96 ADVANCED PHYSIOLOGY 



with food is not necessary since the mere sight or smell of 

 food is all that is required to produce the result. The stom- 

 ach does not regulate itself; it acts only at the command of 

 the brain; Fig. 51. 



It is necessary, however, that the person be conscious, 

 or secretion will not occur. If food is put into the stomach 

 of a sleeping dog, no gastric secretion, and, therefore, n< 

 digestion occurs. Again, more is secreted when one'is hungry 

 than when one swallows food though not hungry. Pleasanl 

 tasting foods stimulate more active secretion than unpleasanl 

 and thus we can conclude that pleasing flavors, althougl 

 they may have no food value, may have a decided use 

 aids in digestion. 



Sometimes when a person's digestion is poor, so-callec 

 predigested foods are taken. These are generally proteit 

 substances which have been treated artificially with pepsii 

 obtained from the stomachs of pigs. This predigested foe 

 can be handled by the stomach more easily than ordim 

 food; but its use should not become a habit, for constant!; 

 aided in this way the stomach and other organs becoi 

 dependent on this assistance and lose their natural powers. 



Cold, as a rule, retards the action of any gland, muscle 

 or other tissue in the body, while heat, within limits, 

 favorable to their action. In the stomach the glands, togethei 

 with the nerves which control them, are so near the surfa( 

 that large quantities of cold food, like ice cream or ice water, 

 produce a shock which always delays their normal actioi 

 The distinct pain caused by too warm food or drink prevenl 

 us from harming ourselves in this way. It is interesting 

 to note in this connection that heat as such, is not fell 

 when food is swallowed; the sensation is one of pain only. 



The Passage of Food into the Intestine. The length of time 

 that food remains in the stomach varies with the kind of food, 

 but in the course of two to four hours after the average meal, 

 all foods have become a finely divided, slimy mass calle 



