to the hair cells of the organ of Corti. In the canal of the modiolus we find the ganglion spirale, and many nerve cells in the tunnel of Corti. Describe the Course of the Sound Waves. The sound waves throw the membrana tympani into vibration : the vibrations are conducted across the tympanic cavity by the chain of ossicles, and are then communicated to the perilymph by the stapes. The wave then passes over the vestibule and semi-circular canals, into the scala vestibuli of the cochlea through the helicotrema, down the scala tympani, and ends as an impulse against the fenestra rotunda. The wave in its passage throws the basilar membrane, with its super-imposed “organ of Corti” and endolymph, into vibration; and thus gives rise to nerve impulses, that pass up to the brain and produce auditory sensations. 43 How may Sounds be Divided ? Into— 1. Noises. 2. Musical sounds. hat are the Essential Parts of the Organ of Hearing ? 1. The membranous vestibule (utricle and saccule) with its crista acustica, auditory hair cells, and otoliths. This part enables us to appreciate the sENsE of sound —its intensity and quantity, low or loud—but no discrimination as to QUALITY. 2. The scala media of the cochlea, with the organ of Corti. This part enables us to discriminate the quauity of sound: sounds are analysed in the cochlea, as the various musical sounds. Both the essential parts are bags filled with fluid, supported in a fluid. What is probably the Essential Part of the Organ of Corti ? Probably “ Corti’s cells” —outer hair cells; and the membrana reticularis acts the part of a ‘“ damper.” State the Conditions of the Ear in some of the Lower Vertebrates. In myxinoid fishes there is a vestibule and one semi- circular canal. The lamprey has two canals; other fishes, three. In amphibia, reptiles, and birds there is a rudimentary cochlea, but there are no rods of Corti. 44 In what other ways can Sounds reach the Lar ? Through the bones of the head—e.y., a tuning-fork, or the audiophone to the teeth. What is the supposed Use of the Semi-circular Canals ? They are probably the peripheral end organs of the “sense of rotation.” As to how this is accomplished there are two theories— 1. Statical theory (Goltz). 2. Kinetic theory (Crum-Brown). What is the Result of Division of the Canals? The head is moved in the direction of the plane of the canal cut, and there is a want of co-ordination of muscular movements. On what does the Sense of Equilibrium depend ? 1. The tactile sense. 2, The muscular sense. 3. The sense of sight. +. The sense of rotation. NERVOUS SYSTEM. Name the End Organs for the Senses of Touch and of Temperature ? 1. TactinE corPusciEs, as in the skin of the hand and foot, front of fore-arm and nipple. 2. Exp sBuxgs, only in mucous membrane, as the con- Junctiva, mouth, and glans penis. 3. Pacryian corpuscrss, as in the digital nerves. 4. Purxuses, The nerve end organs are always covered with epithelium. 45 How do we judge of Tactile Sensations ? These are judged by the smallest weight that can be felt. How ts the Acuteness Tested ? By the power which the part possesses of distinguishing and isolating the sensations produced by two points placed close together—e.q., the points of a pair of compasses. What is the Muscular Sense ? It is the power of perceiving the condition of the muscles—e.g., in raising a weight, one is conscious of over- coming a certain resistance, and is able to put forth just enough muscular contraction necessary for lifting the weight in question. Without this sense one would be unable to co-ordinate muscular movements. How is Weight Estimated ? 1. By the pressure upon the skin. 2. By the muscular sense. CEREBRO-SPINAL NERVES. What are the Functions of the two Roots of a Spinal Nerve ? Anterior root, Moror. Posterior root, SENsury. 46 How, and by whom was this proved ? By Sir Charles Bell. 1. By Currinc— (1) The anterior root: motion lost, but sensation unaltered. (2) The posterior root: sensation lost, but power of movement remains. (3) Both roots: sensation and motion both lost. 2, By STIMULATING (1) The peripheral end of cut posterior root: neither motion nor sign of pain. (2) Central end of cut posterior root: signs of pain. (3) Peripheral end of cut anterior root ; movement in muscles below, but no sign of pain. (4) Central end of cut anterior root: no movement in muscles below. What is meant by “ Recurrent Sensibility” ? In stimulating peripheral end of cut anterior root, there are signs of pain if the posterior root be intact. This is spoken of as “recurrent sensibility,” as it is probably due to “recurrent” fibres passing from anterior root upwards along the posterior root to the cord. Pain is felt even though the nerves of the muscles be cut, and therefore could not be due to muscular spasm. How are the Functions of Nerves discovered ? 1. By their anatomical distribution, as in dissection— e.q., the long buccal nerve. 2. Experiments on animals— (1) By cutting. (2) By stimulating the cut ends. 3, From a study of the results of injury or disease. AT CRANIAL NERVES. Classify the Cranial Nerves according to Function. SENsoRY— Olfactory (smell). Optic (sight) Auditory (portio mollis of 7th). Motor— Third nerve (oculo-motor). Fourth nerve (trochlear, for superior oblique). Sixth nerve (abducens, to external rectus). Facial nerve (portio dura of 7th). Spinal accessory (gives motor root to vagus). Ninth nerve (hypo-glossal). Mixep— Fifth nerve (trifacial). Glosso-pharyngeal. Pneumogastric or vagus (motor root from spinal accessory), ° Give the Functions of the First and Second Nerves. The First, or Olfactory, for the special sense of smell. The Srconp, or Optic, for the special sense of sight. There is a partial decussation of this pair at the optic commissure; the nerve then passes through the optic foramen, pierces the sclerotic and choroid, and expands into the retina. 48 Give the Course and Function of the Third Nerve. 1. It is motor to various muscles of the eye (motor-ocul?). It pierces the dura mater close to the posterior clinoid process, and runs forwards in the outer wall of the cavernous sinus. It divides into two parts, and enters the orbit between the two heads of the external rectus, the two divisions being separated from each other by the nasal nerve. The upper branch supplies— 1. The superior rectus. 2. The levator palpebre. The tower branch supplies— 1. The internal rectus. 2. The inferior rectus. 3. The inferior oblique. From the branch to the inferior oblique passes the motor root of the ciliary ganglion, and through that, fibres pass to the circular fibres of the iris and ciliary muscle. The nerves enter the muscles (extrinsic) on their ocuLaR surfaces. State the Effect of Paralysis of this Nerve. 1. Ptosis — upper eyelid droops, because the levator palpebree is paralyzed. 2. External strabismus, as the internal rectus is paralyzed. 3. Double vision. 4. Dilatation of the pupil. _ 5. Loss of positive accommodation, as the ciliary muscle is paralyzed. 6. Movements of the eye very limited. 7. Eyeball slightly more prominent, due to the action of the superior oblique. 49 Describe the Course and Function of the Fourth Nerve. Tt enters an opening in the free border of the tentorium © near the posterior clinoid process, and passes forwards in the outer wall of the cavernous sinus, through sphenoidal fissure, and enters the superior oblique on its ORBITAL surface. What is the Result of its Paralysis ? ‘When one turns the head round, there is double vision, as the superior oblique is not acting. What ts peculiar about the Fifth Nerve ? It is the largest cranial nerve, and is said to resemble a spinal nerve. As it consists of two roots, motor and sensory, and the sensory has a ganglion upon it. It is also called the “ trifacial.” Describe the Course of this Nerve. It passes forwards to the middle fossa of the skull, and through a recess in the dura matter, near the apex of the petrous portion of the temporal bone. At this point there is a ganglion (the Casserian), from the anterior part of which the three divisions of the nerve pass— 1. Ophthalmic division. 2, Superior maxillary division. 3. Inferior maxillary division. The anterior root is not connected with the ganglion, but passes beneath it and then through the foramen ovale, and joins the inferior maxillary division. D 50 Describe the Ophthalmic Division. It passes through the sphenoidal fissure into the orbit, communicates with the fourth and sympathetic, and gives recurrent branches to the dura mater. It is a PURELY SENSORY nerve. What are its Branches ? It gives off first— 1. The nasal branch, and then divides into 2. Lachrymal, to lachrymal gland. 3. Frontal, which divides into (1) Supra-trochlear. (2) Supra-orbital. What are the Branches of the Nasul Nerve. _ Long root of ciliary ganglion. Two long ciliary nerves. Infra-trochlear. Branch to nasal septum. Superficial branch (external). St py Se tS Where does this Division appear on the Face ? 1. As supra-orbital. 2. As supra-trochlear. 3. Nasal. Give the Course of the Superior Maxillary Division. It passes through the foramen rotundum, crosses the spheno-maxillary fossa, enters a canal on the floor of the orbit, and appears on the face as the infra-orbital nerve. It is a PURELY SENSORY nerve. 51 What are its Branches ? 1. In the SPHENO-MAXILLARY FossA— (1) Orbital, dividing into (a) Temporal. (b) Malar. (2) Spheno-palatine, to Meckel’s ganglion. (3) Posterior dental. 2. In InrrRa-oRBITAL CANAL— (1) Middle dental. (2) Anterior dental. 3. On the Facs— Palpebral, nasal, and labial branches. What Branches of this Division appear on the Face ? 1. Infra-orbital. 2. Subcutaneous male. 3. Temporal branch. Give the Course of the Inferior Maxillary Division. This is the largest of the three; it passes through the foramen ovale, and is then joined by the motor root, and after that divides into an anterior and posterior division. It is both motor and sensory. What are its Branches ? 1. Small or Anterior division (chiefly motor). (1) Masseteric. (2) Deep temporals (two). (3) Pterygoids (two). (4) Long buccal. 52 2. Large or Posterior division (chiefly sensory). (1) Auriculo-tem poral. (2) Inferior dental, giving off branch to mylo- hyoid and anterior belly of digastric. (3) Lingual, to anterior two-thirds of tongue. What Branches of this Division appear on the Face ? 1. Auriculo-temporal. 2. Long buccal. 3. Mental (branch of inferior dental). Give the Functions of the Fifth Nerve. 1. Motor to— (1) Muscles of mastication. (2) Mylo-hyoid and anterior belly of digastric. (3) Tensor tympani. (4) Tensor palati. 2. CoMMON SENSATION to— Scalp, face (except over parotid gland), nose, con- junctiva, and iris. Cavity of the mouth (except the posterior third of tongue), and external auditory meatus. 3, SECRETORY to— The lachrymal gland. What ure the Results of its Paralysis ? 1. The muscles of mastication, and the other muscles supplied by this nerve, are paralyzed. 2. Hearing is impaired, because the tensor tympani is paralyzed. 3. Loss of sensation in the various parts supplied. 53 4. Atrophy of the muscles of expression (motor nerve == 7th)—probably due to loss of trophic influence, because they are cut off from the Casserian ganglion. 5. Destructive inflammation of the eyeball from the same cause, and also because of the loss of sensation, so that particles of dust, etc., are not felt. Give the Course and Function of the Sixth Nerve. It runs forwards in the wall of the cavernous sinus, resting on the internal carotid artery, through the sphenoidal fissure to the external rectus. Result of paralysis—internal squint. Give the Course of the “ Portio Dura” of Seventh (Facial). It enters the internal auditory meatus lying above the portio mollis, then into the aqueduct of Fallopius, and makes its exit at the stylo-mastoid foramen. It first passes ouTWarps, then BAcKWaRDS, forming the knee-shaped bend, where it has a gangliform enlargement (the geniculate ganglion), and then passes straight down. What are its Branches ? 1. In the Meatus, it communicates with the portio mollis by two filaments. 2. In the AquEDUcT— (1) Great superficial petrosal to Meckel’s ganglion, and through that to the azygos uvule and levator palati. (2) Small superficial petrosal to the otic ganglion: conducts the secretory fibres to parotid gland. Both these come from the geniculate ganglion. 54 (3) External superficial petrosal. (4) Nerve to stapedius muscle. (5) Chorda tympani to tongue, submaxillary and sublingual glands. 