GRANULAR VENEREAL DISEASE AND ABORTION IN CATTLE. 19 



cattle, so far as we can find, has ever been verified by post-mortem 

 examination. 



Generally it may be said that the evidence in relation to the im- 

 portance of the nodular venereal disease is purely clinical and cir- 

 cumstantial, while that of the abortion bacillus is chiefly from the 

 laboratory. If the Bacillus abortus is inoculated into a pregnant 

 heifer in order to test its virulence, it is injected into one affected 

 with the granular venereal disease. If the granular venereal disease 

 is capable of inducing abortion, and abortion follows the inocula- 

 tion with the abortion bacillus, there is no conclusive proof which of 

 the two infections, if they be distinct, caused the disaster. It has 

 not been shown that the Bacillus abortus of Bang is or is not related 

 to the granular venereal disease. 



There are many defects in the evidence submitted in favor of each 

 hypothesis. If we examine first the Bang theory, we note among 

 other defective points in the evidence: 



1. Experimental inoculations have been without adequate con- 

 trol. No adequate evidence has been submitted to show that, 

 taken an equal number of pregnant cows or heifers of like age and 

 other conditions, and, instead of inoculating them with the Bacillus 

 abortus, they are given in the same manner (intravenously, hypo- 

 dermically, etc.) an equal amount of an innocuous substance, such 

 as salt solution, a similar precentage of the animals would not abort. 



2. The alleged period of incubation required to induce abortion 

 varies inconsistently, according to species. By referring to Table 3, 

 it will be observed that in cows the average time required to induce 

 experimental abortion in the 26 cases recorded was 131 days; in ewes 

 it required 6 to 83 days to induce abortion or infection ; in the guinea 

 pig abortion followed inoculation after an average of 10 days. In 

 other words, the evidence submitted suggests that no matter how brief 

 the normal duration of pregnancy, an infection which usually requires 

 an average of 131 days, or a trifle less than one-half the span of 

 pregnancy in the cow, its natural host, so hastens its energies as to 

 induce abortion in less than half the span of pregnancy in other 

 species, no matter how brief that span may be. Indeed, the records 

 of experimental infectious abortion in the guinea pig indicate that 

 abortion follows in one-sixth the span of pregnancy after inoculation. 

 We are accordingly offered the phenomenon of an infectious disease, 

 the duration of the incubation of which varies widely according to 

 animal species, though each species may be equally susceptible. 



