6o PHYSIOLOGY 



acquisition of knowledge how best to keep the body 

 from damage as it works, active and healthy. 



The world of life falls into two provinces, plant and 

 animal. In both the same principles underlie the run- 

 ning of the machinery. In detail they diverge and in 

 practice physiology studies them to a large extent apart. 

 But one truth emerges from these allied divisions of 

 physiology taken together, and that is the manifold inter- 

 locking of the actions of plant and animal in the economy 

 of nature. As the world stands the one kind of life 

 seems impossible without the other. The evolution of 

 each has been a condition of the evolution of the other. 

 Their differences are to a large extent complemental. 

 In a plantless world the animal would die of inanition. 

 The crowning beauty of plant-life, the blossom, is mean- 

 ingless without the animal to fertilize it. 



Our glance at a great science must be brief. Perhaps 

 we may win more of its significance if we confine our 

 attempt to some single fractional problem and broadly 

 examine that. It matters little which of the innumerable 

 inquiries opened by Physiology we take. Reference was 

 made just now to the warmth of the body, and we may 

 consider that, since there is no more salient phenomenon 

 in the physiology of animals. 



Our bodily warmth is not constantly in evidence to 

 our consciousness, but the simplest observation at any 

 time suffices to demonstrate it to ourselves. We have 

 simply to touch the forehead with the finger and we 

 recognize that the body is warmer than the air in which 

 it is habitually immersed. Physiology seeks to under- 

 stand how this warmth of the body comes about, its 

 meaning in the sense of its ' how'. 



Heat is evolved in the majority of chemical reactions. 

 Experiment finds evidence that the body is the scene 



