236 Mr. J. Wood on Variations in Human Myology. [June 21, 



have, therefore, a flexor for each of the metacarpal bones, reckoning the 

 opponens as one. But further than this, the outer fibres of the extensor 

 ossis metacarpi pollicis in the same arm (see fig. 6 c) are separated from 

 the rest by a cellular interval, and arise partly from the fascia covering the 

 radial extensors and supinator longus. They are connected with a distinct 

 tendon, which is implanted into the front part of the outer border of the 

 base of the first metacarpal bone. Traction upon this tendon showed that 

 its action was rather of the nature of flexion with abduction than of exten- 

 sion. This peculiarity of origin is noticed by Henle (Muskellehre). The 

 arm from which figs. 3 and 6 were taken is now in the custody of the 

 Curator of the Hunterian Museum. In fig. 3 is seen also the abnormal 

 insertion of the third lumbricalis (c), the absence of the fourth, and at h 

 the frst palmar interosseus of the thumb, described by Henle. In fig. 6 

 the additional special extensors of the third and fourth fingers are given. 



In subjects 13 and 31 were found muscles which are entirely homologous 

 with the flexor carpi radialis brevis just described. They had exactly 

 similar origins, were of the same shape and with like tendons, but were 

 inserted into the inner side of the base of the second instead of the third 

 metacarpal bones, one of them passing, with the tendon of the flexor carpi 

 radialis, through the groove in the trapezium and annular ligament, but 

 the other going outside of that sheath. 



In subject 6 was found a large fusiform muscle, having its origin from 

 the radius outside of that of the flexor longus pollicis, and reaching as high 

 up as the oblique line below the flexor sublimis. Ending in a distinct, 

 strong, and rounded tendon, it was implanted into that deeper portion of 

 the annular ligament which separates the groove for the flexor carpi radi- 

 alis tendon, and with this into the trapezoid, magnum, and base of the 

 middle metacarpal bones. A muscle precisely similar to this was described 

 by the author in his last paper (subject 1). Its resemblance in appearance, 

 position, connexions, and influence upon the carpus, have induced him to 

 class it with the foregoing flexor carpi radialis brevis as a variation of the 

 same type of muscle, the flexor of the middle metacarpal bone. 



15. The variations of the radial extensors found in this column are of two 

 kinds, which appear to be closely allied. The first kind mentioned are the 

 interchanging muscles frequently seen and recorded by anatomists. These, 

 arising with one of the twin muscles, pass as distinct tendons over to 

 the other, and become inserted with it. Of these, three were found. In 

 the absence of a name the author has ventured to distinguish this form of 

 muscle by that of the extensor carpi radialis intermedins. Of the other 

 kind is found only one example. It is the extensor carpi radialis acces- 

 sorius first recorded, named and described by the author in his former 

 papers*. It has been chosen as the subject of fig. 4, taken from the right 

 arm of subject No. 23, because of its coexistence with the intermediate form 

 of the radial extensors, which was not the case in any of the specimens 



* This muscle seems to be present in about the proportion of 1 in 35 subjects. 



