BY DR. OSCAR KATZ. 431 



symptomatic anthrax we have a well-studied disease, the etiology of 

 which is perfectly known. Not so in bovine pleuro-pneumonia. For 

 this reason we have to be careful not to generalise without further 

 information, and it must rest with future researches to decide 

 ui)on this hitherto dark question in the mode of inoculation against 

 pleuro-pneumonia. 



Even if, for the sake of argument, we admit that inoculation 

 against pleuro-pneumonia in the customary shape does protect, we 

 are not yet thoroughly informed as to how long the protection will 

 last. This is, of course, an important factor, which must necessai'ily 

 influence the discussion of the whole question. Human vaccination 

 is known to bestow a long-continuing immunity, and re-vaccination 

 is held to be a powerful aid in securing the intended effect. The 

 question of the period of immunity after inoculation against 

 animal-plagues, is as far as we know, more uncertain than in the 

 ■case of human vaccination. For instance, the pi'otective power 

 of anthrax-inoculation in sheep extends to about one year, 

 while for cattle the period of protection is as yet uncertain. Such 

 an uncertainty has, among other things, rendered the last-men- 

 tioned kind of inoculation, and others objectionable, and it is, 

 therefore, not to be wondered at, if the present practice of inocu- 

 lation against " pleuro " is for the same reason judged in a similar 

 m annex*. 



In addition to the above statements I must point out in a 

 few words that opinions do not agree as to whether inoculated 

 animals are able to infect uninoculated ones or not. This point, 

 of course, is one of paramount importance, and if it could be 

 unmistakably proved that the inoculation in its present shape can 

 yield the means of infection to unprotected individuals, the whole 

 procedure must appear in a most doubtful light. Now, what 

 might happen if a herd of fresh-inoculated cattle, travelling 

 from one end of the Australian Continent to the other, came on 

 their road in contact with other herds that were not inoculated ? 

 Well, they would no doubt give a fair chance to these to contract 



pleuro-pneumonia, which had not existed there before, and the 



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