352 



Mr. H. C. Boss. 



[May 12, 



15 minutes' time it will be seen that probably all the blood- platelets will 

 show one or more bright red spots in them, and these spots are identical in 

 appearance (except that they are usually smaller) with those seen in the 

 cytoplasm of leucocytes when blood is examined by this in vitro method 

 by which the spots in the larger cells were observed by E. Boss, Moore, and 

 Walker. 



It is, however, necessary to state that the spots are not centrosomes. At 

 first I believed them to be such, but further investigation showed the 

 suggestion to be erroneous. They are diffusion vacuoles. If the diffusion of 

 stain into leucocytes is accelerated by heat or alkali so as to cause maximum 

 staining without actually killing the cells, then stained liquid also passes into 

 the colloid cytoplasm and remains suspended in it as a " red spot." 

 A description of the nature of these spots was published in the ' Journal of 

 Physiology,' September, 1908. These vacuoles get gradually larger, and when 

 the leucocytes die, the spots suddenly disperse owing to the liquefaction of the 

 cytoplasm. 



The suggestion of E. Boss, Moore, and Walker, that if the spots could be 

 seen in the blood-platelets it would be proof of their cellular nature, was 

 evidently based on the assumption that the spots were centrosomes. Since 

 they are not centrosomes, it may be said that their appearance in the blood- 

 platelets now falls into insignificance. But the spots in the platelets also get 

 larger and then disperse after an interval, and their disappearance is practi- 

 cally coincident with the disappearance of the vacuoles in the leucocytes, 

 which is caused by the liquefaction of the cytoplasm occurring at death. 

 Morphia also causes extreme vacuolation of the leucocytes. 



As a matter of fact, studying the question from another aspect also shows 

 that their vacuolation is proof that the blood-platelets are cells. When fresh 

 blood is placed on the jelly, and no morphia is employed, the leucocytes do 

 not become extremely vacuolated, nor do the platelets develop the spots. 

 Why should morphia have this effect ? 



It was shown in a former paper* that different cells have different 

 coefficients of diffusion, and that, in blood-cells, approaching death causes a 

 lowered coefficient. It is obvious that the vacuoles will appear more readily, 

 that is, liquid will diffuse more readily into cells which have a lowered 

 coefficient of diffusion. 



It is apparent, therefore, that the blood-platelets must be cells, or rather 

 must be composed of living protoplasm, for their vacuolation is produced 

 experimentally by the action of the poison, as morphia, in causing the gradual 

 approach of death, also lowers the coefficient of diffusion. Morphia lowers 

 * ' Eoy. Soc. Proc.,' B, vol. 81, 1909. 



