The assay of anti-pyretic drugs in mice, using intracerebral injection of pyretogenins.

1. A simple, cheap, and reliable method is described for the screening of new compounds for anti-pyretic activity. It involves the intracerebral injection of a suitable pyretogenin in conscious mice.2. The pyretic response is related to the logarithm of the dose in a substantially linear manner when "E" Pyrogen is used.3. A selection of established anti-pyretic drugs were effective in oral doses approaching those used clinically, which shows that the method is unusually sensitive.4. The response to intracerebral pyretogenin is not unduly influenced by drugs known to cause hypothermia.5. It is suggested that "E" Pyrogen injected intracerebrally has a direct effect on the central nervous system, rather than an indirect action through release of endogenous pyrogen.