OF VITAL MOTION. 33 



I. OF MOVEMENTS IN THE CAPILLARY VESSELS. 



1. Of extra- organic force as the agent in these 

 movements. 



The changes in the life of hybernating animals are 

 the grand test of the operation of these forces upon 

 the vascular system, for this strange faculty is to be 

 referred simply to the conditions in which the life is 

 passed, and not to any peculiarity in the nature of this 

 life. A common squirrel, for example, which hybernates 

 in high northern latitudes no longer does so if it be 

 removed to a warm climate ; but he returns to his old 

 habit if again restored to his former home : and this 

 is the common experience of all creatures which 

 exhibit these phenomena. Nor is there any peculiarity 

 in the organization of these animals, except perhaps 

 a greater delicacy of constitution; for of several 

 animals to all appearance precisely similar, some are 

 found subject to periodical torpidity, and others not, 

 and so we may argue that their strange suscepti- 

 bility to the influence of forces foreign to the organism 

 is merely an exaggerated expression of a sensibility 

 which pervades animate nature. 



The manner in which the vessels are affected by 

 these forces may be illustrated by other facts. If, for 

 example, the hand be held to the fire it becomes 

 flushed with blood, and this condition may increase 



D 



