116 Agricultural Bacteriology. 



the skim milk and whey to 160 F. before using. In 

 Denmark and Germany such a treatment of skim milk 

 and whey by the creameries and cheese factories is made 

 compulsory. Some of the States have similar laws. It 

 is a process to which no one should object. The butter 

 and cheese maker will find himself repaid in the im- 

 proved quality of the milk furnished him, since the 

 milk cans are not polluted with injurious bacteria from 

 dirty whey tanks. The farmer will find that the heated 

 whey and milk will keep longer, hence will be sweet 

 when fed. 



Spread of the disease in the herd. Any animal with 

 open tuberculosis is giving off the tubercle bacilli, thus 

 exposing the remainder of the herd to infection. The 

 disease may spread slowly at first, but as> one animal 

 after another becomes a new center from which the or- 

 ganisms are furnished, the rate of spread increases. 

 The rate of distribution is well shown in the following 

 case: Twelve healthy animals were placed in a stable 

 occupied by a diseased herd. In six months nine had 

 become infected and the disease had made such headway 

 that four did not pass inspection when slaughtered and 

 examined by the Federal meat inspectors. 



The conditions obtaining in the barn with reference 

 to light and ventilation will exert a great influence on 

 the rate of dissemination in the herd. If the air is poor 

 and the animals are forced to breathe it more* or less 

 continuously during the winter, their ability to ward off 

 the disease is reduced. Plenty of pure air is necessary 

 for cattle as for man. 



The most important phase of the modern methods of 

 curing tuberculosis in human beings is to live out of 

 doors, to sleep out of doors, summer and winter. Light 



