166 PROTEIN POISONS 



dried and powdered. It is partially soluble in water, and 

 the soluble part constitutes that which we have used in our 

 experiments. 



The Bacterial Filtrate. After the bacilli have been 

 removed, the culture medium is concentrated on a steam- 

 bath to one-sixth its volume. This concentrated fluid is 

 poured into five times its volume of absolute alcohol, which 

 throws down a heavy, sticky precipitate. This precipitate 

 is placed in Soxhlets and extracted, first with alcohol and 

 then with ether. Next, it is powdered and split up with 

 alkaline alcohol after the method used with the cellular 

 substance. This breaks it up into poisonous and non- 

 poisonous groups, which we distinguish from the corre- 

 sponding bodies obtained from the cellular substance by 

 designating them as "the precipitate poison" and "the 

 precipitate residue." 



The Precipitate Poison. This differs in none of its physical 

 or chemical properties, so far as we have investigated, from 

 the cell poison. 



The Precipitate Residue. This is freely and wholly soluble 

 in water. It gives all the protein reactions and is precipitated 

 by uranyl acetate and metaphosphoric acid. 



The Final Filtrate.- In this manner we have designated 

 that portion of the culture-medium that remains after the 

 concentrated medium has been precipitated by five times 

 its volume of absolute alcohol. The alcoholic filtrate gives 

 a voluminous precipitate with an alcoholic solution of 

 mercuric chloride, showing that all the protein material 

 has not been precipitated by the alcohol. This filtrate is 

 freed from alcohol by distillation and has been used in 

 some of the animal experiments described later. 



It will be seen that we have split up the tubercle cell 

 into two portions: the cell poison and the cell residue. 

 The culture-medium has been concentrated and then pre- 

 cipitated with five times its volume of absolute alcohol, 

 and this precipitate has been broken up into two portions: 

 the precipitate poison and the precipitate residue, and the 

 portion of the culture-medium left after the removal of 



