Nearly all more recent papers, on the other hand (cp. Löwit's compilation), recognise the =close connection of the blood platelets with coagulation=, first observed by Bizzozero. Whether the substance of the platelets directly yields the material for fibrin formation, as Bizzozero holds, or whether according to the observations on thrombus production of Eberth and Schimmelbusch they play but a subordinate part, is not yet decided. To enter here into the chemical side of this complicated problem, would lead us much too far, and we will only refer to a few clinical observations which illustrate the relations between the clotting power of the blood and the number of platelets it contains.
Marked =increase of the blood platelets= occurs in chlorosis (Muir) and in posthæmorrhagic anæmia (Hayem). In both conditions there is a decided =increase in the clotting power of the blood=. In contrast, is the important observation of Denys, who found in two cases of purpura, where as is well-known the =clotting power of the blood is always much lowered= or may even be entirely destroyed, only one morphological blood change, a very marked =diminution of the blood platelets=. Ehrlich likewise had occasion to examine a similar case, in which the blood platelets were entirely absent.
H. F. Müller has described a fourth formed constituent of the blood, and given it the name of "=hæmoconiæ=" or "=blood atoms=," "blood dust." It is found in the plasma of the blood as very small granule- or coccæ-like colourless corpuscles, highly refractile, with a very active molecular movement, which keep their shape under observation for a very long time without any special precautions. According to Müller these bodies are not blackened by osmic acid, and probably contain no fat; they seem to have no connection with fibrin formation, as they always lie outside the fibrin network. Müller found them in every normal blood, in varying numbers however; much increased in a case of Morbus Addisonii; diminished in hunger and cachexias.
More detailed observations are necessary to determine the chemical nature of these forms. Experiments in this direction by extraction with ether, or by the use of fat staining substances, alkanna, Soudan dye, and comparative investigations on lipæmic blood should be successful.