Observations in myology : including the myology of Cryptobranch, Lepidosiren, dog-fish, Ceratodus and Pseudopus pallasii, with the nerves of Cryptobranch and Lepidosiren and the disposition of muscles in vertebrate animals / by G.M. Humphry.

Date:
1872
Catalogue details

Licence: Public Domain Mark

Credit: Observations in myology : including the myology of Cryptobranch, Lepidosiren, dog-fish, Ceratodus and Pseudopus pallasii, with the nerves of Cryptobranch and Lepidosiren and the disposition of muscles in vertebrate animals / by G.M. Humphry. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    *■ mass of the sole, and so on to the extremities of the digits. It may be called ‘ caudo-pedalis,’ and it constitutes a continuous muscle reaching from the middle of the tail to the ends of the toes. Its fibres are partially interrupted by a tendinous in- scription, and it is joined beyond that point by a portion of the muscle arising from the ischium in which there is no tendinous inscription. (Fig. 10.) The third division—‘ caudo-femoralis’—arising somewhat more laterally and deeply from the haemal arches, is inserted by a strong tendon into the middle of the under (plantar) surface of the femur. This disposition of the caudal muscles corresponds with that in the other Urodelans* (Axolotl, Menobranch and Newt) which I have examined; the only difference being, that in these the upper and larger—the iliac—portion of the ventral muscle does not afford so thick a covering stratum to the ilium, and consequently that bone, occupy- ing as it does in Cryptobranch the plane of one of the intermuscular septa, approaches nearer to the surface. Internally the ilium is, as in Ciyptobranch, lined by a deep stratum of the caudal muscle which is continued into the abdomen. The TKANSVBRSE INSCRIPTIONS Or ‘sclerotomcs’ which, in these animals, as in the fish, divide the lateral muscles into so many ‘myotomes,’ serve the purpose of binding the muscles throughout their whole length and depth to the vertebral column, preventing their starting from the column towards the arc of the curve, or their having a tendency to do so, when the tail is bent to one side or the other under their contraction; also by ]>reventing the continuity of the muscular fibres, and by diffusing among many the force of the pull consequent on the contraction of any one, they add greatly to the strength of the whole. It is obvious that if each muscular fibre had been continued from end to end of the animal, and, further, had been required, as must be the case in these animals, and in fishes especially, to contract in its whole length simultaneously for the purpose of effecting those energetic violent flexures which produce the dart- ings and leapings of these animals, it would have been liable to rupture under its own force. The interruption however of the fibre by an inscription common to it with others diffuses the pull of the several parts of each fibre among many, and enables them all better to combine in a simultaneous effort. The arrangement does not interfere with the nerve-supply because each myotome receives its own nerves from its own division of the spinal cord through its vertebral foramen, in addition to the filaments from the lateral nerve which travels along the lateral septum to the tail and then ^ It corresponds also generally with, the account given by Mr Mivart of the Menopoma and Menobranch, Proc. Zool. Soc. April 22 and June 24, 1869.