Saunders' Question Compmd L6V ■5 OF ISTQLOGY Louis Leroy,MD. to 1^ =m ^!^=!^=^=T~ O: = — «^^^^=i— V ~ ^ »^^S ■g o c^^='* 5=^= CM S=^=o> SAUNDERS' QUEmON-COMpLNDS. NO. 25 Essentials of Histology BY LOUIS LEROY, B.S., M.D. Professor of Histology and Pathology in Vandcrbilt University, Medical and Dental Departments ; Professor of Pathology in University of Tennessee ; Bacteriologist to the State of Tennessee j Pathologist to Nashville City Hospital ARRANGED WITH QUESTIONS FOLLOWING EACH CHAPTER 106 ILLUSTRATIONS a;b(ra Eaition, 1Revi0e& anO EnlargeD PHILADELPHIA AND LONDON W. B. SAUNDERS & COMPANY J905 551 Set up, electrotyped, printed, and cop^'righted September, iqoo. Revised, reprinted, and recopyrigliteJ August, igo2. Reprinted May, 1903. Revised, reprinted, and recopyrighted August, 1905 Copyright, 1905. by W. B. Saunders & Company PRESS OF W. b. SAUNDERS &. COMPANY PHILADELPHIA This small 'volume is affectionately dedicated to mv Father. CHARLES L. A. LEROY PREFACE TO THE THIRD EDITION. In the present edition such modifications as have been found advisable or suggested themselves in the class-room since the former edition was published have been made, and a number of new illustrations have been added to facilitate reading the text by one not in pos- session of the actual microscopic specimens. This has been deemed desirable, as the purpose of the work is to furnish a means whereby the essentials of the subject may be acquired in a reasonably short time. For the benefit of the student the chapter on technic has also been further enlarged by the addition of a few well-tried and reliable methods, which can be followed successfully without any great outlay of material or equipment. The author desires to acknowledge his gratefulness to the profession for their cordial reception of the small volume accorded to past editions, and trusts that the present edition may, in its modest way, merit a continu- ation of their favor. Louis Lekoy. Nashville, Tenn., August, 1905. 11 Cornell University Library The original of tliis bool< is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003131137 PREFACE. The main intention in writing this work has been to collect witiiin a limited space and in a convenient form the essential facts in histology. At the same time the author has endeavored not to sacrifice clearness and intelligibility to the necessarily great condensation. It is hoped that the work may find a field of usefulness among graduates who have been some time away from the histologic laboratory, and become a trifle " rusty ; " among men who, having graduated at a time when the subject was not taught in most of the colleges, desire to acquire in a short time sufficient knoMdedge of histology to enable them understandingly to read path- ology ; and especially among students, to save them much of the inconvenience of taking voluminous notes, which always, to a greater or less extent, hampers a man and often causes him to lose some of the most impor- tant points in the endeavor to make a note of some trivial detail. Thanks are herewith tendered to my head assistants, R. H. Hough and F. B. Wilson, for their valuable aid — to the former, for the preparation of most of the illustrations from original sketches by the author ; to the latter-, for the arrangement of the manuscript and the preparation of many of the specimens from which the illustrations were made. 13 CONTENTS. CHAPTER I. PAGE Cells . . , 17 CHAPTER II. Bone 35 CHAPTER III. Muscles 47 CHAPTER IV. EPIT-HELItntt . . . 55 CHAPTER V. Neeves 60 CHAPTER VI. The Vascular System 68 CHAPTER VII. The Lymphatic System 84 CHAPTER VIII. The Digestive Tract ^ 96 CHAPTER IX. The Ueinaey Tract 124 CHAPTER X. The Male Generative Organs 138 15 16 CONTENTS. CHAPTER XI. PAGE The Female Geneeative Organs 150 CHAPTER XII. The Respiratory System 162 CHAPTER XIII. The Cutaxbous System ]69 CHAPTER XIV. The Eye 1~~ CHAPTER XV. The Ear 196 CHAPTER XVI. The Nasal Mucous Membrane . 205 CHAPTER XVir. The Central Nervous System 208 CHAPTER XVIII. Teohnic . . 220 INDEX ... 265 HISTOLOGY. CHAPTER I. Histology is the microscopic science of normal tis- sues. No matter how carefully we dissect the various tissues or organs of the body, we can with the unaided eye obtain but little knowledge of their ultimate com- position. An examination of the smallest portion of muscle, cartilage or bone, for instance, will reveal noth- ing which could not be seen in a gross specimen. The moment, however, we bring the microscope to bear upon any organ, an astonishing complexity of structure is revealed. The whole field of view is seen to be composed of minute bodies, differing greatly in appearance from the tissues they compose, and arranged in more or less definite order. These small bodies have received the name of cells, and are the histologic units. CELLS. A cell is a microscopic, protoplasmic mass, which, when typical or complete, contains cell-wall, cell-body, nucleus, nucleolus, and centrosome. Some cells lack one or more of the above, and are said to be atypical or not complete — e. g., the red cor- puscle contains usually neither nucleus, nucleolus, nor centrosome. The loss of these constituents can usually be traced to some stage of development. 2 17 18 CELLS. Cell-body. — The cell-liody, protoplasm, or cj^to- plasm, as its name implies, constitutes the largest part of the cell. It is surrounded by the cell-wall, and incloses the nucleus, nucleolus, and centrosome. The relative size and the internal structure of the cell-body vary greatly according to the locality from which the cell is taken. Wlicn examined under a high magnification, tlie cell-body is seen to consist of a network or reticu- him of exquisitely delicate fibers (the .Hpo)\gioplasm), the interstices of which are filled with a transparent. Fig. 1.— Diagram of a typical cell: ^, Cell-wall ; 5, cell-body; C, nucleus; .£", uucTeoUis ; Z', centrosome; a, spongioplasm ; 6, hyaloplasm ; c, metaplasm or microsomes ; d, exoplasm ; c, niieiear moiiibi'aue ; /, nuclear network or chroma- tin tiluments ; g, uuclear matrix ; A, nodal enlargements or net knots. homogeneous substance (the hyaloplasm). Besides these two substances, we usually find some small granules embedded in the hyaloplasm. These are usually be- lieved to be not a part of the cell, but rather the result of some vital change in the cell-substance, or in some cases to be partially assimilated substances from with- out. These granules have received the special name of metaplasm or microsomes. At the outer edge of the cell-body there is usually NUCLEUS.— CENTROSOME. i;i a narrow zone which is free from microsomes, and which has received the distinguishing name of exoplasm. Cell- wall. — The cell-wall is a delicate, structureless membrane enveloping the cell, and is derived from the cell-body. Nucleus. — The nucleus is an easily discernible, highly refracting body lying within the cell. It is quite complex in structure. Under a high magnifica- tion we are able to distinguish — {a) Nuclear Membrane. — A very thin membrane sur- rounding the nucleus (sometimes absent). (6) Nuclear Network. — A network of fine, strongly staining threads or filaments called chromatic fila- ments. These filaments exhibit along their course, and also at their points of intersection, certain thick- enings called nodal enlargements or net knots, (c) Nuclear Mcdrix. — A transparent, gelatinous, semi- fluid substance which occupies the space between the fibrils of the nuclear network. Nucleolus. — The nucleolus {\>\\xra\, nucleoli) is a small spheric body usually lying in the nuclear network. There may be several of these bodies in a single cell. Centrosome. — The centrosome is a very minute body usually situated in the nucleus and surrounded by a small clear area. During cell-division, however, it is found in the cell-body. Radiating from the centrosome to the chromatin filaments are found a number of straight lines, which are extremely fine and very difficult to see. The nucleus seems to be the part of the cell which contains and transmits the hereditary characteristics. The centrosome apparently controls the reproduction of the cell. Properties of the Cell. — As the body is but a col- lection of cells and intercellular substance, it is natural 20 CELLS. for us to expect to find the cell possessing certain attri- butes which characterize a living organism. Among these properties may be named — Metabolism — absorbing nutrition and excreting waste. Growth. Reproduction. Irritability — response to stimulation. Fig. 2.— Cells from various localities : a, Squamous epithelial cell fi'oia tongue; h, ciliated e|iitlielial cell from trachea; c, smooth muscle-cell from uterus; d, pigment cell from choroid coat of eye; e, eosiiiophile cell from blood: /, cell from liver. Motion — in some cells from place to place, in othor.s simply the extension and retraction of the cell-body. Faneti.on. — All normal cells have a certain life-work to perform, which is called their function. Origin of Cell. — All cells originate from a preexist- ing cell, and can not be generated spontaneously. MODES OF CELL-DIVISION. 21 Modes of Cell-division. — Two modes of cell-divi- sion are known — (1 ) direct divitsioii or budding ; (2) indi- rect dipision, karyokinesis, mitosis, or karyomitosis. Direct Division. — In the jjrocess of direct division a constriction occurs in the center of the cell which increases until the cell is split in two. Mitosis. — The process of indirect division is by far the more frequent and complicated method. The pro- cess is chiefly concerned in the nucleus, and has been divided into stages for the sake of convenience of de- scription, although, of course, in reality they merge imperceptibly from one into the other. Resting Stage. — In this stage the cell is, as has been described above, the chromatin filaments being arranged in a network. Close Skein. — The centrosome leaves the nucleus and divides into halves, which proceed to opposite poles of the cell and, together with their radiating lines and clear zone, are called attraction spheres. The nuclear network resolves itself into a fine close skein. Loose Skein, or Wreath. — The skein becomes less tangled and more distinct. It then resolves itself into a niunber of convolutions arranged as a wreath. (See Fig. 3.) Monaster. — The loops of the wreath separate, leaving a series of V-shaped threads with the apex of the V toward the center of the cell, giving a radiating or star- form, hence the name. Diaster. — Each V shape in the monaster now splits horizontally into exactly similar halves whose apices begin to diverge from their respective opposite halves and point toward the nearest attractive sphere. In this condition they present the appearance of two stars, each consisting of half the monaster, called daughter stars. 22 CELLS. Division of Nucleus. — These daughter stars separate from each otlier, going toward the attraction sphere, and the sides of the nucleus begin to constrict at a zone between the daughter stars. This constriction pro- gresses until we have the nucleus divided into two. Each half contains a daughter star and an attraction sphere. Division of Cell-body. — The cell-wall next assumes an indentation, which increases in size until the cell is I 1 I im 111 11 iryokinesis- a, Resting stage; &, close skein I I 1 r ] 1' r ige ; e, monaster stage; /, diaster stage; g, showing constriction of cell-body and two nuclei in loose skein ; h, cell divided completely, nuclei in resting stage. divided in two, a half of the original nucleus remaining in each half cell. Reverse Procedure. — The chromatin fibrils in the daughter stars now begin to undergo a reversed pro- cedure. The ends of the V-shaped fibers unite to form a wreath which tangles to become a close skein, which relapses into the nuclear network found in the resting stage. The nucleoli reappear. The attraction sphere once more enters the nucleus^ BEVELOPMENT. 23 and we have two cells, which are identical (except in size) with the parent cell. Time Required. — These changes, while complex, take place rapidly. In the human subject half an hour may be sufficient to complete the cycle. Development. — It has been stated above that cells are always produced by preexisting cells. This would lead us to suspect that the origin of the adult animal might be traced backward to a single cell. Ovum. — In man this origin may be traced to the Fig. 4. — Segmentation of ovum showing stages in tlie furtiintioii of ninllmiTj musses m cioss-soclion. ovum, a complete or typical cell generated in the ovary of the female. This cell passes down one of the Fallo- pian tubes to the uterus, meeting and uniting, on the way down, with a spermatozoon (the male element), provided conception has occurred. In the uterus it multiplies by indirect division into two, these two into four, then into eight, etc. For some time this process is kept up, the cells arranging them- selves to form a spheric mass, which has been termed the mulberry mass. Multiplication of some groups of cells now proceeding 24 CELLS. faster than others, the mass begins to flatten and lengthen, and eventually arranges itself into three super- im]5osed layers, called the primary germ layers. Primary Germ Layers. — The nppur layer is called the epiblast, or ectoderm ; the middle layer is called the m&soblast, or mesoderm. ; the lower layer, the hypohlaxf, or entoderm.. To these some writers have added a fourth layer, the parabJast. Fig. 5. — Formatiou of primary genn layers or blastodermic layers: a, Show- ing beginning difterenlialiun of cells; h, entodennic or bypohlastic cells folded upward; c, beginning formation of mesoblastic or mesoderm cells; rf, same process furtber advanced, showing the three distinct layers. Specialization. — The cells of these layers in their growth now begin to assume certain characteristic peculiarities, whicli differentiate them more and more and cause them to resemble the various tissues thev are to form. This process of specialization proceeds in a TISSUE. 25 regular and definite form, the same layer always pro- ducing the same structure in the adult. Tissue. — A tissue is an aggregation of similar cells and intercellular substance having a common function. The principal tissues originating from the primary germ layers are as follow (from Piersol) : From the cplblast, or ectoderm, are derived the e])i- thelium of the outer surface of the body, including that of the conjunctiva and of the anterior surface of the c^ornea, the external auditory canal, together with the epithelial appendage of the skin, as hair, nails, sebaceous and sweat-glands. The epithelium of the nasal tract, with its glands and communicating cavities. The epithelium of the mouth, and salivary and other glands discharging into the oral cavity. The enamel of the teeth. Tissues of the nervous system. The retina of the eye. The epithelium of the membranous labyrinth. The pituitary and pineal bodies. From the mesoblast : The connective tissues. Areola tissue. Tendons. Cartilage and bone. Dentin of teeth. The muscular tissue (except that of sweat-glands). The tissue of the vascular and lymphatic systems, with their endotheliinn and circulating cells. The sexual glands and their excretory passages as far as the termination of the ejaculator)^ ducts, the vagina, the kidneys, and ureter. From the hypoblant, or entoderm : The epithelium of the digestive tract, with that of all 26 CELLS. the glandular appendage, with the exception of those named as being of epiblastic origin. The epithelium of the respiratory tract.- The epithelium of urinary bladder and urethra. The epithelium of thyroid and thymus bodies (in the latter, Hassel's corpuscles). If we consider the parablast as one of the germ lay- ers, we must omit certain structures from the above classification, as follows : Tissue developed from parablast. Blood-vessels. Lymphatics and lymph-glands. Blood-corpuscles. Connective tissue. All the tissues of the body may, for convenience, be divided or classified into five groups — viz.: (1) Epithe- lial tissue ; (2) connective tissue ; (3) muscular tissue ; (4) nervous tissue ; (5) fluid tissues. The Connective Tissue. — The principal connective tissues are — mucous, white fibrous, yellow elastic, adi- pose, retiform, cartilage, bone, and dentin. Areola tissue is a tissue composed of white fibrous, yellow elastic, and adipose tissues in varying amounts. Mucous tissue is composed of large branching cells surrounded by a soft gelatinous substance (mucir). In the adult it is found in the vitreous humor of the eye. In the embryo it occurs in the umbilical cord and in the subcutaneous tissi^e. White fibrous tissue is made up of very fine, deli- cate fibrils, which run more or less parallel, do not branch, and are united to form bundles. These bundles may unite to form larger bundles, or may cross to form a regular network. Two kinds of cells are found in this tissue — known as the ivandering and the fixed cells. The fixed cells are irregularly stellate, and are direct THE CONNECTIVE TISSUE. 27 descendants of the mesoblastic cells. It is through the agency of these cells that the fibers are formed. The wandering, or migratory, cells are originally white blood-corpuscles that have wandered into the tissue by virtue of their ameboid motion. When boiled, white fibrous tissue yields gelatin. This tissue is found in a Fig. 6. — A, White fibrous tissue; a, nuclei of fixed and wandering connec- tive-tissue cells ; 6, ends of white fibers ; B, isolated fixed connective-tissue cell, highly magnified; C, wandering, or migratory, connective-tissue cell, highly magnified ; D, yellow elastic tissue, very highly magnified. great variety of locations, being probably the tissue most frequently met with in the body, serving as it does to form a framework for all the organs, to bind indi- vidual fibers of muscles and nerves, and as a support to blood-vessels, lymphatics, and nerves. Tendons. — The tendons are strong fibrous cords 28 CELLS. servint; to unite muscle to l)oiie. These cords are made up of numbers of bundles of dense white fibrous tissue, called tiecondarii bundles, and are continuous with the fibi-ous investment of the nuiscular fibers, which are bound together by oiri'ularly disposed bands of areola tissue. Each bundle of fibers can be subdivided into smaller bundles of very delicate iibrillse, called prH»«r?/ bundles. Between these primary bundles are numbers of large irregularly branched tendon cells, whose pro- cesses extend ai'ound and are firmly applied to the sides of the adjoining bundles, thereby aiding in holding them together. Blood-vessels and occasionally a small nerve- fiber are found in the areola tissue surrounding the secondary bundles. Yellow elastic tissue consists of branching fibers that form an elastic network in various locations. The fibers are under some tension, and when broken tend to curl ujj at the ends. This tissue usually occurs associ- ated with others of the connective-tissue group, as, for instance, in areola tissue. It may, however, be found nearly free from other admixtures in the ligamentum nuchie or in the subflava, in which case the fibers are much tliicker and larger than in other localities. It occurs in considerable amount in the subcutaneous tissue, arteries, lungs, capsules of organs, and in the mesentery, omentum, and other serous membranes. Adipose tissue is composed of large, clear, poorly stained spheroid cells, known as fat-cells, supported by white fibrous tissue. The fat-cells are derived from the fixed connective-tissue cells by a change of the protoplasm into an oily substance and the probable absorption of additional substances from Avithout. During this process the irregular cell-wall of the fixed connective-tissue cell is distended until it assumes a spheric shape, the nucleus meanwhile being pushed to THE CONNECTIVE TISSUE, 29 one side of tlie cell. Under adverse circumstances, as in starvation, the fat-cell may return to its original form. Crystals of fatty acid (margarin) are frequently seen in adipose tissue. This tissue occurs in varying amounts in areola tissue under the skin, between muscles, Fig. 7. — Adipose tissue: a, Fibrous tissue; 6, fat-cells; c, nucleus of fat-cells; d, fatty acid crystals in fat^cells. and surrounding nearly all the viscera with the excep- tion of the brain and spinal cord. Retiform tissue consists of a fine reticulum of fibrous tissue. The fibers are usually closely envoloiied by flat, irregular, connective-tissue cells. Adenoid tissue is retiform tissue that has entangled in its meshes numbers of small, round, lymphoid cells. 30 CELLS. CARTILAGE, There are three main varieties of cartilage — viz. : Hyaline, yellow elastic, and white fibrous. A fourth variety, cellular, is sometimes mentioned, but it is not found in man. All varieties are surrounded by a fibrocellular mem- brane called perichoiidrium. This membrane is divided Fig. 8, — Hyaline cartilage: a, Perichondrium; b, group of cartilage-cells; c, hyaline matrix. into an outer part, or fibrous layer, in which white fibrous tissue preponderates, and an inner, or cellular, layer, in which the connective-tissue cells occur in great numbers. These two layers merge insensibly into one another. Hyaline cartilage is composed of a firm, trans- lucent, bluish,* opalescent substance called matrix, or ground substance. HYALINE CARTILAGE. 31 This matrix, or ground suhstanoe, under ordinary means of observation appears to be entirely lioniogene- ous, but by special methods of preparation it may be resolved into very fine fibers united by a cement sub- stance. Scattered loosely through the matrix are found small spaces called Ifieamv. The portion of the matrix inmiediately surrounding Fig. 9. — White fibrocartilage : a, Perichondrium ; 6, ^roup of cartilage-cells ; c, white iibrous fibers and matrix. the lacunae is denser than usual and is called the oapsule. Within the lacunse lie the cartilage-cells, which are but specialized connective-tissue cells, the descendants of the cells in the lower layer of the perichondrium. They are large cells with granular nuclei and relatively good-sized cell-bodies, which frequently contain vacu- 32 CELLS. oles. As neither blood-vessels nor lymphatics have been positively demonstrated in human cartilage, its mode of nutrition is still a problem. Some of the lower animals, however, have minute channels, called canaliculi, connecting the lacuna; and conveying lymph to the cells ; reasoning by analogy, it is plausible to believe that such canaliculi may exist undemonstrated Fig. 10. — Yellow elastic cartilage : ff, Perichondrium ; 6, group of cartilage-cells ; c, Yellow elastic fibers iu stroma. as yet in the human tissue. Hyaline cartilage occurs in many localities where a strong yet flexible and re- sistent tissue is required — e. g., articular cartilage, costal cartilage, trachea and bronchi, the. Eustachian tube, and nose ; in the embryo it is the progenitor of the entire osseous system, with the exception of some of the flat and irregular bones of the skull. VARIOUS CARTILAGES. 33 White fibrous cartilage is essentially a hyaline car- tilage that has numerous bundles of white iibrous tissue coursing in all directions through its matrix. The cells are usually more sparsely distributed and the capsule denser than in the hyaline variety. These characteris- tics adapt the fibrous cartilage particularly to locations where great tensile strength combined with flexibility is required. Hence, we find it in the symphysis pubis, the intervertebral discs, the sternoclavicular and tempo- romaxillary articulations. Yellow elastic cartilage, or reticular cartilage, resembles hyaline cartilage in all respects save that it has in addition a network of yellow elastic fibers within its matrix. These fibers, as a rule, do not envelop the lacunae very closely, but leave clear areas around them, within which the cells can be easily seen. This addition of elastic fibers produces a tissue that is pli- able yet elastic. We find such tissue of special advan- tage in such localities as the external ear, the epiglottis, the arytenoid cartilage, and cartilage of Santorini or of Wrisberg. Cellular cartilage does not occur in the human subject, but may be found in some of the lower animals — e. g., the ear of rats and mice. It consists of very numerous and closely aggregated cartilage-cells that have no matrix proper surrounding them, but are re- tained in position by an intercellular cement substance. In old age, deposits of calcium salts may be found in any of the cartilages ; when so found, the cartilage is said to be calcified. By the action of prolonged boiling, chondrin can be extracted from the cartilage. 34 CELLS. QUESTIONS FOR CHAPTER I. 1. What is histology ? 2. What is a cell? 3. What structures does a typical cell contain ? 4. What are the cell-body ? spongioplasm ? hyaloplasm ? exo- plasm ? 5. What is the cell-wall ? 6. A\'hat are the nucleus? nuclear membrane? nuclear net- work ? nuclear matrix ? 7. What is the nucleolus? 8. What is the centrosome ? 9. Name the properties of the cell. 10. What is meant by metabolism ? growth ? reproduction ? irri- tability? motion? function? 11. How may a cell divide ? 12. What is meant by direct division ? 13. Name the synonyms of indirect division. 14. Describe the process of indirect cell-division. 15. "What is the origin of all cells? 16. What are the primary germ-layers ? 17. "NATiat tissues are developed from the epiblast? from the mesoblast ? from the hypoblast ? 18. What is meant by the parablast ? and what tissues are de- veloped from it ? 19. Name the five groups of tissues. 20. Name the connective tissues. 21. Describe mucous tissue, white fibrous tissue, tendon, yellow elastic tissue, adipose tissue, retiform tissue, adenoid tissue. 22. Name the varieties of cartilage. 23. "What is the perichondrium ? 24. Describe hyaline cartilage. 25. "Wliat is its matrix? "What are its lacunEE? "What is its capsule ? 26. Describe white fibrous cartilage. 27. Describe yellow elastic cartilage, 28. Describe cellular cartilage. CHAPTER II. BONE. Histologically, there are two types of bone, the compact and the spongy or cancellated. Covering the surface of bone, except at articular surfaces, we find a membrane, the periosteum, which is analogous to the perichondrium in cartilage, and, like it, consists of two layers — an outer fibrous and an inner or cellular. The outer layer consists principally of white fibrous tissue. The cellular layer contains many more connective-tissue cells, which gradually become more closely aggregated as we proceed toward the osseous surface, leaving no sharply defined line of demarcation between the two periosteal layers. As the bone is developed through the agency of the periosteal cells, they are sometimes called the osteogenetic cells, and the cellular layer, osteo- gcnrtic layer of the periosteum. Compact bone occurs in the shafts of all the long bones, at the inner and outer tables of the flat bones, and as a thin layer around the periphery of the irregu- lar bones. It is not a homogeneous structure, but is composed of thin layers of osseous substance, character- istically arranged, called lamellce. At the inner and ttie outer (medullary and subperiostal) surfaces are a number of lamellae of bone arranged concentrically with the periphery and called the circumferential or fundamental lamellae. Between the inner and outer circumferential lamellse we find the osseous sub- 35 36 BONE. stance, arranged in systems of concentric layers, each system virtually forming a tube with laminated walls. These tubes, for the most part, run parallel t(j the long axis of the bone, but at frequent intervals are united by diagonal branches, so that the lumens form a continu- ous network of canals. These canals communicate with the medullary cavity, and serve to transmit blood- vessels, nerves, and lymphatics, which are supported Fig. 11.— Transverse section of bone: a, External circumferential lamella; &, Haversian lamella; c, interstitial lamella; tl, internal circumferential lamella ; e, lacunar iu which lie the boiie-cells ; /, canaliculi joining above ; (?, Haversian canals. by a fine prolongation of the marrow reticulum. These tubes are called the Haversian canals ; the strata of their walls, the Haversian or special lamellas ; and the canals, together with their bounding lamellpe, con- tt'iits, and bone-cells (soon to be described), constitute the Haversian system. The more or less triangular spaces between adjacent Haversian systems are occujiied COMPACT BONE. 37 by indefinitely arranged layers of bone, called the interstitial or ground lamellse. Besides the Haver- sian canals there is another system of blood-channels. Tliese occnr scattered throngh the circumferential lamellie, and have received the name of Volkmann's canals. Their blood-vessels communicate both with Fig. 12.— Transverse section of ITiiver.siaii system; //, Iliivcrsian canal sui- rounded by lamellEe ; b, lacunic in tian»vcise section, Irom wbicb run numerous canaliculi. the surface of the bone and with the Haversian canals. There is no special arrangement of the bone around the \''olkmann's canals, as occurs around the Haversian canals, the former being simply spaces between the lamellae. Scattered between the individual lamellse of all three 38 BONE. types we find many elongated, thin spaces — the cell- spaces, or lacunas. In the circumferential lamellae their long axes correspond to the long axis of the bone. In the Haversian lamellaj the lacunar are slightly curved laterally, to conform to the general concentric annular arranwment. In the interstitial lamellae there seems to Fig. 13. — Longitudinal section of bone, showing l.ncunae in longitudinnl sfction, and numerous canaliculi : a, Lacunas. he no special arrangement, but in a general way the long axes of the lacunae correspond to that of the bone. Radiating in all directions and connecting the lacunae are minute canals, called canaliculi, which serve to transmit nutriment to the cells within the lacunae and SPONGY OR CANCELLATED BONE. 39 communicate with the lymphatics in the canals. While the canaliculi radiating from the lacunae of a Haversian system intercommunicate very freely, they rarely or never have any direct connection with the adjacent systems. In dry preparations of bone which have been ground to the requisite degree of thinness for microscopic ex- amination the lacunae and canaliculi become filled with particles of dirt and debris and appear black. In sections which have been decalcified, however, the lacunae are found to contain cells with long protoplasmic prolongations reaching into the canaliculi. TJiese are the true bone->cells, or bone=corpuscles. If some of the outer lamellae be forcibly torn off, there will be observed occasional fibers which penetrate the bone vertically to the surface. These fibers are the remains of old periosteum which in the process of bone forma- tion have failed to be displaced by the newly depos- ited subperiosteal bone. They are called perforating fibers of Sharpey. Spongy or cancellated bone differs from the com- pact in that the plates or spicules of which it is com- posed have no regular arrangement into a system, but unite irregularly to form a honeycombed mass, the cavi- ties of which are filled with marrow. The nutrition of the bone is derived from this marrow, hence there is no need for special blood-vessels. Spongy bone is found at the ends of the shafts of long bones and at the centers of the short and flat bones (the apophyses and diploe). At this place it might be well to call attention to several points in which bone and cartilage are analogous — viz. : 1. They both have a common mesoblastic origin. 2. Both are covered by similar membranes — peri- chondrium, periosteum. 40 BONE. 3. Both are composed of cells embedded in an indif- ferent matrix. 4. Both have similar functions — supportive frame- work. MARROW. There are two kinds of marrow : the red, which occurs in spongy bone, — principally in the flat bones, the ver- ts Fig. 14. — Cells from marrow: a. Myelocytes containing neutrophile granules; &, erytliroblasts ; c, eosinophiles ; t/, giant cell. tebrse, the sternum, and the ribs, — and the yellmr, which is found principally in the medullary cavities of the long bones of the extremities. Small prolongations also ex- tend into the larger Haversian canals. The red marrow contains a rather ildmitc reticulum or network of connective tissue, embedded in the inter- YELLOW MAEKOW. 41 stices of which are very numerous ct'IlK. Tliese cells differ widely, and may be divided into five principal classes — viz., myelocytes, crythroblasts, eosiiwjjhUcn, baso- philes, and giant cells. The myelocyte, myeloplax, or marrow cell, is a moderate-sized cell capable of ameboid motion ; it has a well-marked cell-body, and usually a single round nucleus. The cell-body frequently contains granules, which stain in neutral dyes (neutrophile granules). These cells are the most numerous in red marrow. The erythroblasts, or hematoblasts, are rather smaller cells than the preceding, and contain a relatively small cell body, yellowish in color, containing hemoglo- bin (the oxygen-carrying element of the red blood- corpuscles) and a nucleus, which is frequently seen in process of division. These cells develop the colored corpuscles of the blood. The eosinophiles, or acidophiles, resemble the myelocytes, but frequently have very irregularly shaped nuclei, and contain many large granules, which stain intensely with acid dyes (eosinophilic granules). The basophilic cells, plasma cells, or mastzellen, resemble the eosinophiles excepting that the contained granules stain only in a basic dye. These cells occur only infrequently. The giant cells are very large, irregularly shaped, ameboid cells, and usually contain many nuclei. They play an important part in the develof)ment of bone, and are then called osteoclasts. (See Develop)ing Bone.) The nuclei of all the preceding varieties of cells are frequently seen in process of karyokinesis. The yellow marrow differs from the red in that almost all the marrow-cells have been transformed into fat and the connective-tissue reticulum is slightly in- creased. 42 BONE. The marrow is well supplied with Wood-vessels, lymphatics, and nerves, which come from the periosteum through the Volkmann's and the Haversian canals. DEVELOPMENT OF BONE. Bone may be developed in one of two ways : 1 . From cariilage — the intracartilaginous develop- ment. 2. Under or between layers oi periosteum — the intra- membirmous derelopmeut. In the embryo, all the bones of the body, with the exception of a few in the head, are outlined by solid hyaline cartilage, and covered by a membrane — the primary periosteum — having the same structure as the perichondrium in other places. The development of adult bone from these cartilages begins at certain con- stant and well-defined points, which are called centers of ossification, and are usually situated a short distance from the ends of the bones. The cartilage-cells at these points enlarge considerably and arrange themselves in longitudinal rows, the matrix meanwhile increasing somewhat in amount and becoming infiltrated with lime-salts ( primary calcification), and thus inclosing the cells in small calcareous compartments called primary areolae. While this is going on, small blood-vessels penetrate the cartilage, and upon reaching the vertical layers of cells, proceed to absorb the transverse plates of the primary areola% producing numerous vertical tunnels surrounded by walls of calcified matrix. These vessels are accompanied by numerous cells from the under layer of the periosteum, called the osteoblasts. During this process the cartilage-cells are probably absorbed. The osteoblasts in the tunnels now multiply greatly, and, arranging themselves around the tunnel walls, DEVELOPJrENT OF BOXE. 43 soorete around themselves a layer of bone. Within this fresh osteoblasts arrange themselves and secrete another layer of hon:\ This process is repeated until usually five or six concentric layers of bone, surround- ing the central blooij- vessels and some cells, liave been Fig. 15. — Developing bone, intracartilagiiinus: i, Periosteum; h, hyaline cartiliige ; c, small blood-vessel ; d, osteoblast ; e , osteoclast. deposited. These concentric layers of bone, containing the cells which produce them, and central vessels, tocrether with nerves and lymphatics, which develop a little later, constitute the Haversian systems of the adult bone. At this stage of the development the bone will 44 BONE. consist tln-oughout its thickness of Haversian systems ratlier loosfly lield tou;<'tlicr. A numher of very large, irregular, multinuclear cells (the osteoclasts) now ap- pear in the more central ]i()rtinn of the bone and proceed to canse the disintegration of the adjacent Haversian systems, tluis producing a longitudinal central canal of some size, which becomes the medullary cavity, and contains the eh'ments which go to produce the marrow. During the foregoing process the iunermost cells of the periosteum mnltij)ly and secrete a layer of bone around themselves ; a fresh number of cells are de- posited upon this, which in turn produces a second layer. This process maintains as long as the bone con- tinues to grow in transverse diameter, and produces thereby the adult ciiciimfotriitial liunclkc. The medullary cavity also increases in size, but as the subperiosteal bone is deposited a little more rapidly than the central portion is absorbed, the wall of the bone in- creases in thickness at the same time that it is growing in circumference. In the long bones the cartihigc proceeds to calcify from the n])per center of ossitlcatiou downward until it meets the bone ])roceeding from a lower center ol' ossi- fication upward to the junction of the shaft with the head of the bone. Here a band of cartilage (the epiphyseal cartilage) is met with, which continues to grow as fast as the process of ossificatitjn ascends. This causes the bone to grow in length while the epiphyseal cartilage maintains a constant thickness. A\'heu the bone has attained its maximum length, the cartilage finally becomes calcified also, and all subsequent increase in length is prevented. In the cancellated bones the honeycombed structure is produced in a manner similar to the tunneling out of the medullary canal, but the process is not so complete and the osteoclasts burrow in various directions. QUESTIONS. 