124 THE IKDUCTIONS OF BIOLOGY. 



however, though the chief, is not the sole, varying relation be- 

 tween degrees of growth and amounts of expended force. Tliere 

 are two more ; one of which conspires with the last, while 

 the other conflicts with it. Consider in the first place, the 

 cost at which nutriment is distributed through the body, and 

 effete matters removed from it. Each increment of growth 

 being added at the periphery of the organism, the force ex- 

 pended in the transfer of matter must increase in a rapid 

 progression — a progression more rapid than that of the mass. 

 But as the dynamic expense of distribution is small compared 

 with the dynamic value of the materials distributed, this item 

 in the calculation is unimportant. Now consider, in the 

 second place, the changing proportion between production 

 and loss of heat. In similar organisms, the quantities of heat 

 generated by similar actions going on throughout their sub- 

 stance, must increase as the masses, or as the cubes of the 

 dimensions. Meanwhile, the surfaces from which loss of heat 

 by radiation takes place, increase only as the squares of the 

 dimensions. Though the loss of heat does not therefore in- 

 crease only as the squares of the dimensions, it certainly in- 

 creases at a smaller rate than the cubes. And to the extent 

 that augmentation of mass results in a greater retention of 

 heat, it effects an economization of force. This advantage is 

 not, however, so important as at first appears. Organic heat 

 is a concomitant of organic action, and is so abundantly pro- 

 duced during action, that the loss of it is then of no conse- 

 quence : indeed the loss is often not rapid enough to keep 

 the supply from rising to an inconvenient excess. It is only 

 in respect of that maintenance of heat which is needful during 

 qiiiescence, that large organisms have an advantage over 

 small ones in this relatively diminished loss. Thus these two 

 oubsidiary relations between degrees of growth and amounts 

 of expended force, being in antagonism with each other, we 

 may conclude that their differential result does not greatly 

 modify the result of the chief relation previously set forth. 

 Any one who proceeds to test this deduction, will find some 



