314 BIOLOGY 



The Nervous Functions. The primary question is whether 

 there is any correlation between nervous force and other types 

 of energy. For this purpose it will be convenient to separate 

 the phenomena of simple nervous transmission from those 

 that we speak of as mental phenomena. The former are sim- 

 pler and offer the greater hope of solution. 



Nerve impulse. If we are to find any correlation between 

 nervous force and physical energy, it must be done by find- 

 ing some way of measuring nervous energy and comparing 

 it with physical energy. There has been devised as yet no satis- 

 factory way of measuring the nervous impulse directly. In the 

 experiment of keeping an individual in a large box where all of 

 the energy exhibited by his body can be carefully and accurately 

 measured, the attempt has been made to get some indication of 

 the energy involved in nervous phenomena. But the results 

 have been quite negative. When in these boxes an individual 

 simply arises from his chair, the measuring device of the ap- 

 paratus is accurate enough to show distinct indication of the 

 expenditure of energy in this very simple motion. But when 

 this person is allowed to remain seated, not performing any 

 bodily action, but working hard with his brain, as for example 

 in writing a difficult examination, there seems to be exhibited 

 no extra energy, so far as can be determined by the measure- 

 ment recorded with this apparatus. In spite of all attempts 

 that have been made, it has hitherto been impossible to get any 

 indication that the use of the nervous system involves the ex- 

 penditure of energy. This is probably due to the fact that 

 the amount of energy thus involved is altogether too small to be 

 recorded in the coarse apparatus which has been devised for use 

 in these experiments. 



That there is some correlation between nervous force and 

 physical energy is fairly well proved by experiments along 

 various lines. The impulse that passes along nerves may be 

 excited by a variety of forms of ordinary energy. Any mechani- 

 cal shock, a little heat, or an electrical shock will develop a 



