26 ARBOREAL MAN 



and ulna and radius remain in tlieir primitive condition. 

 The first row of the carpal bones articulates Avith both 

 ulna and radius, and consists of all the ideal elements; 

 radiale {scaphoid), intermedium (semilunar), and ulnare 

 (cuneiform) are all separate and normal. The os centrale 

 is present. Carpale I. (trapezium), carpale II. (trapezoid), 

 and carpale III. (os magnum) are separate, and not 

 greatly changed; carpale IV. and carpale V. are fused 

 into the unciform. The five digits are all present in a 

 very primitive condition, the pollex alone lacking one 

 of its elements. In addition to these slight modifications 

 an ulnar sesamoid (pisiform) is present. 



Now all these departures from the ideal which are 

 manifested in the Primate fore-limb are modifications 

 which have their parallels in very generalized Reptilia. 

 Fusion of carj)ale IV. and V. takes place even in the 

 very generalized chelonian carpus; in the same forms 

 also is seen the identical loss of an element in the pollex, 

 and the development of an ulnar sesamoid. Two addi- 

 tional modifications are present in Man and the giant 

 AnthrojDoids (see Fig. 8). The centrale is lost as a 

 separate element by fusion with the scaphoid (radiale) 

 in Man, the Gorilla and the Chimpanzee; this, again, is 

 a feature of some of the Lemurs and of so primitive a 

 carpus as that seen in the Chelonia. 



Persistence of the os centrale in the human carpus is 

 not an exceptionally rare anomaly, and many cases have 

 been recorded by Gruber. Rosenberg has also shown 

 its normal presence in the human embryo. Anomalies 

 of the Gorilla and Chimpanzee are naturally less well 

 known than are those of Man, but even in these animals 

 the OS centrale is known to occur exceptionally. In the 

 orang-utan and in the Gibbon it is normal and well 

 developed. 



In Man, Gorilla, Chimpanzee and Orang-utan the ulna 

 does not directly articulate with the carpus, but is ex- 

 cluded from contact with the cuneiform (ulnare) by the 