3. At its exit from the stylo-mastoid foramen— (1) Posterior auricular to retrahens, and posterior belly of occipito-frontalis. (2) Digastrie (posterior belly). (3) Stylo-hyoid. 4, On the Facze— (1) Temporo-facial— Temporal. Malar. Infra-orbital. (2) Cervico-facial— Buccal to buccinator. Supra-maxillary. Infra-maxillary. These branches supply the muscles of expression— about eyes, nose, mouth, cheeks, also the platysma. vive the Functions of the Seventh Nerve ? 1. Motor to— (1) Levator palati (2) Azygos uvula (3) Stapedius. (4) Stylo-hyoid. (5) Posterior belly of digastric. (6) Muscles of expression. \ through Meckel’s ganglion. 55 2, SECRETORY to— (1) Secretory fibres of the parotid pass through the small superficial petrosal, but probably come from the glosso-pharyngeal. (2) Submaxillary Ral, (3) Sublingnal ioe chins t i. (4) Glands on dorsum of tongue ee 3. SENSORY— Special sense of taste, to the anterior two-thirds of tongue. What are the Results of its Paralysis ? 1. The wrinkles disappear from the brow. 2. The eyelids cannot be closed. 3. The lower lid falls down, the punctum is drawn away ‘rom the globe, and the tears run over the cheek. 4, Mouth and face drawn to sound side. 5. The nostrils cannot be dilated. 6. The food passes between the teeth and the cheek, yecause the buccinator is paralyzed; the cheek is flabby and alls in, and may be bitten. 7. One cannot whistle or laugh properly, and angle of nouth is depressed. 8. Posterior belly of digastric and stylo-hyoid muscles we paralyzed. 9. Loss of taste in anterior two-thirds of tongue, because the chorda is paralyzed. 10. Hearing is affected, because of the stapedius. 11. The mouth is dry, because the salivary glands (sub- naxillary and sublingual) are not secreting. 12. The palate falls down on the paralyzed side, because he levator and azygos uvule muscles are paralyzed, and ivula points to healthy side. 56 Give the Course and Distribution of the Portio Mollis of the Seventh (Auditory ). It passes along with the facial into the internal auditory meatus, but lying below it, while between the two is the auditory artery. At the bottom of the meatus it divides into the cocHLEAR and VESTIBULAR divisions, which pierce the cribriform lamina and pass to the cochlea and vestibule. (See ‘“ Ear.”) Name the three Divisions of the Eighth. 1. Glosso-pharyngeal. 2. Pneumogastric, or vagus. 3. Spinal accessory. Give the Course of the Glosso-Pharyngeal. It passes over the ‘“‘flocculus” to the jugular foramen, and passes through it enclosed in a separate tube of dura mater, anterior to the other two parts and internal to jugular vein. It has two ganglia— 1. Jugular, only involving part of the nerve. 2. Petrous, involving the entire nerve, and from this comes Jacobson’s nerve. Give its Distribution. 1. Tympanic (Jacobson’s nerve)—common sensation to labyrinth and tympanic cavity. It enters the tympanic cavity through its floor, and has three communications— (1) Sympathetic. (2) Great superficial petrosal. (3) Small superficial petrosal. 57 And three places of distribution— (1) Foramen ovale, (2) Foramen rotundum. (3) Tympanum. Carotid branches, to carotid plexus. . Muscular to stylo-pharyngeus and constrictors. Pharyngeal branches to plexus of that name. Branches to tonsil. Lingual to sides and base of tongue, common sensa- tion and special sense of taste to posterior third of tongue, and taste to anterior pillars of fauces and soft palate. 7. It is also the nerve of secretion for the parorip gland. PoP ws What are the Results of tts Paralysis. 1. Loss of sensation (common and special) to parts named above. _ 2. Deglutition is impaired, though not stopped, because of the presence of the lingual filament of the superior laryngeal branch of the vagus; also palatine branches of the fifth. 3. Parotid nerve of secretion paralyzed. Give the Course of the Pneumogastric or Vagus. It is the longest cranial nerve. It passes across the flocculus to the posterior part of the jugular foramen, and passing through, it is then joined by the inner division of the spinal accessory (this forming the motor root of the vagus). It has two ganglia— 1. Ganglion of the root, in the jugular foramen: from this the awricular branch (Arnold’s nerve) springs. 2. Ganglion of the trunk, just below the fossa. It has many communications and gives off— (1) Pharyngeal branch. (2) Superior laryngeal nerve. 58 Give the Branches of Distribution. 1. AuRicuLAR BRaNcH (Arnold’s nerve)—common sensa- tion to skin behind auricle, also to the external auditory meatus. 2. PHaRYNGEAL BRANCH — motor chiefly to the stylo- pharyngeus and palato-pharyngeus, and perhaps partly to constrictors. 3. SupEeRIon LaryNGEAL— (1) External branch, motor to crico-thyroid. (2) Internal branch, sensory to the mucous membrane of larynx. (3) A sensory filament to root of tongue, just in front of and at sides of epiglottis. 4. INFERIOR, or RECURRENT LARYNGEAL: motor to all the intrinsic muscles of the larynx, except the crico-thyroid. 5. CARDIAC BRANCH ES—- (1) Superior. This is— (a) Sensory to heart. (b) Vaso-inhibitory to the blood-vessels of the abdomen (‘depressor nerve.”’) (2) Inferior—Inhibitory to nerve of heart. Note—Superior— § = Sensory. Inferior— I = Inhibitory. 6. PuLMONARY BRANCHES— (1) Afferent fibres, sensory for the lung, and excito-motor for inspiration. (2) Eferent fibres, motor to bronchial muscles. 59 7. CASoPHAGEAL BRANCHES, to form plexus gulw. 8. GASTRIC BRANCHES. 9. Left vagus sends Sensory BRANCHES to the Spleen and Liver. To help the memory note how— A Arnold’s nerve. Prodigal | Pharyngeal branch. Son Superior laryngeal. Runs Recurrent laryngeal. Cleverly Cardiac branches. through a Purse Pulmonary branches. Of (Esophageal branches. Gold Gastric branches. and Spoils Splenic branches. his Liver. Branches to the liver. What are the Results of Cutting and Stimulating the Superior Laryngeal ? 1. Lower 5np of divided nerve— Movement of the crico-thyroid muscle. 2. UppER END— (1) Acute pain produced. (2) Deglutition excited. (3) Coughing excited. (4) Inspiration inhibited, and the diaphragm brought to rest in a state of relaxation. 60 What are the Results of Cutting both Vagi in the Middle of the Neck ? : 1. On the ALIMENTARY CANAL— (1) Paralysis of esophagus, and therefore deglutition is impaired. (2) Paralysis of the cardiac end of the stomach. (3) Secretion of gastric juice stopped for a time. 2. On VascuLaR SYSTEM— (1) Heart beats more rapidly, because inhibitory nerve is divided. (2) Blood pressure rises usually, and always if the animal be digesting. 3. On RespiraToRY SYSTEM— (1) Paralysis of all the intrinsic muscles of the larynx, except the crico-thyroid, (2) Respiration is slowed and «vepened, and there is a whistling sound during inspiration, as the lips of the glottis fall together, as the crico-arytenoideus posticus is paralyzed. It is slow and deep, because the impulses from the lungs that excite the inspiratory centre are cut off. (3) The bronchial muscles are paralyzed, the lungs become congested, and the vesicles filled with a frothy serum, and this, as it were, drowns the animal. What are the Results of Stimulating the Lower End of the divided Nerve ? 1, The intrinsic museles of the larynx, except the crico- thyroid contract. 61 Bronchial muscles contract. . Heart inhibited. . Walls of cesophagus contract. . Cardiac end of stomach contracts. an, wh If intestinal peristalsis 7s taking place, it is increased. What are the Results of Stimulating the Central End (1) below, and (2) above the Origin of the Superior Laryngeal Nerve ? 1. BeLtow— (1) Respiration, if the nerve is gently stimulated, is accelerated: if powerfully stimulated, respiration is stopped, with the diaphragm in a state of spasm. (2) Heart. If one vagus be still intact, there is reflex inhibition ; if both cut, there is not. (3) Vomiting may be induced. (4) Diabetic state of urine. produced. (5) Signs of pain. 2, ABOVE—- (1) Intense pain. (2) Respiration is probably retarded, and if arrested the diaphragm will be lax. The other results are the same as before—under (1). Give a Summary of the Functions of the Vuyus. 1. Sevsory to pharynx, larynx, heart, root of tongue, cesophagus, stomach, spleen, liver, external auditory meatus, and part of auricle. 62 ' 2. Moror—larynx, bronchi, pharynx, oesophagus, and cardiac end of stomach. 3. Inuiprrory—of heart. 4, Sucrerory—for glands of the stomach. Give the Superficial Origin of the Spinal Accessory. 1. Side of medulla (‘‘ Accessory ” part). 2. Spinal cord as low as the 5th or 6th cervical nerves (“ Spinal” part). Give its Course. The spinal part enters the skull through the foramen magnum, joins the other part, and then leaves the skull through the jugular foramen in front or behind internal jugular vein. Give the Functions of the two Parts. 1. The Spinat Part is motor to the sterno-mastoid and trapezius. It communicates with— The 3rd cervical nerve in the sterno-mastoid. The 2nd and 3rd cervical nerves in the posterior triangle. The 3rd, 4th and 5th cervical nerves in the trapezius. 2, The Accessory parr (from the medulla) joins the vagus, forming its motor root: this part contains the inhibitory nerve of the heart, as well as the motor nerves for the larynx and pharynx. 63 What are the Results of Dividing this Nerve? 1. AccEssoRY PART— (1) Heart beats more rapidly, because the inhibitory nerve is divided. (2) Loss of voice, because the muscles of the larynx are paralysed. (3) Swallowing is impaired. The motor fibres of the stomach, cesophagus, and bronchi in the vagi are not derived from the spinal accessory. 2. Spinal PART— Paralysis of the sterno-mastoid and trapezius. ’ Give the Course of the Hypo-Glossal Nerve. It passes through the anterior condyloid foramen in two bundles, at first it lies behind the internal carotid artery and internal jugular vein, then passes forward between the artery and vein, hooks round the occipital branch, and crosses the external carotid artery. Guve its Branches of Distribution. 1. Descendens noni, forms a loop with the communicans noni. 2. Branch to thyro-hyoid. 3. Genio-hyoid branch. 4, All the intrinsic and extrinsic muscles of the tongue. 64 Name the Muscles it Supplies. 1. Betow Hyorp none—four muscles— (1) Thyro-hyoid—special branch. (2) Omo-hyoid | (3) Sterno-hyoid ; Descendens noni. (4) Sterno-thyroid \ 2, ABOVE HYOID BoNE—four muscles— (1) Genio-hyoid. (2) Genio-hyo-glossus (3) Hyo-glossus | tin muscles of tongue. (4) Stylo-glossus 3. Intrinsic muscles of tongue—four bands of muscular fibres. [Note the three “fours.” ] What are the Results of its Paralysis ? If both be cut, then it is impossible to protrude or retract the tongue. If only one be cut, the tongue can be protruded and retracted, and when protruded it points to the paralyzed side. Edinburgh : Printed by E. & 8. Livinestonz, 4 Melbourne Place. PART VIII. SPINAL CORD—BRAIN—REPRODUCTION— PHYSIOLOGICAL CHEMISTRY. 7 EDINBURGH: ES S&S LIVINGSTONE, PRINTED BY E. & 8 LIVINGSTONE MELBOURNE PLACE EDINBURGH. PHYSIOLOGY. PART VIII. COVERINGS OF THE SPINAL CORD. What are the Coverings of the Cord? I bo Dura mater, Sub-dural space. Arachnoid—curtain-like, dividing No. 2 from Sub-arachnoid space, containing most of the cerebro-spinal fluid. Pia mater. What is the other Description ? In it the arachnoid is looked upon as a serous membrane, enclosing a serous cavity, thus— 1. POP wb Dura mater. Parietal layer of arachnoid. Arachnoid cavity (= “‘sub-dural space”). Visceral layer of arachnoid. Sub-arachnoid space. Pia mater. Describe the Dura Mater. It is a firm FIBRO-SEROUS vascular membrane, reaching from the foramen magnum to the second or third piece of 4 the sacrum. It is separated from the bones of the spinal column by a little fat and loose areolar tissue, and a plexus of veins. Fibrous bands attach it closely to the posterior common ligament. It forms a very loose covering for the cord, being much larger than the cord it ensheaths. The two roots of thirty-one pairs of spinal nerves pierce it (124 perforations in all). Describe the Arachnoid. It is a very delicate NoN-VAscULAR membrane. Placed between the dura and pia, it divides the space between them into two—sub-dural space, and sub-arachnoid space. It forms tubular prolongations around the processes of the ligamentum denticulatum, and also around the roots of the spinal nerves. Describe the Sub-Arachnoid Space ? In this space is a quantity of delicate connective tissue forming a spongy network—the sub-arachnoid trabecule— the interstices being lined by endothelial plates. The tra- becule are connected on the one hand with the arachnoid, and on the other with the pia mater. The sub-arachnoid space contains most of the cerebro-spinal fluid—about 2 fluid ounces. Describe the Pia Mater. It is a delicate, highly vascular membrane, and firmly adherent to the spinal cord, so that it cannot be easily stripped off. A process or fold passes from it into the anterior median fissure of the cord, and it also gives sheaths to the roots of the spinal nerves. 