45 The intramembranous method of development dif- fers from the ])re(!edinf); in that the ]K>sition of the adnlt bone is not mapped ont by the cartilage, but by a doubl(.' layer of periosteum with cellular lavers approximated. Between these layers branchinu; s[)ieules of a calcareous nature are formed, which are subsequently covered by osteogenetic cells from the periosteum. These cells proceed to secrete layers of bone about themselves, in mucii the same way tiiat occurs around the Haversian canals. As bone formation advances, blood-vessels make their way into the tissue, and are accompanied by (osteoclasts, which proceed to tunnel ont marrow spaces, as in the heads of the long bones. The inner and outer tables of dense bone are deposited by the subperiosteal mode, as are the circumferential lamelke in the long bones. The bones of the cranial vertex, the small bones of the face, and the inferior maxilla are the results of the intramembranous development. Dentin is a calcareous tissue constituting the largest part of the teeth. It has many points of similarity with bone, which will be considered at length when describing the teeth. Cementum is also an osseous substance consisting of several layers of calcareous material enclosing lacunae and bone corpuscles. It f(.)rms the outer coat of the roots of the teeth and is deposited by the cells of the alveolar periosteum. QUESTIONS FOR CHAPTER II. 29. Name the two types of bone. 30. What is the periosteum ? Give its structure, v ol. Describe the general arrangement of compact bone. ' 32. What are the circumferential lamella;? I 33. What are the Haversian lamella; ?>- 34. What are the Haversian canals? the interstitial lamellae?^ Volkmann's canals ? 46 BONE. 35. What are the lacunae ? 36. What are the canaliculi ? 37. Describe the appearance of a dried section of bone. 38. ^V^^at are the perforating fibers of Sharpey ? 39. How does spongy bone differ from compact? 40. Name the points of similarity between bone and cartilage. 41. Name the two varieties of marrow. 42. Name the types of cells found in red marrow. 43. Describe the myelocyte, the hematoblasts, the eosinophiles, the basophilic cells, the giant cells. 44. Describe the yellow marrow. 45. Name the two methods of bone development. 46. What are centers of ossification ? 47. What are osteoblasts ? osteoclasts ? 48. Describe the process of intracartilaginous bone development. 49. Describe the intramembranous method of bone develop- ment. CHAPTER III. MUSCLES. The muscular tissues form a group of specialized cells possessing contractility in a marked degree. They are all (with the exception of the small muscles of the sweat-glands) of mesoblastic origin. Three distinct types of muscle are recognized — -voluntary, smooth, and heart muscle. Voluntary, striated, or skeletal muscle is the most abundant of the three types. It forms all the skeletal muscles, and is under control of the will. When examined microscopically, it is seen to be composed of parallel cylindric fibers, which are about 5^|-g- of an inch wide, and vary from | of an inch to 1 1 inches in length. Each fiber is covered by a very delicate structureless membrane, corresponding to a cell- wall, called a sarcolemma. Under this sarcolemma and at the outer edge of the fiber are situated numerous oval nuclei, their long diameters parallel to the direc- tion of the fibers. If looked at with a moderately high power objective (;^-inch to ^-inch), each fiber will exhibit cross striatioivi, consisting of alternate dark and light bands. Under still higher magnification a dark line (the niembrmie of Krause) may be seen in the center of the light bands, and a lighter line (the median liiip of Hensen) in the center of the dark band is distin- guished. Fine longitudinal markings are also sometimes seen. 47 48 MUSCLES. It is possible by treating the fiber chemically to split it, along the longitudinal markings, into fine fibrillse, called sarcostyles, or transversely along the membrane of Krause into discs, each of which contains a dark band with half a light band above and below. Fig. IG. — Voluntary rauscle: J, Three voluntary tihers in long sections; n, three voluntary inuscle-tiliers ; 6, nuclei of same; c, libiuus tissue between the tihers (eudomysiuTu) ; tl, lihers se[)arateil in lo sarcostyles. B, Fiber, diagram- malic ; a, dark band ; b, lijjht band ; c, median line of Heiisen ; (/, membrane of Ki-aust^; r, sarcoleinma ; /, nucleus. C. — (i, liigbt band; b, dark band; e, cr)nl raeting elements; d, row of dots composing the membrane of Krause; r, slight narrowing of contracting element aiding in production of median line of liensen. By combining the two processes the fibers can be resolved into numerous small prisms, known as sarcous elements. This division, however, is entirelv artifi- cial. In reality, the sarcostyles are composed of dark, granular, fusiform, contracting elements, with enlarge- VOLUNTARY .MUSCLE. 49 ments at each extremity, placed end to end. The spaces between tlie contracting elements are filled by a clear substance, called sarcoplasm. As the sarcostyles run parallel, with their comjDosing elements opposite each other, the appearance of the contiguous thick centers will be that of the dark band. The thin ends, sur- rounded by clear sarcoplasm, will show as the light band. The enlargements at the thin ends will produce a row of granules, which are so closely pla(;ed as to appear as a line — the membrane of Krause. The median line of Hensen is produced by a slight thinning of the contracting elements just at their centers, and by refraction of light. When a single muscle-fiber is cut transversely, stained, and examined under a rather high power it will be seen to be divided by a network of light lines into small segments which are known as " areas of Cohnheim." The individual fibers of volun- tary muscle are bound together by very delicate fibers of Fig. 17. — Transverse section of siiigl*-; fiber of voluntary muscle showing areas of Cohnheim : a, Sarcolemma ; b, nuclei of fiber ; c, areas of Cohnheiui ; d, clear lines dividing areas. white fibrous tissues, called the endomysium, to form bundles (the fasciculi). These fa ':ciculi are surrounded and bound to other fasciculi by a larger band of white fibrous tissue, called the perimysium, and these bundles 50 MUSCLES. are grouped together to form the large muscles as found in dissection, and are surrounded by a still larger mass of fibrous tissue (the epimysium), which constitutes the sheath of the muscle. These connective tissues servo also to support numerous nerves, blood- vessels, and lymphatics. The blood-vessels break up into capillaries, which form a fine network around the Fig. 18. — Transverse section of voluntary muscle : a, Cross-section of single muscle-tiber ; &, nuclei of rauscle-fibers; e, endomysium ; d, perimysium divid- ing muscle into fasciculi ; e, small artery ; /, small nerve in cross-section. individual muscle-fibers. The nerves terminate in special end-organs under the sarcolemma. SMOOTH MUSCLE. Smooth, plain, involuntary, or nonstriated muscle is found chiefly in the gastro-intestinal tract, the arteries around the various ducts, in the genito- uriilary tract, and in the skin and capsules of organs. It contracts slowly and is not subject to the will. Smooth SMOOTH MUSCLE. 51 muscle is composed of spindle-shaped cells, covered by a fine sheath, which, while varying considerably in size in various locations, may be said to average about 2-g-^ of an inch in length and g-jVcr of an inch in width. In the center of each fiber is an elongated, rod-shaped a — , Fig. 19. — Smooth muscle-fibers ; a, Nucleus. nucleus. Very fine longitudinal striations may be seen in especially favorable sections. The fibers are held together by cement substance and by interlacing of their ends. Occasionally, extremely fine spiculse branch at right angles to the fibers and aid in uniting them. 52 MUSCLES. HEART MUSCLE. Heart or cardiac muscle, as its name implies, is found only in the heart. It is composed of rectangular, branching cells, placed end to end, and joined by a small amount of clear cement substance. The fibers are more delicately cross -striated than the voluntary muscle, and, like the latter, possess fine longitudinal markings. Fig. 20. — Heart muscle, aemidiagrammatic: a, Nucleus; 6, branch of fibers; c. cross-striation. I A single oval nucleus is present in the center of each cell. Small amounts of fibrous tissue and capillaries are found between the cells. The following tabulated comparison of the three types of muscle may be of value in distinguishing them : QUESTIONS. 53 Voluntary. 1. Fibers long, J of an inch to li inches. 2. Fibers cylindric. 3. Fibera striated. 4. Fibers contain many nuclei. 5. Fibers contain nuclei at edge. 6. Nuclei are oval. 7. Fibers are united by fibrous tissue, called endomysium, perimysium, and epimy- sium, according to location. Voluntary. Fibers very long. Fibers cylindric. Fibers plainly striated. Fibers covered by sarco- lemma. Fibers contain many nuclei. Fibers contain nuclei at 7. Fibers united by fibrous tissue. Heart. 1. Fibers are rectangular. 2. Fibers are cross-striated. 3. Fibers are united by branch- ing and by cement sub- stance. Smooth. 1. Fibers shorter, j^j of an inch. 2. Fibers fusiform. 3. Fibers uustriated. 4. Fibers contain one nucleus. 5. Fibers contain nucleus at center. 6. Nuclei are elongated and rod -shaped. 7. Fibers are united by cement substance, interlacing of ends, and intercellular spiculae. Heart. 1. Fibers shorter. 2. Fibers rectangular. 3. Fibers more lightly striated. 4. Fibers have no sarcolemma. 5. Fibers contain single nuclei. 6. Fibers contain nuclei in cen- ter. 7. Fillers united by cement sub- stance and branching. Smooth. 1. Fibers are fusiform. 2. Fibers are unstriated. 3. Fibers are united by cement substance, by interlacing of ends, and by intercellular spiculae. QUESTIONS FOE CHAPTER III. 50. Name the varieties of muscle. 51. Give the size of the voluntary muscle-fiber. 52. What is the sarcolemma ? 53. What is the membrane of Krause ? 54. What is the median line of Hensen ? 55. What is the sarcous element ? 56. Describe the structure of a voluntary muscle-fiber. 57. What kind of tissue binds together the voluntary muscle- fibers? 54 MUSCLES. 58. What Is this fibrous tissue called in various locations? 59. Describe the blood supply of voluntary muscle. 60. How and where do the nerves terminate ? 61. Describe the nuclei of voluntary muscle. 62. What is the shape and size of smooth muscle-fibers? 63. Where is smooth muscle found ? 64. Describe the structure of smooth muscle. 65. How are the smooth muscle-fibers held together ? 66. What is the shape of cardiac muscle ? 67. Describe its structure. 68. How are the fibers held together ? 69. What are the differences between voluntary and smooth muscle ? voluntary and heart ? heart and smooth ? CHAPTEK IV. EPITHELIUM. Epithelial tissue is essentially a cellular tissue, the intercellular substance of which is of a cement nature. The cells vary greatly as to size, shape, arrangement, and function, but in a general way maj' be said to be rich in cell-body (i-ytoplasm), which is usually granular, and possess a clear, vesicular, smoothly outlined nucleus, containing nucleoli. With the exception of some of the cells of the genito-urinary tract (sexual glands and ducts, kidney, and ureters), all epithelium is either of epiblastic or hypoblastic origin. For sake of convenience we may classify epithelium in three ways — according to shape of cells, arrangement of cells, and function of cells: SquamoTis | ^W^^ scal^^s, OYoid. I. Polygonal, stellate. 1. Shape of cells : / C ^^1,™.':!™' Prismatic. Columnar S^^™*^' Py^^™- ^^ ^ ) iusiiorm, goblet - L shaped, ciliated. Pavement. 2. Arrangement of cells : -{ Transitional. Stratified. Protective. Propulsive. 3. Function of cells : } Conductive. Secretory. Absorptive. Nervous or neuro-epithelium. I. Squamous cells are thin and flattened ; they may 55 56 EPITHELIUM. ])o found in the outer layers of stratified and transitional epithelium, as in the skin, cornea, vagina, and mucous membranes of the buccal cavities, or in a single layer (pavement) chietiy lining the alveoli of the lungs, on the posterior suri'ace of the cornea, and on the anterior suri'ace of the iris. Tlie cells often vary somewhat in thickness and peripheral outline, and have been variously described as roundisli. ovoid, polygonal. Fig. 21. — Epithelial cell.s from vnrions localities; a, Squamous cell; 6, priclcle cell from skin ; c, coluiuiiar ciliated cells; (7, goblet cells; e, stratified epithelium. and stellate. Tlie stellate forms have numbers of very irregular prolongations, frequently branching. These cells frequently contain granules of pigment. Columnar cells are longer than they are broad, and are placed with their long diameters vertical to the surface. According to their cross-section, they will be cyllndric, prhinutic, or cuboid. As their vertical sec- CLASSIFICATION. 57 tions vary, they may appear pyriform, fusiform, goblet- shaped, or ciliated. Columnar cells may occur in a single layer, as liamg ducts, glands, and in the intestine ; or they may be stratified, as in the trachea. In some localities the free Fig. 22. — Pigmented epithelial cells from frog's epithelium : o, Large stellate cell the protoplasm of which is well filled with pigmeT)t. ends of the cells are covered by numbers of very deli- cate hair-like processes, called cilia. These cilia wave rapidly to and fro in a definite direction, with a whip- like motion, and serve to produce currents in fluids or to transport foreign particles. Ciliated cells are found 58 EPITHELIUM. in the nasal fossse, trachea, bronchi, and Fallopian tnbes, and in the central canal of the spinal cord. 2. According to the uses to which epithelium is adapted, the cells may vary in arrangement. In the intestine, lung alveoli, posterior surface of cornea, lining ducts of glands, kidney, urethra. Fallo- pian tubes, and central spinal canal, the cells occur in a single layer resting on underlying layei's of specialized fibrous tissue, called the basement membrane. To this arrangement the name of pavement epithelium may be given. Again, in other localities, as the skin, the mucous membrane of the mouth and vagina, the cornea, and the trachea, they are arranged in many superposed layers, and are called stratified epithelium. In a few places, as the pelvis of the kidney, the ureters, and the urinary bladder, an arrangement of cells only a few layers in thickness is found ; the outer layers of cells are not flattened to any extent, but are more cuboid or ovoid, while virtually but a variation of the stratified variety ; this arrangement has received the special name of transitional epithelium. 3. Epithelium may be further classified according to its function. The protective type would include such localities as the skin and the mucous membrane of the esophagus, in which the main function is to protect the underlying structures. The conductive is found lining ducts the chief function of which is to transmit or to retain secretions. Oiliak'd epithelium, as in the bronchi and Fallopian tubes, which causes currents in fluids and carries small particles of matter, may be termed propulsive. Cells such as occur in glands and in the gastro- intestinal tract, the main function of which is either QUESTIONS. 59 to secrete or to absorb, may be called secretory and absorptive respectively. In the organs of special sense — skin, tongue, nose, eye, and ear — certain types of epithelium are found which are very intimately connected with the nervous system. These cells possess some of the characteristics of both nerve and epithelium, and have received the compound name of neuro-epithelium. Besides the foregoing classes, there are some special- ized substances, as the hair, nails, and enamel of the teeth, which are epithelial derivatives, and will be considered under their appropriate heads. QUESTIONS FOR CHAPTER IV. 70. Describe the general characteristics of epithelium. 71. From what germ layers is it developed ? 72. How may it be classified ? 73. Give a classification with regard to the shape of the cell, the arrangement of cells, and the function of the cells. 74. Describe and give location in which squamous cells are found ; columnar cells. 75. What is pavement epithelium, and where is it found ? strat- ified epithelium ? transitional epithelium ? 76. What is meant by protective type, conductive type, ciliated, propulsive, secretory, and absorptive ? 77. What is meant by neuro-epithelium ? 78. Name the specialized epithelial structures. CHAPTEK V. NERVES. Nerves are long, highly specialized fibers originating in nerve-ceUs, carrying impulses, and usually terminat- ing in special end-organs. The combination of one nerve-fiber with its cell and terminals is called a neuron. It may probably safely be said that all true nerve tissue is developed from the epiblast or ectoderm. A nerve=cell is one of the largest cells in the body. It contains a large spheroid nucleus, rather poor in chromatin, hence staining not very deeply, and usually one or more well-marked nucleoli. The cell-body, or cytoplasm, contains a greater or less number of granules, which stain in a characteristic manner, and ai'e named chromophilic granules. The nerve-cells vary greatly in shape, occurring as unipolar (one pole or projection), bipolar, tripolar, and multipolar. One of the poles in the nerve-cell, called the axis= cylinder process, is enormously extended, and becomes the axis-cylinder of the nerve-fiber. The other jjrocesses of the cell may divide and sub- divide until a dense feltwork of interlacing fibers is fomied about the cell. These processes are called dendrites. Nerves are principally of two types — those consist- 60 MEDULLATEn FIBERS. 6,1 ing of the medullated or white, and those consisting of the nonmedulkded or (/ray jihern. The medullated fiber consists of a very delicate I'll Fig. 23. — Nerve: j4, Longitudinal single ■ liber, diagrammatic: a, axis- cylinder; 6, medullary sheath ; e, neurilemma ; rf, nucleus; e, node of Eanvier. B, Transverse section of nerve bundle: a, epineurium ; 6, perineurium; c, endoneuriura ; d, transverse section of medullated nerve-fiber. thread, the axis=cylinder, which is continuous through- out the length of the nerve, and is in reality a prolongation of the nerve-cell. The axis-cylinder is 62 NERVES. the portion of the nerve which transmits impulses. Enveloping the axis-cylinder is a fotty material (myelin), called the medullary sheath, or the white substance of Schwann. This medullary sheath begins a short distance from the nerve-cell and continues until close to the termination of the fiber. Surrounding the medullary sheath of the peripheral meduUated nerve-fibers is a delicate sheath, called the Fig. 24, — Various nerve-endings: a, Corpuscles of Vater, or Pacinian bodies, from mesentery; b, nerve-ending from voluntary muscle; c, compound tactile cell from bill of duck ; d, genital corpuscle from clitoris. neurilemma. In the central nervous system medullated fibers occur which have no neurilemma. About every -^ of an inch in the course of the nerve-fiber the neu- rilemma dips down to the axis-cylinder, thus forming periodic constrictions — the so-called nodes of Ranvier. At the under surface of the neurilemma are found the nuclei, one of which is placed in the center of each internodal segment. Special methods of staining dis- GANGLIA. 63 close small oblique markings in the white substance of" Schwann (the dvfts of Lantermanii), the exact signifi- cance of which has not been determined. In the perijjheral nerves the individual fibers are held together by fine fibrillse of fibrous tissue, called the endoneurium, and grouped into bundles {fasciculi), which are surrounded by a denser band of the fibrous tissue, which is in connection with that between the fibers. This tissue surrounding the fasciculi is named the perineurium. Numbers of fasciculi are grouped to- gether to form the nerve-trunks, as met '\^■ith in dissec- tion, and are bound together by a thick layer of fibrous tissue, called the nerve-sheath, or epineurium. In the central nervous system the nerve-fibers are held together by a specialized type of tissue, called neuroglia. This neuroglia tissue is composed of irreg- ular cells (neuroglia cells) with very many fine, radiating processes, which interlace with the processes of adjoin- ing cells to form a dense feltwork. NONMEDULLATED NERVE-FIBERS. The nonmedullated, gray, jiale, or MemaJe' s fliers differ from the medullated principally in that they have no medullary sheath, their nuclei are more numerous, and the fibers frequently inosculate and have occasional fusiform dilatations. These fibers occur principally in the sympathetic system, although occasional pale fibers are found asso- ciated with medullated nerves. GANGLIA. Fusiform enlargement occasionally occurs in the course of some of the nerve-trunks, more especially in 64 NERVES. the sympathetic nerve and in the sensory nodes of the spinal nerves. These enlargements are composed of nerve-fibers, connecting with large and rather spheric nerve-cells, and are called the ganglia. The ganglion cells are distributed mostly in more or less longitudinal rows, and usually have two nerve- fibers (an efferent and an afferent) connected at one pole. Some of the cells, however, are bipolar. When a medullated fiber joins a ganglion cell the medullary sheath disappears a short distance from the cell. In all nerves, however, the neurilemma continues, and forms a nucleated sheath for the ganglion cell. NERVE-ENDINGS. Nerves terminate in one of two ways : 1. By dividing into fine arborizations, called termi= nal plexuses. 2. By ending in special structures, called end= organs. The first type of termination is found in many of the sensory nerves of the skin, mucous membrane, and cornea. The ends of the fibers may lie between the epithelial cells, or may ramify in the basement mem- brane. Of the end-organs many types are known, occurring in the lower animals as well as in man. Some of the sensory fibers terminate in crescentic cells, called tactile cells. In many localities fibers terminate in complex ar- rangements of tactile cells, which are then called compound tactile cells. Some of the most important of these are : Corpuscles of Meissner, or tactile corpuscles of the shin, NERVE-ENDINGS. fji which occur in the papillae of the corium. These con- sist of a vertically elongated mass of compressed tactile cells, the upper portion of which is just below the epithelium and the lower portion of which gives entrance to the nerve-fibers. The Pacinian eorpuscles, or corpuscles of Vater, occur in many localities, as in the palms of the hands, the soles of the feet, the mesentery, and the genital organs. They are the largest of the terminal organs, sometimes reaching a size of -^^ of an inch (1.25 mm.). They are oval in shape, and consist of a series of concentric layers of fibrous tissue and hyaline elastic substance, inclosing a small clear space in the center, filled with a transparent, jelly-like material. The medullated fiber enters at one pole and loses its sheath, the axis-cylinder proceeding as a wavy line in the central space. The end-bulbs of Krause are found in the conjunctiva. They consist of a nucleated capsule, in which the axis- cylinder of the nerve-fiber is convoluted. They are much smaller than the preceding. The genital corpuscles of the clitoris and penis may be considered as a compound end-bulb, several end- bulbs, each connecting with a separate nerve-fiber, being partly fused together. Nerve-endings in Smooth Muscles. The nerves supplying the smooth muscles are of the nonmedullated variety, and are principally derived from the sympathetic system. The nerve-fibers break up into plexuses of axis-cylinders, which lie in the intercellular spaces. From these, fine processes enter the muscle- cells and terminate in or upon the nucleus. Nerve-endings in Voluntary Muscle. Both sensory and motor nerves are found in voluntary 66 NERVES. muscle. The sensory fibers form a network between the muscle-fibers, while the motor fibers enter them. When the motor fibers enter a muscle-fiber, they lose their medullary sheath, and the neurilemma blends with the sarcolemma of the muscle. The axis-cylinder now spreads out into a tortuous, irregularly bulbous, branching mass, embedded in a soft, nucleated, protoplasmic substance. This is called the sole plate, and lies upon the muscle substance just under the sarcolemma. Every muscle-fiber has one of these nerve-endings, and sometimes several. Nerve-endings in Tendons. Tendons have several types of nerve terminations : 1. Some medullated fibers, after running a short dis- tance in the tendon, terminate in a dilatation closely resembling the end-bulbs of Krause. 2. The tendon spindles consist of a dilated fusiform bundle of tendon fibers, which is entered by a very small medullated nerve-trunk. This nerve divides into its ultimate fibrillae, which ramify throughout the spindle and terminate in slightly bulbous enlargements. QUESTIONS FOE CHAPTER V. 79. What are nerves ? 80. What is a neuron ? 81. From what layer of the embryo are the nerves probably developed ? 82. Describe the nerve-cell. What are dendrites? 83. Name the two principal types of nerves. 84. Wliat is the axis-cylinder ? medullary sheath ? neurilemma? 85. Is the neurilemma ever absent in medullated fibers ? and If so, where ? 86. What are the nodes of Eanvier ? the clefts of Lantermann ? QUESTIONS. 67 87. Describe a medullated nerve-fiber. 88. Where are the nuclei situated ? 89. How are the nerve-fibers held together, and what are the supporting tissues called ? 90. Describe a nonniedullated nerve-fiber, and tell where they occur. 91. Describe a ganglion. 92. Name two methods of nerve termination. 93. What are tactile cells ? tactile corpuscles ? Pacinian corpus- cles ? end-bulbs of Krause ? 94. Genital corpuscles ? 9.5. Describe the nerve-endings in smooth muscle, voluntaiy muscle, and tendon. CHAPTER VI. THE VASCULAR SYSTEM. The blood-vessels compose a system of closed tubes, l''ig. 25. — Capillary network connecting small arteriole and vein: o, Small arte- riole; 6, vein; c, capillaries. oi vtesobludio orif/in, which are divided structurally into arteries, veins, and capillaries. 68 ARTERIES. 69 ARTERIES. An artery has tliree coats, called respectively outer, middle, and inner. The inner coat, serous coat, or tunica intima, consists of a single layer of thin, flat, elongated endothelial cells, united by a delicate cement substance, which rests upon a subendothelial layer of fibrous tissue. Surrounding this layer of fibrous tissue is a wavy band of yellow elastic tissue. In the larger arteries this elastic tissue forms a thick sheet, in which more or less irregular openings occur. It is then called the fenestrated membrane of Henle. Fig. 26.— Blood-vessel : A^ Tunica intima; B, tunica media; C, tunica ad- ventitia; a, eudothelial lining; 6, blood-corpuscles; c, fenestrated membrane of Henle. The middle coat, muscular coat, or tunica media, surrounds this fenestrated membrane of Henle, and consists principally of smooth muscle, most of which runs circularly around the artery. Some few fibers of fibrous and yellow elastic tissue are also found inter- spersed among the muscle-cells, especially in the larger arteries. The outer coat, fibrous coat, or tunica adventitia, 70 THE VASCULAR SYSTEM. consists of fibrous tissue in rather dense bundles, with occasional fibers of yellow elastic tissue. The inner coat presents a smooth surface, which offers scarcely any resistance to the blood current. The muscular coat is under control of the vaso- motor nerve system, and, by contracting or dilating, changes the size of the lumen, thereby regulating the amount of blood passing through a given vessel. The outer coat gives strength to the artery, and serves to sustain it in its relations to the adjacent tis- sues. ... -•) ^^^^ Ki^^^^HESfel^s^BSev S. - i ^. ^_ it ^Sm ^H Fig. 27. — Aorta showing elastic tissue stained by rcsorcin-fucbsin method. In the aorta and larger blood-vessels, whose caliber remains practically constant, the middle coat will be found to contain a relatively large amount of yellow elastic tissue, as has been noted. This elastic tissue permits a rapid expansion of the vessel-wall upon each systolic contraction of the heart, and while the heart is A^EINS— OAPILLAFvTES. 71 again filling (diastole) the gradual and constant con- traction of the clastic tissue in the vessel-wall forces the blood forward in a nn)re steady stream. It is not unusual to find at least three-fourths of the bulk of the middle coat of the aorta to consist of elastic tissue. VEINS. The veins differ from the arteries only in the rela- tively small size of their muscular coat and the large amount of fibrous coat. Their walls are thinner in proportion to the lumen, and when cut they tend to collapse. CAPILLARIES. The larger arteries branch repeatedly until the finest arterioles are reached, when they lose their outer two coats and continue as thin tubes consisting of only a single layer of endothelial cells, the continuation of the endothelial lining of the larger vessels. Occasionally, the endothelial cells do not fit together exactly, and small spaces occur, which are filled with cement sub- stance. These are called stigmata, and are probably the first places through which the white blood-corpus- cles pass in inflammations. The larger vessels are supplied %mth mdrition by smaller vessels, which ramify within their coats. These have received the name of vasa vasorum. Lymphatics also occur in the outer coat of the larger vessels, and some of the smaller blood-vessels are completely surrounded by narrow lymphatic spaces — the perivascular lymphatics. 72 THE VASCULAK SYSTEM. THE HEART. TJie lieart is lined by the endocardium, which is similar in structure and continuous with the tunica in- tima of the blood-vessels. Under this is the myocardium, or heart muscle, which has already been considered. The outer surface of the heart is covered by the pericardium, a serous membrane containing a mem- brane of fibrous tissue, on the free surface of which are flat, irregular endothelial cells. Tlie valves of the lieart are broad, flat rednpUcations of the endocardiimn, between the two layers of which is a plate of very tough, dense fibrous tissue. The heart contains many lymjihaiics, some of which run between the muscle-fibers ; others are found around the coronary arteries. Both mcdidlated and nonvieduUated nerve-fibers occur in abundance, the former being chiefly branches of tlie pvieumogastric ; the latter, from the sympatlietic sys- tem. Numerous ganglia are also found in the course of the nerves. THE BLOOD. The blood may be considered as a mesoblastic tissue consisting of cells with a fluid intercellular substance. The cellular elements of tlie blood are called cor- puscles ; the fluid portion, the plasma, or liquor sanguinis. The principal corpuscles are the colored, the colorless, and the blood platelets. Other forms that occur are the dust eorpxside.'i, the shadow.' eorptiscles, the mirrociftr,^, and THE BLOOD. 73 the spheric red corpuscles. The colored corpuscles, red corpuscles, or erythrocytes, are round, biconcave discs. When viewed singly under the microscope, they have a yellowish-green color, the characteristic red color of blood being produced only by the superposi- tion of great numbers of cells. Their number varies somewhat in different individuals, and is slightly greater in the male than in the female. A cubic millimeter (t5 ^^ ''■" inch) of blood in the male will contain, on an average, 5,000,000 colored blood-cells, whereas the female will average about 4,500,000. In man the red cells are singularly regular in size, measuring -^-^-^ of an inch (7.5 microns) in breadth and about Y2"^^^ of an inch (2.08 microns) in thickness at the edge. The thickness of the center depends upon the amount of concavity, and varies much in different cells. In stained preparations the center appears clear, and is called the "delle." Structurally, the colored cells are surrounded by a clear, extremely delicate limiting membrane (virtually a cell-wall), inclosing the body of the cell, the hemo= globin, which is the oxygen-carrying element. In the adult no nuclei are found in the colored cells, although in the embryo and a few days after birth some nucleated red cells occur. When allowed to remain quietly out- side the blood-vessels, they tend to arrange themselves into stacks, or rouleaux, resembling rolls of coin. Action of Reagents. Upon the addition of water to the blood the red cells swell up until they become spheric in outline, and lose their hemoglobin, which is dissolved out. When acted upon by dilute saline solutions, minute spines develop around the surface of the cell, giving it 74 THE VASCULAR SYSTEM. somewhat the appearance of a horse chestnut bur. Corpuscles in this condition are said to be crenated. If the strength of the solution be increased, the cells will eventually shrivel up into an unrecognizable mass. Almost all adds, especially acetic acid, decolorize the cells and cause them to become spheroid in outline. Tannic acid in a 1 % solution causes the hemoglo- bin to escape from the cell and to coagulate in minute beads at the edge of the limiting membrane. If the solution used is too strong, the hemoglobin will be coagulated within the cell. ^^0^' 0. -Cb c^^ -t®-^ Fig, 28. — Blood corpuscles from camel ; a. Red blood-cells ; b, ueutrophile cell ; c, lymphocyte. Colored Corpuscles in Other Animals. The red blood- cells of all mammals (with the excep- tion of the camel tribe) differ only in size. In the camel tribe the red- cells are biconcave, oi-a\, and have no nuclei. In birds and cold-blooded animals they are oval, biconvex and have well-marked usually elongated nuclei. The following is a table showing the size of the col- ored cells in various animals : THE BLOOD. 75 Proteus, Newt, Toad, Shark, Crocodile, Snake, Lizard, Ostrich, Electric eel, Pike, Pheasant, Perch, Pigeon, Humming-b: Elephant, Sloth, Whale, Camel, Man, Monkey, Dog, Guinea-pig, Bear, Eabbit, Cat, Pig, Horse, Sheep, Ox, Goat, Musk deer. ird jJi) of an inch (63.5 microns). sr-£ " (30.7 " ) TtiVs u (23.9 " )• 1 li TTT2 (1 (21.fi " )• rhi 11 (20.3 " ■ 1 ' i u (iy.6 " )• J-Bhn " 1( (16.7 " ). It'o " il (15.1 " ). 