234 Report on the Contagious and 



The period of incubation of lung disease is very valuable, extending from 

 ten days, which may be taken as the minimum, to three months, which may 

 be taken as the maximum. Under ordinary circumstances three weeks may 

 be accepted as the average period of incubation. 



In the majority of cases of direct infection, that is to say, where diseased 

 cattle have been placed in contact with healthy animals, the signs of pleuro- 

 pneumonia have manifested themselves in from sixteen to twenty-one days 

 after exposure. Some animals have resisted the infection up to the fiftieth day ; 

 but it must be remarked, in reference to those long periods of apparent incuba- 

 tion of the disease, that there is no precise evidence as to the moment when 

 the virus introduced into the system meets with the conditions which are 

 necessary for the development of the disease ; for it is the case, in reference to 

 all maladies which are proi^agatcd through the means of contagious virus, that 

 a certain susceptibility must exist in the system of the healthy subject before 

 the disease can undergo development. 



Pleuro-pneumonia is confined to the Ox tribe, and, on this account, the 

 choice of the term is unfortunate, as pleuro-pneumonia of the ordinary 

 kind, namely, inflammation of the lungs and membrane covering them, is 

 common to all domesticated animals. Pleuro-pneumonia of the ox, or con- 

 tagious pleuro-pneumonia, or, as it is commonly termed, " lung disease," is 

 distinguished from the ordinary aflection by the absence of any acute signs of 

 inflammation of the respiratory organs, and the gradual advance of congestion 

 with the exudation of lymph into the connective tissue of the lungs. 



As a consequence of these changes the affected lung acquires a considerable 

 increase in bulk, and is distinguished by a characteristic marbled appearance, 

 which is seen on making a section, and which is due to the presence of the 

 exuded lymph of light colour between the lobules, which are rendered dark in 

 consequence of the retention of the blood in their vessels. It has been observed 

 that in the course of three weeks the lung on one side, which normally woidd 

 weigh about 15 lbs., has been increased by interlobular deposit to a weight of 

 45 lbs. 



Appearances similar to those which are seen in the diseased lung of the ox 

 affected with pleuro-pneumonia have occasionally been seen in the lungs of the 

 horse and sheep. There is no reason, however, to suspect that any form of 

 lung disease in the ox, sheep, or pig is contagious, or in any way resembles the 

 pleuro-pneumonia of the ox, save in the occasional occurrence of interlobular 

 deposit. 



The treatment of pleuro-pneumonia is very rarely effectual. Animals have 

 recovered under all kinds of treatment, and the fact that nearly equal results 

 have been obtained by the depletive and the stimulant systems is tolerably 

 good evidence of the inutility of remedial measures. The most successful 

 remedy which has been recently employed is carbolic acid, which has been, 

 and still is, used extensively by Mr. Priestman. Professor Baldwin also has 

 employed the same agent as a curative and preventive of the disease, and he 

 states that the results in his hands have been satisfactory. Mr. Priestman 

 uses carbolic acid externally and internally, giving doses once or twice a day, 

 combined with spiri't and diluted largely with water ; at the same time that he 

 keeps the floor of the cowshed covered with sawdust, which is saturated with a 

 strong solution of the agent. Whatever kind of medical treatment may be 

 employed it is highly important that the sick animals should be carelully 

 isolated. 



Preventive measures naturally take the precedence of curative means in all 

 cases where pleuro-pneumonia has broken out in a district, but it unfortunately 

 happens that, owing to the uncertainty as to the progress of the disease, it 

 is exceedingly difficult to decide as to the efficacy of the means which are 

 employed. Sometimes pleuro-pneumonia spreads with remarkable rapidity 



