Observations on the anatomy of Nycticebus tardigradus / by St. George Mivart and James Murie.

  • Mivart, St. George Jackson, 1827-1900.
Date:
[1865]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the anatomy of Nycticebus tardigradus / by St. George Mivart and James Murie. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    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 Huxley1 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 semitendiuosus. 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 middle 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. 1. 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 ot the body. Meckel'2 describes the muscle under the name of the “plantaire grele,” 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 flbular side. This fact tells against 1 Proc. Zool. Soc. 1861, p. 319. 5 Anat. Comp. vol. vi. p. 456. [14]