FORMATION OF HYDROCHLORIC ACID IN THE FOVEOL^E. 237 



was more Prussian blue in the cells of the foveolar epithelium 

 then anywhere alse. The amount in the cells of the necks of the 

 gland was less and decreased to\vard the bottom of the gland 

 tubule, although it appeared in nearly all the cells of the gland. 

 It was abundant in the interglandular connective tissue, being 

 in the blood and lymph vessels. 



Skates experimented upon in the same w r ay showed Prussian 

 blue in the blood vessels and lymphatics of the wall of the 

 pharynx and stomach. The glands of the gastric mucous mem- 

 brane showed the reaction in small quantities in the gland lumina 

 and in a few of the cells. The cells showing the reaction were 

 more numerous in the part of the gland near the free surface 

 than in its deeper portions. The surface epithelium of the 

 stomach and of the intestines two inches beyond the pylorus 

 and of the large intestine contained small quantities of Prussian 

 blue. 



Summary of the Results Obtained by the Prussian Blue Reaction 



and their Significance. 



From the facts reported by Miss Fitzgerald and those which 

 our own experiments have added, it seems clear that the occur- 

 rence of the Prussian blue reaction does not necessarily indicate 

 the formation of free mineral acid under normal conditions 

 in the places in which it is found. It appears in many places 

 where it could hardly have been due to the presence of acid 

 in the blood, lymph, liver, spleen, intestine, heart muscle, etc. 

 In these places its presence must be due to something else. 



It may be due to fatty acids, which bring about the precipi- 

 tation of Prussian blue from solutions of the salts used in these 

 experiments in proportion to the amount of the acid present. 

 It may be due to the withdrawal of the ammonium citrate by 

 more rapid diffusion or by the involvement of the ammonium in 

 the metabolic processes of the tissues. Nencki and Pawlow ('96) 

 have shown that the gastric mucous membrane normally con- 

 tains an extraordinarily large amount of ammonia. Ferric citrate 

 and sodium ferrocyanide solutions give when mixed an imme- 

 diate precipitate of Prussian blue even in the absence of any acid. 

 It may be due to the death or reduced vitality of cells, permitting 



