PLAGUE. 411 



The tubes should then be incubated at 37 C, when the 

 transparent colonies of the influenza bacillus will appear, 

 usually within twenty-four hours. 



PLAGUE. 



The bacillus of oriental plague or bubonic pest was 

 discovered independently by Kitasato and Yersin during 

 the epidemic at Hong Kong in 1894. The results of their 

 investigations, which were published almost at the same 

 time, agree in all the 

 important points. 



They cultivated the 



. .. 

 same organism from a 



large number of cases 

 of plague, and repro- 

 duced the disease in 

 susceptible animals by 

 inoculation of pure 

 cultures. It is to be 

 noted that during an 

 epidemic of plague, 

 sometimes even pre- 

 ceding it, a high mor- 

 tality has been ob- 

 served amongst certain you F n ' g G cu S r - B n aC a ^ f 



animals, especially rats Stained with weak carbol-fuchsin. x 1000. 

 and mice, and that 



from the bodies of these animals found dead in the plague- 

 stricken district, the same bacillus was obtained by Kitasato 

 and also by Yersin. 



Bacillus of Plague Microscopical Characters. As 

 seen in the affected glands or buboes in this disease 

 the bacilli are small oval rods, somewhat shorter than 

 the typhoid bacillus, and about the same thickness 

 (Fig. 99). They have rounded ends, and in stained 

 preparations a portion is sometimes left unstained in the 