5 How does it ditier from the Pia Mater of the Brain? It is— 1. Thicker. 2. Less vascular. 3. More adherent. What is the Linea Splendens ? It is a thickened fibrous band, along the anterior aspect of the outer surface of the pia. Describe the Ligamentum Denticulatum. It is a toothed ligament that runs along longitudinally on each side of the cord. Internally, it is attached to the pia mater about midway between the anterior and posterior nerve roots. There are some twenty-one tooth-like processes, extending from the medulla oblongata to the pointed ex- tremity of the cord—or from the foramen magnum to the 12th dorsal or 1st lumbar vertebra. What is the Use of this Ligament ? It helps to support and moor the spinal marrow within its wide dural sheath. How does the Pia Mater end below ? In the ‘‘filum terminale” or central ligament; in its upper half this encloses the continuation of the central canal of the spinal cord. Opposite the first or second sacral vertebra it pierces the dura mater, receiving an investment from it, and ends below by blending with the periosteum of the sacrum and the base of the coccyx. How is it Distinguished ? By its srivery hue. THE SPINAL CORD. Gire a General Description of the Cord. It extends from the foramen magnum to the lower border of the first lumbar vertebra; above, it passes into the medulla, and below, into the ‘FILUM TERMINALE.” Below the end of the cord (conus MEDULLARIS) we find a bundle of nerve roots, the CAUDA EQUINA, in the midst of which we find the silvery-looking thread, the ‘“filum terminale,” which passes from the apex of the conus medullaris. The length of the cord ranges from 15 to 18 inches: on section, it is cylindrical, or somewhat flattened antero-posteriorly. It has two enlargements. It gives origin to thirty-one pairs of spinal nerves. Describe the Enlargements. 1. The cervican enlargement, extending from the third cervical to the first dorsal vertebra. From this spring the large nerves of the upper extremity. 2, The Lumbar enlargement; it begins at the 10th dorsal vertebra, is largest opposite the 12th, and then gradually tapers away into the conus medullaris. From this spring the large nerves to the lower extremity. Both enlargements are chiefly due to an increase of the GREY MATTER of the cord. i Give the Length of the Cord at different Periods of Life. 1. At the first the cord extends all through the vertebral canal. 2. After the third month of intra-uterine life the spinal nerve roots and the vertebral canal grow faster than the cord. 3. At birth it reaches the lower border of the third lumbar vertebra. 4, In adult life it only reaches the lower border of the first lumbar vertebra. Describe the Fissures of the Cord. 1. ANTERIOR MEDIAN. —It is more distinct than the posterior ; in depth it extends only one-third of the thick- ness of the cord. It contains a distinct fold of the pia mater, with blood-vessels. At the bottom of this fissure is a transverse band of WHITH MATTER, connecting the two halves of the cord, and called ‘‘the anterior or white commissure.” 2. PosTERIOR MEDIAN.—This is a septum rather than an actual fissure: it does not contain a fold of the pia mater. In depth it extends one-half of the thickness of the cord. At its bottom lies “the posterior or grey commissure.” Besides these two chief “fissures” we have the ANTERO- LATERAL and POSTERO-LATERAL grooves, indicating the lines of origin of the anterior and posterior nerve roots. The antero-lateral has no real existence as a fissure, being a mere depression: the postero-lateral partakes more of the nature of a real fissure. In the cervical region, close to the posterior median fissure, is an additional cleft, along with several minor septa. 8 What are the Columns of the Cord ? The various fissures and grooves above mentioned divide the cord into— : 1. Anterior column. 2. Lateral column. 3. Posterior column, this last being further divided into— (1) Postero-internal tract (Goll). (2) Postero-external tract (Burdach)—also known as the FASCICULUS CUNEATUS, OY POSTERIOR ROOT ZONE. This part is specially affected in Loco- MOTOR ATAXY, and also in the “nervous” form of “ Ergotism.” How many Spinal Nerves are there ? Thirty-one pairs, each taking origin by two roots— the anterior and posterior. Their coverings or sheaths are similar to those of the cord itself. The bundle of nerve roots below the termination of the cord is known as the “cauda equina.” What are the Chief Arteries of the Cord and their Origin ? 1. Anterior spinal artery is formed by the union of two branches, and runs along the front of the cord. Ortcin—The vertebrals. 2. Posterior spinal arteries are two in number, and run down, one on each side, behind the line of origin of the posterior nerve roots. Oricin—The vertebrals. 9 What may be Observed on a Cross Section of the Cord ? . The two lateral halves of the cord. . Central core of grey matter. . Cortex of white matter. A central canal in the grey commissure. . The grey and white commissural fibres connecting the two lateral halves. _ A State the Appearance of the Grey Matter. It consists of two semilunar crescent-shaped masses, united by the grey or posterior commissure, thus giving it roughly, a resemblance to the capital letter H. The extremities of the crescent are known as the ANTERIOR and POSTERIOR HORNS or corNUA. The anterior is short and thick, the posterior long and narrow. Between the grey commissure and the bottom of the anterior median fissure is the ANTERIOR OY WHITE COMMISSURE. What is the “ Substantia Gelatinosa” of Rolando ? It is a stratum of gelatinous or clear-looking connective tissue at the apex of the posterior horn. What ts the “ Processus Reticularis” ? On the concave side of each crescent, just behind its centre the grey matter assumes the form of a network projecting out into the white substance, which receives the above name. What is Observed just in Front of this ? A pointed collection of grey matter, known as the INTERMEDIO-LATERAL TRACT, resembling a lateral horn. It is best seen in dorsal region. LO Point out the Appearance of the Grey Matter at Different Levels. 1. In the cervicaL region the anterior horn is broad and thick; the posterior long and narrow. 2. In the porsaL region they are both narrow, closely resembling the capital letter H. 3. In the tumsar region, they are both broad and thick, but especially the anterior. Describe the Central Canal of the Cord. The central canal, or ventricle, of the spinal cord is situated in the grey commissure. It is the remains of the primitive medullary canal of the embryo. Above, it expands into the 4th ventricle of the brain ; in the conus medullaris it enlarges and becomes T-shaped in section, and extends back to the surface, covered only by the pia mater. It is lined by columnar ciliated epithelium—at least in . the child. , What are the Structural Elements of the Grey Matter ? 1. Neuroglia (“nerve glue”). 2. Nervous elements—fibres and cells. Describe the Neuroglia. It consists of— . A homogenous jelly-like matrix. . A network of fine fibrille—‘neuroglia fibrils” (Klein). . Small branched nucleated cells—“ neuroglia cells.” . Larger cells—‘ cells of Deiters.” two re 11 What are the Nervous Elements ? 1. Multipolar nerve cells, singly or in groups, with processes— (1) An axial cylinder process, which does not branch but becomes directly continuous with a nerve fibre. (2) Processes that branch and form a fine dense network of fibrille. 2. Medullated nerve fibres. What are the Groups of Nerve Cells called ? They are known as “ VESICULAR COLUMNS.” Name the Vesicular Columns. 1. The largest is in the anterior horn—the ANTERIOR VESICULAR COLUMN, consisting of an outer and an inner group of cells. In function the cells are motor and trophic. 2. INTERMEDIO-LATERAL VESICULAR COLUMN, in the pro- jection of grey matter about midway between the anterior and posterior horns: best seen in the dorsal region. 3. POSTERIOR VESICULAR coLUMN (Clarke’s column, or dorsal nucleus), at the base of the posterior horn, near its inner angle. Name the Tracts of White Matter in the Spinal Cord. 1. ANTERIOR COLUMN— (1) Antero-internal tract (fasciculus of Tiirck : direct, or uncrossed, pyramidal tract). (2) Antero-external tract (basis bundle of Turner : anterior root zone of Charcot). 12 2, LaTERAL COLUMN— (1) Crossed pyramidal tract. (2) Direct cerebellar tract. (3) Sensory zone of Gowers. (4) Mixed zone—anterior mixed; posterior mixed, or limiting layer. 3. PosTerror coLuMN— (1) Postero-internal tract (fasciculus of Goll). (2) Postero-external tract (fasciculus of Burdach : posterior root zone of Charcot: fasciculus cuneatus). Give the Structure of the White Matter. It consists of blood-vessels and neuroglia, but chiefly of medullated nerve fibres. How do these Fibres differ in Structure from Medullated Nerve Fibres generally ? So far as can be discovered they do not possess a neuri- lemma, nor “‘ nodes of Ranvier.” (For the Minute structure of Nerve Fibres, and Special forms of Nerve Cells, see Part L, pp. 53 to 57.) Give the Deep Origin of the Anterior Nerve Roots. The fibres may be traced to— 1. The lateral group of cells in the anterior horn. The lateral white columns. The posterior cornu. The anterior part of the commissure. The anterior group of cells in the anterior horn. ot iG BS 13 (rive the Deep Origin of the Posterior Nerve Roots. The posterior root enters the cord in two distinct bundles, external and internal. The fibres of the ExreRNAL bundle may be traced to— 1. The nerve cells of the posterior horn. 2. The anterior horn. 3. The posterior part of the commissure. The fibres of the INTERNAL bundle do not pass straight to the grey matter, but enter the white substance of the posterior column, and ultimately pass to— 1. The lateral cells of anterior horn. 2. The cells of Clarke’s column. 3. The posterior part of the commissure. It is believed that the fibres of the anterior root become (in great part) directly continuous with the unbranched process (axis cylinder process) of the multipolar nerve cells ; while the fibres of the posterior root become continuous with the branched processes (plexuses of Gerlach). What are the Chief Functions of the Cord ? 1. A great reflex centre. 2. A conductor of impressions to and from the brain. What is the General Structure of the Spinal Cord in a Lobster ? It consists of a double chain of ganglia united by transverse and longitudinal branches. This is essentially its schema as a reflex centre. In vertebrata the ganglia are so numerous that they are fused together in all directions. Reflex action is entirely independent of sensation. 14 What Conditions affect Reflea Action ? 1. The nature of the afferent impulse. 2. The intensity of the afferent impulse. 3. The locality. 4. The condition of the cord. What are the Characters of Spinal Reflex Movement ? J. Simple. 2. Compound or complicated— (1) Of a definite character. (2) Of an indefinite character. Give an Example of Simple Reflex Action. Cross the legs, and strike the tendon of the patella sharply : the foot is jerked upwards—the “patellar reflex.” Give an Example of Compound Reflex Action of a Definite Character. Remove a frog’s brain, and then touch some part of the skin of its body with acetic acid ; the toes will move to the spot to remove the irritant. The muscles are co-ordinated and many groups are thrown into action, in an harmonious combination, to serve a DISTINCT PURPOSE. In this respect the frog is very remarkable. To get this action, however— 1. The stimulus must be applied to the NERVE TERMINA- tions and not to the trunk of a nerve, otherwise we would get indefinite reflex movements. 2. The stimulus must not be too powerful. 3. The cord must not be in a too excitable condition. 15 What are the Causes of Compound Reflex Movements of an Indefinite Character ? 1. A too powerful stimulus. 