THE UNIQUENESS OF THE INDIVIDUAL 



ments of this kind are part of the ordinary maintenance charges 

 of the body: they are not accompanied by any net change of 

 size. But some forms of wastage are integral with the act of 

 growing. Bony tubes and boxes Kke the long bones of the legs 

 and the cranium are hollowed out on the inside in the course of 

 growing larger. The only growth which is purely additive or 

 accretionary is that of which the product takes no further part 

 in the physiological activity of the body, as with shells or hair. 

 The idea that the growth of organisms can be likened to, for 

 example, the growth of houses is not acceptable even in the 

 roughest first approximation. The two processes have nothing 

 in common at all. 



In spite of the complexity of growth, its outcome, as we 

 measure it, may be comparatively simple, and in later para- 

 graphs I shall set out some of the quantitative rules to which 

 growing animals conform. The measurements I shall refer to 

 tell one no more and no less about growth than could be 

 learned of the mechanism of respiration by measuring the 

 composition of inspired and expired air, or of a firm's 

 method of conducting business by contemplating a single 

 figure representing its annual net loss or gain. In all such 

 cases we have to do with measuring the final outcome of 

 covert processes of formidable complexity. The measurements 

 are not very deeply informative, but the information which 

 they contain is indispensable. 



THE SCALE OF SIZES 



The largest adult mammals are about 50 million times larger 

 than the smallest. A fully grown blue whale weighs about 

 2 X 10^ grammes; one of the smallest mammals, the long-tailed 

 shrew Cryptotis parva parva, weighs only about four. Even 

 when studied under conditions ''particularly conducive towards 

 repose** this shrew ate its own weight of worms and insects 



110 



