78 SCIENCE PROGRESS 



according to the method which is employed for their demon- 

 stration. In human blood mixed with Hayem's fluid they are 

 for the most part biconvex granular bodies about Sfi to 3'5/i in 

 length. They may be isolated, or clumped together into groups. 

 Some remain stationary ; others float freely in the slow currents 

 which are always in progress in any wet preparation. In our 

 opinion, they are entirely destitute of haemoglobin, and persist 

 after the erythrocytes are carefully haemolysed. Their behaviour 

 to stains also varies according to the nature of the fluid with 

 which blood has been mixed. With eosin they tint faintly ; but 

 pyronin, iodine-green, dahlia, Spiller's purple, methylene-blue, 

 or polychrome methylene-blue (Goldhorn) stains these bodies 

 most effectively. The reaction of Mylius for alkali in blood 

 shows that the erythrocytes appear as unstained discs, while the 

 plasma acquires a faint, and the platelets an intense, pink colour. 

 The platelets also show some degree of iodophilia, and con- 

 sequently have been described as containing glycogen. This 

 reaction, however, is, as Hiippert has shown, an inconclusive 

 test. 



In 1883 Wooldridge 1 discovered that a molecular precipitate 

 settled from iced peptone plasma. This is now known to occur 

 when blood-plasma is mixed with oxalates, citrates, or fluorides, 

 or even cooled (Biirker). This morphological separation, beyond 

 any doubt, forms the bulk, if not all, of the bodies described as 

 platelets ; and though this contention may not be universally 

 accepted, we may state that the admixture of blood with oxalates 

 is one accepted method for the demonstration of platelets 

 (Langley, W. Stirling, and Druebin). Another is the addition 

 of *6 per cent, peptone (Afanassiew, Bohm and Davidoff), while 

 A. E. Wright points out the ease with which these bodies can 

 be obtained when blood is mixed with citrates; and Biirker 2 

 simply allows a drop of blood to remain uncoagulated on a disc 

 of paraffin, when the summit of the drop is found to consist of 

 plasma with a quantity of platelets ; but from this experiment 

 we are certainly not justified in assuming that blood is not 

 rapidly dying and altering in nature, even though coagulation 

 is delayed. Whether the accumulation of platelets in an excised 

 vein (Osier), or those which collect at the damaged wall of a 



1 " Uber einen neuen Stoff des Blut-Plasmas," Du Bois Reymond's Archiv f. 

 Physiologie, 1884, and Proc. of the Royal Soc. p. 70, 1885. 



2 " Blutplattchen und Blutgerinnung," Pfluger's Archiv J. Physiologie, cii. 1904. 



