BACTERIAL PROTEINS 35 



been confirmed by many investigators. There 

 are several ways in which this cleavage can be 

 secured, but the most satisfactory is the one 

 which we first employed. The dried protein, 

 after exhaustive extraction with alcohol and 

 ether, is repeatedly heated at 78 with a two per 

 cent solution of sodium hydroxide in absolute 

 alcohol. When this is done the poisonous frac- 

 tion goes into solution while the nonpoisonous 

 part remains undissolved and is removed by 

 filtration. This is evidently a true cleavage and 

 not a mere disintegration. The nonpoisonous 

 portion contains all the carbohydrate and phos- 

 phorus of the original complex molecule. 



THE PROTEIN POISON. Since this body has 

 been obtained from all true proteins, bacterial, 

 vegetable and animal, so far examined, we have 

 called it "the crude soluble poison;" "crude" 

 because it is undoubtedly a mixture of chemical 

 bodies and "soluble" in contradistinction to the 

 bacterial cellular proteins from which it was 

 first prepared. Aqueous solutions are somewhat 

 opalescent, and may be quite turbid. Filtration 

 through hard paper generally gives a clear fil- 

 trate but with some preparations we have found 

 filtration through porcelain necessary to secure 

 a perfectly clear solution. All the crude soluble 

 poisons that we have obtained give the biuret 



