TUBERCULOSIS 279 



should welcome such a regulation, for the effect of its en- 

 f ore em (Mi.1 is to prevent the spread of disease and to im- 

 prove tlu 1 (jiiality of milk supplied by the farmer to the 

 operator. 



The prevention of the introduction of ineipioutly dis- 

 eased animals into the herd is a far more difficult 'problem. 

 The history of the disease in the individual animal usually 

 shows a slow lint not a continually progressive development. 

 Periods of development are followed by periods of dor- 

 mancy, in which neither the animal nor the parasite is 

 active in its attack on the other. The organisms remain 

 alive in the ti^ucs. and during periods of diminished vital- 

 ity in the animal may find opportunity for renewed action, 

 causing a rapid progress of the disease. In man recovery 

 from infection is the rule rather than the exception, while 

 in cattle recovery is probably so rare that it can not be 

 considered as a factor in the frght against the disease. For- 

 tunatoly, the period of latency may cover several years, and 

 so permit of its detection in the earlier stages of the disease 

 before the infected animal becomes an element of danger. 



Detection of tuberculosis. In the early stages of the dis- 

 ease it is impossible to detect it by a physical examination 

 alone. Not until the disease has made sufficient progress to 

 affect in considerable degree the general health of the ani- 

 mal are the symptoms apparent, even to an experienced 

 person. In the last stages the animal becomes emaciated., 

 the hair rough, the eyes sunken, and the head often ex- 

 tended. The appetite may remain good, but food seems to 

 have no effect. If the lungs are involved, coughing may be 

 noted, especially after the animal has been forced to violent 

 exercise. In the case of glands that can be examined in 

 the livinu animal, such as those of the neck and udder, an 

 enlarged condition should always arouse suspicion. It is 

 impossible for the average farmer or veterinarian to tell 



