EXPLANATION OF PLATES VII AND VIII 167 



In both upper and lower jaw we see the four incisors in the middle 

 (Inc. i, Inc. 2) ; on each side of them is the conical crown of a canine 

 a tooth which is greatly enlarged in the ape (see PL VIII), but 

 is no larger proportionately than it is here even in the most ancient 

 known human jaw, that from the Pleistocene of Heidelberg (see 

 'Science from an Easy Chair,' Methuen, 1910, p. 405). The two 

 small bicuspid " premolars " and the three large molars follow these 

 on each side in each jaw. The crown of the most anterior (or 

 " first "j molar of the upper jaw has four cusps, tubercles, or cones on 

 it. It is '' quadri-tuberculate." The second and the third molars of 

 the upper jaw have three such prominent tubercles (excluding a row of 

 small tubercles on the hinder margin of the second) ; they are, in fact, 

 tri-tuberculate ; whilst the two hindermost molars of the lower jaw 

 have four tubercles and are called quadri-tuberculate. The first molar 

 (M 1 ) of the lower jaw has in this specimen five tubercles. In 60 per 

 cent, of European lower jaws this is the case. But in 40 per cent, this 

 tooth is quadri-tuberculate (see PI. IX). In Polynesians, Chinese, 

 Melanesians and negroes five tubercles are found on this tooth in 90 

 per cent, of the jaws examined. The apes are characterised by five 

 tubercles on this tooth, and they are found also on the first lower molars 

 of prehistoric men. Four tubercles only on this tooth is a departure 

 from the ape's condition and is found more frequently in Europeans. 



It is obvious that these big molar teeth, as well as the two smaller 

 ones in front of them on each sice of each jaw, are adapted for breaking 

 up rather soft, pulpy food, and not for cutting lumps of bone or raw 

 flesh, as are the molars of the clouded tiger (identical with those of all 

 species of the genus Felis), shown in Figs. 26 and 27, pp. 160, 161, 

 nor for rubbing grain, grass or herbage to a paste, as are those of 

 the goat (Fig. 22), those of the coypu rat (Fig. 24), and those of the 

 elephants and mastodons (Fig. 13). 



PLATE VIII. Drawings of (i) the upper and (2) the lower series of teeth of 

 the Gibbon (Hylobates concolor),one of the anthropoid or most man-like 

 apes (enlarged by one third). If these drawings are compared with 

 those in PI. VII, showing man's teeth, the most striking difference seen 

 is that the " arch " or series of teeth is here elongated and squared, not 

 rounded in front, whilst there is plenty of room in both jaws for the last 

 or wisdom tooth, which is not the case in modern races of men, though 

 in the ancient Neander man's jaw and in that from Heidelberg there 

 is ample space for the last molar as in the apes. The next most 

 important difference is that in the gibbon the four canine teeth are 

 very large and tusk-like, and must certainly be of value as weapons 

 of attack which man's are not. Connected with the large size of 



