378 Inoculation for Pleuro-Pneumonia in Cattle. 



the same may be said of farcy, small-pox, cow-pox, rabies, and 

 many others, all of which produce their like, and are figured 

 forth in some especial organ of the body. 



The inoculations of pleuro-pneumonia are made then, as we 

 have seen, in the belief that this disease is highly contagious, and 

 spreads itself from this cause, as well as the special causes of the 

 extension of an epizootic; and that the operation engenders a 

 peculiar state of the system which, without imparting the dis- 

 ease itself to. the animal, gives immunity against all the causes 

 which produce it. With regard to attempts being made to con- 

 trol epizootic diseases of various kinds, I may here remark that 

 Dr. Layard, a celebrated physician, wrote an essay in 1757 

 strongly recommending the inoculation of cattle to prevent their 

 falling a sacrifice to a destructive malady which at that time pre- 

 vailed in this country. It does not, however, appear that beyond 

 a few experiments the practice was carried out, although these 

 inoculated animals were said to have been placed amidst the in- 

 fection without sustaining injury. 



I have before alluded to the interest shown, by the Belgian 

 Government in this matter, and I have now to observe that in the 

 early part of this year two diseased cows were sent by order of the 

 Minister of the Interior to Hasselt, to be placed with six inocu- 

 lated animals, the property of M. Willems, sen. Eight days 

 afterwards these two cows died, but the six inoculated animals 

 had remained well down to the time of my visit. Two other 

 cows were inoculated, and subsequently sent to the farm of M. 

 De Moulin, near Hasselt, and placed with thirteen of his cows then 

 ill. These two animals continued unaffected, while, of the thirteen, 

 nine died, and four were restored by medical treatment. I went 

 over to this farm and saw the cows belonging to the Government, 

 and I ascertained that M. De Moulin had seventeen cows ori- 

 ginally, four of which, although not then inoculated, escaped the 

 malady. It is true, these four animals were subsequently ino- 

 culated, and when I was there no disease had existed for three 

 weeks ; but still their escape, at the time the thirteen cows fell ill, 

 militates against inoculation being the sole protection of the 

 Government cows. On inspecting the cattle of the different dis- 

 tillers I found several who had objected to have the operation 

 performed, and their animals had during the summer been as free 

 from disease as the others. 



All parties agree that they have most disease in the winter, 

 when the town is fullest, and when the secondary causes I have 

 named are in active and vigorous operation. It is also admitted 

 that in some summers since 1836 they have had as little disease 

 as during the past. Similar things have occurred in the experience 

 of most persons, and are not without their value in an investiga- 