1 a (< (14.4 " ). IS TO 1( (12.5 " )• IlW " a (11.7 :: 1: ] (1 55S"¥ u (10.15 J At " (f ( 9.56 " )■ 1 li '' ( 9.375 " )■ .,'43 " £1 ( 9.2 " ). .»'57 " •' ( 8.6 " )• 1 1( u ( 8.0 " )■ 3Aj " a ( 7.6 " ). iMo of an inch ( 7.5 microns). 1 " 13^7 8 " ( 7.4 " )• 33ffTl (i ( 7.1 " )• TaV^ f 1 ' i \ jsVr " 11 ( 7.0 " ^ 1 'I 11 I 7.0 " 1 3"o"o^ 11 ( 6.25 li. { TrVu '' (1 ( 6.0 li 1 1 ( ' T6or " ( 5.9 " )• 1 (' (1 ( 5.0 " '1 rzVj " ( 4.8 *' )• 1 t( ■5-2311 (( ( 4.0 " ^ T5JZ3 (1 ( 2.4 U \' QW^ x^y Fig. 29.— Frog'a blood : a, Red corpuscles ; 6, white corpuscles. 76 THE VASCULAR SYSTEM. Colorless Blood-corpuscles. The colorless corpuscles, white blood-cells, or leukocytes, are briefly described as nucleated cells, .n! Fig. 30,— Cells of blood : a, Colored blood- corpuscles seen on the flat ; 6, on edge; e, in rouleau; d, blood platelets. 7 8 tig, 3i. — Amcljtii.i inovemciiL in wliite blood-cnrpiisck'. Tin' liiviwiiig^ were made of the same cell at intervals of one miuute and a iialf. averaging about g-sVo" of fi'i iuch (10 microns) in diam- eter, containing no cell- wall, and often having the power of spontaneous or ameboid motion from place to place. THE BLOOD. 77 ~ There are many varieties of colorless corpuscles occiirriiig normally in the blood. The five principal types are : Small lymphocytes. Eosinophiles. Large lymphocytes. Basophiles. Polymorphonuclear neutrophiles. The small lymphocytes form about 20^ of all the white cells. They are the smallest of the white cells, measuring only from •j-gVo ^"^ ^TW^ ^^ ^^ inch (5—10 microns) in diameter. The nucleus is usually round and surrounded by a relatively small spheric cell-body of dear cytoplasm. Large lymphocytes constitute about 7 fo of the white blood-cells. They are much larger than the last-named variety, about ywwo ^^ ^'^ ™^^ (^^ microns) in diameter, and resemble the small lymphocytes, with the exception that the cell-body is proportionately a trifle greater. Polymorphonuclear neutrophiles are the most numerous types of white blood-cells, forming about 70 fo of the total number. They are about the size of the large lymphocytes. The nucleus is very irregularly lobated in outline, often appearing to be multiple, but usually these seemingly separate lobes are connected by delicate threads of nuclear substance. The cell-body is peculiar, in that it contains many very fine granules scattered through it, which will stain only in a mixture of acid and basic dyes. These cells, as well as the next two varieties, j)ossess the power of ameboid movement. This ameboid motion is so called from its resemblance to the action of a unicellular ani- mal — the ameba. The cell so moving first advances a small projection of cytoplasm, called a pseudopod, into which the rest of the cell slowly flows. By virtue of this power of movement the white cells frequently leave 78 THE VASCULAR STSTEil. the blood-vessels and wander short distances in the surrounding tissues. The " migratory " cells of white fibrous tissue are examples of this. The irregular shape of the nuclei in the amehoid cells is probably due to the twisting and bending they are subjected to through the movement of the cells. Those of the white blood-cells which have ameboid motion also have the peculiar property of engulfing and carrying away certain foreign particles with which they may come in contact, and cells may frequently be seen Fig. 32. — White blood-corpuscle passing out through capillary wall : a, White corpuscle early in process ; b, white corpuscle nearly through. with several small particles within their cell-bodies which they have taken up. "When one of these cells comes in contact with a foreign particle, it apparently adheres to the particle, and a depression forms in the cell at the point of contact. The depression deepens and the cell-body closes over the top, thus inclosing the particle. In diseased conditions cells frequently are found containing bacteria which they have en- gulfed ; and when so found, are called phagocytes. Eosinophiles constitute only about 3% of all the white cells ; they are colorless cells, and closely re- BLOOD PLATELETS. 79 semble the last-dosn-ibed variety, but differ ciiiefly in the tact that the granules contained in tlie cell-body are much coarser, fc\\'er in number, and will stain only in acid dyes, such as eosin. Basophiles, mast=cells, or mastzellen, are quite rare, constituting only about 0.25 ^ of all the white cells. They differ from the neutrophiles principally in the fact that their granules will be stained only in a basic dye. The white blood-cells are not so numerous as the red, occurring in the ratio of 1 of the former to between Fig. 33. — Various forms of leukocytes; a, Small lymphocyte; b, large lympho- cyte; c, polymorphonuclear neutrophile; tf, eosinophile. 400 and 600 of the latter. This would make between 8300 and 12,500 white cells in every cubic milli- meter (2^ of an inch) of blood. The exact number varies with the condition of the individual, the time of day, and the nutrition. Blood Platelets. Blood platelets, blood plaques, or third corpuscles, are small round or oval bodies, one-fourth the size of red blood-cells, which occur in large but varying num- bers in the blood. They are rather unstable structures, and require some care to see properly. The exact function of the blood platelet is at present unknown, although it is supposed by many to be related to the 80 THE VASCULAR SYSTEM. formation of fibrin. Tlie platelets appear transparent, colorless, and structureless when examined in fresh or unstained preparations, but when recent smears of blood are fixed and stained by one of the eosinate of methy- lene-blue solutions in methyl alcohol, the protoplasm of the platelet will be found to be granular and to contain two types of protoplasm, one basic, the other neutral or acid in its relation to the stain. In some of the plate- lets the basic substance will be found to form a charac- teristic central body which must be considered as a nucleus. O.Q0 Fig. 34. — Blood platelets: a, Red corpuscles; b, white corpii.scle; c, platelets showing nuclei ; d, platelet showing nuclear tubstance irregularly arranged. The dust corpuscles are small granules, much smaller than any of the preceding forms, of an albu- minous nature, and have been originally the granules of white blood-cells. The escape and dissemination of these granules from both eosinophiles and neutrophiles has been directly observed by Sangree and Leroy. Shadow corpuscles are occasionally met with in normal blood. They are apparently the remains of the limiting membrane of red blood-corpuscles from which the hemoglobin has escaped. At infrequent intervals red blood-corpuscles that are either very small (microcytes) or splieric in form may be encountered. CRYSTALS. 81 Crystals. Hemoglobin easily crystallizes out from dried prepa- rations of blood, and then appears as long rhombic prisms of a red color. Hematin is also met with in dried blood, and occa- sionally in abnormal conditions, as a dark brown or black pigment. Hematoidin occurs as yellowish crystals around areas of extravasation of blood, also in pathologic and chronic irritations. When treated with ferrocyanid of potassium and an acid they give a blue reaction. Probably the most important blood crystal is hemin, or Teichmann's crystals. They are produced when Fig. 35.— Teichmann's crystals of bemin. X 1000 diameters. blood, fresh or dried, is heated in the presence of acetic acid and salt. They are narrow rhombic plates, of a dark brown color, and extremely small. The presence of hemin crystals in a material treated as just described is a positive test for blood, but will not give any light as to what animal it came from. Development of Blood-corpuscles. The first red blood-corpuscles are derived directly from the mesoblastic cells, and are nucleated and color- less. These multiply somewhat, and eventually become smaller, lose their nuclei, and acquire hemoglobin. 82 THE VASCULAR SYSTEM. Later in fetal life the liver and spleen contribute cer- tain of the colored blood-cells. After birth, however, the supply is maintained by the direct division of the erythroblasts or hematoblasts of the red bone-marrow. The colorless corpuscles originate principally in the lymphoid tissues and spleen. These lymphoid corpuscles become dislodged, and are carried along either in the lymphatic stream or, in the case of the spleen, in the blood current, and there become the small lymphocytes of the blood. The probability is that there they undergo further develop- ment into the neutrophile (the adult cell), and later into the eosinophile (sometimes called an overripe cell). QUESTIONS FOE CHAPTER VI. 96. From what layer of the embryo is the vascular system derived ? 97. Name the three coats of an artery. 98. Describe the inner coat; the middle coat; the external coat. 99. How do veins differ from arteries ? 100. Give the structure of the capillaries. 101. How are blood-vessels nourished ? 102. What structures compose the heart ? Describe each. 103. "What are the valves of the heart and veins, and describe them? 104. Of what is the blood composed ? 105. Give the size and shape of the colored corpuscles. 106. Give the number occurring in normal blood, and describe the structure of the colored blood-cell. 107. What action has water upon the colored blood-cell ? dilute saline solutions ? acids ? tannic acid ? 108. Describe the colored corpuscles of birds and cold-blooded animals, and name the differences between these and warm-blooded animals. 109. Give the general characteristics of the colored corpuscles. 110. Name the varieties of colorless corpuscles and give the per- centage of each occurring in normal blood. QUESTIONS. 83 111. Describe the small lymphocytes ; large lymphocytes; poly- morphonuclear neutrophiles; eosinophiles; and basophilea. 112. AMiat is meant by phagocytosis? 113. Describe the blood plates. 114. What are dust corpuscles ? 115. "Wbat are shadow corpuscles ? microcytes? 116. What crystals may be obtained from blood? 117. What are Teichmann's crystals, and how are they pro- duced ? 118. From what are the red blood-cells developed ? the colorless cells? CHAPTER VII. THE LYMPHATIC SYSTEM. The lymphatic system comprises the lymph-vesseh, the lymph, the lymph-nodules, the spleen, the thymus, the tonsUs, and the serous membrane of cavities. The lymph-vessels form a richly branching and anastomosing system of tubules, which vary in size from 1 mm. (-^Ig- of an inch) to the minutest capillaries. The smaller vessels continually join to form larger ones, until the thoracic duct is reached, which is of considerable size and empties directly into the subcla- vian vein, so that the cavities of the lymphatics are continuous with those of the vascular system. In structure the lymphatics are similar to the blood-ves- sels, the larger ones possessing three coats, the lymph capillaries possessing only one coat of endothelial cells. Frequently throughout the course of the lymph-ves- sels folds of the endothelial coat occur, which may be reinforced by a layer of fibrous tissue, and constitute the valves. These valves prevent the blood at the thoracic duct from being forced into the lymphatics, and at the same time compel the lymph to flow in one direction only. The smaller lymph-vessels have irregular dilatations throughout their extent, which in a measure serve a similar purpose. The lymphatics are almost universally distributed throughout the body, possibly to a greater extent in fibrous and areolar tissue. Around the nerves and smaller blood-vessels they sometimes form an inclosing LYMPH-FOLLICLES. 85 tube, in which case they are called perineuria! and perivascular lymphatics respectively. LYMPH. The lymph is a clear, wliitish fluid, which contains many freely floating cells and fatty granules. The cells resemble the colorless corpuscles of the blood, the small lymphocytes, however, being very greatly in excess of the other types. The fatty gran- ules are constantly present in varying amounts, but are very much increased during and just following digestion. DIFFUSE ADENOID TISSUE. In many areas throughout the body, especially in the tunica propria of raucous membranes, as in the lungs and digestive tract, masses of adenoid tissue occur. This adenoid tissue is formed of a network of fibrous tissue and branching connective-tissue cells (i-etiforiii tissue), which entangle and support large numbers of cells resembling the small lymphocytes of the blood, and called in this location lymphoid cells. In some places adenoid tissue occurs in small amounts, which merge gradually into the surrounding tissue without any sharp line of demarcation. The diffuse adenoid tissue and lymph-follicles commu- nicate with the lymphatic vessels by small lymph spaces within the follicle or narrow sinuses surrounding it, and also drain the overlying epithelium by delicate channels. LYMPH-FOLLICLES. In other localities the adenoid tissue may be sur- rounded by an envelope of fibrous tissue, in which a few fibers of smooth muscle may be interspersed, called the capsule. 80 THE LYMPHATIC SYSTEM. LYMPH-GLANDS. Lymph-glands or lymph-nodes are aggregations of lymph-follicles occurring in the course of lymph- vessels. The glands are usually bean-shaped. The lymph-vessels and blood-vessels enter at the central Fig. 36. — Adenoid tissue: A, a, Sliowing cells held together bj- retiform tis.sue; 6, showing retiform tissue cells having been washed out. £, Single lymphoid cell. depression, or hilum, from which point they are distrib- uted throughout the structure. The capsule is usually well marked, and sends pro- longations into the substance of the gland, which have received the name of trabeculae, and which in turn divide and subdivide until they eventually become con- tinuous with the retiform tissue forming the framework of the gland. LYMPH-GLANDS. S7 An outer or cortical aud an inner or medullnry portion may be readily distinguislied. The cortical portion is ('(trnposed of a number of dense lymph-follicles, placed side by side and separated from the capsule by a narrow cleft, the circumferevtidl lymph-sinus, which, however, is frequently bridged by small branching processes of connective-tissue cells. Fig. 37. — Lymph-node: a, Capsule; 6, circumferential lyraph-sin^l^^ ; c, lymjiii- follicles; a, lynapli-cord.s. The medullary portion is more open in appearance, and combines alternate bands of adenoid tissue, the so-called lymph=cords, and open spaces, the lymph=sinuses, which serve to transmit the lymph. These sinuses are frequently traversed by fine fibers of connective tissue. The blood-vessels, after entering at the hiluni, break up into a rich capillary network, which is principally 88 THE LYMPHATIC SYSTEM. distributed to tlie adenoid tissue, and reunite to form the veins wliicli leave tlie gland at the hiluni alsn. Occasionally, some small blood-vessels may enter at vari(nis points on the capsule. A few nerves may be found, both of the medul kited and the nonmedullated varieties. Fig. 38. — Spleen: a, Capsule; i, two trabeculfe extending perpendicularly into substance of organ ; c, small transverse baud uniting trabeculse and contain- ing a small blood-vessel ; d, splenic pulp. SPLEEN. The spleen is a lymphoid organ, and differs from a lymphatic gland principally in the arrangement of its blood supply and in having no medullary portion. SPLEEN. 89 It is surrounded by a deuse capsule of fibromuscidar tissue, which sends trdheculce down at rio;ht angles into the substance of the organ. These trabecule divide repeatedly to form the framework of the splenic pulp. This framework is filled with lymphoid cells. Fig, 39. — Spleen, Seclion taken some distance from surface, a, Trabecule in cross and oblique section ; b, .splenic pulp; c, Mal|iigliiaii body. At occasional intervals areas occur in which the lymphoid cells are very much more closely packed than usual. These areas are called the Malpighian bodies, and give the organ a characteristic appearance. The blood-vessels enter at the hilum of the organ, and 90 THE LYMPHATIC SYSTEM. proceed for some distance in the trabecules. From these, small branches proceed into the adenoid tissue, and frequently may be seen in the centers of the Mal- pighian corpuscles. Here they divide into very small arterioles, some of which open directly into rather large blood spaces in the splenic pulp, from which they may pass directly into veins without the intervention of true capillaries. b Fig. 40. — Thymus: a, Ciipsiile; 6, lyniplioid tissue; c, corpuscle of Hassall; dy capillaries. Small numbers of lymphatic vessels occur, mostly within the connective tissue of the capsule and tra- becule, and surrounding the blood-vessels. A few iierve-fibers are found, which are principally nonmedullated, and are distributed usually to the blood-vessels. THYMUS. In early life (up to the first year) the thymus is mostly epithelial in type, but as time goes on this is largely replaced by lymphoid tissue. The epithelium persists only as scattered, small, concentric masses (Hassall's corpuscles), containing a dozen or so flat- tened epithelial cells. TONSILS. 91 The gland is surrounded by a capsule of fibrous tissue, which sends down branching trabeculse, dividing the lymphoid tissue incompletely into follicles. At the periphery of the follicles the lymphoid tissue is more densely packed with cells than at the center. This has led to a division of the follicles into a cortical (outer) and a medullary (inner) portion. Blood-vessels and nerves are found in the trabeculse, and send fine branches into the lymphoid tissue. TONSILS, The tonsils are two in number, situated one on each side of the base of the tongue. They are composed of several lymphoid follicles surrounded on their outer surface by a capsule of fibrous tissue and on their free inner surface by the stratified epithelium of the buccal mucous membrane. At a number of places on the free surface of the tonsils the epithelium dips down into the lymphoid tis- sue, forming narrow fissures — the crypts. At these places the epithelium becomes infiltrated with lymphoid cells, until at the bottom of the crypts it fades away into the lymphoid tissue. Blood-vessels, lymphatics, and a few nerves supply the tonsil and enter the organ through the capsule. SEROUS CAVITIES AND MEMBRANES. The serous membranes may be considered as the greatly expanded walls of lymph-vessels, and the serous cavities inclosed as greatly dilated lymph- spaces. In structure the serous membranes are com- posed of a single layer of thin, irregular, polygonal 92 THE LYMPHATIC SYSTEM. cells, placed edge to edge and united by cement sub- stance, wliicli rest upon a rather thin sheet of fibrous tissue. At irregular intervals small openings occur (the stomata), wliich ai-e the mouths of lymphatics. Occasionally, a place is found at which the endothelial cells do not " match up " well. These spaces thus '' ^^"it' .lIS^I^^ *^(j ^0 ... Fig. 41. — Tonsil: u, Epithelial surface; 6, crypt; c, adenoid tissue; d, lymph- follicle. formed are filled up by cement substance, and are called the pseudostomata. The principal serous membranes of the body are the pleura, pericardium, and peritoneum, and the synovial membranes of the tendons and joints and meninges. Structurally, the internal lining of heart, blood-ves- sels, and lymphatics would also come under this head. MUCOUS MEMBRANES. 9.3 MUCOUS MEMBRANES. All cavities and passages in connection with the external air are lined with mucous membranes. These consist of two essential parts — an cpitlivlial corering and a nuLcpithelial fibrous coat. The epitheliiiin may be either stratified or columnar, according to its location. Immediately under the ej>i- thelium the fibrou.s coat is usually specialized into a clear thin layer, called the " basement membrane." Beneath the basement membrane, within the subepithe- Fig. 42. — Types of glands : a, Simple tubular ; b, compound tubular ; c, coiled tubular; d, simple saccular ; e, compouud saccular, or racemose. lial fibrous tissue, in some localities a thin layer of smooth muscle — the muscularis mucosae — occurs. Along the course of the mucous membrane numerous glands occur. These are devices whereby a large secreting surface may be made to open upon a compara- tively small area, and consist virtually of more or less complex invaginations of the epithelium. Several types "jf glands are recognized : I. Simple tubular glands are straight, narrow de- pressions into the subepithelial tissue, which are walled 04 THE LYMPHATIC SYSTEM. by specialized epithelium continuous with that of the free surface. Examples of this type are found in the cardiac end of the stomach and in the crypts of Lieber- kiihn of the small intestine. 2. Compound tubular glands are similar in struc- ture to the simple tubular, but branch. In some instances these branches divide and subdivide, produc- ing an arborization of tubules all discharging their secretions eventually into the common duct. The glands of the jiyloric end of the stomach and the mam- mary gland may be taken as examples. 3. Coiled tubular glands differ from the simple tubular only in the fact that they run a tortuous, usually spiral course. The sweat-glands are examples of this type. 4. Simple saccular glands are small, spheric cavi- ties lined with secreting cells and having a small open- ing at their outer poles through which the secretion may be discharged upon the free surface. This type of gland may be said not to exist in the human body, but it occurs frequently in tlie lower forms of life, although some writers class the follicles of the ovary under this head. 5. Compound saccular, alveolar, or racemose glands resemble the compound tubular gland in ar- rangement, but the terminal secreting portion of the tubules dilates into saccules. The larger sebaceous glands and the lungs are constructed after this type. QUESTIONS FOE CHAPTER VII. 119. What structures and organs are comprised in the lymphatic system ? 120. Describe the lymph-vessels. 121. What are perineurium and perivascular lymphatics? 122. Name and describe the cells occurring in the lymph. QUESTIONS. 05 123. Describe diffuse adenoid tissue. 124. Wliat are the lymph-follicles ? 125. What are the lymph-nodes ? 126. Describe the structure of a lymph-node. 127. To what system does the spleen belong ? 128. Describe its capsule and trabeoulse. 199. Describe the Malpighian bodies of the spleen. 130. Describe blood and nerve supply. 131. Describe the thymus. What are Hassall's corpuscles? 132. "ttTiat are the tonsils ? Describe their structure. 133. A\Tiat are serous membranes ? 134. Where do thej' occur and what is their structure ? 13.5. What are mucous membranes, and where do they occur? Describe their structure. 136. Name the types of glands and describe each. CHAPTER VIII. THE DIGESTIVE TRACT. The mouth is lined with mucous membrane, com- posed of stratified epithelium, upon the surface of which open the excretory ducts of numerous branched tubular glands. At the junction of the epithelium and the submucous tissue an irregular outline is presented, the projections of submucous fibrous tissue being called papillae. The tongue consists of a mass of voluntary muscle- fibers, running in various directions, surrounded by a layer of areolar tissue (the submucosa), and covered with stratified epithelium (the mucosa). The muscular portion is made up of the geniohyo- glossus, lingualis, and styloglossus muscles, and pre- sents fibers running longitudinally, transversely, and vertically. The submucous coat at its outer surface is thrown into marked papillse, which are covered closely by epithelium. Three types of papillse are recognized : 1. Filiform papillae, by far the most numerous, are narrow, conoid projections, which may have at their outer surface a number of smaller projections, called secondary papillse. 2. Fungiform papillee, not quite so numerous as the former, are larger, their bases are somewhat con- THE TONGUE. 97 stricted by the epithelium, and they contain secondary papillae on their sides as well as at the outer surface. 3. The circum vallate papillas are the largest and broadest of the three types. They occur in smaller Jiumbers, and are usually found at the posterior por- tion of the tongue. They contain secondary papillse at the top. At the sides, the epithelium dips down to form furrows or crypts, which make the papillse appear to stand out from the surrounding tissue. Embedded in the epithelium at the sides of the cir- cumvallate papillse are the taste-buds. Fig. 43. — Tongue: a, Filiform papilla; 6, filiform papilla with secondary papillse; c, fungiform papilla; (/, circumvallate papilla; e, taste-bud. The taste=buds are the seat of the sense of taste, and consist of several long, spindle-shaped, neuro-epi- thelial cells (the gustatory cells), with elongated nuclei, which are surrounded by a layer of slightly flattened cells (the cortical or tegment cells), the whole forming small flask-shaped bodies, which are usually grouped side by side, vertical to the epithelial surface. Besides the foregoing structures, the tongue contains a vertical partition, mostly of fibrous tissue (the septum lingualce), which divides it into laterally symmetric 98 THE DIGESTIVE TRACT. halves, Numerous raucous and serous glands also occur in the submucous tissue. The tongue is richly supjilied with lympliatica, the larger vessels being situated deeply, the superficial ones forming a plexus under the mucosa and sending small branches up into the papillffi. Niuuerous lymph-folli- cles and areas of diffuse adenoid tissue occur in con- nection with the lymphatics, being especially numerous at the root of the tongue. Fig. 44. — Ground section ttirough dentin, cutting tlie dentinal tubules at ricbt angles to their course, and showing the column uicating branches connecting them. Fig. 45. — Transverse ground sec- tion of tooth at the junctioQ of the enam.el and dentin (diagrammatic); a, Enamel cuticle; 6, enamel; c, inter- globular spaces; d, dentin, showing dentinal tubules. The blood supply is very abundant, plexuses of small arterioles occurring throughout the submucosa and sending branches into the papillae and around the numerous glands. The mucous membrane is richly supplied with nerv&s, both sensory and taste. They are mostly med- ullated fibers from the glossopharyngeal aud lingual nerves. Numerous ganglia also occur along the course of the former. Tt[E TEETH. 09 THE TEETH. Although the teeth vary considerably in shape and in general appearance, the same general structure is found in all. Tiie outer or exposed part of the tooth is called the Town ; the portion embedded in the socket is called Fig. 46. — Tooth: a, Enamel; h, dentin; c, pulp-cavity ; tl, junction of enamel and cementum ; e, cementum ; /, alveolar periosteum. the fang. Between these, at about the edge of the gum, is a slightly constricted portion — the neck. The main bulk of the tooth is composed of the dentin, or ivory. This gives the form to the tooth, and incloses the pulp=cavity, which contains the pulp. At the crown the dentin is covered by the enamel. At the fang it is covered by the cementum, except at 100 THE DIGESTIVE TRACT. the apex, where a minute canal penetrates to the pulp- cavity. The dell tin is composed of a hard, white, apparently homogeneous matrix, in which are numerous small (25 microns = -Yst^ of an inch) canals — the dentinal tubules. These dentinal tubules originate in the pulp- cavity, and run a wavy course, more or less at right angles to the inner surface, through the dentin, and terminate at the juncture of the dentin and the enamel or cementum in irregular dilatations, called the inter- globular spaces. Along their course many communi- cating branches occur, uniting the dentinal tubules. Fig. 47, -Enamel : a, Section parallel to .surface, showing cross-sections of enamel prisms; b, longitudinal view of enamel prisms. That portion of the matrix which forms the wall of tlie tubules being harder and denser than the main body, it has received the special name of dentinal sheath. The enamel consists of closely arranged columns (the enamel prisms), running vertically to the free surface of the tooth, and held together by a very small amount of resistant, clear, cement substance. When isolated, these prisms are foimd to be four- to six-sided, and have a slightly irregular outline. At the dentinal border of the enamel there occasion- ally occur between the enamel prisms small canals which open into the interglobular spaces. At birth the enamel is covered by a thin meinbrane, THE TEETH. 101 tlie enamel cuticle, derived from the epithelial cells of the ennmel orfjan ; this, however, soon wears off. The cementum consists of eoncentric layers of osseons tissue containing many lacunie, with their radi- Fig. 48. — Dentin at tn]ge of [)uli>-caviLy, showing open ends of dentinal tubules tbrougli wbich extend prolongations of the odontoblasts — the dentinal tihefs. Photograph made from a ground seeLioii ol tooth. ating canaliculi, which contain bone-corpuscles and communicate with the interglobular spaces. Ha\'ersian canals are absent, excepting occasionally in the thicltest portions. The cementum is surrounded by a dense layer of 102 THE DIGESTIVE TRACT. connective tissue (the periodontal membrane), which is virtually a periosteum. The tooth-pulp is a mass of undeveloped connec- tive tissue, consisting mostly of stellate or irregular Fig. 49. — Junction of dentin and enamel : a, Dentin, showing dentinal tu- bules and (&) interglobular spaces ; c, enamel. Photograph from ground section of tooth. connective-tissue cells, with nerves and blood-vessels, which fill the pulp-cavit)-. The portion of the pulp in contact with the den- tin is made up of elongated cells (the odontoblasts), which send long processes into the dentinal tubules. THE TEETH. 103 These processes usually extend the whole length of the tubule, and are called the dentinal fibers. The Development of Teeth. Both the epiblast and mesublast contribute to the formation of the teeth. Fig. 50. — Developing tooth ; a, .StriitiDed epithelium of buceal cavity, send- ing down (b) coi-d of cells — tlie dentinal ridge ; c, gi'eatly expanded mass of epi- thelial cells rorniing the enamel organ; d, small offshoot of epithelium, winch hirer will develop into the enamel orgau of the permanent tooth ; e, papillus. The epithelium over the primitive jaw becomes thickened, and grow.s down into the subjacent tissue to form the dental ridge. From the lower outer border 104 THE DIGESTIVE TRACT. of this, flask-shaped masses of cells (dental bulbs) grow (one for each milk-tooth), which subsequently bec()me liollow on their under surface and cover a co- noid upgrowtli of connective-tissue cells (the papilke). Fig. 51. —Developing tooth, more liighly magnified; a, Outer portion of enamel organ ; b, inner layer of columnar cells of enamel organ, which are just beginning to secrete; e, enamel; d, portion of papilhis, the outer layer of which is composed of odontoblasts which are just beginning tn secrete; e, dentin in contact with the enamel. The dental bulbs continue to expand, their inner sur- faces assuming the form of tlie crown of the tooth, and the inner layer of cells becoming columnar. Each of these columnar cells secretes an enamel THE ESOPHAGUS. 105 prism, and the bulb is now called the enamel organ. While this has been in progress, the outer cells of the papillae have elongated to form the odontoblasts, which deposit the dentin. Thus it will l)e seen that the enamel is deposited outward, the dentin inward. The remains of the papillae become the tooth-pulp. The permanent teeth are developed similarly from secondary dental bulbs springing diagonally downward from the neck of the milk-tooth bulbs. The cementum is deposited later by the alveolar periosteum, and is somewhat laminated as a result, re- calling in mode of development the external circumfer- ential lamellae of the long bones. THE ESOPHAGUS. The esophagus has four layers — mucous, submu- cous, muscular, and fibrous. The mucous coat consists of stratified epithelium resting upon a basement membrane which is thrown up into papillae. At the outer edge of the basement mem- brane is found a very narrow layer of smooth muscle — the muscularis mucosae. The submucous coat is of loose fibrous tissue, and contains numerous blood-vessels, lymphatics, and nerves, besides scattered mucous glands, which dis- charge into the lumen of the esophagus. The muscular coat consists of two layers — an inner (circular) and an outer (longitudinal) — throughout its length, the upper third being composed of voluntary muscle-fibers, which are gradually replaced below this point by smooth muscle. The fibrous coat is a thin layer of rather dense, white, fibrous tissue, which may also contain a few fibers of yello\\' elastic tissue. 106 THE DIGESTIVE TEACT. THE STOMACH. The stomach presents two portions for considera- tion : viz., the cardiac or upper and the pyloric or lower ends. The cardiac end of the stomach comprises four coats — mucous, submucous, muscular, and serous. Fig. 52.— Oariliac end of etoniaeh : a, Mucous coat; 6, submucous coat; c, d, d', eivoutar. longittidinal, and oblique tnuscular coats ; p, serous coat ;/ raus- cularis inucosse; g, chief cells ; h, acid cells; i, opening of gastiic gland' on free surface of stomach. The mucous coat is continuous with that of the esoph- agus, and, like the latter, has a basement membrane and muscularis mucosae. The epithelium, however, is thickly studded with simple tubular glands, opening u])on the free surface. In tliese glands two types of cells are found — chi(f or peptic, and parietal or acid. The chief cells, which are more numerous and smaller, were supposed to be the pepsin-secreting elements. THE STOMACH. 107 The parietal cells arc relatively lar!i;<', and have well- iiuivked, lart^e cell hixlies, whieli stain deeply in almost all anilin stains. They were snppiised to he the hydro- el dorie-aeitl-seeretin^- element. The suhtimi'ons coat consists of loose fihvons tissnc containing many blood-vessels, lyniphaties, and nerves. ( )eeasionally, small areas of diif'use adenoid tissne may oei-nr. This coat is fre(|uently thrown into riducr earrvinff the mncoiis coat above it and forming the rno'fe. Fig. 53. — Mucous coat of pjioric euil of Lhe stomach : ii, Branched tubular gland j />, submucous coat. The mnsrular coat consists of three layers of smooth muscular fibers — an inner circuhir, a middle hiif/ltucU- nal, and an outer hicoinplefr oblique layer. The serous coat is a reflection of the peritoneum, and is made up of a delicate sheet of fibrous and yellow elastic tissue, covered on the outer side bv a single layer of endothelial cells. The pyloric end of the stomach differs from the cardiac end chiefly in the muct)ns and muscular coats. The glands studding the mucous coat (pyloric glands) are slightly further apart than in the cardiac end. They 108 THE DIGESTIVE TRACT. are further characterized by branching at their lower ends, to terminate in t\\(j or three tortuous offshoots. Only one type of cell is present in these glands, the parietal or acid cells being cdufined entirely to the car- diac portion. The outer or oblique muscular layer is usually en- tirely absent also. Tlie masses of adenoid tissue in the submucosse (solitary follicles) are usually a trifle more numerous here than in- the cardiac jiortion. THE INTESTINES, The intestines contain four coats throughout their entire length : viz., mucous, submucous, muscular, and serous. The mucous coat is frequently thrown into transverse ridges, which are called the ralcuke conni- ventes. Structurally, we may recognize the duode,nuii\, small intedine, larc/e intestine, and (ippoidix. The small intestine has projecting from its mucosa small, finger-like projections, called the villi, which are often club-shaped. These villi are covered with a single layer of columnar epithelial cells, which often exhibit the goblet form. Dipping down into the sub- mucous coat from between the villi are simple tubular glands, the crypts of Lieberkiihn, which secrete the succus entericus. Directly imder the epitlieiiimi is a flat layer of con- nective-tissue cells, called tlic endothelium of Debove, which in turn rests upon a nierabrana propria of fibrohs tissue. At the iimer border of this is the muscularis mucosse, which extends throughout the intestine. M^ithin the villi is found a small lymphatic radical (the lacteal) surrounded by a network ersed with fibers of yellow elastic and smooth muscular tissue and supported by some loose areolar tissue. The lymphatics of the liver accompany the blood- THE SALIVAEY GLANDS. 