184 



PHYSIOLOGY. 



that blood-plates are nucleated and contain protoplasm, with an 

 amoeboid movement. In blood that has been drawn from the vessels 

 they diminish very rapidly both in numbers and size, becoming grad- 

 ually dissolved in the plasma. They are readily seen in blood 

 treated with 1 per cent, of solution of osmic acid. 

 I As to their nature, there is some diversity of opinion, but the 

 consensus of thought seems to be in favor of the plates being formed 

 bodies, and not precipitates. They have been found to contain the 

 same elements chemically as the nuclei of the leucocytes. 



The number of blood-plates is about half a million per cubic 

 millimeter. In the defibrination of blood by whipping two periods 



J 



fc 



V'V 





Fig. 54. Blood-plates and their Derivatives. (LANDOIS.) 



1, Red corpuscle on the flat. 2, On the side. 3, Unchanged blood -plates. 

 4, Lymph-corpuscle surrounded by blood-plates. 5, Altered blood-plates. 6, 

 Lymph-corpuscle with two heaps of blood-plates and threads of fibrin. 7, 

 Group of fused blood-plates. 8, Small group of partially dissolved blood-plates 

 with fibrils of fibrin. 



can be distinguished: in the first, a thick layer of platelets collect 

 on the bunch of wires, whilst in the second these bodies coalesce into 

 a granular mass in which layers of fibrin collect. The platelets 

 have numerous processes. Blood-plates can be seen in the circulat- 

 ing blood of the bat, mouse and guinea-pig. 



Endocarditis and injury to the wall of a vein, damaging the 

 blood, gives rise to the formation of a white thrombus, which is 

 formed by an adhesion of red corpuscles to the parts. This throm- 

 bus extrudes the platelets, which consist of nucleo-proteid, and form 

 more thrombi. The function of blood-plates is to assist in coagula- 

 tion and in the formation of thrombi. Blood-plates are less in 

 purpura.. The lessened coagulability here may in part be caused by 



