From the data presented it seems permissible to draw the following conclusions.

1. Guinea pigs cannot be rendered immune to the Bacillus abortus inoculation disease by treatment with heat-killed cultures of this organism. This agrees with the work of Ascoli, and with the general conclusions of many that dead cultures confer very little or no immunity to infectious abortion in cattle.

2. The progress of the disease can be delayed appreciably by such treatment. This is supported by the following observations: (a) the loss in body weight due to the disease is delayed; (b) the development of splenic enlargement is partially inhibited or delayed; (c) the development of renal lesions is delayed or prevented; and (d) the rapidity of multiplication of Bacillus abortus in the splenic pulp is reduced.

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