We have learned, chiefly from the work of Metschnikoff, that those white corpuscles or leucocytes which migrate from the vessels in the greatest numbers have marked phagocytic properties, that is, they can devour other living things and thus destroy them just as do the amoebae. In inflammations produced by bacteria there is a very active migration of these cells from the vessels; they accumulate in the tissue and devour the bacteria. They may be present in such masses as to form a dense wall around the bacteria, thus acting as a physical bar to their further extension. The other form of amoeboid cell, which Metschnikoff calls the macrophage, has more feeble phagocytic action towards bacteria, and these are rarely found enclosed within them. It is chiefly by means of their activity that other sorts of substances are removed. They often contain dead cells or cell fragments, and when haemorrhage takes place in a tissue they enclose and remove the granules of blood pigment which result. They often join together, forming connected masses, and surround such a foreign body as a hair, or a thread which the surgeon places in a wound to close it. They may destroy living cells, and do this seemingly when certain cells are in too great numbers and superfluous in a part, their action tending to restore the cell equilibrium. The foreign cells do even more than this: they themselves may be devoured by the growing cells of the tissue, seemingly being actuated by the same supreme idea of sacrifice which led Buddha to give himself to the tigress.