RESPECTING VITAL MOTION. 6 



sleep throughout the night ; and hence we may argue 

 that the vivifying rays of the sun are essential to the 

 continuance as well as to the commencement of exist- 

 ence, and that the vital movements of the lizard 

 depend, not merely upon a source and spring of action 

 that is peculiar to the creature itself, but also upon a 

 more general and comprehensive agent, which affects 

 at one and the same time the entire realm of nature. 



As in the sensitive plant and lizard, so in other 

 plants and animals, the vital movements are found to 

 refer partly to internal and partly to external agencies. 

 In some cases there may be greater energy in the 

 forces which reside within the organism ; in others the 

 influence of surrounding nature may be more power- 

 ful ; but in every case the two classes of agencies are 

 invariably associated. 



In order, therefore, to arrive at any satisfactory 

 knowledge of vital motion, it is necessary to examine 

 it in relation to cosmical as well as to organic force, 

 or rather in relation to the forces which originate 

 within and without the organism for we find, on the 

 one hand, that cosmical force pervades the organism 

 and constitutes part of its vitality, and, on the other, 

 that organic force is not restricted to the limits of the 

 body. Before we enter upon any special and syste- 

 matic enquiries, however, it may be well to endeavour 

 to obtain some preliminary information upon the mode 

 in which the bodily structures are affected by some of 



B 2 



