STRUCTURE OF THE HUMAN BODY 37 



Other very important organs of the kind, the peptic or gastric 

 glands, are found as innumerable minute branching tubes opening 

 into the stomach, in the lining of which they are imbedded. The 

 fluid secreted by these glands is the gastric juice. 



The liver, which is the largest organ of the body, is, among 

 other things, a digestive gland. It is a bulky reddish-brown mass 

 placed in the upper part of the abdominal cavity, and its secretion, 

 the bile or gall, passes into the beginning of the small intestine 

 through a small thick-walled tube, the bile-duct. Connected with 

 this is a pear-shaped bag, the gall-bladder, in which bile can be 

 temporarily stored up. 



The last digestive gland of importance is the pancreas, popu- 

 larly known as the sweetbread, which lies in the first loop made 

 by the small intestine, and pours its secretion, the pancreatic juice, 

 through a short tube into the bile-duct. 



Process of Digestion. — The process o{ Digestion essentially 

 consists in the conversion of food into a dissolved or else a very 

 finely-divided state. It is effected partly in a mechanical, partly 

 in a chemical manner. 



1. Mechanical Digestion. — As regards mechanical digestion 

 an important part is played by the teeth, which reduce the food 

 to small fragments, this being rendered more easy by the pouring 

 out of saliva, which acts as a moistening and softening agent. 

 The muscular tongue and cheeks are also of importance here, 

 because they help to keep the fragments between the grinding 

 teeth. In gullet, stomach, and intestines a further division is 

 brought about as the result of a squeezing action exerted by the 

 muscle-containing walls of these organs. 



2. Chemical digestion is even more important. Within the 

 stomach abundant gastric juice is poured on to the digesting food 

 and acts more particularly upon the albuminoids, converting some 

 of them into a soluble form known as peptone. 



The saliva is concerned with starchy foods, which it converts 

 into a kind of sugar. 



Chemical digestion is completed in the small intestine by the 

 bile and pancreatic juice. The latter finishes the work on the 

 starchy and albuminous matters begun by saliva and gastric juice, 

 besides which it acts on fats, converting them into a milky state or 

 emulsion, where minute globules of the fat are suspended in fluid. 

 The bile helps in the digestion of fats, and is of importance in 



