16 THE HUMAN BODY. 



the Body offers clearly even a more complex subject of study 

 than its structure. 



Physiological Properties. In common with inanimate 

 objects the Body possesses many merely physical properties, 

 as weight, rigidity, elasticity, color, and so on; but in addi- 

 tion to these we find in it while alive many others which it 

 ceases to manifest at death. Of these perhaps the power of 

 executing spontaneous movements aiid of maintaining a high 

 bodily temperature are the most marked. As long as the 

 Body is alive it is warm and, since the surrounding air is 

 nearly always cooler, must be losing heat all day long to 

 neighboring objects; nevertheless we are at the end of the 

 day as warm as at the beginning, the temperature of the 

 Body in health not varying much from 37 0. (98.4 F.), so 

 that clearly our Bodies must be making heat somehow all 

 the time. After death this production of heat ceases and the 

 Body cools down to the temperature in its neighborhood; but 

 so closely do we associate with it the idea of warmth that 

 the sensation experienced on touching a corpse produces so 

 powerful an impression as commonly to be described as icy 

 cold. The other great characteristic of the living Body is its 

 power of executing movements; so long as life lasts it is 

 never at rest; even in the deepest slumber the regular breath- 

 ing, the tap of the heart against the chest-wall, and the beat 

 of the pulse tell us that we are watching sleep and not death. 

 If to this we add the possession of consciousness by the living 

 Body, whether aroused or not by forces immediately acting 

 upon sense-organs, we might describe it as a heat-producing, 

 moving, conscious organism. 



The production of heat in the Body needs fuel of some 

 kind as much as its production in a fire ; and every time we 

 move ourselves or external objects some of the Body is used 

 up to supply the necessary working power p just as some coals 

 are burnt in the furnace of an engine for every bit of work it 

 does; in the same way every thought that arises in us is ac- 

 companied with the destruction of some part of the Body. 

 Hence these primary actions of keeping warm, moving, and 

 being conscious, necessitate many others for the supply of 

 new materials to the tissues concerned and for the removal of 

 their wastes; still others are necessary to regulate the pro- 

 duction and loss of heat in accordance with changes in the 

 exterior temperature, to bring the moving tissues into rela- 



