68 THE DESCENT OF MAN 



olianging from quadrupeds into bipeds, natural selection 

 would probably bave been greatly aided by tbe inherited 

 effects of the increased or diminisbed use of tbe different 

 parts of tbe body. 



Arrests of Development. — Tbere is a difference between 

 arrested development and arrested growtb, for parts in tbe 

 former state continue to grow wbile still retaining their 

 early condition. Various monstrosities come under this 

 bead; and some, as a cleft-palate, are known to be occa- 

 sionally 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 complex than in 

 normal men. The frontal sinus, or the projection over the 

 eyebrows, is largely developed, and the jaws are prognathous 

 to an "effrayanf degree; so that these idiots somewhat re- 

 semble 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 incapa- 

 ble of prolonged attention, but are much given to imitation. 

 They are strong and remarkably active, continually gambol- 

 ling and jumping about, and making grimaces. They often 

 ascend stairs on all-fours, and are curiously fond of climbing 

 up furniture or trees. We are thus reminded of the delight 

 shown by almost all boys in climbing trees; and this again 

 reminds us how lambs and kids, originally alpine animals, 

 delight to frisk on any hillock, however small. X^diots also 

 resemble the lower animals in some other respects; thus 

 several cases are recorded of their carefully smelling every 

 mouthful of food before eating it. One idiot is described as 

 often using his mouth in aid of his hands wbile bunting for 

 lice. They are often filthy in their habits, and have no sense 

 of decency; and several cases have been published of their 

 bodies being remarkably hairy. " 



36 "Memoire sur les Microcephales, " 186t, pp. 50, 125, 169, 111, 184-198. 



^' Prof. Layeook sums up the character of brute-like idiots by calling them 



theroid; "Journal of Mental Science," July, 1863. Dr. Scott ("The Deaf and 



