246 B. C. H. HARVEY AND R. R. BENSLEY. 



neutral red. At the bottom of the foveolae the alkaline reaction 

 gives way to the crimson acid color which is exhibited by the whole 

 foveola and by the surface. The foveolar epithelium also stains 

 the crimson acid tint. Neutral red stains the dead cells deep 

 red, and also the granules of the small cells of Heidenhain referred 

 to above. 



Thus the consistent results of four separate methods show 

 that the hydrochloric acid is not free as such in the gland, and 

 that the contents of the canaliculi of the parietal cell contrary 

 to expectation are alkaline in reaction. The question naturally 

 arises, then, where is the acid of the gastric juice formed and what 

 are the factors concerned in its formation? Without doubt, 

 our reactions with the dyes of the cyanamin series indicate that 

 the hydrochloric acid of the gastric juice is set free in the foveola, 

 possibly also on the free surface of the mucous membrane. As 

 to the source of the chlorine concerned in the formation of hydro- 

 chloric acid of the stomach the experiments of Greenwood ('85), 

 Macallum ('08), and Fitzgerald ('10) seem to be conclusive. 

 Greenwood showed that in preparations of the mucous membrane 

 of the stomach made with silver nitrate, and then reduced in the 

 light, the parietal cells stained much more strongly with the 

 silver deposit than the other epithelial elements. In his studies 

 of the silver reaction for chlorides Macallum showed that only 

 chlorides, phosphates, and carbonates, of silver gave this reduc- 

 tion reaction, and devised a method by means of which the 

 phosphates and carbonates could be excluded and only chlorides 

 exhibited. This method consisted in using for the reaction a 

 solution of silver nitrate containing nitric acid in which the 

 phosphates and carbonate of silver are soluble. By this means 

 he demonstrated that the parietal cells of the stomach were rich 

 in chlorides. This result has recently been confirmed by Miss 

 Fitzgerald, who found that the reaction was obtained not only in 

 the body of the parietal cell but also in the intracellular channels. 



This being the case, in view of the fact that the secretion of 

 the parietal cells is alkaline while in the cells themselves, and 

 that the secretion of the whole gland while contained in the gland 

 lumen is very nearly neutral as shown by the neutral red and 

 cyanamin reactions, it seems probable that the chlorine is 



