128 THE INDUCTIONS or BIOLOGY. 



the differences between the sizes of organisms, has yet to be 

 considered. TV r e are introduced to it by pushing the above 

 inquiry a little further. Small animals have been shown to 

 possess an advantage over large ones, in the greater ratio 

 which, other things equal, assimilation bears to expenditure: 

 and we have seen that hence, small animals in becoming 

 large ones, gradually lose that surplus of assimilative power 

 which they had, and eventually cannot assimilate more than 

 is required to balance waste. But how come these animals 

 while young and small, to have surplus assimilative powers ? 

 Have all animals equal surplus of assimilative powers ? 

 And if not, how far do differences between the surpluses de 

 termine differences between the limits of growth ? We 

 shall find in the answers to these questions, the interpretation 

 of many marked contrasts in growth that are not due to any 

 of the causes above assigned. For example, an ox immensely 

 exceeds a sheep in mass. Yet the two live from generation 

 to generation in the same fields, eat the same grass and tur 

 nips, obtain these aliments with the same small expenditure 

 of force, and differ scarcely at all in their degrees of organiz 

 ation. AVhence arises, then, their striking unlikeness of bulk ? 



AVe noted when studying the phenomena of growth in 

 ductively, that organisms of the larger and higher types, com 

 mence their separate existences, as masses of organic matter 

 having tolerable magnitudes. Speaking generally, we saw 

 that throughout each organic sub-kingdom, the acquire 

 ment of great bulk occurs only where the incipient bulk 

 and organization are considerable ; and that they are the 

 more considerable in proportion to the complexity of the life 

 which the organism is to lead. 



The deductive interpretation of this induction may best be 

 commenced by an analogy. A street orange- vendor makes 

 but a trifling profit on each transaction ; and unless more 

 than ordinarily fortunate, he is unable to realize during 

 the day a larger amount than will meet his wants : leav 

 ing him to start on the mcrrow in the same condition as 



