180 HUMAN PHYSIOLOGY 



When we take up the minute organization of these parts 

 we shall see that the usage is reasonable. Glands which 

 are placed distinctly away from the canal have ducts 

 leading to it for the discharge of their secretions. 



Three pairs of salivary glands contribute saliva to 

 the mouth. On either side there is a parotid gland below 

 and before the ear. Its duct runs forward to empty 

 on the inside of the cheek opposite the upper molar 

 teeth. The submaxillary gland is near the angle of the 

 jaw; it has a duct opening under the tongue close to its 

 fellow from the other side. At or near the same point 

 comes in the secretion of the small sublingual gland which 

 is under the floor of the mouth. 



Glands of a microscopic order discharge by openings 

 that may be spoken of as pores over the entire lining of 

 the stomach and intestine. They secrete the gastric 

 juice into the stomach and the intestinal juice or succus 

 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. 



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 

 intestine is concerned, into an outer layer in which the 

 fibers have a longitudinal direction and an inner and 

 thicker one in which they are transverse or circular. 

 The cells in these layers are of the smooth type (Chapter 

 IV). 



Inside the muscular coats there is more or less loosely 

 woven tissue rich in blood-vessels and nerves. Still 

 within this and next to the hollow of the canal is the 



