OF ANIMAL HEAT. 117 



from strictly deserving the epithet vital, because it is regulated 

 by the vital powers of the system, although through the instru- 

 mentality of chemical changes. If the high temperature of an 

 inflamed part is owing to the increased momentum of the blood, 

 yet this increased momentum is produced by the vital powers. 

 As there is less vigour in old than in young persons, and in 

 remote parts than in those which are near the centre of circu- 

 lation, the momentum of the blood is less in the old than the 

 young, and in parts remote than in parts near the heart 5 hence 

 the temperature of the old falls short of the temperature of the 

 young, and is stated to be in all persons lower in proportion to 

 the distance of parts from the centre of circulation.* 



All animate matter has a tendency to preserve a certain tem- 

 perature. Even eggs are cooled and frozen with more difficulty 

 than equal masses of inanimate matter, though, when once frozen 

 and their life destroyed, they freeze readily. f Vegetables shew 

 the same tendency by the greater difficulty with which the juices 

 in their stems and branches are frozen than lifeless fluids, and by 

 ice thawing when roots shoot into it.| 



* Dr. Davy, Philos. Trans. 1814. 



f Hunter, on the Blood, $c. p. 79. 



J American Medical and Philosophical Register. 1814. p, 19. 



