THE PROTEIN SUBSTANCES. 93 



formed in presence of the ferment pepsin. The name is often 

 applied to all acid albumins, but it is perhaps preferable to 

 restrict its use to describe the product from muscle. 



Ex. Free the muscle part of meat from fat as far as possible and run 

 it through a sausage mill several times to bring it to a fine state of sub- 

 division. Wash this chopped mass with distilled water until the washings 

 remain clear. Now, to about 5 gm. of the moist residue in a small flask, 

 add 50 cc. of dilute hydrochloric acid, containing o.i per cent of the true 

 acid. Warm the mixture slightly (to 35 or 40 C), and keep at this tem- 

 perature about three hours. Then filter and test the filtrate. It contains 

 the soluble syntonin, held by the excess of weak acid used. 



Ex. To a small portion of the filtrate add weak caustic soda, which 

 produces a precipitate soluble in excess of the alkali. This latter solution 

 contains albuminate. 



Boil another portion of the filtrate. It does not coagulate directly, but 

 after the addition of common salt precipitation follows. 



It must be remembered that the action of both acids and 

 alkalies on the native albumins may easily extend beyond the 

 formation of the simple products here mentioned. These are 

 merely limiting cases. It has been already shown that by more 

 prolonged action various products of disintegration are ob- 

 tained and the substances just described represent the first 

 stages. With slightly stronger acids or alkalies or by eleva- 

 tion of temperature the more easily separated of the amino 

 complexes begin to split off. The condition of stability is 

 only relative. With molecules as large as these it may even 

 be possible to separate some of the outlying groups without 

 greatly impairing the integrity of the whole. 



ALBUMOSES AND PEPTONES. 



By the simple treatment with weak acids or alkalies alone 

 the changes in the native protein bodies are of the character 

 described in the last paragraph. But in presence of certain 

 enzymes further modifications are reached and these have 

 received the names of albumoses and peptones when they are 

 produced by the ferments of the digestive tract. It is indeed 

 true that these substances may be produced in fairly large 

 amount by the simple chemical treatment or by heating the 



