1884.] MR. G. E. DOB«ON ON CAPROMYS MELANURUS. 241 



Supinator longns is absent, but s. brevis is moderately well 

 developed. 



Palmaris brevis is well developed, arising from the ulnar side of 

 the sesamoid ossicle covering the carpo-metacarpal articulation of 

 the pollex ; the fibres cross the })alm obliquely, superficial to the 

 tendons of the jiexor siiblimis, and end by forming the perforated 

 tendon for the fifth digit. 



Lumbricales are remarkably large ; they are four in number, and 

 arise close together (separated only by the tendons of the flexor 

 digitorum sublimis) from the palmar surface of the tendon of the 

 flexor profundus, immediately before it divides into slips for the five 

 digits, and from the fascial arches under which that tendon passes 

 into the hand. The first lumbricalis goes to the radial side of the 

 palmar surface of the second digit, and the other three are similarly 

 distributed to the third, fourth, and fifth digits respectively. 



Abductor minimi digiti arises from the pisiform bone, and forms 

 a slender tendon which is inserted into the ulnar side of the meta- 

 carpo-phalangeal sesamoid bone of the fifth digit. 



Flexor brevis minimi digiti arises, under cover of the preceding, 

 from the pisiform bone, and forms a tendon which unites with that 

 of the outermost of the pair oiflexores breves for the fifth digit, and 

 is, with it, inserted into the sesamoid bone. 



Although the pollex is very small, it is well supplied with 

 muscles ; there is & flexor brevis, an adductor, and a pair of flexores 

 breves. The flexor brevis arises from the sesamoid bone, covering 

 the polliceal carpo-metacarpal articulation, and forms a slender tendon 

 which is inserted into the radial side of the inferior surface of the 

 base of the terminal phalanx. The adductor poUicis arises from the 

 ligamentous structures at the base of the second metacarpal bone, and 

 is inserted into the first phalanx of the pollex ; and the pair of 

 flexores breves arise partly from the base of the first metacarpal and 

 partly from the sesamoid bone above-named. 



Adductor indicis and adductor minimi digiti are well developed ; 

 they arise togetlier from the ligamentous structures at the bases of 

 the third and fourth digits, and, continuing united for some distance, 

 diverge to their insertions into the bases of the first phalanges of 

 the second and fifth digits, respectively. 



Flexores breves. — There are a pair of these muscles for each digit, 

 arising as usual. (For insertions see interossei dorsales, below.) 



Extensor communis digitorum and extensor minimi digiti arise 

 together, as usual, from the external condyle ; and the extensor 

 secundi internodii pollicis et extensor indicis from the ulna and 

 interosseous membrane. The first-named divides into four tendons 

 for the four outer digits ; the second forms one for the fiftli digit 

 and another for the fourth, which unites with the dorsal interosseous 

 for that digit, and is, with it, inserted into the base of the dorsal 

 surface of the second phalanx of that digit ; the last-named, the 

 extensor secundi internodii pollicis et extensor indicis, divides into 

 two slips — one, very slender, goes to the terminal phalanx of the 

 pollex, the other to the corresponding phiilanx of the second digit. 



