CONTAGIOUS PLEUROPNEUMONIA. 369 



sealed in glass tubes. Other investigators state that they have suc- 

 cessfully infected cattle by placing, in the nostrils, sponges or pledg- 

 ets of cotton saturated with such serum. Cattle have also, accord- 

 ing to the best evidence obtainable, been infected from the clothing 

 of attendants, from horns used in drenching, and from smelling 

 about Avagons which have been used to transport affected carcasses. 

 In the Avork of eradicating pleuropneumonia from 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 Avere adopted. These Avere ahvays old stables, 

 with woodwork in a decaying condition and Avith flooi^s underlaid 

 Avith filth Avhich could not be thoroughly removed or disinfected. 

 In every one of these cases the destruction of the stable, the burning 

 of the lumber of Avhich it Avas constructed, the removal of the ac- 

 cumulations beneath the floors, and thorough disinfection, prevented 

 the recurrence of the plague in neAV stables built upon the same 

 premises. This experience conclusively shoAvs that under certain 

 conditions, at least, stables may retain the infection for a consider- 

 able time, and that when restocked the disease may break out again 

 from such infection. 



As a rule, how^cA^er, the disease is acquired by a healthy animal 

 being near an affected one and receiving the contagion direct. 

 Affected animals may giA'e off the contagion in the early stages of the 

 disease before the symptoms are apparent to the obserA'er ; also, they 

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

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

 ease haA^e disappeared. 



Incuhation. — The time Avhich elapses between exposure to the con- 

 tagion of pleuropnemnonia 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 Avithin three to six weeks after exposure; 

 they may be observed, hoAvever, Avithin tAvo 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 

 ma}^ disseminate the contagion after apparent recoA^ery Avhich give 

 the plague that insidious character so often spoken of, and which 

 greatly increase the difficulties of eradication. 



Syrnqytoms. — The symptoms are such as w^ould be expected Avith 

 inflammation of the lungs and pleurae, but they vary considerably, 

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

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

 appear suddenly; the breathing becomes rapid and difficult, the ani- 

 mal grunts or moans Avith each expiration, the shoulders stand out 

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

 33071°— 16 24 