117 vessels as perivascular spaces, the supeijioial lymphatics occurring around the vessels of the capsule. The deeji plexus surrounds the interlobular vessels, and possibly the intralobular capillaries. The nerves of the liver are both medullated and non- medullated. They follow the course of the hepatic artery in the capsule of Glisson. Small ganglia occa- sionally occur near the edge of the lobule, but the exact termination of the fibers is not known. The gall-bladder consists of three coats. The mucous or internal coat is composed of columnar epi- thelium continuous with that of the hepatic duct. Ex- ternal to this is the middle or fibrous coat, which, besides white fibrous tissue, contains numbers of longitudinal and transverse smooth muscle-fibers. The outer or serous coat is derived from the peri- toneum. The inner surface is thrown into small ridges, called rugae, and is usually covered by a viscid secretion from the mucous lining. THE SALIVARY GLANDS. The salivary glands are the parotid, the submaxil- lary, and the sublingual glands, and the pancreas. They all belong to either the compound tubular or the racemose type of gland, and ai'e surrounded by a cap- sule of fibrous tissue, which sends septa down into the glands, dividing it into lobes. The lobes are further subdivided by smaller septa of fibrous tissue into lobules. The main duct of the gland enters at the hilum and divides into numerous branches, one of which is distributed to each lobe (the interlobar dtid). These further divide, sending a branch (the interlobular ducts) to each lobule, where they again divide into the intra- 118 THE DIGESTIVE TRACT. lobular duds, or salivary tubes of Pfluger, which in turn continue for a way as the intermediate tubes, and termi- nate in the secreting portion of the gland, the acini, or alveoli. All the ducts are lined with a layer of columnar epi- thelium, which rests on a basement membrane. In some of the main ducts a second layer of low cells is found between the columnar cells and the basement membrane. External to the basement membrane is a fibrous coat, which may contain some fibers of yellow elastic tissue and, in the larger ducts, smooth nmscle- fibers. The acini vary in different glands from saccular to club-shaped or tubular. They are lined by a single layer of epithelial cells, broader and larger than those lining the ducts, which rest upon a membrana propria, or basement membrane. According to the character of the secretion and the general structure of the aoiyii, the salivary glands are divided into the serous, mucous, and mixed glands. The serous glands secrete a thin, watery, albumi- nous saliva. The alveoli are usually small and of the tubular variety. The cells are opaque and markedly granular, and rest upon a relatively small basement membrane. The nuclei are usually round, and are placed about one-third the width of the cell from the basement membrane. In the true serous glands the " demilunes " are absent. The mucous glands secrete a thick, viscid fluid (mucus). The alveoli are usually larger than those in the serous glands, and are saccular or flask-shaped. The cells are larger, transparent, but slightly granular, have a well-developed basement membrane, and stain but slightly. The nuclei are usually flattened, and are placed close to the basement membrane. THE SALIVARY GLANDS. 119 In many alveoli we find, besides the large clear cells just described, thin, granular cells, or groups of cells, cresceutic in form, and situated at the periphery of tlm acini, against the basement membrane. These usually have a spheric nucleus, and are known as the demHnru.i of Heidenhuin, or the erescenfs of Gianazzi. The mixed glands, or seromucous glands, may have some acini of the serous type and some of the Fig. 61. — Serous and inucons salivary j^laiids: A, Mucous salivary gland ; B, serous salivary gland; a, demilune of Heidenhain. mucous, or some acini may contain cells of both kinds. It has been claimed that the demilunes could be con- sidered as representing occasional serous cells situated peripherally in a mucous gland. The blood supply of the glands is very abundant, the arteries accompanying the excretory ducts to a point near the acini, where they branch into a network of capillaries, which closely surround the basement mem- 120 THE DIGESTIVE TRACT. braiio of the acini, and reunite to foi-m the veins, wliieh return parallel to the arteries. The larger lymphatic vmseU arc found with the arte- ries in the interlobular connective tissue. These send along the course of the ducts Ijrnnches which terminate in numerous irregular clefts or spaces around and be- tween the acini. Nt'vrex are plentiful, and consist of medullated and nonmednllated fibers, with numerous small ganglia. The ultimate distribution of the nerve filaments is unknown, having been traced positively only as far as the basement membrane of the alveoli. The Parotid Gland. The parotid gland is a typical serous gland, and pos- sesses the characteristics previously described under that head. The excretory duct (Stenson's duct) is large, has thick walls of fibro-elastic tissue, and is lined by a double layer of epithelium. Its smaller branches are lined with a single layer of columnar colls, which pre- sent a distinctly striated appearance at their free edges, and are hence called rod epithelium. Between the intralobular ducts and the acini inter- mediate or intercalated tubules occur. These are small tubules lined with flattened cells. The Pancreas. The pancreas is a gland of the serous tyjie, and re- sembles the parotid gland so closely as to \\i\\e been called " the abdominal salivary gland." It differs, however, from the parotid in the following features : The pancreatic duct (or main duct of the gland) branches directly to form the inkniwdude iubu/cs with- out the intervention of the intralobular duets, or sali- THE SUBLINGUAL fiLAND. 121 vary tnltcs of Pfliiger, which in the p:ir(.)tid are lined with rod epithelium and are quite prominent. The (ii'iii! arc longer and narrower, as a rule, than those of the parotid. The xccretiuy cellx are more columnar, narrower, and their nuclei are usually slightly farther from the per- ipheral edges of the cells. The cells also contain distinct, highly refracting granules (the zymogen granules), situated mostly at the margin of the cell-body next to the lumen. The number of granules and the extent of the granular zone in the cell depend upon the state of activity of the gland, being least in evidence just as digestion begins. Tiie development of the pancreas is not homogeneous, but throughout the organ are found certain small, denser areas, well supplied with blood-vessels, which are undeveloped lobules or acini. These areas possess vaguely the type of the rest of the organ, and have received the special name " bodies of Langerhans." The Sublingual Gland. The sublingual gland in man affords a typical exam- ple of a mucous gland, having all the characteristics previously described under that head. Its main duct, the ductus sublingualis, or duct of Bartholin, is lined with a double layer of columnar epi- thelium, which rests upon the usual membrana propria of fibro-elastic tissue. This duct branches to form the intralobular or mucous tubes, which pass directly into the acini, there being no "intermediate" tubules in this gland. The fibrous tissue between the acini is quite scanty, and usually contains many wandering connective-tissue cells. 122 THE DIGESTIVE TRACT. The Submaxillary Gland. In man tlie submaxillavv gland is of the raucoserons or mixed type. Tlie main duct, or dncf of Whurtoti, divides in the usual manner until the intermediate tubules are reached, some of which terminate in the acini of tlie serous type ; others, in the acini of the clear mucous type. QUESTIONS FOR CHAPTER VIII. 137. Describe the mucous uiembrane of the mouth. 13-<. Of what tissue is the tongue composed ? 139. Name the tj'pes of papillae in the tongue. 140. What are the taste-buds V Describe them. 141. What is the lymphatic supply of the tongue? the blood supply V the nerve supply ? 142. Describe the gross structure of the tooth. 143. What is dentin ? Describe it. ^Miat is the enamel ? the cementnm ? the tooth-pulp ? 144. What layers of the embryo contribute to the development of the teeth? 145. What is the dental ridge? 146. What are the odontoblasts? 147. Describe the process of tooth development. 148. Name the four layers of the esophagus. Describe each. 149. What two portions of the stomach are considered histolog- ically ? 1.50. Name the four layers of the stomach. l.)l . Describe the mucous coat of the cardiac end of the stomach; the submucous coat; the muscular coat ; the serous coat. Irr2. How does the pyloric differ from the cardiac end of the stomach ? 153. Name the four coats of the intestine. 154. What portions of the intestine do we recognize structurally ? 155. What are the villi ? 15(). What are the valvulte conniventes? 157. Describe the mucous membrane of the small intestine. 158. What is the endothelium of-Debove? QUESTKlNfl, 123 159. Wlmt are the lacteals ? 160. What are Peyer's patches? 161. Describe the submucous coat of the small intestine. 162. What are crypts of Lieberkiihn ? 163. De.scribe the muscular coat of tlie small intestine. 164. What are Brunner's glands, and where do tbry occur ? 165. How do the large intestines differ from the. small ? 166. Describe the structure of the appendix vermiformis. 167. Describe the blood supply of the stomach and the intes- tines; the nerve supply; the lymphatics. 168. Into what is the liver divided '! 169. What is the capsule of Glisson, and of what is it composed ? 170. Of what are the lobules compo.sed ? 171. Describe fully the blood supply to the liver. 172. Where do the bile caijillaries originate? Describe their course. 173. Describe the portal canal. 174. Describe the structure of a bile-duct. 175. Describe the lymph supply of the liver. 176. Describe the nerve supply of the liver. 177. Describe the structure of the gall-bladder. 178. Name the salivary glands. 179. Outline their general structure. 180. What is the main duct? What are the interlobar ducts? the salivary tubes of Pfluger? the intermediate tubes? the alveoli? 181. What is the structure of the ducts? 182. What is the characteristic of a serous gland ? of a mucous gland ? of a mixed gland ? 183. What are the demilunes ? 184. Describe the blood supply of the salivary glands; the lymphatic supply ; the nerve supply. 185. Describe the special characteristics of the parotid gland. 186. Describe the special characteristics of the pancreas. 187. . What are the bodies of Langerhans ? 188. What type of gland is the sublingual ? Describe it. 189. What type of gland is the submaxillary ? Describe it. CHAPTER IX. THE URINARY TRACT. The kidney is covered by a ca])sule of fibrous tissue, and upon longitudinal section is seen to be composed of t\V(.) distinct portions. The outer or codical portion is granular in apjjear- ance and comprises about one-third of the organ. The inner or medullary portion constitutes the remaining two-thirds of the organ, and is seen to be composed of a number (from ten to fifteen) of pyramidal masses (the pyramids of Malpighi), with their bases at the iuner surface of the cortex, and their apices pointing into the sinus, constituting the papillce. They are finely striated radially, owing to the alter- nate arrangement of th<> uriniferous tubules and blood- vessels which compose them. Usually small extensions of cortical substance, called the cortical columns, or columns of Bertini, jitroject down between the pyra- mids of Malpighi, separating them one from another. At intervals along the junction of the cortex with the Malpighian pyramids jirojections from the latter extend into the cortical sulistance. These are called the medullary rays, or pyramids of Ferrein, and consist of continuations of the striations composing the Malpig- hian jtyramids. That portion of tlie cortex situated between the ]iyramids of Ferrein has received the name of the labyrinth, on account of tlie tortuous course which its component tubules take (being composed 124 URINIFEROUS TUBULES. ] -25 chiefly of the first and second convokited tubules, a description of wliich follows). At the side of the kidney opposite the cort(!X there is a marked depression, called the hilum, at wliich point it flares out into a funnel-shaped tube (the pelvis) and expands into a central cavity, called the sinus. Fig. 62, — Kidiiev lon^itiidiniK ilioii e\hilntin., geiiei il rt-liitions of micio- scopicdetaiIs(;ifter"l ici )1} 4 leniliitei\ I inclci < one uT Miecitlyces, into whicli ii i)iii)illa projet rs 1 c i ti \ c()iitTiiiin_ lil)^ tmtli (/) mil iiiednlliiry i-ays (ni) ; 2, luedolhi ; 3/, iM ilpigiiian p> i iiuids, oiiK ot)liqtitl3 cut Hi 3, 3 : />, l)onii- dary layer ; J?, coluimis of Eertiiii ; 4, masses of adipot,e tissue; 5, 5, biaiieUes of renal artery (after Heule). The sinus has several branches or divisions, into which project the papillte (the infundibulae, or calyces). URINIFEROUS TUBULES. The histologic units of the kidney are the uriniferous tubules. These tubules begin as closed, spheric expan- 12G THE UEINAKY TEACT. sions (the glomeruli or Malpighian bodies) in the labyrinth of the cortex. At the end of the glomerulus a slight constriction occurs, called the neck. Next the tubule increases in size slightly and pursues a wavy course, entering the area of the medullary ray (the first or proximal convoluted tubule). Here it turns downward in a spiral course (the spiral tubule), until it reaches the lower border of the medullary ray, and enters one of the ]\Ialpighian pyramids. At this point the diameter becomes much smaller and the tubule descends in nearly a straight line as the de-vrndhif/ limb of Henlc's loop, ^\'hen well down in the Maljiighian pyramid, the tube expands somewhat, and then turns abruptly upward (the loop of Henle ) and ascends in a straight line, nearly parallel to the descending tubule, until it is well up into the medullary ray (the ((scciiding limb of the loop of Henle), when it expands still more, re- enters the labyrinth, and follows a very irregular course for a short distance (the iii'ccpihir or zigzag tubule"). The convolutions of the zigzag tubules become more regularly curved (the sevnnd or dixtnl conrohitvd tube), and the tubule again enters the medullary ray. Here it forms a slight arch (the (irrhed collecting or junctional tubule) and joins a large collecting tubule or the tubule of Bellini, which runs straight down to\rard the pelvis of the kidney, joining other similar collecting tubules to form princijjol tubulcx, several of which unite to form a papillarjf duct, which terminates at the end of one of the ^li^pillfe- A single papilla will contain about two hundred papillary ducts. X IMalpighian body is composed of a small afFereq^ arteriole, which immediately branches into a spheric tuft of capillaries, which reunite to form one or, rarely, more efferent arterioles, which emerge beside the affer- ent vessel. URINIFEROITS TUBULKS. 12; Fig. 63. — Diagram of kidney, showing Ihe course of uriiiifeious tubules and of tbe lilood-vessels {after Piersol) ; for convenience, the medulla is i-epreseuLed as greatly shortened. The various divisions of tbe tubule — Bowman's capsule, neck, proximal convoluted, spiral, descending and ascending limb of Henle's loop, irregular, distal convoluted, arched collecting, sfraight collecting, and excretory duct — are indicated by their initial letters: (/,, c, c, respectively tlie aflFerent, efferent, and capillary blood-vessels ; s, stellate vein ; vr, vasffi rectse. 128 THE URINARY TRACT. Closely surrounding this tuft and dipping down be- tween the capillaries is a thin layer of fibrous tissue called the capnule of Boioman, which serves as a base- ment membrane for a layer of flat cells, which are con- tinuous with the cells lining the uriniferous tubules. Fig. 64. — Cortical portion of Itidiiey: a, Medullary rays; b, labyriutb ; c, gloraei'iili. At the upper part of the Malpighian body, where the arteriole enters, the capsule of Bowman with its layer of cells bends sharply around upon itself, and descends, inclosing a very narrow space, which is the beginning of the lumen of the tubule. The tuft, therefore, lies URINTPEKOUS TUBULKS. rjn entirely on the outside of the tubule, aw thout:;!) it had been thrust into a hollow sphere, eaiisinj;; one side to be invaginated into the other. The iiriiiifcivun tuhulcn are surrounded by a basement membrane, eontinuous with the capsule of Bo\vnian, upon which, internally, rests a single layer of epitiielial cells, continuous with those lining the J\Ialpighiau body. Fig. fi5. — Kidney in section: a, Glomeiuliis ; 6, cross-section of convoluted tubule ; c, cross-section of Henle's tubule ; d, capsule of Bowman ; e, fibrous tissue between tubules. The size and character of these cells vary according to the part of the tubule in which they are found. The glomeridus is about 0.2 mm. (y^-g- of an inch) in diameter, the cells lining it being Kqiimnmis. At the neck the diameter diminishes to 25 mici'ons (y^^q-q of an inch), the epithelium being of a low cuboid form. The 130 THE UEINAEY TRACT. jJroximal and didal convoluted tubules are similar, being 50 microns (g^J^ of an inch) in diameter and lined with columnar cells. These cells are of moderate size, being about 12.5 microns (-j-oVt ^^ ^° inch) high. In favorable preparations they are seen to contain fine Fig. 66.— Section of Icidiiey: a, Gloiiienilus ; b, iiriuifefous tubules in transverse section ; Cy portion of couvoluLed tubule. striations at the outer border, and to be finely granular in that portion next to the lumen. The spiral tubule diminishes slightly in size to 40 microns (g-^j of an inch) ; the epithelium resembles that of the convoluted tubules, with perhaps a slightly plainer striation. The BLOOD SUPPLY. 131 epithelium at the (Icnenidinr/ liinh of ILnle's loop be- comes very much flattened, being only about 3 microns (~STW1T ^^ ^" inch) in tliickness, tlie total diameter of the tube at tliis place measuring about 10 microns (tsVo" '^^ ^" inch). In the loop and mcemUnr/ limb of Henle the cells increase in size to (J microns (4 a'oT "^ an inch), the total diameter of the tube being 25 microns (yoVo °^" ^^ inch). No definite size can be ascribed to the irregular titbule ; it varies, however, be- tween 35 and 60 microns (y-j-Q and ^i-j- of an inch). The cells resemble those of the spiral tubule, the nuclei being more oval and nearer the lumen. The tubes of Bellini have the general characteristics of the second convoluted tubule, being, however, slightly narrower (40 microns, or -g-l-g- of an inch). The princijial tubes and papillary duds vary in size up to 250 microns (ttt °^ ^^ inch). It will be seen that, with the exception of the glom- erulus, in a cross-section of a tubule the cell on either side and the lumen each occupy about one-third of the entire diameter. BLOOD SUPPL-^. The blood enters the kidney at the hilum through the renal artery, which passes just beneath the mucosa of the pelvis, sending branches (interpyramidal arteries) up between the Malpighian pyramids (in the columns of Bertini) and a few vei'y small branches to the adjacent tissues. The large branches proceed upward to the juncture of the medullary and cortical portions, where they turn nearly at right angles and form arches over the top of the Malpighian pyramids, called the arte= rial arcade. From the arterial arcade two series of smaller branches arise : one series, the interlobular arte- 132 THE URINARY TRACT. ries, running straight toward the periphery, following the outer border of the labyrinth ; the second series, the artrrm rocUr, running tfiward the pelvis, into the Mal- pighiau pyramids. The interlobular arteries give oif into the labyrinth Fig. 67.— Section of kidney, blood-vessels injected : a. Small interlobular artery, sending branches sisalFerent arterioles to (6) several glomernli; c, eiferent arteriole, emerging from glomerulus to form (d) capillary network ; e, capsule. numerous lateral branches, which enter the glomeruli as afferent (uieriolcK. These form a small plexus within the glomerulus and emerge as the efferent eirtenoles, break up into capillaries, and course around between the THE SINUSES, PELVIS, AND UEETEKS. 133 uriniferous tubules of the labyrinth and medullary ray, a few N'esriels reaching down into the Malpighian pyra- mids. The capillaries join to form small veins (the inter= lobular veins), which empty into the venonn arcitdes, and thence into the inter pyramhlal rciiii^ and into the renal vein, running parallel to the arteries of similar names. Just beneath the capsule some of the vessels form small, irregular sinuses, called the venae stellae. The arterise rectae form capillaries, which run be- tween and encircle the uriniferous tubules in the Mal- pighian pyramids, form a network around the openings of the capillary tubules, and return by the vence. recite (by the side of the arterise rectse) to empty into the venous arcade previously described. LYMPHATICS. The lymphatics of the kidney are not well defined. One system is found in the capsule, the other in the basement membrane and fibrous tissue between the tubules. NERVES. The nerves of the kidney are of the nonmeduUated variety. They enter at the hilum with the blood-ves-. sels, follow the course of the latter, and send small branches between and around the uriniferous tubules. But little is known of their ultimate termination. THE SINUSES, PELVIS, AND URETERS. The sinus, pelvis, and ureters are covered by three layers of tissue — a fibrous, a muscular, and an epithelial. 134 THE URINARY TRACT. The fibrous coat is an extension of the capsule, lies in contact with the kidney-substance proper, and continues as the outer coat of the ureters, at the distal end of which its fibers merge into the outer surface of the bladder. The muscular coat in the sinus and pelvis consists of two coats — an mder (next the fibrous coat) longitu- dinal, and an inner circular. Over the papillae the longitudinal fibers disappear. In the ureter the same layers persist, with the addition, near the bladder, of a third more internal coat, in which the fibers run longi- tudinally. The epithelial coat is continuous with the lining of the papillary ducts, immediately becoming of the traii- sitional variety at the orifices of those structures, and extending to the epithelial lining of the bladder. A slight basement meinbrane underlies the epithelial coat and separates it from the muscular. A few blood-vessels and nerves are found, mostly in the outer fibrous coat. THE XJRINARY BLADDER. The bladder has a fibrous, a muscular, and an epi- thelial coat, continuous with those of the ureters. At the areas covered by the peritoneum a fourth or serous coat will be found. The fibrous coat is rather thin, and contains numer- ous fibers of yellow elastic tissue. The muscular coat composes the larger part of the bladder-wall, and contains three poorly defined layers of smooth muscle-fibers : viz., an outer longitudinal, a middle circular, and an inner longitudinal. The epithelial coat is of the transitional type, and is thrown into folds when the bladder is empty and THE URETHRA. 135 contracted, tlie cells then being thicker and more nearly spheric. When distended, the cells become more elongated and flattened. All the coats are richly supplied with cajjillary blood- vessels. Lymphatwn are also abundant, especially so just beneath the epithelial surface, in which locality lymph- follicles also occur. Both viedullated and nonmedullated nerve-fibers as well as small ganglia may be observed in moderate numbers. Fig, 68. — Urinary bladder nuicous membrane; a, Epithelium of tlie transitiODal type ; h, nniscular coat. THE URETHRA. The male urethra has three layers, from within out- ward — a mucous, a muscular, and a fibrous may be dis- tinguished. The mucous coat has an epithelial surface, varying in different localities and resting upon a fibro-elastic tunica propria, or basement membrane. The epithe= lium is transitional, and is continuous with that of the bladder in the prostatic portion. In the membranous 13G THE UKINAEY TRACT. portion it is columnar and stratified ; in tlie spongy or penile portion it is' but a single layer in thickness, and is columnar. In the fossa navicularis it is continuous with the external covering of the gians jtenis, and is of the stratified squamous \'ariety. Small racemose glands (the glands of Littre) occur throughout the length of the mucous coat. The muscular coat is of smooth muscle, arranged as an inner lonf/lkuUnal and an outer circiihir layer in the prostatic and membranous portions of the urethra, but disappearing in the penile portion. The fibrous coat surrounds the muscular ; when present in the penile portion, it supports the mucous membrane. The female urethra has the same three coats as the male : viz., mucous, nmscular, and fibrous. The inner surface, especially near the meatus, is covered with irregular projections — the papilla'. The mucous coat is lined throughout with sirafificd firpia- mous epithelium. The tunicit 2^'>'opria is aumVdr to that in the male, but the small glands are much fewer in number. The fibers of the muscular coat are also ar- ranged in an inner lonc/itudinal and an outer circuleir layer. The mucous coed is richly supplied with ceqrd- laries. Lymphatics and nerves occur in abundance be- neath the mucosa, the latter terminating just below the epithelium. QUESTIONS FOE CHAPTER IX. 190. Describe the gross appearance of the kidney. 191. "Wliat is the capsule? cortical portion? medullary portion? Wliat are the pyramids of Malpighi ? the papilhe ? 1112. What are the colnnins of Bertlni? 193. What are the niednllary raj'S or pjTamids of Ferrein ? 194. What is the lahyrinth? QUESTIONS. 137 195. "\ATiat is the hilum ? pelvis? sinus? "Wliat are the iiifiin- dibula, or calyces ? 196. "What is a uriiiif erous tubule ? 197. Outline general course of a tubule; give names of each location. 198. Describe a Malpighian body. 199. ^^^lat is the capsule of Bowman ? 200. Give the structure of a uriniferous tubule. 201. Give relative sizes of tubules in diiierent locations. 202. How does the size of the lumen compare with the size of the cells surrounding it ? 203. Describe the blood-supply of the kidney. 204. What is the arterial arcade ? 205. "Wliat are the arteriaj rectae ? 206. Wliat are the vente stellse ? 207. Describe the lymphatics of the kidney ; nerve-supply. 208. What is the structure of the sinus, pelvis, and ureters? 209. Describe their tibrous coat; muscular coat; epithelial coat. 210. Of vifhat coats is the urinary bladder composed '! 211. Describe its fibrous coat ; muscular coat; epithelial coat. 212. What are the layers composing the urethra ? 213. Describe the mucous coat; ^muscular coat; fibrous coat. 214. Describe the female urethra. CHAPTER X. THE MALE GENERATIVE ORGANS. THE TESTICLE. The testicle is a compound arrangement of coiled tubular glands. It is covered externally by a capsule of fibrous elastic tissue, the tunica albuginea, which at the posterior portion becomes very much enlarged, in which location it is called the mediastinum, or body of Highmore. The tunica albuginea is further divided into two layers : the outer, covering most of the organ, being an extension of the peritoneum, has the structure of a serous membrane, and is called the tunica vaginalis ; the inner contains a rich blood-supply, and is called the tunica vasculosum. The mediastinum and the tunica vasculosum are con- nected by septa of fibrous tissue, which divide ithe body of the organ into irregularly pyramidal lobules. In these lobules lie a varying number of the seminifer- ous tubules (from 300 to 800 in all), which begin as closed tubes near the periphery of the lobule and run to the edge of the mediastinum, where they unite into from 20 to 30 larger ducts (the vasa recta) and enter the mediastinum, anastomosing with one another to form a mass, called the rete testis, whence they emerge from the upper edge of the mediastinum as a dozen or so tubules (the vasa efferentia). These pass through the tunica albuginea, and at first follow a straight 138 THE TESTICLE. 139 course ; then form a series of conic masses (one for each tubule), called the coni vasculosi, the entire mass constituting the globus major of the epididymis. At the bottom of the globus major all the tubules open into a larger single tube (the body of the epididymis), which runs a very convoluted course, dilating at its end Globus Major. Septa Va^a Effe.ientia. Fig. 69. — Vertical section of tlie testicle to show the arrangement of the duct. to form the globus minor, which empties into the vas deferens. This follows the spermatic cord through the internal abdominal ring and passes to the base of the bladder, where it joins the duct of the vesicula semi- nalis to form the ejaculatory duct, which passes through the prostate to the verumontanum of the urethra. 140 THE JIALE aENEEATIVE OKGANS. The seminiferous tubules may be divided into three portions : 1. The convo/iited tubules, occupying about the outer three-fourths of tlie lobules. 2. The straiffht tnljtdcs, which continue to the vasa recta. 3. The tubules in the incdiastunnn. Fig. 70. — Testicle : a, Tunica albnginea ; &, seminal tubule. In structure the seminiferous tubules consist of an outer covering oi flat endothelial cells, which surround a thin basement membrane. Internal to this are several layers of irregular epithelial cells, more or less of which will be found to be in process of karyokincsis according to the func^tional activity of the organ. Tiie outer epithelial cells are called the parietal THE TESTICLE. 141 cells, and are of two kinds : the first, or sustentacular cells, or Sartoli's columns, take no active part in the production of the spermatozoa ; the second, or sperma- togenic cells, are the eventual jirogenitors of tiie sper- matozoa. Inside of the parietal cells a sc^cond layer may he disting-uislied, many of wliicli in the active organ will be found to exhibit mitotic figures. These Fig. 71. — Tubule of te.'^ticle: a, Fibrous tissue surroundiug tubule; 6, base- ment membrane; c, sustenlacular pells; d, spei mato^eiiic cells; p, niolher cells in the process of mitosis;/, daughter cells ; g, spci niatoblasts ; A, spei'malozna. cells are tlie direct descendants of the spermatogenic cells, and are called the mother cells. The mother cells by their multiplication give rise to a third layer of cells, internal to the previous two, called the daughfer cells. These cells are somewhat smaller than the mother cells, and at the inner portion of the layer many of their nuclei may be seen from around which 142 THE MALE GENERATIVE ORGAN'S. most of the cell-body has disappeared, forming the spermatoblasts. From the spermatoblasts the sper- matozoa are formed, and may be seen with their heads embedded among the spermatoblasts and the daughter cells. The spermatozoa in man are about 50 microns in length, and consist of a head, a body or middle piece, and a tail. The head is flattened ovoid in shape, its under sur- face beinsr sliffhtlv concave. It measures about one- twelfth of the entire length of the spermatozoa, or 3 or 4 microns. The body is attached to the posterior part of the B ;? UL Fig. 72. — Spermatozoa; A, Flat view; B, side view; o, head; b, body; c, tail; d, axial fiber. head, where it is about 1 micron wide and tapers down for a distance of from 4 to 6 microns, where it joins the tail as an extremely delicate filament. The fail forms the greatest part of the total length, measuring about 40 micrfins. It is a very thin, hair- like filament, which, when the spermatozoa is alive, has a very rapid lashing movement, by virtue of which tlie element is enabled to travel at a considerable rate of speed in fluids. Running through the center of the body and tail is a fine line, called the axial fiber, wliich at the end of the tail is uncovered and forms the termi- nation of that part. The spermatozoa possess much vitality, being able under favorable circumstances to THE TESTICLE. 143 retain their power of movement for several days out- side the body. The scmhiiferoufi tubules are held together by loose connective tissue, embedded in which at irregular inter- vals small masses of polyhedral epithelial cells occur, termed the interstitkU ceUs. These are the remains of a fetal structure — the Wolffian body. The straight tubules are smaller than the convoluted tubules, measuring only about 25 microns in diameter. They are lined with a single layer of short columnar epithelium, the external coat remaining the same. The tubules of the rete testis vary nuicli in size, and are lined by a single layer of flat epithelium. The vasa efferentia and the coni vasculosi are lined by several layers of columnar cpithclmm, the innermost layer of which is provided with long cilia. The fibrous coat contains many fibers of smooth mus- cle, arranged cii'cularly. The epididymus is similar to the vasa eiferentia in structure, but the smooth muscle-fibers increase in num- ber and size. The vas deferens, or spermatic duct, has, in addi- tion to the structure of the epididymis, a well-marked, smooth, muscular coat, the inner layer of which runs circularly, the outer layer longitudinally. The vesicula seminalis continues the structure of the vas, but contains in its mucosa numerous small tubular glands. The ejaculatory duct diifers from the vesicula semin- alis in being lined by a single layer of columnar epi- thelium. The blood supply of the testicles enters the tunica vasculosa and mediastinum, whence it is distributed through the septa, and thence by small branches to the intertubular connective tissue, there breaking up into 144 THE MALE GENERATIVE ORGANS. capillaries surrounding the tubules and returning through veins accompanying the arteries. Two sets of lymphaiics are present : the first, within the tunica albuginea ; the second, or deep, surrounds the seminiferous tubules and rete testis, emptying into the large lymphatic vessels of the spermatic cord, which in turn terminate in the lumbar glands. Both medullated and nonmeduUated nerve-fibers are found between the seminiferous tubules. " THE SEMEN. The semen contains, besides the spermatozoa, numer- ous epithelial cells ; round, albunmious granules ; clear, waxy, cylindric masses from the vesicula seminalis ; and some spheric or irregular yellowish bodies, which con- tain concentric markings suggestive of those found in the potato starch. These bodies are called the pros- tatic concretions, or amyloid bodies. THE PENIS. The body of the penis is covered externally by skin with its stratified epithelium, the subcutaneous tissue of which contains little or no fat. It is free from hairs, and at the juncture of the prepuce and glaus numerous small tubular glands (the glands of Tyson, or glandulse odoriferae) occur, wliicli secrete the smegma. The glans penis is covered with a stratified mucous membrane having but little submucosa and being firmly adlierent to the underlying corpus spongi- osum. The under surface of the mucosa is indented by large papillfe, in \\-hich the genital corpuyclc.s are situated. Beneath tlic subcutaneous tissue in the dorsal portion of the organ is found a tiiick oval sheath of longitudinal THE PENIS. 