60 The Lung Plague of Cattle. 



in buildings, and we have known parks, with sheds, that 

 proved regularly infecting year after year to all cattle 

 turned into them. In other cases we have known the 

 vii-us carried for miles on the clothes of attendants, and 

 thus introduced into new herds. 



"A far greater danger lies in the lengthened period dur- 

 ing which the poison of lung fever remains dormant in 

 the system. This averages about three weeks or a 

 month, but may extend, in exceptional cases, to not less 

 than two or even three months. An ox or a cow which 

 has been exposed to the contagion may, therefore, be 

 carried from one extremity of the continent to the other, 

 may be exposed in a succession of markets, and may 

 change hands an indefinite number of times, and be all 

 the while in the best apparent health, though infallibly 

 approaching the manifestation of the disease, and for the 

 latter portion of the time spreading the germs of the 

 malady to others. There is here an opportunity for the 

 unscrupulous to sell off exposed and infected animals 

 without the purchaser having the least suspicion of foul 

 play. There is also the strong probability of animals 

 that have contracted the disease by accident, in cars or 

 otherwise, in passing to a new home, mingling with the 

 herd of the new owner and infecting them extensively be- 

 fore there is a suspicion that anything is amiss. This 

 long period of incubation after the animal is infected, and 

 the equally long period of latency of the malady in ani- 

 mals he has infected, one or two of which only will be at- 

 tacked at intervals of a month, lull suspicion as to the 

 presence of contagion, and it is too often only after great 

 damage has been done that the truth dawns on the 

 mind. 



" In aphthous fever and rinderpest, on the other hand, 

 the disease shows itself in from one to four days after in- 

 fection, and the surrounding animals are so rapidly at- 

 tacked after the coming of the infected stranger, that 

 there is no room for hesitancy as to the existence of con- 

 tagion. Nor can the victims of these diseases be carried 

 far from the point where they have been infected and dis- 

 posed of as sound animals, so that in the very vigor and 

 promptitude of their action we have an excellent basis foi 

 their restriction and control. 



