INFECTIOUS DISEASES OP CATTLE. 



367 



had rapidly diminished, but it was not until 1898 that the infection 

 was finally eradicated. 



The other infected European countries, though they maintain a 

 veterinary sanitary service, are not making satisfactory progress in 

 eradicating the disease. This is due partly to delays in carrying out 

 the provisions of the laws and partly to mistaken ideas as to the 

 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) ofpleuro-pneumonia. — This is a contagious dis- 

 ease, and only arises by contagion from a previously affected animal ; 

 consequently it can never be seen here except as the result of import- 

 ing affected animals from the Old World. When 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 pleuro-pneumonia 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 germs of the disease, but it was 

 not until 1898 that Nocard and Roux, by an ingenious method of culti- 

 vation, succeeded in obtaining a very feeble growth of an exceedingly 

 minute microorganism. With these cultures the disease was pro- 

 duced in cattle. 



Some investigators and writers are of the opinion that the disease 

 can only be contracted 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 pleuro-pneu- 



