242 DIGESTIVE SYSTEM. 



juice is the result of a special sensibility on the part of the 

 mucous of the stomach, and that this delicate sensibility can- 

 ilot be deceived : an aliment suitable to digestion by means 

 of the gastric juice is needed to produce it. The mucus, on 

 the contrary, is secreted when the stomach craves food, or is 

 occupied by a foreign body, which the mucus surrounds and 

 isolates. 



It has also been ascertained that after section of the 

 pneumogastric nerves, the gastric juice is still formed, 

 though in smaller quantity: the nerves are not, therefore, 

 indispensable to the act of digestion ; the great sympathetic 

 nerve is generally considered as regulating the digestion of 

 the stomach. 



That remarkable peculiarity by which the secretory organs 

 of the stomach yield genuine gastric juice only when in 

 contact with certain alimentary substances, is now fully 

 recognized, but ought not, perhaps, to be attributed to a 

 peculiar sensibility, to a sort of intuition (Blondlot) of the 

 stomach ; but rather, according to Lucien Corvisart and 

 Schiff, to the fact that these substances furnish an indispen- 

 sable element in the secretion of pepsin : this is the theory 

 of the peptogenous substances and peptogeny of Schiff, a 

 theory which has already produced many practical results, 

 and which we will here sketch rapidly. 



Schiff has proved by numerous experiments that pepsin 

 is not formed uninterruptedly in the peptic glands, simply by 

 the nutrition of the coats of the stomach ; but that a stomach 

 fasting and exhausted by copious digestion loses the prop- 

 erty of yielding a gastric juice which is really active, until, 

 having absorbed certain substances, the coats of the stomach 

 become ladened with elements which are capable of being 

 changed into pepsin : these substances are called peptogens. 

 Thus, after the exhaustion produced by copious digestion 

 continuing from twelve to twenty-four hours, the empty 

 stomach nearly loses its power of digesting the albumen ; 

 but this power increases in a remarkable degree, if a moder- 

 ate quantity of other aliments (peptogens) be introduced 

 into it along with the albumen. In this case, the stomach 

 first secretes a purely acid fluid, which serves to dissolve the 

 peptogenous elements ; and as these become absorbed, and, 

 mixing with the blood, enable it to furnish pepsin to the glands 

 of the stomach, we observe that the secretion of a gastric 

 juice becomes constantly more active or, in short, peptic. 

 These pcptogens are essentially represented by the elements 



