Cotton (8) failed to demonstrate the presence of abortion bacilli in the genital organs of the bull used to serve aborting cows, or in the testicles of two bull calves, one of which had been fed and the other injected with the cultures of the abortion bacillus. He concludes that the bull does not harbor the organisms in the testicles. Carpenter (9) injected both _streptococci_ and _Bact. abortum_ into the scrotal sacs of young calves, and intravenously in others. In no case was he able to recover the organisms from any part of the genital canal, except for a _streptococcus_ in one instance. Rettger and White (10) were unable to obtain evidence of the presence of _Bact. abortum_ in three bulls slaughtered after repeated reactions to the complement fixation and agglutination tests. The three bulls had been under observation for three years, with no conclusive evidence to indicate that they were a source of danger to the herds in which they were a part. They believe that the bull transmits the infection as a passive carrier. Attempts at artificial inoculation by natural channels have failed, with the possible exception of McFadyean, Sheather, and Minett (11) who were able to infect the bull by the prepuce in two cases and by the mouth in one case. The results, however, are by no means conclusive. They conclude, nevertheless, that cattle of any age of either sex may be infected by natural channels with the bacillus of epizootic abortion. Schroeder (12) carried out investigations to ascertain the frequency with which bulls react to abortion tests, and the frequency with which lesions chargeable to abortion bacilli occur in the reproductive organs of reacting bulls. Studies were also pursued which he states conclusively prove that bulls with infected reproductive organs may expel abortion bacilli with the seminal fluid. In the first two mentioned investigations 325 bulls from a Washington abattoir were tested, and slaughtered upon reaction. “Approximately ten per cent of the bulls reacted, and approximately ten per cent of the reacting bulls showed lesions of the reproductive organs from which abortion bacilli were isolated.” The value of these studies, he emphasizes, lies not in “that they give us a measure of the proportion of bulls that react positively to abortion tests or the proportion of reacting bulls that are carriers of abortion bacilli,” but in “the fact that they show that abortion bacillus disease of the bull’s reproductive organs is not a wholly unique affection which practically may be ignored, but an important condition that must be taken into account in our efforts to combat infectious abortion, since it has been proved to be associated with contamination of the seminal fluid.” In discussing the method by which infected bulls transmit the organisms to cattle, he believes that leakage of semen from the penis, or vaginas of cattle after service, contaminates the food which subsequently gains entrance to their digestive tracts.