868 DISEASES OE CATTLE. 



monia froni 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 woodwork in a decaying condition and 

 with floors underlaid with filth which could not be thoroughly 

 removed or disinfected. In every one of these cases the destruction 

 of the stable, the burning of the lumber of which it was constructed, 

 the removal of the accumulations beneath the floors, and the thorough 

 disinfection prevented the recurrence of the plague in new stables 

 built upon the same premises. This experience conclusively shows 

 that under certain conditions, at least, stables may retain the infec- 

 tion for a considerable time, and that when restocked the disease may 

 break out again from such infection. 



As a rule, however, the disease is acquired by a healthy animal 

 being near to an affected one and receiving the contagion direct. 

 Affected animals may give off the contagion in the early stages of the 

 disease before the symptoms are apparent to the observer, and they 

 may retain this infectious character, if they survive the attack, for 

 six months and probably for a year after all symptoms of the disease 

 have disappeared. 



Incubation. — The time which elapses between exposure to the con- 

 tagion of pleuro- pneumonia and the first appearance of the symptoms 

 of this disease varies greatly with different individuals and with dif- 

 ferent outbreaks of the disease. Ordinarily the symptoms of disease 

 make their appearance within three to six weeks after exposure; 

 but they may be observed within two weeks or they may not become 

 apparent until nearly or quite three months. It is this long period of 

 incubation, and the great length of time that an animal may dissemi- 

 nate the contagion after apparent recovery, which give the plague 

 that insidious character so often spoken of, and which greatly 

 increases the difficulties of eradication. 



Symptoms. — The symptoms are such as would be expected with 

 inflammation of the lungs and pleurse, but they vary considerably 

 according to the type which the disease manifests. If the attack is 

 an acute one, as is frequently seen in hot weather, the symptoms 

 appear suddenly; the breathing becomes rapid and difficult, theanimal 

 grunts or moans with each expiration, the shoulders stand out from 

 the chest, the head is extended on the neck, the back is arched, the 

 temperature is 104° to 107° F. , the milk secretion is suspended, there 

 is no appetite, rumination is stopped, the animal may bloat and later 

 be affected with a severe diarrhea. Such cases are generally fatal in 

 seven to twenty days. 



Very often the attack comes on slowly and the symptoms are much 

 less clear. In the mildest cases there is a cough for a week or two, 

 but no appreciable loss of appetite or elevation of temperature. The 

 lungs are but slightly affected and recovery soon follows. Such 



