UNIVERSITY OF CALIFORNIA SAN FRANCISCO LIBRARY OUTLINES DENTIST, PROFESSIONAL BUILDING, 07 1881 CHESTNUT ST., ROOM 71 PHiMDBLPHIA. COMPARATIVE ANATOMY AND MEDICAL ZOOLOGY. BY HARRISON i ALLEN, M.D., WOFESSOR OF ZOOLOGY AND COMPARATIVE 43A»*MT IN THK UNIVERSITY OF PENNSYLVANIA. SECOND EDITION. PHILADELPHIA: J. B. LIPPHSTCOTT & CO. 1874. Entered, according to the Act of Congress, in the year 1868, by HARRISON ALLEN, M.D., In the Clerk's Office of the District Court of the United States in and for the Eastern District of Pennsylvania. PREFATORY NOTE. IN the spring of 1866, a desire was expressed by the Class to have the author's Lectures on Comparative Anatomy and Zoology published for distribution. Nothing definite, however, was determ- ined upon until the following spring, when arrangements were en- tered into which have resulted in the appearance of this little volume. It is in many respects somewhat fuller than a synopsis, which, however, in general features, it resembles. Although pre- pared in answer to the expressed needs of a class composed chiefly of Medical Students, it is hoped that it may not be without value to the cultivators of rational anatomy elsewhere. In the attempt, apparent in different portions of the book, to frame general definitions and give brief classifications of anatomical sys- tems, the author is fully aware of the liability to error thus incurred. Any conclusions based upon the present state of a science so ac- tively cultivated as Comparative Anatomy may eventually prove of but doubtful utility. It is easy to group about assumed stand- points the observations of others, but more difficult to preserve in such arrangements harmony between the old and new facts. In (Hi) iv PREFATORY NOTE. proposing such, the author has been actuated by a sincere desire to simplify a confessedly intricate subject. In conclusion, he would desire to express his acknowledgments to Dr. George H. Horn for the contribution of the articles on Hemip- tera and Cantharis ; as well as to Professors Joseph Leidy, Ed- ward D. Cope, and Horatio C. Wood, Jr., for assistance rendered while the work was passing through the press. CONTENTS. COMPAEATIYE ANATOMY. MM PEZFATORY NOTE 6 I. Introduction 9 Elements of structure 9 Organism 10 Distinctions between vegetables and animals 11 Division of functional labor 12 II. Classification 13 Plan of star 15 Sac 17 Ring 19 Vertebra 20 III. Skeleton 23 Nature of limbs in Vertebrata 81 Table of elements of cranial vertebras 34 IV. Articulation 35 V. Apparatus of motion 36 VI. Teeth 38 VII. Digestive system 44 VIII. Circulatory and respiratory systems 62 8 trim bladder 60 Relation of branchial arches to stylo-hyoid ligament 61 Spleen 63 Lymphatics 64 IX. Excretory system 64 Kidney 66 X. Integument 68 XI. Nervous system 72 XII. Animal electricity and phosphorescence 82 Torpedo 82 Gymnotus. 83 Malapterurus 84 Animal phosphorescence 86 (v) VI CONTENTS. PAGE XIII. Special organs 87 Lasso cells 88 Organs of touch 88 Organs of smelling 91 Eye 92 Appendages to the eye 95 Ear 96 XIV. Sexual characters 101 XV. Reproductive system 103 Sperm cell 103 Ovum 104 Organs of generation 109 Testicle. 109 Ovary 109 XVI. Generation 120 Mammary gland 135 MEDICAL ZOOLOGY, Mammalia 137 Moschus 137 Viverra 139 Castor 139 Hyrax 141 Catodon 142 Reptilia 143 Caudisona 143 Crotalus 113 Ancistrodon 144 Vipera 144 Cerastes 144 Naja 144 Hydrophis 145 Pisces 145 Gadus 145 Acipenser 145 Insecta 147 Cantharis 147 Acanthia 151 Notonecta 152 Nepa 153 Aphis , 153 Coccus 153 Apis 154 Cynips 155 CONTENTS. Vll PAGE Pulex 156 Pediculus 156 Arachnida 157 Sarcoptes 157 Demodex 158 Myriapoda 159 Scolopendra 159 Annelida 159 Hirudo 159 Entozoa 161 Nematoidea 161 Trichina 161 Strongylus 162 Trichocephalus 162 Ascaris 163 Oxyuris 164 Sclerostoma 164 Dracunculus 164 Eustrongylus 165 Trematoda 165 Fasciola 165 Distoma 166 Bilharzia 167 Tetrastoma 168 Hexathyridium 168 Development of trematoda 168 Cestoda 169 Taenia , 169 Bothriocephalus 171 Development of Cestoda 172 Mollusca 174 Sepia 174 Protozoa 174 Infusoria 174 Virgulina 174 Vibrio 174 Paramecium 175 Cercomonas 175 Trichomonas 175 Psorospermice 175 Gregarinidae 176 Spongia 177 A-dditions 178 TABLE or CLASSIFICATION 179 INDEX... ,. 