DIGESTION. 186 



thrown down by the fatty acids set free, and when these last are 

 placed in water and removed by shaking with ether, the rennet re* 

 mains in the watery solution. 



A fasting animal cannot secrete a strongly-acid gastric juice 

 The acid of the gastric juice then cannot be derived from the foods, 

 but must originate in the mucous coat. As the pyloric glands, 

 which contain no delomorphic cells, secrete an alkaline secretion, 

 while the fundus glands, in which such cells occur, yield an acid 

 secretion, it is generally assumed with HEIDENHAIN that the delo- 

 morphic cells are of special importance in the secretion of free 

 hydrochloric acid a statement which other observations tend to 

 confirm. That the hydrochloric acid must originate from the chlo- 

 rides of the blood is evident; and these latter must therefore un- 

 dergo a decomposition with the setting free of hydrochloric acid. 

 This decomposition has been considered as an electrolysis, but the 

 opinion has also been held that it may be caused by some organic 

 acid formed in the mucous membrane (BRUCKB). 



MALT has called attention to the fact that, on account of the 

 presence of a large quantity of free carbon dioxide in the blood and 

 the avidity of the same, there must be present among the numerous 

 combinations of acids and bases which exist in the serum traces of 

 free hydrochloric acid in addition to acid salts. As these traces of 

 hydrochloric acid are separated from the blood by means of rapid 

 diffusion by the glands, the action of the carbon dioxide must set 

 free new traces of hydrochloric acid in the blood, and in this way 

 may be explained the secretion in the blood of large quantities of 

 hydrochloric acid. But though the occurrence of traces of free hy- 

 drochloric acid in the alkaline blood is not denied, it does not fol. 

 low that the hydrochloric acid passes by diffusion from the blood 

 to the gastric juice. Similar processes in other animal glands 

 render it probable that here, as in other cases of secretion, we have 

 to deal with a yet unexplained specific secretory action of the 

 glandular cells. The process going on in the secretion of hydro- 

 chloric acid is not yet understood. 



After an abundant meal, when the store of pepsin in the stom- 

 ach is completely exhausted, SCHIFF claims that certain bodies, 

 especially dextrin, have the property of causing a supply of pepsin 

 in the mucous membrane. This " charge theory/' though experi- 



