256 APPLIED BACTERIOLOGY 



are the pyogenic organisms and the ordinary skin sapro- 

 phytes. Klein and Copeman have, however, independently 

 discovered an organism which may prove to have a specific 

 relationship to these diseases. 



Two pieces of evidence point strongly to a bacterial 

 agency in vaccine lymph : first, the fact that if vaccine 

 lymph is heated up to 60° C. its efficiency is destroyed ; 

 and second, and more important, is the fact that filtration 

 of the lymph through a Pasteur-Chamberland filter re- 

 moves the active principle to which the lymph owes its 

 efficiency. 



It appears that Dr. Copeman has established the patho- 

 genicity of the minute bacilli described by him. He finds 

 that the bacilli in both small-pox and cow-pox are similar 

 morphologically ; so that we must assume that vaccine 

 owes its action to the presence in it of what was originally 

 the small-pox bacillus, which has become modified or 

 attenuated in such a way as to render it capable of con- 

 ferring an immunity against small-pox almost as complete 

 as is produced by an attack of that disease. An important 

 point proved by Dr. Copeman is that the extraneous 

 organisms that may be accidentally present in vaccine 

 lymph are destroyed by the addition of pure glycerine, 

 which is allowed to act for a certain time before the lymph 

 is used. This addition of glycerine is in no way prejudicial 

 to the activity of the vaccine, which is, if anything, more 

 active than before. The advantages of the addition of 

 glycerine are confirmed by Dr. Klein and by several 

 Continental observers. The minute bacilli which are the 

 active agents in vaccine lymph can be demonstrated in 

 large numbers in the early stages of the vesicles, but they 

 are not found when the vesicles have reached maturity, 

 which may very possibly be due to the fact that they have 

 formed spores. 



