THE PLAGUE BACILLUS 



395 



amount on the bottom and sometimes upon the sides of 

 the tube. After some days the broth may become a little 

 cloudy. A delicate flocculent film develops if the tube 

 be kept absolutely at rest. In broth to which a little 

 butter-fat or ghee has been added little islands of growth 

 appear on the surface, and from 

 these flocculent tapering depen- 

 dent growths form in about a 

 week, provided the tubes or 

 flasks be kept absolutely at rest, 

 the bulk of the broth remaining 

 clear. This is the stalactite 

 growth of Haffkine, and is very 

 characteristic (B. pseudo-tuber- 

 culosis also gives it). Broth 

 cultures reduce a weak solution 

 of methylene blue. 



With sulphuric acid alone a 

 feeble indole reaction can be 

 obtained with week- old broth 

 cultures. With sulphuric acid 

 and a nitrite a well-marked 

 indole reaction can be obtained 

 under the same conditions. 



The fermentation reactions of 

 the B. pestis, which MacConkey 

 has pointed out are practically identical with those by the 

 B. pseudo-tuberculosis, are as follows : Acid production, 

 but no gas, in glucose, laevulose, galactose, maltose, 

 mannitol, and dextrin, no change in lactose, cane-sugar, 

 and dulcitol. 



Action of antiseptics, etc. The plague bacillus is readily 

 destroyed by antiseptics ; a 1 : 1000 corrosive sublimate 

 or 1 : 100 chloride of lime solution being efficient. An 

 acid solution of corrosive sublimate is preferable, and for 



FIG. 44. Plague, surface cul- 

 ture on gelatin four days 

 old. 



