1910. | Hydrochloric Acid in the Gastric Tubules. 7 Oa 
colour. Edinger mentions that his results confirm those of Lieberkiihn,* 
who also observed the yellow colour of the stomach following the use of 
alizarin. 
Tropeolin was another reagent used by Edinger. This yellow dye, known 
as Tropzeolin OO, is unaffected by organic acids, but is exceedingly sensitive to 
mineral acids, the smallest trace of the latter being sufficient to cause the 
colour to change to carmine red. It was brought into medical technique for 
determining the presence of free hydrochloric acid in the gastric juice by 
Von den Velden,t who used it in the form of a crystalline salt of potassium 
and not in the brown commercial state. He pointed out that in the presence 
-of much peptone, or of a small quantity of albumen, the colour change does 
not oceur on the addition of hydrochloric acid. 
Edinger also points out that in the presence of strongly saline fluids the 
reaction does not occur. He applied the reagent by injecting a solution into 
the large artery of the stomach of fasting dogs killed just before injection. 
He found no trace of red colour in the gastric mucosa, and obtained a yellow 
colour everywhere. Previous to this, Edingert had employed tropeolin in 
_an investigation of the stomach of the frog with negative results. 
Trinkler§ also employed tropeolin. After carefully washing the stomach 
of the dog, he placed the teased glands in a solution of the dye and made 
his observations under the microscope. He found both the parietal and the 
chief cells yellow, the tint of ‘a neutral solution of tropeolin, and therefore 
concluded that neither kind of cell held or formed free acid. He was 
further strengthened in his view by the negative results obtained with litmus. 
Stintzing|| endeavoured to determine the acid-forming element by means 
-of Congo red, which changes in colour from deep red to blue in the presence 
-of a trace of hydrochloric acid, and forms a firm compound in either alcoholic 
or aqueous solution. He applied the red solution to the gastric mucosa of the 
following animals :—Frog, mouse, rat, guinea-pig, and rabbit, and in each 
ease within certain cells of the fundus glands he detected blue granules, 
sometimes small, sometimes the size of a cell nucleus. Although not 
venturing to affirm that these results proved the existence of acid within 
these cells, which could be classed as parietal cells, he held the opinion that 
they furnished some supporting evidence of the formation of acid in the 
parietal cells. 
* Lieberkiihn, ‘Sitzungsb. d. Gesell. z. Beférd. d. ges. Naturwiss. zu Marburg,’ 1874. 
Original paper unobtainable for reference.—M. P. F. G. 
+ Von den Velden, ‘Deutsch. Archiv Klin. Med.,’ 1879, vol. 23 ; 1880, vol. 27. 
{ L. Edinger, ‘ Archiv Mikros. Anat.,’ 1879, vol. 17. 
§ N. Trinkler, ‘ Archiv Mikros. Anat.,’ 1885, vol. 24. 
|| Stintzing, ‘Miinchener Med. Wochenschr.,’ 1889, p. 793. 
