THE ENDOSKELETON 



181 



Aside from the normal bones in carpus and tarsus there 

 occur occasionally supernumerary elements of greater or less 

 frequency. Thus in Man, in which the subject has been nat- 

 urally investigated the most thoroughly, there have been re- 

 corded for the carpus fifteen or sixteen such elements, aside 

 from the occasional occurrence of the division of a normal 

 element into two (bipartite). The summary of such elements, 

 so far as known, resting upon the investigation of several 

 thousand' human carpi, is shown in Fig. 49. Similar super- 

 numerary elements occur in the tarsus ; the most important of 



ps 



FIG. 49. Diagrams of the supernumerary carpal bones. [After 

 PFITZNER.] 



r, radiale externum (constant in apes); ce, centrale; /, (epilunatum) ; z, hypo- 

 lunatum; c, triquetrum secundarium; p, epipyramis; y, praetrapezium; s, styloideum; 

 t, parastyloideum; e, metastyloideum; m, capitatum secondarium; g, ossiculum Gru- 

 beri; h, os hamuli proprius; v, os Vesalianum; ps, pisiforme secundarium. 



>f the normal carpal bones the scaphoides and the cuboides are represented as 

 bipartite. This peculiarity has been also observed in the lunare and the trapezoides. 



which are the trigonum, associated with the astragulus, and 

 present in 8% of the cases studied; the tibiale externum (n- 

 12%) ; the peroneum (8-9%) ; and an inter metatarseum (8- 



