The Origin of the Hydroch loric Acid in the Gastric Tubules. 347 



and potassium ferrocyanide give, even after standing for 24 hours, no 

 evidence of the formation of Prussian blue, nor is the latter produced in the 

 mixtures when either sodium dihydric phosphate or carbon dioxide dissolved 

 in excess is present. On the other hand, the addition of very dilute acids, 

 organic or inorganic, suffice to develop at once a marked Prussian blue 

 reaction. In the case of hydrochloric acid, a concentration of 3G parts of 

 acid in 100,000 (or 0'036 per cent.) gives, with an equal volume of the mixture, 

 a distinct blue, and as the acid in the gastric juice is much more concentrated 

 than this, a mixture of equimolecular solutions of the double salt and 

 potassium ferrocyanide ought, when injected hypoderniically or intravenously, 

 to indicate minutely the structures in the gastric mucosa which are concerned 

 in the production of hydrochloric acid. Hypodermic injections of the mixture 

 in rabbits and guinea-pigs give results which fully bear out this assumption. 



Within a few hours after the injections, a more or less circumscribed 

 greenish deposit was found adhering to the mucosa of the lesser curvature 

 adjacent to the oesophageal opening. An examination of sections of the under- 

 lying tissue revealed, in some instances, no evidence of any blue compound in 

 the gland tubules or in the crypts into which they opened, but in one rabbit 

 the Prussian blue was found at isolated points in the gland tubules and in 

 the crypts into which they opened. In this case only rarely did the reaction 

 appear throughout the length of the upper two thirds of the lumen of a 

 tubule. Much more often it was confined to the third of the lumen next 

 the crypt, while it never obtained in the lowest third. 



Here and there from these deposits in the lumina there branched out lines 

 in blue, which penetrated the parietal cells. As a rule there was only one 

 branch to each cell, but occasionally as many as three or more were found to 

 penetrate a cell. Each branch, immediately on entering the cell, usually 

 ramified, and the branchlets, penetrating the depths of the cell, in some 

 cases curved around the nucleus to reach the cytoplasm on its far side. The 

 blue twigs did not appear to touch the nucleus. Local aggregations of the 

 blue deposit in these canaHculi gave the latter at times a beaded appearance. 



The cytoplasm itself, apart from the ramifications of the blue canaliculi, 

 was as a rule free from colour. The exceptions implied in this were cells in 

 which, under the most favourable daylight illumination, an exceedingly 

 faint, almost imperceptible, blue appeared throughout the cytoplasm. In 

 some cases it was uncertain whether this was due to a scattering of the light 

 reflected from the blue material in the canaliculi, but in the other cases the 

 faint blue appeared to indicate that there is free hydrochloric acid in the 

 cytoplasm. 



It would seem that however the acid is held in the cytoplasm, whether in 



