34 THE DESCENT OP MAN. 



to the low eastern plains, and when now tempted down by high 

 wages to the gold-washings, they suffer a frightful rate of mor- 

 tality. Nevertheless Mr. Forbes found a few pure families which 

 had survived during two generations: and he observed that they 

 still inherited their characteristic peculiarities. But it was mani- 

 fest, even without measurement, that these peculiarities had all 

 decreased; and on measurement, their bodies were found not to be 

 so much elongated as those of the men on the high plateau; whilst 

 their femora had become somewhat lengthened, as had their tibiae, 

 although in a less degree. The actual measurements may be seen 

 by consulting Mr. Porbes's memoir. From these observations, 

 there can, I think, be no doubt that residence during many genera- 

 tions at a great elevation tends, both directly and indirectly, to 

 induce inherited modifications in the proportions of the body." 



Although man may not have been much modified during the 

 latter stages of his existence through the increased or decreased 

 use of parts, the facts now given show that his liability in this 

 respect has not been lost; and we positively know that the same 

 law holds good with the lower animals. Consequently we may 

 infer that when at a remote epoch the progenitors of man were 

 in a transitional state, and were changing from quadrupeds into 

 bipeds, natural selection would probably have been greatly aided 

 by the inherited effects of the increased or diminished use of the 

 different parts of the body. 



Arrests of Development. — There Is a difference between arrested 

 development and arrested growth, for parts in the former state 

 continue to grow whilst still retaining their early condition. 

 Various monstrosities come under this head; and some, as a 

 cleft-palate, are known to be occasionally inherited. It will 

 suffice for our purpose to refer to the arrested brain-development 

 of microcephalous idiots, as described in Vogt's memoir.'" Their 

 skulls are smaller, and the convolutions of the brain are less com- 

 plex than in normal men. The frontal sinus, or the projection 

 over the eyebrows, is largely developed, and the jaws are prog- 

 nathous to an "effrayant" degree, so that these idiots somewhat 

 resemble the lower types of mankind. Their intelligence, and 

 most of their mental faculties, are extremely feeble. They 

 cannot acquire the power of speech, and are wholly incapable of 

 prolonged attention, but are much given to imitation. They are 

 strong and remarkably active, continually gamboling and jumping 

 about, and making grimaces. They often ascend stairs on all- 

 fours; and are curiously fond of climbing up furniture or trees. 



»= Dr. Wilokens ('Landwirthschaft. Wochenblatt,' No. 10, 1869) has 

 lately published an interesting Essay showing- how domestic animals, 

 which live in mountainous regions, have their frames modified. 



3» 'Memoire sur les Microcephales,' 1S67, pp. 60, 125, 169, 171, 184-198. 



