454 HUMAN DENTITION. 



or Orang, owing to the slow attainment of maturity characteristic] 

 of the Human species, and the longer interval which elapses be- 

 tween the acquisition of the first and the last true molars, than inj 

 the highest Quadrumanes. In the last true molar, called from its late 

 appearance, the "dens sapientiae" or wisdom-tooth, the two inner 

 tubercles are blended together, and a fissure extends, in many in- 

 stances, especially in the Melanian varieties, from the middle of the 

 grinding surface, at right angles to that dividing the two outer 

 cusps, to the posterior border of the tooth. 



The first upper molar is always implanted by three diverging 

 fangs, two external and one internal. The second molar is usually 

 similarly implanted, but the two outer fangs are less divergent, are 

 sometimes parallel (PI. 118, fig. 2), and occasionally connate 

 (ib. fig. 3) ; this variety appears to be more common in the 

 Caucasian than the Melanian races. The tw^o outer fangs of the 

 last molar tooth are more commonly connate or confluent, and 

 sometimes also the inner fang is blended with them into one 

 simple root, in the Caucasian race : but I have never seen these 

 varieties in the Melanian races ; and in the Australians the 

 wisdom-tooth has always presented the same three-fanged implan- 

 tation as in the Chimpanzee and Orang. 



The crowns of the inferior true molars are quinque-cuspid, 

 the fifth cusp being posterior and connected with the second 

 outer cusp : it is occasionally obsolete in the second molar. The 

 four normal cusps are defined by a crucial impression, the pos- 

 terior branch of which bifurcates to include the fifth cusp ; this 

 bifurcation being most marked in the last molar where the fifth 

 cusp is most developed. In the first molar a fold of enamel ex- 

 tending from the inner surface to the middle of the crown is the 

 last to disappear from the grinding surface in the course of abra- 

 sion. (1) The wisdom-tooth is the smallest of the three molars in 

 both jaws, but the difference, is less in the Melanian than the 

 Caucasian races. Each of the three lower molars is inserted by 

 two sub-compressed fangs, grooved along the side turned towards 

 each other : this double implantation appears to be constant in the 

 Melanian, especially the Austrahan race, in which the true molars 



a) Pi. 120, rig, 1, m, 1. 



