The body temperature of 450 normal rabbits has been measured rectally in the natural posture and it has been found that their body temperature be- came constant two hours after meals averaging 39°.26 C (δ=0°.21 C); a large number of them stand between 38°.9 and 39°.6 C. These results were almost constant in rooms where the temperature ranged from 7° to 28°C. On the other hand, the pyrogenic activity of the infected distilled water injected in the ear-vein of the rabbits was shown to be parallel to its dose amount. With repeated, injections of a certain amount of Escherichia coli filtrate rabbits do not develop tolerance against their pyrogenic reactions.
