324 A MANUAL OF BACTERIOLOGY 



these are the various coloured pigments ; but the 

 chemistry of the microbian pigments is a subject 

 which has been very little investigated. They are 

 undoubtedly products formed from the decomposi- 

 tion of albuminoids by the agency of microbes. 1 



In concluding the chapter, it may be stated that 

 the substances which microbes produce put a stop 

 to their activity; thus the alcohol produced by 

 yeast, the phenol, cresol. etc., produced by putre- 

 factive microbes, are themselves germicides, which 

 ultimately kill the organisms that produce them. 



1 Concerning the composition of the red pigment produced by 

 M. prodigiosus, see the author's paper iii Comptes Rendus, vol. 

 cxv. p. 321. The green pigment pyocyanin has already been 

 described (p. 319). The author has described ptomaines in 

 glanders, pneumonia, and puerperal fever ; and also one pro- 

 duced by M. tetragonus (see Comptes Rendus, vols. cxiv. and 

 cxv.). 



