PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
57 
the leg extending downwards from the level of the knee joint; the fascia 
over the muscles of the leg being here very strongly developed. 
Fick^ describes the ischio-femoral portion of the biceps as the direct 
antagonist of the scansorius, the action of the former muscle being to 
extend the hip and to rotate it outwards ; both these muscles are absent 
in man. Langer^ describes the long head of the biceps as in part going 
to be inserted into the patella, and he characterizes it as the great 
“ sprungmuskel ” which, in quadrupeds, is capable of extending all three 
joints, hip, knee and ankle. In Langer’s Orang connection with the 
tendo Achillis alone was absent. The ischio-femoralis is sometimes 
joined with the gluteus maximus in the Orang, but more frequently is 
completely separate. In the Gorilla, Bischoff® describes the two heads 
of the biceps, but states that the long head is not inserted into the linea 
aspera as in the Orang, but passes to the head of the fibula and the 
fascia cruris. In the Chimpanzee and the Gibbon, according to the 
same authority, the Biceps is most human-like but extends also into the 
fascia cruris. In the lower apes the biceps has only one head — the long 
head — which is inserted, not into the fibula,but into the tibia ; this fact is 
noted by Bischoff and by Huxley.^ Hepburn found both heads 
present in the Orang, and, whilst one was inserted into the fibula and the 
other into the tibia, there was no femoral attachment. The biceps has 
been found in rare cases inserted in part into the tendo Achillis in man 
(Testut). 
The Seinimembranosus arose external to the point of attachment of 
the semitendinosus from the posterior part of the tuberosity of the 
ischium and the bone immediately in front of this (0.75 cm. wide) ; it 
was inserted into the inner aspect of the head of the tibia. 
The absence of a ligamentum teres in the hip joint was noted. No 
vestige of this structure could be found ; the head of the femur present- 
ing an unbroken surface smooth throughout. One could not determine 
any definite ilio-femoral ligament, although the capsule of the hip-joint 
was thickened anteriorly in the line of its usual development. 
The shortness of the hamstring muscles in the Orang and their low 
attachment, removed some distance below the knee, prevent complete 
extension of the leg at that joint, and this inability to extend at the 
knee is necessarily still further increased when the hip-joint is flexed. 
1 Loc. cit. I, p. 3Q. 
2 Loc. cit., p. 187. 
3 Loc. cit. 2, p. 21. 
4 Loc. cit. Vol. II, p. 40. 
