32 CHEMICAL PRODUCTS OF BACTERIA. 



them. We may divide the bacterial proteids into two classes : (1) 

 Those which constitute an integral part of the bacterial cells ; and 

 (2) those which have not been assimilated by the cells, but which 

 have been formed by the fermentative or cleavage action of the bac- 

 teria on the proteid bodies in which they are growing. This classi- 

 fication, however, is of questionable value. We allow bacteria to 

 grow for a number of days in a nutrient solution. We then sep- 

 arate the soluble constituents from the formed cells by filtration 

 through porous tiles ; we wash the latter and then study their 

 proteid contents ; but a considerable proportion of the contents of the 

 living cells has already passed into solution, and the bacterial 

 detritus left on the filter gives no exact knowledge of the con- 

 stituents of the living cells. Moreover, the living cells absorb and 

 excrete, and we are not yet able to distinguish with certainty be- 

 tween those substances formed within the cell and those preexisting 

 in the culture medium. The filtrate contains, or may contain, any 

 one or more of the following proteid bodies : (1) Those portions of the 

 proteid substance which were used in the preparation of the nutri- 

 ent solution and which have escaped the action of bacteria; (2) 

 proteids which have at one time been integral parts of the cells, but 

 which have passed into solution on the death and dissolution of the 

 bacteria ; and, (3) proteids which have been formed by the fermentative 

 action of the bacteria, or those which are defined as constituting the 

 second class, as given above. Attempts are now being made (1901), 

 by growing bacteria on solid culture media extensively to distinguish 

 with certainty the proteid constituents of the cell from those of the 

 culture medium ; but at the present writing this work has not pro- 

 gressed sufficiently for us to make any positive statements concern- 

 ing its results. 



It is now quite certain that none of the proteids formed by the 

 cleavage action of bacteria on the normal constituents of culture 

 media, or on those of the animal body, are specific factors in the 

 production of disease. It is true that many bacteria peptonize pro- 

 teids and the specific poisons of certain infectious diseases have been 

 sought for among the peptons ; but there is no evidence that these 

 are more poisonous than those formed by the gastric juice. The 

 specific bacterial poisons are formed by synthetical rather than by 

 analytical processes and they are constituents of the protoplasm en- 

 closed in the cell wall. 



The Bacterial Cellular Proteids — Nencki was the first to at- 

 tempt to study the chemistry of the bacterial cell. His experiments 

 were made with putrefactive bacteria, which were obtained by de- 

 cantation of liquid cultures, freed from fat with ether, dissolved in 

 50 parts of a potash solution of 0.5 per cent., heated for some hours 

 at 100° and filtered. The filtrate was acidified with dilute hydro- 



