HOG-CHOLERA. 419 blood of infected rabbits exposed to 58° C. This blood was found to be exceedingly toxic. DeSchweinitzl found that the introduction of progress- ingly increased amounts of cultures into cows caused the development in them of an antitoxic substance capable of protecting guinea-pigs from the disease. Working in my laboratory, Pitfield2 has found that after a single injection of a sterilized bouillon culture of the bacillus into the horse, the serum, which has origin- ally slight agglutinative reactive power, is so changed as to show a decided reaction. If the horse be immunized to large doses of such sterile cultures, the serum reaction becomes so marked that with a dilution of I : 10,000 a typical reaction occurs in sixty minutes. According to this experiment, in doubtful cases the use of this reaction should greatly facilitate the differen- tiation of the bacillus of hog-cholera from similar ba- cilli. 1 CenlralbL /. Bakt. u. Parasitenk., xx., p. 573. 2 Microscopical Bulletin, 1897, p. 35.