2. Over-excitability of the spinal cord—e.g., as in a frog under the influence of strychnine. How does Spinal Reflex Action differ in a Mammal as compared with a Frog? The spinal cord of a mammal is not so remarkable for its reflex movements as it is in the frog, because in the mammal these movements are to a great extent relegated to the brain. Further, the movements of the limbs of a mammal are more complicated than those of the frog. Name the: Chief Reflex Centres in the Spinal Cord of a Mammal. To urinary bladder lower part—probably in To sphincter of anus the lumbar enlargement. Vase-200t03 Gentes all through the cord. Centres for secretion of sweat 6. Centre for radiating fibres of iris—in the pons. To organs of generation jib are placed at the SUP ee If the cord be cut or crushed at the lower part, the centres placed there are paralyzed—the feces pass involun- tarily, and the urine is either retained or dribbles away constantly. After a time, the centres may partially regain themselves: micturition may take place perfectly enough reflexly ; but defxcation does not take place perfectly, as this function requires impulses from the brain as well. 16 State what you know of Inhibition of Spinal Reflex Action. Stimulate the hand—e.g., by tickling or pricking: if the attention is not directed to it, the hand is at once withdrawn ; but if the attention be directed to it, this withdrawal can be prevented—in other words, the reflex movement may be inhibited. This inhibitory power is absent (or less marked) in sleep—e.g., when the skin is touched or tickled ; or touch with the finger the palm of the hand of a sleeping child, the finger is grasped, but when the child is awake no such effect is produced. Other examples are—that one can prevent, by an effort of will, jerking up of the legs when the feet are tickled ; so, also involuntary closing of the eyes, and starting, when a blow is aimed at the head. Where are the Inhibitory Centres placed ? The corpora quadrigemina (optic lobes, in animals) are the inhibitory centres for spinal reflex action, and perhaps also the optic thalami. The fibres probably pass down the cord in the crossed pyramidal tract (lateral column). Give Experiments in Support of the above. Take two frogs, and remove all the brain above the optic lobes in one of them, and then note the time between the stimulation (¢g., by putting the toes into a solution of common salt) and the occurrence of the reflex movement. In the other frog, remove all the brain above the medulla (including the optic lobes), and treat in a similar manner. When the optic lobes are removed the reflex movement takes place much more quickly than when they are present. Further, irritate the optic lobes (e.g., by putting a crystal of common salt on them), and a longer time elapses between 17 the stimulation and the reflex movement than when they are left untouched, because the irritation causes a greater number of inhibitory impulses to be sent down the cord. Give some Experiments serving to show the Conducting Paths of the Cord. 1. Cut through lateral half at any part, and there is— (1) Loss of motion, but increase of sensibility— except TACTILE sensation—which is said to be lost (Schiff), on the same side below the injury. (2) Loss of sensation, but motion not affected on the opposite side below the injury. 2. Make a vertical median incision in the cord at any part: there is loss of sensibility on both sides in a part corresponding to the length and position of the incision. Voluntary movement not affected. 3. Make a vertical median incision at decussation of pyramids: there is loss of motion on BoTH sides. 4. Cut through ricHT crus cerebri—or, what is the same thing, suppose there be a blood clot on the right side of the brain involving both motor and sensory areas: there is loss of both motion and sensation on the LEFT — 7.e., the opposite side. 5. Cut through all the white columns entirely, leaving only the grey matter, or any part of it—sensations that give rise to PaIN are still felt. What Deductions may be drawn from the above Experiments? 1. Motor rmpuLses start in the brain, cross to the other side at the upper part of the medulla, and descend in the antero-lateral columns, keeping to the same side throughout. B 18 2. Sensory mMPULsES pass from the posterior root along a certain length of the posterior column, then cross to the other side and ascend to the brain. 3, Tactile sensory impressions also pass up the posterior column of the same side (Schiff), though others believe that they decussate in the spinal cord. 4. Sensations that give rise to pain pass up through all parts of the grey matter, probably decussating in the cord. 5. Sensations of temperature are probably conducted along a separate and distinct set of fibres, and undergo decussation in the cord. 6, Vaso-motor fibres pass along the lateral columns, and leave by the anterior nerve roots. 2 7, Co-ordinating fibres from the cerebellum are probably in the posterior column, and decussate at different levels. THE BRAIN. What does this Include ? All parts of the great central nervous system enclosed within the cavity of the cranium, viz :— 1. The cerebrum. 2. The cerebellum. 3. The pons varolii. +. The medulla oblongata. For the— Removal of the Skull-Cap. Removal of the Brain, The Dura Mater, and its Processes. The Venous Sinuses. (See “ Anatomy,” Part III, pp. 5 to 11.) 19 What are the Communications of the Cerebro-Spinal Fluid ? It communicates with the fluid in the spinal subarach- noid space, through the “foramen of Majendi” in the roof of the 4th ventricle, and through two similar openings in the ventricular roof between the medulla and cerebellum. Give the Boundaries and Contents of the “ Inter-peduncular Space.” BovnpaRries— In front—Optic commissure. Behind—Pons varolii. Sides— In front—Optic tracts. Behind—Crura cerebri. CONTENTS— 1. Tuber cinereum. Infundibulum, attached to pituitary body. Corpora albicantia. Posterior perforated spot (“pons Tarini”). Probably also the third pair of cranial nerves. Sb ge bs This space has a very intimate relation to the floor of the third ventricle. What are the Arteries of the Brain? They are all derived from the two INTERNAL CAROTIDS, and the TWO VERTEBRALS. The internal carotids give off— 1, Ophthalmic branches. 2. Anterior cerebral. 3. Middle cerebral. 4. Posterior communicating. 20 What are the Branches of the Middle Cerebral ? Lenticular. Lenticulo-striate. Lenticulo-optic. What is the Source of the Choroidal Arteries ? Either from the internal carotids or middle cerebrals : they supply the choroid plexus. What are the Branches of the Vertebrals ? It sometimes gives off the POSTERIOR INFERIOR CERE- BELLAR. The two vertebrals unite to form the BAsILaR, and this gives off— 1. Transverse branches—one of them is the internal auditory. 2, Anterior inferior cerebellar. 3. Superior cerebellar. 4, Posterior cerebrals. (For the “Circle of Willis,” see ‘“ Anatomy,” Part IIL, page 64.) What are the Special Features of the Cerebral Circulation ? 1. The free anastomosis at the circle of Willis, thus providing against blockages at any one part. 2. The main vessels enter the skull through tortuous bony canals, thus mitigating the force of the heart’s impulse. 3. The vessels ramify and break up in the pia mater before entering the substance of the brain. 21 4, The great length and terminal nature of the capillaries, as well as the thinness of their walls. 5. The presence of venous sinuses, which are without valves, and do not run along with the arteries. MEDULLA OBLONGATA. Give a General Description of this Part. It is about 14 inches long, 1 inch in breadth, and about 4 inch thick. It is continuous below with the spinal cord, and above with the pons varolii. Its anterior wall rests on the upper surface of the basi-occipital groove; its posterior surface lies between the two lateral lobes of the cerebellum, and partly forms the floor of the 4th ventricle. What are the Fissures of the Medulla? 1. Anterior median fissure. 2. Posterior median fissure. 3. Lateral fissures. Name the various White Strands of the Medulla. 1. Fasciculus gracilis, with its enlarged upper end, known as the clava. This is the prolongation upwards of the postero-internal strand or ‘‘ band of Goll.” 2. Fasciculus cuneatus, expanding above into the cuneate tubercle. This is the prolongation upwards of the postero-external strand or “column of Burdach.” 22 3. Outside this is a greyish band, the funiculus of Rolando, expanding above into a tubercle—the “tubercle of Rolando.” 4. Restiform body or inferior cerebellar peduncle, which seems to be incorporated with the previous fasciculi, though this is not the case, it being composed of fibres derived for the most part from the lateral column of the cord, viz :—the direct cerebellar tract joined by the external arciform fibres. 5. The tract of the olivary fillet and olivary body, a prolongation from the mixed zone of the lateral column. The rest of the fibres of this zone go to form part of the Sormatio reticularis. 6. The anterior pyramid, formed chiefly by the crossed pyramidal tract of the opposiTE side, with a few fibres from the direct pyramidal tract of the same side. It is this crossing that forms the ‘“decussation of the pyramids.” The above description is somewhat more complicated than the older and more usual one, where the medulla is looked upon as made up of five strands, viz :— 1. Anterior pyramids. 2. Olivary fasciculus. 3. Restiform body (fasciculus cwneatus). 4. Posterior pyramid (fasciculus gracilis). 5. Fasciculus teres. The two latter go to the cerebellum, the others to the cerebrum. oD N ‘snyveund snpnotuny ‘sIflowiS snqnotung oy, pues [BUIEzUT-0.10480q ‘(qoUINT,) Sor} SHTNOTOSRT “L} ‘SLIB[NOYOI OTYBUIO} OF, | *9UOZ PoXT ‘gorTy Avearyo of, ‘UNT[Iqe190 OF vvUeT, pus ‘fpoq TWIOJTJSoL OF, *'* JoRIY AV[[Eq e190 YooITC, ‘apts apisoddo Jo pttuerdd qowoeyue oF, **''* qoRry TeprurerXd passorg ‘SLIB[NOTJOI OTPETIOF OT, ‘49[y pue epounped Axearpo oy, pe “9U0Z POXT]AL ‘oppunq [eurpnylsuocT ro1seqsod ou} ‘opis oures Jo prmerdd roreyue oy, sessed your Teprareadd yoourq ‘VITOCUN “a@400 a G : | NWM100 IVEGLV'] ‘T | NWA109 YOLUALSOg J AN NWOATOOD YOIUALINY wynpapy ayn ylnosy, pion ay fo spovuy, ayy ayy dn any 24 How is the Grey Matter of the Medulla divided ? 1. Into that derived from the grey matter of the cord. 2. Independent masses of grey matter. Name the Parts derived from the Grey Matter of the Cord. From the ANTERIOR HORN we find— 1. From its head, the nucleus lateralis 2. From its neck, the unterior part of the formatio reticularis. 5. From its base, the nucleus of the fasciculus teres, From the POSTERIOR HORN 1. From its head, the nucleus of Rolando. 2, From its neck, the posterior part of the formatio reticularis. 3. From its base, nucleus of the funiculus gracilis, nucleus cuneatus, and nuclei on the floor of the 4th ventricle. Name the Independent Masses of Grey Matter. 1. Nucleus of the olivary body. 2. Accessory olivary nuclei. 3. Nucleus of the external arciform fibres. PONS VAROLII. How are the White Fibres arranged ? 1. Superficial transverse, seen on the surface of the pons. 2. Deep transverse, lying behind the superficial longi- tudinal. 25 3. Superficial longitudinal, the upward continuation of the anterior pyramids of the medulla. 4. Deep longitudinal, near the dorsal aspect of the pons. Name the Grey Nuclei of the Pons. 1. Nucleus pontis, amongst the superficial transverse fibres. 2. Superior olivary nucleus, on the dorsal part of the pons, behind the trapezium. 3. Nuclei of origin of several cranial nerves. Name the Special Centres in the Medulla and Pons. 1. Centres for the respiratory system. 2. Centres for the vascular system— (1) Vaso-motor. (2) Cardio-inhibitory, and probably (3) Cardio-motor. 3. Centres for reflex movement in connection with the alimentary canal— (1) Deglutition—motor centre of 5th, centres of 7th and 9th all used in deglutition. (2) Vomiting centre. (3) Sucking centre. 4+. Centre for certain movements connected with the eye—e.g., winking. The dilator centre is in the pons. 5. Centres for secretion, tears, saliva, sweat, etc. 6. The medulla also assists the co-ordination of spinal reflex movements in mammals. 7. Centre for general convulsions, arising from asphyxia, anzmia, etc. 26 THE CEREBRUM. Name the Fissures of the Cerebrum. 1. Primary or interlobular fissures— (1) Fissure of Sylvius: this fissure appears first in development. (2) Fissure of Rolando. (3) Parieto-occipital fissure. These are not mere indentations of the cerebral cortex, but are formed by the folding upon itself of the entire cerebral substance. 2. Secondary or intralobular.—These are mere indenta- tions of the cerebral cortex, and separate the individual convolutions from each other. Name the Lobes of the Cerebrum. 