IX.] THE DYNAMICS OF LIFE. 99 



cause of that feeling of buoyancy which makes action Buoyancy- 

 more agreeable than rest ; and deficiency of it is probably f "tig^e 

 the cause of the sensation of fatigue. And perhaps, though 

 I only offer this as a suggestion, the immediate cause of Death from 

 death by fatigue may in some cases be the want of sufficient ^ ^^^^^' 

 vital energy in the system to supply motive power for the 

 muscular work of the heart and lungs. 



It is the function of the muscles to transform vital Eelation 

 energy into motor energy ; and it appears to be one of the nervous 

 various functions of the nervoiis system to transform vital system to 

 energy into heat. We may say, indeed, that the primary j^at. 

 function of the whole nervo-muscular system, including the 

 electric apparatus of the torpedo and other electric fishes, 

 is to transform vital energy into other kinds of energy. To 

 this class of phenomena probably belongs the well-known 

 but little understood fact of the high temperature of Heat of 

 inflamed parts. This cannot be due to any increase of parts 

 chemical action ; for, contrary to what we might expect, 

 an examination of the blood that has passed through an 

 inflamed part shows that oxidation goes on not more but 

 less rapidly in an inflamed part than in a healthy one.^ 

 But the increased sensitiveness of inflamed parts shows 

 that nervous action in them must be in some way 

 heightened ; and this heightening of nervous action pro- due to 

 bably determines a conversion of vital energy into heat, action?^ 

 Sensation, however, is not what constitutes nervous action ; 

 sensation is only a concomitant of nervous action, and not Insentient 

 by any means an invariable concomitant. The nervous 

 system is primarily a part of the animal apparatus for the 

 transformation of energy ; and it is scarcely possible to 

 doubt that all excitement of the nerves, whether accom- Nervous 

 panied by sensation or not, determines the transformation ahra^g 

 of part of the stock of vital energy into some other form causes 

 of energy. If it is not transformed into motion, it is then mation'of 

 probably transformed into heat. This is in accordance ^iiergy, 

 with the analogy of other vital actions ; and, besides, there 

 is something of the nature of experimental evidence for 

 it. It is a familiar fact that severe pain often produces 



1 Beale's edition of Todd and Bowman's Physiologj'-, p. 137. 



H 2 



