THE BLOOD-PLATELETS 79. 



blood-vessel, and are the foundation for a white thrombus, are 

 comparable to Wooldridge's bodies, must remain at present 

 uncertain ; but as far as aspect and staining properties are 

 concerned, this question might well be answered in the affirma- 

 tive. Comparatively few observers have attempted an answer 

 to the question whether the " Bliitplattchen " described by 

 various histologists are or are not identical with the granular 

 material which forms in plasma ; but we may call to mind that 

 Wooldridge considered this molecular precipitate was a mass 

 of platelets, and believed these coalesced into rosette-shaped 

 bodies, which, except in colour, closely resembled red blood- 

 corpuscles. 



The claim made by Bizzozero that platelets form definite 

 morphological elements in living unmixed blood has met with 

 considerable hostile criticism. M. Lowit and Wlassow in 

 particular denied that they existed in normal blood. Both 

 these observers maintained that shed blood protected against 

 the contact of glass by the use of liquid paraffin or castor oil 

 (Lowit) or a mixture of paraffin and vaseline (Wlassow) showed 

 none, or exceeding few, platelets. According to Lowit these 

 bodies are separations from the plasma, and in Wlassow's view 

 this procedure hinders their formation from the erythrocytes. 

 In our observations these experiments, when carried out exactly 

 as they were described, yielded specimens free from any 

 platelets, and we have noticed the same fact when human blood 

 was examined as a thin stretched film on a loop of platinum wire 

 in a moist chamber at 36° C. Wlassow believes that these bodies 

 originate from erythrocytes, a view which assumes that many of 

 the red corpuscles are somewhat fragile bodies ; but this can 

 scarcely be the case, for, as Karl Boden x has shown, the 

 erythrocytes are the most resistant of all the morphological 

 constituents of shed blood. He collected blood in sterile 

 tubes, and found that the granular leucocytes, lymphocytes, 

 and red corpuscles constantly disintegrated within a definite 

 time — even after a hundred days many red corpuscles remained 

 undamaged — and he considered that these were the most 

 resistant to destruction of all the cells of the blood. 



The evidence as to the pre-existence of the platelets in the 

 normal living blood of mammals rests on comparatively few 



1 " Die morphologischen und tinctorfellen Veranderungen nekrobiotischer 

 Blutzellen," Virch. Archiv, clxxiii. 1903. 



