6 TOXINS AND ANTITOXINS. 



difficult operation. The materials must first be 

 exhausted with water slightly acidulated; then, 

 after precipitating the albuminoids by boiling and 

 defecating by adding lead acetate, the liquid is evap- 

 orated to one-half its volume and dialyzed in a 

 vacuum.* 



Phosphomolybdate is then added to the dialyzed 

 liquid, and the precipitate formed, which now con- 

 tains all the bases, decomposed by boiling with 

 lead acetate. After removing the excess of lead, 

 there is thus obtained a limpid solution of all the 

 alkaloidal bases in the form of acetates. These 

 are separated by alcohol and by means of frac- 

 tional precipitations with various metallic salts, 

 depending upon the known properties of the bases. 



In order to facilitate their study, the ptomaines 

 have been grouped under two distinct classes, the 

 one embracing the cadaveric or putrefactive 

 ptomaines, of undetermined microbial origin, the 

 other containing the ptomaines formed by microbes 

 of known character. Each of these two groups is 

 itself divided into subgroups, as shown in the 

 following table: 



* Armand Gautier: C. rend, de I'Acad^mie des Sciences, cxiv, 

 p. 1256. Ibid., xcvii, p. 264, and xciv, p. 1600. 



