114 DIFFUSION- VACUOLES 



leucocytes may fall by as much as one unit if the cells 

 have been shed for more than twenty-four hours and 

 kept in citrate solution at the room-temperature. 

 There are certain substances also which expedite this 

 loss of vitality and its accompanying lowering of the 

 coefficient of diffusion, especially certain alkaloids and 

 extracts of dead tissues; and it was in the course of 

 experimentation with the alkaloid morphine hydro- 

 chloride that diffusion-vacuoles were seen in the 

 blood-platelets for the first time. 



The events which led to the discovery of diffusion- 

 vacuoles in blood-platelets are worthy of mention. 



Soon after this method of in-vitro staining was 

 suggested by Professor Ronald Ross about five years 

 ago, either he or I saw the "red spots" for the first 

 time in leucocytes. The laws of diffusion which I 

 have described were not then known, and only minute 

 vacuoles had been seen in the cells, for alkalies had 

 not been employed. These spots only appeared as 

 minute red points in the cytoplasm, and in appear- 

 ance they certainly resembled the centrosomes of 

 plants and other cells; for it must be remembered 

 that hitherto leucocytes have never been seen to divide, 

 and no one knew what their centrosomes were like. 

 In the preliminary note in The Lancet 1 by Professor 

 Ross and Messrs. Moore and Walker, in which this 

 in-vitro method was first described, these "red spots" 

 were mentioned, and it was suggested that, from their 

 appearance, they might possibly be centrosomes. Now, 

 it is well known that the nature of the blood-platelet 



l The Lancet, July 27, 1907. 



