46 OMENTAL PLAGUE chap. 



material with other microbes, the only way, in my 

 experience, to identify it by culture is by plate cultures. 

 And if it cannot be identified in this way, it is hardly to 

 be expected that it will be identified by tube culture. Of 

 course it is supposed that the observer is familiar with the 

 appearances and nature of the colonies of B. pestis in 

 their early stages. This conceded, I am confident, from 

 a large experience, that there need be no difficulty in 

 identifying B. pestis in a mixture, such, for instance, as 

 would occur in the sputum of some pneumonic cases, or 

 in the purulent discharge of a suppurating bubo. The 

 plates should be, of course, sufficiently large (three inches 

 diameter), and several plates should be inoculated with 

 the material. As regards the sputum, it should be re- 

 membered that the Diplococcus pneumonia is a frequent 

 microbe in expectorations, and except in acute cases of 

 croupous pneumonia, in which this microbe occurs very 

 numerously, it is present generally only in moderate 

 numbers. But however scarce or however frequent, there 

 ought to be no difficulty in identifying the B. pestis by 

 plates, if this latter should be present in such sputum. 

 Drs. Pakes and Joseph of Johannesburg have recommended 

 to make the cultures of sputum of suspected lung cases in 

 slightly acid broth, for in this medium the B. pestis grows 

 well, whereas the Diplococcus pneumoniae does not, and 

 consequently the former is secured from being crowded 

 out by the latter, which, according to Pakes and Joseph, 

 does happen if the culture medium is ordinary broth. 

 Without for a moment doubting that this modification, 

 viz. using slightly acid broth as culture medium, may be 

 very useful, I have likewise no doubt that plate cultiva- 

 tion with proper nutrient beef-broth agar, such as I have 



