240 



INFECTIVE DISEASES. 



tissue of the lungs, and into the trachea, without any result except 

 a small abscess at the seat of puncture. Administration of the 

 virus by the mouth gave equally negative results. The lungs from 

 a recently killed animal infected with pleuro-pneumonia were placed 

 in a shed occupied by healthy heifers, and left there for several days. 

 Fodder, litter, and manure were taken from places in which there 

 were diseased cattle, and placed in contact with healthy cattle, and sub- 

 sequently all the animals used in these experiments were slaughtered 

 and carefully examined, and the results were absolutely negative. 

 Similarly negative results followed experiments made by Saiider- 



FIG. 119. INFECTIOUS PLEURO-PNEUMONIA OF CATTLE, x 480. 



a,a,a, Exudation in air-vesicles, composed of a network of fibrinous lymph with 

 entangled leucocytes; b,b, the same caseating; c, the air- vesicle filled with 

 leucocytes only. In the centre is a blood-vessel filled with a fibrinous plug. 

 (Hamilton. ) 



son and Duguid, and thus confirmed the conclusion arrived at by 

 Brown, that the disease could only be communicated by actual contact 

 of a living, diseased animal with a healthy one. 



The symptoms of the disease in cattle are a rise of temperature 

 to 105 or 107, and a peculiar dry cough, and later the usual 

 indications of pneumonia, difficulty in breathing, and dulness on 

 percussion. As a rule, death follows from exhaustion ; but the disease 

 may also assume a chronic form, if the animal escapes slaughter, 

 and the lung may become gangrenous or tubercular. The period of 

 incubation is about thirty days, but it is uncertain. The lesions are 



