724 SPECIAL PHYSIOLOGY. 



the living tissues, it is the surface of the clots next in contact with those 

 living tissues, which first presents appearances of organization and 

 vascularization. This suggests the possibility that, subsequently to 

 the effusion of blood, a true plastic exudation may take place around 

 the clot, and may penetrate between the columns of its aggregated 

 corpuscles ; in this way, the apparent organization and vascularization 

 of a clot may, ultimately, be the same process as that of a fibrin ous 

 effusion, depending on formative acts on the part of the surrounding 

 cell elements, which give rise to nuclei, cells, or intercellular substance. 

 According to this view, the coagulum of the blood constitutes a sort 

 of nidus for future developmental processes, but is not itself converted 

 into tissue. The fibrillae of the coagulated fibrin may support the 

 effused mass, divide it into areolae or spaces, and thus favor the pene- 

 tration of exuded plastic matter, and the penetration of nuclear growths 

 through it. The plastic lymph, though a fibrinous material, may not 

 be identical with the solidified fibrin of the blood, but may be a true 

 protoplasm, more distinctly and positively possessed of organizable 

 tendencies, and thus of a real though low form of nutritive life. If 

 this be so, the strongest argument in favor of the vital character of 

 the coagulation of the fibrin of the blood is nullified. 



Moreover, many facts appear irreconcilable with such a doctrine. 

 Thus, the blood of a horse has been kept in a fluid state, by means of 

 nitre, for fifty-seven weeks, and yet speedily coagulated, when suf- 

 ficiently diluted with water. (Gulliver.) Frozen' blood, as already 

 stated, will coagulate when thawed. If, therefore, coagulation is a 

 vital act, the life of the blood must be admitted to be capable of being 

 " pickled" and "frozen." (Gulliver.) It is replied by the vitalists, 

 that the vitality of the fibrin is simply preserved in a dormant con- 

 dition, by the prevention of spontaneous change or decomposition ; 

 just as the dormant vitality of seeds and ova endures for years, and 

 as that of infusorial animalcules, and even of the highly organized 

 Rotifera, may be restored, after considerable elevation or lowering of 

 the temperature, or may be suspended, and so conserved by desicca- 

 tion. But the recovery of animalcules after freezing is, probably, 

 only apparent, a minute drop of surrounding unfrozen water perhaps, 

 defending them from actual congelation ; whilst in blood thoroughly 

 frozen, the fibrinous fibrillae, undergoing no nutritive changes, could 

 hardly escape that event. Furthermore, there is no example of the 

 recovery of life, by any of those minute organized beings, after im- 

 mersion in so potent a substance as a solution of nitre, which is a well- 

 known solvent of fresh fibrin. 



On the supposition that the coagulation of the fibrin is not a vital, 

 but a physical process, it has been maintained that the fibrin is held in 

 a fluid state in the living blood, by a minute quantity of ammonia, 

 and that the escape of this ammonia is the immediate cause of its co- 

 agulation at least when blood is drawn from the body. The cele- 

 brated Robert Boyle (1684) considered that the blood gave out a 

 spirit, and observed that it could be maintained in a fluid state by a 

 salt of ammonia, and that clotting occurred after the removal of this. 

 It was proved by Haller that the halitus of the blood is alkaline. Al- 



