EXPLANATOEY HYPOTHESES 113 



of proportion hence arising constitutes unlikeness of 

 structure." But I have been unable to find in his 

 book any attempt to establish this general law of 

 nutrition, further than by a misleading analogy 

 between a human society and a living organism, 

 the labour and capital of the one being supposed to 

 represent the food-supply of the other. Nor do I 

 know of any experiments made to test the accuracy 

 of this so-called law ; and unless it can be supported 

 by experimental or observational evidence, the 

 ' ' law ' ' must be looked upon as an assumption 

 only. Mr. Spencer forgets that money-making is 

 a mental operation ; and if the analogy is of any 

 value, it means that assimilation is a mental opera- 

 tion also. But then he would have to shew why 

 useful organs should always have a better mental 

 endowment than useless ones ; and that would bring 

 him to the same position from whence he started. 



Professor Cope has given, as an illustration of this 

 law, the change of the skull in the early races of 

 man. He says that the orthognathism of the later 

 races was due to the increased use of the brain 

 enlarging and expanding its bony case, probably at 

 the expense of the lime-salts which would other- 

 wise have gone to the jaws ; and so the latter 

 dwindled. In other words he gives the use of the 

 brain as a reason for prognathous jaws disappearing 

 with an increasing forehead. But we know now 

 that the forehead increased most rapidly in the latter 

 half of the pleistocene period, long before progna- 

 thous jaws disappeared ; so that his illustration wi!I 

 not stand. The diminishing of the lower jaw is 



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