145 fibrous tissue, interspersed with much yellow elastic tissue (the tunica albuginea), surrounding two masses of erectile tissue (the corpora cavernosa), each of which is also covered with an individual circular coat of fibro-elastic tissue. Below the corpora cavernosa is another body of erectile tissue, surrounded by a less distinct sheath, called the corpus spongiosum, in the center of which is situated the urethra. The corpora cavernosa are composed of very numer- Fig. 73. — SecUon of erectile tissue : tr, Blood spaces ; 6, blood-corpuscles ; c, walls composed of fibrous tissue aud smooth muscle. ous branching irregular trabeeuke, which extend from the surrounding fibro-elastic sheath, and contain scat- tered groups of smooth muscle-fibers. The spaces formed between the trabeculse are lined with endo- thelium, and, being connected with the arteries and veins, form large sinuses, which become enormously distended during erection. The corpus spongiosum contains much the same structure as the corpora cavernosa, the trabeculse, 10 146 THE MALE GENERATIVE OUGAN«. however, being much finer and the blood spaces smaller and more regular in size. At the glans it ex- pands, covering the ends of the ('(trpora cavernosa, and is covered directly by the nmcosa of the glans. The male urethra lies in the center of the corpus spongiosum, and extends from the bladder to the meatus. The blood supply is derived from the dorsal arteries and the arteries of the corpora cavernosa, which break up into capillaries, most of which empty into the blood spaces of the corpus spongiosum and corpora cavernosa, thence to be drained by the small veins emptying into the dorsal vein or to jiass out at the root of the organ into the prostatic venous plexus. Some of the arteries entering the corpora cavernosa do not at once break up into capillaries, but form tor- tuous vessels, which in the nonerect condition of the organ form loops, which project into the cavernous spaces. These have been called the helicene arteries. ^lany of the capillaries from these arteries supply the tissue of the trabeculse and return through the veins without emptying into the cavernous spaces. A deep and a superficial set of lymphafk^ are present ; the latter being distributed in the subcutaneous tissue and accompanying the superficial vessels, and terminat- ing in the inguinal glands ; the former arising in the corpus sjjongiosum and corpora cavernosum, following the deep blood-vessels, to terminate in the deep lymph- atics of the pelvis. The nerre.s are both medullated and nonmedullated, from the pudic and hypogastric plexus of the sympa- thetic. Both the Pacinian bodies and genital corpuscles are found. THE I'ltOSTATE. 147 THE PROSTATE. The prostate is a comjiound tubular gland, and is inclosed by a two-layered capsule, the outer layer of which is fibrcius tissue, the inner layer, smooth muscle. From the muscular layer the main stroma of the gland is derived, containing but occasional fibrous tissue bundles. The acini of the gland are lined with Fig. 74.— Prostate: a, Acini; b, prostatic concretion ; c, iutertubular smooth muscle. a single layer of columnar epithelium. Frequently, between this epithelium and its basement membrane numerous small, roundish cells are found. Occasion- ally, especially in old age, the acini will be found to contain clearish, rounded, laminated masses, of an albuminous nature, called the prostatic concretions. The larger ducts are lined with a stratified epithelium. 148 THE MALE GENERATIVE ORGANS. continuous with that of tiie urethra. The blood supply enters the capsule and is distributed in a rich capillary network about the acini and within the fibrous capsule. lAjniphatic clefts occur in the fibrous septa and accompany the veins. Medullated and nonmedidlated nerve-fibers occur between the acini, but their mode of termination is unknown. Corpuscles of Vater are also occasionally found. COWPER'S GLANDS. Cowper's glands are two small, compound, saccular or racemose glands lying beneath the membranous urethra. The acini are lined by a single layer of short columnar cells. QUESTIONS FOR CHAPTER X. 215. What type of gland is the testicle ? 216. What is the tunica albuginea ? 217. What is the mediastinum ? 218. Into what is the tunica albuginea divided ? 219. Describe the lobules. 220. Describe the course of the seminiferous tubules from their beginning to the ejaculatory duct. 221. What are the three portions of the seminiferous tubules proper ? 223. Describe the structure of a seminiferous tubule.. 223. What are the sustentaoular cells ? 224. What are the spermatogenetic cells ? mother cells ? daughter cells? spermatoblasts? 235. Describe the spermatozoa. 236. What are the interstitial cells of the testicle ? 237. Describe the vasa. rectis; the vasa- effereutia; the epididy- mis; the vas deferens. 228. Describe the vesiculse seminalis and the ejaculatory duct. 229. Give the course of the blood-vessels in the testicle; of the lymphatics; of the nerves. QUESTIONS. 149 230. Describe the penis. 231. Give the general structures composing the penis. 232. What are the glands of Tyson? 233. What is the character of the co-s-ering of the penis ? of the glans ? 234. What is the tunica alhuginea ? 235. What are the corijora cavernosa ? What is the corpus spon- giosum ? 236. Describe the structure of each. 237. Give the blood distribution of the penis. What are the helicene arteries ? 238. Describe the lymphatics and nerves of the penis. 239. What type of gland is the prostate ? 240. Describe its general arrangement. 241. What are the prostatic concretions? 242. Give the blood supply ; the lymphatic and nerve supply. 243. Describe Coivper's glands. CHAPTEE XL THE FEMALE GENERATIVE ORGANS. THE OVARY. The ovaries are small almond-shaped masses attached to the posterior surface of the broad ligament. They are covered by two layers of tissue. The first is a modified reflection of the peritoneum, containing a single layer of columnar epithelial cells, called the germinal epithelium. The second layer is composed of fibrous tissue, and is called the tunica albuglnea. In the germinal epithelium, more especially in the fetus, occasional large, clear, ovoid cells containing a prom- inent nucleolus are found. These are the primor- dial ova, and are the cells from which the ova are developed. The substance of the ovary is divided into a cortical and a medullary portion, which merge imperceptibly into one another. Beneath the tunica albuginea is the ovarian stroma, which consists of a peculiar fibrous tissue containing many long spindle=shaped cells arranged irregularly. Embedded in the stroma of the cortex lie a large number (36,000) of Graafian follicles. These differ in size and appearance according to their stage of devel- opment. 160 THE OVARY. 151 The immature fo/licleti are produced by a downgrowth of the germinal epithelium surrounding oi.e of the pri- mordial ova. This downgrowth is cut off from the sur- face by the growing-in of the stroma and leaving the ovum surrounded by a granular layer of cells of greater or less thickness according to the stage of devel- \ Fig. 75.— Ovary: a, Germinal epitheliiini ; 6, primordial ova; c. tunica al- buginea; J, tbeca follicnli ; e, stratum graiutlosum ; /, discus proligerus; g, corona radiata; h, z()Ma pellucida; /, cavity of liquor folliculi ; j, vitelline mem- brane; fc, vitellus; /, germinal vesicle ; 7r(, germinal spot ; ??, Immature follicle ; 0, stroma. opment. These in turn are surrounded by a slightly denser concentric arrangement of the spindle-shaped cells of the stroma. The mature Chaajian follicles are much larger in size, measuring from 4 to 8 mm. in diameter. They are bounded externally by a denser layer of the 152 THE FEMALE GENERATIVE ORGANS. stroma, called theca folliculi, in which two layers may be distinguished. The outer layer, or tunica externa, is more fibrous and contains the larger blood-vessels. The inner coat, or tunica interna, is more cellular in t'haracter and contains smaller blood-vessels and capil- laries. Inside of the theca folliculi is a granular layer of cells derived originally from tiie germinal epithelium, and called stratum granulosum. At some point the cells of the stratum granulosum * . Fig. 76. — Portion of Graafian follicle and ovary. are heaped up, forming a mass called the discus pro= ligerus, or cumulus ovigerus, the inner layer of which is arranged radially, and called the corona radiata, whiiOi in turn surrounds a delicate radially striated memlirane, the zona pellucida. The centers of the follicles contain a cavity bounded by the stratum granulosa and containing a clear fluid, called the liquor folliculi. The ovum lies within the zona pellucida, and is THE OVARY. 1S3 bounded by a thin, transparent membrane, called the vitelline membrane. Within this is a granular mass, called the vitellus. Situated excentrically in the vitel- lus is the germinal vesicle, which is bounded exter- nally by a delicate wall, contains many chromatin fibers, and a small body, resembling a nucleolus, called the germinal spot. Graafian follicles of all degrees of development between the immature and fully matured may be found. When a follicle is ripe, the liquor folliculi distends it until it ruptures at the surface of the ovary and the ovum is discharged with a portion of the discus pro- ligerus adherent. The wounds in the surface thus formed are healed up by a multiplication of the cells of the stratum granu- losum, forming large polyhedral cells, between which fibers from the stroma carrying capillaries penetrate. The mass thereby produced is yellowish in color, and is called the corpus luteum. This varies in size and development accordingly as pregnancy has taken place or not. If pregnancy has occurred, the mass is called a true corpus luteum ; if not, the development will be much less, and a false corpus luteum results. The blood=supply of the ovary enters at its attach- ment to the broad ligament and proceeds to the medulla, whence branches are given off to the stroma, forming a capillary network in the theca folliculi. The lymphatics are most numerous in the medulla, but also occur in the cortex and theca folliculi. Both medullated and nonmedullated nerve-fibers occur, first penetrating to the medulla, from which fine branches are distributed to the cortex and follicles. 154 THE FEMALE UEXERATIVE OKGA^'S, THE PAROVARIUM. The parovarium, epoophoron, or organ of Rosen- miiller, as it is variously termed, is the remains of a fetal structure culled the Wolffian duct. It is situ- ated in the broad ligament, between the ovary and the Falloijian tube. In structure it is found to contain a numl^er of small converging tubes leading to a larger transverse tube, all of which are lined by short columnar epithelial cells, some of which are found in the lumina of the tubules. THE FALLOPIAN TUBES. The Fallopian tubes, or oviducts, have three coats — an outer fibro.se)-ous, a middle wvsctdar, and an inner mucous. TJie outer or fibroserous consists of a reilection of the peritoneum, being covered externally by a layer of ilat endothelium, supported l)y a layer of fibrous tissue con- taining many fibers of smooth muscle. The muscular coat has two layers — an outer longi- tudinal and an inner circular, the latter being much the larger. The mucous coat has a well-developed membrana propria, which is very much plicated, giving a transverse section of the lumen a very irregular outline. This is lined by a single layer of ciliated columnar epithelium. THE UTERUS. The uterus also contains three coats — an outer serous, a middle museulur, and an imiev cpith died. The serous coat consists of a layer of peritoneum^ THE UTERUS. 155 being covered by a layer of endothelial cells which rests upon a layer of fibrous tissue. The muscular coat constitutes the bulk of the organ, and may, with difficulty, be divided into three layers of smooth fibers, the outer layer of which runs mostly Fig, 77.— Fallopian tube : ii, Tortiiou.s liiiuen ; b, muscular coat; c, fibrous coat. longitudinally, the middle layer mostly circularly, and the inner layer obliquely longitudinally. In all the coats, however, many fibers are found at all angles to the general trend. The epithelial coat contains a single layer of ciliated columnar epithelial cells, which rests upon a thin base- ment membrane, a true submucosa being absent. Scattered throughout the epithelial coat are the 156 THE FEMALE GENERATIVE OKGANS. mouths of wavy, brancliecl tubular glands, the uterine glands, ^vhich are lined by a single layer of ciliated cells resting on a slight basement membrane. These glands, owing to the absence of the submucosa, extend to the muscular coat. The lower jialf of the cervix is lined with stratified squamous epithelium, which is thrown into longitudi- nal folds, and in cross-section resembles papillae. Here, Fig, 78. — Uterus : rr, Epithelial surface ; h, uterine glands ; c, iutertubular fibrous tissue and cells ; d, smooth muscular coat. also, short mucous crypts occur, which occasionally become occluded and form retention cysts, called the ovulee Nabothi. The blood-vessels penetrate the serous coat to the muscular, where they branch, sending some of their branches to the internal coat, there encircling the uter- ine glands and epithelium in a network of capillaries. THE VAGINA, 157 In the middle coat large thin-walled blood=spaces occur between the fasciculi of muscular tissue. The lymphatics form a network beneath the epi- thelial coat, unite witli slightly larger vessels in the muscular coat, and emj)ty into the large vessels of the serous coat. Medullated and nonmedullated nerve-fibers occur in the muscular coat, sending fine branches to the epi- thelial surface. Along the course of the nonmedullated fibers small ganglia sometimes occur. THE VAGINA. The vagina has three coats — external fibrous, middle muscular, and inner mucous. The fibrous coat is well developed, and contains many fibers of yellow elastic tissue scattered through the main bulk of white fibers. The muscular coat consists of an ovter longitudinal and an inner circular layer of smooth muscle, the boundaries of which are ill defined. The mucous coat consists of a well-developed mem- brana propria, studded with leukocytes, which is thrown into frequent ridges (the rugce) and projections (papillce). This is covered by a deep layer oi stratified epithelium the outer layers of which are squamous. The blood=vessels run near the outer surface of the membrana propria, from which situation smaller branches are sent into the muscular tissue and to the under surface of the epithelium. Between the muscular and mucous coats the veins are arranged in a complex network, giving to the part slight erectile properties. The lymphatics in the mucosa empty into those of 158 THE FEMALE GEJ4ERATIVE ORGANS. the muscular coat, and these in turn communicate with those of the fibrous coat. MeduUated and nonmeduUated nerve=fibers, ganglia and special nerve-endings (the genital end=bulbs, or the genital corpuscles of Krause) occur in the mucosa. The labia majora are covered with stratified epithe- lium, the deep layers of which are more or less pig- mented. Hair follicles, sweat-glands, and sebaceous follicles are numerous. Beneath the epithelium is a loose areolar tissue containing much fat and some muscu- lar and elastic fibers. The labia minora are covered with stratified epi- thelium, which contains neither fat, hair follicles, nor sweat-glands. The subepithelial tissue is loose in tex- ture and contains many large blood-spaces, making the tissue moderately erectile. MeduUated and nonmeduUated nerves and genital corpuscles occur. The clitoris consists of two masses of erectile tissue (the corpora cavernosa) inclosed in a sheath of fibrous tissue and covered externally by stratified epithelium. Genital corpuscles are numerous. The glands of Bartholin are small raoemofie glands lying at either side of the ostium vaginae. They are lined with clear mucous cells, wliich discharge their secretions through a tube lined with short columnar epithelium. THE MAMMARY GLANDS. The mammary glands are complex tubular glands, the several lobes of which are held together by fibrous tissue and fat, and empty side by side through the THE M A:\1.M ART GLANDS. 159 nipple. The acini are lined by a single layer of gran- ular, polyhedral epithelial cells, which rests upon a dis- tinct nieml)rana propria. As in other glands, the acini are grouped into lobules and then into lobes, all of which are surrounded by a greater or less amount of fibrous tissue accoi'ding to their size. Fig. 79.— Mammary gland : a, Acini ; b, cells cnnfaining globules. During lactation the epithelial cells are seen to con- tain numerous droplets of oil in their substance. More or less oil will also be found in the acini. The blood-vessels run between the lobules and send branches into the fibrous tissue, which break up into capillary network surrounding the acini. The gland is well supplied with lymphatics, which occur both in the subcutaneous tissue and in the inter- acinous fibrous tissue and communicate with the glands of the axilla and slightly with those of the anterior mediastinum. The milk consists of a clear fluid, suspended in which are immense numbers of oil droplets, together 160 THE PEMALB GENERATIVE ORGANS. with some granular matter from the cells lining the aoini and tubules. During the first few days of lactation certain large, granular, fatty, highly refracting bodies occur, which have received the name of colostrum corpuscles. Fig. 80.- -Elements of milk: a> Droplets of oil in milk; 6, leukocytes; c, large colostrum corpuscles. QUESTIONS FOR CHAPTER XI. 244. Describe the general characteristics of the ovary. 24.5. Wh&t is the germinal epithelium ? the primordial ova ? 246. What is the tnnica albuginea ? 247. What is the ovarian stroma ? 2 18. What are the Graafian follicles ? Where do they originate ? 249. Give the structure of the mature Graafian follicle. 2^^0. Describe a corpus luteum. 251. Describe the ovum. 252. Name the layers of the Graafian follicle and ovum in their sequence. 253. Describe the blood-supply of the ovum; the lymphatic; the nerve. 2.i4. 255. 256. Descrilie the parovarium. Describe the Fallopian tube; give its structure. Name the coats of the uterus. Describe each. QUESTIONS, 161 257. Describe the uterine glands. 258 Describe the cervix. 259. What are the ovulaj Nabothi ? 260. Describe the blood distribution of the uterus; the lym- phatics; the nerves. 261. Name the coats of the vagina. Describe each. 262. Give the blood-, lymph-, and nerve-supply. 263. Describe the labia majora, the labia minora, and the clitoris. 264. Wliat are the glands of Bartliolin ? 265. What type of glands are the mammary glands ? 266. Describe them. 267. Give their blood- and lymphatic supply. 268. Describe the milk. 269. What are colostrum corpuscles? 11 CHAPTER XII. THE RESPIRATORY SYSTEM. The larynx is lined with stratified ciliated epithe- lium, resting on a thin membrana propria of fibre- elastic tissue. Beneath this is tlie submucosa of fibrous tissue, which c(,)ntains numerous branched tubu- lar glands comnmnicating with the surface. In the external jxirtion of the submucosa are the cartilages of the larynx. Tliose of the thyroid, cricoid, and arytenoid are of the hyaline variety, the epiglottis and the carti- lages of Wrisberg and Santorini being of the yello\v, elastic variety. The trachea is lined with stratified ciliated columnar epithelium resting upon a tunica propria. Numerous small racemose glands dip down from the surface into the submucosa below. The submucosa is surrounded l)v the fibrous coat, embedded in which are a number of C=shaped plates of hyaline cartilage, which surround the trachea on all sides except at its juncture with the esophiigus, and which serve to keep the tubes open. External to the cartilage is a slight layer of circular, smooth muscle. The larger bronchi continue the structure of the trachea, dividing repeatedly until the smaller tubes are reached, when the cartilage rings become smaller and smaller, until they entirely disappear. The epithelium is reduced to a single layer and the muscular coat be- comes relatively better developed. 162 THE LONCiS. 1(« THE LUNGS. The smaller bronchi divide until the terminal bronchi arc reached, the diameter of each of which is about 1 mm. (Jj inch). These, again, branch to form Fig. 81. — Bronchial tube: a, Mucous membrane; 6, muscularis mucosfe; c, cartilage plate ; d, lung tissue ; e, small artery ; /, bronchial glaad ; ff, duct of bronchial gland. narrow tubules, the alveolar ducts, which open into dilated pouches, called the infundibula, from which again a number of air-sacs or alveoli open. 164 THE RESPIRATORY SYSTEM. The alveolar ducts are lined with nonciliated low columnar cells lying on thin, fibrous, elastic basement membrane. The alveoli are lined with a single layer of epithe- lium. The groups of acini belonging to a terminal bronchus are united to a number of similar groups by fibro-elastio tisstie to form a lobule. Fig. 82. — Diagram of bronchial terminations: n, Siiialler bronchus; b, ter- minal bronchus ; r, alveolar dnct ; ti, cnnslrictinii, or ncclc ; e, space of inl"nn- dibiilutn outlined by dotted lines ; /, infundibnla ; (f, ciiiateO colnmmir cells lin- ing small bronclms; h, nonciliated columnar cells lining alveolar ducts ; i, flat epithelium lining alveoli. Numerous lobules are similarly united to form the lobes, the external surface of which ai'e covered by a serous membrane, the pleura. The blood-vessels follow the course of the bronchi, dividing into a capillary network in the alveolar walls THE LUNGS. 165 to surround tlie alveoli witli a very complete network. It is in tiiese eapillai-ies tluit the oxidation of the blood takes place, the gases having to traverse onlv the capil- lary wall, an extremely small amount of tibro-elastic tissue, and the thin epithelial lining of the alveoli. The veins return by the side of their respective arteries. Fi^. 83. — Section of Uiiifj: a, Cross-section of small bi-oncbiis; 6, alveolus; c, alveolar wall lined with flat epitbeliinn ; (/, lop wall of iilveulus entirely cut across; e, section into infundibnliini, sliowing several aheuli opening into it. Other small branches from separate arteries occur which serve entirely to supply nutrition to the tissue. The lymphatics form three systems : the first is found in the connective tissue beneath the pleura and communicates with the pleural cavity. The .second accompany the blood-vessels between the lobules. 166 THE RESPIRATORY SYSTEM. The third begin under the epithelium of the bronchi, follow the blood-vessels to the root of the lung, where they unite with the previous two systems and pass into the bronchial glands. Numerous masses of diffuse adenoid tissue occur in Fig. 84. — Section of lung in which the blood-vessels have been injected with carniin gelatin: a, Small artery, showing branches around alveoli and at (h) forming network over alveoli. the submucosa of the trachea and bronchi, and small nodes occur especially near their bifurcations. Both medullated and nonmedullated nerve=fibers are found following the course of the blood-vessels and THE THYROID. 167 lyiiipliatio vessels. The ternnnatii)n of the fibers is unknown. THE THYROID. The thyroid is a comjxmnd tubulai- gland, the excretory ducts of which are closed. It falls within the classification of "ductless glands." It is surnmnded hv a capsule of fibrous tissue, wliich penetrates the body of the organ, dividing it into irregular lobules. Fig. 85. — Thyroid gland : a, Acini completely filled with colloid material ; b, same partly filled. The acini are lined with short, columnar epithelium, resting upon a well-marked basement membrane. The lumen of the acini contain epithelial cells, leukocytes, granular mattei', and occasional red blood-corpuscles, held together by a yellowish, gelatinous mass of colloid substance. The blood=vessels enter the fibrous tissue between the lobules, and send rich capillary network to surround the acini. 168 THE RESPIRATORY SYl^TEM. The lymphatics are quite numerous, being found in the connective tissue of the caijsule and between the lobules. QUESTIONS FOR CHAPTER XII. 370. Describe the structure of the larynx. 271. Describe the structure of the trachea. 272. Describe tlie general structure of the air-passages. 273. Wliat is the structure of the alveoli ? 974. What structures separate the air from the blood in the aheolar capillaries? 275. Describe the bloorl-supply of the lungs, the lymphatics, and the nerve-snpijly. 976. Wliat type of gland is the thyroid ? Describe its structure. 277. What substance is found in its acini ? 278. Describe its blood-vessels and lymphatics. CHAPTER XIII. THE CUTANEOUS SYSTEM. The cutaneous system embraces the skin, nails, hair, and glands. The teeth are also sometimes in- cluded,, but have been described with the digestive system. THE SKIN. The skin consists of two distinct portions — the cutiok, epidermis, or false skin, and the corium, cutis vera, or tnie skin. The epidermis is the more external of the two, and consists of several layers of epithelial cells, varying much in thickness in diiferent locations. The innermost layer of these cells (the stratum Malpighii, or rete mucosum) rests upon the irregu- larly projecting papillse of the corium and consists of two or three layers of columnar cells. These cells are in rapid process of growth and multiplication, which is indicated by their darkly and easily staining. In the colored races, and in some situations in the white, these cells are found to contain pigment, to which the color -of the skin is due. External to these cells a layer of irregularly poly- hedral cells connected with each other by minute spines is found, called the prickle cells. Outside of these a narrow layer of flattened polyhedral cells containing many granules of eleidin occur, called the stratum granulosum. 169 170 THE CUTANEOUS SYSTEM. Above this is a narrow layer of still flatter polyhe- dral cells which are largely transformed into keratin, the nuclei showing very indistinctly (the stratum lucidum). Fig. 86. — Skin: A^ Epidermis; i?, cutis vera; a, stratum Malpigliii ; b, pricltle cells ; e, stratum granulosum ; d, stratum lucidum ; e, stratum corueum ; /, duct of sweat-gland ; g, coil of sweat-gland ; h, adipose tissue. External to this and more superficial is the stratum corneum, consisting of squamous plates of hardened THE SWEAT-GLANDS. 171 keratinized epithelial cells, wliicli have entirely lost the appearance of ever having been nucleated. The corium consists of two layers of flbro-elastic tissue ; the external, a stratum papilis, is quite dense and at its upper surface projects into the epidermis as papillie, the ujiper surface of which contains the tactile nerve-organs. The internal layer, or stratum reticu- lare, is much Ioosit in texture and merges gradually into the underlying tissues. THE SEBACEOUS GLANDS. The sebaceous glands are small racemose glands, situated in the corium, their excretory ducts discharg- ing into the hair follicles, or from the free surface of the skin in localities where hair is absent. The acini are lined by one or two layers of cuboid epithelial cells, the lumen being filled with a mass of degenerated cells, granular detritus, and a fatty, waxy secretion of the cells. THE SWEAT-GLANDS. The sweat-glands, or sudoriferous glands, are coiled, tubular glands which occur in great immbers (2,000,000) throughout the skin. The deeper portions of the glands lie in the stratum reticulare as a round- ish, coiled mass, the excretory duct being straighter. The gland tubules consist of a single layer of pyra- midal columnar cells resting upon a distinct basement membrane. In many of the glands, especially those of larger size, a more or less complete layer of smooth muscle exists between the cells and basement mem- brane. The excretory duct is slightly smaller in size and lined with low cuboid cells up to the epidermis, where 172 THE CUTANEOUS SYSTEM. the course of the tubule becomes more spiral, its walls being formed by the epithelial cells until it terminates in a funnel-shaped expansion at the surface. D:'^~rcS Fig. 87.— Skin and lonj^ilndinal section of hair: a, I'^pidermis ; &, corium ; c, sebaceous gJand; t/, fibrous root slieatb ; e, glassy membrane; /, outer root, slieatb ; g, inner root sheatli ; Ii, expanded bulbous end of hsiir; i, papilla of bair; j, arrector pili ; fc, adipose tissue. THE HAIR. The hair is derived from the skin, and consists of two divisions — that within the skin called the root, and that external to the skin, the shaft. THE HAIR. The root lies embedded in a deep depression called the hair follicle. The shaft consists of three layers — the cuticle., corti- cal, and medulla, all of which are composed of more or less modified epithelial cells. Fig. 88. — Cress-section of hair and follicle at level of root; a, Cut end of longitudinal fitjer.s of sheath ; b, circular fibers; r, glassy menihrane; d, outer root sheath; e,/, Henle's and Huxley's layers of inner root sliealh ; (?, hair cuticle ; /;, cortical portion of hair substance; i, medullary portion of hair sub- stance (sometimes absent). The cuticle is the outermost covering, and consists of a single layer of horny, nonnucleated cells which overlap one another like shingles. The cortical or middle layer is the thickest^ and is 174 THE CUTANEOUS SYSTEM. composed of many strata of greatly elongated, indis- tinctly nucleated, iiorny ejiitlielial cells, which are very intimately united with one another. These cells become broader and shorter in the root, where, not having become entirely altered, they resem- ble the cells of the stratum mucosnm. Scattered through the cortical portion is a greater or less airfount of pigment upon which dejiends the color of the hair. The medulla or pith is often absent, but when present, lies in the center of the hair fiber. It consists of two or three columns of cuboid cells which are usually filled with minute air-spaces, which give the medulla a silvery appearance when viewed In' reflected light, but by transmitted light it appears black. The hair follicle is a flask-shaped depression of the epidermis which extends down into the corium or sub- cutaneous tissue, according to the size of the hair, is surrounded by a fibrous sheath from the corium, and tightly encircles the hair root. At the bottom of the follicle a small projection of the fibrons sheath (the hair papilla) extends a short dis- tance into the hair bulb, carrying with it blood-vessels and pigment cells. The outermost coat of the follicle is the fibrous sheath, which is derived from the corium, and consists of three layers — the outer longitu(Ji)i(il, the middle circular, the inner glassy or hi/aline layer, a delicate structureless membrane upon which the epithelium of the middle coat rests. The middle coat of the follicle is called the outer root sheath. It consists of a number (8 to 10) of rows of cells directly continuous with those from the rete mucosum of the epidermis. The outer cells are colum- nar ; those more internal become polyhedral. THE NAILS. ITS The inner coat is called the inner root sheath, and consists of two layers. The outer of these is called Henle's I'li/er, and is composed of a la^'cr of elongated, nonnucleated, granular polyhedral cells. Tiie inner layer is called Huxley's layer, and is composed of one or two layers of polyhedral cells containing granules of eleidin and small nuclei. Tlie inner cells of Huxley's layer rests directly upon the cuticle of the hair root. The arrectores pilorum are small bundles of smooth muscle-fibers which extend from the fibrous coat of the hair follicles to the upper surface of the corium. The contraction of these muscles raises the hair from an oblique to a vertical position. THE NAILS. The nails consist of three portions — the root, the body, and the free margin. The nail groove surrounds the root and sides of the body, the free margin projecting beyond the finger tips. The floor of the nail groove upon which the body rests is called the nail bed, tiiat portion supjiorting the root being called tiie matrix. The nail groove has the same structure as the skin. The nail bed consists of a ])rolongation of the corhim, the upper surface of which is thrown into longitudinal ridges (instead of papillae, as in the skin) that are covered by a number of layers of epithelial cells, re- sembling and continuous with the stratum Malpighii of tiie skin. The nail is virtually a greatly hypertrophied stratum lucidum which is formed only above the matrix and pushed forward as the cells of the matrix multiply. 176 THE CUTANEOUS SYSTEM. QUESTIONS FOE CHAPTER XIII. 279. What does the cutaneous system embrace ? 280. Name the two portions of the skin. 281. Describe the stratum Malpighii. 282. What are prickle cells? 283. Describe the stratum granulosum. 284. Describe the stratum lucidum ; stratum corneum. 285 Describe the eoriuiu. 286. "What are the papilla;? 287. Describe the sebaceous gland. 288. Describe the sweat-gland. 289. Name the divisions of the hair. 290. Describe the shaft. Describe each layer separately. 291. What layers compose the liair follicles? Describe each separately. 292. What are the arrectores pilorum ? 293. Name the three portions of the nails. 294. Describe the nail groove, the nail bed, and the matrix. CHAPTEK XIV. THE EYE. The eye consists of the (iiderior and the ijosteiior chambertt, which are separated by the irin and leim. The anterior chamber is limited in front and at the sides by the transparent cornea; jwsteriorl}- by the iris and lens. Tlie posterior ctiamber is surrounded by the retina, the clioroid, and the sclera. The retina covers the posterior portion of the inner surface of the eye and extends nearly to the ciliary body, where it terminates in a ragged edge, called the era serrata. In the center of the retina, posteriorly, is an elevated spot, the macula lutea, in the center of which is a slight depression, called fovea centralis. The choroid surrounds the retina externally, is ■pierced centrally by the optic nerve in its passage to the retina, and terminates in front in the ciliary process and iris. The sclera is continuous posteriorly with the sheath of the optic nerve, passes forward, and joins the cornea near the latitude of the iris. Just before its junction with the cornea it is joined l)y a reflection of the con- jimdlva, the epithelium of which becomes modified and continues over the remaining anterior portion of the sclera and the entire cornea. The lens is a biconvex, transparent body, situated immediately behind and in contact with the iris, and is held in position by the suspensory ligaments which are attached to the ciliary body. 12 177 178 THE EYE. The anterior chamber is filled with a clear fluid, tlie aqueous humor. The posteridr chamber coiitiiins a thin, transparent, jelly-like substance, called the vitreous humor. Fig. 89. — Diagram of eye : A , Anterior chamber occupied by aqueous humor ; B, posterior chauiber occupied by vitreous ; r, crystalline leus ; a, conjuuctiva ; 6, cornea ; c, letiuu ; d, choroid coat ; e, sclerotic coat ; /, rectus interuus muscle ; g, iris; A, caual of Scbleuim; i, corueoscleral junction ; j, optic nerve; k, central artery ; /, entrance of optic nei've. The cornea contains five layers, which, named from without inward, are the anterior epithelium, the ante- rior limiting membrane, the substantia propria, the posterior limiting membrane, and the posterior endothe- lium. THE CORNEA. 179 The anterior epithelium is a stratified epithelium, the innermost cells of which are cuboid, becoming flat- ter as they progress outward until the outer layers are squamous. The anterior limiting membrane, anterior elastic lamina, or membrane of Bowman, is a moderately thick basement mend:>rane, consisting of s])ecialized fibrous tissue. The substantia propria constitutes the main bulk of / y ' ] X . u J an i.i-a yir-1 Fig. 90. — Cornea; (T, Exfernal epithelium ; &, anterior elastic lamina; c, sub- stantia propria; (/, posterior limiting membrane ; e, posterior epithelium. the cornea, and is composed of obliquely arranged bun- dles of fibrous tissue, \vhieh are bound together by clear cement substance (interfibrillar cement substance) and a few white fibers, which are called the fibrae arcuatae. Between the fiber bundles and in the cement sub- stance lie large numbers of irregular stellate lymph- spaces (the hicumr^ or (■oi-ncal spaccx), Avhich are joined by a network of small canaliculi. In these spaces, ISO THE EYE. and folliiwiiia; their general outline, lie the corneal cor- luiHcka, -which unite by their stellate processes. The posterior limiting membrane, posterior elastic lamina, or Descemet's membrane, is a thin, clear membrane, resembling the anterior limiting membrane. The posterior endothelium, or Descemet's endothe- lium, consists (jf a single laver of flat endothelial cells, resting directly on the jjosterior elastic lamina. ^Vfter bii'th, the c(n'nea contains no blood=vessels excepting in a narrow zone (the limbos), just at its periphery. Lymphatic spaces occur in the lacunae and canaliculi, and also around the large nerves. The nerves are branches of the ciliary n<'rvcs, enter till.' substantia propria as meduUated fibers, whicli at once lose tiieir medullary sheath and form a network beneath the anterior epithelium, called the subepithelial plexus, which send still finer branches between the epithelial cells, called the intra=epithelial plexus. A few branches are also sent into the posterior portion of the substantia propria. THE RETINA. The retina may be divided structurally into three parts — the retina jyroper, the macula lutca with the fovea centralis, and the ora serrata. The retina proper contains ten layers. ?