The Blood Picture of Normal Laboratory Animals *

I. Method of obtasning blood. The universal method of obtaining blood from the rat is by snipping off the tip of the tail, preferably with a razor blade. This method gives valid results only under certain circumstances, for by repeated bleeding from the tail, there results, from trauma, a high grade inflammatory reaction with hyperleukocytosis (Klieneberger and Carl281). Repeated withdrawals of even the small amount of blood necessarv for counting soon lead to marked anemia (Bunting66).