COMPARATIVE ANATOMY 51 



where the oesophagus enters; the pyloric end is the part where 

 the small Intestine begins. The lateral side of the stomach is 

 known as the greater curvature; the inner side is the lesser 

 curvature. The entrance to the small intestine is guarded by a 

 ring-like thickening, the pyloric valve (pyle, gate). 



Small Intestine. — The small intestine is divided into three 

 regions. The first part, the duodenum, begins at the pyloric 

 valve, runs posteriorly on the right side and then forward again 

 on the left side. The place where it turns posteriorly on the left 

 side is arbitrarily chosen as the end, although there is no distinct 

 line of division. The jejunum (meaning empty) is the much 

 convoluted part of the intestine following the duodenum and 

 extending for approximately twenty-five centimeters. Its limits 

 cannot be exactly defined. Its name refers to the fact that in 

 human cadavers it is usually found empty. The remaining 

 part of the small intestine, the ileum (eilein, to roll up), consti- 

 tutes about two-thirds of the whole. Observe the mesenteries 

 supporting it. The ileo-colic valve lies at the point where the 

 ileum joins the large intestine. 



Large Intestine. — The large intestine is composed of two 

 parts, the colon and the rectum. The colon is the enlarged por- 

 tion of the intestine into which the ileum enters. Near the 

 point of entrance of the ileum is a blind pouch, the caeciim. The 

 colon passes anteriorly, then to the left, and then posteriorly 

 again, forming roughly the ascending, transverse, and descending 

 colon. The rectum is assumed to begin where the descending 

 colon reaches the middle line and extends to the anus, which is 

 surrounded and kept closed by the sphincter ani muscles. Near 

 the anus are two small anal glands. Do not dissect the last 

 part of the rectum until the urogenital system has been studied. 



Spleen. — This is the dark red body lying along the greater 

 curvature of the stomach. It is a ductless gland associated with 

 the circulatory system and is not an organ of digestion. 



Liver. — This is the largest gland of the body. It is divided 

 into several lobes. The gall Madder lies partially embedded in 

 the liver. Cut away the free ends of the liver and dissect the 

 bile ducts. This requires care, patience, and technique, as the 

 ducts are covered with connective tissue which must be removed. 

 On the duodenum, about an inch from the pyloric valve, is a 



