20 



The Descent of Man. 



Part I 



been assured Ivy a surgeon to a hospital for children, have theii 

 backs covered by rather long silky hairs ; and such cases pro- 

 bably come under the same head. 



It appears as :f the posterior molar or wisdom-teeth were 

 tending to become rudimentary in the more civilised races of 

 man. These teeth are rather smaller than the other molars, as 

 is likewise the case with the corresponding teeth in the chim- 

 panzee and orang ; and they have only two separate fangs. 

 They do not cut through the gums till about the seventeenth 

 year, and I have been assured that they are much more liable to 

 decay, and are earlier lost than the other teeth ; but this is denied 

 by some eminent dentists. They are also much more liable to 

 vary, both in structure and in the period of their development, 

 than the other teethe In the Melanian races, on the other 

 hand, the wisdom-teeth are usually furnished with three 

 separate fangs, and are generally sound ; they also differ from 

 the other molars in size, less than in the Caucasian races. 42 

 Prof. Schaaffhausen accounts for this difference between the 

 races by " the posterior dental portion of the jaw being always 

 " shortened" in those that are civilised, 44 and this shortening may, 

 I presume, be attributed to civilised men habitually feeding on 

 soft, cooked food, and thus using their jaws less. I am informed 

 by Mr. Brace that it is becoming quite a common practice in the 

 United States to remove some of the molar teeth of children, as 

 the jaw does not grow large enough for the perfect development 

 of the normal number. 45 



With respect to the alimentary canal, I have met with an 

 account of only a single rudiment, namely the vermiform append- 

 age of the caecum. The caecum is a branch or diverticulum of 

 the intestine, ending in a cul-de-sac, and is extremely long in 

 many of the lower vegetable-feeding mammals. In the marsupial 

 koala it is actually more than thrice as long as the whole body. 48 

 It is sometimes produced into a long gradually-tapering point, 

 and is sometimes constricted in parts. It appears as if, in con- 

 sequence of changed diet or habits, the caecum had become much 



42 Dr. Webb, 'Teeth in Man and 

 the Anthropoid Apes,' as quoted by 

 Dr. C. Carter Blake in ' Anthropo- 

 logical Review,' July 1867, p. 299. 



43 Owen, ' Anatomy of Verte- 

 brates,' vol iii. pp. 320, 321, and 

 325. 



44 ' On the Primitive Form of the 

 Skull,' Eng. translat. in 'Anthropo- 

 logical Review,' Oct. 1868, p. 426. 



45 Prof McEte^rzza writer to me 



from Florence, that he has lately 

 been studying the last molar teeth 

 in the ditFerent races of man, and 

 has come to the same conclusion as 

 that given in my text, viz., that in 

 the higher or civilised races they 

 are on the road towards atrophy oi 

 elimination. 



46 Owen, ' Anatomy of Verte- 

 brates,' vol. iii. pp. 416, 434, 441. 



