THE PLAGUE BACILLUS 



471 



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, from which flocculent tapering 

 dependent 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-tuberculosis 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, Isevulose, galactose, mal- 

 tose, manntyol, and dextrin, no change in lactose, cane- 

 sugar, and dulcitol. 



Action of antiseptics, etc. The plague bacillus is readily 

 destroyed by antiseptics ; a 1 : 1,000 corrosive sublimate 

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

 acid solution of corrosive sublimate is preferable, and 

 for the practical disinfection of native houses a 1 : 250 

 solution of sulphuric acid may be employed. A tempera - 



FIG. 45. Plague, surface 

 culture on gelatin four 

 days old. 



