146 



PATHOGENIC BACTERIA. 



In the early days of study efforts were made to facili- 

 tate the observation of bacteria by the use of carmin and 

 hematoxylon. Both of these reagents tinge the proto- 

 plasm of the organisms a little, but so unsatisfactorily 

 that since Weigert introduced the anilin dyes for the 



purpose both of these 

 tissue-stains have been 

 rejected. The affinity 

 between the bacteria 

 and the anilin dyes is 

 peculiar, and many 

 times is so certain a 

 reaction as to become 

 an essential factor in 

 the differentiation of 

 species. 



For the study of bac- 

 teria in the stained con- 

 dition we now employ 

 the anilin dyes only. 



The best anilin dyes 

 made at the present 

 time, and those which 

 have become the stand- 

 ard for all bacteriologi- 

 cal work, are made in 

 Germany by Dr. Griib- 

 ler. In ordering the 

 stain the name of this 



Fig. 7.— Apparatus for keeping objects under manufacturer should 

 microscopic examination at constant tempera- 1 , . ~ , 



tures r always be specified. 



A whole volume could 

 easily be devoted to scientific staining. Indeed, the tech- 

 nical difficulties encountered are so great that no explana- 

 tions can be too thorough to be useful. The special meth- 

 ods essential for such bacteria as have peculiar staining re- 

 actions will be given with the description of the organism. 

 General methods only will be discussed in this chapter. 



