PLAGUE. 437 



be allowed to remain till they have a moderately light 

 colour, the time varying according to their appearance. 

 They are then placed in xylol and afterwards mounted in 

 balsam. 



(/;) Cultures. A suitable portion of the greenish-yellow 

 material having been selected from the sputum, it should 

 be washed well in several changes of sterilised water. A 

 portion should then be taken on a platinum needle, and 

 successive strokes made on the surface of blood-agar tubes. 

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

 transparent colonies of the influenza bacillus will appear, 

 usually within twenty-four hours. These should give a 

 negative result on inoculation on ordinary agar media. 



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 investi- 

 gations, which were Jf 

 published almost at 

 the same time, agree 

 in most of the im- 

 portant points. They 

 cultivated the same 

 organism from a large 

 number of cases of 

 plague, and reproduced 

 the disease in suscept- 

 ible animals by inocula- 

 tion of pure cultures. 



It IS tO be noted that FlG - "3- Bacillus of plague from a 

 , . , young culture on agar. 



during an epidemic Ot Stained with weak carbol-fuchsin. xiooo. 

 plague, sometimes 



even preceding it, a high mortality has been observed 

 amongst certain animals, especially rats and mice, and that 



