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



the entrance of salts which would not have entered living or 

 healthy cells. It may be that the cells which show the reaction 

 are just those which are poisoned by the salts used. The iron 

 and ammonium citrate solution injected repeatedly during 

 several days caused the death of one kitten. Therefore this 

 salt has a serious toxic action. It may be that the interaction 

 chemically of these two salts with the contents of certain cells 

 may sometimes permit the liberation of an acid in them, when 

 no acid would have been produced in the absence of the com- 

 plex chemical state which exists when they are present. It may 

 have been absorbed from the surface of the mucous membrane. 

 Its presence between the epithelial cells and in underlying lym- 

 phatic vessels of the stomach and intestine suggest this possi- 

 bility. 



Since the Prussian blue may be precipitated in so many places, 

 the fact that it is sometimes precipitated in the canaliculi of a 

 few parietal cells in a relatively small part of the stomach per- 

 haps in an abnormal condition at the time does not necessarily 

 prove that free hydrochloric acid is formed under normal con- 

 ditions in the parietal cells of the stomach as a whole. The 

 failure to get any reaction in the stomach in some experiments, 

 the small number of parietal cells in which it ever appears, its 

 occurrence in other tissues and in the blood vessels and lymph 

 vessels before it appears in the parietal cells at all, the fact that 

 several factors other than the presence of free mineral acid may 

 cause the precipitate to form, all these things show that it 

 would not be right to conclude from the evidence which the 

 Prussian blue reaction affords that free hydrochloric acid is 

 formed in the paiietal cells. Much less could one reach this 

 conclusion from any other evidence that has been adduced, for 

 all other evidence is much less definite than this. And this 

 failure to show clearly that free hydrochloric acid is formed in 

 the parietal cells becomes quite clear when it appears, as we shall 

 show in the following part of this paper, that the contents of the 

 canaliculi of these cells are alkaline and those of the gland lumina 

 are not acid when free acid is being produced by the mucous 

 membrane. 



