164 DIGESTION. 



the mode of its production it does not attack the walls of the stomach 

 itself. As the pepsine alone accumulates in any considerable quantity 

 in the gastric follicles, while the acid ingredient appears abundantly only 

 at the time of digestion, no dissolving action can be manifested while 

 the organ is empty of food. It has already been seen, furthermore, that 

 during the active secretion of the gastric juice, its free acid is formed by 

 some modification in the exuded fluids, so that it is distinctly perceptible 

 only in the fluids on the free surface and in the cavity of the stomach. 

 In the substance of the mucous membrane, the acid fluid, even if ab- 

 sorbed, could not exert its solvent action, since it must be at once neu- 

 tralized by the alkaline plasma of the circulating blood. 



Even after death the gastric mucous membrane usually remains nearly 

 intact, because, as a general rule, digestion has been at least partially 

 suspended during the last hours of life, and the stomach accordingly 

 contains little or no gastric juice. Still it is rare, in the human subject, 

 to make an examination of the body twenty-four or thirty-six hours 

 after death, without finding the mucous membrane in the great pouch 

 of the stomach more or less softened and altered in its appearance from 

 this cause. Sometimes, when death takes place suddenly, by violence 

 or accident, in a healthy person, soon after the ingestion of food, 

 and when the body has been protected against rapid cooling, the accu- 

 mulated gastric juice acts powerfully upon the walls of the stomach as 

 well as upon the food which it contains. Owing to the stoppage of 

 the circulation, the local alkalescence of the fluids is no longer main- 

 tained, and the increasing quantity of free acid at last preponderates 

 over the blood remaining in the capillary vessels. The mucous mem- 

 brane becomes imbibed with an active digestive fluid, and in the course 

 of ten or twelve hours may be thoroughly softened and disintegrated, 

 exposing the submucous layer of connective tissue; and occasionally all 

 the coats of the organ have been found destroyed, with a perforation 

 leading into the peritoneal cavity. These changes show that, after death, 

 the gastric juice, if present in sufficient quantity, may dissolve the coats 

 of the stomach without difficulty ; while during life, the changes of nutri- 

 tion going on in the tissues protect them from its influence, and effectu- 

 ally preserve their integrity. 



Daily Quantity of the Gastric Juice. The quantity of gastric juice, 

 secreted during a given time, like that of the saliva, varies very much 

 according to the condition of the secreting organ. In many instances, 

 as we have already seen, it is entirely absent during the intervals of 

 digestion, and is poured out in abundance under the stimulus of recently 

 introduced food. An exact estimate of the normal daily quantity is 

 difficult for several reasons. First, it is evident that if the secretion be 

 excited by artificial irritation of the gastric mucous membrane with in- 

 soluble glass or metallic substances, its quantity is not so abundant as 

 when produced by the stimulus of natural food. Secondly, if excited 

 by the introduction of food, a part of it is almost necessarily absorbed 

 by the alimentary material, and consequently cannot be collected for 



