20 THE DESCENT OP MAN. 



dentists. They are also much more liable to vary, both in structure 

 and in the period of their development, than the other teeth.''- In 

 the Melanian races, on the other hand, the wisdom-teeth are usual- 

 ly furnished with three separate fangs, and are generally sound; 

 they also differ from the other molars in size, less than in the Cau- 

 casian race." Prof. Schaaffhausen accounts for this difference be- 

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

 "always shortened" in those that are civilized," and this shorten- 

 ing may, I presume, be attributed to civilized 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 prac- 

 tice 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.* 



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

 count of only a single rudiment, namely the vermiform appendage 

 of the cascum. The ceecum is a branch or diverticulum of the intes- 

 tine, ending in a cul-de-sac, and is extremely long in many of the 

 lower vegetable-feeding mammals. In the marsupial koala it is ac- 

 tually more than thrice as long as the whole body." It is some- 

 times produced into a long gradually-tapering point, and is some- 

 times constricted in parts. It appears as if, in consequence of 

 changed diet or habits, the caecum had become much shortened in 

 various animals, the vermiform appendage being left as a rudi- 

 ment of the shortened part. That this appendage is a rudiment, we 

 may infer from its small size, and from the evidence which Prof. 

 Canestrini" has collected of its variability in man. It is occasion- 

 ally quite absent, or again is largely developed. The passage is 

 sometimes completely closed for half or two-thirds of its length, 

 with the terminal part consisting of a flattened solid expansion. In 

 the orang this appendage is long and convoluted: in man it arises 

 from the end of the short caecum, and is commonly from four to 

 five inches in length, being only about the third of an inch in 

 diameter. Not only is it useless, but it is sometimes the cause of 

 death, of which fact I have lately heard two instances: this is due 

 to small hard bodies, such as seeds, entering the passage, and 

 causing inflammation.^' 



« Dr. Webb, 'Teeth in Man and the Anthropoid Apes,' as quoted by 

 Dr. C. Carter Blake in 'Anthropological Review,' July, 1867, p. 299. 



« Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 320, 321 and 325. 



" 'On the Primitive Form of the Skull,' Eng. translat. in 'Anthropo- 

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



« Prof. Mantegazza writes to me from Florence that he has lately 

 been studying the last molar teeth in the different races of man, and 

 has come to the same conclusion as that given in my text, viz., that 

 in the higher or civilized races they are on the road towards atrophy 

 or elimination. 



*" Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 416, 434, 441. 



■" 'Annuario della Soc. d. Nat.' Modena, 1867, p. 94. 



•»M. C. Martins ("De I'TJnite Organique," in 'Revue des Deux Men- 



