Injected and dissected so as to show the manner in which the viscera are arranged in situ.
The following external characters, for the most part discernible in this specimen, should be noted: - the absence of limbs: the transparent cornea-like structure covering the eye formed by the union of the eyelids: no external mark indicating the position of the ear: the slight furrow between the two rami of the lower jaw permitting the free extrusion of the tongue when the mouth is closed. In these points as well as in the total loss of the shoulder-girdle Ophidians differ from Lizards, but they agree with them in having the cloacal aperture transverse and a complete investment of scales. These scales, with the exception of those upon the head overlap one another. They are processes of the dermis with an epidermis, the outer layers of which are thick and horny. These layers, together with the outer coat of the fused eyelids and the labial organs of sense, are moulted periodically, apparently at intervals of one month, during the active summer life of the animal. There are three types of scales: the flat plates of the head with apposed edges: the series of broad ambulatory ventral scales extending from the throat to the divided scale which protects the cloaca: and the triangular scales of the body, smallest, and strongly keeled near the median dorsal line.
The Harderian gland of the eye and the labial glands of the mouth have been exposed by the removal of the skin. The lobed extremity of the former appears behind the eye: it extends below that organ and opens by a single duct at the inner angle. The true lacrymal gland which lies above the eye is absent in Serpents but present in Lizards, e. g. the Blind-worm. The labial glands of the upper jaw are divisible into two kinds, readily distinguishable in the freshly killed animal. The first kind is grey in colour and forms (1) the azygos rostral gland lying upon the praemaxillae and not exposed here, and (2) a series of composite glands, each with its own duct extending back to the angle of the gape. The second kind is naturally white, but assumes a yellow colour in spirit preparations. It is large, and opens by a single duct between the maxillary teeth, and is the homologue of the poison gland in the Viper. The glands of each ramus of the lower jaw form an unbroken series and are grey in colour.
The integument has been divided in the median ventral line as far as the prae-cloacal scale, and then reflected to the right and left. The dark-coloured tongue formed by the hyoglossi muscles extends backwards from the chin. On either side of it is a white rod, generally considered to be the larger cornu of the hyoid bone. The common jugular veins lie to the outer side of these rods. They rise into view at the angle of the mandible, and the right vein is well displayed in its whole course, the left only close to the heart. The trachea is seen externally to the right jugular close to the heart. This portion of it is dilated and marked by irregular ridges: the first portion lies dorsally to the tongue and has complete rings. The oesophagus, at first dorsal to the trachea, passes to the left side of the body where it becomes visible close to the heart. It dilates gradually into the stomach. Between the two jugular veins, and close to the heart, is the thymus gland, and between the latter and the heart three vessels are visible, one in front, the left aorta, one difficult to see in the middle, the carotid, and a third passing to the right, the right aorta. The left aorta reappears at the outer side of the left jugular vein, embracing the oesophagus.
This organ is twisted to show the dorsal junction of the two aortae, beneath which a black bristle has been passed. The dorsal aorta in Snakes is not closely tied to the backbone as it is in other Vertebrata.
The pericardium has been cut away. The right auricle is large and has its wall removed to show the right auriculo-ventricular aperture. The left auricle is small and is crossed by the left jugular vein. The ventricle touches the small and rudimentary left lung, and rests upon the large and long right lung which lies behind the liver. Crossing the ventral surface of the right lung is the vena cava inferior, accompanied by the pulmonary artery which lies to its outer side. The liver is long and unilobar. A furrow on its outer surface lodges the vena cava inferior. The gall-bladder is large, and lies about a half inch from the posterior end of the liver. It is bent sharply upon its duct, beneath which a piece of blue paper has been passed. This duct and the bile duct unite inter se, and with the pancreatic duct in the substance of the pancreas, a globular gland lying on the intestine close behind the gall-bladder. The first portion of the intestine is straight, but from the pancreas onwards it is disposed in short abrupt coils. These are supported by a mesentery, but the peritoneal coat does not follow every turn of their course as is usual, but passes from the end of one coil to the end of the next succeeding.
The coils are closely united by connective tissue.
The lobed fat body commences about the level of the pancreas. It is fastened out on the animal's right side; the branches of a vessel, the remnant of the epigastric vein, may be seen here and there among its lobes. The vessel in question joins the portal vein. About four inches from the liver is the right ovary with a single row of ova, and between it and the fat body is the vascular oviduct. The left ovary and oviduct have similar relations on the left side, but are placed more posteriorly. The same asymmetry is visible in the position of the two kindeys, organs consisting of a number of leaf-like lobes placed one behind the other. Close to the cloaca, the large intestine is seen lying between the two oviducts. It has been opened and a black bristle passed through it into the cloaca. The left oviduct has a white bristle similarly inserted into it. The skin and muscles behind the cloaca have been removed to show the two sacs, homo-logues of the two eversible sacs or intromittent organs of the male.