GROWTH. 153 



smaller rate than the cubes. And to the extent that aug- 

 mentation 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 produced 

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

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

 supply from rising to an inconvenient excess. It is chiefly 

 in respect of that maintenance of heat which is needful 

 during quiescence, that large organisms have an advantage 

 over small ones in this relatively diminished loss. Thus 

 these two subsidiary relations between degrees of growth and 

 amounts of expended force, being in antagonism, we may 

 conclude that their differential result does not greatly modify 

 the result of the chief relation. 



Comparisons of these deductions with the facts appear in 

 some cases to verify them and in other cases not to do so. 

 Throughout the vegetal kingdom, there are no distinct limits 

 to growth except those which death entails. Passing over a 

 large proportion of plants which never exceed a comparatively 

 small size, because they wholly or partially die down at the 

 end of the year, and looking only at trees that annually send 

 forth new shoots, even when their trunks are hollowed by 

 decay; we may ask How does growth happen here to be 

 unlimited? The answer is, that plants are only accumula- 

 tors : they are in no very appreciable degree expenders. As 

 they do not undergo waste there is no reason why their 

 growth should be arrested by the equilibration of assimilation 

 and waste. Again, among animals there are sufficient 



reasons why the correspondence cannot be more than approxi- 

 mate. Besides the fact above noted, that there are other 

 varying relations which complicate the chief one. We must 

 bear in mind that the bodies compared are not truly similar : 

 the proportions of trunk to limbs and trunk to head, vary 

 considerably. The comparison is still more seriously vitiated 

 by the inconstant ratio between the constituents of which 



