3 i6 THE POPULAR SCIENCE MONTHLY. 



should take into consideration. There are many others to which 

 I can not now refer, but which will naturally occur to the thought- 

 ful anatomist. 



In this rapid review of the physical side of our subject the 

 study of these race-characters naturally suggests the vexed ques- 

 tion as to the hereditary transmission of acquired peculiarities. 

 This is too large a controversy for us now to engage in, but in the 

 special instances before us there are grounds for the presumption 

 that these characters of microdontism and megacephaly have 

 been acquired at some stage in the ancestral history of humanity, 

 and that they are respectively correlated with diminution of use 

 in the one case and increase of activity in the other. It is a mat- 

 ter of observation that these qualities have become hereditary, 

 and the point at issue is not the fact, but the mechanism of the 

 transmission. We know that use or disuse affects the develop- 

 ment of structure in the individual, and it is hard to believe that 

 the persistent disuse of a part through successive generations 

 does not exercise a cumulative influence on its ultimate condition. 



There is a statement in reference to one of these characters 

 which has gained an entrance into the text-books, to the effect 

 that the human alveolar arch is shortening, and that the last 

 molar tooth is being crowded out of existence. I have examined 

 400 crania of men of the long- and round-barrow races, Romano- 

 British and early Saxon, and have not found among all these a 

 single instance of absence of the third molar or of overcrowded 

 teeth. On the other hand, out of 200 ancient Egyptian skulls, nine 

 per cent showed displacement or disease, and l£ per cent show 

 the want of one molar tooth. Out of 200 modern English skulls 

 there was no third molar tooth in one per cent. So far this seems 

 to confirm the current opinion. 



Yet the whole history of the organism bears testimony to the 

 marvelous persistence of parts in spite of contumely and disuse. 

 Take, for example, the present position of the little toe in man. 

 We know not the condition of this digit in prehistoric man, and 

 have but little information as to its state among savage tribes 

 at the present day, but we do know that in civilized peoples, 

 whose feet are from infancy subjected to conditions of restraint, 

 it is an imperfect organ — 



" of every function shorn 

 Except to act as basis for a corn." 



In one per cent of adults the second and third joints have anchy- 

 losed, in three per cent the joint between them is rudimentary, with 

 scarcely a trace of a cavity, in twenty per cent of feet the organ 

 has lost one or more of its normal complement of muscles. But 

 though shorn of some of its elements, and with others as mere 



