382 DISEASES OF CATTLE. 



measures which are necessary to accomplish the object. The United 

 States was the last of the countries, having old infected districts, 

 which undertook to stamp out this contagion, and, excepting Hol- 

 land, it was the first to reach success. 



The cause {etiology) of lyleurofneuifnoma. — This is a contagious 

 disease, and only arises by contagion from a previously affected 

 animal ; consequently it can never be seen here except as the result of 

 importing affected animals from the Old AVorld. ^^'^len thoroughly 

 stamped out it does not reappear, and if imported animals continue 

 to be properly inspected and quarantined we have every reason to 

 believe that pleuropneumonia will never again be seen affecting the 

 cattle of this country. 



The exact nature of the virus or contagion of lung plague has never 

 been determined. Various investigators have from time to time 

 claimed the discovery of the specific organism of the disease, but it 

 was not until 1898 that Nocard and Roux, by an ingenious method 

 of cultivation, succeeded in obtaining a very feeble growth of an ex- 

 ceedingly minute microorganism. With these cultures the disease 

 was produced in cattle. 



Some investigators and writers are of the opinion that the disease 

 can be contracted only by an animal coming near enough to a living 

 diseased animal to receive the contagion directly from it. They hold 

 that the contagion is expired with the air from the affected lungs, 

 and that it must be almost immediately inspired by another animal in 

 order to produce the disease. Some experimental attempts to infect 

 animals by placing them in stables where diseased animals have been, 

 and by placing the diseased lungs of slaughtered animals in their 

 feeding troughs have failed, and, consequently, apparently confirm 

 this view. 



On the other hand, it is known that the serum from affected lungs 

 retains its virulence and may be used successfully for inoculation 

 weeks or months after the death of the animal from which it was 

 taken. This is particularly the case when this liquid is hermetically 

 sealed in glass tubes. Other investigators state that they have suc- 

 cessfully infected cattle by placing in the nostrils sponges or pledgets 

 of cotton saturated with such serum. Cattle have also, according to 

 the best evidence obtainable, been infected from the clothing of 

 attendants, from horns used in drenching, and from smelling about 

 wagons which have been used to transport carcasses of animals 

 affected with this disease. In the work of eradicating pleuropneu- 

 monia from the United States many stables were found in which the 

 disease would appear and reappear after the slaughter of affected 

 herds, and in spite of any precautions which could be adopted. These 

 were always old stables, with Avoodwork in a decaying condition 

 and with floors underlaid with filth which could not be thoroughly 



