486 THE BLOOD. 



" From these facts it is obvious that the ammonia theory utterly failed 

 to explain the influence of temperature on coagulation. The circum- 

 stance that the liquor sanguinis was acid in this experiment is clear 

 proof that it contained no free ammonia whatever ; yet the acidulated 

 plasma was affected by cold and heat, just like ordinary blood. It re- 

 mained fluid near the freezing point, although the ammonia it originally 

 contained must have entered into combination and lost its reputed 

 power of dissolving the fibrine, and it coagulated when warmed, though 

 the ammonia, fixed by the acid, must have been incapable of evolution. 

 If the author of the ammonia theory were asked to explain why this 

 horse's blood took a quarter of an hour to coagulate, he would no doubt 

 reply that it must have contained a large amount of ammonia, requiring 

 all this time to escape. But we have seen that the acid liquor san- 

 guinis, though possessing no free ammonia at all, took as long to clot. 

 There can therefore, I think, be little question but that the slowness of 

 coagulation in the horse, compared with the rapidity of the process in 

 the sheep, and the variations met with in the human species, depend 

 not on the amount of ammonia present in the blood, but on differences 

 in its other constituents, and, speaking generally, that the theory which 

 attributes the coagulation of the blood to the escape of ammonia is 

 fallacious."* 



* "Since the above communication was made, I have seen for the first time 

 the able essay of Dr E. Briicke, which competed for the Astley Cooper 

 Prize (see Med.-Chir. Review, vol. xix.) ; and I find that the principle which 

 he advocates viz., that the fluidity of the blood within the living body de- 

 pends upon an action of the walls of the vessels upon it is supported by 

 many facts which he has observed in the chelonian reptile, very similar to 

 what I have made out in mammalia. Thus, he found that the blood re- 

 mained fluid in the heart of the turtle for days after death, and for several 

 hours after he had blown air through the veins of the neck, so as to make a 

 foamy mixture in the cavities of the organ. He also found, as had been 

 previously ascertained by Virchow and others, that after the introduction of 

 mercury into the heart the blood coagulated about the globules of the metal, 

 but not elsewhere, and this he regarded as an example of the influence of 

 ordinary matter in inducing coagulation in its vicinity. He also succeeded 

 with the following very striking experiment, which would not answer with 

 mammalia : He drew blood into a cup from the veins of a living turtle, and 

 injected it into the empty heart of another turtle just killed, and found that 

 the blood remained fluid for several hours in its new situation, instead of 

 coagulating in a few minutes as when retained in a cup. J. L." 



