GASTRIC JUICE 247 



to 0.29-0.60 per cent, the ash to 0.10-0.17 per cent. It contains neither 

 peptone, nor leucin, nor tyrosin, but always contains proteid, and at times 

 traces of fatty acids. At a low temperature it becomes turbid, and sepa- 

 rates into three layers: an upper clear layer, a median turbid layer, and a 

 lower one consisting of a sediment of small, homogeneous, strongly refractive 

 granules. 



The analysis by Schumow-Simanowsky of the pure gastric juice of the 

 dog is as follows : 



Acid 0.46 -0.58 per cent. 



Chlorine 0.49-0.62 



Dry residue 0.43 -0.60 " 



Ash 0.09-0.16 



Coagulation by alcohol 0.14 -0.19 " 



Coagulation by heat 0.13-0.18 " 



Precipitation at C 0.011-0.003 " 



Phosphoric acid 0.004 " 



Gastric juice inverts cane sugar, digests proteid, gelatin and f gelatin- 

 forming substances, coagulates milk and splits emulsified fats into fatty acid 

 and glycerin. 



The inversion of cane sugar is accomplished by the acid, the digestion 

 of proteid, etc., by pepsin, the coagulation of milk by rennin, the cleavage, 

 of emulsified fats probably by a third enzyme, the gastric steapsin. We have 

 now to study more closely the acid and these enzymes of the gastric juice. 



A. THE ACID OF THE GASTRIC JUICE 



Proof was given by Prout as early as 1844 that the acid reaction of 

 the gastric juice is due to free HC1 l ; but it was not incontestably established 

 until C. Schmidt (1852) by his convincing analyses showed that more chlorine 

 is secreted by the mucous membrane of the stomach than can unite with all 

 the inorganic bases, including ammonia, present in the gastric juice. 



The percentage of HC1 in the gastric juice is very different in different 

 animals. In the dog it amounts to 0.46-0.58 per cent; and in the case of 

 a boy with a complete cesophageal stricture and a stomach fistula, it was found 

 to be 0.39-0.57 per cent. In other fistulous patients 0.05-0.3 per cent has 

 been observed. 



When proteids are taken into the stomach, the HC1 unites with them, 

 and later with the products of their digestion (Sjoquist). On this account 

 and because the HC1 reacts with the phosphates of the food with liberation 

 of phosphoric acid, great difficulty is experienced in determining the quantity 

 of HC1 in the stomach contents, and in following its quantitative varia- 

 tions. Nevertheless, the mucous membrane secretes more acid than is neces- 

 sary to combine with the proteid, consequently free acid can always be demon- 

 strated, at least in certain stages of digestion. 



The HC1 combined with proteids seems to insure their digestion; the 

 conception that only free acid could be of importance is therefore not sound. 



1 Lactic acid found in the stomach is probably formed by bacterial decomposition of 

 carbohydrates. 

 17 



