86 SCIENCE PROGRESS 



platelets, all the forms can be and actually are derived from 

 the erythrocytes, a view which is largely founded upon the 

 appearances of the detached fragments of red cells, which are 

 very similar to the platelets described by Deetjen. Such 

 fragments occur in quantities when dogs are treated with small 

 doses of toluylenediamine. 



Fourth View. — From a lengthened series of observations on 

 human blood, together with a consideration of the literature, 

 we incline to the view that the platelets cannot be regarded as 

 genuine morphological constituents of the blood ; but under 

 pathological conditions large numbers are to be found in the 

 circulation. They are destitute of haemoglobin. Shed blood 

 at first shows few or no platelets. The admixture of fixing 

 fluids damages the blood, and produces platelets which had 

 no pre-existence. These platelets vary in size and shape, and 

 the centre may react to stains in such a way as to contrast with 

 the peripheral parts of the body. Human leucocytes of normal 

 blood are resistant cells, and the same is true of the erythrocytes. 

 It is much easier to haemolyse the latter than to fragment them, 

 for in order to effect this, even pressure is inefficient, but 

 reagents such as chromic acid or Wlassow's fluid can give rise 

 to such fragments (Wlassow-Sacerdotti phenomenon). 1 Since 

 no actual damage of the blood-cells can be observed to take 

 place when, for example, Hayem's or Afanassiew's fluid or 

 oxalates is added to blood, we are compelled to believe that 

 the blood-plasma is the chief, if not the exclusive, source of the 

 platelets. The essential cause of the appearance of these bodies 

 is either damage to the plasma or removal of blood from the body. 

 A temperature below that of the body is favourable to their 

 appearance. The peculiar shapes assumed by the platelets, 

 which are such that they appear to be genuine amoeboid cells, 

 cannot be regarded as a criterion of their independent character, 

 for absolutely amorphous bodies can be observed to become 

 transformed to Osier's platelets, or to those figured by Deetjen, 

 Puchberger, and others. 



A partial compromise between these various views is that the 

 blood contains two kinds of platelets, which have been termed 

 true and false ; the former would correspond to the Blutplattchen, 

 and, either as cells or cell-fragments, rank as actual constituents 

 of the blood ; while the latter would comprise the separations 



1 Sacerdotti, " Erythrocyten und Blutplattchen," Anat. Ameiger, xvii. 1900. 