\amed from within (in contact with the vitreous humor) outward (to the choroid coat), they are — 1. Internal limiting membrane. '1. Lavcr . Ijayer of ganglion cells. 4. The inner molecular, granular, or reticular layer. ;!. Inner nuclear layer. 6. Outer molecular, granular, or reticular layer. T?rE RETINA. 181 7. Outer nuclear layer. S. External limiting membrane. 9. Layer of rods and eones. 10. Pigment layer, pigmented epithelium of the „ J© ISO P 60„0 °o 009,0 „ ffll&iS:P^^ — ..4V Jil A- Fig. 91. — Section of retina ; a, Pigment layci- ; &, layer of rods and cones ; c, external limiting membrane; ; (/, canal of Schlemm ; fi, point of tlie junction of the cornea and sclera; /, suspensoi'y ligamenl of lens. A small number of nonmedullated nerve=fibers are found being distributed to the blood-vessel walls. Small ])erivasciilar lymph=spaces are occasionally seen around the veins of the stroma. SCLERA. The sclera contains three layers : The innermost consists of a layer of endothelial cells, which separates it and the choroid. The middle layer constitutes the bulk of the coat, 188 THE EYE. and is composed of dense, white fibers and yellow, elastic fibers, supporting many fixed and wandering connective-tissue cells. The innermost portion of this is somewhat looser in texture, contains numerous branched pigmented cells, and is called the lamina f usca scleras. This layer is also continuous, anteriorly, with the substantia propria of the cornea. The outer layer of the sclera is a layer of endothelial cells. A few small blood-vessels are present which present no characteristic distribution. Lyinph=spaces communicating with one another occur surrounding the cells. Only a few naked axis-cylinders of nerve=fibers are found in the sclera. THE CILIARY BODY. The ciliary body lies on the inner surface of the eyeball, at the anterior portion of the posterior ciiam- ber. It may be divided into three portions — the ciliary ring, the ciliary processes, and the ciliary muscles. The ciliary ring is a continuation of the choroid coat, extending from a point beyond the ora serrata to the ciliary processes. It differs in structure from the choroid in containing numerous smooth muscle-fibers from the ciliary nuiscle, has but little elastic tissue, and the choriocapillaris is absent. The ciliary processes constitute the inner surfiice of the ciliary body, and consist of fibrous stroma which is thrown into a large number (60 to 80) of circular folds. These are covered internally by a thin, transparent membrane, continuous -with the glassy lamina of the choroid. Internal to this is a row of darker pigmented cells, THE IRIS. IHH which, in turn, are odvered l)v a layer of cohimnar cells, internal to which is a thin, transparent, internal limiting membrane. All of these last three layers are continuous with the similar layers of the retina. The ciliary muscle lies external to the ciliary pro- cesses, and contains smooth muscular fibers, whicii are arranged in three directions, and which in contracting, change the form of the lens in the process of accommo- dation. The outer layer of fibers run parallel to the sclera (antero-posteriorly) and are called the meridional fibers. Below these, posteriorly and running at a slight angle, are the radial fibers. In front of the radial fibers a smaller number of fibers run circularly around the ciliary body. These are called the circular fibers. Lying in the sclera, about at the junction of the cornea, sclera, and ciliary body, is a small oval, venous channel, called the canal of Schlemm. The blood supply is not prominent, being distrib- uted chiefly to the ciliary muscle-fibers. A small plexus of mednllated nrrre-fihers is found in the ciliary body, from which small branches pass to the eve and cornea. A small number of ganglion cells also occur. THE IRIS. The iris extends from the anterior edge of the ciliary body, between the anterior and jiosterior chambers of the eye and projects into the anterior chamber. It con- sists of five layers — anterior endothelium, anterior boundary layer, vascular layer, posterior boundary layer, and pigment layer. The anterior endothelium is a single layer of flat, granular endothelial cells, which are continuous with the posterior endothelium of the cornea. 190 THE EYE. The anterior boundary layer consists of meshworks of fibrous tissue, entangling large numbers of Ij'mphoid cells, the whole resembling adenoid tissue. The vascular layer composes the main bulk of the iris, and is composed of loose fibrous tissue, in which lie a radiating plexus of arteries and two sets of smooth muscular fibers. The iris is surrounded by an artery (the cireulus iridis major), from which the above-men- tioned radiating plexus arises and converges to a smaller arterial ring at the margin of the pupil (the cireulus iridis minor). The muscles are arranged in two sets. The inner forms a ring around the pupil, which it narrows upon contraction ; the other set is arranged radially and, upon contracting, serves to dilate the pupil. The posterior boundary layer, or vitreous lamella, consists of a thin structureless membrane, which seems to support the pigment cells. The pigment layer consists of the following layers : The anterior is a layer of spindle-shaped cells, ^vhich are arranged radially and are more or less pigmented. The middle layer is thicker, and consists of cells much more darkly pigmented, so that their outline is lost ; the amount of the pigment in this as well as that of the anterior layer depending upon the color of the eyes, being absent in albinos. The inner layer, euticular membrane, or memhrana Umitans iridis, is a very thin membrane. These layers of the pigment layer are continuous with the pigment layer of the ciliary processes. The nerves in the iris lose their medullary sheath, and are distributed to the circular and radiating mus- cular fibers. THE LENS. 191 THE LENS. The lens is a transparent, biconvex structure which lies immediately behind the iris. It consists of a lenticular mass of lens fibers, covered on its anterior surface by the lens epithelium, the whole Fig. 94. — Lens : A, Fibers longif.udinal ; a, anterior capsule; b, anterior epi- thelium ; c, lens fibers. B, Posterior surface view of auterioi- epitlieliuni. being surrounded by a capsule and retained in position by the suspensory ligament. The capsule consists of a thin membrane of elastic tissue, thicker in front than behind, into which the fibers of the suspensory fibers merge. 192 THE EYE. The lens epithelium consists of a single layer of cuboid cells covering the anterior surface of the lens, and lying just beneath the capsule. At the edge of the lens these cells become much elongated and merge into the lens fibers. The Jens fibers constitute the bulk of the lens, and consist of long, clear, hexagonal fibers, extending from the edge to the center of the lens. The fibers are nucleated near the edge, the remainder being perfectly clear and transparent. They are held together by a clear cement substance, which is reinforced in the cen- tral zone, the fibers there being serrated by a dovetail- ing of the edges. As the fibers do not completely en- circle the lens, there are places where the ends of the fibers abut, which form the stellate areas called the lens stars. Two of these occur, the anterior and the posterior. The suspensory ligament, the zonula ciliaris, or zone of Ziiin, consists of thin fibers which begin at the ora serrata (where they are continuous with the hyaloid membrane of the vitreous body) and, extending over the ciliary processes to which they are attached, pass to the lens. Just before reaching the lens the fibers sepa- rate, part going to the anterior portion of the edge and part to the posterior portion of the edge. In this way a small triangular space is left surrounding the lens and bounded by the two portions of the suspensory ligament. This space has been called the canal of Petit. THE AQUEOUS HUMOR. The aqueous humor consists of a clear fluid in which a few leukocytes may be found. THE EYELIDS. 193 THE VITREOUS HUMOR. The vitreous humor consists of a very loose net- work of dehcate fibrils and branching cells, the meshes of which are greatly dilated by the clear jelly-like vit- reous substance. It is surrounded by a slightly denser membrane of fibrous tissue which, anteriorly, is con- tinuous with the suspensory ligament, and is called the hyaloid membrane. Occasional leukocytes are also found both in the hyaloid membrane and in the body of the vitreous. THE EYELIDS. The eyelids consist of five layers — the skin, mus- cular layer, median connective tissue, tarsal plate, and conjunctiva. The skin, with its subcutaneous tissue, has the same structure as elsewhere, being, however, quite thin. The muscular layer consists of irregular bundles of voluntary muscle-fibers from the orbicularis palpebra- rum. The median connective=tissue layer consists of fibrous tissue, containing occasional smooth muscle fas- ciculse. The tarsal plate consists of fibrous tissue much denser than the latter, embedded in which lie a number of long, compound tubular glands (the Meibomian glands), which secrete a fatty substance just internal to the eye- lashes. The conjunctiva covers the inner surface of the eye- lid, and is reflected over upon the eyeball at a point near the corneoscleral junction. It is composed of a basement membrane covered by epithelium, which at the inner surface of the lid is stratified, columnar, and continuous with that of the skin. Near its junction 13 194 THE EYE. with the sclera the cells become flattened and continue over the cornea as the anterior epithelium. THE LACRIMAL GLANDS. The lacrimal glands are small racemose glands of the serous tyjte, which are situated at the upper outer angle of the orbit. Their secretion is poured upon the surface of the conjunctiva by a number of small canals. QUESTIONS FOR CHAPTER XIV. 295. Name the cliamhers of the eye. What separates them ? 296. Give the boundaries of the anterior chamber ; of the po.s- terior chamber. 297. Describe the gross structure of the retina, of the choroid, of the sclera, of the lens, and of the cornea. 298. Name the layers of the cornea. Describe each separately. 299. Describe the lymphatic and nerve supply of the cornea. 300. Name the three parts of the retina. 301. Name the ten layers of the retina in their order. 302. Describe each layer of the retina. 303. What are the radiating fibers of Miiller ? 304. Describe the macula lutea. 30.5. Describe the fovea centralis. 306. Describe the ora serrata. 307. Describe the blood supply of the retina. 308. Name the four coats of the choroid. Describe each sepa- rately. 309. Describe the nerve, lymphatic, and blood supply. 310. Name the three laj'ers of the sclera. Describe each. 311. A^Tiat is the ciliary body ? Describe its structure. 312. What is the canal of Sehlemm ? Give its location. 313. ^Miat is the nerve and blood supply ? 314. Name the five layers of the iris. Describe each. 31.5. Give the general structure of the lens. 316. "SMiat are the lens stars ? QUESTIONS. 1!I5 317. Describe the suspcnsoiy ligaments. 318. Describe the aiiiieoiis humor. Md. Describe the \itreous humor. 320. Name the layers of eyelids and describe each. 321. Describe the lacrimal glands. CHAPTER XV. THE EAR. The ear may be divided into three jjortions — the external ear, the middle ear, and the internal ear. The external ear consists of the pinna, or auricle, and the auditory canal. The pMWK(, or (luricle, consists of a basis of yellow elastic cartilage, which is covered by the skin and its subcutaneous tissue. In the inner surface are found coiled tubular glands, ^vhicli are modified sweat-glands, and secrete a waxy sulistanee. These are called the ceruminous glamh. The auditory niiKtl is a little over an inch in length, extending inward to the tym])anum. The outer lialf of the canal is comjxised of cartilage continuous with that of the jiinna. The inner half is osseous in structure. The entire canal is lined with a tliin stratified epithelium, containing a few hairs and ceruminous glands near the outer portion of the canal. The middle ear includes the tym])anum, the Eu- stachian tube, the mastoid cells, and the tympanic cavity, with the small ear bones, or ossicles. The tympaiinm consists of three layers. The e.rfcnial kr/rr is a thin, stratified epithelium, continuous with the lining of the auditory canal. The middle lai/er is a thin membrane of white, fibrous tissue. The infernal or mucous layer comiAso? i\ single laver 196 EUSTACHIAN TUBE. 197 of I'lihoid epitlielial e'ell.s, contiiuiou.s witli the lining of llie tympanic rax'ity. Bluud-icaxc/.^, lyiiipIi(iti(:-<, and nerrcs are very nniuer- ons. The Euddcliinii tube consists of three portions. The inner, opening into the tympanic cavity, has bony walls ; the middle portion, yellow, elastic, cartilaginous walls; and the portion opening into the pharynx is tibrous. 1* '''f/.L/^] ^ J) C==^^^ Fig. 95. — Longit.iulinal section of cochlea, showing the relation of the scalae, the ganglion spii-alLe, etc. (after l.Ti'ay): .s. i'., Scal.i vestihnli ; .s'. t.^ scala tynipani ; 5. ?Ji., scala media; /. s., liganientuni spirale; cj,s,, ganglion spirale. The entire tube is lined hy stratified, ciliated, columnar epithelium. The tj/mjxiiila cavit]/ and mastoid celh are lined by their periosteum, upon which is a thin layer of fibrous tissue supporting the epithelium. This and the mas- toiil cells and the promontory are flat, and but a single layer in tliickncss. ( )ver the other portions of the cavity the epithelium is columnar-ciliated. 198 THE EAR. The ossicks have the usual structure of compact hone, being covered at their articulations with hyaline carti- lage. The internal ear, or labyrinth, comprises the vesti- bule, semicircular cauals, the cochlea, and the mem- branous labyrinth. The vestibule and xciiucircalui- caiiah are lined by a F], blood-vessels. very thin fibroserous membrane, which secretes a thin fluid — the perilymph. The perilymph fills the space between the walls and the membranous labyrinth. THE COCHLEA. 199 The membranous lahi/iiidh lias three portions — tlie saccule, the utricle, and that portion in the scniicii'ciilar canals. All, however, have a similar structure consisting of three layei's. The outer is of fibro-elastie tissue, the middle layer a delicate basement menihranc, and the inner a single layer of squamous epithelium. At certain areas marking the entrance of the auditory nerve-fibers the membrane is much thickened, the epi- thelium covering these areas becoming columnar, until at the end of the nerve-fibers the neuro-epitli(>lium is reached. These spots are called the maculae cribroste in the saccules and utricles, and the ci'istas acusticte in the semicircular canals. The neuro-epithelium is of two kinds — fiber cells and hair cells. The jiber cdlx are long, slightly hourglass-shajoed elements, the bottom expansion being slightly larger than the upper. They have good-sized oval nuclei situated in the lower portion. These cells serve as supporting elements. The hair cells are more cylindric elements, situated between the fiber cells. They have a large spheric nucleus, and their free surface is covered by long, deli- cate filaments, called the auditory Iiairs. The hair cells are the special endings of the auditory nerve. Upon the surface of the hair cells a gelatinous sub- stance is spread, in which are embedded numerous slightly elongated crystals of calcium carbonate, called the otoliths, or ear stories. The center of the membranous labyrinth is filled with a clear fluid, which is called the endolymph. THE COCHLEA, The cochlea consists of a small tube coiled spirally two and a half times around a central pillar (the modiolus). 200 THE EAE. The modiolus contains the fibers of the cochlear brandies of the auditory nerve-fibers from which they pass into tlic spiral tube. The spiral tube contains a long spiral lamina, which extends as a shelf from the modiolus to its center. From the free edge of this bony lamina a triangular duct (the membranous cochlea or ductus cochlearis) extends, its base being attached to the periphery of the bony tube. This arrangement constitutes virtually three tubes ; that above the bony lamina is called the scdla vestibuli, that within the ductus cochlearis is called the scala media, that below is called the sealatympani The membrane forming the boundary between the seala vestibuli and the scala media is called the mem- brane of Reissner, or memhruna vestibularh. That be- tween the scala tympani and the scala media has received the name of the membranous spiral lamina. The scalas vestibuli and the tympani are lined by the periosteum, which is considerably thickened at the periphery or point of attachment of the ductus coch- learis, and is called in this location the ligamentum spirale. The membrane of Reissner consists of three layers : that bounding the scala is of epithelium ; the middle layer is of thin fibrous tissue ; that layer lining the scala media is a single layer of squamous epithelium. The membranous spiral lamina also has three layers — the tympanic lamella, the basilar membrane, and the epithelium. The tympanic lamella forms part of the lining of the scala tympani, and consists of a dense layer of fibrous tissue, the outer surface of which is covered by fusiform cells of undeveloped mesoblastic nature. The basilar membrane forms the supporting por- THE COCHLEA. 201 tion of the membranous spiral lamina, and is composed of fibrous tissue. The epithelium covering the peripheral portion of the spiral lam'ina is flat and slightly granular. These cells are termed the cells of Claudius, and the area covered by tlieni the zona pectinata. ^Vt the inner portion the cells become greatly special- ized and form a mass called the organ of L brti, the area covered by it being known as the zona tecta. Fiff. 97.— Section of Corti's organ from guinea-pig's cochlea (after Piersol); iS* T, Scala tympani ; TO, tunnel of Corti; a, bony tissue or spiral lamina; b, b, fibrous tissue covering same continued as substantia propria of basilar membrane; c, c, protoplasmic envelope of Corti's pillars (e, e) ; d, endotlielial plates ; /, heads of pillars containing oval areas; g, head plates of pillars ; />, h', inner and outer hair-cells; m, membrana reticularis; k, I, cells of Hensen and Claudius; «, n, nerve-fibers; i, cells of Betters. The organ of Corti consists of numerous arches of epithelial cells, joined side by side to form a long tun- nel, which extends nearly the whole length of the cochlea. Several types of epithelial cells contribute to the formation of the organ. On either side of the arch proper, and really forming '•^02 THE EAR. part of it, are the p7/rt,r cells. These are tall, narrow cells with expanded bases, and, according to their position, are known as outer or inner pillar cells. The inner cells are somewhat the shorter of the two and have a concave upper outer surface, into which the convex adjoining surface of the outer cell fits. The tunnel thus formed contains a clear, thick fluid, through which many nerve-fibers pass. Just internal to the inner pillar cells is a row of shorter, tailed columnar cells (one cell wide in each arch). These cells have a number of hair-like pro- jections on their free end, and are called the inner hair cells. Still internal to these are a numter of columnar cells which serve as inner sustentacular cells. External to the outer pillar cells three or four rows of hair cells occur, wdiich resemble the inner hair cells, but are called the outer hair cells. Situated below these cells, and sending up slender prolonged ends separating the outer hair cells from each other, are a few fusiform cells, called the cells of Deiters. Between these cells spaces frequently occur which communicate with the tunnel and contain a clear fluid, and are ca,lled Nuel's spaces. External to the cells of Deiters are a few cells in- termediate in size, which gradually merge with the cells of Claudius, and which are called the cells of Hensen. The nerves branch continually from the modiolus, fibers passing into the ganglion spiralae which are sit- uated just within the bony spiral lamina. From this the fibers pass to the inner hair cells, and thence across the tunnel to the outer hair cells. The blood supply of the cochlea consists of a number of branches from the cochlear branch of the auditory QUESTIONS. 203 artery. Sonio of these brancli(^s supply the lower por- tion of the eoelilea, the rest passinV up the modiolus, where some of them coil up to form the (/lomendl cochlai' ; others proceed to tlie membrane of Keissner. Branches from the glomeruli pass into the membranous spiral lamina. The fluid in thr> perilymph-spaces of the entire inner ear intercommunicate, and are also in connection with subarachnoid lymph-spaces. The endolymph-spaces likewise communicate with each other and with subdu- ral spaces. QUESTIONS FOE CHAPTER XV. 32'2. Name the tlii-ce portions of the ear. 323. Describe tlie structure of the auricle ; the auditory canal. 3-24. What is included in the middle ear ? :;2."). Describe the three lujers of tympanum. :!:2li. Describe the Eustachian tube. :!27. Describe the structure of the tvinpanic cavity and the mas- toid cells. 32><. Describe the structure of the ossicles. 329. What structures comprise the internal ear ? 330. Describe the structure of the vestibule and the semicircular canal. 331. Describe the structure of the membranous labjTinth. 3.'!2. What is the perilymph ? 333. What is the neuro-epithelium, the fiber cells, and the hair cells ? 334. What are the auditory hairs ? the otoliths ? 335. Of what does the cochlea consist ? "\ATiat is the membranous cochlea ? 336. What is the soala vestibuli ? the scala media? 337. ^VTiat is the membrane of Reissner ? Describe it. 33S. What is the membranous spiral lamina? Describe it. 339. What is the organ of Corti ? Describe it. 340. What are the cells of Deiters? 204 THE EAR. 341. Describe the nerve di.stribution of the internal ear. :J42. What are the ganglion spiralie '! 343. Describe the blood siip])ly of the internal ear. "\\ hat are the glomeruli cochlea!? 344. Describe the lyniijli supply of the internal ear. CHAPTER XVI. THE NASAL MUCOUS MEMBRANE. The nasal membrane is divided into two parts — the respiratory and the olfactory tracts. The respiratory mucous membrane is lined witli stratified columnar, ciliated, epithelial cells, under which is a well-marked submucosa of loose fibrous tis- sue containing many glands and blood-vessels. The glauds are tubular, and may be either serous or mucous in character. !Many leukocytes are found surrounding the glands and scattered through the fibrous tissue, as wt'll as occasionally invading the epithelial covering. Small lymph-nodes, or follicles, are seen quite fi'e- quently, as well as small, scattered masses of diffuse adenoid tissue. Tlie olfactory mucous membrane differs from the respiratory in color, being brownish and circumscribed, tlie color limit not, however, exactly marking the ex- tent of the olfactory cells, Avhich may continue into the apparently red of the respiratory membrane. It consists of two layers — the epithelial tissue and the subepithelial tissue. The epithelial tissue is stratified in character and contains three types of cell : The miMent(ietil L-shaped pieces of metal arranged so as to form a square, and the square so formed filled with molten paraffin. The paraffin is allowed to cool for a moment until a thin skin forms over the top, when the whole thing is plunged into cold water in order to solidify the mass as quickly as possible. When thoroughly cold, the block of paraffin containing the tissue at the lower end is sepa- rated from its metal casing and carefully dried. Then the block is cut away from the sides of the specimen, PARAFFIN E.MBEDDINO. 243 k'living a margin of only about 1 mm. of paraffin around each sido, hut being careful that the opposite outer edges of the niargiu are parallel. The block is now clamped in the microtome \vith the longest diameter of tlie specimen transversely to the path of the knife. The knife must be so placed that its edge is at right angles to its path and that it will pass squarely through the specimen, and not obliquely, as is the case in cutting celloidin. The sections are cut with the knife dry, and may be removed one at a time as they are cut or allowed to adhere, the front edge of one to the hind edge of the preceding, as they are cut, s(.) as t(j form a " ribbon." Only as many sections should be cut as -will be needed at once, as the embedded block will keep indefinitely and can always be cut from at any subsequent time. If the tissue is tough and the sections are not too thin, they may be placed at once in xylol or turpentine, to dissolve out the paraffin, and thence in absolute alco- hol if they are to be stained ; or if already stained in bulk, they may be mounted in Canada balsam. If the sections are fragile, they must be mounted on glass slides. The slides having been thoroughly cleaned, a very thin layer of Mayer's albumin is spread upon one side, either with a camel' s-hair brush or with the fingers, and allowed to dry. The Mayer's albumin is made by mixing — White of egg . . ... 50 c.o. Glycerin 50 " Sodium salicylate ... . . 1 j^ia. shaking very thoroughly with a few pieces of broken glass (to hasten the solution of the egg), and filtering through coarse filter-papei'. This filtration may require weeks, but the resulting solution, if tightly stoppered, will keep good for a year or more. As soon as the 244 TECHNIC. sections are cut, they are picked up with a needle or brush or fine forceps and carefully floated upon warm water (40° C), when they will at once flatten out and become perfectly smooth. The edge of one of the albuminized slides is carefully dipped into the water and the section carefully floated uj) into place by means of a needle. The slide is removed, the excess of water drained off", and the slide placed on top of the oven or in an incubator (37° C.) for several hours, or the slide and sections may be allowed to dry and may then be im- mersed in equal parts of alcohol and ether for an hour, which will coagulate the albumin and fix the section fast to the slide. The slide is now immersed in xylol, tur- pentine, or benzol for a few minutes to dissolve off" the paraffin. After this it is placed in absolute alcohol, after which it may be stained in whatever way desired. FREEZING. This is a very rapid method of preparing sections. The tissues may either have been fixed or may be per- fectly fresh. If fresh, they had best be fixed for an hour or so in 10 'fo of formalin in water. If they have already been fixed, they should be placed for an hour or more in water, in order to extract the alcohol, which would greatly retard the freezing. They are next placed in a thin solution of cane-sugar and gum arable (2 gm. to 100 c.c.) in water, to which a small piece of camphor or thymol has been added to prevent the growth of mold, and allowed to remain for three or four hours. While a little more troublesome to make, the follow- ing solution has several advantages over the plain gum and sugar : FREEZING. 245 Two stock solutions are made and kept on hand. (a) Cane-sugar 2!^.:) giu. Water 30 c.c. Boil, and while hot saturate with boracic acid ; cool and filter. Gum acacia . . 45.6 gm. Water icold) . . 2400 c.e. When dissolved, add boracic acid to saturation by boil- ing ; cool and filter. For use : Solution a 4 parts. Solution b 5 " Water .... . 9 " Boil, and saturate with boracic acid ; cool and filter through muslin. Tissues may be kept fov an indefinite time in this solution, and be ready to cut immediately. The pieces of tissue are then removed, placed upon the drum of the freezing microtome, a small quantity of gum solution added, and the ether spray or liquefied carbon dioxide turned on gradually until the whole mass begins to congeal. As soon as it becomes solid and of a dull luster, and before it turns hard and white, the sections should be rapidly cut, with the knife-edge at right angles to the direction of movement. If the specimen chance to have been frozen too hard, it should be allowed to soften slightly for a moment before cutting the section, as if this is not done the sections may be imperfect and the knife-edge damaged. As soon as the sections are cut they should be placed in water, in order to expand as well as to dissolve out the gum. They may subsequently be stained by any one of the various methods. 246 TECHNIC. STAINING. Thin sections of tissue being very transparent and often highly and evenly refractive to light, it becomes advantageous to stain them, so as to produce a stronger and more easily studied image. Again, as different elements of tissue and cells are of varying chemic composition, they are found to be differently affected by various stains, so that by a suitable selection of stains contrast effects may be produced which aid very ma- terially in distinguishing and studying closely associ- ated details. The number of methods of staining tissues which have been suggested and used is enor- mous. At present only one or two of the simpler but most generally useful can be given. Osmic acid (osmium tetroxide) is a very useful stain for studying the distribution of fat and myelin, as it has the property of being reduced by these substances and coloring them black or dark olive green, whereas the other tissues are stained but slightly. Teased fresh material or sections made with the freezing microtome give the best results, although tissue hardened in formalin or MuUer's iluid may be stained in this way. As the vapors of osmic acid are extremely irritating to the eyes and res23iratory tract, care should be exercised in making and handling the solution. A 1 fc solution in distilled water Avill give good re- sults and may be taken as a fair average strength, although it is frequently used in strengths varying from .25;% to 2^. The substance occurs in commerce sealed in glass tubes which can be easily broken by first cutting with a file, then breaking the end off with the fingers and dropping tube and all into a bottle contain- ing the amount of distilled water neeessar}- to insure the desired strength of solution. STAINING. 247 Only distilled watei- should be used as the acid blackens organii^ matter in time and suffers decomposi- tion. The solution should be j^ept in dark bottles and away from the liglit. Stained material or sections ma}- be preserved in 95^ alcohol or may be mounted in glycerin or chloro- form balsam. The ordinary xylol balsam soon bleaches osmic acid preparations, hence should not be used. Sudan III is a specific stain for fat, and gives its best results when used on fresh sections made either by the freezing microtome, unfixed or fixed in formalin, or in sections made from fresh tissue by the double or Valentine's knife. The stain may be prepared by saturating 80 ^ alco- hol with the dye. Sections sliould be stained for half an hour, rinsed in 50^ alcohol, tiien in water, from which they may be mounted in glj'ccrin or Farrant's solution, or they may first be counterstained in hema- toxylin. This stain cannot be used in specimens wliich have been treated witli strong alcohol or ether, as both these substances extract tlie fat. In properly stained sections the fat globules or fat cells stain a briglit deep orange, the tissues a dull yellow or scarcely at all. Borax carmin is one of the most reliable and most easily handled of the stains. Grenacher's formula is as follows : Carmin (No. 40) ... . 1.25 gm. Borax . 2 " Water 50 " Alcohol (70%) 50 " The borax, carmin, and hot water are rubbed thor- oughly ill a mortar and allowed to cool. The alcohol is then added, and the whole allowed to stand for two or three weeks, and then filtered. This preparation is 248 TECHNIC. the 8tain licst adapted to bulk xfaiiiiiu/, for wliich jiur- pose the previously fixed and hardened pieces of tissue are immersed for three days. From this they are transferred directly into — Hydrochloric acid (lU;t) .... 4 c.c. Alcohol (70;/^) 100 " where they should remain for forty-eight hours. ^V hen removed, the specimens should be of a bright, deep-red color. They are next placed in 85 fo, 95 '/e, and abso- lute alcohol for twenty-four hours each, after wiiich they are ready for the solution immediately preceding the infiltration and embedding. If sections are to be stained, they should be placed in the fluid for half an hour, then in — Hydrochloric acid (pure) .... 5 c.c. Alcohol (70%) . . . . 100 " for from five to ten minutes, from which they should go into absolute alcohol and then into the clearing mixture. The borax carmin stains all parts of tiie tissue almost equally of a dull-red color, which would readily wash out. When, however, it is treated with the dilute HCl, the excess of stain is dissolved out, the nuclei remain more deeply stained than the rest of the tissue, and the stain is fixed permanently. A pleasing contrast staining results if a few crystals of picric acid are dissolved in the alcohol and used after the stain as well as in the final clearing medium. In tliis case the nuclei will remain a deep-red, whereas the cell-bodies and intercellular substances will assume a briglit canary yellow. Lithium carmin stains somewhat more rapidly and brilliantly than the foregoing and gives extremely pleas- ing pictures as a contrast stain in tissues which have had the blood-vessels injected with Berlin blue. It STAINING. 249 keeps very avoU and is simiile to prepare. Its formula is — Carmine 3 gm. Lithium carbonate (sat. aq. sol.) 100 c.c. Dissolve by shaking; warm .slightty if necessary. Sections should be stained five minutes and then transferred without rinsing to — Hydrochloric acid . . . 1 c.c. Alcohol (70%) 99 " until they assume a bright pink color, when they are dehydrated and mounted as usual. This stain does not give good results for staining tissues in bulk. Mayer's paracarmin is made as follows : Carmimic acid 1 urn. Aluminum chlorid 0.5" Calcium chlorid 4 " Alcohol (70 %) 100 c.c. Dis.solve, warming if ucce.-^sarv ; cool and filter. This .solution stains splendidly in bulk, and will pene- trate even better than borax carmin ; hence it can be used for large specimens. Sections slain in a few minutes, and need only be rinsed in 70 'fo alcoliol before being dehydrated, cleared, and mounted. For bulk staining the specimen should remain in the stain from one to ten days, according to its size and permeabilitv, when it can be wa.shed in 70^, alcohol, dehydrated and imbedded. Paracarmin rarely overstains either tissues or .sections ; but if such a condition should occur, the e.vcess may be remo\'ed l)y adding 0.5^ aluminum chlorid or 2.5 fo glacial acetic acid to the 70 ^ alcohol when wasiiing the specimens. Care should be taken not to place objects iu the stain which ha\e an alkaline reaction. Any other failure with this stain can usually be traced to a poor quality of carminic acid. 250 TECHNIO. Hematoxylin is of equal value and as extensively used. Delafield's formula, while being a trifle more complex than some others, is still the most satisfactory : Hematoxylin ... . 4 gm. Alcohol (absolute) .... 25 c,o. Dissolve aiul add Ammonia alum . . 52 gm. Water . . . 400 c.o. Allow the mixture to stand in the light for a week and then add Glycerin ... . 100 c.c. Methyl alcohol . . 