66 THE ACTIVE FORCES OF LIVING ORGANISMS 



factors in determining the nature and rate of meta- 

 bolism, for these constitute the environment of the 

 nerve-cell and in a great measure influence the character 

 of its vibrations. 

 Theinflu- Although the beneficial effects of a slight rise in 



enoe of a ° " . 



place may altitude and the opposite effects of a great rise may 



be trans- i ■ n i r • 



mitted to a considerable extent be explained by referring 

 the ether, them to the Variations in the relative amounts of 

 carbonic acid and oxygen in the blood, yet there are 

 cases in which the solution of the problem must be 

 sought in the influence of other factors. Kesidenee 

 on the top of a hill at a comparatively low level is 

 frequently more bracing in its effects than a sojourn 

 of the same duration in a hill-encircled valley far 

 above it in height. Moreover, the beneficial influence 

 which a situation of the former kind exerts on many 

 constitutions is not of an evanescent character, and 

 is often connected with a rise above sea-level so slight 

 as to be quite inappreciable from the point of view 

 of diminished atmospheric pressure. It has been 

 suggested that such results are due to electrical 

 influences. The degree of negative attraction of the 

 earth varies, it is said, very considerably in different 

 situations. Those which are free, open, and elevated 

 as compared to the surrounding land are less negative 

 than those which are low-lying, damp, and encircled 

 by high hills. If we look upon electricity as being 

 a mode of motion of the ether, and the latter as a 

 great and universal medium whereby matter in one 

 form or amount influences matter in another form or 



