INTRODUCTION. 



/, 



J t-j> 



different, may look very much alike. The differences usually 

 become apparent when the bacteria are grown artificially. 

 The cultivation is done for the most part in test-tubes contain- 

 ing some material which furnishes suitable food. The nutri- 

 ent materials most used are meat-extract and peptone, which, 

 dissolved with salt in water, constitute nutrient bouillon. Or- 

 dinary gelatin, or a vegetable gelatin called agar-agar, may be 

 added to the bouillon when a solid culture-me- 

 dium is desired. Before these substances can 

 be used for the cultivation of bacteria all 

 other bacteria which they may contain must be 

 destroyed by heat. 



Finally, the effects of bacteria in bringing 

 about disease may be tested on the lower 

 animals. The proof that a particular species 

 of bacteria causes a particular disease cannot 

 be considered complete unless the disease can 

 be reproduced by introducing these bacteria 

 into some animal. 



Bacteriological Literature. — The student who 

 wishes to pursue bacteriological study in any 

 direction farther than it is possible for the limits 

 of a short manual to go, may, besides consult- 

 ing the large text-books, and weekly medical 

 journals, obtain much assistance from technical 

 ' periodicals. The Journal oj Experimental Med- 

 icine, Journal of Medical Research, and the 

 Journal of Infectious Diseases, pubhshed in 

 this coimtry, and the Enghsh Journal of Pathology and Bacte- 

 riology and Journal of Hygiene will give a great deal that is 

 valuable. 



A reading knowledge of German and French is very desirable. 

 The CentralUatt fiir Bakteriologie, etc., a German periodical, 

 and the Bulletin de VInstitut Pasteur, published semimonthly 



Fig. 



■Test- 



TtlBE CONTAIN- 

 ING Culture- 

 medium. 



