Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/480

Rh REPTILES [ANATOMY. of the eye. A muscle arises from the surface of the sclerotic on its inner side and ends in a tendon which passes backwards and down- wards over the optic nerve to attach itself to the margin of the nictitating membrane. There is a rudimentary pecten. In the Chelonia the sclerotic is furnished with bony plates. The Harderian gland is small, but the lacrymal is considerable. There are three eyelids, and the nictitating one has the muscle which moves it combined with the elevator muscle of the eyelids. Both arise from the inner side of the sclerotic. One arches over the optic nerve and goes to the third eyelid, and the other goes from the outer angle of the eye to the lower eyelid. The fibres of these two muscles arc closely interrelated at their origin. Nasal The Olfactory Organ. There are two olfactory organs organ. f n every Reptile, consisting of tracts or foldings of mucous membrane richly supplied with nerves and supported and protected by cartilaginous or bony structures. In existing Eeptiles they always lie at, and extend near to, the anterior end of the muzzle, though in the Ichthyosauri and Plesiosauri they opened anteriorly far back and near the orbits. The olfactory membranes are always enclosed or supported by carti- lages which proceed out from an azygous septum which divides them one from the other. Each nasal organ has an anterior and posterior opening, though the anterior openings may so meet as to form but one superficial aperture, as in the Crocodilia, and the two posterior apertures may open, not directly into the mouth, but into an azygous forwardly-extending diverticulum from it, the posterior opening of which diverticulum forms practi- cally a common posterior termination for both the organs of smell. The nasal passages are short in all existing Reptiles save the Crocodilia, and open posteriorly far forwards as has been already noticed in describing the skull, when the prolongation backwards of the posterior nares in the Crocodiles was also described. In the Chelonia the anterior external apertures of the nostrils are distinct though near together. Sometimes, as in Chelys and Trionyx, they are tubular, and open externally at the end of a short proboscis. A structure called the nasal gland exists and is well- developed in the Ophidia. It is a peculiar rather soft body, often shaped like a mushroom with a very short stalk. It lies immediately beneath the floor of the nasal capsule, and the membranous Avail of the cavity on which it lies is covered and protected by a bone, commonly called the "turbinal," which extends out from the median nasal septum to the maxilla. These cavities open on the palate by narrow apertures placed in front of the posterior nares. In the- Chelonians we find a soft, egg-shaped, whitish, azygous body (without any internal cavity), also placed in front of the posterior nares in the skin of the palate, behind the palatine part of the premaxillas. It is supplied with palatine nerves. The Urogenital System. In Reptiles the urinary and generative systems are distinct, save as regards the approximation of their pos- terior terminations, thus agreeing with higher Vertebrates and differing from Amphibians, in which the renal and secreting organs generally continue throughout life more or less connected. Urinary The Urinary System. The urinary system of the Rep- system. tilia always consists of a pair of renal glands or kidneys, with excretory ducts which pass down to the cloaca. There may or may not be a urinary bladder, also opening into the cloaca. Besides these parts there are also a pair of Wolffian bodies, which are more or less aborted remnants of large organs which are always developed during embryonic life. The Kidneys. The kidneys are more or less symmetrically placed on the dorsal side of the peritoneum, in the hinder half of the trunk. Each consists of a mass of crecal tubules into the distal end of which a tuft of minute vessels projects, thus forming what is called a glomerulns or Malpighian body. In the Ophidia the kidneys are least symmetrical, the right one extending the farthest forwards. They are elongated and lobed, and sometimes in such a way as to appear spirally twisted. Each ter- minates behind considerably in front of the cloaca. The duct of each ureter begins at the anterior end of the kidney and thence proceeds along its inner border, and accessory ducts open into it from the interspaces of the lobes of the kidneys. The two ureters open into the sides of the cloaca. In the males each opens upon a papilla in close proximity to the opening of the male sexual duet or va's deferens. In the females the ureter opens beside the mouth of the female sexual duct or oviduct. There is never any urinary bladder. In Lacertilians the kidneys are more posteriorly placed than in Serpents. They lie at the hindmost part of the body cavity above the cloaca, and they generally much approximate together. They are also more symmetrically placed; only in the Amphisbaeniana the right kidney extends the more forward, thus resembling Ophidians. There is always a urinary bladder, which is a veutral diverticulum of the cloaca. The kidneys are usually transversely furrowed. The ureters run along the inner side of the kidneys, and open into the sides of the cloaca, not into the bladder. In Chelonians the kidneys lie near the cloaca in the cavity of the pelvis. They are rather short and thick, and more or less trihedral. Their surface is marked with many shallow meandering grooves and fewer deeper furrows. The ureters proceed as usual along the inner sides of the kidneys, and several large canals successively open from them into the ureters, which extend backwards, but to a trifling extent, beyond the kidneys. They open rather anteriorly into the cloaca close to the neck of the urinary bladder, which vessel is always present and voluminous, and is often two-horned. The Crocodilia also have posteriorly situated pelvic kidneys, but they have no urinary bladder. The kidney is concave dorsally and flatter ventrally. Its surface has meandering convolutions separated by furrows. The ureters for the greater part of their length run deeply sunk in the substance of the kidneys. The ureters leave the hinder ends of the kidneys and run freely for a short distance to the cloaca, which they enter close behind the rectum. The Wolffian Bodies. These bodies lie one on each side on the dorsum of the body cavity, and each consists of a series of crecal tubes with vascular balls or glomeruli like those of the kidney, the various tubes always opening at first into a common excretory duct which leads towards the cloaca. In adults they arc but small organs. In a Python 10 feet long they measure but about an inch. In Serpents generally they are slender and lobed bodies which lie close to the veins in front of the kidneys. The Generative Organs. Reptiles, like all the higher Vertebrates, have the sexes divided, with two sets of organs which respectively characterize male and female indivi- duals. In both sexes, as in Birds, there is a pair of sexual glands, each furnished with a passage for the exit of its product, together with, almost always, external organs destined to effect and facilitate impregnation. Unlike Mammals, however, all Reptiles have the sexual glands placed within the abdominal cavity, and, also unlike Mam- mals, the male external organ or agent for copulation may be either azygous or bifold according to the group to which any Reptile may belong. Unlike the more inferior Verte- brates, however, Reptiles, with the solitary exception of Hatteria, always possess such a copulating organ, and im- pregnation is invariably effected internally. The male organs consist of a pair of glands, the testes, with their ducts, the vasa deferentia, and the external organs, penis or penes. The female organs consist of a pair of glands, the ovaries, with their ducts, the oviducts, to- gether with rudimentary representatives of the external sexual organs of the males. The Testes and Vasa Deferentia. These are two compact and rather small glands, consisting of a mass of caecal convoluted tul >es, lying in the dorsal region of the abdominal cavity and completely invested by peritoneum, and with a dense albugineal coat of their own. From the mass of tubules a certain variable number of efferent tubes, vasa elferentia, come forth and soon unite in the single excretory duct of the gland, the vas deferens. In the Ophidia the testes are not symmetrically placed, the right one being somewhat more voluminous and also in front of the other. Consequently the right vas deferens is larger than the left one. Each testis lies in front of the kidney of its own side, and is more or less elongated in form. The vas deferens proceeds along the inner margin of the testicle, and is a convoluted tnl>u which narrows as it proceeds backwards. The opening into tliu