1. Frontal. 2. Parietal. 3. Occipital. 4, Tempero-sphenoidal. 5. Island of Reil—central lobe; this lobe is not in contact with the bones of the sci, but is hidden within the two limbs of the Sylvian fissure. Give the Boundaries of the Frontal Lobe. BeuinD, the fissure of Rolando. Bexow, the horizontal limb of the Sylvian fissure. Axoveg, the great horizontal fissure. Ww ~] Name its Convolutions. 1. Ascending frontal, just in front of the fissure of Rolando; and in front of this convolution we find the precentral sulcus. 2. Superior frontal 3. Middle frontal “ Prefrontal Lobe” (Gowers). 4. Inferior frontal The tert inferior frontal is known as “ Broca’s convolu- tion,” and is believed to be the centre for speech. The orpiTaL surFace of the frontal lobe presents the tri-radiate fissure, which subdivides this surface into three gyri— (1) Internal orbital, or gyrus rectus. (2) Anterior orbital. (3) External orbital. Whut vs found on the Surface of the Gyrus Rectus ? A club-shaped sulcus, the “olfactory groove,” for the OLFACTORY BULB, and its PEDUNCLE. Give the Boundaries of the Parietal Lobe. In Front, the fissure of Rolando. Beutnp, the parieto-occipital fissure. Betow, the horizontal limb of the fissure of Sylvius. Name tts Convolutions. 1. Ascending parietal, parallel to and behind the fissure of Rolando. 28 2. Superior parietal; below this we find the intra- parietal sulcus 3. Supra-marginal gyrus, or convolution of the parietal eminence (Turner). 4. Angular gyrus; this gyrus probably contains the centre for sight, though the neighbouring occipital lobes are probably concerned in the same function. Give the Boundaries of the Occipital Lobe. It lies behind the parieto-occipital fissure, and a line drawn downwards from it across the surface of the hemi- sphere to its lower margin. Name its Convolutions. Superior occipital. Middle occipital. Inferior occipital. This lobe lies in the superior fossa of the occipital bone, and rests on the tentorium. It is closely connected with the sense of sight. Give the Boundaries of the External Surface of the Temporo- Sphenoidal Lobe. It lies in the middle fossa of the base of the skull, resting partly on the petrous part of the temporal bone— Axgove, is the horizontal limb of the fissure of Sylvius. Betow, the inferior temporo-sphenoidal sulcus. Benind, it merges into the occipital lobe and angular gyrus. 29 Name its Convolutions. 1. Superior temporo-sphenoidal. 2. Middle temporo-sphenoidal: between these two we find the ‘parallel fissure.” 3. Inferior temporo-sphenoidal. What is found on the under Surface of the Temporo- Sphenoidal Lobe ? On the under surface, the temporo-sphenoidal and the occipital lobes are directly continuous; they present two convolutions—a superior and an inferior occipito-temporal— separated by the ‘collateral fissure.” Describe the Island of Rel. It lies deeply in the fissure of Sylvius, forming a delta between the two limbs of that fissure. It appears first in development, and consists of five or six convolutions known as the “ gyri operti.” How can tt be Shown ? It may be seen to a certain extent by separating the sides of the Sylvian fissure, but to expose it fully the tip of the temporo-sphenoidal lobe should be removed, as well as the “ operculum.” What is the Operculum ? It is formed by the contiguous ends of the— 1, Ascending frontal 2. Ascending parietal convolutions. 3. Inferior frontal At one period of its history, the island of Reil is not covered, but these parts grow over and cover it. 30 Name the Fissures and Convolutions on the Median Surface of the Brain. 1. CALLOSAL FISSURE, close to the corpus callosum. 2, CALLOSO-MARGINAL FISSURE, between the former and the upper margin of the hemisphere. 3. Close to the corpus callosum, we find the gyrus Sornicatus. 4. Above that in front, the marginal convolution. The hinder part of this is known as the paracentral lobule. 5. The parieto-oceipital fissure, and in front of that the quadrate lobule or precuneus. 6. Lower down we find the calearine fissure or sulcus ; between this and the previous fissure is a triangular mass, the occipital lobe or cuneus. 7. The dentate (hippocampal) jisswre ends in the notch of the uncus; it separates the uncinate or hippocampal gyrus from the fimbria or Tenia Hippocampi. At the bottom of the dentate fissure is the fuscia dentata. Describe the Structure of the Cerebral Cortex. 1. A layer, the most external, chiefly composed of neuroglia, with a few stellate cells. 2. A layer of small, multipolar pyramidal nerve cells. 3. A layer of large and small pyramidal branching cells, with their apices towards the surface; they are separated into groups hy radiating nerve fibres. 4, Small irregular cells, with many fine processes. 31 5. This layer consists chiefly of fusiform cells, which, at the apex of the gyrus, are set at right angles to the surface, but in the sulci are parallel with it. In the motor areas, especially in the ascending frontal convolution, the nerve cells are of large size and arranged in groups. These cells are called Grant ceLts, GaNGLIONIC CELTS, and cELLs of Brrz. Point ont in a general way the Position of the Motor and Sensory Areas. The Moror areas are situated immediately in front of and behind the fissure of Rolando. The general order of centres from below upwards is— Centres for Face. Centres for Upper Extremity. Centres for Lower Extremity. SprEecH—the inferior frontal of left side—“ convolution of Broca.” The centres for COMMON SENSATION are placed posterior to the motor centres. Centres of SPECIAL SENSATION— 1, Sight — the angular gyrus or the contiguous occipital lobe. 2. Auditory centre — in the superior temporo- sphenoidal convolution. 3. Smell — in the middle temporo-sphenoidal convolution. 4, Taste — in the inferior temporo - sphenoidal convolution. 32 How would you Expose the Corpus Callosum ? The two hemispheres of the brain are separated by a deep fissure, and at the bottom of this lies the “corpus callosum.” With the base of the brain downwards, remove slices from its upper surface. This will expose a white central mass with red dots in each hemisphere, surrounded by grey matter. The white spot is the centrum ovale minus, and the red dots the puncta vasculosa. Cut down to the level of the corpus callosum, when the two white parts seem to fuse, forming the centrum ovale majus. The upper surface of the corpus callosum is now exposed. Describe the Corpus Callosum. The corpus callosum, or great commissure, connects the two hemispheres; it is whitish in colour and about one-half the length of the brain (about 4 inches), but is placed nearer the front than the back. It arches from before backwards; it is thicker at the ends, and is thickest and widest behind : it is narrowest in the middle. In rront it bends down, forming the genu, which is prolonged into the rostrum, which is connected with the optic commissure through the lamina cinerea. It finally bifurcates into two peduncles, which end in the anterior perforated spot. Beurnp, it ends in a free thickened border, the splenium. Its UPPER suRFAcE is marked by a raphé, and on each, and parallel with this, the median longitudinal stric or “nerves of Lancisi;” external to these we find the lateral longitudinal stric. ’ Its UNDER SURFACE rests, in its posterior part, on the body of the fornix ; its anterior part on the septum lucidum. Lareratty, it forms the roof of the lateral ventricles. 33 VENTRICLES, Describe the Lateral Ventricles. To expose them, cut through the corpus callosum a little on each side of the median line, and turn the part aside. Each ventricle consists of a body and three cornua—or “anterior,” “ posterior,” and “ lateral” horns, The ANTERIOR HORN passes forwards and outwards, into the frontal lobe, in front of the corpus striatum. The POSTERIOR HORN curves backwards, outwards, and inwards, into the occipital lobe. The sBopy is triangular in section, the rvof and floor meeting and blending on the outer side. Give the Boundaries of the Body of the Ventricle. The roor is the under surface of the corpus callosum. The INNER WALL is the septum lucidum, with the “ foramen of Monro.” EXTERNALLY, the roof and floor meet. On the FLOoR we find— 1. A small part of the corpus callosum. 2, Nucleus caudatus of the corpus striatum (intra-ventricular nucleus). 3. Tenia semi-circularis. 4, Optic thalamus. 5. The choroid plexus, the vascular fringe of the velum interpositum. 6. The free edge of the body of the fornix. ce 34 Describe the Descending Horn. It curves round the posterior end of the optic thalamus, and runs backwards, outwards, downwards, forwards, and inwards (hence called the B.O.D.F.I. horn) in the substance of the temporo-sphenoidal lobe. In its ROoF are— 1. Corpus callosum. 2. Optic thalamus. 3. Nucleus caudatus. 4. Teenia semi-circularis. In its FLooR we find— 1. The hippocampus major—a prominence due to the dentate fissure. 2, Pes hippocampi, the paw-like termination of the above. 3. Tenia hippocampi (‘corpus jimbriatum”), the edge of the posterior pillar of the fornix. 4, Choroid plexus, entering through the “great transverse fissure.” What is the ‘‘ Eminentia Collateralis” ? It is a slight eminence at the point where the lateral and posterior horns diverge, caused by the collateral fissure on the under surface. What are the Communications of the Luteral Ventricles ? They communicate with the third ventricle through the foramen of Monro, which lies between the anterior pillars of the fornix and the optic thalami: it is a Y-shaped passage. 35 Give the Boundaries of the Third Ventriele. This is a narrow cleft-like space, in the middle line between the optic thalami. The sipes are formed by the optic thalami and the peduncles of the pineal gland: crossing the space at this point, we find the middle commissure. The IMMEDIATE ROOF is the velum interpositum, above this the fornix, and higher up still the corpus callosum. These structures must be removed to expose it. Its FLoor is formed by the inter-peduncular space and its contents, viz.:— di Sop wie 6. Locus perforatus posticus (“ pons Tarini.”) Corpora albicantia. The tuber cinereum. The infundibulum. The optic commissure. Lamina cinerea. In FrontT— 1, Anterior pillars of fornix. 2. Anterior commissure. 3. Foramen of Monro. Bexninp— 1, Corpora quadrigemina and pineal gland. 2, Posterior commissure. 3. Aqueduct of Sylvius. Nume the Commissures of this Ventricle. 1. Middle or soft—all grey matter passing between the two optic thalami. 2. Posterior—white fibres. 3. Anterlor—also white fibres. 36 What are the Communications of the Third Ventricle ? It communicates in front with the lateral ventricles, through the foramen of Monro; and behind, through the aqueduct of Sylvius, with the fourth ventricle. This canal is often known as the “iter a tertio ad quartum ventrt- culum,” or simply the “17rER.” Give the Dissection to Expose, and the Boundaries of the Fifth Ventriele. It is a thin translucent, double, vertical, mesial partition, which separates the lateral ventricles from each other. To expose it, divide the corpus callosum in the middle by a transverse incision and turn forwards the anterior part, and the SEPTUM LUcIDUM will be exposed. Between the two layers we have the fifth ventricle, which is a closed cavity and has no communications, and is not lined by epithelium like the other ventricles. It is bounded— ABOVE and in Front, by the corpus callosum. Betow and BEHIND, by the fornix. On EACH SIDE, by the septum lucidum. This ventricle is merely an accidentally enclosed space, as it were, by the growth of the brain tissue, and is not, like all the other ventricles, a remnant of the cerebro-spinal embryonic canal. What is the Fourth Ventricle ? It is a dilatation of the central canal of the spinal cord. By the divergence of the posterior pyramids and restiform bodies, the grey matter comes to the surface, and the central canal is lost in the fourth ventricle. In shape it resembles an heraldic lozenge. 37 What is its Position ? It rests on the back of the medulla and pons, and behind it is the cerebellum. Describe its Floor. Its lower angle is often called the “calamus scriptorius,” from its supposed likeness to a writing pen. Running across the widest part of the floor are the stri@ acusticw, dividing the floor into two divisions. Note also, on the floor, the inferior and superior fovea, the fasciculus teres, the tuber- culum acusticum, the ala cinerea with the eminentia cinered, and at the upper part the locus ceruleus. What are its Lateral Walls ? 