368 HANDBOOK OF PHYSIOLOGY. 



best of all stimuli. How it acts is unknown. Khigino believes that it 

 acts upon the afferent nerve-filaments in the stomach, and that the effect 

 is reflex. 



The influence of the higher nerve-centres on gastric digestion, as in 

 the case of mental emotion, is too well known to need more than a ref- 

 erence. 



Digestion of the Stomach after Death. If an animal die during the pro- 

 cess of gastric digestion, and when, therefore, a quantity of gastric juice 

 is present in the interior of the stomach, the walls of this organ itself are 

 frequently themselves acted on by their own secretion, and to such an 

 extent that a perforation of considerable size may be produced, and the 









Fig. 254. Auerbach's nerve-plexus in small intestine. The plexus consists of flbrillated sub- 

 stance, and is made up of trabeculae of various thicknesses. Nucleus-like elements and ganglion- 

 cells are imbedded in the plexus, the whole of which is inclosed in a nucleated sheath. (Klein. ) 



contents of the stomach may in part escape into the cavity of the abdo- 

 men. This phenomenon is not infrequently observed in post-mortem ex- 

 aminations of the human body. If a rabbit be killed during a period 

 of digestion, and afterward exposed to artificial warmth to prevent its 

 temperature from falling, not only the stomach, but many of the sur- 

 rounding parts will be found to have been dissolved (Pavy). 



From these facts, it becomes an interesting question why, during 

 life, the stomach is free from liability to injury from a secretion, which, 

 after death, is capable of such destructive effects. 



It is only necessary to refer to the idea of Bernard, that the living 

 stomach finds protection from its secretion in the presence of epithelium 

 and mucus, which are constantly renewed in the same degree that they 

 are constantly dissolved, in order to remark that although the gastric 

 mucus is probably protective, this theory, so far as the epithelium is 



