44 
PRIMROSE ; THE ANATOMY OF THE ORANG OUTANG 
ligament, and from the tendon of the extensor ossis metacarpi pollicis, 
and was inserted into the radial border of the first metacarpal bone. 
Brooks^ also described the origin from the extensor ossis metacarpi 
pollicis. The opponens is well developed in apes and resembles in 
attachment and development the same muscle in the human hand. 
The Adductor obliquus pollicis arose from the bases of the second and 
third metacarpal bones and the ligaments over the anterior surface of the 
carpus. A portion of the adductor obliquus pollicis (indicated in plate 
V, fig. 5 a.obpl) exists as a separate slip passing over the anterior surface 
of the metacarpal bone. This apparently corresponds to the muscle and 
tendon fasciculus which Langer^ describes and figures, and which he 
believes to represent the flexor longus pollicis of man ; it is in conse- 
quence of the existence of this muscular slip that the Orang is capable 
of bending the terminal phalanx of the thumb. 
The Adductor transversus pollicis arose from the base of the third 
metacarpal bone and the distal extremity of the second metacarpal 
bone, and from the fascia over the interossei muscles between the two 
bony points named. The adductor muscles of the thumb in the Orang 
thus correspond very closely to the muscles of the same group in the 
human hand. 
The Flexor brevis pollicis. The inner head of the muscle (the “ inter- 
osseus primus volaris” of Henle, plate V, ^ fbp.2) arose from the base 
of the first metacarpal bone, and was inserted into the base of the first 
phalanx with the adductor obliquus pollicis. The outer head of the 
flexor brevis pollicis (plate V, fig. 5 fd.p. /), arose from the anterior 
annular ligament and was inserted into the radial portion of the base 
of the proximal phalanx. Flemming^ looked upon the flexor brevis 
pollicis as a single headed muscle. This view has been proved to be 
incorrect by Cunningham^ who holds that in the foot as in the hand the 
flexor brevis of the first digit is always a double headed muscle, and man 
is no exception to the rule. In man the ulnar head has suffered diminu- 
tion and has been suppressed by the great development of the adductor. 
The inner head is the muscle which Henle called the “ interosseus 
primus volaris.'’ It was Bischoff who first enunciated the view that such 
was the case in demonstrating the true significance of the interosseus 
1 Loc. cit., p. 82. 
2 Loc. cit., p. 183. 
3 W. Flemming-, “Ueber den Flexor brevis pollicis und hallucis des Menschen.” Anatomischer 
Anzeiger, 1887, pp. 68, 269. 
4 D. J. Cunningham, “The flexor brevis pollicis and the flexor brevis hallucis in man,’’ Anatom- 
ischer Anzeiger, 1892, p. 206. 
