On the myology of the sciuromorphine and hystricomorphine rodents / by F.G. Parsons.

  • Parsons, Frederick Gymer, 1863-1943.
Date:
1894
Catalogue details

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.

    42/48 (page 290)
    the extensor longus on the dorsum of the toes. It is present in all the Sciuromorpha and Hvstricomorpha except Dipus. In no case was it seen to give a tendon to the hallux, but tendons to the second and third toes were always met with. In Ccelogenys, Arcto- mys, and Erethizon dorsatus1 it sends a small slip to the fourth toe, but it does not follow that when the four outer toes are well de- veloped a tendon goes to each ; for in Octodon, in which all the five toes are present, the muscle only sends slips to the second and third. Peroneus Longus.— The peroneus longus showed very little vari- ation in the Rodents examined. It rises from the head and the upper part of the outer surface of the shaft of the fibula, also in many cases by a few fibres from the external lateral ligament of the knee. Its tendon passes through a groove on the outer side of the extei’nal malleolus, grooves the cuboid, and is inserted into the base of the first metatarsal bone, or, when that is absent, into the second. In one specimen of Hystrix I failed to find it, but it was present in another which 1 looked at. Peroneus Brevis.—The peroneus brevis rises either from the upper or middle portions of the outer surface of the fibula. Its exact origin is very variable and is not constant for animals of the same group. It passes behind the external malleolus and is inserted into the base of the fifth metatarsal bone. In Dipus cegyptius it is absent. In the Octodontidse, Hystricidse, and Chinchillidse it is present. In the Dasyproctidse it is absent in Dasyprocta, but present in Coelogenys. In the Caviidse it is present in Cavici cobaya and Cere don, but absent in Dolichotis 1 2. In the two former it is inserted into a nodule of bone (rudimentary fifth metatarsal ?) under the base of the fourth metatarsal. In one specimen of Guinea-pig I found it dividing into two parts ; the anterior, which was the smaller, had the usual insertion, while the posterior was attached to the anterior and upper part of the external surface of the calcaneum. Beddard describes a somewhat similar arrangement in the peroneus quarti digiti of Dolichotis2. The muscle is present and normal in all the Sciuromorpha. Peroneus Quarti Digiti.—This muscle arises from the lower part of the outer surface of the fibula below the origin of the peroneus quinti, when that muscle is present. When the p. quinti is absent the p. quarti rises from the upper part of the outer surface of the fibula. The insertion is into the extensor tendon on the dorsum of the fourth toe. In Dipus cegyptius it is present and rises from just below th$e p. longus. In the Octodontidse it rises from the lower part of the fibula (Octodon, Myopotamus, Capromys, Aidacodm). In the Hystricidse it is present in Hystrix, bul absent in Sphin- [40] 1 P. Z. S. 1882, p. 271. 2 P. Z. 8. 1891, p. 23G.