VII] CHEMISTRY OF BACTERIA 129 



7. Winogradski and Warrington have shown that by 

 nitrification ammonium salts in the soil are converted 

 ■ into nitrites by one set of short bacilli, and these nitrites 

 into nitrates by another set of bacilli ; the two species differ 

 from one another in their motility and general morphology. 

 The nitrates thus produced are the forms of nitrogen which 

 serve as nitrogenous food for plants. This proposition as 

 to the necessity of intervention of special bacteria to nitrify 

 ammonium salts was first enunciated and experimentally 

 established by Schlosing and Miintz, and they were more 

 accurately investigated by Winogradski, Warrington, and 

 Percy Frankland. 



8. The power of certain bacteria to become phosphorescent 

 and to give the medium in which they grow the character of 

 phosphorescence has been first noticed by Pfliiger (phos- 

 phorescence of putrid fish, menthol wood). Katz, Fischer, 

 and Beyrinck have described various species of phosphor- 

 escent bacteria ; particularly the latter has studied them in 

 pure culture (broth, salt, asparagin) and has described 

 various species. Elwers and Dunbar have described vibrios 

 that have the power of phosphorescence. 



9. The series of changes produced by some species of 

 bacteria, called putrefaction of albuminous substances, con- 

 sist chiefly in the decomposition of albumin into lower 

 nitrogenous principles associated with the evolution of 

 sulphuretted hydrogen and ammonia, and the formation of 

 alkaloidal bodies known as ptomaines of Selmi. Brieger, 

 who has first isolated a number of alkaloids (cholin, neurin, 

 cadaverin), has shown that, while some have poisonous 

 action on the animal system, others have not. The fact 

 that injection — either directly into a vein or indirectly into 

 the subcutaneous tissues of animals — of putrid fluids in 

 sufficient doses causes acute poisoning : rise of temperature 



K 



