The muscles of the fore and hind limbs in Dasypus sexcinctus / by John Charles Galton.

  • Galton, John Charles.
Date:
[1868]
Catalogue details

Licence: Public Domain Mark

Credit: The muscles of the fore and hind limbs in Dasypus sexcinctus / by John Charles Galton. 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 radius, at the junction of the proximal with the middle third of this bone, and immediately posterior and external to the insertion of the broad tendon of the pronator teres, widening out and becoming flatter at its termination. This muscle is not represented by Cuvier in his plates of the myology of Dasypus. Both short and long supinatores appear, according to Meckel, to be fused together (“ verschmolzen zu seyn”). He remarks further that no muscle is given off from the humerus above the extensores of the hand. Tinder these, on the other hand, lies a much stronger muscle, which passes to the upper half of the radius, “und bloss Beuger ist.” In all probability the long supinator is absent in this animal {Dasypus); and the above muscle may be, after all (“nur”), the short supinator^. Mr. Mivart and Dr. Murie, in their paper on the “Myology of Hyrax capensis”^, describe as supinator longus a muscle which much resembles that which I have termed s. hrevis in Dasypus. It is ^‘exceedingly diminutive, and arises from the outer shaft of the humerus, just above the common origin of the next two muscles {extensor carpi radialis and e. communis), and is inserted into the radius near its neck.” Soemmering^ in his description of this muscle in man, says, “ Nonnumquam superior pars [humeral origin] a reliquo musculo distincta est.” Theile, moreover, states that when the two layers of which the muscle is composed are distinct, the superior head takes origin from the outer condyle of the humerus^. Extensor carpi radialis.—Brom the strong outer ridge (“supinator ridge”) of the humerus arises, for the extent of nearly three quarters of an inch along its superior portion, a muscle which, after completing about half of its course, crosses over the radius, and, becoming suddenly tendinous at the distance of an inch from its insertion, passes under a ligamentous and muscular bridge into the palm. The ligamentous bridge stretches from the abrupt spinous termination of the dorsal ridge of the radius to a sesamoid lying midway between this point and the styloid process of the bone. The extensor ossis metacarpi pollicis forms the muscular bridge. Two cord-like tendons are given off simultaneously by this muscle, which, before becoming tendinous, narrows more or less suddenly to a conical apex; one of these is inserted into the dorsal surface of the metacarpal of the index, while the other termi- nates at the same aspect of the like segment of the middle digit. These answer respectively to the tendons of the extensores carpi radiates, longior et hrevior, of human-anatomy language. It is stated in Cuvier’s ‘ Le5ons that in some animals, such as the Dog, Hyaena, Hare, and the Edentata, the above muscles are fused together at their condyloid ex- tremity, their tendons alone being distinct. Meckel observes that the extensor radialis hrevior is occasionally absent in man, as is the case in many mammals, in which never more than one radial extensor is met with. “ Conformation,” he continues, “ dont le premier degrd est la fusion complete des deux radiaux externes en un seul, dont on connait divers exemples ” ®. ^ Proc. Zool. Soc. April 1865, p. 340. ‘‘ Encyclopedie Anatoraique, tom. iii. (Paris, 1843) p. 231. ® Manuel d’Anatomie Generale, tom. ii. p. 163. 4 F 2 * Op. dt. p. 534. ■’ De Corp. Human! Fabr. tom. iii. p. 267. ® Loc. dt. p. 443.