COAGULATION OF THE BLOOD. 



261 



Fig. 88. 



takes place the blood-globules have subsided from the upper part of the 

 fluid, leaving a layer at the surface which is colorless and partly trans- 

 parent, but which is as firmly coagulated as the rest. Thirdty, if horse's 

 blood be freshly drawn into such a vessel, surrounded by a freezing 

 mixture and kept at the temperature of (32 F.), coagulation is for 

 the time altogether suspended, and the globules sink toward the bottom, 

 leaving a transparent colorless fluid above. If this colorless fluid be 

 removed by decantation, and allowed to rise in temperature a few de- 

 grees, it coagulates firmly like fresh blood. 



These facts show that the blood-globules take no direct part in the 

 process of coagulation; and that, when present, they are simply en- 

 tangled mechanically in the solidifying clot. 



Finally, if the freshly drawn blood of man, or of any of the warm- 

 blooded animals, be briskly stirred with a bundle of twigs or glass rods, 

 the fibrine coagulates in comparatively small mass upon the surface of the 

 foreign bodies ; and the red globules which it entangles may be removed 

 by washing, without changing in any way its essential characters. 



It is the fibrine, therefore, which, by its own coagulation, induces the 

 solidification of the entire blood. As it is uniformly distributed before- 

 hand throughout the blood, when coagulation 

 takes place the minute filaments which make 

 their appearance in it entangle in their meshes 

 the globules and the albuminous fluids of the 

 plasma. A very small quantity of fibrine, 

 therefore, is sufficient to include in its solidifi- 

 cation all the fluid and semi-fluid ingredients 

 which were before mingled with it, and to 

 convert the whole into a voluminous, trem- 

 bling, jelly-like mass of coagulated blood. 



As soon as the coagulum has fairly formed, 

 it begins to contract, increasing somewhat in 

 consistency as it diminishes in size. By 

 means of this contraction the albuminous liquids begin to be pressed 

 out from th^e meshes in which they were entangled. A few isolated 

 drops first appear on the surface of the clot, 

 which soon increase in size and also become 

 more numerous. After a time they enlarge so 

 much as to come in contact with each other 

 at various points, when they coalesce, extend- 

 ing in all directions as the exudation increases, 

 until the whole surface of the clot is covered 

 with a thin layer of fluid. The clot at first ad- 

 heres pretty strongly to the sides of the vessel 

 into which the blood was drawn; but as its 

 contraction goes on, its edges are separated, 



and the fluid continues to exude between it and showing the clot contracted 

 the sides of the vessel. This process continues 



Bowl of recently OOAGTT- 

 LATKD BLOOD, showing the 

 whole mass uniformly solidi- 

 fied. 



Fig. 89. 