185 COMPARATIVE ANATOMY. i. INTRODUCTION. ELEMENTS OF STRUCTURE. THE composition of all bodies is either inorganic or organic. An inorganic (mineral) body is homogeneous in structure, and is either crystalline or without definite form. Its increase results from external accumulation of particles. An organic body is a product of organization. An organized body (organism) is heterogeneous in structure, and has a definite form. Its increase results from nutritive processes carried on within. Every organized body is composed of ultimate and proxi- mate physical elements. THE ULTIMATE PHYSICAL ELEMENTS are (1) homogeneous liquid, — as in the germinative area of the egg immediately after impregnation ; (2) homogeneous granules, — as in Monas crepusculum ; (3) homogeneous filaments, — as in cilia, sper- matic filaments, and Vibrio; (4) homogeneous membrane, — as in basement membrane. (Leidy.) THE PROXIMATE PHYSICAL ELEMENTS result through union of the ultimate elements. They are very constantly pro- nounced in varieties of the organic cell, of which it is conve- nient to speak, as an early, though not a primordial, expres- sion of form. As usually described, the organic cell is a minute form, composed of homogeneous membrane with intervening (9) 10 COMPARATIVE ANATOMY. spaces occupied with homogeneous liquid. Three concen- tric spheres can commonly be detected : the first (nucleolus) placed within the second (nucleus); the third (cell wall) en. closing the other two. Homogeneous granules appear within the liquid, and filaments (cilia) may be appended to the cell wall. FORMS OF CELLS are round, oblong, elongate, cylindrical, compressed, polygonal, and stellate. Surrounding conditions and position determine shape. PROPERTIES OF CELLS. — In addition to the nutritive pro- cesses common to all organisms, may be mentioned fissura- tion and motility. Relations of cells to histogenesis lead to consideration of origin and significance of cells. 1st Theory. — Cells originate spontaneously in a homoge- neous fluid, in the form of granules (nucleoli). Around these granules are subsequently developed others assuming the form of the remaining constituents of the cell, to be recog- nized as the nucleus and cell wall. (Schleiden and Schwann.) 2d Theory. — Omni ceUulce e cellula. (Virchow.) 3d Theory (generally known as the germinal theory). — The terminology of the cell is discarded, and the phrases "ger- minal matter" and " formed matter" substituted. The former is a structureless plastic substance everywhere pervading organized bodies, to which the formed matter stands in the relation of an evolved substance. (Beale.) ORGANISM. All organisms are sexual beings, and are, for the most part, composed of cells. Many inferior organisms assume the form of cells, as Amoeba* and Bodo. The ovum, apparently a cell, is in re- ality an undeveloped organism. The difference between a * Amoeba, one of the lowest of Rhizopoda, — composed of sarcode, with an outer structureless diaphanous integument, and containing an interior circular contractile vesicle. Measurement, from ^ to 2 ^ 5" long. Is found in stagnant water. INTRODUCTION. 11 cell and an organism can be determined only by tracing out the life-history in each. DISTINCTIONS BETWEEN VEGETABLES AND ANIMALS. Many attempts have been made to separate vegetables from animals. The cell being common to both groups, attempts have been made to separate them by its means. A sphere of homogeneous membrane intervening between nucleus and wall of the vegetable cell, not peculiar to it; an analogous membrane is seen in cartilage cell. There is no difficulty in separating high plant from high animal, as, for example, a horse from a tree; but acknowl- edged difficulty in distinguishing low forms, as a sponge from a Protococcus, an Am&ba from an (Ethalmm. But, as a rule, confusion obtains not so much among the very lowest forms of animal and vegetable life, as, for example, between Rhizopoda and Protophytse, as it does between others higher in the scale, as between certain Infusoria and Fungi, as the Myxomycetes. Linnaeus' definition: "Stones grow; plants grow and live; animals grow, live and feel." Objections. — Stones do not grow, but increase in size by accretion. Feeling may be said to exist in the lower classes of both plants and animals, provided that contractility be accepted as a property of sensitive tissue. If it be surmised that pain is a result of feeling (i. e. sensation), it may be attributed to CEthalium with equal propriety as to Amoeba. Were every act of fissuration, evisceration or amputation accompanied with pain, it becomes difficult to understand why self-mutila- tion should be so frequently imposed for the preservation of both individual life and that of the species (see p. 120). It is probable that at such times an organism