Abstract
This study is based on the cerebral arteries of 15 rats, 4 white mice, 2 Syrian hamsters and 3 guinea pigs. Elevated areas of tissue formed by the intima were stained metachromatically by cresyl violet in the rat, mouse and Syrian hamster, however none were found in the guinea pig. All areas of metachromasia were associated with a branching of the artery. These protuberances varied from rudimentary to typical valves. These protuberances in the mouse and hamster in general were more rudimentary than in the rat. In the rat there were from 40 to 79 areas of metachromasia. These arteries had a well developed internal elastic membrane separating the base of the valve from the pars media.