100 " The whole mixture should be kept in the sunlight as much as possible for t\\ o weeks longer, when it is ready for use ; it will usually keep well for a year. If it becomes too strong aud stains too rapidly, small quan- tities may be diluted to any requisite amouut with dis- tilled \vater. For bulk staining the stain is diluted until it is quite transparent, and pieces of fixed tissue arc immersed in it until they become dark blue. As the stain varies very much in power from time to time, no definite length of time can be given. Ordinarily, however, the stain should be diluted until of such strength as will stain blocks well in twenty-four hours. Care should be taken to avoid overstaiuing, but a trial or two will suffice to determine the dilution necessary. From the hematoxylin solution the tissues should be placed in an abundance of water, where they should remain with occasional agitation for forty-eight hours. From this they are transferred to increasing strengths of alcohol until absolute, embedded, and cut. Sections are placed in the solution for from three to fifteen minutes, according to the strength of the stain ; STAINING. 251 washed well in water from three to five minutes, then in 95 fo alcohol, then absolute alcohol, and next in the clearing' medium. Mayer's hemalum can be used at once, and stains quite well in bulk, but does not keep so well as Dela- field's hematoxylin. Hematein . . .1 gm. Alcohol (9.5 % ) .50 c.c. Dissolve by heating. {l)\ Alum ... 50 gra. ^ ' Water WOO (J.c. Pour a into h ; filter, and add a ciystal or two of thymol to prevent the growth of moulds. Sections after staining should be washed in distilled water, and may be counterstained. For bulk staining the solution should l)e diluted with distilled watei' and the tissue immersed tor twenty-four hours or nxire and washed in distilled water. It does not overstain. Acid hematoxylin is likewise an excellent stain and keeps well. Kulschitsky's formula is as follows : Hematoxylin (crj'stals) 1 gm. Alcohol (absolute) . . 20 c.c. Dissolve and add Acetic acid (2 %) . 100 c.c. Sections should be st.iined in this fluid for from five to fifteen minutes, ^^■ashed in water, and placed in a satu- rated solution of lithium carbonate until they assume a fine deep blue color, when they may be dehydrated, cleared, and mounted or counterstained with eosin. Logwood and eosin staining, when combined, make one of the most pleasing combinations of stains. By this method nuclei are stained deep blue, while the cell-bodies and intercellular substances become a fine 252 TECHNIC. pink to red, according to the depth of the eosin stain- ing. At the same time red blood-corpuscles assume a, characteristic coppery-red tinge, \vhich makes them very easily recognized. After the specimen has been stained in tlie hematoxylin (by either of the above methods) and washed in water, it is placed for two minutes in — Eosin (yellowish) 0.5 gm. Alcohol (70^) . . 100 c.c. after which it is dehydrated, cleared, and mounted. Van Gieson's stain (picro-acid-fuchsin) may be sub- stituted for eosin with advantage in the study of fibrous or nerve tissue. After staining the section in hema- toxylin and rinsing in water stain it for five minutes in — Acid f uohsin {1% aqueous sol.) . 10 c.c. Picric acid (sat. aq. sol.) . . . 90 " Dehydrate in alcohol containing a few crystals of picric acid to prevent extracting too much of the yellow stain. If creasote is used for clearing, a few crystals of pic- ric acid may also be added to it. As this stain tends to decolorize the hematoxylin and render it brownish instead of blue, sections should be first slightly over- stained with the hematoxylin. This method stains connective tissue red, elastic tis- sue and muscle yellow ; nuclei and epithelium are stained brown. Thin sections of tissues fixed in alco- hol or mercuric chlorid give better results than thick sections or chromic acid fixatives. Orcein is employed to demonstrate elastic tissue and may be used after any of the fixatives. Tissues may also be stained in bulk by this method. Sections should stain in the orcein solution for five or six hours and then be washed in 95 ^ alcohol, cleared, and mounted. For STAINING. 253 bulk staining thin pieces should be stained for twenty- four hours or more and be placed for about half an hour in acid alcohol, taking care, however, not to allow them to remain long or they will become decolor- ized. Dehydrate in absolute alcohol and imbed and cut sections as usual. The elastic fibers should be stained a reddish brown and the rest of the tissue but slightly stained. The stain is prepared by mixing — Orcein 1 gm. Absolute alcohol lOU c.c. Hydrochloric acid . 1 " Resorcin-fuchsin, or Weigert's stain, is also used for demonstrating elastic tissue and, while more trouble- some to prepare, gives results more certain and superior to orcein. To prepare the stain boil — Basic fuohsiu .... . 1 gm. Resorcin . . . . 2 " Water 200 c.c. in an evaporating dish. When boiling add 25 c.c. of liquor ferri chloridi and continue to boil and stir for about five minutes. This produces a blackish precipi- tate which should be separated upon cooling 1)y filtering. Drain off the excess of fluid and dissolve the precipitate in 200 c.c. of 95 ^ alcohol, throwing in filter-paper and all to avoid loss of precipitate. When dissolved remove the old filter-paper and add 4 c.c. of hydro- chloric acid. Sections should be stained for an hour and then rinsed in two or three changes of 95 ^, then absolute alcohol, cleared, and mounted. Xylol is the best clearing agent, as it does not extract the stain. The elastic fibers will appear as deep steel blue upon a clear field. Sections may be stained either before or 254 TECHNIO. after this method with carmine, which produces a very pleasing contrast. Dahlia is used in several modifications for staining mast cells. One of the simj^lest and most satisfactory is known as Westphal's alum-carmine dahlia, which is made by dissolving — Dahlia 1 gm. Alcohol (absolute) 25 c.c. Glycerin 12 " Glacial acetic acid 5 " When dissolved add an equal volume of alum carmine. The best results are obtained with tissue which has been fixed in alcohol for about ten days. Sections should be stained for twenty-four hours and then dehydrated in several changes of absolute alcohol for twenty-four houi's more, when they may be cleared in xylol and mounted. The nuclei will be reddish and the granules of the mast-cells present will be stained a deep blue. DEHYDRATION OF SECTIONS. All sections which are to be finally mounted in Canada balsam must, after staining, be dehydrated. If this is not thoroughly accomplished, any trace of moisture remaining will precipitate the balsam, pro- ducing a cloudy mount. If some one of the clearing agents is used, such as clove oil or creasote, 95 ^ alco- hol may be used to dehydrate the specimen, otherwise absolute alcohol must be used. CLEARING. After the specimens have been stained and dehydrated they are subjected to the action of a clearing agent, the purpose of which is to remove the alcohol used in de- M(IUNTIN(;. 255 hvdrating, to iviider tlie spociineu trans])arent, to act as a prt'servative, and to afford a substance whicli will be readily miscible with the Canada balsam. Of these clearing agents there arc many : Xylol, turpentine, creasote, clove oil, cedar oil, oil of berga- mot, and, in fact, nearly all the essential oils may be used. Of these, creasote (which must be the best German beechwood variety) is mo^t satisfactory for ccUoidin sections, as the celloidin is not attacked by it as it would be by clove oil. Creasote also clears well from 95 fc alcohol. Xylol, either pure or with the addition of half its weight of crystallized carbolic acid, makes an excellent clearing agent for paraffin sections, but requires very thorough dehydration. Oil of cloves is reliable and has the quality of dis- solving celloidin, which may be either desirable or not according to the case in hand. MOUNTING. If the sections are unattached to the slide, they should be lifted from the clearing agent by means of a section-lifter, which is gently slid under the section and lifted out of the fluid, the section meanwhile being held in place by means of a needle. The section is then gently slid off the lifter on to the center of a clean glass slide and the excess of clearing agent carefully I'emoved by means of a clean piece of filter-paper. A drop of Canada balsam is placed on the center of the section and covered by a cover-glass, care being taken that just enough balsam is used to fill all the space between the cover-glass and slide, and at the same time to avoid air- bubbles. The paper-filtered balsam, which comes in 256 TECHNIC. collapsible tubes, or xylol balsam will be found to be the best agents for mounting specimens. The slide should be labelled at once, and may be examined or put away in a horizontal position for a few days, by which time the balsam will be quite well set, so as to retain the cover-glass in positi(ju. Chloroform balsam may be used in place of xylol balsam, but is used especially to mount preparations stained with osmic acid, as it does not decolorize them. It may be jjurchased in bulk or in collapsible tubes or may be made as follows : Evaporate commercial Canada balsam over a water- bath or by gentle heat until it is reduced to about half its original bulk or until it becomes brittle upon being cooled. Then pour it out upon an iron plate to cool. Break it up into small pieces and dissolve in chloroform to the consistency of thick syrup and preserve in tightly stoppered bottles. Damar ma}- be used in the place of Canada balsam. It has tlic property of not rendering the sjjc'ciniens quite SI) transparent, which in some cases will show more detail and is advantageous. It is used in the same manner as the balsam, and can bo bought ready pre- pared ; or it may be made by dissolving the gum in etpial parts of benzine and oil of turpentine until a thick consistency is reached. Farrant's solution also maizes a convenient mount- ing medium for specimens which have not been dehy- drated, as blood-cells fixed in Hayem's solution, or sec- tions stained in pierocarmiu before they are placed in the final alcohol and clearing bath. Glycerin 50 c.c. Water 50 " Gum araliic 50 gm. Arsenous acid 1 " MOUNTING. 257 Dissolve the arsenoiis acid in tlie water, tlaen add the gum, and allow it to stand for several days. Next add the glycerin ; mix thoroughly, and filter tlirough cloth. It is used in the same manner as balsam, but only with objects ^^'hich have previously been in water or an aqueous solution. Glycerin jelly is convenient for mounting blood- corpuscles which have been fixed and stained in bulk, as it enables the corpuscles to be seen and studied in various positions. It may also be used for sealing cover-glasses or holding them in position and prevent- ing evaporation when glycerin or other fluid medium is being used under the cover-glass, as it becomes firm upon cooling, and when warmed may be applied with a small brush. It is made as follows : Gelatin 20 gm. Glycerin 30 c.c. Spts. camphor 1 " Soak the gelatin in cold water for an hour and press out the superfluous water. Add the glycerin and warm upon a water-bath until dissolved, then add the camphor, and filter. An equal quantity of 1-1000 mercuric chlorid may be substituted for the camphor, as the function of either is simply preservation. TabtjIjAB Scheme of Pebpabation of Tissue to be Stained IN Bulk. 1. Fix in one of the fixing solutions. 2. "Wash in water, according to fixative used. Borax Carmin. HemaioxjiUn. 3. Borax carmin . 3 daj'S. 3. Delafield's hema- toxylin . 24 hours. 4. Acid alcohol . 2 " 4. Water . . 48 " 17 258 TECHNIC. Borax Carmin. 5. Alcohol (S5%) . . 24 hours. 6. Alcohol (95%) . 48 " 7. Alcohol (absolute) 48 " If Emliedded in Paraffin. a 1. Xylol, turpentine, or chlo- roform until translucent — one to twelve hours. If chloroform is used, ■ next to saturated solu- tion of paraffin in chloro- form twelve hours. a 2. Melted paraffin, two to eight hours. Cast block. Cut sections. Fix to slide -with Mayer's albumin. Dissolve off paraffin, and clear with xylol. Mount with drop of Canada balsam. a 3. a A. a b. a 7. Hemaioxylin. .5. Alcohol (70??.) .24 hours. 6 Alcohol (H5 5;) .24 " 7. Alcohol (95%) . . 24 " 8. Alcohol (absolute) 24 " If Embedded in Celloidin. a 1. Alcohol and ether . . 24 to 48 hours. a 2. Thin celloidin .24 " a 3. Thick celloidin 48 " a 4. Block, and allow to set. a 5. Chloroform or 85 % alcohol . 24 hours. a 6. Cut section. a 7. Place sections in absolute alcohol two minutes. a 8. Creasote, or other fixa- tive, three minutes. a 9. Place on slide with sec- tion-lifter and remove excess of solution. a 10. Drop of Canada balsam and cover-glass. Scheme of Pkepaeation" op Tissue.^ by Pabapfin Method, TO BE Stained in Sections. 1. Fix and wash if fixative requires it. 2. Dehydrate. 3. Xylol, turpentine, chloroform, or alcohol and cedar oil until translucent, one to twelve hours. 4. If chloroform has been chosen, into saturated solution of paraffin in chloroform. If alcohol and cedar oil, into pure cedar oil, for twelve hom-s in either case. 5. Into melted (50° C.) paraffin at 51° C. to 52° C. for from two to eight hours. 6. Cast, block, and trim it. 7. Cut sections and float out on warm (40° C. ) water. 8. Fix sections to slide with Mayer's albumin and dry thoroughly for several hours on top of oven or in incubator at 37° C. Slides may be stored away and kept indefinitely at this stage. When wanted for use, proceed with : 9. Place slides in xylol, turpentine, or benzol, to dissolve ofi paraffin completely. Place slides in absolute alcohol for five minutes, from which they can enter alcoholic stains. "\Mien aqueous stains are to be used, they are best placed for a minute in 85 % alcohol first. 10, MOUNTING. 259 Scheme of Peepakation of Tissues by Celloidin Method, TO BE StAIN'ED in SECTIONS. 1. Fix and wash if fixative requires it. 2. Dehydrate. 3. Alcohol and ether, twenty-four to forty-eight hours. 4. Thin celloidin, twenty-tour hours. 5. Thick celloidin, forty-eight hours. 6. Block and allow to set. 7. Place blocks in chloroform or 85 % alcohol for twenty-four hours. 8. Cut sections with knife wet with 85 % alcohol. 9. Sections may be kept indefinitely in 85% alcohol until ready to be stained. Scheme fob Staining Sections with Boeax CABunN. If celloidin sections are used, they may be transferred directly from one solution to the other with needles. If the paraffin sections are fixed to the side, either a few drops of the various solutions may be placed upon the section in the center of the slide or the whole slide may be immersed in a small jar of the solution, taking care to wipe off all excess of solution each time a change is made, in order to avoid contaminating the succeeding solutions. 1. Sections in borax carmin, half-hour. 2. Five per cent. HCl in 70 % alcohol, from five to fifteen minutes, or until they become bright and light red. 3. Pure alcohol, which may contain a few crystals of picric acid, three minutes. 4. Xylol, creasote, or oil of cloves, which may also contain a little picric acid, three minutes. 5. Canada balsam and cover-glass. Scheme foe Staining Sections with Delafield's Hematoxylin and Eosin. 1. Section into Delafield's hematoxylin, from three to fifteen minutes. 2. Water, from three to five minutes. 3. One-half of 1^ solution of eosin in 70% alcohol, two minutes. 4. Absolute alcohol, three minutes. 5. Creasote, xylol, or clove oil, three minutes. 6. Mount in Canada balsam and cover-glass. 2fi0 TECHNIC. Scheme for Stainiko Sections in" Acid Hematoxylin. 1. Seetinn in Kulschitsky's hematoxylin, from five to fifteen minutes. 2. Rinse in water one minnte. 3. Saturated aqueous solution of lithium carbonate until it becomes clear deep blue. 4. Absolute alcohol, three minutes. 5. Creasiite, xylol, or clove oil, three minutes. 6. Mount in Canada balsam and cover-glass. BLOOD EXAMINATION. Fresh specimens of blood may be examioed by simply placi no; a drop of blood od a slide and immedi- ately coverinjj; it -with a cover-glass. The slide and cover should be perfectly clean, in order that tlie drop may diffuse evenly between them. A .^-inch objective is all that will be required to show the general cliarac- teristics of the red cells, the formation of rouleaux, etc., but for the demoustration of the granules in the leuko- c^}'tes and to well observe the ameboid movement a yL- inch oil-immersion lens will be required. If it is desired to prolong the observation, it is well to seal up the mount by painting around tlie edge Avith melted j)araffin, which will prevent evaporation. The action of various reagents upon the cells may be Avatched bv allowing a drop of the solution to diffuse slowly under the cover-glass from one corner, care being taken that none of the fluid is allo\\-cd to floAV on the upper surface of the cover-glass. Blood-platelets may be examined by placing a drop of a 1 ^ solution of osmic acid on the tip of the finger and ])rickiug the finger through this, so that the blood in csca])ing shall flow directly into and mix with the acid. In this way the ])]atclets are immediately fixed, and can then be examined tmder a cowr-ghiss at lei.sure. Fixed fluid preparations can be mcU made by BL(X)D EXAMINATION. 201 allowiuo; the hlood to drop directly into Hayem's solu- tion I'oiitained in a conical beaker. In twenty-four hours the red cells will l)e well fixed and will have scltled to the hottoni of the vessel. The fixing solution is now cart'fully poured off" and water added, when the whole .should he thorouuhly stirred in oi'der to wash the cells and rid theui of any trace of the fixing solution. The cells are again allowed to settle, when some of them can he removed with a pipet and placecl in a drop of glycerin on the slide and examined. The I'cd cells ai'c exceedingly well preserved hy this method, but it is not suitable f()r studying tlie white cells. Hayem's solution has the following formula : Sodium chlorid .... . 1 gm. Sortium sulphatu ... . Ti " Mercuric chlorid , . . (I.;! " Water . 20(1 c.c. At least one hundred times as much Hayem's solution as blood must be used. After the cells have been fixed and washed, they may be stained in bulk by adding a little eosin to the water and allowing it to stand for a few hours, again pouring off the stain, adding fresh water, and allo\v'ing to settle. Sections of the red cells may be obtained by ligating a small blood-vessel at both ends and then placing it in a fixing solution, from which it is treated the same as any ordinary tissue to be cut in paraffin. Thin sections should be cut, and may be stained with eosin with or without any of the nuclear stains. Dried and stained films, however, give the most satisfactory pictures as permanent mounts. The spreads are made by taking two perfectly clean cover-glasses, touching the center of one of them to a small drop of blood, and immediately inverting it over the other in such a manner that the drop of blood is spread in a 262 TECHNIC. thin even layer between the two. The covers are then at once .slid apart, taking care that no pressure is exerted upon them, as this would distort or destroy the cells. This will be most easily accomplished if the two covers are placed crosswise so that the corners of one project beyond the edges of the other. The spread should be as thin as p(«sible, so that the cells may l)c well sepa- rated from line another. After the spread lias been made, it should be diied rapidly in air, when it is ready for one of the various methods of fixation. Fixation. — In order to stain well, blood as well as other tissues reijuircs to be fixed. For a study of the red cells an inmiersion of the dried film in alcohol or a mixture of equal parts of ether and alcohol for an hour is all that is required. If the granules of the white cells are to be stained, the best fixative is heat. This is applied by placing the dried films in a small oven which is heated to 120° C (248° F.) for twenty minutes and then allowed to cool gradually. Staining. — -The red cells stain well in a few minutes with the ordinary 0.5 fo solution of eosin in 70 fc alco- hol. The specimen is then well rinsed in watei', dried in air, and mounted with a drop of balsam. If it is desired to show the nuclei of the white cells as well, this staining may be preceded by a few minutes' im- mersion in either of the hematoxylin stains ; or the two stains may be combined, as in the following formula of GoUasch : Eosin (crystaLs) .... 0.5 am. Hematoxylin . . 2 " (rlvwriii Absolute alcohol . . aa 100 CO. Glacial acetic acid . . 10 " Alum slight excess. BLOOD EXAMINATION. 263 After mixing, the sokitiini should he kept in the sun- liglit as much as ])Ossible for a few weeks, wlien it will turn quite dark as it " ripens." When ready for use, it will stain spreads in from five to ten minutes, when the film should be well washed in water, dried in air, and mounted in balsam. If it is not desired to make a permanent preparation, however, the specimen, after rinsing, may be simply inverted upon a slide, the water removed from the upper surface by firmly blotting with a piece of filter-paper, and the specimen at once placed' under the microscope. In case it should dry, another drop of water may be placed under the cover-glass and the examination continued. With the foregoing mixture the red cells will be stained a coppery red, the eosinophile granules of the white cells a bright red, and the nuclei bluish. The different types of white cells are best shown by Ehrlich's neutrophile mixture : Saturated aqueous solutiou, orange G 130 to 135 c.c. Saturated aqueous solution, acid fuchsiu . . . . . 80 to 120 " Saturated aqueous solution, methyl green 125 " Distilled water ... . 300 " Absolute alcohol 200 " Glycerin . . .100 " Mix the orange G., acid fuohsin, water, and alcohol slowly in a bottle, shaking gently, and then add the methyl green and then the glycerin. The mixture should stand for several weeks before heing used. Take the stain for use from the center of the bottle with a pipet, and avoid shaking or disturbing the solu- tion any more than absolutely necessary. To obtain the best results the smears should have been fixed by heat. Cover the spread with a few drops 264 TECHNIC. of the stain, and allow it to remain from three to fifteen minutes, according to the enersiv with which the stain acts ; rinse the film rapidly in water, and examine it at once or allow it to dry thoroughly in air, and then mount in balsam. The red cells will be stained orange to brownish red, the nuclei light bluish, the eosinoj)liiIe granules bright red, the neutro])hilc granules purplish. The eosinophile granules may be intensely stained by cdveriug the film with a saturated solution of eosin in glycerin and allowing it to remain for two hours, then rinsing in water, drying, and mounting in balsam. The basophile granules may be stained liy immer- sion in the following solution for two hours, rinsing in water, drying between filter-pajier, and mounting in balsam : Saturafccil solution of Jalilia in gla- cial acetic acid , I'i 5 c.c. Alisojiite alcohol . . ."id " Distilled water 100 INDEX. Absorptive epithelium, 59 Acid cells, 106 hematoxylin as stain, 251 staining in sections with, scheme for, 260 Acidophiles, 41 Acini of salivary glands, 118 Adenoid tissue, 29 diffuse, 85 Adipose tissue, 28, 29 Adrenal, 224 Agminated folUcles, 109 Alcohol as fixative, 230 Alveolar ducts, 163, 164 glands, 92 Alveoli, 118 of salivary glands, 118 Ameboid movement, 77 Ammonium bichromate as fixa- tive, 231 Amyloid bodies, 134 Appendix vermiformis, 112 Aqueous humor, 178, 192 Arachnoid, 208 Arbor vltse, 216 Areas of Cohnheim, 49 Areolar tissue, 26 ArteriEE rectae, 132, 133 Arterial arcade, 131 Arteries, 69 Arterioles, 132 Artery, helicene, 146 hepatic, 114 interlobular, 114, 131 Auditory canal, 196 Auerbach, plexus of, 114 Auricle, 196 Axis-cylinder, 61 process, 60, 214 Axon, 214 Bartholin's glands, 158 Basement membrane, 58, 93 Basilar membrane, 201 Basket cells, 219 Basophiles, 41, 79 Belhnian tubule, 126, 131 Berlin blue as injection fluid, 237 Bertinian columns, 124 Bile capillaries, 115 Bladder, 134 Blood, 72 cells of, 76 crj'stals, 81 plaques, 79 platelets, 79 supply, 131 of intestines, 113 of stomach, 113 of tongue, 98 Blood-corpuscles, development of, 81 Blood examination, 260 fixation, 262 staining, 262 Blood-vessel, 69 Bodies of Langerhans, 121 Body of epididymis, 139 of Highmore, 138 Bone, 35 265 266 INDEX. Bone, cancellated, 39 compact, 35 development of, 42 intracartilaginous, 42 intramembranous, 45 Haversian systems of, 43 spongy, 39 transverse section of, 2(1 Bone-cells, 39 Bone-corpuscles, 39 Borax carmin as stain, 247 staining in sections with, scheme for, 259 Bowman's capsule, 128 glands, 207 membrane, 179 Bronchi, larger, 162 terminal, 163 Bronchial terminations, dia- gram of, 164 Brunner's glands, 110 Budding, 21 Bundle, anterior ground, 211 Burdach's column, 212 Cajal's cells, 220 Calcification, primary, 42 Calyces, 125 Canalicuh, 3S Capillaries, 71 bile, 115 intralobular, 114 Capsule, 31, 224 of Bowman, 128 of Glisson, 114 Cardiac muscle, 52 Carmin, borax, as stain, 247 staining in sections with, scheme for, 259 Carmin-gelatin as injection fluid, 236 Cartilage, 30 cellular, 33 epiphyseal, 44 hyaline, 30 reticular, 32, 33 white fibrinous, 33 Cartilage, yellow elastic, 32, 33 Cartilage-cells, 31 Cell-body, 18 division of, 22 Cell-division by budding, 21 direct, 21 indirect, 21 karyokinesis, 21 karyomitosis, 21 mitosis, 21 modes of, 21 resting stage, 21 Celloidin embedding, 240 method of staining in sec- tions, scheme of prepara- tion of tissues for, 259 thick, 240 thin, 240 Cells, 17 acid, 106 basket, 219 bone-, 39 cartilage-, 31 chief, 106 columnar, 56 cortical, 97 daughter, 141 development of, 23 diagram of, IS fat-, 28 ganglion, 64 giant, 41 glia, 214 gustatory, 97 hair, of ear, 202 hepatic. 114 lymphoid, 85 marrow, 40 mast-, 79 mastoid, 197 migratory, 78 mother, 141 nerve-, 60 neuroglia, 63 of blood, 76 of'Cajal, 220 of Claudius, 201 of Deiters, 202 INDEX. 267 Cells of Hensen, 202 of neuroglia tissue, 214 olfactory, 206 origin of, 20 osteogenetic, 35 parental, 140 parietal, 106 peptic, 106 plasma, 41 prickle, 169 properties of, 19 specialization of, 24 spermatogenic, 141 squamous, 55 sustentacular, 141, 205 tactile, 64 compound, 64 tegment, 97 tendon, 28 time required for changes in, 23 Cell-spaces, 38 Cell-wall, 19 Cellular cartilage, 34 Cementum, 45, 99, 101 Centers of ossification, 42 Central canal, 210 nervous system, 208 vein, 115 Centrosome, 19 Carebellar tract, direct 212 Cerebellum, 215 cortex, scheme of, 219 section of, 216 Cerebral cortex, scheme of, 222 Cerebrum, 220 Ceruminous glands, 196 Chief cells, 106 Chlorid of mercury as fixative, 233 Chloroform balsam, 256 Chorda equina, 208 Choriocapillaris, 186 Choroid, 177, 186 coat, 186 layers of, 186 Chromatic granules of Nisei, 214 Chromic acid as decalcifying solution, 235 as fixative, 231 Chromophilic granules, 60 Cilia, 57 Ciliary body, 188 ring, 188 Ciliated epithelium, 58 Circumferential lymph-sinus, 87 Circumi,-allate papillae, 97 Clarke's column, 213 Claudius, cells of, 201 Clearing agents, 254 creasote, 255 oil of cloves, 255 xylol, 255 of specimens, 254 Clefts of Lantermann, 63 Clitoris, 158 Close skein, 21 Cochlea, 199 longitudinal section of, 179 membranous, 200 Cohnheim's areas, 49 Colored corpuscles, 73 action of reagents, 73 in other animals, 74 table showing size of, in various animals, 75 Colorless corpuscles, 76 Colostrum corpuscles, 160 Columnar cells, 56 Columns of Bertini, 124 Conductive epithelium, 58 Coni vasculosi, 139, 143 Conjunctiva, 177, 193 Connective tissue, 26 Cornea, 178 Corneal spaces, 179 Corona radiata, 152 Corpora amylacea, 224 cavernosa, 145 Corpus luteum, 153 false, 153 true, 153 spongiosum, 145 Corpuscles, 72 268 INDEX. Corpuscles, blood-, develop- ment of, 66 bone-, 39 colored, 72. See ;Uso Colored Corpiiscleti. colorle.'is, 76 colostrum, 160 crenated, 74 dust, SO genital, 65 of Krause, 158 of Hassall, 90 of Meissner, 64 of Vater, 65, 148 Pacinian, 65 red, 73. See also Colored Corpuscles. shadow, SO tactile, of skin, 64 third, 79 white blood-, 76 Corti, organ of, 201 Cortical cells, 97 Corneoscleral junction, 1S7 Cowper's glands, 14S Creasote as clearing agent, 255 Crenated corpuscles, 74 Crown of teeth, 99 Crypts of Lieberkiihn, 108 Crystals, blood, 81 Teichniann's 81 Cumulus ovigerus, 152 Cutaneous system, 169 Cytoplasm, 18, 55 Dahlia, as stain, 254 Damar, 250 Daughter cells, 141 Debove's endothelium, lOS Decalcification, 234 Decalcifying solutions, 234 chromic acid, 235 nitric acid, 235 phloroglucin, 235 picric acid, 235 Dehydration of sections, 238, 254 Deiters, cells of, 202 Delafield's formula for hema- toxylin stain, 250 hematoxylin and eosin, scheme for staining in sec- tions with, 259 "Delle," 73 Demilunes of Heidenhain, 119 Dendrites, 60, 213 Dental bulbs, 104 ridge, 103 Dentin, 46, 100 Dentinal fibers, 103 sheath, 100 tubules, 100 Descemet's endothelium, 180 membrane, ISO Diastcr, 21 Digestive tract, 96 Discus proligerus, 152 Ductus cochlearis, 200 Duodenal glands, 110 Duodenum, 109 Dura mater, 208 Dust corpuscles, 80 Ear, 196 external, 196 internal, 198 middle, 196 stones, 199 vestibule of, 198 Ectoderm, 23 Ejaculatorv duct, 139, 143 Eieidin, 169 Embedding, 239 celloidin, 240 interstitial, 239 paraffin, 242 Enamel, 99, 100 cuticle, 101 organ, 105 prisms, 100 INDEX. 269 End-bulbs of Krause, 65 Endocardium, 72 Endomysium, 49 Endfineuriuni, 63 End-organs, 64 Endothelium, Uescemet's, 180 of Debove, lOS Entoderm, 23 Eosinophiles, 41, 78 Eosinophilic granules, 41 Epiblast, 25 tissues originating from, 25 Epidermis, 169 Epididymis, 143 Epidural spaces, 208 Epimysium, 50 Epineurium 63 Epiphyseal cartilage, 44 Epithelium, 54 absorptive, 58 ciliated, 57 conductive, 57 germinal, 150 pavement, 57 propulsive, 57 protective, 57 secretory, 58 stratified, 57 transitional, 57 Epoophoron, 154 Erythroblasts, 41 Erythrocytes, 73. See also Colored Corpuscles. Esophagus, 105 fibrous coat of, 105 mucous coat of, 105 muscular coat of, 105 submucous coat of, 105 Eustachian tube, 197 Excretory duct, 171 Exoplasm, 19 Eye, 177 anterior chamber of, 177 diagram of, 178 lymphatic spaces o.f, ISO nerves of, 180 posterior chamber of, 177 EyeUds, 193 Fallopian tubes, 154 False corpus luteum, 153 Fangs of teeth, 09 Farrant's solution, 256 Fasciculi, 49, 63 Fasciculus cuneatus, 212 gracilis, 212 Fat-cells, 28 Female generative organs, 150 urethra, 136 l'"ciiestrated membrane of Henle, 09 Ferrein's pyramids, 124 Fiber, dentinal, 103 gray, 63 meduUated, 61 nonmeduUated, 63 pale, 63 perforating, of Sharpey, 39 radiating, of Mijller, 181 Ivemak's, 63 Fibrte arcuatm, 179 terminales, 208 Fibrocartilage, white, 31 Filiform papilhr, 96 Filum terminally, 208 Fissures, median, anterior, 211 posterior, 211 Fixation, 230 Fixatives, 230 alcohol, 230 ammonium bichromate, 231 chromic acid, 231 Flemming's solution, 232 formaldehyd, 232 mercuric chlorid, 233 Mijller's fluid, 231 Orth's solution, 232 potassium bichromate, 231 Flemming's solution, 232 Formaldehyd as fixative, 232 Fovea centralis, 177, 185 Freezing, 244 Fundamental column, anterior 211 Fungiform papilla;, 96 270 INDEX. Gall-bladder, 117 Ganglia, 63 Ganglion cells, 64 spiralae, 202 Generative organs, female, 150 male, 138 Genital corpuscles, 65 of Krause, 158 end-bulbs, 158 Germinal epithelium, 150 spot, 153 \esicle, 153 Giant cells, 41 Glands, 93 alveolar, 94 Brunner's, 110 Cowper's, 148 duodenal, 110 mammary, 158 of Bartholin, 158 of Littre, 136 of Tyson, 144 parotid, 117, 120 pyloric, 107 racemose, 94 saccular, compound, 94 simple, 94 salivary, 117. See also Salivary Glands. sebaceous, 171 sublingual, 117, 121 submaxillary, 117, 122 sudoriferous, 171 sweat-, 171 thyroid, 167 tubular, coiled, 94 compound, 94 simple, 93 types of, 93 Glandula; odoriferae, 144 Glia cells, 214 Glisson, capsule of, 114 Globus major, 139 minor', 139 Glomeruli, 126, 129 cochlea?, 203 Glycerin .jelly, 257 GoU's column, 212 Gowers' tract, 212 Graafian follicles, 150 Granules, chromatic, of Nisei, 214 chromophilic, 60 eosinophilic, 41 neutrophile, 41 zymogen, 121 Gray commissure, 210 anterior, 210 posterior, 210 matter of spinal cord, 210 substance, 212 Grenacher's formula for borax carmin stain, 247 Ground bundle, anterior, 211 substance, 30, 31 Gustatory cells, 97 Hair, 172 cells of ear, 202 follicle, 174 coats of, 174, 175 root of, 173 shaft of, 173 layers of, 173, 174 Hardening of specimen, 238 Hassall's corpuscles, 90 Haversian canals, 36 lamella", 36 system, 36 of adult bone, 43 Haymen's solution, 261 Heart, 72 muscle, 52 valves of, 72 Heidenhain, demilunes of, 119 Helicene arteries, 146 Hematin, 81 Hematoblasts, 41 Hematoidin, 81 Hematoxylin, acid, as stain, 251 staining in sections with, scheme for, 260 and eosin, Delafield's, scheme for staining in sections with, 259 INDEX. 271 Hematoxylin as stain, 250 Hemin, 81 Hemoglobin, 73, 81 Henle's fenestrated membrane, 69 layer, 175 loop, 126 ascending limb of, 126, 131 descending limb of, 126, 131 Hensen, cells of, 2(J2 median line of, 47 Hepatic artery, 114 cells, 114 veins, 115 Highmore, body of, 138 Hilum of kidney, 125 Histology, definition of, 17 Humors, aqueous, 192 vitreous, 193 Huxley's layer, 175 Hyaline cartilage, 30 Hyaloid membrane, 193 Hyaloplasm, 18 Hypoblast, 24 tissue originating from, 25 Infundibhla, 125, 163 Injection fluids, 236 Berlin blue, 237 carmin-gelatin, 236 Interglobular spaces, 100 Interlobular arteries, 114, 131 vein, 114, 133 Interstitial embedding, 239 Intestine, 108 blood supply of, ) 13 large, 110 lymphatics of, 114 muscular coat of, 109 nerves of, 113 small, 108 submucosa of, 109 Intralobular capillaries, 114 vein, lis Iris, 189 Ivory of teeth, 99 Karyokinesis, 21 diagram of stages of, 22 Karyomitosis, 21 Keratin, 170 Kidne.\-, 124 diagram of, 127 first convoluted tubule of, 126 - hilum of, 1 25 labyrinth of, i 25 lymphatics of, 133 nerves of, 133 pelvis of, 125, 133 pyramidal convoluted tubule of, 126 sinus of, 125, 133 spiral tubule of, 126, 130 Krause's end-bulbs, 65 genital corpuscles, 158 membrane, 47 Kulschitsky's formula for acid hematoxylin stain, 251 Labia majora, 158 minora, 15S Labyrinth, 198 of kidney, 124 Lacrimal glands, 194 Lacteal, 108 LacunfE, 31, 37, 179 Lamellee, 35 circumferential, 35, 44 fundamental, 35 ground, 37 Haversian, 36 interstitial, 37 special, 36 tympanic, 200 Langerhans' bodies, 121 Lanterman, clefts of, 63 Large intestine, 110 Larynx, 162 Lateral tract, ascending ante- rior, 212 descending anterior, 212 mixed, 212 272 INDEX. Lens, 177, 191 stars, 192 suspensory ligaments of, 177 Leukocytes, 76 "Tjieberkuhn, crypts of, 108 Ligaments, suspensory, 192 Liquor folliculi, 152 sanguinis, 72 Litliium carmin as stain, 248 Littre's glands, 136 Liver, 114 lymphatics of, 116 Logwood and eosin as stain, 251 Loop of Henle, 126. See also Henle's Loop. Loose skein, 21 Lungs, 163 section of, 165 Lymph, 85 Lymphatic system, 84 Lymphatics, 71 perineurial, 85 perivascular, 71, 85 Lymph-cords, 87 Lymph-follicles, 85 capsule of, 85 Lymph-glands, 86 capsule of, 86 trabeculip of, 86 Lymph-nodes, 86 Lymphocytes, large, 77 small, 77 Lymphoid cells, 85 Lymph-sinus, 87 Lymph-vessels, 84 Macula lutea, 176, 185 Male generative organs, 138 urethra, 135, 146 Malpighian bodies, 89, 126 pyramids, 124 Mammary glands, 158 Margarin, 29 Marrow, 40 cell, 41 red, 40 Marrow, yellow, 41 Mast-cells, 79 Mastoid cells, 197 Mastzellen, 41, 79 Matrix, 30, 31, 175 Mayer's albumin, 243 hemalum, 251 paracarmin, 249 Median fissures, 211 Mediastinum, 138 Medullary cavity, 44 rays, 124 sheath, 62 Meibomian glands, 193 Meissner's corpuscles, 64 plexus, 114 Membrana vestibularis, 200 Membrane, basement, 58, 93 mucous, 93 of Bowman, 179 of Krause, 47 serous, 91 Mercuric chlorid as fixative, 233 clilorid-acetic acid, 234 Mesoblast, 24 tissues originating from, 25 Mesoderm, 24 Metaplasm, 18 Microcytes, 80 Microsomes, 18 Microtomes, 239 "Migratory" cells, 78 Milk of mammary glands, 159 Minute structures, 212 Mitosis, 21 Modiolus, 200 Monaster, 21 Mother cells, 141 Mounting, 255 Mouth, 86 Mucin, 26 Mucosa, 86 Mucous membranes, 93 tissue, 26 Miiller, radiating fibers of, 181 Mailer's fluid, 231 Muscle, 47 INDEX. 