THE ALIMENTARY CANAL 



183 



entericus into the intestine. Their occurrence in the 

 lower divisions of the canal is less abundant than higher 

 up. The pancreas has a chief duct uniting with the 

 small intestine just below the pylorus. At the same 

 place the bile duct, bringing the secretion of the liver, 

 reaches an outlet. The two ducts practically come to- 

 gether in the act of entering the intestine. The spleen 

 has no duct and is not strictly a gland. 



FIG. 46. The principle of glandular structure. In the upper figure 

 a simple microscopic gland is supposed to be laid open by a section along 

 its vertical axis. The cells are seen to surround a recess into which they 

 discharge their secretion. Below, the same structure is shown in its 

 entirety, and in addition the encircling blood-vessels which contribute 

 to make good the losses suffered by the secreting cells. 



The Minute Structure of the Organs of Digestion. 

 The outer coat of the stomach and intestine has already 

 been mentioned, a continuation of the mesentery and 

 so of the peritoneum. This covers the muscular com- 

 ponent of the canal which is resolved, so far as the small 



