650 



CHORD AT A. 



tlie brain (fig. 040, c). They have a single pair of pectoral 

 mamni;«, utcras simplex, and a discoidal placenta. The dentition 

 is essentially the same throughout; in the Platyrrhina; flj-f, in the 

 llapalidas |y||, in the Catarrhinis and in man |y|-|. Yet there is 

 a tendency to variation, since in the chimpanzee and in man the 

 third molar (wisdom tooth) is in process of degeneration, while in 

 the orang a fourth molar often occurs. In all the molars are 

 buuodont. 



The skeleton of the hand aiid foot has played an important 

 role in classification. As in the lemurs and ojjossums, the thumb 

 and great toe can be opjiosed to the other digits, so that an ape can 

 grasp objects with either hand or foot. In man this opposability 

 of the thuml) is increased, but that of the great toe, in consequence 

 of the upright position, is only retained to a slight degree by chil- 

 dren and jirimitive people. On this peculiarity rest the names often 

 given of Biuiana, for man, and Quadrumana, for the apes and 

 monkeys. In contradiction of this it must be emjihasized that the 

 apes do not have a hand, but rather a grasping foot, on the hinder 

 extremities. In the grasping foot (fig. 673) are the same bones. 



Fia. 673. — Hand and foot of gorilla, c, oapitatum; en. calcaneus; cw, cuboid; ?i, lia- 

 niatum ; 1, luiiatum ; ?/«■, metacarpals ; iiir, metatarsals; )i, navlculare ; p, pisi- 

 forine; ph, plialanKcs ; .s, scaplmul; /, triqiietrum; /((, talus : tiU trapezoid ; tr, tra- 

 pezium; I-\\ digits; 1-3, cunuiformia. 



similarly arranged and of about the same shape as in the foot of 

 man, while tlio mnsculaturo is ossentiallv the same. On the otlier 



