THE HISTOGENESIS OF THE BLOOD PLATELETS 



JAMES HOMER WRIGHT 



Director of the Pathological Laboratory of the Massachusetts General Hospital 

 Assistant Professor of Pathology, Harvard Medical School 



With Two Colored Double Plates 



The theories that have been proposed regarding the nature 

 and origin of the blood platelets, before the publication of my 

 papers on this subject in 1906, may be grouped and briefly dis- 

 cussed under the following headings. 



1. The blood platelets are fragments of the leukocytes. 



The principal objection to this view is that the blood platelets 

 when observed and stained in various well-known ways present 

 such a characteristic structure and appearances as to make such 

 an origin very improbable if not inconceivable. 



2. The blood platelets are derived from the extruded nuclei of 

 the red blood corpuscles. 



The principal objection to this view is that the extruded and 

 degenerated nuclei of the red blood corpuscles never show any 

 similarity in appearance to, nor any transitions toward, blood 

 platelets in preparations in which both of these elements are pre- 

 sent and characteristically stained. I have been able to follow 

 all stages in the fate of these extruded nuclei up to their final 

 dissolving in the plasma in preparations of embryonic blood and 

 of the blood of animals which had been intravenously injected with 

 the hemolytic toxins, ricin and saponin. In these preparations 

 in which the extruded nuclei of the red blood corpuscles are abun- 

 dant I have in no instance seen a suggestion of the formation of 

 a characteristic blood platelet from the extruded nucleus. 



JOURNAL OF MORPHOLOGY. — VOL. 21, NO. 2 



