1866.] Mr. J. Wood on Variations in Human Myology. 237 



before found. It arises from the condyloid ridge of the humerus, below 

 the extensor carpi radialis longior {f), Kes between that muscle and the 

 extensor intermedins (c), which separates it from the extensor carpi radi- 

 alis hrevior (d). It has a distinct tendon of considerable size, which, 

 crossing that of the longior, goes through the sheath of the extensors of 

 the metacarpus and first phalanx of the thumb, and divides into two slips, 

 one to be implanted into the base of the frst metacarpal, and the other to 

 give part origin to a double abductor pollicis (b). The tendon of the 

 intermedins (c) can be seen to be implanted upon the second metacarpal 

 with that of the longior. In the left arm of the same subject only the 

 intermediate form was found. The close relation of these two forms is 

 well seen in the figure. The accessorius has an origin somewhat similar to 

 the intermedins, while its insertion and connexion with the short abductor 

 is precisely similar to that often found in the tendon of extensor ossis 

 metacarpi pollicis, with which the radial extensors have usually so close a 

 connexion at its origin, as before alluded to in describing the redundancy of 

 that muscle in subject 32 (fig. 6 c). If we suppose the germ of an extensor 

 intermedins to become blended with that of the upper and outer portion of a 

 double extensor ossis metacarpi pollicis, the result would be the extensor 

 accessoj'ius here described*. 



16. The extensor carpi uJnaris in two subjects sent, in both arms, ten- 

 dinous slips to the little finger, which were blended with the common 

 extensor aponeurosis (fig. 5 a). This variety is mentioned by Meckel. Henle 

 considers it as homologous with that of the peroneus quinti in the foot. 

 In both subjects the arrangement of the slip was strikingly similar 

 to that of the last-named abnormality, but in neither of them was the 

 peroneus quinti found in the foot. In the same arms the extensor minimi 

 digiti (b) was found provided with two tendons, both inserted, with a slip 

 from the common extensor, into the dorsal aponeurosis of the fifth digit (c). 



* On looking over Meckel's description of the exten&or ossis metacarpi pollicis, in 

 reference to this subject, the author finds that he mentions the rare occurrence of a 

 double-bellied long abductor of the tJiumb, arising from the outer condyle of the hume- 

 rus, and inserted into the base of the first phcdanx of the thumb {op. cit. Muskellehre, 

 p. 517). This has evidently been the extensor carjyi radicdis accessorius of the author, 

 passing entirely into the outer head of a double abductor j^ollicis brevis, without any 

 insertion into the metacarpal bone, as found in one of the specimens figured in the 

 author's first series. 



In many of the lower animals, and occasionally in the human subject (Henle), the 

 radial extensors are represented by one large muscle, which gives off two tendons to the 

 second and third metacarpal bones respectively. This original connexion seems to be 

 represented by the intermediate form of muscle just described. In the Anteater is found 

 a muscle arising from the himierus above the long supuiator, and inserted either into 

 the ensiform bone or into the muscular substance of the palm (Meckel, Anatomie 

 Compar., 1829-30, pp. 327-8, vol. vi.). In the Echidna and Oryiithorhyncus a small 

 muscle is found under the common extensor of the 2nd and 3rd metacarpal bones, which 

 ' is considered by Meckel {Be Ornithorhynco) to be a supinator longus. These may 

 probably be the homologues of this muscle. 



