CHAPTER XII. 



METHODS OF EXTRACTING PTOMAINS. 



Feom what has been given in the preceding pages, one may form 

 an idea of the difficulties with which the chemist has to contend in 

 endeavoring to isolate the basic products of bacterial growth. He 

 has to deal with complex substances, the nature and reactions of 

 many of which he does not know. Moreover, the bodies which he 

 seeks to isolate are often prone to undergo decomposition and in this 

 way escape detection. Many ptomains are volatile or decomposable 

 at temperatures near that of boiling water, and in such cases so- 

 lutions cannot be evaporated in the ordinary way and the poison 

 remain in the residue. The investigator has frequently been disap- 

 pointed when on the evaporation of a solution, which he has demon- 

 strated to be poisonous, he finds that the residue is wholly inert. 

 Again, he may destroy the substance which he attempts to isolate 

 with the reagents which he employs. So simple a procedure as the 

 removal of a metallic base from a solution containing a ptomain, by 

 precipitation with hydrogen sulphid, has been known to wholly de- 

 stroy the ptomain. Probably the most perplexing difficulty in the 

 isolation of these putrefactive alkaloids lies in the great number, 

 complexity, and diversity of the other substances present in the decom- 

 posing matters. The same ptomain may be present in equal quan- 

 tities in two samples of milk, and yet it may be easily obtained from 

 the one, while from the other only minute traces can be secured. 

 The difference is due to the fact that the other constituents of the 

 milk in the two samples are at different stages of the putrefactive 

 process, and, consequently, differ in their reactions and in their 

 effects upon the agents employed to isolate the poison. All chem- 

 ists appreciate this difficulty. 



The first thing for the chemist, who undertakes this work, to do is 

 to ascertain whether or not his reagents are pure. We have found 

 samples of German ether, imported on account of its supposed 

 purity, to yield on spontaneous evaporation a residue which gave 

 some of the alkaloidal reactions, and a few drops of which, injected 

 under the skin of a frog, caused paralysis and death within a few 

 minutes. We advise that 500 c.c. of the ether to be used be 

 allowed to evaporate spontaneously, and its residue, if there be 

 one, be examined both chemically and physiologically. The 

 basic substance which exists in some samples of sulphuric ether is 

 pyridin. 



230 



