THE LUNG PLAGUE. 27 



tlioug'li slow return of the respiratory murmur, with increased mobility 

 of the ribs and easier movement of the flanks. 



TERMINATION. 



Cases of lung diseases in cattle end in partial or complete restoration 

 to health, or death by prostration, suffocation, purulent fever, or hectic. 



As a rule, when a herd of cattle has suifered from the contagious 

 pleuro-pnenmonia, the surviving animals, whenever slaughtered, show 

 old adhesions, partial collapse of the lung tissue, atrophy or wasting of 

 the lung, thickness of the heart's covering or pericardium, and sometimes 

 chronic abscess. Complete recovery without leaving the slightest traces 

 of pre-existing lesion occurs, It has been noticed that cattle that have 

 once had pleuropneumonia fatten more readily than others. 



Death supervenes during the acute attacks of the disease from shock, 

 prostration, or gradual suffocation. When animals linger on for some 

 time in the bloodless state peculiar to this disease, and which is mainly 

 due to the great drain on the system by the immense discharge which 

 occurs in the substance of the lung and cavities of the chest, a perma- 

 nent impairment of the functions of nutrition or assimilation occurs, 

 and although the appetite may be partially restored, emaciation advances, 

 and the animal sinks. A terrible diarrhea or dysentei;y usually accom- 

 l)auies this form of disease. 



In other cases abscesses form in and around the lungs and in other 

 parts of the body, and the animals die of purulent infection. Occasion- 

 ally a cavity formed by tlie breaking up of d4seased lung tissue commu- 

 nicates with the pleural sac or cavity of the chest, and a condition known 

 to pathologists as empyema results, to the certain destruction of the 

 animal. 



DURATION OF THE DISEASE. 



Affected animals usually pass through an incubative stage varying 

 from twenty to eighty days, and usually averaging from twenty-five to 

 forty days. The acute stage of the disorder varies from seven to twenty- 

 one days. Convalescence extends over a period of one, two, and even 

 three months, during the greater part of which the convalescent animal 

 is often capable of infecting healthy cattle. 



The mortality varies from one to ninety per cent, of the affected ani- 

 mals. When a first case is isolated early, all the remaining animals may 

 continue to enjoy health. As a rule, in mild outbreaks, the mortality 

 obtains twenty-five per cent., and in severe cases sixty, seventy, eighty, 

 and even one hundred per cent. 



In England the lung disease has doubled the usual cattle mortality of 

 the country, and during many years fifty per cent, of tlie cattle that 

 have died of disease have died of tlie contagious lung disease. 



