CHAPTER I 



BODY SIZE AS STRUCTURE AND AS 

 FUNCTION 



Every kind of living organism is distinguished by its 

 size. Size is one of the chief of its properties, and 

 the bodies of individuals belonging to one kind are 

 alike in bulk. Even a giant or a pigmy is not so differ- 

 ent from the average individual as is usually the aver- 

 age individual of another species. Among men, for 

 instance, all adults fit the same doorways and the same 

 beds; Procrustes had to be excessively particular to 

 find any cause for mutilating his victims. A hasty com- 

 parison with all men of all the inorganic objects of 

 some one kind, such as all crystals of a single kind of 

 salt, all granite rocks, or all dolomite mountains, re- 

 veals the extent to which size characterizes men. 



1. Size a Regulated Characteristic 



Metabolism and size. Uniform size of body and of 

 its parts is not, however, peculiar to living things. 

 Drops of water and grains of sand are each similar to 

 one another in volume as well as in shape. But a liv- 

 ing body does not keep its component materials as 

 does the grain of sand, nor depend upon isolation for 

 its integrity as does the drop of water. 



The organism is, in fact, continually exchanging its 

 constituents for new ones. Thus, its water is con- 

 stantly being thrown away, only to be replaced by 

 other molecules which are the same in every respect. 

 The living body is like a river; its content is ever 

 changing but its shape and its size remain unmodified 

 to any large extent. A river is contained in a bed 

 which limits it; but the mold in which the individual 



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