GASTRIC DIGESTION. 39 



dry filter. In a number of test-tubes digest equal weights of 

 well-drained fibrin with 10 cc. of each of the above solutions 

 of pepsin hydrochloric acid at 40, and observe the difference 

 in the time of digestion. In order to eliminate errors several 

 tests should be made with each solution of pepsin hydro- 

 chloric acid. We use first 1 g. of fibrin; if no difference is 

 perceptible we make a series of experiments with 0.5 g. and 

 2 g. Instead of the fibrin slices of egg-albumen may be 

 used. The more exact determination can only be accom- 

 plished by means of quantitative analysis. 



VII. PREPARATION OF THE PRODUCTS OF DIGESTION. 



Digest 250 grams of fibrin for forty-eight hours at 40 with one and a 

 half liters of artificial gastric juice and neutralize with sodium carbonate. 



Precipitate: acid albumin. Filtrate: albumoses and peptone. 



Saturate with ammonium sul- 

 phate. 



Precipitate : albumoses, boil with Filtrate : peptone and ammonium 



barium carbonate. sulphate, boil with barium car- 



bonate. 



The best material for digestion is well-drained fresh 

 blood-fibrin. 



If only the coagulated fibrin preserved in chloroform-water is avail- 

 able, it is advisable first to subject it to the following treatment before 

 using : Heat the fibrin in a large dish (enamelled-iron dish) with water 

 containing 2 cc. of hydrochloric acid, specific gravity 1.19, to the liter, 

 until it swells and becomes jelly-like. After cooling the jelly is ready 

 for use. It dissolves almost as readily as the fresh fibrin. The swell- 

 ing, however, sometimes remains incomplete, presumably when the 

 fibrin was boiled too long before being put into the chloroform-water. 



