A COMPARATIVE STUDY OF THE BIOLOGICAL CHARACTERS AND PATHOGENESIS OF BACILLUS X (STERNBERG), BACILLUS ICTEROIDES (SANARELLI), AND THE HOG-CHOLERA BACILLUS (SALMON AND SMITH).

1. Bacillus X (Sternberg) belongs to the colon group. 2. Bacillus icteroides (Sanarelli) is a member of the hog-cholera group. 3. The various channels of infection, the duration of the disease and the gross and microscopical lesions in mice, guinea-pigs and rabbits are the same for Bacillus icteroides and the hog-cholera bacillus. 4. The clinical symptoms and the lesions observed in dogs inoculated intravenously with Bacillus icteroides, are reproduced in these animals by infection with the hog-cholera bacillus. 5. Bacillus icteroides when fed to the domestic pig causes fatal infection, accompanied by diphtheritic, necrotic and ulcerative lesions in the digestive tract, such as are seen in hogs when infected with the hog-cholera bacillus. 6. This disease may be acquired by exposing swine in pens already infected with Bacillus icteroides, or by feeding them with the viscera of infected pigs. 7. Guinea-pigs may be immunized with sterilized cultures ofBacillus icteroides from a fatal dose of the hog-cholera bacillus and vice versa. 8. Rabbits may be rendered immune by gradually increasing doses of a living culture of Bacillus icteroides of weak virulence from a fatal dose of a virulent culture of the hog-cholera bacillus 9. The sera of animals immunized with Bacillus icteroides and with the hog-cholera bacillus, respectively, show a marked reciprocal agglutinative reaction. 10. While the blood of yellow fever practically does not exercise an agglutinative reaction upon Bacillus icteroides, the blood of hog-cholera agglutinates this bacillus in a much more marked degree, thus pointing, we think, to the closer etiological relationship of this bacillus to hog-cholera than to yellow fever.