1. The Ltowrr part—the j/uniculus gracilis (posterior pyramid) and its clava; higher up the funiculus cuneatus, and higher still the restiform body, or inferior peduncle of the cerebellum. 2. The upper part—the superior peduncles of the cerebellum. How is its Roof jormed ? The lower half is roofed over by a reflection of the pia mater from the cerebellum to the back of the medulla. The roof of the upper part is formed by the superior cerebellar peduncles, and partly by the superior and inferior medullary vela—the superior is known as the “valve of Vieussens,” the inferior as the “valve of Tarini.” What are the Openings into the Fourth Ventricle ? At the superior angle we have the “aqueduct of Sylvius,’ communicating with the 3rd ventricle: at the lower angle we find the opening of the central canal of the spinal cord: in its roof we find the “ foramen of Majendie,” communicating with subarachnoid space. 38 Name the Grey Nuclei in the Floor of the Fourth Ventricle. 1. The HyPo-GLossaL Nucxzus, for 9th nerve. 2. TUBERCULUM ACUSTICUM. 3. The ava CINEREA and its eminenti4, for the spinal accessory, vagus, and glosso-pharyngeal nerves (8th pair). 4, At the upper part the sensory and motor nuclei of the 5th nerve. 5. The nucleus of the 6th nerve. 6. The nucleus of the 7th nerve (facial). 7. Nucleus for auditory part of the 7th nerve. Describe the Forni, It lies beneath the corpus callosum, and belongs to the longitudinal system of commissural fibres of the brain. It is composed of white fibres, and its two lateral halves separate in front and behind, forming the anterior and posterior pillars, but are united at the middle part, forming the Bopy. The “body” is connected with the under surface of the corpus callosum; the edges are in contact with the choroid plexuses, and its under surface rests on the velum interpositum. Describe the Course of the Anterior Pillars. They descend through the grey matter on the sides of the 3rd ventricle, between the corpora striata, curve back and reach the corpora albicantia, where they make a twisted loop, like a figure-of-8, forming the white cortex of the corpora; they then ascend to the anterior tubercles of the optic thalami. Give the Course of the Posterior Pillars. They curve outwards and enter the descending horn of the lateral ventricles, as the tenia hippocampi, lying in the concave margin of the hippocampus major, extending to its extremity. 39 Name the Commissures of the Brain. 1. Corpus callosum, or great commissure. The fornix. Tenia semi-circularis. Anterior commissure . Middle commissure in 3rd ventricle. Posterior commissure Poe Y2 bo What are the parts of the Crura Cerebri ? 1. The tEemEntvum, on posterior surface. 2. The pus, Basis, or cRUSTA, on anterior surface. 3. Between these two parts there is a stratum of dark grey matter, the ‘locus niger.” How are the Fibres arranged in the Cerebro-Spinal System ? 1. ProsEcTIon sySTEMS— (1) Cerebral part, or proximal projection system— : fibres from the basal ganglia into the con- volutions of the hemispheres, forming the corona radiata. (2) Middle projection system — fibres from basal ganglia to pons and medulla; this system decussutes. (3) Distal projection system —nerves through the body, generally from spinal cord. 2, TRANSVERSE COMMISSURAL SYSTEM— These connect the two hemispheres, viz :— (1) Corpus callosum, the chief. (2) Anterior compu) (3) Middle commissure | in 3rd ventricle. (4) Posterior commissure 40 3. ASSOCIATION SYSTEM— These are found in each half of the brain; they keep on the same side of the middle line, and connect various parts of the same side together, viz :— (1) Fornix. (2) Tenia semicircularis. (3) Strie longitudinales. (4) Fibres of uncinate convolution, connecting frontal and temporo-sphenoidal lobes. (5) Fibres of gyrus fornicatus. (6) Longitudinal inferior fasciculus, between occipital and temporal lobe. Name the “ Basal Ganglia.” 1. Corpora striata. Optic thalami. Corpora quadrigemina Corpora geniculata sometimes included. SOF Se Ge ES Locus niger Describe the Optic Thalamt. They are two large, oval, convex masses, placed above the crura cerebri; but behind and internal to the corpora striata, from which they are separated by the tenia semi- circularis. They form part of the floor of the lateral ventricles, and the lateral walls of the third ventricle. Their anterior end is rounded—the anterior tubercle; and at the posterior end, we find the posterior tubercle or pulvinar. They consist of a continuous mass of grey matter, traversed by nerve fibres in no definite manner. 41 What are the Purts of the Corpora Striata? Each corpus consists of two parts— 1. The NUCLEUS CAUDATUS or intra-ventricular nucleus ; it projects into the lateral ventricle. On section the grey core is streaked with white fibres, hence the name corpus striatum. 2. The NUCLEUS LENTICULARIS or extra-ventricular nucleus ; it is separated from the former by a strand of white fibres, which form part of the internul capsule. It is separated from the optic thalamus by a similar band of white fibres, the other part of the “internal capsule.” External to it we find the external capsule. What is the Claustrum ? A leaf-like mass of grey matter, external to the lenti- cular nucleus, and separated from it by the external capsule. External to it we find the ‘‘island of Reil.” Hence, from the middle line of the brain outwards, we find the following parts— 1. “Optic thalamus” and “ Nucleus caudatus.” 2, “Internal capsule.” 3. “ Nucleus lenticularis.” 4. “Outer capsule.” »). “The claustrum.” “A strand of white fibres.” The grey matter of the “island of Reil.” PhS What is the Nature of the Internal Capsule ? It is a narrow band of white matter close to the base of the brain, immediately above the crura. It is formed by the fibres of the corona rudiuta coming from, or going to, the grey matter of the cortex; the fibres are collected into a compact band which has a very intimate relation with the basal ganglia. 42 What are its Parts and their Function ? 1. It consists of a POSTERIOR PART, which lies between the optic thalamus and the lenticular nucleus. Its posterior third is sensory, its anterior two-thirds motor and trophic. 2. The aNTERIOR PART lies between the nucleus lenti- cularis and the nucleus caudatus; this part is probably concerned with the psychological functions of the brain. 3. A GENU, connecting the two parts. What are the Corpora Quadrigemina and their Connections ? They are four rounded tubercules placed in pairs, on each side of the middle line above the aqueduct of Sylvius. The anterior pair are called the nates, the posterior pair the testes. From them pass the anterior and posterior brachia—the anterior passing to the “corpora geniculata” and thence to the optic tracts of which they are the direct roots ; the posterior brachia are lost beneath the “corpora geniculata interna.” They are thus related to— . The cerebrum, by the anterior brachia. . The olivary fasciculus. . The optic tracts. . The third and fourth nerves. a He Oo Lo What are their supposed Functions ? 1. They have a very intimate relation to the sense of sight. Homologues of them exist in all vertebrata, and they always give origin to the optic nerves, and in size bear a direct relation to the animal’s power of sight. In birds there are only two, but they are very large, especially in those that have great powers of sight. In the mole the posterior pair are well developed, the anterior pair are rudimentary. Injury to the optic nerves causes the an- terior pair to waste, but leaves the posterior pair unaltered 43 Hence it is the anterior pair that are specially related to the sense of sight. 2. They are centres for movement of the eye and pupil. 3. They are probably centres concerned in balancing the body. 4. Centres for inhibiting spinal reflex action. THE CEREBELLUM. What are the Parts of the Cerebellum ? Two lateral hemispheres, and a central structure called the VERMIFORM PRocEss. The central lobe is the only one found in birds, reptiles, and fishes. The vermiform process lies at the bottom of a deep fossa, the vallecula. Name the Lobes of the Cerebellum. 1. On the upPER surface— (1) Central. (2) Anterior superior, or quadrate. (3) Posterior superior. 2. On the unDER surface— (1) Posterior inferior. (2) The slender. (3) The biventral. (4) The amygdaloid. (5) The flocculus. 3. The SUPERIOR VERMIFORM PROCESS— (1) Central lobe. (2) Monticulus cerebelli. (3) Commissura simplex, 4, The INFERIOR VERMIFORM PROCESS— (1) Tuber valvule. (2) The pyramid. (3) The uvula. (4) The nodule, or laminated tubercle. 4A What are the Peduneles of the Cerebellum ? 1. The supERior, or crura ad cerebrum, they form the lateral boundaries of the upper part of the 4th ventricle. 2. The MIDDLE, or crura ad pontem; they form the superficial and deep transverse fibres of the pons. 3. The INFsRIOR, or crura ad medullam, formed by the restiform bodies, and bounded by the lower lateral part of the 4th ventricle. Describe the Grey Matter of the Cerebellum. On the cortex it covers the surface and also lines the sides, and passes across the bottom of its various fissures and sulci, so that it is like a thin lamina folded on itself in a series of leaves or plates. On vertical mesial section, it shows a tree-like appearance, forming what is known as the arBor vitzZ. The principal grey mass in the interior is called the CoRPUS DENTATUM. What is the Minute Structure of the Grey Matter ? 1. The outer LAYER, consists of neuroglia, nerve cells, and nerve cell processes, 2. The inner Layer, called the granular layer, “ rust- coloured layer” (Turner)—consists of nucleated corpuscles, rounded or angular, embedded in a matrix of fine interlacing fibrils. 3. The mmppLe Layer, is formed by the cells of Purkinje (“antler cells”). These are large flask-shaped cells set at right angles to the surface of the cerebellum. Their central end gives off a single unbranched process; the outer end gives off a large process that branches like the horns of a deer, sending fine processes up to the outer layer of the cortex. 45 What are the Supposed Functions of the Cerebellum ? 1. It is probably a centre for the co-ordination of mus- cular movements, such as walking, etc. (Flourens). 2. It is also concerned in equilibriation. What are the probable Sensations that enable the Body to maintain its Equilibrium ? 1. The tactile sense. 2. The muscular sense. 3. The visual sense. 4, The semi-circular canals. What are the two Chief Theories as to the Uses of the Semi-ctrcular Canals ? 1. The “sraticaL THEORY ”—that they are the peripheral end organs of a sensory apparatus, for enabling the animal to maintain its head in a state of equilibrium. 2, The “ Kinetic tHEoRY” (Crum-Brown). Give a Short Outline of the Development of the Brain and Spinal Cord. In the development of the human embryo, there is formed the BLASTODERM oY GERMINAL MEMBRANE, consisting of three layers of cells— 1. Epiblast. 2. Mesoblast. 3. Hypoblast. It is from the epzblust that the brain and spinal cord are developed. On the dorsal aspect of the embyro two ridges appear with a groove between—the primitive or medullary groove - the ridges are the medullary folds or dorsal lamine. 46 The lamine ultimately meet in the middle line on the dorsal aspect, blending together and forming a tube lined with epiblastic cells; the tube is called the primitive medul- lary tube or neural canal. It is from this tube, with its lining of epiblastic cells, that the brain and spinal cord are developed; the cells forming the solid parts, the cavity remaining as the central canal of the cord, and the various ventricles—with the exception of the 5th ventricle of the brain. The Brain is developed from the anterior end of the primitive medullary tube; at first it dilates and then two constrictions appear, producing the ‘ anterior,” ‘“ middle,” and “posterior” cerebral vesicles. The posterior cerebral vesicle gives rise to the medulla, pons, and cerebellum. The middle cerebral vesicle—in its roof are formed the “corpora quadrigemina ;” in its floor, the “crura cerebri;” while the original central canal remains as the ‘“ aqueduct of Sylvius.” The anterior cerebral vesicle—the sides of this vesicle become thickened, and form the ‘‘ optic thalami,” while part of the original cavity remains as the third ventricle. From the anterior and lateral part of this vesicle two processes are given off, which grow enormously, and form the ‘‘corpora striata” and cerebral hemispheres, so that these hemispheres are mere offshoots from the anterior cerebral vesicle. They, in turn, give off another smaller process, which is developed into the olfactory bulb with its peduncle. The 5th ventricle, as already stated, differs from the others in not being a part of the primitive medullary tube, but is simply a part of the great longitudinal fissure which has become enclosed in the process of development. REPRODUCTION. Male Organs. Describe the General Structure of the Testicle. The TESTICLE is enclosed in a strong fibrous capsule, the tunica albuginea. Along its posterior border a specially strong prolongation is given off, the meddastinum testis, or corpus Highmorianum. From the corpus spring numerous septa of connective tissue, dividing it into a number of compartments, and in these the seminal tubes are lodged. Name the Parts of the Seminal Tubules. They begin in blind ends or anastomosing loops, and are at first very much convoluted, but as they approach the mediastinum testis they become straighter, forming the— 1, Vasa REcTA.