The reactions of neuroglia and of microglia in cerebral trauma have been well studied in the last few years, but the changes produced by the direct introduction of foreign fluid substances have received little attention. Carmichael,1 in 1928, injected rabbit's blood into the brains of rabbits in order to show the development of its phagocytosis. Davidoff, Seegal and Seegal,2 in a study of the Arthus phenomenon, injected foreign proteins into the brains of sensitized rabbits to demonstrate the same cellular reaction in the brain that is found in the skin.
The present work was undertaken in order to study the cerebral reaction in rats and rabbits when rabbit fat, mineral oil or olive oil was introduced directly into the brain substance.
At first an attempt was made to dye olive oil with sudan 4, neutral red and trypan blue so that it could be more easily recognized