STRUTHIONES 501 



The extensor metacarpi radialis is single. 

 The ectepicondylo-ulnaris is absent or fused with the 

 extensor metacarpi ulnaris. 



The extensor digitorum communis suppHes only the 

 index. 



The two pronators form only one muscle. 



The flexor digitorum sublimis and the fl. dig. profundus 

 arise by a single head from the flexor condyle of the humerus. 

 The two muscles immediately divide ; the upper part (= 

 sublimis) ends in two tendons, of which one is inserted on to 

 radiale, the other fuses with the upper tendon of profundus, 

 and also gives off two shps which surround that tendon and, 

 reuniting, fuse with the lower tendon of the profundus. The 

 lower part of the muscle (= profundus) gives off two ten- 

 dons, of which the upper ends on the first metacarpal, while 

 the lower runs to the base of the last phalanx of the 

 index. 



The flexor metacarpi ulnaris ends fleshily on ulnare, but 

 is prolonged beyond this bone, receiving also some fibres 

 from it, to the metacarpal. 



The radio-metacarpalis ventralis — or at least a muscle 

 which, if it be not this, is not found in Palamedea — arises 

 from the ulna and not from the radius. 



The total number of muscles in the hand of the ostrich 

 is twenty-three, allowing for the absent ectepicondylo-ulnaris. 

 The additional muscle is a small pronator quadratus, running 

 from the ulna to the radius. 



It appears, therefore, that, in spite of the small size of the 

 manus of the ostrich relatively to that of flying birds, there 

 is but little if any evidence of degeneration in its musculature. 

 On the contrary, indeed, for it might be said that the wing 

 muscles of Struthio are less degenerate, or at any rate less 

 modified, than those of carinates in that amount of muscle 

 as compared with tendon is greater. The complication of 

 the conjoined flexores digitorum is highly suggestive of a 

 walking or climbing animal. It seems to be conceivable 

 that the ostrich branched off from the avian stem before the 

 power of flight was perfectly established. 



