PLEURO-PNEUMONIA CONTAGIOSA. 53 



disease of a specific character peculiar to the bovine race, 

 and may occur in an acute, or in a sub-acute form. It is of 

 a very insidious character: whole herds frequently becoming 

 affected before the presence of disease is recognised. 



Some of our best authorities consider it as a fever, which 

 tends to localise itself in the lungs, causing in those organs 

 the well marked changes of eff"usion, inflammation of the lungs 

 and pleura, solidification of the lung tissue, and gangrene. 



Causes. — Contagious pleuro-pneumonia is due to contagion 

 in every case, the contagious principle being supposed to 

 gain access to the system by means of the organs of 

 respiration. As a proof of this, portions of diseased lung, 

 etc., have been administered to healthy animals without 

 producing the disease. It is sometimes a matter of diflB- 

 culty to trace the disease to a contagious origin, and on this 

 account some writers do not believe that it is always due to 

 a contagious principle, but favour the theory of spontaneous 

 oriojin. However, there can be no reasonable doubt of the 

 disease being caused by contagion in all cases. 



Symptoms. — The first stage may continue during a period 

 varying from two to eight weeks, the first symptom being 

 an increase of temperature. This is succeeded by anorexia, 

 and derangement of the circulatory system, the pulsations in- 

 creasing in number. There is a short, weak, and husky 

 cough, which is very characteristic of the disease, and is 

 easily recognised by those of considerable experience. If in 

 a cow, there is observed to be a considerable decrease in the 

 quantity of milk secreted. The animal is hide-bound, the 

 coat being unthrifty in appearance, and a gradual reduction 

 of flesh takes place. Auscultation reveals a grating sound. 

 The animal may now show signs of improvement and ulti- 

 mately recover, or the disease may proceed to the second 

 stage, the pulse becoming quicker and weaker, the muzzle 

 hot and dry. Ko sound is heard on auscultation. The 



