76 SCIENCE PROGRESS 



the process of inflammation. The experiments of Wlassow l led 

 him to the idea that the more fragile of the erythrocytes in 

 circulating blood shed out a nucleo-proteid which forms 

 platelets, while the remnants remained as microcytes. From 

 the fact that a vessel may be plugged by a mass of platelets, 

 Dekhuyzen 2 regards these bodies or thrombocytes as specific 

 agents which exist in blood and protect the organism against 

 accidental haemorrhage. According to this observer, in all 

 vertebrates hitherto examined with the exception of mammals, 

 a cell or thrombocyte homologous with a platelet of mammalian 

 blood is found which possesses the following features. It is 

 a non-amceboid spindle-shaped body with an oval nucleus ; the 

 protoplasm is finely granular and furnished with fine radiating 

 processes, which coalesce with those of adjacent thrombocytes. 

 They are familiar to every one as the " Spindeln " of frog's 

 blood, but are also found in worms, echinoderms, Crustacea, and 

 molluscs. Conclusions drawn from purely histological studies 

 are always to be received with caution, and we must suspend 

 our judgment before entirely accepting Dekhuyzen's views. It 

 is certain that the thrombocytes of amphibian blood are not the 

 homologues of mammalian blood-platelets (E. Neumann, J.Arnold, 

 Eisen, Lowit, Engel, Maximow, Carl Marquis, Pappenheim, E. 

 Schwalbe), if any bodies do exist which have this relationship 

 it is the plasmocytes which G. Eisen 3 has described in the blood 

 of Necturus and Amphiuma. Delezenne's discovery, confirmed 

 by every one, that blood free from tissue-lymph remains 

 unclotted, is absolutely opposed to the idea that any bodies of 

 the nature of thrombocytes can be present in normal uninjured 

 blood. 



The view of Hayem and his school that haematoblasts contain 

 haemoglobin and are the antecedents of red blood corpuscles 

 is still found in recent French text-books. All the evidence 

 adduced as to the existence, origin, and destiny of haematoblasts 

 is entirely histological, which is a most uncertain and unreliable 

 foundation for the building up of hypotheses. The methods 

 of histology are those of the morphologist and anatomist ; the 



1 " Untersuchungen iiber die histologischen Vorgange bei der Gerinnung und 

 Thrombose mit besonderer Berucksichtigung der Entstehung der Blutplattchen,'' 

 Ziegler's Beitrage, xv. 1894. 



2 " Uber die Thrombocyten (Blutplattchen)," Anatomisch.es Anseiger, xix. 1901. 



3 " On the Blood-Plates of the Human Blood, with Notes on the Erythrocytes 

 of Necturus and Amphiuma," Journal of Morphology, Boston, xv. 1899. 