feels no more pain than is experienced by the contractile contents of an ovum undergoing segmentation. Among the attempts which have been made to separate plants from animals, may be mentioned the following — placed, for convenience, in the form of propositions and ob- jections: 12 COMPARATIVE ANATOMY. Prop. 1st. That while plants inspire carbonic acid they expire oxygen — the process being reversed in animals. Obj. Plants, in absence of sunlight, or in times of flowering, ex- hale carbonic acid. Prop. 2d. That plants do not possess cilia — animals do. Obj. Many zoospores of plants arc ciliated. Entire groups of animals, as higher articulates and osseous fishes, are without them. Prop. 3d. That plants are without stomachs — all animals possess stomachs. Obj. The amoeboid stage of development of (Ethalium has a stomach in the same sense as Amceba; while Tcenia (tapeworm) is without a stomach. Prop. 4th. That plants have cellulose and starch as chemi- cal constituents of tissue — animals have not. Obj. The mantle of the Tunicata contains cellulose ; the ventricles of human brain contain starch granules. Prop. 5th. That plants are stationary — while animals are contractile and motile. Obj. Many plants have active con- tractile zoospores, and Volvox globator and the Diatomaceae are essentially motile. We cannot, therefore, well express the difference between a plant and an animal.; but can only ascertain the position of each disputed form by contrasting the sum of its life-phases with that of acknowledged types, as determined by develop- ment and sexual condition. Contrasts between animals arise from the variety of methods by which the processes of life are performed. In the Amoeba these processes are carried on in a common tissue (sarcode), so that at different times the same structure is sub- servient to different uses. But among the higher animals, which have many tissues, each organ has a limited functional power ; the degree of such limitation bearing a fixed relation to the multiplicity of organs, so that in the highest animals each organ has but a single function to perform. Indee'd, every animal, it is thought, has its tissues so specialized that the degree of its specialization is expressive of its position in the class to which it belongs. CLASSIFICATION. 13 This leads to the following law : The successive degrees of development attained by the animal kingdom depend upon the extent to which functional labor is divided. II. CLASSIFICATION, CLASSIFICATION is the arrangement of objects into groups, the limitations of which are determined by some precon- ceived standard of comparison. Classifications are artificial or natural, as the standard chosen is either false or true. Thus the classification of ani- mals, according to Aristotle, is artificial, since the standard assumed, viz., the coloration of the blood, is false. An arti- ficial classification is the result of an imperfect knowledge of the things classified. It is only by an intimate acquaintance with the anatomy,, physiology, and development of each animal, that wet can* determine in what tissues, and at what time, the true stand-- ard for comparison exists. As a rule, the hard tissues, such, as the shell, bone, teeth, scales, etc., furnish excellent second- ary characters; yet in sub-groups of Vertebrata, soft tissues^ as the blood and brain, afford reliable data. Sexual char* acters are occasionally of value, as the mammary gland, in, Mammalia, and, in a less degree, the construction of the penis in the same class. The male, in Vertebrata, conveys the expression of potentiality of species; in lower types, it is< subordinate. Maturity very generally yields the true standard of com** parison. Yet examples are not rare where it is best seen ia the young. The articulated condition of Lepas (barnacle) is* noticed only in the larval stage of the animal. The chorda dorsalis — the distinctive feature of the Vertebrata — disap^- pears (hi comparatively few instances only is it persistent,, viz., Cartilaginous fishes) before birth. 