METABOLISM 23 



It would almost seem as if the nerves which subserve 

 the physiological function of any organ or tissue exert 

 either a promoting influence on its anabolism or a 

 restraining influence on its katabolism, with the conse- 

 quence that when the nervous influence is withdrawn or 

 perverted rapid -tissue destruction or alteration ensues. 

 It is perhaps in some such way as this that the influence 

 of emotional and mental states on local and general 

 nutrition is exerted, an influence which is shown locally 

 in the blanching of the hair from fear, and generally in 

 the promotion of fatness by cheerfulness (' laugh and 

 grow fat '), and of leanness by anxiety. Again, ' consti- 

 tutional ' as opposed to muscular strength may perhaps 

 be due, in part at least, to a firm grip of the nervous 

 system upon metabolism. Medical experience, at all 

 events, would seem to show that a strong will and 

 a cultured mind make for strength and long life, whilst 

 a weak brain and will are often accompanied by a feeble 

 general vitality. 



6. Influence of Internal Secretions. The term 

 ' internal secretion ' has come to be used in rather 

 a loose way, and in clinical medicine, at least, it is 

 often employed like the terms * reflex action,' * trophic 

 influence,' and ' toxin,' as a sort of deus ex machind to 

 explain pathological phenomena which would be other- 

 wise difficult of comprehension. It is, of course, in 

 a sense true that every tissue and organ produces an 

 'internal secretion,' inasmuch as the waste products 

 of its metabolism are turned into the blood- stream, and, 

 being diffused throughout the body, may conceivably 

 influence chemical processes in remote parts. It would 



