IXOCULATIOX AS A PREVENTION OF PLEURO-PKEU.MOXIA. 15 



pneumonia is not from a pathologist's point of view, what at 

 first sight it would appear to be, and what for a long time it 

 really was considered, viz., " a disease of the lungs simply," 

 analogous for instance to pleuro-pneumonia in the horse, or to 

 the same disease sporadically occurring in cattle, diseases which 

 have their origin in causes which are ordinary and quite remote 

 from the causes of the epizootic malady ; but a contagious 

 eruptive fever, of which the changes that take place in the lungs, 

 are a symptomatic feature. 



The fever is the disease, the luno'-chancjes a result, in the 

 same way that in variola, or smallpox, there is firstly the 

 variolous fever, then the succeeding eruption on the skin. In 

 the former Xature does her best to throw the disease off throuijh 

 the lungs, in the latter through the skin. 



Perhaps the greatest triumph of medicine (vaccination 

 excepted), was the discovery of inoculation, which, prior to its 

 introduction into this country by Lady Montagu, had long been 

 known and successfully practised in the East. Applied to man 

 the operation technically means the imparting of smallpox to a 

 previously healthy person, by introducing the specific virus of 

 the disease into the system tlarough an incision or puncture in 

 the skin, the result being variola or smallpox of a type milder, 

 and the occurrence of which practically gives exemption from an 

 attack of the true disease. Applied to cattle, the operation 

 of inoculation means the introduction into the system through 

 an opening of the skin of the specific virus of contagious pleuro- 

 pneumonia, the result being a mild degree of fever, with certain 

 phenomena of an eruptive character at the seat of the operation, 

 the occurrence of which also gives exemption from the true 

 disease. 



So far the operation in man bears a resemblance to that in 

 cattle, but no further, for between the two there is this great dis- 

 tinguishing difference, the artificially induced disease in man is 

 contagious, whereas it has been clearly and indisputably shown, 

 and placed beyond all doubt, that the conditions, the disease, 

 produced by inoculating healthy cattle with the virus of pleuro- 

 pneumonia are non-contagious. Having in view the fact that 

 the contagium of pleuro-pneumonia is given off, I would say 

 almost solely by the lungs, the reason for such ditterence is not 

 far to seek, and rests in the fact that inoculation never produces 

 lung-disease. As already hinted, and as I shall show further on, 

 the eruptive ])henomena, which next to the fever, are the lead- 

 ing features of inoculation, occur at the seat of operation. 



It is fortunate that this is so, had it been otherwise, had the 

 lungs as a result of the operation become affected in the same 

 way that they do when an animal contracts the disease, the 

 operation would be inexpedient, dangerous, and so valueless, 

 since each animal which clianced to be operated upon would 



