544 Veterinary Medicine. 



intravenous injections of a " bovovaccin " , he can render the 

 system of the calf refractory to virulent bacilli, even when inocu- 

 lated. Thousands of his protected calves have been exposed to 

 casual infection with comparative impunity, but a certain number 

 have apparently resisted virulent inoculation as well. This is 

 supported by experiments of Vallee and others in Europe, and of 

 Buckley in America. Its advocates concede that the method 

 fails with mature animals, and various experimenters have found 

 the results inconstant. Pearson, using the avian bacillus and 

 later a nonvirulent bacillus from man, intravenously, has also 

 had a large measure of success. In all alike a number of check 

 calves, under virulent inoculation, but without previous protec- 

 tive treatment, developed tuberculosis, mostly generalized. A 

 measure of protection is undeniable, but cannot be safely made 

 use of when radical, systematic work is carried on for the extinc- 

 tion of the germ. Von Behrings' " bovovaccin " fails with ma- 

 ture animals, its advocates themselves being judges : there is 

 evidence from other sources that it fails at times in the young ; 

 for the cases in which it appears to succeed we have as yet no 

 sufficient evidence that the protection is permanent. 



In estimating its value the unequal virulence of tuberculosis 

 at different times and places must also be considered. Sometimes 

 whole families or herds are decimated or killed out in a few 

 months, and at others we see tuberculous men and families live 

 to old age, and herds, generally affected for years, with no 

 particular indication of general ill health. In my hands a large 

 herd has just shown 50 per cent, reactions to tuberculin, yet the 

 general health seems good and the yield of milk generous. In 

 these cases there is an acquired tolerance (partial immunization), 

 yet the presence of every infected man or beast is a continual 

 source of danger to the sound and unsound alike. The indi- 

 vidual, partial immunity thus becomes a factor in the preserva- 

 tion and extension of the infection. Some day, under encreased 

 virulence, or greater susceptibility, the disease will assume a 

 more fatal type, and the losses will encrease in ratio with the 

 numbers affected. Such deadly outbreaks have been noted 

 among Indians, Esquimaux, Oregon herders, Transvaalers, 

 Negroes, and Philippinoes, and in Jersey, Guernsey and other 

 thoroughbred cattle, and in all cases the preservation of the 



