62 
PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
are muscle bellies for four toes, viz. : the first, second, third and fourth, 
whilst that for the fifth toe still retains its original position among the 
peronei. 
The Gastrocnemius. The outer head arose from the posterior aspect 
of the external condyle, and by a few fibres from the posterior ligament 
of the knee joint. The fibres of origin were closely associated with 
the flexor digitorum fibularis, the latter having a femoral origin behind 
the external condyle immediately internal to and above the place of 
attachment of the gastrocnemius. The inner head arose from the 
femur immediately above the internal condyle and from the posterior 
ligament of the knee joint. Langer and Tick both observed the 
connection of the outer head with the flexor digitorum fibularis. The 
muscle is not nearly so well developed as in man. 
The Soleus arose by a narrow attachment (i cm. wide) from the 
posterior part of the head of fibula ; this was joined by a delicate, thread- 
like, distinctly tendinous structure which descends from the outer and 
posterior surface of the tibia. MacalisteT found a trace of a tibial 
head in the Chimpanzee, but all other observers (Huxley, Pick, Langer, 
Bischoff, etc.,) state that the tibial head of the soleus is absent in all 
apes. The soleus and gastrocnemius unite in a tendo Achillis which 
is wholly tendinous at a point 3 cm. above the heel. In FickV Orang 
the fleshy fibres of the muscle extended down to its insertion into the 
os calcis, and this condition is held by him to be characteristic of 
anthropoids as compared with that found in the lower apes and in man. 
Bischoff agrees with this statement excepting in the case of the Gibbon, 
in which the tendo Achillis, according to him, is developed as in man. 
The Popliteus arose from the outer condyle of the femur within the 
knee joint passing through the posterior ligament of the knee. The 
muscle was overlaid at its origin by the outer head of the gastrocnemius 
and the femoral head of the flexor longus hallucis. It was crossed 
about its middle by the inner head of the gastrocnemius. Rudolf found 
on the right side that its nerve entered the superficial surface. It was 
inserted into the posterior surface of the tibia in its upper fifth and 
along the inner border of that bone extending down from the internal 
tibial condyle for one-fourth of the length of the bone. Langer and Pick 
both describe sesamoid bones in connection with the tendons of origin 
of the popliteus in the Orang. Humphrey^ looks upon the popliteus 
1 Loc. cit., p. 205. 
2 Loc. cit. I, p. 40. 
3 Loc. cit. I, p. 228. 
4 Loc. cit., p. 328. 
