114 COAGULATION OF THE BLOOD. 



living blood as containing three leading constituents an albuminousjiq- 

 uid, fibrin dissolved therein, and the cells. The coagulation arises from 

 the tendency of the fibrin particles to agglutinate together. As this takes 

 place, the cells are caught in the meshes of the network that arises, and 

 a voluminous red clot is the result. So the serum of dead blood con- 

 tains no fibrin, and differs from the plasma of living blood in that impor- 

 tant particular. 



It has been observed that exposure to cold retards coagulation, as does 

 likewise the absence of air, or covering the blood over with a film of oil. 

 The condition of rest promotes it, as also does the presence of rough or 

 angular bodies. Blood will yield up its fibrin readily when stirred with 

 The buffy a stick. When, for any reason, the cells sink more rapidly than 

 coat usual from the surface of the blood, the fibrin of the supernatant 

 portion coagulates alone, giving rise to a stratum free from the red color, 

 and designated the bufiy coat, and on the subsequent contraction, since 

 there are no cells to hinder the fibrin, its parts upon this stratum are 

 drawn more closely together, and the clot becomes cupped. 



By those who accept figurative expressions as an explanation of phys- 

 Expianationof iological facts, the coagulation of the blood is said to be due 

 coagulation, f j{ s d ea th ; some, however, have regarded it as an abortive 

 attempt at organization, and therefore a manifestation of life. Such con- 

 tradictory explanations lose much of their interest when we examine the 

 facts of the case critically. I believe that nothing more takes place in 

 blood which has been drawn into a cup than would have taken place had 

 it remained in the body. In either case the fibrin would have equally 

 coagulated. The entrapping of the cells is a mere accident. The hourly 

 demand for fibrin amounts to 62 grains ; a simple arithmetical calculation 

 will show that the entire mass of the blood would be exhausted of all 

 the fibrin it contains in about four hours, so that the solidification of 

 fibrin must be taking place at just as rapid a rate in the system as after 

 it has been withdrawn. No clot forms in the blood-vessels, because the 

 fibrin is picked out by the muscular tissues for their nourishment as fast 

 as it is presented, nor would any clot form in a cup if we could by any 

 means remove the fibrin granules as fast as they solidified. 



That blood-fibrin differs from muscle-fibrin in certain respects is to be 

 admitted, but it does not follow that blood-fibrin is in a condition of ret- 

 rograde metamorphosis. It may require modification before it can be 

 received as the syntonin of muscles, but that such a conversion actually 

 takes place I think there can be no doubt. 



In entering on a detailed examination of the constitution and func- 

 tions of the blood, our attention will have to be directed, in the first 

 place, to the cells. It is sufficient to arrest our thoughts at once when 

 we learn that for every beat of the pulse nearly twenty millions of these 



