254 APPLIED BACTERIOLOGY 



that the disease produced by the bite of the tsetse does 

 not affect wild, but only domesticated animals, especially 

 horses ; also that it is not due to any inherent venom in 

 the fly itself, but to the communication of certain flagel- 

 lated germs from other diseased animals. 



Flagellated monads have also been described by various 

 investigators as occurring in the blood of apparently healthy 

 rats, fish, etc. 



Much work has yet to be done to determine the exact 

 part played by the Protozoa in disease. For detailed in- 

 formation, we would refer the student to the original 

 communications on this subject in the home and foreign 

 medical journals. 



FERMENTATION. 



The term ' fermentation ' is derived from fervere, to boil, 

 and was formerly applied to all those cases where a liquid 

 or semi-liquid mass was seen to become puffed up and to 

 disengage gas without any apparent cause, among the 

 earliest observed forms of this phenomenon being the 

 fermentation of grape- juice and the leavening of bread. 

 Owing to the mystery with which these well-known pro- 

 cesses were surrounded, the term gradually came to be 

 applied to all those chemical processes which were brought 

 about by the presence of a body known as a ferment, the 

 presence of which was indispensable, as the necessity for 

 its presence was unintelligible. The meaning of the term 

 ' fermentation ' has now been much extended, until at the 

 present day we mean those chemical changes which take 

 place in a substance through the agency of a body derived 

 from the animal or vegetable kingdom, termed a ferment. 

 The ferment remains the same, qualitatively, both before 

 and after the reaction. Hence we may class many bodies 



