1910. | Hydrochloric Acid in the Gastric Tubules. 67 
The cylindrical epithelium and the interstitial tissue were, on the other hand, 
uncoloured. 
In repeating the experiment with the rabbit, the results obtained were, in 
the main, the same; but in this animal, owing to the glands not being 
uniformly active, the mucosa was flecked with red instead of being uniformly 
coloured, while the intervening tissue was of the normal hue. The pyloric 
region was also uncoloured, except in one instance, when faintly acid spots 
were observed. In the microscopical examination of teased glands taken 
from uncoloured areas, no red colour whatever was seen, nor was the red 
colour peculiar to one kind of cell in the borderland between a coloured 
and an uncoloured area. 
In testing the reagent used, Friinkel found that all acids would produce the 
red colour, also acid phosphates, and acid ammonium tartrate, but that neutral 
salts would not. He regarded the results obtained as proving the acid reaction 
of the gastric mucosa and the formation of the acid in the gland cells, but 
did not feel justified in saying that this formation could be ascribed to one 
or other kind of cell exclusively. He considered the view held by others 
that only one kind of cell produced the free acid, was by no means 
established. 
Oppel* and Gmelint also hold the opinion that an inter-relation between 
the parietal cells and hydrochloric acid is not yet proven. (Gmelin, in the 
course of the experiments upon which he based this opinion, stained the 
parietal cells of the puppy with Congo red and obtained a brown colour. 
During the course of the years in which the experiments previously 
mentioned were performed, indirect evidence in support of Heidenhain’s theory 
of the acid-forming function of the parietal cells was supplied from time to 
time by experimental work of another kind, a complete account of which is 
outside the scope of the present paper. 
Of special interest in reference to the hydrochloric acid originating from 
the chlorides of the organism are the observations of Mary Greenwood made 
in 1884-5. She found, when treating the gastric glands of the pig with 
silver nitrate, that the parietal cells stained readily and deeply with the 
reagent on exposure to light, the reducing portion of the cell apparently 
being the interstitial substance and not the network of the cytoplasm. 
She further found that the cells of the gastric glands of the frog, which 
secrete an acid fluid, gave a colour reaction with the silver compound, while 
those of the csophagus, which secrete an alkaline fluid, did not. She 
* Oppel, ‘Lehrbuch der vergleich. Mikrosk. Anat. I. Theil,’ “ Der Magen,” 1896, p. 253. 
+ Gmelin, ‘ Archiv fiir d. ges. Physiol.,’ 1902, vol. 90, p. 103. 
i M. Greenwood, ‘Journ. Physiol.,’ 1884-1885, vol. 5, p. 195. 
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