26 THE DESCENT OF MAN. [PARr L 



are earlier lost, than the other teeth. It is also remark- 

 able that they are much more liable to vary both in struct- 

 ure and in the. period of their development than the other 

 teeth. 31 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. 32 

 Prof. Schaaffhausen accounts for this difference between 

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

 always shortened " in those that are civilized, 33 and this 

 shortening may, I presume, be safely attributed to civil- 

 ized 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 devel- 

 opment of the normal number. 



With respect to the alimentary canal, I have met with 

 an account of only a single rudiment, namely, the vermi- 

 form appendage of the caecum. The caecum is a branch 

 or diverticulum of the intestine, ending in a cul-de-sac, and 

 it is extremely long in many of the lower vegetable-feed- 

 ing mammals. In the marsupial koala it is actually more 

 than thrice as long as the whole body. 34 It is sometimes 

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

 sometimes constricted in parts. It appears as if, in conse- 

 quence of changed diet or habits, the caecum had become 

 much shortened in various animals, the vermiform append- 

 age being left as a rudiment of the shortened part. That 



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

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



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



33 « On the primitive Form of the Skull,' Eng. translat. in ' Anthro* 

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



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



