. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Vitelline apparatus of the Fetus of a Viper at a more advanced period, showing the Yolk partially entered into the Abdominal Cavity. a, the yolk-bag; b, the amnion; a', portion of the yolk-bag which lias passed through the um- bilical canal into the cavity of the abdomen; d, d, ductus vitello-intestinalis running forward to open into the intestine; g, continuation of intestinal tube; k, the kidney. Fig. The Embryo of a Viper Just before it is hatched, showing the Condition of the Vitelline System at this Period. Th
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Vitelline apparatus of the Fetus of a Viper at a more advanced period, showing the Yolk partially entered into the Abdominal Cavity. a, the yolk-bag; b, the amnion; a', portion of the yolk-bag which lias passed through the um- bilical canal into the cavity of the abdomen; d, d, ductus vitello-intestinalis running forward to open into the intestine; g, continuation of intestinal tube; k, the kidney. Fig. The Embryo of a Viper Just before it is hatched, showing the Condition of the Vitelline System at this Period. The letters a, c, g, h, I, indicate the same parts as in fig. 244.; b, remains of the vitelline sac, taken out of the abdominal cavity, iu which it had now become completely closed; d, the ductus vitello- iutestinalis shrank into a very short canal; /, f, the stomach; h, i, rudiments of the ovaria; k, the kidney. represented as they appear just before the egg is hatched, the vitelline sac being already completely introduced into the abdominal cavity ; the yolk of the egg, b, now reduced to a very small size, is now seen to commu- nicate with the intestine^ g, by the extremely short passage, d, to which the long ductus vitello-intestinalis, represented in Fig. 244., is now reduced. Tegumentary System.— In all reptiles the blood is cold, and the general temperature of the body corresponds with the imperfectly oxygenated state of the circulating fluid ; instead, therefore, of being clothed in hair or feathers, their bodies are invested with plates or scales of horny cuticle, better adapted to their manner and mode of life. In lizards the cuticular covering is cast off at intervals in small detached portions; but in serpents, where it forms a thin continuous stratum that envelopes the whole surface of the body, it is cast off in a single piece. Beneath the cuticle, the skin of reptiles presents the usual structure, consisting of the cerium, and of an interposed mucous layer, upon
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