ITS VITAL PROPERTIES, AND RELATIONS TO LIVING ORGANISM. 193 



upon the vital relations of the Blood to the Organism at large, these being only 

 sustained whilst it is circulating in the fluid state, and being interfered with by 

 anything that favors its passage into the form which it assumes when withdrawn 

 from the body. 



181. The Coagulation of the Blood, then, consists in the 'new arrangement of 

 its constituents, which takes place when it is drawn from the vessels and is left 

 to itself, or when the body itself dies ( 138). This new arrangement essen- 

 tially depends upon the passage of the Fibrin from the soluble to the insoluble 

 state, in which it forms, not an amorphous coagulum, but a network of fibres 

 more or less definitely marked out ( 26-28) ; in the meshes of which network 

 are included the Red corpuscles, usually grouped together in columnar masses, 

 resembling piles of money. The Crassamentum or Clot thus formed becomes 

 dense, in proportion to the amount of Fibrin which it contains, and to the 

 degree of its elaboration ; and it undergoes a gradual contraction, by which the 

 Albuminous, Saline, and Extractive matters, still dissolved in the water, are more 

 or less completely expelled from it, constituting the Serum. This separation 

 will not occur, however, if the coagulation take place in a shallow vessel ; nor 

 if the amount of Fibrin should be small, or its vitality low. A homogeneous 

 mass, deficient in firmness, presents itself under such circumstances ; though the 

 solid part of this may pass into a state of more complete condensation, after the 

 lapse of a certain time. That the coagulation is due to the Fibrin, and that the 

 Corpuscles do not take any active share in the process, appears from several 

 considerations, 1 A microscopical examination of the Clot shows that it has the 

 same texture with Fibrin when coagulating by itself; the Corpuscles clustering 

 together in the interspaces of the network, and not being uniformly diffused 

 through the whole mass. Their specific gravity being greater than that of the 

 Fibrin, they are usually most abundant at the lower part of the clot ; and the 

 upper surface is sometimes nearly colorless, especially when the coagulation has 

 taken place slowly ; yet this upper part is much firmer than the under, showing 

 that the Fibrin alone is the consolidating agent. If, after the complete subsid- 

 ence of the Corpuscles, a little of the colorless Liquor Sanguinis be skimmed 

 off, it will undergo complete coagulation, forming a colorless clot ; as was long 

 ago shown by Hewson. The same fact may be experimentally demonstrated 

 by the use of methods which effect an artificial separation of the Fibrin from the 

 Corpuscles. Thus Miiller placed the blood of a Frog, diluted with water (or 

 still better, with a very thin syrup) on a paper filter, of sufficiently fine texture 

 to keep back the Corpuscles ; and the Liquor Sanguinis, having passed through 

 the filter completely unmixed with them, presented a distinct coagulum, al- 

 though, from the diluted state of the fluid, this did not possess much consistency. 

 Owing to the more minute size of the Blood-disks of warm-blooded animals, this 

 experiment cannot be so readily performed with their blood. So, again, if 

 fresh-drawn blood be continually stirred with a stick, the Fibrin will adhere to 

 it in strings during its coagulation ; and the Red corpuscles will be left sus- 

 pended in the serum, without the slightest tendency to coagulate. Moreover, 

 if a solution of any salt, that has the property of retarding the coagulation (such 

 as carbonate of potash or sulphate of soda), be added to the blood, the Corpus- 

 cles will have time to sink to the lower stratum of the fluid before the clot is 

 formed ; the greater part of the crassamentum is then entirely colorless, and is 

 found by the microscope to contain few or no red particles. It will be presently 



1 It is remarkable that this doctrine, clearly established by the older Physiologists, and 

 especially by Hewson, should ever have been put aside, even temporarily, for the untenable 

 hypothesis that the coagulation of the blood is due to a running- together of its red cor- 

 puscles. For an admirable summary of the history of opinion on this subject, see Mr. 

 Gulliver's Introduction to his edition of " Hewson' s Works" (published by the Sydenhaia 

 Society). 

 13 