14 COMPARATIVE ANATOMY. The early condition of the embryo itself may determine the position of the animal. Thus in contrasting the early stage of the developing egg of an articulate with that of a vertebrate animal, it can be ascertained before the appear- ance of rings on one hand, or chorda dorsalis on the other, to which type the animal belongs. In the first, the embryo presents serrated borders, and is without a median groove; in the second, there is a median grove, but no lateral ser- rations. Apart from the application of the general law (p. 1 3), the inferiority of an animal within its group can be determined either (1) by the repetition of parts, or (2) by the permanency of embryonic conditions. (1) The tentacles and partitions of Actinia are indefinitely repeated throughout life; they are reduced to a fixed number — eight — in Alcyonium: therefore Actinia is a lower form of polyp than Alcyonium. In like manner Gammarus (fresh-water shrimp), a crustacean articu- late, from the repetition of its segments, is a type inferior to Lupa dicantha (crab), where they are consolidated toward ithe anterior extremity of the animal. (2) Upon observing .among acaleph radiates that the genus Hydra corresponds in form to the first larval change of the Aurelia (SQQ p. 126), Hydra is said to be a lower form than Aurelia. In perceiving that a canal of communication between an arterial and venous .current (foramen of Botal) obtains in the systemic circulation of the reptile, while such a condition is peculiar to the foetal circulation of the mammal, the reptilian type is said to be •lower than the mammalian. When the relations of closely allied animals are sought for, the characters are selected not so much from their phy- siological importance as from their constancy. Indeed, the most important vital organs with some groups of animals may furnish no characters for classification — as, for example, the heart in insects; while others having no apparent sig- nificance, such as minute differences in form and number of joints of antennae, may be of the greatest value. Systems of classification change with increase of knowl- edge, and, all things being equal, the latest is the best. But CLASSIFICATION. 15 it appears probable that the present classification will never be materially altered. The main features are for the most part defined with clearness. As a result, a number of plans or types of structure are seen in the animal kingdom — each plan or type being taken as the standard of comparison for all animals included -within its limits. To these ideal pat- terns the tissues more or less regularly conform. If they have the significance by many attributed to them, namely, in each being the expression of a divine idea, it follows that the great principles of classification are fixed. These plans are four in number, and are arranged in ac- cordance with the capacity possessed by each for develop- ment, as follows: STAR. SAC. RING. VERTEBRA. In that large group, the Protozoa,* no plan or plans have yet with certainty been recognized. STAR (Radiata). A radiate animal is one having its parts disposed around a common central axis, and diverging from it to the periph- ery. (Agassiz.) Divided into groups of Coelenterata and Echinodermata. Ccelenterata subdivided into Polypi and Acalephse. * PROTOZOA. This term was proposed by Siebold to designate a group of animals, characterized by the various systems of organs not being distinctly separated. (Griffith in Micrograph. Diet.) Divided into Rhizopoda, Spongida, and Infusoria. Rhizopoda. — Essential characters are the gelatinous composition of the body, and the locomotive organs consisting of variable foot-like processes (pseudo-podia\ (Griffith, ibid.) Spongida. — Fixed, aquatic, polymorphous animals; inhaling and imbibing the surrounding element through numerous contractile pores situated on the external surface; conveying it through internal canals or cavities, and ejecting it through appropriate orifices; having an internal flexible or in- flexible skeleton. (Bowerbar.k.) Interior mass occupied with numbers of chambers lined with flagellate cell-like bodies (Carter.) Infusoria. — Form variable, fixed or free, round, oval, etc., with integument furnished cither with a ciliated spiral line, or a single flagellum. Interior mass slightly specialized ; a gullet and contractile vesicles making theii appearance. 