Dr. William Osler, in his interesting address before the Society of the Alumni of Bellevue Hospital, April 3, 1889,1 gave an excellent summary of what is at present known concerning the active functions of those normal protoplasmic bodies, termed colorless corpuscles, migrating cells, leucocytes, etc. Since Metschnikoff clearly demonstrated the fact that the colorless corpuscles of the blood were not only capable of amœboid movements, but also of attacking and enveloping foreign bodies in the blood and tissues, a large number of active investigators in Europe and America have studied the subject with more or less success. And all agree in stating that these cells are, throughout the healthy structures of the body, actively engaged in enveloping and removing minute particles whether derived from the disintegration of tissue or introduced from without.
From their exhibition of this capacity to devour and remove obstructions and foreign particles, they have