—In the mediastinum they form a network, the 2, Rete Testis ; from this the 3. VASA EFFERENTIA arise; and, becoming much convoluted, form the 4. Cont vascuLosi; then comes the 5. Epipipymus, with its head, body, and tail; from which arises the 6. VAS DEFERENS. How are Spermatozoa Developed ? The tubules at the active part of the gland are lined by several layers of polyhedral cells, known as the ouTER and the INNER seminal cells. The inner cells form several layers, and show very abundantly the process of indirect division or karyokinesis ; in consequence of this many small “daughter cells” are 438 formed, and those next the lumen are transformed into spermatozoa, and are hence called spermatoblasts. They first become pear-shaped, the nucleus passing to one end— this end becoming flattened and thin. These are young spermatozoa, the nucleated extremity being the head. They become arranged in peculiar fan-shaped groups, the head towards the inner seminal cells, and the other end directed into the lumen of the tube. What are the Parts of a Full-grown Spermatozoa ? 1. A weap, the nucleus of the original spermatoblast. 2, A rod-shaped MIDDLE Pincg, derived directly from the cell body of the spermatoblast ; sometimes there is a spiral thread around this part. 3. A long hair-like ram, Female Organs. Give a General Description of the Ovary. It consists of a stroma of fibrous connective tissue in bundles, blood-vessels, and bundles of non-striped muscular tissue. Embedded in the stroma we find the “ Graafian follicles,” and streaks or groups of polyhedral cells, each with a spherical nucleus—“ interstitial epithelial cells.” Various layers are distinguished in the ovary— 1. It is covered by a single layer of short coLUuMNAR EPITHELIAL CELLS, continuous at the ‘white line” with the endothelium of the peritoneum; these cells are known as gerninal epithelium, because it is from them that the ova are developed. 2. The atpucinea.—This is the most peripheral layer of the stroma, not containing any ‘“Graafian follicles,” 3. The corticaL Layer (Schrén).—This is a layer con- taining the smallest ‘“Graafian follicles,” in small groups separated by the stroma. 49 4. From the cortical layer towards the centre of the ovary, we find embedded in the stroma isolated ‘“ Graafian follicles” of various sizes, increasing from the former to the latter. What are the Parts of a fully-formed Graafian Follicle ? 1. A TUNICA FIBROSA. 2. A BASEMENT MEMBRANE. 3. A TUNICA GRANULOSA, inside the basement membrane, consisting of epithelial cells. At one part these cells are collected into a heap, called the discus proligerus, in which is embedded the ovum. 4. The cavity of the follicle is filled with Liquor FOLLICULI. Name the Parts of the Ovum. It is simply a modified epithelial cell, and consists of— 1. The zona PeLLucipa, or cell wall, with vertical striations. 2. The YELK, or VITELLUS—the cell substance or protoplasm. 3. The GERMINAL VESICLE, or nucleus. 4, The GERMINAL Spot, or nucleolus. The ova are developed from the GERMINAL CELLS covering the surface of the ovary: these enlarge and grow down into the stroma, while the stroma grows up and includes them. A chief cell becomes the ovum, while the rest becomes the TUNICA GRANULOSA. What is the Fate of the Graafian Follicle? Before menstruation, one or more ripens, and becomes very hyperemic. They therefore grow rapidly, and the liquor increases to such a degree that they reach the sur- face of the ovary and, during menstruation, burst at a superficial point, and the ovum with its discus proligerus is ejected and brought into contact with the abdominal ostium of the Fallopian tube. D 50 What happens to the Follicle after this ? The cavity collapses, blood is effused, and the follicle is converted into a CORPUS LUTEUM by an active multiplication of the cells of the tunica granulosa; new capillaries shoot in, the cells undergo fatty degeneration, become gradually absorbed, leaving a small spot of cicatricial tissue. What happens should Pregnancy occur ? The coRPUS LUTEUM in that case is much larger, and takes a much longer time in its development and disappearance. What Changes occur in the Ovum before Impregnation ? The germinal vesicle becomes corrugated, and seems about to break up: an oval body forms with its poles directed to the vitelline membrane—the “PoLaR BoDY.” By and by the protoplasm becomes radiate in disposition, and the FEMALE PRO-NUCLEUS is formed. Briefly state the Leading Changes after Impregqnation. 1. After the entrance of spermatozoa the male pro-nucleus is formed, and this unites with the female pro-nucleus. 2. Segmentation into 2, 4,6, 8, . . . . divisions, forming the MoruLA or mulberry mass. 3. Formation of the blastodermic membrane by arrange- ment of the cells under the vitelline membrane; this consists of two layers—the mPIBLasT and HYPOBLAST, and in the centre is a cavity containing the “secondary yelk.” The blastoderm is vestcuLar forming a complete sac, and is, when fully formed, TRIPLO-BLASTIC. 4, Formation of the germinal or embryonal area, with its area pellucida and area opaca, and primitive streak. 5. Formation of the MEsopLast—the third and middle layer of the blastodermic membrane. ol 6. Formation of the notochord, medullary groove, and medullary folds or dorsal laminze, and speedy conversion of the groove into the NEURAL CANAL, due to its enclosure by the DORSAL LAMIN®. 7. Splitting of the mesoblast, and union partly with the EXTERNAL, partly with the inTeRNAL layers, forming the somato-pleure and splanchno-pleure, the cavity between them being the common pleuro-peritoneal cavity. 8. Development of the umbilical vesicle with its duct (‘‘vitelline duct”) from the splanchno-pleure. This is continuous with the wall of the intestine, and is the seat of the first circulation. The yelk is absorbed to nourish the embryo in its very early stage. 9. Formation of the alimentary canal (pharynx, gullet, stomach, intestine), from the splanchno-pleure. 10. Enclosure of the general body cavity (HH®MAL CANAL as opposed to the NEURAL CANAL) by the somato-pleure, which forms the hemal arch. What is the Notochord ov Chorda Dorsalis ? It is an axial column of cells, derived from the mesoblast, lying just beneath the medullary groove, and occupying the place of the future bodies of the vertebree. Around it the bodies of the vertebre are developed; after its enclosure it disappears, no trace being left except the soft pulpy centres of the inter-vertebral discs. In some fishes, however, it is persistent—as in the case of the lancelet, and some cyclo-stomatous fishes. Name the Structures derived from the Three Layers of the Blastoderm. From the Eprsrast— 1. Epidermis. 2, Epithelium of the Nose and Mouth. 3. Brain, Spinal Cord, and Nerves. 4. Parts of the Eye and Ear. 52 From the Hypopuast— 1. Epithelium of the Pharynx, and Alimentary Canal below it. 2. Epithelium of Lungs, Urinary Bladder and Urethra. From the MrsopLtast— All other Tissues and Organs. How is the Amnion Formed ? It is formed by two hollow prolongations of the somato- pleure backwards over the embryo, the converging folds meeting at the “amniotic umbilicus.” The inner division becomes the sac of the TRUE amnion—a closed and complete serous sac. The outer division forms the FALSE amnion, and becomes the subzonal membrane. The true amnion becomes distended with a serous fluid. What ts its Use ? Its use is that of a ‘“water-bag,” to diffuse pressure, and protect the foetus from injury. Describe the Allantois or Urinary Vesicle. It is developed as a blind bud from the lower end of the alimentary canal—i.e., from the splanchno-pleure. It grows along the umbilical duct into the false amniotic space, and against the subzonal membrane. What is its Use ? It unites the true and the false amnion. The urinary bladder, urachus, umbilical cord, and foetal part of the placenta are developed from it. How is the Chorion formed ? It is developed from the vitelline membrane, which sends processes (villi) into the decidua reflexa and serotina. It is thus the most external of the foetal membranes. The villi are at first developed equally all over the chorion, but 53 those lying in the decidua reflexa become absorbed ; those in the decidua serotina remain permanent. The villi are at first hollow, but the allantois grows round, and from it blood-vessels and connective tissue shoot into them. The villi disappear everywhere, except where the feetal part of the placenta is formed. The maternal part of the placenta is developed from the mucous membrane of the uterus—the decidua serotina. Give a Short Account of the Development of the Heart. The heart is at first represented by two tubes placed side by side, which very soon fuse into a single tube. Two transverse constrictions appear in the tube, dividing it into three chambers—PriMITIVE AURICLE, ARTERIAL BULB (truncus communis arteriosus), and PRIMITIVE VENTRICLE. About the third week of intra-uterine life the heart becomes doubled upon itself, and represents the permanent condition found in fishes. A septum appears about the sixth week, which grows upwards from the aper of the ventricle, dividing the single cavity into two; this septum should be complete about the eighth week. Occasionally it is not completed at all, so that a permanent opening remains between the two ventricles, towards the base of the heart—the normal form of heart in the chelonia and scaly reptiles. After the ventricular division is completed, a septum appears at the upper part of the single auricle, and grows downwards, dividing it into two auricles; an opening, how- ever, exists in this septum during the whole of intra-uterine life, called the FoRaAmEN ovate. It should close up a few days after birth. A partition also grows in the aRTERIAL BULB, dividing it into the ascending aorta, and the trunk of the pulmonary artery. Sometimes this septum is deficient, so that the blood in the two tubes is more or less mixed. 54 Give a Short Account of the Vascular Arches. The bulbus arteriosus bifurcates into the two ventral aortic roots. The arches these form make the first pair of vascular arches. As the neck lengthens so do these, and in the concavity other four arches appear. The first pair pass to the first visceral arch, where the lower jaw is developed; the second, third, and fourth into the other arches. There are five arches on each side— The first and second atrophy. The third forms the internal carotids. The fourth Lerr becomes the arch of the aorta. The fourth rigur becomes the innominate artery, and part of the right subclavian. The fifth Lerr becomes the ductus arteriosus. The fifth ricHr disappears. These vascular arches have a general resemblance to the branchial arteries in the gills of fishes and amphibia, but in man and the higher vertebrates gills are not formed in connection with them. Explain the “ Recurrent” Branches of the Vagus. At first the heart is in the neck, and the vagus gives off its recurrent branch opposite the fifth vascular arch, round which it turns to the larynx. As the heart sinks down into the chest, this branch is stretched and as the fifth right arch disappears, the right nerve turns round the fourth right arch —7ze., the first part of the subclavian. The fifth left arch remains as the ductus arteriosus, and the left nerve bends below this before it ascends behind the arch of the aorta. Name some of the Early Veins of the Fetus. The first veins are the OMPHALO-MESENTERIC, from the vascular area in the wall of the umbilical vesicle ; they join and open into the primitive auricle. 