130 THE DIGESTIVE FLUIDS. 



fused out into the lumen of the glandular duct before the 

 alkaline elements of the cell could bring about its neutralization. 

 This, however, is improbable. Among the various other views 

 which have been expressed, that of Maly has attracted much atten- 

 tion. According to this, the hydrochloric acid results from a mass- 

 action on the part of the carbonic acid of the blood upon the 

 chlorides in the cells, and is immediately eliminated to the outside, 

 while the resulting bicarbonate is returned to the blood. We know 

 that within the cells carbon dioxide is present under great pressure. 

 Schlierbeck thus found that water which is introduced into the 

 stomach of living dogs after a variable length of time contains a 

 certain amount of carbon dioxide, and that its tension rises from 

 30 to 40 Hgmm. while fasting, to 130 to 140 Hgmm. during the 

 process of active digestion. There are objections to this view also, 

 and, as a matter of fact, we can offer no satisfactory explanation 

 which rests on anything but a hypothetical basis. 



The secretion of hydrochloric acid seems to be inaugurated 

 through the activity of a specific hormone which is furnished by the 

 mucous membrane of the pyloric portion of the stomach. Of its 

 nature nothing is known (see also Secretin). 



Significance of the Hydrochloric Acid. One of the functions of the 

 hydrochloric acid no doubt is the activation of pepsinogen to pepsin, 

 and thus a digestive function. We know, however, that life can go 

 on in the entire absence of the stomach, as has been proved not only 

 by experiments on animals but also by operations performed on the 

 human being. A dog whose stomach was almost entirely removed 

 by Czerny in 1876, lived for more than six years after the opera- 

 tion, when it was killed in Ludwig's laboratory ; and it is reported 

 that the animal was normal in every respect, and had increased in 

 weight from 5850 to 7000 grammes. It is thus manifest that 

 while the hydrochloric acid of the gastric juice no doubt aids 

 in the process of albuminous digestion, its presence to this end is 

 not imperative. A further function may be the prevention of putre- 

 factive changes in the contents of the stomach, and we find, as a 

 matter of fact, that albuminous material that has been removed from 

 the stomach at the height of digestion can be preserved for a long 

 time without undergoing decomposition. It has been noted, more- 

 over, that the gastric juice is also capable of arresting putrefactive 

 processes that have begun before the ingestion of such material. 

 A third function, as will be shown later on, is the activation 

 of the duodenal secretion, which in turn calls forth the secretion 

 of the pancreatic juice. 



Tests for Free Hydrochloric Acid. A large number of tests have 

 been devised for the purpose of demonstrating the presence of free 

 hydrochloric acid in the stomach-contents. The most important of 

 these are the following : 



TOPPER'S TEST. A small amount of the filtered gastric contents 

 is treated with a few drops of an 0.5 per cent, alcoholic solution of 



