On the myology of the sciuromorphine and hystricomorphine rodents / by F.G. Parsons.
- Frederick Gymer Parsons
- Date:
- 1894
Licence: Public Domain Mark
Credit: On the myology of the sciuromorphine and hystricomorphine rodents / by F.G. Parsons. 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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![of the head of the fibula and in most cases joins the outer head of the gastrocnemius to help form the tendo Achillis. In Ccelogenys and Cavia cobay a, however, the muscle continued separate to its insertion in the tuber calcis, while in Ceredon it was inserted into the os calcis by a round tendon from its inner portion, while the outer portion blended with the tendo Achillis. Plantaris.—The plantaris rises just above the outer head of the gastrocnemius ; it forms a muscular belly as large as, or larger than, either one of the gastrocnemius. It soon contracts into a narrow tendon, which winds round the inner side of the tendo Achillis, and passes over the back of the tuber calcis to the sole, where it spreads out into a broad fascia, which eventually splits into slips for the four outer toes or as many as are present. Each of these slips acts as a flexor perforatus, allowing the long flexor tendons to pass through, and is then inserted in the same way as the flexor sublimis in the fore limb. In Castor, where the muscle is perhaps better developed than in any other Eodent, the tendon divides into a superficial and a deep layer w'hen it reaches the commencement of the sole. The superficial layer is fibrous and corresponds to the plantar fascia; the deep layer develops muscular fibres and doubtless represents the flexor brevis digitorum of human anatomy. In many cases a loop is given off from the deep surface of each tendon before it is perforated; this loop embraces the long flexor tendon as in the anterior extremity. Popliteus.—The popliteus always has the usual human attach- ments, except that it is often inserted only into the inner border of the upper third of the tibia instead of into the posterior surface right across. Flexor Longus Hallucis (Flexor Fibularis).—The long flexors of Rodents have been so thoroughly described by Dobson1 that it would be waste of space to do more than refer the reader to his Monograph. I have repeated his dissections in many animals and can confirm the accuracy of his descriptions. The additional animals that I have dissected fully bear out his point that among the Hystricomorpha the flexor fibularis is joined in the sole by the flexor tibialis and is inserted into the terminal phalanges of all the toes. In the Sciuromorpha, on the other hand, the flexor fibularis goes to all the toes without being joined by the flexor tibialis in the sole. In Aulacodus and Dasyprocta no fibres were continued to the inner- most toe from the flexor fibularis. Flexor Longus Digitorum (Flexor Tibialis).—This muscle, as Dobson1 points out, rises from the back of the tibia and iiuthe Hystricomorpha joins the flexor fibularis in the sole, its fibres being continued chiefly to the inner toes. In the Sciuromorpha it does not join the flexor fibularis, but in Sciurus, Xems, Spermo- philus, aud Arctomys is inserted into a sesamoid hone below the internal cuneiform, from which some ill-marked fibrous tissue is continued on to the hallux. In Castor it terminated in the inner half of the double scaphoid. The only exception to this arrange- 1 Journ. Anat. vol. xviii. p. 159. [42].](https://iiif.wellcomecollection.org/image/b2238635x_0046.jp2/full/800%2C/0/default.jpg)
