PATHOGENIC BACTERIA. 93 



take the characteristic stain, and look as if the protoplasma had 

 been destroyed that enclosed them. 



FIG. 53. 



Growth on A gar. 



Bovine tubercle-bacilli are about one-third smaller than human 

 tubercle bacilli. 



Staining. The tubercle bacilli require special methods to 

 stain them, and a great number have been introduced. They 

 are stained with great difficulty : but once stained, they are 

 very resistant to decolorizing agents. Upon these facts all the 

 methods are founded. 



It will only be necessary to describe those methods principally 

 in use ; and as the examination of sputum for bacilli is of so 

 frequent an occurrence, and so necessary, it is well to detail in 

 particular the method of staining. 



Starting with the sputum, we search for little clumps or rolled- 

 up masses ; if these are not present, the most solid portions of the 

 mucus are brought with forceps upon a clean cover-glass ; very 

 little suffices. With another cover-glass it is pressed and spread 

 out evenly ; drawing one glass over the other, we obtain two 

 specimens, and these put aside or held high over the flame until 

 dry. 



If we desire to examine the specimen quickly, or make a 

 hurried diagnosis, we use the rapid method, with hot solutions ; 

 otherwise we let it stay, in cold solution until the next morning 

 the advantages of which will be later on described. 



The Rapid Method. (B. Frankel's method modified by Gab- 

 bet.) The principle is to combine with the contrast stain the 



