CHAPTER THIRD. 



THE NUTRITIVE SYSTEM. — SPLANCHNOLOGY, OR HISTORY 

 OF THE DIGESTIVE ORGANS. 



DEFINITIONS AND DESCRIPTIONS. 



290. Definition of Digestive Organs. — The Digestive Or- 

 gans are those which receive the food into the body and effect 

 such changes in it that the various tissues can be formed 

 from it by means of the glands. Of these organs the princi- 

 pal one is the Alimentary Canal. This commences with the 

 mouth, and includes the stomach, with the whole length of 

 tube known as the intestines. This canal, in a full-grown 

 man is about thirty feet in length, being as a general rule 

 five times the height of the individual, and is lined through- 

 out its entire length by mucous membrane. 



291. The Mouth; Salivary Glands; the Tonsils,— The 

 Mouth contains the organs of mastication including the teeth 

 and tongue, and receives the saliva, which is secreted by three 

 pairs of glands named Parotid, Submaxillary, and Sublingual, 

 situated just beneath and behind the lower jaw. Besides 

 these three glands there are many other minute glands and 

 follicles situated upon the floor and backsides of the mouth, 

 which secrete fluids that aid in mastication and digestion. 

 The Tonsils are simply an aggregation of follicles situated in 



290. What are Digestive Organs? Give the general description of the Alimentary 

 Canal. 291. What does the mouth contain ? Name the three principal pairs of glands 

 and give their location. 



