88 THE LUNG PLAGUE OF CATTLE. 



18th. An unbroken chain of cases can be traced from the cow im- 

 ported into Brooklyn in 1848 to the present day. 



19th. Prior to that importation lung plague was unknown on the 

 American continent. 



20th. The most inclement countries have failed to produce lung 

 plague. 



21st. The most torrid regions have failed to produce lung plague, 

 though they aggravate it when once introduced. 



22d. Temperate climates apart from imported infection have failed to 

 produce lung plague. 



23d. Privations of travel have failed to produce lung plague. 



24th. Impure air has failed to produce lung plague. 



25th. Feeding distillery swill has failed to produce lung plague. 



26th. Feeding the refuse of glucose and starch factories has failed to 

 produce lung plague. 



27th. No other conclusion is open to us than that lung plague is 

 caused in Western Europe and America by contagion only, and, if so, we 

 have a perfect guarantee that it can be completely stamped out and 

 permanently excluded. 



28th.. The infection of the herds on our unfenced Western and South- 

 ern pasturages would render it as impossible for us to stamp out the 

 disease as it has been for the people of South Africa and Australia. 



29th. The danger of such an infection is being constantly increased 

 with the increase of the infected area in the East, with the increase of 

 cattle imports, with the increase of thoroughbred herds, with the move- 

 ment of thoroughbreds W T est and South for the improvement of native 

 cattle, with the increased shipment of Eastern calves to be matured in 

 the West, and with the improved railroad facilities. 



30th. The virus of lung plague retains its virulence for over a month 

 in a hermetically sealed glass tube, for months in a close building, and 

 for a variable time, according to exposure to air, in manure, fodder, 

 'clothes, &c. ; so that the way is open for its propagation through differ- 

 ent unsuspected channels. 



30th. Lung plague is peculiar to the bovine genus ; and other genera 

 of animals, man included, can only assist in the dissemination of the 

 disease by carrying the virus on the surface. 



31st. The mortality from lung plague varies much, but may reach 100 

 per cent, in hot climates and seasons. Hence the necessity for exclud- 

 ing it from the warmer portions of the continent. 



32d. The incubation of lung plague, extending from a fortnight to 

 three-and-a-half months, is one of the most dangerous features of this 

 disease, and allows ample time for sending infected but still apparently 

 healthy animals to the utmost confines of our territory. This long period 

 of latency condemns the practice of passing animals as sound on a pro- 

 fessional examination, and also the proposed method of sweeping over 

 the country and killing all infected herds; for by reason of the many 

 cases that must necessarily exist of infected animals not at the time 

 showing symptoms of the disease, the process would have to be begun 

 again as soon as it had been once performed. 



33d. This long incubation demands, as an essential concomitant of 

 slaughter and disinfection, the entire prohibition or the most rigid con- 

 trol of all movements of cattle in an infected district. 



34th. When an animal survives an attack of lung plague there is us- 

 ually left an encysted mass of dead (infecting) lung inclosed within the 

 living. So that convalescent animals may be held as for a time capable 

 of conveying the disease to others. These encysted masses often re- 



