THE LUNG PLAGUE. 41 



One of tliese cows was left eighteen days in the stable, and then killed 

 to serve for the pnrpose of inoculation experiments. On the 27th of 

 June another sick cow was placed in the same stable. 



The result was that the five animals from Pomerage resisted the dis- 

 ease as well as one of the healthy ones. The second healthy cow was 

 seized with the malady thirty-five days after cohabitation. 



In order to confirm the above results, the commissioners caused to be 

 placed in stable A all that remained of the first herd. On the 6th of 

 July, 1852, five cows were sent from Paris to Pomerage. Not one of the 

 animals that had served in previous experiments contracted the disease. 



The history of pleuropneumonia, coupled with the observations made 

 on the sui^posed casual agencies cai)able of inducing the disease, are 

 almost sufficient to establish the purely contagious nature of the disease, 

 but there are several important proofs that deserve mention. 



It is seen in all countries where the lung plague aj)pears, that it 

 spreads in x^roportion to the opportunities of contagion. It is worst in 

 large cities, where cow feeders have to make frequent purchases. It is 

 apt to diminish in severity, as per example, in the city of Washington? 

 in Dublin, Ireland, and elsewhere, so long as the cows are confined to 

 stables in the winter and different herds have no chance of approach. 

 When spring and fine weather arrive, and the cows are turned out during 

 part of the day, or altogether, on commons, parks, or pastures, the pres- 

 ence of any infection results in the rapid dissemination of the disease. 

 I had special occasion to study this among the cows turned out into the 

 Phoenix Park, Dublin, and on the commons near !N"ewcastle, in England. 



In 1802 I chose a large estate in Perthsliire, presenting the feature of 

 being cut up in farms, on some of which cattle were wholly bred ; 

 whereas, on others, purchases had occasionally been made. The result 

 was the demonstration of the fact that the disease appeared only Avhere 

 it was carried by diseased cattle. The estate was that of Lord Wii- 

 loughby d'Eresby, comprising twenty-six farms, on eleven of which the 

 disease was at different times imported ; whereas on the fifteen other 

 farms, interspersed between eleven, the only report to be obtained was, 

 "Xever had the disease. Breeds his own stock." 



A similar inquiry relating to the parish of St. Martin, in Perthshire, 

 showed that pleuropneumonia had appeared there in 1815. Since then 

 ten farms have been visited by the disease, and in every case the attack 

 has been distinctly traced to contact with diseased cattle, i^ineteen 

 farms, on which cattle are bred and purchases rarely made, have enjoyed 

 a perfect immunity 



The higli-prized herds of England, which have been carefully isolated 

 by their proi)rietors, have always remained free from the disease, and 

 short-horn breeders have, in many instances, exercised the greatest care 

 not to have any admixturi; with strange animals, which would certainly 

 have destroyed their stock. 



It is needless entering at length into the subject of authorities on this 



