The behavior of the rabbit against infection with Salmonella abortivoequina was examined and discussed. The data obtained are summarized as follows : 1. Total 32 rabbits were perorally inoculated with the organisms ranging in number from 50 to 25,000 million. 2. Almost all rabbits revealed the symptoms of the infection. The severity of infection may not coincide with the numder of the organisms inoculated, but depend upon the individual susceptibilities. 3. The main symptoms of the disease in rabbits were rise of temperature (23/32=71.9%) and decrease of body weight (28/32=87.5%). 4. The antibodies generally began to rise after the 4th day following inoculation, and tended to appear in the following delaying order : hemagglutinin, O-and H-agglutinin, precipitin, and CF antibody. 5. After 8 weeks or later the antibodies began to fall. Among them, hemagglutinin and precipitin fell earlier, and CF antibody fell a little later or simultaneously with formers but it persisted in exhibiting a low titer for long period. O-and H-agglutinin fell gradually but in all cases they did not completely disappear during the observation period. 6. It seems to be probable that the rabbits which continued to show high precipitin titers, usually harbored the organisms. 7. The organism was detected most frequently from the mesenteric lymphnode and then in the following descending order : the spleen, submaxillary lymphnode and digestive canal. 8. The increase and decrease of the leucocyte number differ from each other, but it may be said that when febrile attack appears, leucopenia will occur and that when temperature becomes normal, it will turn to leucocytosis. 9. The "shift-to-the-left" of neutrophile leucocytes was evident in almost all cases. 10. Macroscopically, the enlargement of the mesenteric lymphnode and the spleen was observed in parallel with the detection of the organisms. 11. From the above stated results, it may safely be said that the rabbit has a susceptibility considerably similar to that of the horse, especially of foals, to the infection of S. abortivoequina. The author wishes to express his sincere thanks to Prof. HIRATO, the chief of this Department for his kind direction and review of this study, and also to Assist. Prof. SHIMIZU for his helpful criticisms
