Abstract
1. Experiments have been carried out to analyse the way in which a bacterial pyrogen causes a biphasic pattern of fever in rabbits.
2. It was just during the interpolated period between the first and the second peak of fever, that vasoconstriction was observed in the denervated ear with a larger dose of pyrogen. After adreno-demedullation this vasoconstriction developed more slowly and to a less degree.
3. Moreover, it was principally during the period of the first declining phase of fever that hyperglycaemia was seen.
4. A marked fever developed in a rabbit in which the participation of skin vessels was largely or completely prevented.
5. There was a tendency in intact animals that skeletal muscular activity, as indicated by E. M. G. from the back of the body, was low throughout the period between the two peaks compared with the other periods of the induced fever.
6. A biphasic fever was more likely to occur for the low level of temperature in a thyroidectomised rabbit.
7. It may be concluded that the biphasic pattern of fever is caused by a temporal suppression of a fever which would otherwise be monophasic. The adrenal medullary secretion may be suggested to play an important part in such an effect.
