• Histogenesis of the Blood Platelets. 265 



6. The blood 'platelets are cells out of which the red blood cor- 

 puscles develop. 



That they have nothing to do with the development of red 

 blood corpuscles is shown by the absence of transitions between 

 them and young red blood corpuscles in preparations from bone 

 marrow appropriately stained, and also by well established facts 

 in the development of the red blood corpuscles. 



In brief, after much study of the subject and for the reasons 

 given, as well as for many others, I am compelled to believe that 

 all these theories of the origin and nature of the blood platelets 

 are erroneous and untenable. 



As one of the results of an extensive study of the blood and 

 blood forming organs of various animals I have become convinced 

 that the blood platelets are detached portions of the cytoplasm 

 of those giant cells of the blood forming organs which have been 

 named megakaryocytes by W. H. Howell to distinguish them from 

 the multinucleated giant cells of the bone marrow, the so-called 

 osteoclasts or polykaryocytes. 



This view of the origin and nature of the blood platelets is 

 based upon the following : — 



Facts and Observations 



By means of a special staining method, devised by me, which 

 gives the so-called Romanowsky polychrome staining, I have 

 been enabled to stain characteristically the blood platelets in 

 sections of fixed tissues and organs so that they may be positively 

 recognized and may be clearly distinguished from other histolog- 

 ical elements. "* 



The description of this method of staining will be found at the 

 end of this paper. 



I have studied especially sections of the bone marrow and spleen 

 of the cat and young kitten. Similar material from man, mouse, 

 dog, rabbit, guinea pig, white rat, and opossum has also been 

 studied. The appearances observed in the preparations from the 

 blood forming organs of man and of these animals indicate that 

 the blood platelets originate from the megakaryocytes in all of 

 them. 



