NATURE OF BLOOD-PLATELETS 117 



(fig. 21) has been a matter of great controversy for many 

 years ; some say that they are normal constituents of 

 the blood, but are precipitates of the plasma. Others 

 say that they are extruded nuclei of red cells, and 

 again it has been suggested that they are derived from 

 leucocytes. Lastly, some people say, even to this day, 

 that they arise from all three sources. In view of this 

 controversy, Professor Ross and his collaborators, con- 

 sidering the "red spots" in leucocytes to be centro- 

 somes, suggested that if anybody could find them in the 

 blood-platelets it would, of course, settle once and for 

 all the real cellular nature of these bodies. 



A short time after this, while I was working to 

 determine the laws of diffusion by this method, I 

 appreciated that "red spots" were not centrosomes at 

 all, but were diffusion-vacuoles a fact which I pub- 

 lished in The Journal of Physiology* and a fact which 

 was afterwards confirmed when divisions were induced 

 in leucocytes and the real centrosomes demonstrated. 



This knowledge rendered Professor Ross's sugges- 

 tion of less importance, for since the spots are not 

 centrosomes, the discovery of them in the platelets 

 would not prove that these bodies found in the blood 

 were cells capable of reproduction. But when I was 

 experimenting with morphia on blood-cells I acci- 

 dentally discovered the "red spots" in all the blood- 

 platelets (figs. 22, 23). 



Now, in spite of the fact that these spots are 

 not centrosomes, their appearance in the blood-plate- 

 lets still proves that these minute bodies are living 



1 Journal of Physiology, vol. xxxvii, No. 4. 



