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
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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![breaks up into branches (p. 47). When, however, as in the case ot the caudo-femoral, caudo-crural, &c., a part is segmented from the rest lor the purpose of independent action requiring indepen- dent nerve-supply, then, pai’tly for the better distribution of the nerves through its substance, the inscriptions disappear, the con- tinuity of the muscular fibres being established through them so as to cause their obliteration. It is probable also, taking into account the peculiar vibratory or successional manner of action of the several parts of a fibre by which sustained contraction is effected, that con- tinued action may have relation to continuity of independent fibres; whereas violent sudden efforts are associated with interruption of fibres, or, as in the case of the heart, with interlacing and intercom- munication of fibres, which would have much the same effect. Prac- tically, at any rate, we find where sustained action is required the muscular fibres ai'e parallel and uninterrupted, but where sudden violent efforts are needed the fibres are interlaced and communicating, or ai'e segmented by transverse tendinous inscriptions. It is obvious that just as the extension of the muscular fibres through or over the tendinous inscriptions would cause fusion or ankylosis of the myotomes, and the occurrence of this partially and in varied ways will lead to varied dispositions and divisions and complications of the muscular structure: so the extension of the tendinous inscriptions through or over the myotomes would cause fusion or ankylosis of the sclerotomes; and the ossification of the thus extended sclerotomes may lead to varied prolongations and com- plications of the bony skeleton. I have mentioned incidently that the limb-guxlles and the limbs are placed beneath the lateral septa in connection with the venti'al parts of the lateral muscles and have little or no relation to the dorsal parts, that the saiiie is the case with the ribs, and that the iliac bones are, like the ribs (]>p. 6 and 10), the result of ossifications in the ventral transverse intermuscular septa. It does not hence follow that the iliac bones are precisely the serial homologues of the vertebral ribs or ‘pdeurapophyses.’ An objection to that view is pi'esented by the fact that there intervenes in the Cryptobranch and other Urode- lans, between the iliac bones and the vertebral transverse processes on either side, a distinct bone which must correspond with a rib, and which in Menobranch has the elongated characters of a rib. This, together with the ventro-mesial position and relations of the pelvic bones and their freedom from the vertebral column in some animals (Whales, Snakes and Lepidosiren), indicate a serial correspondence with the skeletal formations in the sternal rather than with those in the vertebral (‘pleurapophysial’) region of the visceral wall. I avoid ap[)lying the term ‘hsemapophysial’ to the former because I think it by no means clear that the visceral cavity and its wall are to be regarded as identical with the hsemal canal and its wall. Indeed, as stated above, the lining of the visceral cavity {fascia tramversalis) in the Ci yptobranch is continued from the interior of the pelvis beneath the haemal arches of the tail where it blends with the subhaemal septum; and the position which a backward or caudal prolongation of](https://iiif.wellcomecollection.org/image/b21945810_0020.jp2/full/800%2C/0/default.jpg)
