156 PHYSIOLOGICAL CHEMISTRY. 



ach and preserved in dry form. Sometimes the mucous mem- 

 brane is cut into shreds, dried at a low temperature and ground 

 to a powder, in which condition it keeps very well. In pres- 

 ence of weak hydrochloric acid this powder becomes active 

 and is able to digest a large amount of albumin. Usually, 

 however, the mucous membrane is extracted in some manner 

 as illustrated by the first steps described in the Kuehne-Chit- 

 tenden process. In the commercial processes the following 

 steps are much simpler however. As carried out in the United 

 States, they aim to furnish a finished dry product, one part 

 of which will digest 3,000 parts of egg albumin prepared in a 

 certain way. Several different methods are in use by manu- 

 facturers for purifying and concentrating the extract from 

 the stomach glands. 



Some Reactions with Pepsin. The behavior of peptic 

 extracts may be easily shown by experiment. For this pur- 

 pose an extract made by the use of glycerol, as described above, 

 is very convenient. An aqueous extract will answer if freshly 

 prepared. 



Ex. Boil an egg until it is hard, take out the white portion and rub 

 it through a clean wire sieve with fine meshes, by means of a spatula. 

 Add about five gm. of this egg to 100 cc. of 0.2 per cent hydrochloric 

 acid in a flask, and then add 2 cc. of the glycerol extract. Keep the flask 

 at a temperature of 40 C., with frequent shaking. In time the egg albu- 

 min will dissolve, forming an opalescent liquid. Unless the flask is very 

 frequently shaken the solution of the albumin will be slow. Use the solu- 

 tion for experiment to be described. 



Ex. To 2 cc. of the glycerol extract in a test-tube add a little water 

 and boil a few minutes. Now add this boiled liquid to albumin and 0.2 

 per cent hydrochloric acid, as in the last experiment, and note that under 

 the same conditions digestion does not take place, the heating having 

 destroyed the active enzyme. In like manner it may be shown that the 

 enzyme is destroyed by alkalies or stronger acids. 



Ex. TEST FOR ALBUMOSE AND PEPTONE. About an hour after the be- 

 ginning of the digestion explained in the above experiments pour off about 

 half the liquid, neutralize it exactly with sodium hydroxide or ammonia, 

 and then saturate with powdered sodium sulphate or ammonium sulphate. 

 This precipitates albumose, but not peptone. Filter off the precipitate and 

 apply the biuret test to a portion of the filtrate, using only a very small 

 trace of copper sulphate. A pink color should be observed. Concentrate 

 the remainder of the filtrate from the albumose precipitate by evaporation 



