264 SECRETS OF ANIMAL LIFE 



have dwelt on this popular concept of vigor not 

 because we are confident we know what vigor 

 precisely is, but because we are convinced that it 

 means more than is indicated in a recent work of 

 considerable interest which bears the title Vigor 

 and Heredity. 1 According to the author, Mr. J. 

 Lewis Bonhote, well known as an experienced orni- 

 thologist, vigor may be defined as " activity of 

 nutrition and function/' or as " rate of metabolism/' 

 It is not so much like heat as like temperature; and 

 it requires to be qualified by some adjective, as 

 " high vigor/' or " low vigor." It is the rate of 

 metabolism. Now "metabolism" is just a con- 

 venient general term for the manifold complex 

 chemical processes which go on in a living body, 

 some of them of a constructive, synthetic, upbuild- 

 ing, or assimilative character (anabolic), and others 

 of a disruptive, analytic, down-breaking or disas- 

 similative character (katabolic). But it is a very 

 wide term and includes such a variety of processes 

 that " the rate of metabolism " does not mean very 

 much. Two creatures may have the same number 

 of chemical transactions per hour, and yet have 

 very little in common from a physiological point of 

 view, just as two shops may have the same number 

 of sales in a day and yet have very little in common 

 commercially. And, again, if we measure the 

 amount of metabolism that goes on in a day in 

 various types by the amount of oxygen used up, or 



1 Vigor and Heredity. By J. Lewis Bonhote. West, New- 

 man & Co, 1915. 



