20 DEPARTMENT OF AGRICULTURE. 



discharge which occurs in the substance of the Tung and cavities of the chest, a permanent 

 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 diarrhoea 

 or dysentery usually accompanies 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. Occasionally a cavity formed by the 

 breaking up of diseased lung tissue communicates with the pleural sack or cavity of the 

 chest, and a condition known to pathologists as empyema results, to the certain destruc 

 tion 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, or 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 animals. When a 

 first case is isolated early, all the remaining animals may continue to enjoy health. As a 

 rule, in mild outbreaks, the mortality attains twenty-five per cent., and in severe cases 

 sixty, seventy, eighty, or 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 the cattle that have died of disease have died 

 of the contagious lung disease. 



LATENT FORM. 



It is necessary that I should draw special attention to the large number of cases which 

 run an insidious course and pass unobserved. These are the most dangerous, as less care 

 is paid to their isolation. 



APPEARANCES AFTER DEATH. 



Animals that are slaughtered, or are permitted to die in advanced stages of the lung 

 plague, present the following characteristics : 



The internal changes are confined almost entirely to the chest. On opening this, by 

 splitting the brisket, as the animal lies on its back, layers of yellowish, friable, false mem 

 brane, of varying tenacity, stretch across and around the sack (pericardium) containing the 

 heart. These adhesions exist on one or both sides of the chest, but are sometimes alto 

 gether absent. They are found bathed in a yellowish, grumous fluid or serum, highly 

 charged with albumen and shreds of solid deposit. Portions of one or both lungs are found 

 more or less firmly adhering to the membrane (pleura) covering the ribs and diaphragm, 

 and in passing the hands, especially round the large posterior lobes of either lung, it is 

 difficult, in advanced stages of the disorder, to detach the diseased portions of the organ 

 from the ribs. 



The false membranes, disposed in layers which may be stripped off the pulmonary 

 surface, are found adhering more or less closely to it, and the membrane (pleura) covering 



