1894.] MICROSCOPICAL JOURNAL. 3C7 



blood corpuscles of the blood of oviparous vertebrates, 

 he says ; " the blood of oviparous vertebrates constantly 

 holds colorless cells differing essentially from white 

 blood corpuscles. These elements in progressive de- 

 velopment become perfect red blood corpuscles and for 

 this reason he proposes to call them by the name of 

 Hsematoblasts." 



In the fourth paper upon the development of the red 

 corpuscles in the blood of higher animals, viviparous 

 vertebrates, he states that the hsematoblasts in the blood 

 of men and viviparous vertebrates are very small, deli- 

 cate, slightly refracting elements of a contour almost 

 invisible, with a diameter of 1-5 to 3 micromillimeters. 

 Immediately after the removal of the blood from the 

 vessels the hsematoblasts become thorny and are apt to 

 formgroops or clusters, which latter feature is less pro- 

 nounced in the blood of man than in certain animals. 

 He thinks that they play an important part in the for- 

 mation of fibrin, though this is doubtful. In his conclu- 

 sions, he states that the red blood corpuscles arise from 

 more or less regular small elements which are color- 

 less, delicate and quickly changed or modified as soon 

 as removed from the blood vessels of living creatures. 



From the description of Hayem I think it plainly fol- 

 lows that he designated as hsematoblasts two form ele- 

 ments which I hope to show are entirely distinct from 

 each other. 



II. — BLOOD PLATELETS. 



The first one who saw in the fresh blood granules, 

 granular masses or plaques was Max Schultze. [Archive 

 fur Mikroscopische Anatomie. Vol. 1, p. 38, 1861.] To- 

 day instead of the word plaque we adopt the name 

 platelet, it being the diminutive of plate, identical with 

 the French plaque. 



Blood platelets are colorless lumps of living matter 



