Chai\ II. Manner of Development. 35 



relation with the greatly increased length of the trunk. The 

 Aymaras present some other singular points of structure, for 

 instance, the very small projection of the heel. 



These men are so thoroughly acclimatised to their cold and 

 lofty abode, that when formerly carried down by the Spaniards 

 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 

 manifest, even without measurement, that these peculiarities 

 had all decreased ; and on measurement, their bodies were found 

 not to be so much elongated as these of the men on the high 

 plateau ; whilst their femora had become somewhat lengthened, 

 as had their tibiag, although in a less degree. The actual 

 measurements may be seen by consulting Mr. Forbes's memoir. 

 From these observations, there can, I think, be no doubt that 

 residence during many generations at a great elevation tends, 

 both directly and indirectly, to induce inherited modifications 

 in the proportions of the body. 35 



Although man may not have been much mo lifted during 

 the latter stages of his existence through the increased or de- 

 creased use of parts, the facts now given shew 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 wo 

 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 refei to the arrested brain-development 

 of microcephalous idiots, as described in Vogt's memoir. 36 

 Their skulls are smaller, and the convolutions of the brain 

 are less complex than in normal men. The frontal sinus, or the 



35 Dr. Wilckens ('Landwirth- regions, have their frames modified, 



gchaft. Wochenblatt,' No. 10, 1869) 36 'Memoire sur les Microc£- 



has lately published an interesting phales,' 1867, pp. 50, 125, 169, 171, 



Essay shewing how domestic ani- 181-198. 

 uala* which live in mountainous 