55 Then, in the wall of the chorion, two UMBILICAL veins appear about the fourth week. At the fifth week one dis- appears, and the other remains as the umbilical vein, The omphalo-mesenteric and umbilical veins are viscEraL veins. There are also PARIETAL veins—the cardinal and the jugular. The carDINAL veins return the blood from the Wolffian bodies and the walls of the trunk. Two PRIMITIVE JUGULAR veins are developed in the head and neck, and return the blood from these regions. The primitive jugular and car- dinal vein, on each side, join in the cervico-thoracic region to form a vein called the “duct of Cuvier.” Describe the Fetal Circulation. The blood from the inferior vena cava is mixed—impure from the lower part of the body, and purified from the placenta. It flows into the right auricle, and, guided by the Eustachian valve, passes through the patent foramen ovale into the left auricle, then to the left ventricle, and thence to the head, neck, and upper limbs, very little passing through the descending aorta. The blood from the superior vena cava is entirely venous, and passes into the right auricle, then to the right ventricle, and into pulmonary artery, and passes through the puctus ARTERIOSUS into the descending aorta, very little passing into the right and left pulmonary arteries. This blood supplies the lower parts of the body, and then passes to the placenta to be purified, by means of the hypo-gastric arteries. From the placenta the blood is returned by the umbilical vein. This vein, when it reaches the liver, divides into two branches—one communicates with the portal vein; the other, the pucrus veNosus, joins the inferior vena cava. What are the Wolffian Bodies ? They are the PRIMORDIAL KIDNEYS. They appear about the third week, being formed from the intermediate cell mass 56 of the mesoblast. In this a tube appears with diverticuli and vascular glomeruli. The duct opens into the cloaca. Up to the sixth or seventh week, they fulfil the office of kidneys; after that they atrophy. In the adult male, the “organ of Giraldes,” and the vas aberrans, are the remains of the Wolffian body; in the adult female, the “ grains of Folin,” near the parovarium, are its persistent representatives. The PERMANENT KIDNEYS arise from a mass of mesoblastic cells at the back of the Wolffian body. The URINARY BLADDER is formed by a dilatation of the intra-abdominal part of the allantois. How are the Genital Glands Developed ? They arise (7.e., the ovary and testes), in close relation to the Wolffian body, from the same “intermediate cell mass.” What is the Use of the “‘ Small Body” at the Summit of the Wolfian Body ? It is converted in the male into the vasa efferentia, coni vasculosi, and globus major of the epididymis. What is the Fate of the Duct of the Wolffian Body ? In the mats, it is converted into the body and globus minor of the epididymis, the vas deferens, and the common ejaculatory duct, whilst the vesicula seminalis arises as a diverticular prolongation from it. In the remaLe, it almost entirely disappears, but it forms in certain animals the tubes called the “canals of Gartner.” What is the Duct of Miiller ? It is a slender tube on each side lying on, but not communicating with, the Wolffian body. The anterior ends open into the peritoneal cavity; the posterior ends become fused together. In the male they almost entirely disappear, and are represented in the adult by the pedunculated hydatid of ot Morgagni, situated at the summit of the testicle, which is the persistent remains of the anTERIOR end of the duct, and by the vesicula prostatica (sinus procularis, or uterus masculinus ). In the female, they become greatly developed, and form the genital passages and tubes. The anterior end of each duct remains distinct, and form the Fallopian tubes ; whilst the posterior coalesced portions are converted into the uterus and vagina. Describe the Descent of the Testicle. The testicles are originally situated in the abdomen, below the kidneys and behind the peritoneum. Up to about the sixth month of feetal life, they are found below the kidney ; after that they gradually descend, so that, by the seventh month, they are situated behind the internal abdominal ring. During the. eighth month they pass through the canal, and by the end of the ninth month they have reached the bottom of the scrotum. In some mammals—e.g., the elephant—the testes remain permanently within the abdomen, and in the rodentia they only descend at each “rutting” season. How is the Foetus Nourished ? 1. By the contents of the umbilical vesicle. 2. By the villi of the chorion. 3. By the placenta. Name the Parts of the Umbilical Cord. . Amniotic sheath. . Two umbilical arteries. . Umbilical vein. . Pedicle of umbilical vesicle. . Remains of allantois. . Wharton’s jelly. What are the Functions of the Placenta? 1. It is a respiratory organ. 2. It is an alimentary organ. DOE Wb re 58 PHYSIOLOGICAL CHEMISTRY. Classify Proteids or Albumens, and state their Solubilattes. 1. Native ALBuUMEeNs—egg albumen, and serum albumen. 2. PEPTONES. Both the above are soluble in water. To distinguish, observe that heat coagulates native albumens, but does not coagulate peptones. 3. The GnosuLin FamiLty — globulin, fibrino-plastin, fibrinogen, myosin, vitelline. All these are soluble in dilute saline solutions, but not in pure water. 4, Dreriveo ALBUMENS—acid albumen, alkali albumen, casein. These are soluble in dilute acids or alkalies. 5. Fisnin—soluble on boiling with dilute hydrochloric acid, 6. CoaguLaTeD Proterps—soluble by the action of the gastric or the pancreatic juice. 7. LarpacEIn or AMYLOID SUBSTANCE: this is not soluble in either of the above menstrua. What Elements enter into the Composition of Proteids ? C. H. 0. N.S. State their General Reactions. . 1. Turn yellow on heating with strong nitric acid, and the colour deepens to amber-red on the addition of ammonia (‘‘xanthoproteic reaction ”). 2. With Millon’s reagent (nitrate and nitrite of mercury) a pink precipitate or mere colouration, either directly or on boiling. The colour may deepen to purple-red. 3. With a drop or two of a weak solution of copper sulphate and caustic soda, a violet colour. 4, With acetic acid and ferrocyanide of potassium, a white precipitate. og 5. Add acetic acid in excess, then sodium sulphate, and boil: a white precipitate is formed. 6. They turn a ray of polarised light to the left. Alcohol, tannic acid, and mercuric chloride, also pre- cipitate them. State the action of Trommer’s Solution on various substances. Trommer’s solution—a solution of copper sulphate and caustic soda—(“ Fehling’s solution” would act in the same way )— 1. With peptone, a purple-red colour. 2. With albumen, a violet colour. 3. With glucose, a foxy-red precipitate. What are the Tests for Egg-Albumen ? 1. Coagulation by heat: acids lower the temperature of coagulation, while alkalies heighten it. 2. Strong acids, especially nitric, coagulate it; also salts of the heavy metals—e.g., Hg Cl,. 3. It is coagulated by ether. 4. Acetic acid with ferrocyanide of potassium precipitate it—a delicate test. 5. Hexrrr’s test—Pour strong nitric acid into a test tube, and then gradually add a solution of albumen, so as to form a layer on the top; the albumen is coagulated at the point of contact with the acid in the form of a fine ring. A very useful test for detecting albumen in the urine. How does Serum-Albumen differ ? 1. It is not coagulated by ether. 2. The precipitate formed by nitric acid is soluble im excess—important, in testing the urine, to remember this. 3. If egg-albumen is introduced directly into the blood it is largely excreted as a foreign body: serum-albumen is not so. ov How would you Detect the presence of Sulphur in an Organic Solution ? Heat the substance with caustic potash in the presence of basic acetate of lead, when a brown or black colour will be developed. A sulphide is formed with the caustic potash, and then this forms the black sulphide of lead. How does Casein differ from Alkali-Albumen ? 1. Casein contains sulphur (detected by the above test) ; alkali-albumen does not. 2. Casein yields a phosphorus-containing body when - digested with gastric juice. What are the Characteristic Features of the Globulins ? 1. They are not soluble in distilled water (‘native albumens” are). 2. They are soluble in neutral saline solutions (e.g., 1 per cent. of NaCl), and are thus distinguished from “derived albumens.” An excess of salt precipitates them, which is not the case with the egg, or serum-albumen. What are the Special Features of Peptones ? 1. They are very soluble in water. 2. They are not coagulated by heat or mineral acids— unlike albumen. 3. Like albumen they are precipitated by tannic acid, HgCl,, and excess of alcohol. 4. Unlike all other proteids they are diffusible. How does Gelatin differ from Mucin ? It contains sulphur; mucin does not, in this respect resembling elastin. Chondrin, like gelatin, contains sulphur. The presence of sulphur is detected in the usual way. 62 What Changes occur in the Urine on standing ? It decomposes and an ammoniacal odour is developed : this is due to the decomposition of urea, producing ammonia, What are the Alkalies of the Urine? 1. Volatile, due to ammonium carbonate. 2. Fixed, due to the phosphate and carbonate of potas- sium and sodium. How would you distinguish them ? Dip yellow turmeric paper into the urine; a brown colour is produced. Heat this gently; if it disappears the alkali is volatile ; if not, it is fixed. give the Test for Chlorides. Acidify with nitric acid, and add excess of nitrate of silver; a white precipitate is produced, insoluble in nitric acid. What is the Test for Sulphates ? Treat with a solution of barium nitrate, when a white precipitate is produced, insoluble in nitric acid. What are the Phosphates of the Urine ? 1. SoLrusLE— (1) Alkaline sodium and potassium phosphates. (2) Acid sodium and potassium phosphates. 2. InsotusLeE—Phosphates of calcium and magnesium ; these are therefore precipitated in alkaline solutions. Dur- ing the decomposition of the urine ammonia is formed, and this unites with the magnesian phosphate, forming the “‘triple-phosphate” (2Mg0(NH,),0,P,0,). 63 Give Tests for Phosphates. 1. Heat urine, if there is a precipitate, and it dis- appears =uRaTES. If it does not disappear it must either be albumen or phosphates. Acidify with nitric acid: if it is dissolved, then it was pHosPHates; if not, it is albumen. Heat thus enables us to distinguish— (1) Urates. (2) Phosphates. (3) Albumen. 2. Another test is the NITRATE OF URANIUM. How ts the Quantity Estimated ? For this we require— 1. A “standard solution” of nitrate of uranium. 2. A solution of acetate of sodium with some free acetic acid. 3. A solution of ferrocyanide of potassium as “‘indicator.” How is Uric Acid recognised ? 1. The crystals are always coloured. 2. The “Murexipe” test. Evaporate with nitric acid by a gentle heat almost to dryness; let it cool, and then add a drop of a solution of ammonia, when a purple colour is produced. Urates form a “ brick -dust” deposit, which disappears on heating. How is the quantity of Urea Estimated? 1. By the “‘HYPOBROMITE OF sopa” METHOD (Russell and West). 2. Lrepie’s METHOD, by means of— (1) A standard solution of mercuric nitrate. (2) Asaturated solution of barium hydrate, and nitrate to precipitate the phosphates and sulphates. (3) A solution of sodium bicarbonate as “ indicator.” 2 pr 64 What are the Tests for Albumen ? 1. Heat to boiling point, a precipitate is formed. Add nitric acid, it is insoluble, and therefore it is not earthy phosphates. 2. Use Heller’s test (page 59). 3. Mercuric chloride gives a precipitate at once. When albumen is present, the urine is usually of low specific gravity. Give the Tests for Sugar in the Urine. 1. Moore’s test (page 61). 2. Trommer’s test (page 61). How is the Quantity Estimated ? 1. By Fehling’s solution, or 2. By the fermentation process. When sugar is present, the specific gravity of the urine is usually high. What are the Tests for the presence of Blood? 1. The microscope. 2. Tincture of guaiacum and ozonic ether. 3. The “‘hemin” test. How do you Detect the presence of Bile? Use Gmelin’s or Pettenkofer’s test (page 61). How would you Detect Pus? 1. Use the microscope. 2, Add caustic potash, the urine becomes stringy. How would you Detect Chyle ? The urine will be milky, or contain a soft coagulum. Examine for albumen, molecular fat, and the filaria sanguinis hominis. Edinburgh : Printed by E. & S. Livinasrone, 4 Melbourne Place.