PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
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and the flexor digitorum tibialis, both became tendinous immediately 
above the inner ankle, and proceeded towards the sole of the foot. They 
passed behind the inner ankle, where they lay in separate osteo-fibrous 
canals, separated from one another by a well-defined fibrous partition, 
the nerves and vessels which pass into the sole lying on a more superficial 
plane immediately over the fibrous septum between the muscles. The 
flexor digitorum fibularis was confined in a groove in the posterior part of 
the astragalus and passed immediately subjacent to and in contact with 
the sustentaculum tali of the os calcis, the flexor digitorum tibialis 
occupying a position anterior to this. In the sole of the foot the two 
muscles crossed one another, the tendon of the flexor longus tibialis 
occupying the more superficial position. From the flexor longus tibialis 
a considerable contribution was given to the flexor brevis digitorum 
to be presently described, and from the same source the deep flexor 
tendons were supplied for the second and fifth toes, whilst the deep flexor 
tendons for the third and fourth digits passed from the flexor digitorum 
fibularis. Four lumbricales existed in connection with these deep 
flexors. The first lumbrical was attached solely to the tibial side of the 
tendon of the flexor digitorum tibialis for the second toe. The second 
and third lumbricals were connected with the tibial side of the tendon of 
the flexor digitorum fibularis for the third aud fourth toes. The fourth 
lumbrical arose by two heads, one from the tibial side of the flexor digi- 
torum tibialis of the fifth toe, and the other head from the fibular side 
of the tendon of the flexor digitorum fibularis of the fourth toe. 
The Flexor brevis digitorum was closely associated in the sole with 
the tibial and fibular flexors. It was a well-developed muscle, and 
arose from the inferior and inner aspects of the os calcis by an ori- 
gin 2 cm. wide. It was inserted into the four outer toes. The ten- 
don for the third toe was the strongest, and received the bulk of the 
fleshy fibres of the muscle. This tendon split into two portions, which 
passed to be inserted into the ventral aspect of the middle phalanx at 
its base, allowing the tendon of the flexor digitorum fibularis to perfor- 
ate and pass beneath in the usual fashion. The division to the second 
toe was similar in its relations, but was not as strongly developed. The 
division for the fourth toe was very delicate, its tendon being very fine 
and thread-like. This delicate tendon was joined by a well-developed 
tendon, which was derived from a bundle of fleshy fibres in the sole, 
having their origin from the flexor digitorum tibialis opposite the inner 
ankle. The tendon for the fourth toe, being so constituted by fibres 
derived from the two muscles named, passed on and split to allow the 
perforating tendon (flexor digitorum fibularis) to pass beneath, and had 
