68 Miss M. P. FitzGerald. The Origin of the [June 4, 
therefore regarded the reaction as indicating the presence of chlorides in the 
parietal cells, and associated this with their acid-forming function. 
Though giving support to the presence of chlorides within the parietal 
cells, the results cannot be regarded as proving the point, for Macallum* 
has shown that besides the chlorides other silver salts, such as the phosphate, 
carbonate, etc., produce a coloured reduction compound under the action of - 
light, and that it is only in the presence of free nitric acid, which prevents 
the formation of these other coloured reduction compounds, that the reaction of 
silver nitrate can be relied upon for the detection of chlorides in animal and 
vegetable tissues, and in this case also taurine and creatine must be absent, 
since they give a reaction similar to that of the chloride in an acid solution. 
Before accepting the conclusion of Mary Greenwood, or attributing the’ 
reaction to the presence of hydrochloric acid in the cells, it would, therefore, 
be a matter of especial importance to eliminate the possilility of the 
reaction being due either to the presence of phosphate of sodium, the diacid 
form of which is supposed by Malyf to be the effective agent in bringing 
about the production of hydrochloric acid from sodium chloride, or to other 
organic compounds of physiological origin, which will also in the absence of 
free nitric acid produce a dark reduction compound with silver nitrate under 
the influence of light. 
This has been accomplished by Macallum,t who at the same time proved 
by the use of his silver nitrate—nitric acid method that in comparison with 
the chief cells and adjacent tissues chlorides were present in abundance in 
the parietal cells of the gastric glands of the rabbit and guinea-pig, the 
reaction being so pronounced as to readily demonstrate the occurrence of 
these cells along the course of the tubules. 
From this necessarily condensed account of even a portion of the work 
done it will be seen that hitherto certainty has not been attained in 
reference to the structure elaborating the hydrochloric acid of the gastric 
secretion, although the view that its elaboration was in some way connected 
with the parietal cells has been maintained. Neither hasit hitherto been proved 
that the hydrochloric acid exists in a demonstrable form in the secretion of the 
glands before this reaches the free surface of the mucosa. Therefore, in spite 
of all endeavour during the intervening years, the outlook of Bickel in 1908 
(see p. 56) closely resembles that of Prout in 1823. 
Notwithstanding so many failures, the opinion was held by Prof. 
A. B. Macallum that micro-chemistry would still reveal the seat of formation 
* A. B. Macallum, ‘ Roy. Soc. Proc.,’ 1905, B, vol. 76. 
+ R. Maly, ‘Zeitsch. f. Phys. Chem.,’ 1878 vol. 1, p. 174. 
¢ A. B. Macallum, ‘ Ergebn. der Physiol ° 1908, vol. 7, p. 628. 
