ESSAYS ON BACTERIOLOGY. 101 



painstaking and lifetime devotion of Jenner, and to 

 his immortal renown, vaccination was for a long time 

 thiought to occupy a peculiar and isolated place in 

 pathology. The mj'stery about it, and that which 

 strengthened incredulity as to the identity of cow- 

 pox and smallpox, was this: — how can such a virulent 

 disease as smallpox he so modified and mollified by 

 passing through the body of the cow? For such a 

 thing there was no analogy. 



But the investigations of the last ten years have 

 put an entirely new face upon this idol of unbelief. 

 The modification of a disease by passing it through 

 the body of certain animals has become a common- 

 place matter in pathology. We no longer wonder at 

 such a claim nor doubt its possibility. 



It is unnecessary to enter into the details of these 

 new facts, they are so generally known. It is suffi- 

 cient to refer to the modification of the virus of ra- 

 bies, of the pneumococcus and of others, brought 

 about by this means, or by other methods of altering 

 the culture soil or the conditions of growth. 



Acting upon the view that cowpox was modified 

 smallpox, the attempt has been repeatedly made to 

 imitate the whole process artificially; that is, to secure 

 vaccine virus by inoculating the cow with smallpox. 

 The first to do this is supposed to have been Gassner 

 of Gunzburg (1807). It was done on a large scale by 

 Thiele of Kasan and Geely of England (1838). They 

 carried their vaccine virtis, thus obtained, through 