273 Muscle, heart, 52 involuntary, 50 nonstriated, 50 plain, 50 skeletal, 47 smooth, 50 nerve-endings in, 65 striated, 47 tabulated comparison of three types, 53 voluntary, 47, 48 nerve-endings in, 65 Muscularis mucosae, 93 Myelin, 62 Myelocytes, 41 Myeloplax, 41 Myocardium, 72 Nail, 175 bed, 175 grooA'e, 175 Nasal mucous membrane, 205 Neck of teeth, 99 Nerve-cell, 60 Nerve-endings, 64 in smooth muscle, 65 in tendons, 66 in voluntary muscles, 65 Nerve-fibers, nonmeduUated, 53 Nerves, 60, 61 of intestine, 113 Nervous system, central, 208 Neuraxon, 214 Neurilemma, 62 Neuro-epithelium, 39 Neuroglia, 63 cells, 63 tissue/ 214 Neuron, 60 Neutrophile granules, 41 polymorphonuclear, 77 Nisei, chromatic granules of, 214 Nitric acid as decalcifying solution, 235 phloroglucin as decalcify- ing Solution, 235 18 Nodes of Ranvier, 62 NonmeduUated fibers, 63 Nuclear matrix, 19 membrane, 19 network, 19 Nuclei, 62 Nucleoli, 60 Nucleolus, 19 Nucleus, 19 division of, 22 spheroid, 60 Nuel's spaces, 202 Odontoblasts, 102 Oil of cloves as clearing agent, 255 Olfactory cells, 206 mucous membrane, 205 Ora serrata, 177, 185 Orcein as stain, 252 Orth's solution, 232 Osmic acid as stain, 246 Ossification, centers of, 42 Osteoblasts, 43 Osteoclasts, 44 Osteogenetio cells, 35 layer of periosteum, 35 Otoliths, 199 Ovarian stroma, 150 Ovary, 150 blood supply of, 153 lymphatics of, 153 tunica albuginea of, 150 externa of, 152 interna of, 152 Oviducts, 154 Ovulse Nabothi, 156 Ovum, 23, 152 Pacchionian bodies, 209 Pacinian corpuscles, 65 Pancreas, 117, 120 Papillfe, circumvallate, 96 filiform, 95 fungiform, 95 of tongue, 95 374 INDEX. Parablast, 24 tissues originating from, 26 Paraffin embedding, 242 method of staining in sec- tions, sclieme of prepara- tion of tissue for, 25S Parietal cells, 106, 140 Parotid gland, 117, 120 Parovarium, 154 Pavement epithelium, 5.S Penis, 144 tunica albuginea of, 145 Peptic cells, 106 Pericardium, 72 Perichondrium, 30 cellular layer of, 30 fibrous layer of, 30 Perimysium, 49 Perineurial lymphatics, 85 Perineurium, 63 Periodontal memlirane, 102 Periosteum, 35 cellular layer of, 35 inner layer of, 35 osteogehetic layer of, 35 outer fibrous layer of, 35 Perivascular lymphatics, 71, 85 Petit, canal of, 192 Peyer's patches, 109 Pfluger's sahvary tubes, 118 Phagocytes, 78 Pia mater, 209 Picric acid as decalcifying solu- tion, 235 in borax carmin staining, 238 Picro-acid-fuchsin as stain, 252 Pineal body, 224 Pinna, 196' Pituitary body, 223 Plaques, blood, 79 Plasma, 72 cells, 41 Platelets, blood, 79 Pleura, 164 Plexus of Auerhach, 114 of Meissner, 114 Plexus, terminal, 64 Polymorphonuclear neutro- philes, 77 Portal canals, 116 vein, 114 Potassium bichromate as fixa- tive, 231 Prickle cells, 169 Primary bundles, 38 calcification, 42 columns of spinal cord, 211 germ layers, 24 tissues originating from, 25 Primordial ova, 150 Propulsive epithelium, 58 Prostate, 147 Prostatic concretions, 144, 147 Protective epithelium, 27 Protoplasm, 18 Pseudopod, 77 Pseudostomafa, 92 Pulp of teeth, 99, 102 Pulp-cavity oif teeth, 99 Purkinje's cells, layer of, 218 Pyloric glands, 107 Pyramidal tract, crossed, 212 direct, 211 Pj'ramids of Ferrein, 124 . "of Malpighi, 124 Racemose glands, 94 Radiating fibers of MuUer, 181 Ranvier's nodes, 61 Rectal valves, 110 Rectores pilorum, 175 Red corpuscles, 73. See also Colored Corpuscles. Reissner's membrane, 200 Remak's fiber, 63 Resorcin-fuchsin as stain, 2.53 Respiratory mucous mem- brane, 205 syiBtem, 162 Resting stage, 21 Rete mucosum, 169 testis, 138 INDEX. 275 Rete testis, tubules of, 143 Reticular cartilage, 32, 33 process, 215 Retiform tissue, 29, .S5 Retina, 177, 180 blood supply of, 186 blood supply of, 186 diagram of, 182 proper, 180 layers of, ISO, 183 section of, 181 Reverse procedure, 22 "Ribbon" sectioning, 243 RosenmiiUer, organ of, 154 Saccular glands, 94 Salivary glands, 117 abdominal, 120 acini of, 118 alveoli of, 118 blood supply of, 119 ducts of, 117 lymphatics of, 120 mixed, 119 mucous, 118 nerves of, 120 seromucous, 119 serous, 118 tubes of Pfliio-er, 118 Sarcolemma, 47 Sarcoplasm, 49 Sarcostyles, 48 Sarcous elements, 48 Sartoli's columns, 141 Scala media, 205 tympani, 200 vestibuli, 200 Schlemm's canal, 189 Schwann, white substance of, 62 Sclera, 177, 187 layers of, 187, 188 Sebaceous glands, 171 Secondary bundles, 28 columns of spinal cord, 211 Secretory epithelium, 59 Sectioning, 238 Sectioning, free-hand, 239 ribbon, 243 Sections, dehydration of, 238, 254 Semen, 144 Semicircular canals, 198 Septum lingualse, 97 Serous cavities, 91 membrane, 91 Shadow corpuscles, 80 Sharpey's perforating fibers, 39 Sheath, medullary, 62 Skein, close, 21 loose, 21 Skin, 169 Small intestine, 108 Sole plate, 66 Solitary follicles, 108 Specialization of cells, 24 Spermatic ducts, 143 Spermatoblasts, 142 Spermatogenic cells, 141 Spermatozoa, 142 Spheroid nucleus, 60 Spinal cord, 208 gray matter of, 210 lumbar section of, 213 primary columns of, 211 secondary columns of, 211 white matter of, 210 vSpindles, tendon, 66 Spiral lamina, membranous, 200 tube, 200 Spirals?, ganglion, 202 Spleen, 88 blood-vessels of, 89 capsule of, 89 nerve-fibers of, 90 section from surface of, 89 trabeculte of, 89 Spongioplasm, 18 Squamous cells, 65 Staining, 246 in bulk, tabular scheme of, preparation of tissue for, 257 276 INDEX. Staining in sections by cel- loidin method, scheme of preparation of tissue for, 259 by paraffin method, scheme of preparation of tissue for, 258 with acid hematoxylin, scheme for, 260 with borax carmin, scheme for, 259 with Delafield's hema- toxylin and eosin, scheme for, 259 Stains, 246 borax carmin, 247 dahlia, 254 hematoxylin, 250 acid, 251 lithium carmin, 248 logwood and eosin, 251 orcein, 252 osmic acid, 246 picro-acid-fuchsin, 252 resorcin-f uchsin , 253 Sudan III, 247 Van Gieson's, 252 Weigert's, 253 Stenson's duct, 120 Stigmata, 71 Stomach, 106 blood supply of, 113 cardiac end of, 106 mucous coat of, 106 muscular coat of, 107 pyloric end of, 107 serous coat of, 107 submucous coat of, 107 Stomata, 92 Stones, ear, 199 Stratified epitheUura, 58 Stratum corneum, 170 granulosum, 152, 169 lucidum, 170 Malpighii, 169 papillae, 171 reticulare, 171 Stroma of choroid, 186 Stroma, ovarian, 150 Subarachnoidean spaces, 209 Subdural spaces, 208 Sublingual glands, 117, 121 Sublobular veins, 115 SubmaxiUary gland, 117, 122 Submucosa, 96 Substantia gelatinosa Rolandi, 215 Sudan III, 247 Sudoriferous glands, 171 Suprarenal body, 224 Suspensory ligament, 192 Sustentacular cells, 141, 205 Sweat-glands, 171 Tactile cells, 64 compound, 64 corpuscles of skin, 64 Taste-buds, 97 Teasing, 229 Technic, 229 Teeth, 99 crown of, 99 development of, 103 fang of, 99 ivory of, 99 neck of, 99 pulp of, 99, 102 pulp-cavity of, 99 Tegment cells, 97 Teichmann's crystals, 81 Tendon, 27 cells, 28 nerve-endings in, 66 spindles, 66 Terminal plexuses, 64 Testicle, 138 tubule of, 141 tunica albuginea of, 138 vertical section of, 139 Theca foUicuU, 152 Third corpuscles, 79 Thoracic duct, 84 Thymus, 90 Thyroid, 167 Tissue, 25 INDEX. 277 Tissue, adenoid, 29 adipose, 28, 29 areola, 26 connective, 26 diffuse adenoid, 85 erectile, section of, 145 mucous, 26 originating from primary germ layers, 25 retiform, 29, 85 to be stained in bulk, tabu- lar scheme of prepara- tion of, 257 in sections by oelloidin method, scheme of preparation of, 259 by paraffin method, scheme of prepara- tion of, 25S white fibrous, 26, 27 yellow elastic, 28 Tongue, 96 blood-supply of, 98 lymphatics of, 98 mucous membrane of, 98 papillEe of, 96 Tonsils, 91 Tooth-pulp, 99, 102 Trachea, 162 Transitional epithelium, 58 True corpus luteum, 153 Tubular glands, 93. See also Glands, Tubular. Tunica adventitia, 69 albuginea of ovary, 150 of penis, 145 of testicle, 138 externa of ovary, 152 interna of ovary, 152 intima, 69 media, 69 vaginalis, 138 vasculosum, 138 Tijrck's column, 211 Tympanic cavity, 197 "lamella, 200 Tympanum, 196 Tyson's glands, 144 Ureters, 133 Urethra, 135, 145 female, 136 male, 135, 146 Urinary bladder, 134 tract, 124 Uriniferous tubules, 125 Uterus, 154 blood-vessels of, 156 coats of, 154, 155 lymphatics of, 157 Vagina, 157 blood-vessels of, 157 lymphatics of, 157 Valves of heart, 72 of thoracic duct, 84 rectal, 110 Valvule conniventes, 108 Van Gieson's stain, 252 Vas deferens, 139, 143 Vasa efferentia, 138, 143 recta, 138 vasorum, 71 Vascular system, 68 Vater, corpuscles of, 65 Vein, 71 central, 115 hepatic, 115 interlobular, 114, 133 intralobular, 115 portal, 114 sublobular, 115 Venje stella;, 133 Vesicula seminalis, 139 Vestibule of ear, 198 Villi of small intestine, 108 Vitelline membrane, 152 Vitellus, 153 Vitreous humor, 178, 193 Volkmann's canals, 37 Weigert's stam, 253 Wharton's duct, 122 White blood-cells, 76 fibrocartilage, 31, 33 278 INDEX. White fibrous tissue, 26, 27 matter of spinal cord, 210 substance, 215 of Schwann, 62 Wolffian body, 143 duct, 154 Wreath, 21 Xylol as clearing agent, 255 Yellow elastic cartilage, 32, 33 tissue, 28 Zenker's fluid, 234 Zinn, zone of, 192 Zona fasciculata, 224 glomerulosa, 224 pectinata, 201 pellucida, 152 reticularis, 225 spongiosa, 215 tecta, 201 terminalis, 215 Zone of Zinn, 192 Zonula ciliaris, 192 Zymogen granules, 121 SAUNDERS' BOOKS Pathology, Physiology Histology, Embryolog'y and Bacteriology W. B. SAUNDERS Ci COMPANY 925 Walnut Street Philadelphia 9, Henrietta Street Covent Garden, London LITERARY SUPERIORITY 'l^HE excellent judgment displayed in the publications of the house at the very beginning of its career, and the success of the modern business methods employed by it, at once attracted the attention of leading men in the profession, and many of the most prominent writers of America offered their books for publication. 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ISJain emphasis has been laid upon those facts and views which will be directly helpful in the practical branches of medicine. At the saiue time, however, sufficient consideration has been given to the experimental side of the science. The entire literature of physiology has been thoroughly digested by Dr. Howell, and the im- portant views and conclusions introduced into Ms work, so that the student has the benefit of the latest advances along this line. Illustrations have been most freely used whenever it was thought they would be helpful in understanding or supplementing the descriptioas in the text. They are all original. HISTOLOGY. Bohm, Davidoff, and Huber's Histology AText=Bookof Human Histology. Including Microscopic Technic. By Dr. A. A. Bohm and Dr. l\f. von Davidoff, of Munich, and G. Carl Huber, M. D., Professor of Histology and Embryology in the University of Michigan, Ann Arbor. Handsome octavo of 528 pages, with 377 beautiful original illus- trations. Flexible cloth, ^3.50 net. RECENTLY ISSUED— SECOND REVISED EDITION The work of Drs. Bohm and Davidoff is well known in the German edi- tion, and has been considered one of the most practically useful books on the subject of Human Idistology. This American edition has been in great part rewritten and very much enlarged by L^r. Huber, who has also added over one hundred original illustrations. Dr. Huber's extensive additions have rendered the work the most complete students' text-book on Histology in existence. Tlie book contains particularly full and explicit instructions in the matter of technic, and it will undoubtedly prove of the utmost value to students and practical worlcers in the Histologic Laboratory. Special atten- tion is called to the fulness of the text, the large amount of matter on technic, and the numerous handsome illustrations. OPINIONS OF THE MEDICAL PRESS British Medical Journal " The combined authorship of so many distinguished men has led to the production of a most valuable work. The illustrations are most beautiful, and beautifully executed, and their study will be an education in themselves." Boston Medical and Surgical Journal " Is unquestionably a text-book of the first rank, having been carefully written by thorough masters of the subject, and in certain directions it is much superior to any other histological manual." American Medicine " It is recognized as the highest authority in Germany. ... A book on histology which surpasses anything of its kind now in print." ^ SAUNDERS' BOOKS ON GET A«*^^«.:r«'k*% THE NEW THE BEST /\nierii,an standard Illustrated Dictionary Third Revised Edition— Recently Issued The American Illustrated Medical Dictionary. A new and complete dictionary of the terms used in Medicine, Surgery, Dentistry, Pharmacy, Chemistry, and kindred branches ; with over loo new and elaborate tables and many handsome illustra- tions. By W. A. Newman Borland, M. D., Editor of "The American Pocket Medical Dictionary." Large octavo, nearly 800 pages, bound in full flexible leather. Price, $4.50 net; with thumb index, ^5.00 net. Gives a Maximum Amount of Matter in a Minimum Space, and at the Lowest Possible Cost THREE EDITIONS IN THREE YEARS— 1500 NEW TERMS The immediate success of this work is due to the special features that distinguish it from other books of its kind. It gives a maximum of matter in a minimum space and at the lowest possible cost. Though it is practi- cally unabridged, yet by the use of thin bible paper and flexible morocco binding it is only \i^ inches thick. In this new edition the book has been thoroughly revised, and upward of fifteen hundred new terms have been added, thus bringing the book absolutely up to date. The book con- tains hundreds of tenns not to be found in any other dictionary, over IOC original tables, and many handsome illustrations. PERSONAL OPINIONS Howard A. Kelly, M. D., Professor of Gynecology, Johns Hppkins Uniiiersity, BaltitMnre. " Dr. Dorland's dictionary is admirable. It is so well g^otten up and of such conve- nient size. No errors have been found in my use of it." Roswell Park, M. D., Professor of Priticiples and Practice of Svrg-ery and of Clinic (il Surgery, University of Bttffa'lo. " I must acknowledg^e my astonishment at seeing how much he has condensed within relatively small space. 1 find nothing to criticize, very much to commend, and was inter- ested in finding some of the new words which are not in other recent dictionaries." PATHOLOGY. Stengel's Text-Book of Pathology Fourth Edition, Revised— Recently Issued A Text=Book of Pathology. By Alfred Stengel, M. D., Professor of Clinical Medicine in the University of Pennsylvania. Octavo volume of 933 pages, with 394 text-illustrations, many in colors, and 17 full-page plates, 7 in colors. Cloth, SS-°o net; Sheep or Half Morocco, $6.00 net. WITH 394 TEXT-CUTS, MANY IN COLORS, AND 17 PLATES, 7 IN COLORS In this work Ihe practical application of pathologic facts to clinical medi- cine is considered more fully than is customary in works on pathology. In this edition the section dealing with General Pathology has been most extensively revised, several of the important chapters having been practically rewritten. A very useful addition is an Appendix treating of the technic of pathologic methods, giving briefly the most important methods at present in use for the study of pathology, including, however, only those methods capable of giving satisfactory results. PERSONAL AND PRESS OPINIONS William H. Welch, M. D., Professor 0/ Patholog'y, Johns Hopkins University, Baltimore, Md. " I consider the work abreast of modern pathology, and useful to both students and practitioners. It presents in a concise and well-considered form the essential facts of general and special pathologic anatomy, with more than usual emphasis upon pathologic physiology." Ludvig Hektoen, M. D.. Professor of Pathology, Rush Medical College, Chicago. " I regard it as the most serviceable text-book for students on this subject yet written b^-- an American author." The Lancet, London " This volume is intended to present the subject of pathology in as practical a form as possible, and more especially from the point of view of the 'clinical pathologist.' These subjects have been faithfully carried out, and a valuable text-book is the result. We can most favorably recommend it to our readers as a thoroughly practical work on clinical pathology." SAUNDERS' BOOKS ON Mallory and Wright's Patholo£(ic Technique Recently Issued— Third Edition. Enlarged Pathologic Technique. A Practical Manual for Workers in Pathologic Histology, including Directions for the Performance of Autopsies and for Clinical Diagnosis by Laboratory Methods. By Frank B. Mallory, M. D., Associate Professor of Pathology, Harvard University ; and James H. Wright, M. D., Director of the Clinico-Pathologic Laboratories, Massachusetts General Hos- pital. Octavoof 469 pages, with 13S illustrations. Cloth,g3.oo net. WITH CHAPTERS ON POST-MORTEM TECHNIQUE AND AUTOPSIES In revising the book for the new edition the authors have kept in vievp the needs of the laboratory worker, whether student, practitioner, or pathologist, for a practical manual of histologic and bacteriologic methods in the study of pathologic material. Many parts have been rewritten, many new methods have been added, and the number of illustrations has been considerably increased. Among the many changes and additions may be mentioned the amplification of the description of the Parasite of Actinomycosis and' the insertion of descriptions of the Bacillus of Bubonic Plague, of the Parasite of Mycetoma, and Wright's methods for the cultivation of Anaerobic Bacteria. There have also been added new staining methods for elastic tissue by Weigert, for bone by Schmorl, and for connective tissue by Mallory. PERSONAL AND PRESS OPINIONS William H. Welch, M.D., Professor of Pathology , Johns Hopkins University, Baltimore, Md. " I have been looking forward to ttie publication of this book, and I am g-Iad to say that 1 find it a most useful laboratory and post-mortem guide, full of practical information and well up to date." Boston Medical and Surgfical Journal " This manual, since its first appearance, has been recognized as tlie standard guide in pathological technique, and has become well-nigh indispensable to the laboratory worker." EMBRYOLOGY. Heisler's Text-Book qf Embryology Second Edition, Thoroughly Revised A Text-Book of Embryology. By John C. Heisler, M. D., Professor of Anatomy in the Medico-Chirurgical College, Phila- delphia. Octavo volume of 405 pages, with 196 illustrations, 32 of them in colors. Cloth, ^2.50 net. WITH 196 ILLUSTRATIONS, 32 IN COLORS The fact of embryology having acquired in recent years siicli great interest in connection with the teaching and with the proper comprehension of human anatomy, it is of first importance to the student of medicine that a concise and yet sufficiently full text-book upon the subject be available. In this edition the work has been thoroughly revised, and such additions have been made as the progress of the science has rendered necessary. Moreover, the entire work has been generally improved. The chapter treating of the Deciduse and the Placenta has been rewritten, as has also the greater part of that upon the Chorion. In addition to these changes, several new illustrations have been added. PERSONAL AND PRESS OPINIONS G. Carl Huber, M. D., Professor of Histology and Embryology, University of Michigan, Ann Arbor. " I find the sscond edition of 'A Text-Book of Embryology ' by Dr. Heisler an improve- ment on the first. The figures added increase greatly the value of the work. I am again recommending it to our students." William Wathen, M.D., Professor of Obstetrics, Abdominal Surgery, and Gynecology, and DeaJt , Kentucky School of Medicine, Louisville , Ky. " It is systematic, scientific, full of simplicity, and just such a work as a medical student will be able to comprehend." Birmingham Medical Review, England "We can most confidently recommend Dr. Heisler's book to the student of biology or medicine for his careful study, if his aim be to acquire a sound and practical acquaintance with the subject of embryology." SAUNDERS' BOOKS ON McFarland's Pathogenic Bacteria Fourth Edition, Rewritten and Enlarged A Text=Book upon the Pathogenic Bacteria. By Joseph McFarland, M. D., Professor of Pathology and Bacteriology in the Medico-Chirurgical College of Philadelphia ; Pathologist to the Medico-Chirurgical Hospital, Philadelphia, etc. Octavo volume of 629 pages, finely illustrated. Cloth, ^3.50 net. RECENTLY ISSUED This book gives a concise account of the technical procedures necessary in the study of bacteriology, a brief description of the life-history of the important pathogenic bacteriLi, and sufficient description of the pathologic lesions accom- panying the micro-organismal invasions to give an idea of the origin of symp- toms and the causes of death. The illustrations are mainly reproductions of the best the world affords, and are beautifully and accurately executed. The chapters upon Infection and Immunity have been greatly extended by the addition of many new facts. The value of the work has been consider- ably enhanced by the introduction of a large number of references to the literatme. PERSONAL AND PRESS OPINIONS H. B. Anderson, M. D.. Professor of Pathology and Bacteriology y Trinity Medical College^ Toronto. " The bnok is a satisfactory one, and I shall take pleasure in recommending it to the students of Trinity College." The Lancet, London - " It is excellently adapted for the medical students and practitioners for whom it is avowedly written. . . . The descriptions given are accurate and readable, and the book should prove useful to those for whom it is written." New York Medical Journal "The author has succeeded admirably in presenting the essential details of bacterio' logical technic, together with a judiciously chosen summary of our present Icnowledge <»f pathogenic bacteria." BACTERIOLOGY AND PATHOLOGY. Eyre's Bacteriologiic Technique The Elements of Bacteriologic Technique. A Laboratory Guide for the Medical, Dental, and Technical Student. By J. W. H. Eyre, M. D., F. R. S. Edin,, Bacteriologist to Guy's Hospital, London, and Lecturer on Bacteriology, Medical and Dental Schools, etc. Octavo, 375 pages, with 170 illustrations. Cloth, I2.50 net. This book presents, concisely yet clearly, the various methods at present in use for the study of bacteria, and elucidates such points in their life-his- tories as are debatable or still undetermined. The illustrations are numerous and practical. Medical News, New York "Of the many laboratory guides constantly being issued, this book is undoubtedly the best that has reached us." Warren's Pathology and Therapeutics Surgical Pathology and Therapeutics. By John Collins Warren, M. D., LL.D., F. R. C. S. (Hon.), Professor of Surgery, Harvard Medical School. Octavo, 873 pages, 136 relief and lithographic illustrations, 33 in colors. With an Appendix on Scientific Aids to Surgical Diagnosis, and a series of articles on Regional Bacteriology. Cloth, ^5.00 net; Sheep or Half Mo- rocco, ^6.00 net. SECOND EDITION, WITH AN APPENDIX In the second edition of this book all the important changes have been embodied in a new Appendix. In addition to an enumeration of the scientific aids to surgical diagnosis there is presented a series of sections on regional bacteriology, in which are given a description of the flora of the affected part, and the general principles of treating the affections they produce. Roswell Park, M. D., In the Harvard Graduate Magazine. " 1 think it is the most creditable book on surgical pathology, and the most beautiful medi- cal illustration of the bookmakers' art that has ever been issued from the American press." SAUNDERS' BOOKS ON Dtirck and Hektoen's Special Pathologic Histolog'y Atlas and Epitome of Special Pathologic Histology. By Dr. H. Durck, of Munich. Edited, with additions, by LuDviG Hektoen, M. D., Professor of Pathology, Rush Medical College, Chicago. In two parts. Part I. — Circulatory, Respira- tory, and Gastro-intestinal Tracts. 120 colored figures on 62 plates, and 158 pages of text. Part II. — Liver, Urinary and Sexual Organs, Nervous System, Skin, Muscles, and Bones. 123 colored figures on 60 plates, and 192 pages of text. Per part: Cloth, ^3.00 net. In Saunders' Hand-Atlas Scries. The great value of these plates is that they represent in the exact colors tlie effect of the stains, which is of such great importance for the differentia- tion of tissue. The text portion of the book is admirable. William H. Welch, M. D.. Pi-ofessor of Pathology, Johns Hopkins Unk'ersiiy, Baltimore. " I consider Diirck's 'Atlas of Special Pathologic Histology,' edited by Hektoen. a very useful book, for students and others. The plates are admirable." Sobotta and Huber's Human Histolog'y Atlas and Epitome of Human Histology and Microscopic Anatomy. By Privatdocent Dr. J. Sobotta, of ^Vurzburg. Edited, with additions, by G. Carl Huber, M. D., Professor of Histology and Embryology, and Director of the Histological Laboratory, University of Michigan, Ann Arbor. With 214 colored figures on 80 plates, 68 text-illustrations, and 248 pages of text. Cloth, $4.50 net. //; Saunders Hand-Atlas Series. Lewdly s F. Barker, M. D., Pt;>/c!i!;iu' and Hea,/ of ihc 0,:J>a>-/mrnt of Avatomy. Utn~'crsity of Chicago. " 1 cnnfiratulate you upon the appearance of this volume. The ilhistrations are certainly very fine, and Pr Huber has made important contributions to the text. The book should have a large sale." PHYSIOLOGY. 13 American Text-Book of Physiology American Text=Book of Physiology. In two volumes. Edited by William H. Howell, Ph. D., M. D., Professor of Physiology in the Johns Hopkins University, Baltimore, Md. Two royal octavo volumes of about 600 pages each, fully illus- trated. Per volume: Cloth, ^3.00 net; Sheep or Half Morocco, ^3-75 net. SECOND EDITION, REVISED AND ENLARGED Even in the short time that has elapsed since the first edition of this work ttiere has been much proj^ress in Physiology, and in this edition the book has been thoroughly revised to keep pace with this progrebs. The chapter upon the Central Nervous System has been entirely rewritten. A section on Physical Chemistry forms a valuable addition, since these views are taking « large part in current discussion in physiologic and medical literature. The Medical News " Ttie work will stand as a work of reference on pliysiology. To him wlio desires to know the status of modern physiology, who expects to obtain suggestions as to further physiologic inquiry, we know of none in English which so eminently meets such a demand." Stewart's Physiology A Manual of Physiology, with Practical Exercises. For Students and Practitioners. By G. N. Stewart, M. A., M. D., D. Sc, Professor of Physiology in the University of Chicago. Octavo volume of 894 pages, with 336 illustrations and 5 colored plates. Cloth, ^3.75 net. FOURTH REVISED EDITION This work is written in a plain and attractive style that renders it par- ticularly suited to the needs of students. The systematic portion is so treated that it can be used independently of the practical exerciies, which constitute an important feature of the book. In the present edition a considerable amount of new matter has been added, es|iecially to the chapter on the Central Nervous System. Philadelphia Medical Journal " Those familiar with the attainments of Prof. Stewart as an original investigator, as a teacher and a writer, need no assurance that in this volume he has presented in a terse, concise, accurate manner the essential and best established facts of physiology in a most attractive manner." 14 SAUNDERS' BOOKS ON Levy and Klemperer's Clinical Bacteriolog'y The Elements of Clinical Bacteriology. By Drs. Ernst Levy and Felix Klemperer, of the University of Strasburg Translated and edited by Augustus A. Eshner, M. D., Pro- fessor of Clinical Medicine, Philadelphia Polyclinic. Octavo \olume of 440 pages, fully illustrated. Cloth, ^2.50 net. S. Solis-Cohen, M. D., Professor o/ Clinical Medicine, Jefferson Medical College, Phila. "I consider it an excellent book. I have recommended it in speaking to my students." Lehmann, Neumann, and Weaver's Bacteriolog'y Atlas and Epitome of Bacteriology : including a Text- Book OF Special Bacteriologic Diagnosis. By Prof. Dr. K. B. Lehmann and Dr. R. O. Neumann, of Wtirzburg. J^ro7n the Second Revised and Enlarged German Edition. Edited, with additions, by G. H. Weaver, M. D., Assistant Professor of Pathology and Bacteriology, Rush Medical College, Chicago. In two parts. Part L — 632 colored figures on 6g lithographic plates. Part IL — 511 pages of text, illustrated. Per part: Cloth, ^2.50 net. In Saunders' Hand- Atlas Series. Lewis* Anatomy and Physiology Anatomy and Physiology for Nurses. By LeRoy Lewis, M. D,, Surgeon to and Lecturer on Anatomy and Physi- ology for Nurses at the Lewis Hospital, Bay City, Michigan. 12 mo of 200 pages, with 100 illustrations. JUST ISSUED The author has based the plan and scope of his work on the methods he has employed in teaching the subjects, and has made the text unusually PATHOLOGY, BACTERIOLOGY, .LVD FILYSIOLOGY. 15 Senn'S Tumors second Revised Edition Pathology and Surgical Treatment of Tumuus. By Nicholas Senn M. D., Ph. D., LL.D., Professor of Surgery, Rush Medical Col- lege, Chicago. Handsome octavo, 718 pages, with 478 engravings u ,r''^?S '^ full-page colored plates. Cloth, ^5.00 net; Sheep or Half Morocco, $6.00 net. illM'Jnf.H'"""/'''-!'?''.?'"^ f ''"^ '■''"'" ''°.°'' '" '^"ff''"'' °° 'his subject. It is well Illustrated, and will doubtless remain as the principal monograph oti the subject in our language for some ye^TS." -Journal 0/ Ike A„u;;cu„ Medicll A^socicitian Stoney's Bacteriology and Technic '^New (2d) Ed!'' Bacteriology and Surgical Technic for Nurses. By Emily M. A. Stoney, Superintendent of the Training School for Nurses at the Carney Hospital, South Boston, Mass. Revised by Frederic R. Grif- fith, M.D., Surgeon, -New York. i2mo of 278 pages, profusely illus- trated. Cloth, ^1.50 net. " These subjects are treated most accurately and up to date, without the super- fluous reading which ,s so often employed. . . . Nurses will find this book of the greatest value."— 7/if Jruincd Nurse and Hospital Review. Clarkson's Histology A Text-Book of Histology. Descriptive and Practical. For the Use of Students. By Arthur Clarkson, M. B., C. M. Edin., for- merly Demonstrator of Physiology in the Owen's College, Manchester, England. Octavo, 554 pages, with 174 colored original illustrations. Cloth, I4.00 net. "The volume in the hands of students will greatly aid in the comprehension of a subject which in most instances is found rather diflicult . . . The work must be con- sidered a valuable addition to the list of available text-books, and is to be highly recommended." — New York Medical Joitrnal. Gorham's Bacteriology A Laboratory Course in Bacteriology. For tlie Use of Medical, Agricultural, and Industrial Students. By Frederic P. Gorham, A. M., Associate Professor of Biology in Brown University, Providence, R. L, etc. i2mo of 192 pages, with 97 illustrations. Cloth, ^1.25 net. " One of the best students' laboratory guides to the study of bacteriology on the market. . . The technic is thoroughly modern and amply sulficient for all practical purposes." — American Journal of the Medical Sciences. Raymond's Physiology Ned"(3d)Td1tio„ Human Physiology. By Joseph H. Raymond. A. M.. M. D., Pro- fessor of Physiology and Hygiene, Long Island College Hospital, New York. Octavo of 685 pages, with 444 illustrations. Cloth, ^3.50 net. "The book is well gotten up and well printed, and may be regarded as a trust- worthy guide for the student and a useful work of reference for the general practi- tioner. The illustrations are numerous and are well executed." — The Lancet, London. i6 BACTERIOLOGY, PHYSIOLOGY, AND HISTOLOGY. Ball's Bacteriology Recently Issued— Fifth Edition, Revised Essentials of Bacteriology : being a concise and systematic intro- duction to the Study of Micro-organisms. By IM. V. Ball, M. D., late Bacteriologist to St. Agnes' Hospital, Philadelphia. I2mo of 236 pages, with 96 illustrations, some in colors, and 5 plates. Cloth, ^i.oo net. In Saunders^ Question- Co7iipend Series. "The technic with regard to media, staining, mounting, and the like is culled from the latest authoritative works." — The Medical Times, New York. Bud^ett's Physiology Essentials of Physiology. Prepared especially for Students of Medicine, and arranged with questions following each chapter. By Sidney P. Budgett, M. D., Professor of Physiology, Medical Depart- ment of Washington University, St. Louis. i6mo volume of 233 pages, finely illustrated with many full-page half-tones. Cloth, ^i.oo net. In Saunders^ • Question- Compend Series. " Contains the essential facts of physiology presented in a clear and concisf manner," — Philadelphia Medical JouniaL i^GTOy^S fiistolO^ second Edition, Revised Essentials of Histology, By Louis Leroy, M. D. , Professor of Histology and Pathology, Vanderbilt University, Nashville, Tennessee. i2mo, 263 pages, with 92 original illustrations. Cloth, ^i.oo net. /n Saunders^ Question-Coifipend Series. " The work in its present form stands as a model of what a student's aid should be ; and we unhesitating'ly say that the practitioner as well would find a g^lance through the book of lasting benefit " — The Medical World, Philadelphia, Bastin's Botany Laboratory Exercises in Botany. By the late Edson S. Bastin, M. A. Octavo, 536 pages, with 87 plates Cloth, ?2.oo net. Barton and Wells' Medical Thesaurus A The.saurus 01' Medical Words and Phrases. By Wilfred M. Barton, M. D., Assistant Professor of Materia Medica and Therapeu- tics ; and Walter A. Wells, M. D. , Demonstrator of Laryngology, Georgetown University, Washington, D. C. i2mo, 534 pages. Flexible leather, $2.50 net. - . _ 1 , •TV .• Fourth Edition, Revised American Pocket Dictionary Recently issued American Pocket Medical Dictionary. Edited by W. A. Newman Dorland, M. D., Assistant Obstetrician to the Hospital of the University of Pennsylvania. Containing the pronunciation and defi- nition of the principal words used in medicine and kindred sciences, with 64 extensive tables. Handsomely bound in flexible leather, with gold edges, ^i. 00 net; with patent thumb index, $1.25 net. " I can recommend it to our students without reserve." — J. H. Holland, M. D., Dean of the Jeffersoyi Medical College ^ Philadelphia. Saunders' ComDends SAU ^ERS' Question Compends, arranged in questiori- ahd-answer form,, are the latest, most complete, and best' illustrated series of compends ever issued. They are now recognized as the standard authorities jn medical literature with students and practitioners in every city of the United States and Canada. Since the first appearance of these fn- valuable student-helps there" have been sold over 250,000 copie^. The entire series has been kept thoroughly revised and enlarged when necessary, many of j:hem being iir their fifth and §ixth editions. A COMPLETE LIST OF VOLUMES ■ / Cloth, $ 1 .00 net per copy, unless otherwise noted 1. ESSENTIALS OF PHYSIOLOGY. A new work. By Sidney P., BUDGETT, M.D. 2. ESSENTIALS OF SURGERY. 7* ed. 90 illustrations. By Edward Martin-, M.p. 3. ESSENTIALS OF ANATOMY. 7th ed. 151 iUustrations.:, By ^ C. B, Nancrede, M.D. 4. ESSENTIALS OF MEDICAL CHEMISTRY. 6th ed. By Law- rence Wolff, M.DJ Revised by A. Ferree - Witmer, Ph.D. ■ , 5. ESSENTIALS OF OBSTETRICS. . 4* ed. 75 illustrations. By W. Easterly AShton, M.D. ,' ' - 6. ESSENTIALS OF PATHOLOGY AND MORBID ANATOMY. •\ ' By H. Harlow Brqoks, M.D. A newimrk. Preparing. 7. ESSENTIALS OF MATERIA MEDICA, THERAPEUTICS, AND PRESCRIPTION-WRITING. 6th ed. By Henry , Morris, M.D. Revised "by W. A. Bastedo, Ph.G., M.D. • 8,9. ESSENTIALS OF PRACTICE OF MEDICINE. By W R. WiLLiAMSj M.D. (Double number, iSl.7S net.) (Continued on Opposite Page) Saunders' Compends ia. ESSENTIALS OF GYNECOLOGY. S* ed. With 62 illustra- tions. By Edwin B. Cragin, M.D. 11. ESSENTIALS OF DISEASES OF THE SklN. 6th edition. 61 illustrations. By H. ,W. StelwagOn, M.D. ' 12. ESSENTIALS OF MINOR SURGERY, BANDAGING, AND VENEREAL DISEASES. 2d ed, 78 illustrations. By Edward Martin, M.D. ' ' 14. ESSENTIALS OF -DISEASES OF THE EYE. 3d ed., illus- .'-trated,- By Edward Jackson, M.D. f5. ESSENTIALS OF DISEASES OF CHILDREN. 3d ed. By Wm. M. POWEf.L, M.D, 17. ESSENTIALS OF, blAGNOSIS. 2d ed. By S. SoLis-CoHEfj, M.D., and. A. A. EsHJtER, M.D. -^ 19. ESSENTIALS OF NOSE AND THROAT. 3d ed., illustrated. ByE, U GleAsoN, M.D. ^ 20. ESSENTIALS OF BACTERIOLOGY. Sth ed. 96 illustrktions and 6 plates. By M. V. Ball, M.D. Revised by Karl M.. ' , ' VOGEL, M.D.^ , . ■ - - 21. ESSENTIALS OF NERVOUS DISEASES AND INSANITY. 4th ed. 53 illustrations. By John C. Shaw, M. D. , Revised by Smith Ely Jelliffe, M. D. 22. ESSENTIALS OF MEDICAL PHYSICS, zd.ed. By Fred. J. Erockway, M. p. ,,- ' 23. JESSENTIALS OF MEDICAL ELECTRICITY. By D, D. ' Stewart, M.D.', and E. S. Lawrance,. M. p. ' '' 24. ESSENTIALS OF DISEASES OF THE EAR. 3