22 APPLIED PHYSIOLOGY 



bolism the physiologist has also little to tell us, although 

 from the clinical point of view there is evidence that 

 such an influence must be exerted in no small measure. 

 How else is one to explain the chronic malnutrition so 

 often met with in neurasthenic subjects, and which may 

 exist quite apart from any disturbance of digestion ? In 

 the acute forms of neurasthenia, indeed, a patient may 

 emaciate rapidly even although he be taking a fair 

 amount of food. There is one way in which it is 

 obvious that nervous control can influence the amount 

 of general metabolism. The maintenance of ' tone ' in 

 the muscles is one of the functions of the nervous 

 system, but ' tone ' involves chemical transformations in 

 the muscle akin to those which take place in contraction, 

 though doubtless less in degree. The greater the degree 

 of tone in the muscles, then, the greater their consump- 

 tion of energy, and it is noteworthy that in many neurotic 

 subjects there is evidence, from an exaggeration of the 

 tendon reflexes, of the presence of an abnormal degree 

 of ' tone.' On the other hand, flaccid paralysis of any 

 large number of muscles must lessen metabolism, just 

 as it has been found experimentally that poisoning with 

 curare does. These nervous influences upon metabolism 

 are apparently exerted through the medium of the 

 ordinary nerve fibres which are concerned in calling 

 into play the functional activity of the tissue concerned 

 (e.g., in the case of the muscles, the motor nerves, in 

 the case of glands the secretory), and not through any 

 special trophic fibres, for the existence of these though 

 often assumed clinically has never yet been proved 

 physiologically. 



