214 APPLIED BACTERIOLOGY 



Certain observers have described monads and psoro- 

 sperms as the active agents in small-pox; but it appears 

 that Dr. Copeman has conclusively 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 

 so far as morphology and cultural characters are con- 

 cerned; 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 conferring an im- 

 munity 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. 



Growth on Media. — It has been found impossible to obtain 

 growths on any of the ordinary media, such as gelatine, 

 agar, potato, blood serum, or any of the modifications of 

 these ; but Dr. Copeman has succeeded in obtaining abun- 

 dant growths without difficulty, when inoculation was made 

 into an egg, from a suspension of variolous crusts in salt- 

 and-water. He found that growth proceeded best when 

 the egg so treated was incubated at blood-heat for one 

 month, and that then a pure culture was obtained of a 



