CONTAGIOUS DISEASES OF CATTLE. 453 



COW is, or how little vitality she may have, she can never develop 

 tuberculosis unless the germ is introduced into the system. 

 When the germ is taken in, if the animal be strong and have no 

 inherited weaknesses, the bacillus is expectorated, or is destroyed 

 by the cells where it lodges, or may be thrown off through the 

 alimentary or urino-genital tract. Every influence which weakens 

 the constitution or resisting power of the animal is a predisposing 

 cause, and favors the development of the disease when the germs 

 are present. The disease is unquestionably contagious, and nu- 

 merous instances have been published in which it has extended 

 along a row of cattle in both directions from a subject of tubercu- 

 losis. Thousands of experiments prove conclusively that animals 

 have tuberculosis, and that it is transmitted from one to another, 

 and from infected cows to human beings. I have dealt at length 

 on this subject because it is one that should interest the people 

 greatly. The spread of this disease over the whole world, with 

 the exception of the Polar regions, the steppes of Russia, and 

 portions of Africa, and the percentage of cattle affected in herds 

 should receive the careful consideration of the public generally. 



Symptoms. — Unthriftiness, decrease in milk, abortion if in 

 calf; the appetite capricious, mucous membrane pale; a dry, dull 

 cough, skin and hair dry and dusty; skin yellow, and the animal 

 ceases to lick itself. As emaciation proceeds more rapidly, the 

 digestive organs are weakened, and diarrhoea reduces the animal 

 to a skeleton. Auscultation and percussion may reveal the lungs 

 diseased. In many cases the thoracic cavity becomes partially 

 filled with blood, as does also the abdominal cavity. The aninuil 

 on getting up in the morning may cough several times. This 

 may be noticed to increase for months before there is much loss 

 of flesh. Such a cow should be looked ujDon with suspicion. A 

 reliable means of diagnosis has been given us by Robert Koch, 

 of Berlin, in what is known as " Koch's lymph of tubercuHne." 

 Where properly used it is an infallible diagnostic agent. Since 

 it was firsit tried on cattle by Prof. Gutmar, of the Veterinary 



