420 Veterinary Medicine. 



greatest stimulus is given to the enhancement of such qualities, 

 and with this there is the correspondingly ready receptiveness to 

 the tubercle bacillus. To this is added a degree of constitutional 

 delicacy which comes from too close breeding, and which other- 

 wise shows itself in an encreasing infertility, when bred with an 

 animal that is nearly related. In addition, the high bred animal 

 is kept much indoors, where the bacillus, once introduced, is 

 easily preserved and propagated, and is denied the free outdoor 

 life and exercise which might develop muscle and vigor. This 

 is no valid argument for introducing inferior blood to the deteri- 

 oration of the economic value of a race, but rather for the com- 

 plete exclusion of the bacillus which may find in our treasured 

 herd an especially inviting field for its ravages. 



AGE. 



In both man and beast, age appears to have a predisposing 

 effect, but apart from debility or trauma, this may be fully ex- 

 plained on the ground of often repeated infection, an indoor life, 

 and, in dairy cows, the excessive drain upon the system. In 

 thoroughbred herds of cattle, in which the cows are preserved as 

 long as they will breed, and in dairies where they are kept as 

 long as the milk yield is satisfactory, the oldest show by far the 

 largest percentage tuberculous. In secluded individual dairies 

 we have found ioo per cent, affected, Ostertag gives the average 

 for Berlin at 75 per cent., and Bang for Denmark at 69 per cent. 



PREDISPONENT DISEASES. 



As already noted all diseases which undermine the health tend 

 to diminish the powers of resistance to the tubercle bacillus. To 

 be especially dreaded, are long standing diseases which produce 

 emaciation and debility, fevers that for a length of time impair 

 sanguification, metabolism and nutrition, diseases of the digestive 

 organs which cut off the requisite supply of nutritive material, 

 and, above all, diseases of the lungs and air passages that impair 

 the tone of the tissues and invite the attack of the invading mi- 

 crobe. Bronchitis, laryngitis, pharyngitis and tonsilitis in all 

 their varied forms are to be particularly noted. Even in man it 

 is believed that one of the most common channels of infection 

 entrance is through the open tonsillar crypts, and the same doubt- 



