IS LITE UNIVERSAL? 127 



intimate and so incessant, that we naturally think of 

 them together. Hence it arises that quite foreign 

 considerations, affecting the spiritual nature of man, 

 ever tend to exert a disturbing influence on the 

 higher questions of physiology. It is not easy to 

 keep separate in our thoughts the purely physical 

 life of the body, and the spiritual faculties of feeling 

 and will to which it is subservient. 



But distinguishing the mental and the material 

 life, and fixing our thoughts upon the body, over 

 which, as over an obedient instrument, the conscious 

 man bears sway, we may see the path to be pursued. 

 Life exhibits, not the agency of a single power, but 

 the united effects of several causes: the problem 

 of vitality requires division into various simpler 

 problems. We have to seek not the nature of an 

 invisible agent, but the demonstrable causes of a vast 

 variety of physical results. We have found, for 

 example, three prominent questions claim an answer 

 in respect to the living body : how it acts ; why it 

 grows; and whence its form? Taking these ques- 

 tions one by one, and seeking guidance from the facts 

 presented to us by nature, we have also found that 



