88 THE BODY AT WORK 



refuse. Even the vermiform appendix may have its use. 

 Dr. GaskelPs theory of the thyroid gland involves a transfor- 

 mation so fantastic that it would provoke a smile of incredulity 

 were we to set it forth without a prologue far more lengthy 

 than our space permits. Yet Dr. Gaskell may be right. We 

 can but guess as to the nature of the prime functions of the 

 thyroid and parathyroids. For many geological epochs they 

 have not been exercised. But whatever else they did when 

 they were indispensable constituents of the organism, their 

 activity was accompanied by the secretion of colloid. Colloid 

 is not made by other organs ; therefore the otherwise obsolete 

 thyroids are retained. It is of course not impossible that, in 

 a certain degree, Nature, like a thrifty housewife, finds a new 

 use for superseded apparatus ; but we are probably justified 

 in believing that the use is never really new. Not wanting 

 the organ for its original specific purpose, Nature relegates 

 to it alone work which hitherto it had shared with other of 

 her tools. 



A comparatively short while ago the attention of physi- 

 ologists was wholly concentrated upon the obvious or prime 

 functions of organs. Muscles contracted. The stomach 

 digested. The pancreas secreted pancreatic juice. The brain 

 made thought. Now they understand, to put it somewhat 

 metaphorically, that gastric juice is made in the calves of the 

 legs ; the ferment of pancreatic juice in the small intestine ; 

 thought of a certain emotional quality in the large intestine. 

 The chemistry of the laboratory is far behind the body's 

 chemistry. We cannot detect in the blood coming from con- 

 tracting muscles the stimulant possibly a precursor of pepsin 

 to which the stomach reacts, although the magical benefit of 

 exercise seems to prove that there is a chemical connection 

 between the activity of the muscles and the activity of the 

 glands of the alimentary canal. It has been proved by experi- 

 ment that a substance produced in the epithelium of the small 

 intestine is the messenger upon whose call depends the potency 

 of pancreatic juice. The clearing of the brain effected by a 

 judicious pill shows that poisons of some kind are absorbed 

 into the blood from an overloaded large intestine. None of 

 the organs lives altogether for itself. The chemical products 

 which it throws off, absorbed by the blood, regulate the 



