4 TOXINS AND ANTITOXINS. 



Ptomaines. 



This name is more specially reserved to desig- 

 nate those alkaloidal substances, generally highly 

 hydrogenized, that are formed outside the organism, 

 from the fermentative action of anaerobic microbes 

 on albuminoid substances. 



These bases are generally volatile, with an intense 

 and tenacious purulent odor; often, however, they 

 possess a floral odor (aubepine, syringa), and even 

 like that of musk. They combine readily with 

 acids and with the chlorides of the heavy metals, 

 yielding crystallizable salts. 



The ptomaines afford no specific reaction whereby 

 they may be readily identified ; and their identifica- 

 tion is effected only after a painstaking analysis. 



We must here call attention, however, to several 

 of their more common properties, beginning with 

 their basic character, their oxidizability by the air 

 and consequently their well-defined reducing power 

 a property that led Selmi to propose a mixture 

 of ferric chloride and potassium ferricyanide as a 

 reagent for their detection.* They are precipitated 

 by all the general reagents for the vegetable alka- 

 loids. Selmi has given several reactions, such as 

 those afforded by sulphuric, hydrochloric, and 

 nitric acids, which appear, however, to apply much 



* Sulle ptomaine od alcaloidi cadaverici. Bologne, CLXXXVII, 

 p. II. 



