82 SCIENCE PROGRESS 



cannot be regarded as otherwise than damaging to blood. The 

 idea of all, and the contention of most of these observers is 

 that pre-existing bodies which otherwise easily disintegrate 

 are preserved, but this view that the platelets rapidly disappear 

 is not in accord with the facts. 



Any one who repeats the simple procedure suggested by 

 Biirker, in which a drop of blood is allowed to fall on a disc 

 of paraffin and any evaporation checked by placing the 

 preparation in a moist chamber, can see that the blood remains, 

 if not unaltered, at any rate unclotted for half an hour or longer, 

 during which time the corpuscles settle and leave a cap of 

 plasma loaded with platelets at the summit of the drop. 



Moreover, it is easy to see that bodies which all observers 

 would recognise as the blood-platelets figured by Hayem, 

 Schiefferdecker, and Bizzozero actually form when, under the 

 microscope, a drop of fresh human blood comes in contact 

 with any one of the fluids which are considered to fix them. 

 We are satisfied that a variable length of time, ranging from 

 about .five seconds to a minute according to the fluid used, 

 elapses between the contact of the fluids and the appearance 

 of the platelets at the contact edges, and the only inference 

 which appears reasonable is that these bodies arise as the 

 result of damage to the blood by the sublimate, iodine, formol, 

 or peptone, which may be in the so-called fixing fluids. More- 

 over, the number is at first small, but subsequently increases 

 as the fluids become more intimately mixed. This observation 

 can be carried out in a variety of ways, and with i per cent, 

 potassium oxalate the phenomenon is particularly well seen. 

 The experiment uniformly fails with the blood of birds, fish, 

 or frogs; for Amphibia this fact has been established by Lowit 

 and Druebin. 1 Neither of these observers, nor Mosen, 2 could 

 obtain any evidence of blood-platelets in the lymph. 



That amphibian blood yields no platelets similar to those of 

 mammalian blood, though Eisen considers that the plasma- 

 cytes shed out of haemic cells of Necturus are similar, may be 

 explained by the great differences which exist between the 

 proteid quotients of mammalian and amphibian blood-plasma; 



1 " Uber Blutplattchen des Saugerthieres und Blutkorperchen des Frosches," 

 Du Bois ArcJiiv f. Physiologie, Suppl. 1893. 



2 "Die Herstellung wagbarer Mengen von Blutplattchen," Du Bois ArcJiiv f. 

 Physiologie, 1893 (full literature). 



