[X.] GASTRIC DIGESTION. 77 



due to the HC1 unaffected. The sulphuric ether does not affect the mineral 

 acid stain. 



(f. ) Mohr's Test. Mix together 2 cc. of a 10 per cent, solution of sulpho- 

 cyanide of potassium, 0.5 cc. of a neutral solution of ferric acetate, and 8.5 cc. 

 water. Place a few drops of this ruby-red fluid on a porcelain capsule, and 

 allow a few drops of the gastric juice to mix with it = a light violet colour at 

 the point of contact, and a mahogany brown when the fluids mix. It is less 

 sensitive than the aniline tests. 



(</.) Shake up a mixture of dilute HC1 and an organic acid, e.g., lactic, with 

 ether. Remove the ether, and on evaporating it, it will be found to have 

 dissolved the organic acid, but not the mineral one. On this fact is based 

 Richet's method of determining the amount of an organic acid in presence of 

 a mineral acid. 



These reactions for a mineral acid are specially to be noted, as 

 they are used clinically for ascertaining the presence or absence of 

 hydrochloric acid, e.g., in a vomit. This acid is frequently absent 

 from the gastric juice in cancer of the stomach. In gastric catarrh 

 the HC1 may be greatly diminished and lactic acid abundant. The 

 presence of peptones interferes with the delicacy of some of these re- 

 actions. The reactions (c.), (d.), (e.), are the most to be depended on. 



10. Carbolo-Chloride of Iron Test for Lactic Acid (U/elmann). Prepare 

 a fresh solution by mixing 10 cc. of a 4 per cent, solution of carbolic acid with 

 20 cc. of distilled water, and I drop of liquor ferri perchloridi. The 

 amethyst-blue solution thus obtained is changed to yllow by lactic acid, while 

 it is not ail'ected by 0.2 per cent. HC1 ; but alcohol, sugar, arid phosphate, 

 yield a similar reaction. 



A faintly yellow-coloured solution of ferric chloride (2-5 drops to 5000. water) 

 is not affected by the addition of HC1, acetic, or butyric acid, but it is inten- 

 sified in the presence of dilute lactic acid. 



ADDITIONAL EXERCISES. 



[Proteids, e.g., albumin, are split up by certain acids and ferments, as 

 shown by Kiihne, into an anti -group and a hemi-group. In the case of 

 ferments, the following scheme represents the results : 



Action of Enzymes (Ferments). 



ALBUMIN. 

 a 



Anti-albumose. Hemi albumose. 



/ / 



Anti-peptone. Anti-peptone. Hemi-peptone. Hemi-peptone. 



Ampho-peptone. 



Leucin, Ty rosin, Leucin, Ty rosin, 

 &c. &c. 





