368 THE AMERICAN MONTHLY [Dec, 



varying in size from just visible granules up to the size 

 of about i the diameter of a red blood corpuscle. 



The smallest granules are, as seen under immersion 

 lenses, apparently homogeneous or structureless, the 

 larger the granules are the more we are able to dis- 

 cern in them an extremely delicate faintly pronounced 

 reticular structure. All these formations I have stated 

 are colorless, exhibiting when small a peculiar greenish 

 shining appearance characteristic of all granules of 

 living matter. 



They invariably lack the yellowish color seen in the 

 HsBmatoblasts. Small granules are nearly uniform in 

 their diameter and are often seen slightly angular, i. e., 

 provided with from two to four conical projections. 

 The larger the granules swell owing to their taking in 

 of liquid from the surrounding plasma of the blood, 

 the more they assume a grayish color, a discoid shape, 

 smooth contours and a faint reticular structure. 



The easiest way to bring the platelets to view is to 

 treat the blood corpuscles with glacial acetic acid, diluted 

 with equal parts of water. For this purpose a droplet 

 of the solution of this acid is placed upon the skin, pre- 

 ferably the palmer surface of the thumb of the left hand. 

 The skin is then pricked directly through this droplet. 

 Both the blood secured and acetic acid are directly trans- 

 ferred to the slide and quickly covered with a thin cov- 

 ering, glass always of course oiled on its edges. In my 

 own blood platelets are extremely scanty. As soon, 

 however, as acetic acid is mixed with it hundreds of them 

 appear, of all sizes from the minutest granules, up to 

 half the size of a red blood corpuscle, the smallest being 

 slightly angular, glossy and of a greenish refraction ; the 

 larger ones pale gray, smooth, discoid and faintly retic- 

 ulated. The red blood corpuscles, under the influence of 

 this preparation of acetic acid in a few minutes have be- 

 come enlarged to nearly three times their original size, 



