90 



ALIMENTARY CANAL. 



CHAPTER V. 



OBSERVATIONS UPON THE ALIMENTARY CANAL AND DIGESTION 



OF ALBUMEN AND FLESH. 



In many cartilaginous fishes, as the Stingray {Trygon sabina), the extent of sur- 

 face over which the digested aliment is. spread, is increased by a spiral valve which 

 winds in close turns, from the pyloric to the anal extremity of the capacious intes- 

 tine. By this remarkable arrangement, the apparently short intestine possesses an 

 exceedingly enlarged surface of mucous membrane. 



Fig. 19 represents the viscera and impregnated uterus of a Stingray {Trygon 

 sabina), reduced to half its diameter. 



The intestinal canal of Ophidians, is but slightly convoluted; its length is gene- 

 rally about equal to that of the body. 



Fig. 21 represents the viscera of the Corn Snake ( Coluber guttatus), reduced to half 

 its diameter. 



Fig. 8. 



Viscera of Snapping Turtle (Chelonura serpentina), a carnivorous chelonian, reduced to one-half diameter. A. Ventricle 

 of heart. B. Auricle of heart. M, M. Liver. N. Stomach. G. Duodenum ; a small portion of the pancreas is 

 seen in contact with the superior surface of the duodenum. P, P, P. Small intestines, which suddenly expand into 

 the large intestine. 0. Large intestine, filled with shells of Crustacea, and fragments of grass and leaves. T. Rectum, 

 S, S. Testicles. Q, Q. Kidneys. II. Bladder, partially filled with light yellow urine ; the bladder communicates 

 with the cloaca. X. Divided extremity of the large intestine, called, at this position, the cloaca. 



