Abstract

1. In rabbits, the onset of fever produced by cocaine, beta-tetrahydronaphthylamine, and hay infusion is accompanied by corresponding increases in serum osmotic pressure. This tends to retard the loss of surface water.

2. The temperature decreases sometimes seen after giving pyretic agents are associated not with increased, but often with decreased osmotic pressure.

3. Serum specific gravity increase is seen with the onset of marked febrile reactions, but is often missing with the lesser rises. This indicates that the blood volume factor is of less importance than surface evaporation.

4. The osmotic pressure increases are far greater than can be accounted for by the blood sugar increases. In the case of cocaine, they are of the same order as the lactic acid increase. In the case of beta-tetra, perhaps fifty per cent larger.

5. While lactic acid per se seems unable to raise the serum osmotic pressure, the amount of increased muscular activity would seem to be a parallel factor. Thus muscular activity is concerned both with the increased heat production, and the decreased heat elimination, which together account for the onset of fever.