236 GENERAL BIOLOGY OF MICRO-ORGANISMS 



variety of phenomena in the interaction of the host cells and their 

 secretions on the one hand with the parasites and their chemical 

 products on the other. The elementary conceptions of immun- 

 ology and the primary language of the science are derived from 

 the old theories, especially from Ehrlich's theory, and these theo- 

 ries are an essential part of the introduction to immunology.^ 



1 For a concise presentation in English of facts^ and practical experiments re- 

 lating to immunity, the student is referred to Citron, Immunity, translated by 

 Garbat, Philadelphia. 



