PATHOGENIC BACTERIA. 323 



monary form the bacilli occur in the sputum, and may be 

 tested in the same manner. This type of the disease is said to 

 be very fatal. In the septicemic form no primary bubo is 

 found; but a bubonic case may become septicemic, and this 

 form is also very fatal. 



During epidemics of plague it has been noted that rats may 

 die in large numbers, and plague bacilli have often been re- 

 covered from the bodies of such rats. The systematic de- 

 struction by health departments of all the rats possible is im- 

 portant where an epidemic is present or is feared. The same 

 applies to mice. The agency of fleas as carriers of the bacilli 

 has been suggested, and according to Thompson* this has been 

 proven. Flies have also been suggested as carriers. 



No one but the most experienced and strictly careful person 

 should trust himself with experiments with cultures of the 

 plague bacillus. The danger is so great, not only to the worker 

 himself, but to those around him that the cultures should be 

 handled in a room where only the worker himself is engaged in 

 his experiments. It follows', of course, that cultures should 

 under no circumstances be entrusted to classes of students un- 

 der instruction. 



The greatest care must be used in working with the bacillus 

 of plague. A number of fatal results have occurred through 

 it in laboratory investigators. 



Haffkine has devised a method of protective inoculation 

 against plague consisting of the injection of small doses from 

 cultures in which the bacilli have been killed. An accidental 

 infection with tetanus at the time of injection in 19 persons 

 in India rather discredited this method for a while, but sub- 

 sequent results have been very encouraging. An active im- 

 munity which is quite lasting, it is maintained, may be secured 

 by this method in some days. The injection is sometimes 



*J. A. Thompson. Australian Medical Gazette. Sidney, Australia. Nov. 

 20, 1908. 



