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



From these results Miss Fitzgerald concludes that the hydro- 

 chloric acid was formed as such in the parietal cells and secreted 

 into the gland lumina. She says (p. 82) : "The occurrence of the 

 Prussian blue reaction in the canaliculi of the parietal cells of an 

 animal injected with a solution of these two salts affords con- 

 clusive evidence of the presence of free acid within these struc- 

 tures." 



The absence of the Prussian blue from most of the parietal cells 

 might be regarded as evidence that only a few of these cells are 

 engaged in the formation of hydrochloric acid, and that the 

 greater part of them do not form it. She explains this absence 

 from most of the parietal cells by saying that it may have been 

 washed out of them, but surely in that case it would have ap- 

 peared in them in some preparations. She explains the appear- 

 ance of the reaction in the blood vessels and in the part of the 

 parietal cell next to the blood vessel (and that part only) by 

 the suggestion that under certain circumstances the acid may be 

 secreted by the parietal cells into the blood stream instead of 

 into the gland lumen. But the facts she reports are open to the 

 other interpretation that the Prussian blue, or the salts forming 

 it, may have been excreted from the blood stream into the 



parietal cell. 



Our Own Experiments. 



These were conducted upon rabbits, cats, dogs, a fowl, a 

 snapping turtle, and several skates. Into these animals we 

 injected solutions of sodium ferrocyanide (which we found less 

 toxic than potassium ferrocyanide) and solutions of iron and 

 ammonium citrate. We did not always use molecularly balanced 

 solutions, because we found that the two salts were excreted 

 with very different degrees of rapidity and by different ways. 

 The injections were made subcutaneously or intravenously. In 

 so far as our experiments repeated those of Miss Fitzgerald, they 

 confirmed the results reported by her entirely, but we obtained 

 also some additional results which have a very important bearing 

 upon the conclusion which she drew. 



By these experiments we sought to get answers to the following 

 questions: First, is the Prussian blue precipitate produced in any 

 place other than the gastric mucous membrane? 



