484 THE BLOOD. 



except immediately at the spot where the injury had been inflicted, it 

 was obvious that the introduction of the wire could not affect the 

 amount of ammonia in the blood; and from this and many other facts 

 to which I need not here allude,* I was led to the opinion, that as re- 

 gards what takes place within the living vessels, the ammonia theory 

 might practically be left entirely out of consideration, 



" What I have to show this evening will, I think, prove that even for 

 blood outside the body, the ammonia theory, whatever degree of truth 

 it may contain, is very far indeed from representing the whole truth. 



" One of the most remarkable circumstances connected with blood 

 that has been shed from the vessels is, that it refuses to coagulate below 

 a temperature of 40 Fahr. or thereabouts. This is explained by Dr 

 Richardson on the hypothesis, that the low temperature prevents the 

 evolution of ammonia,t while the rapidity with which coagulation takes 

 place at high temperature seems to him satisfactorily accounted for by 

 the increased volatility exhibited by the ammonia under such circum- 

 stances. I was myself at first disposed to accept this interpretation ; 

 but subsequent reflection led me to think that, to say the least, it 

 required confirmation. It occurred to me, that if it were true that 

 the fluidity of blood below 40 was due to free ammonia retained in it, 

 coagulation would take place immediately, in spite of the cold, if the 

 alkali were neutralized by the addition of acid, provided the fibrine 

 were not impaired in its coagulating property by the reagent employed. 

 In order to ascertain whether this result would really follow, I poured 

 blood freshly shed from a sheep into vessels surrounded by ice-cold 

 water, and by this means succeeded in keeping some portions of it 

 fluid for a considerable time, and found that it continued liquid not- 

 withstanding the additon of dilute acetic acid in what I supposed must 

 be sufficient quantity to overcome the feeble alkalinity of the blood, 

 while the acidulated specimen retained the property of coagulating very 

 rapidly when raised in temperature. But on attempting to discover 

 whether this blood was really acid in reaction, I found that its red 



* For some of these facts see Philosophical Transactions for 1859, pp. 

 673, et seq. 



t See Dr Richardson's Astley Cooper Prize Essay, p. 303, where a fact if 

 mentioned, indicating that no ammonia was given off at 34 Fahr. from a 

 specimen of blood which had been artificial^ arumoniated, and which at 96 

 afforded distinct evidence of evolution of the alkali. 



