THE BLOOD. 481 



" i. First, Major Proposition. The primary and essential part of the 

 process of coagulation consists in the evolution of a volatile prin- 

 ciple from blood. 



" [This is proved by the experiments which have gone before. These 

 have shown that coagulation is prevented by exclusion from air or other 

 gas, by cold, and by cold and pressure; and that it is retarded by motion 

 in a closed circuit, and by addition of dense fluids. Conversely, other 

 experiments have indicated that exposure to the vacuum, to the air, or 

 other gases, motion during such exposure, and increase of temperature 

 during such exposure, are each and all physical conditions which quicken 

 coagulation. 



" With the escape of a volatile agent these conditions are all in perfect 

 accord and harmony ; in the presence of any other view, they become 

 mere disjointed and even contradictory phenomena. 



" The proof is carried further still in the experiment of passing the 

 vapour of blood through blood, and in the suspension of coagulation 

 which succeeds.] 



" ii. Second Major Proposition. The volatile principle thus eliminated 

 from blood is ammonia, differing perhaps in formula in different 

 classes of animals, but serving essentially the same purpose in 

 all. 



" [This proposition is proved by two series of experiments; first, by 

 those which have shown that ammonia may be obtained from blood- 

 vapour; and secondly, by the results which follow the addition of 

 ammonia to newly drawn blood. Still further, but in the same direc- 

 tion, it is proved in the experiments of re-dissolving the blood-clot or 

 the fibrin-clot in ammonia solutions, and reproducing coagulation by 

 eliminating the ammonia. 



" Lastly, the proposition is exemplified by the experiments which show 

 that, in blood held temporarily fluid by access of ammonia, coagulation 

 is favoured or retarded by the same physical agents as those which 

 favour the normal coagulation of blood.] 



" The minor propositions which spring naturally from the foregoing, 

 are the following : 



" (a) As a result of the evolution of the volatile solvent from newly 

 drawn and liberated blood, the fibrin, which has previously been held 

 in solution in the serum by virtue of the alkalinity imparted by the 

 ammonia,- is transformed from the fluid to the solid condition; its 



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