THE ALIMENTARY CANAL 59 



stomach. At the left side of the body and near the spleen 

 the descending colon begins. Its course is downward 

 and backward, so that it passes behind the coils of the 

 small intestine. Following the dorsal boundary of the 

 cavity around to the middle line, the colon forms the short, 

 curved region called the sigmoid flexure. The remaining 

 section is the rectum, situated directly in front of the lower 

 extremity of the spinal column within the pelvis and ter- 

 minating at the anus. 



Almost everywhere the lining of the alimentary canal is 

 pitted with microscopic glands. Those in the stomach 

 furnish the gastric juice; those in the intestine, the intesti- 

 nal juice. Besides these small glands and the salivary 

 glands already mentioned, there are the pancreas and the 

 liver, contributing secretions to the cavity of the digestive 

 tract. The pancreas has been said to lie in the turn of the 

 duodenum. It is thus under the pyloric portion of the 

 stomach and behind the transverse colon. Its main duct 

 discharges into the small intestine about 3 inches below the 

 pylorus. A second, but very small, duct opens close by. 

 The liver, which is the largest gland in the body, is fitted 

 to the concave under surface of the diaphragm and is 

 mainly to the right of the midplane. It is cleft into several 

 lobes, from which ducts converge and unite as they ap- 

 proach the duodenum. A single duct is finally formed and 

 it enters the intestine at the same point as the chief pan- 

 creatic duct. The arrangement serves to blend the two 

 secretions, and is somewhat suggestive of the devices used 

 with bath-tubs for mingling hot and cold water. 



The liver produces bile, and its channel of discharge to 

 the duodenum is accordingly known as the bile-duct. 

 This duct has a side branch which leads to a contractile 

 sac embedded in the under surface of the liver, this reser- 

 voir being the gall-bladder. Bile, as it flows down from 

 the liver, may either find its way directly to the intestine 

 or it may turn aside into the gall-bladder. The course 

 taken will depend on the contraction and relaxation of the 

 muscular walls of the ducts. Active contraction of the 



