PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
69 
arose from the annular ligament and was inserted into the under surface 
of the internal cuneiform. 
The Flexor brevis hallucis. The inner head arose from the portion of 
the tendon of the tibialis posticus which was inserted into the external 
cuneiform bone and from the sheath of the peroneus longus. It formed 
a well developed muscle 1.5 cm. wide, and was inserted into the base of 
the proximal phalanx of the great toe on its under and fibular side. 
The outer head (Interosseus primus volaris of Henle) was definitely 
demonstrated as a structure composed wholly of fleshy fibres .5 cm. 
wide arising from the base of the fibular portion of the first metatarsal 
bone and inserted into the outer aspect of the base of the proximal 
phalanx of the great toe, immediately under the insertion of the 
adductor obliquus. The outer head of the flexor brevis in anthropoids 
is weak and tends to unite with the adductor hallucis more or less inti- 
mately — thus Bischoff found it in the Gorilla. 
The Opponens hallucis was well developed. It arose in common with 
the flexor brevis hallucis, but proceeded separately to its insertion into 
the whole length of the tibial border of the first metatarsal bone. 
Rudolf observed on the right foot that the opponens could naturally be 
split up into three more or less separate and distinct fasciculi or 
bundles. The opponens hallucis is very variable in its development in 
apes. Bischoff states^ that he only found it as a separate muscle in 
the Orang among anthropoids and in Macacus among lower apes. 
Huxley^ discovered it in the Orang, and speaks of it as “ a most 
remarkable muscle.” At the time he writes (1864), he remarks that 
“this has not been described by other authors nor indeed is there any 
trustworthy evidence of the existence of such a muscle in any of the 
mammalia.” Macalister, however,^ subsequently found an opponens 
hallucis in the Gorilla although others have failed to find it in any of 
the anthropoid apes save the Orang. Brooks^ records that whilst it is 
absent in all anthropoids (with the exception of the Orang) some of the 
fibres of the adductor transversus (and sometimes also of the adductor 
obliquus) in anthropoids are inserted into the metatarsal bone of the 
hallux and constitute a “ second opponens ” corresponding to the 
“ adductor opponens ” described by Bischoff and Ganger in the hand of 
the Orang. (See page 46.) 
1 Loc. cit. 2, p. 235. 
2 Loc. cit., Vol. I, p. 596. 
3 Loc. cit., p. 506. 
4 Loc. cit., p. qo. 