16 COMPARATIVE ANATOMY. Polypi. — Composed of a sac divided into chambers by partitions arranged to the periphery (integument), as radii to- a central point — the stomach. Such partitions maybe more, though never less than six in number. "The upper margin of body is fringed by hollow tentacles, each of which opens into one of the chambers." They may be naked and present indefinite numbers of partitions and tentacles., as in A ctinia (sea-anemone); or possess a definite yet large number of tentacles often accompanied with depositions of calcareous matter within walls between partitions, as in Madrepora (coral); or the tentacles may be restricted to six, with a tend- ency to formation of calcareous skeleton, as in Alcyonium. Acalephse. — This is a numerous and diversified group, com- posed for the most part of individuals, which, when mature, have a dome or umbrella-like form. The organs and systems of vessels are arranged in a stellate manner to a central point. Divided into Ctenophorse, Discophorse, and Hydroida. Acalephs move by means of minute flappers arranged in vertical comb-like rows on outer side of the dome-like struc- ture, as in Ctenophorse; or through the movements of the edges or general contractile power of the Discophorse and Hydroida. In the last two groups, remarkable features are seen in the development of the young, the larval condition, as a rule, remaining fixed and dissimilar in form to the adult. (See p. 124.) Echinodermata. — This is the highest group of radiates, composed of stellate globular or oblong forms, rarely fixed, and possessing, with the exception of one group, a system of foot-like processes (ambulacra), which may be inflated with water through ambulacral vessels, communicating by means of a peculiar canal (madreporic body)* with the ex- terior. The spaces between the ambulacral pores are the ambulacral spaces. The majority of Echinodermata are more or less enclosed * So called from the resemblance its sieve-like opening bears to a polyp chamber of Madrepora. CLASSIFICATION. 17 by a complicated system of calcareous plates, giving a rigidity to the general form of the animal. The plates constituting the dorsal system may be very numerous and complicated, so as to form a stem by which the animal is invertedly attached to the ground, while the ambulacral system may be limited to a comparatively small area, and the interambulacral system is wanting, as in Coma- Ma (sea lily); the dorsal system, though large, may not form a stem, yet fold over on the under side of the animal so as to enclose entirely the ambulacral system, forming a kind of shield to the bases of the long snake-like arms, as in Ophio- pholis ; the system may occupy the back of the animal, but not to enclose the ambulacral suckers which find their way between the rows of small plates along the under side of the arms, as in Asteracanthion (star fish); the system may be* contracted to a small area on the top of the animal, the row* of interambulacral plates which are separated and lie on-< either side of the ambulacra in the star fish may now be united, and both ambulacral and interambulacral systems. bent upward, meeting in a small dorsal area above, as in TOX+- opneustes (sea urchin); or the ambulacral and interambulacral systems may take a great preponderance over the dorsal sys- tem, the latter being pushed out to the end of a cylinder, while the two former ran along its whole length, as in Holo* ihuria (sea cucumber). — (E. C. & A. Agassis.) SAC (Mollusca). A mollusc has the stomach and viscera enclosed by a fleshy sac. Principal nerve masses, consisting of ganglia, which are adjacent to, or surround the oesophagus. Intestine bend^- ing inward, or having an outward flexure. Heart on outer- side of intestine. (Morse.) Divided into Polyzoa, Brachiopoda, Tunicata, Lamellibran^ chiata, Gasteropoda, Pteropoda, and Cephalopoda. Polyzoa. — Compound molluscs. Respiratory apparatus; exsertile from sac in the form of ciliated tentacles around mouth. Intestinal canal definite, curved upon itself. Single ganglion situated at re-entering angle. Heart, none. Brachiopoda. — Animals solitary. Mantle covered by Mr- Si 18 COMPARATIVE ANATOMY. valved shell, arranged antero-posteriorly to body. Respira- tory apparatus in the form of two long, ciliated tentacles. Alimentary canal curved upon itself, and either ends blindly in the middle line or else terminates in a distinct line be-* tween lobes of mantle. (Huxley.) Nervous ganglion placed within the re-entering angle of intestine. Vascular system imperfectly understood. An atrial circulation, or movement of water within system of communicating chambers, is well developed. Tunicata. — Compound or single molluscs. Respiratory apparatus included within mantle. Gullet commences from the base of this branchial chamber. Endostyle* present. The intestine is curved upon itself and terminates at anal aperture, which is always situated within a chamber opening externally by a second aperture upon mantle. The nervous ganglion not placed within entering angle of intestinal fold. Heart of simple'form always present. Atrial system present