120 APPLIED BACTERIOLOGY 



Separation of the Ptomaines. — The chemical methods 

 employed by many of the workers upon these bodies in the 

 past are open to severe criticism. The processes used were 

 very complicated, involving treatment of the raw material 

 with acids under heat, boilings at the ordinary tempera- 

 ture, etc., this alone being sufficient to cause alteration in 

 albuminous bodies present. Owing to the unstable nature 

 of the ptomaines, and their susceptibility to oxidation, all 

 evaporation of solutions containing them should be carried 

 on under reduced pressure, and at a temperature not 

 exceeding 45° C. 



Several of the ptomaines, like the vegetable alkaloids, can 

 be obtained from solutions containing them by extraction 

 with ether, after setting them free with alkali. The solu- 

 tion should, of course, be previously freed from other bodies 

 soluble in ether by extraction with this solvent in acid 

 solution. 



Brieger's Method. — The liquid culture of the organism, 

 or the filtered decoction of the ptomaine-containing body, 

 is rendered faintly acid with hydrochloric acid, and gently 

 warmed. The filtrate is then treated with basic acetate of 

 lead until no further precipitate falls on further addition of 

 the lead salt. The liquid is then filtered, and the excess of 

 lead removed from the filtrate by passing sulphuretted 

 hydrogen, and the precipitated lead sulphide removed by 

 filtration. The filtrate is evaporated to one-third of its 

 bulk under reduced pressure. A solution of mercuric 

 bichloride is then added, when a somewhat heavy and 

 dense precipitate is formed. This precipitate is carefully 

 washed, and then suspended in water, and sulphuretted 

 hydrogen passed ; the white precipitate is decomposed, with 

 production of black sulphide of mercury ; this is then 

 filtered off. The filtrate is then carefully concentrated by 

 very careful evaporation, under reduced pressure, until 



