28 DEPARTMENT OF AGRICULTURE. 



pleuropneumonia, it can easily be settled. Delafond thought that the deterioration of 

 breeds might favor its development. And why, then, has not the disease appeared in 

 South America, while it has decimated the matchless herds of England and Australia ? 

 It may be accepted as a settled truth that the lung disease, like the rinderpest and foot 

 and mouth disease, spreads without reference to any peculiar breed. Improved and -unim 

 proved breeds are alike susceptible of the affection. 



Calves are at times, however, born of sick cows, and present unmistakable signs of 

 the lung plague. The first observation of this sort was made by Hilfelhelseim, in the 

 Rhine provinces, who dissected the foetuses of cows that aborted under the disease. He 

 found the lesions of pleuropneumonia in these animals. Delafond made similar observa 

 tions, but has created some confusion by including cases of tuberculosis with others of 

 pleuropneumonia. In 1S39, a cow that had gone six months in calf was killed in Frei 

 burg, Switzerland, while suffering from pleuropneumonia. The foetus presented signs of 

 the malady. It is common for calves to take the disease soon after birth, and I have 

 shown in a government report that the contagious cattle diseases of Ireland, including 

 pleuropneumonia, were mainly due to the active trade in sucking calves between the large 

 towns of England and Dublin. 



It has been necessary frequently to refer to animals that are susceptible and insus 

 ceptible to attacks of pleuropneumonia. Tins has been ascribed by some to constitutional 

 or inbred resistance or weakness. It is due to what pathologists term, for want of a bet 

 ter name or explanation, idiosyncrasy. At times it appears that young animals resist the 

 disease better than old ones ; and Mr. Harvey, of Glasgow, found that by communicating 

 the disease to yearlings and two-year olds he had fewer deaths than when he had it among 

 his pregnant and milch cows. But, as Sauberg has observed, outbreaks occur in which 

 the older animals seem to bear up better than the young ones, and it is difficult, on pres 

 ent data, to establish any rule on the point. 



It may be accepted as proved that all cattle, whatever their age, breed, sex, condi 

 tion, &c., are susceptible to pleuropneumonia until they have been once seized, and then 

 it is rare to witness a second attack. An insusceptible animal is, therefore, an animal that 

 has once had the disease, either in a mild or latent, or severe and apparent form. 



It is, however, certain that a degree of insusceptibility may be traced in animals that 

 have never been affected, and we are quite at a loss to account for this. Similar observa 

 tions are made in relation to all fevers affecting men and animals. A person has been 

 known to nurse many during an outbreak of yellow fever, escape and live for a year, when 

 the disease has reappeared, and the individual who has been proof against the malady one 

 year has been among the first to die from it the next. 



Not a few cases have been recorded of rinderpest and I have witnessed a remark 

 able one of a cow standing for weeks by animals that died of the malady, and which 

 never showed signs of it. More strange than this are two observations, one in Lyons in 

 1853, and the other in Vienna in 1865, of dogs which could not be rendered rabid by the 

 bites of, and inoculations from, undoubtedly rabid dogs. For the time, at all events, we 

 must rest satisfied with the pathologist s explanation that these animals had a peculiar con 

 stitutional immunity or idiosyncrasy. 



