Prevention, Extermination. 593 



In this connectiou care should be taken that the young offspring 

 from such herds are not fed on infected milk. This is accomplished 

 by heating all skim milk to 85° C, or better, to the boiling point, before 

 feeding to calves or swine. In all cases, however, the milk from evi- 

 dently infected udders should be destroyed. 



In feeding sucking calves it is all important that the milk be free 

 from tubercle bacilli. Infection is most successfully prevented by 

 having young calves suck dams that are known to be free from tuber- 

 culosis as indicated by physical examination and tuberculin tests. If 

 for economic reasons this arrangement is impracticable the calves should 

 be fed with fresh raw milk obtained from healthy cows with every 

 possible aseptic precaution. ]\Iilk sterilized by heat should be used 

 only as a last resort. Milk thus treated has lost the ferments so im- 

 portant for digestion and for the prevention of abnormal gas production 

 in the intestines. For this reason every possible precaution should be 

 observed that the vessels used and the hands of the persons in charg(3 

 of this work are kept scrupulously clean. Heat sterilization is of course 

 always vastly preferable to the use of formalin (see p. 155) or of 

 hydrogen peroxide, because milk thus treated (perhydrase milk, budder- 

 ized milk), aside from the fact that it may contain virulent tubercle 

 bacilli, is unsuitable for sucklings on account of its Ioav fat content (2% ) . 



By careful compliance with these instructions it is possible 

 at least to check the too rapid progress of the disease and to 

 prevent for years the occurrence of very great losses. The 

 measures referred to are however recommended for considera- 

 'tion only in cases where for economic or other insurmountable 

 reasons the complete extermination of the disease is out of the 

 question. 



Extermination of Tuberculosis. Investigations shomng 

 that tuberculosis is an infectious disease, transmissible from 

 animal to animal, and demonstration of the fact that heredity 

 plays only an unimportant role in its transmission has placed 

 the warfare against tuberculosis upon a new and safe basis. 

 The aim and object of this w^arfare now is to protect healthy- 

 born animals from infection during life; if we are successful 

 in this effort the animals will remain free from tuberculosis, 

 irrespective of whether tbey are the offspring of diseased 

 parents or otherw^ise. 



Upon the basis of this principle Bang has worked out a 

 plan for the extermination of tuberculosis from dairy herds 

 which has been put into successful practical operation since 

 1892. The very satisfactory results already obtained have 

 demonstrated not only the correctness of this theory but also 

 its practical worth. 



Bang's Method of Extermination. This consists, in effect, in the 

 destruction of clinically affected animals, the separation and isolation 

 of reactors to the tuberculin test which are otherwise clinically of 

 healthy appearance, and the artificial feeding of calves from the latter 

 with milk free from tubercle bacilli. The details of the method are 

 as follows: 



Vol. 1—38 



