252 MESSRS. MIVART AND MURIE ON THE [Feb. 28, 
serted into the sesamoid bone of the outer head of the gastrocne- 
mius. 
The flexor longus digitorum presents perhaps the most interest- 
ing peculiarities of any of the muscles of this animal. These pecu- 
liarities are passed over in silence by Professors Van der Kolk and 
Vrolik, which makes it the more probable that part of this muscle 
has been confounded by them with the gastrocnemius. 
The spontaneous flexion of the digits of this creature is very re- 
markable; and, as has been noticed by Professor Huxley’ in his 
account of the nearly allied form, Arctocebus, it requires considerable 
effort to extend the toes, which when left to themselves become 
again bent. 
We observed, in suspending the dead specimen by the feet from 
our fingers, that instead of falling to the ground, the body remained 
suspended, the toes forcibly contracting, grasping firmly the fingers, 
the animal thus hanging quite securely by the digits of its feet. 
Various modifications, doubtless, concur in producing this very 
strong and ready flexion of the digits ; but the peculiar origin of the 
flexor longus digitorum, there is little doubt, greatly contributes, if 
not mainly conduces, to this phenomenon. ‘This muscle has three 
distinct origins—the first from the internal condyle of the femur 
as high as the inner head of the gastrocnemius, and from the inner 
surface of the tendon of that inner head (fig. 5); the second part 
arises from the inner border of the tibia, in close union with the 
aponeurosis of the sartorius and semitendinosus. The fibres from 
these two origins unite to form one fleshy belly, which constitutes the 
greater part of the muscle. The third part arises from the posterior 
surface of the tibia, beginning above immediately below the popli- 
teus (fig. 5). Its fibres constitute the second belly of the muscle— 
an elongated rhomboidal mass which, uniting with the larger belly 
immediately above the common tendon, passes down behind the in- 
ternal malleolus, and, after giving off a small tendon to the hallux, 
bifurcates, the inner portion giving rise to two tendons, one going 
to the middie digit, the other forming part of the deep index-tendon. 
The outer portion also gives rise to two tendons, going to the fourth 
and fifth digits respectively (fig. 6, F. J. d). 
The origin of this muscle from the proximal bone of the limb (the 
femur) has the effect of flexing the digits by the mere extension of 
the leg on the thigh. Professor Huxley, in his present Hunterian 
Course of Lectures, dwelt upon the passive mode of suspension of 
Pteropus by its hinder extremities, and also noticed in the same the 
origin of the flexor longus digitorum from the femur. This similar 
condition must, doubtless, have a similar effect, and greatly contri- 
bute in Pteropus, as in Nycticebus, to the effortless suspension of the 
body. 
Meckel? describes the muscle under the name of the “ plantaire 
gréle,” and says it arises in the ordinary way from the internal con- 
dyle of the femur; but the plantaris, as far as we know, arises con- 
stantly and exclusively from the fibular side. This fact tells against 
? Proc. Zool. Soc. 1864, p. 319. — 2 Anat. Comp. vol. vi. p. 456. 
