The degree of elevation of the serum lipides was apparently related to the amount of endotoxin injected up to a certain point, beyond which there was no further increase.

There were two types of response to endotoxin by the serum lipides, a moderate increase and an uncontrolled increase. Higher dosages of endotoxin and fasting apparently increased the incidence of the latter response.

No direct correlation could be made between serum lipide responses and histologic evidence typical of the generalized Shwartzman reaction following this regimen of endotoxin injection. The Shwartzman reaction did occur with greater frequency and with lower dosages of endotoxin in fasted animals.

Animals given repeated injections of endotoxin showed an initial increase in serum lipides followed by a progressive decrease to normal levels as tolerance to the febrile action of endotoxin appeared. The febrile tolerance as well as the unresponsiveness of the serum lipides to endotoxin was abolished by thorium dioxide (thorotrast) in these animals. In similar experiments a "breakthrough" of lipide unresponsiveness to endotoxin was obtained by increasing the amount of endotoxin injected.

Some of the implications of these results for the metabolic alterations produced by bacterial endotoxins are discussed.