310 PATHOGENIC BACTERIA. 



poorly, except with such concentrated penetrating stains 

 as carbol-fuchsin and L,6ffler's alkaline methylene blue, 

 and even with these the bacilli stain more deeply at the 

 ends than in the middle, so that they appear not a little 

 like diplococci. 



For the demonstration of the bacilli in the blood Canon 

 recommends a rather complicated method. The blood is 

 spread upon clean cover-glasses in the usual way, thor- 

 oughly dried, and then fixed by immersion in absolute 

 alcohol for five minutes. The stain which seems best is 

 Czenzynke's : 



Concentrated aqueous solution of methylene 



blue, 40 ; 



0.5 per cent, solution of eosin in 70 per cent. 



alcohol, 20 ; 



Distilled water, 40. 



The cover-glasses are immersed in this solution, and kept 

 in the incubator for three to six hours, after which they 

 are washed in water, dried, and then mounted in Canada 

 balsam. By this method the erythrocytes are stained red, 

 the leucocytes blue, and the bacillus, which is also blue, 

 appears as a short rod or often as a dumb-bell. 



Sometimes large numbers of the bacilli are present ; 

 sometimes very few can be found after prolonged search. 

 They are often enclosed within the leucocytes. It really 

 is not necessary to pursue so tedious a staining method 

 for demonstrating the bacilli, for they stain quite well by 

 ordinary methods. They do not stain by Gram's method. 



The bacillus is non-motile, and, so far as is known, 

 does not form spores. Its resisting powers are very re- 

 stricted, as it speedily succumbs to drying, and is cer- 

 tainly killed by an exposure to a temperature of 60 C. 

 for five minutes. It will not grow at any temperature 

 below 28 C. 



The bacillus does not grow in gelatin or upon ordinary 

 agar-agar. Upon glycerin agar-agar, after twenty-four 

 hours in the incubator, minute colorless, transparent, 



