ee. | Hydrochloric Acid in the Gastric Tubules. 87 
presence of chlorides in the cytoplasm of the parietal cells, and, if possible, 
thereby to increase collateral eviderice of the elaboration of the hydrochloric 
acid of the gastric juice within these cellular elements of the gastric mucosa. 
As before stated (p. 68), owing to the fact that, on exposure to 
sunlight, the phosphate and the carbonate of silver form coloured reduction 
compounds similar in colour to that of the chloride, the results obtained by 
Mary Greenwood by the use of silver nitrate furnished only a partial proof 
of the presence of an excess of chlorides in the parietal cells as compared 
with the chief cells, but definite proof of this was afforded by Macallum, 
who eliminated the error which could arise in the interpretation of the 
results obtained by the silver nitrate method as used by the earlier investi- 
gator, by the addition of free nitric acid to the silver nitrate solution, which 
permits the formation of the coloured reduction compound from chlorides, but 
prohibits a similar formation from phosphates and carbonates. 
Macallum* also pointed out that, in the presence of free nitric acid, 
organic substances, with the exception of taurine and creatine, will not give 
the colour reaction similar to that of the sub-chloride of silver, and that 
proteids and albuminoids, when freed from all traces of haloids, do not give 
any compound of silver that will reduce under the action of light. | 
In the present series of experiments, the methods used were similar to 
those employed for the determination of the distribution of the chlorides in 
nerve-cells and fibres by Macallum and Menten,t and of the phosphates 
in muscle by Maud Menten.{ For the detection of salts, such as chlorides, 
phosphates, and carbonates, giving a coloured reduction compound of silver 
on exposure to sunlight, a deci-normal solution of silver nitrate was used ; 
and, for demonstrating the chlorides alone, a deci-normal solution of silver 
nitrate containing 1°5 per cent. free nitric acid. The silver solution was in 
each case made with pure water. 
Investigations were carried out on the fresh gastric mucosa of the rabbit 
and of the guinea-pig. the animals having been killed beforehand by the 
methods described previously (p. 74) for the two species named. In each 
case portions of the fresh stomach, washed quickly in distilled water, were 
rapidly cut into sections, and the mucosa detached from the outer layers of 
the stomach wall placed in vessels containing the respective solutions. 
The tissues were then carefully teased with goose quills, to permit the 
reagent to penetrate. Penetration does not take place readily, and, although 
the presence of the free nitric acid aids the diffusion of the nitrate in the 
* A.B. Macallum, ‘ Roy. Soc. Proc.,’ 1905, B, vol. 76, p. 217. 
+ A. B. Macallum and Maud L. Menten, ‘ Roy. Soc. Proc.,’ 1906, B, vol. 77, p. 165. 
+ Maud L. Menten, ‘Canadian Inst, Trans.,’ 1908-1909, vol. 8, p. 414, 
