16 



to infect a numerous herd; contaminat- 

 ing the one artificial watering place, as 

 also the ground, and the posts of the 

 enclosure, spreading and transmitting 

 the virus, by expectoration, by licking- 

 one another, or by dams licking their 

 calves. 



In such parts, selection of the best 

 milk-producers is always made, and they 

 are preserved only in view of their 

 abundant yield of milk. 



This gives rise to another factor of 

 contamination; as subjects attacked by 

 chronic and slow tuberculosis, give forth 

 virulent matters; of pulmonary, intesti- 

 nal, uterine, or mammary origin. 



For similar reasons to those which 

 favour the diffusion of tuberculosis in 

 the dairies situate in cur rural districts, 

 the animals employed in agricultural 

 labo^r-the oxen — are frequently exposed 

 to contamination. Respecting these, two 

 further circumstances concur, i.e. age, 

 generally advanced-and the weakening 



