History of Animal Plagues. 319 



' The total insufficiency of inoculation to answer, in the case of the 

 murrain, the end proposed, on the score of both the preceding circum- 

 stances, would be a sufficient ground for exploding the practice of it. 

 But there is a yet stronger reason against its use, w'hich arises from this 

 principle: — The mtirrain is, at least with respect to the European coun-.. 

 tries, an epidemical disease, though contagious. That is, it does not, asl 

 we have observed before, ever reign but when certain unfavourable cir- 

 cumstances of season have created a predisposition in the cattle to re- 

 ceive the infection, and thence rendered them temporarily susceptible 

 of it. When the etfects of these unfavourable circitmstances of seasoni 

 cease the etfects of the contagion cease likewise, as far as regards accidental! 

 infection 5 so that when the consequences are left to the natural course 

 of things, this disease is only a temporary mischief, to which there is 

 some certain period, though that period may be different, as we have 

 seen above, from the various condition of different places. Now, if the 

 inoculation for the murrain were practised in so general and continued 

 a manner as to render it of any public consequence, supposing the 

 inoculated beasts incurred less danger from the disease by that mode of 

 receiving the infection, and were more secure from future attacks of it, 

 the contagion must be spread in proportion to the extent of the country 

 where the operation is practised, and must also be constantly kept up 

 in sood as well as bad seasons. Hence all the natural means of the 

 contagion being exterminated in the favourable times would be wholly 

 taken away, and in the bad times there would be necessarily a great 



these instances taken together, we find a far greater proportion of the cattle destroyed 

 by the murrain given by the inocufation than would have been by the infection 

 taken' in the natural way. Professor Camper says, nevertheless, 'That such ill 

 success should not discourage the future pursuit of inoculation for this disease, be- 

 cause the same miscarriages happened on the first introduction of this operation for 

 the small-pox into our parts of the world.' But I must beg his pardon for saying 

 that this is an inadvertent assertion, and that he is entirely mistaken in the matter 

 of fact. For the inoculation for the small-pox was equally successful at first as 

 now ; and though extraordinary stress has been lately laid on some particular 

 methods of treatment supposed to be new, yet, where they have not been followed, 

 we have two instances of a greater list of recovered patients in proportion to those 

 which have been lost under the same conduct, than can be produced on equal 

 authority by any of the pretended improvers of this practice. Some few out of 

 great numbers have at all times died of inoculation for the small-pox, but never in 

 any proportion to the beasts, which appear in the relations here cited, to have died 

 from inoculation for the murrain. It was the striking examples of success which 

 could alone have introduced and established the use of inoculation for the small-pox 

 here, and it would have been rejected with horror, and prohibited by authority, had 

 a similar failure to that which has been experienced in the murrain been found m 

 the result of the first trials. 



