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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![Owen describes the left rectus in Capromys fournieri as passing through a slit in the right, the right being therefore both super- ficial and deep to the left; this is practically what 1 found in Octodon, the only difference being that each rectus rose by two heads, the two belonging to the left muscle passing together between the two belonging to the right. In Myopotamus, according to Martin, the four heads alternate, one of the left being most super- ficial. The rectus in Aulacodus was not noticed. Mivart and Marie 1 describe a well-marked decussation in the Agouti; this 1 did not see ; indeed, in none of the animals examined was there any decussation approaching in distinctness that found in the Octodontkkc. Psoas Parvus.—The psoas parvus varies very much in develop- ment among the Hystricomorpha; it rises from the sides of the bodies of a variable number of lumbar vertebrae, and is inserted into the ilio-pectineal eminence on the brim of the pelvis. In the Dipodidse the muscle is large and rises from all the lumbar vertebrae except the last one or two (D. cegyptius, D. hirtipes). Among the Oetodontkke it is small and rises from the anterior 3 or 4 vertebrae, and from the crura of the diaphragm in Aulacodus, Myopotamus, and Capromys. In Octodon it was absent. In the Hystrieidae it has the same arrangement (Ilystrix, Sphingurus). In the C’hincbillidae the muscle is large, and rises from all or nearly all the lumbar vertebrae (Chinchilla, Lagostomus). In the Dasyproctidae it is small, and rises from two or three of the central lumbar vertebrae. In the Caviidae it is very small and apparently often absent. In one specimen of Ceredon it was absent, while in another it rose from the 4th and 5th vertebrae. In two specimens of Cavia cobaya it was present, in one it was absent. In the Sciuromorpha it is always present and well marked; it usually rises from the anterior four or five lumbar vertebrae. Psoas Magnus.—This muscle shows much less variation than that of the psoas parvus. It rises from the sides of the bodies and ventral surfaces of the transverse processes of all the lumbar vertebrae, and occasionally from the first sacral. The muscle is usually more or less distinctly divided into an inner and outer part by some of the branches of the lumbar plexus, this division being specially well seen in Spermophilus. It has the usual insertion as in Man. Iliacus.—The iliacus rises from the iliac surface of the ilium; it soon joins the psoas, with which it is inserted. Nothing charac- teristic was noticed about it in the different animals examined. Quadratus Lumborum.—This muscle rises from the sides of the bodies of the posterior dorsal vertebra, usually the last six, anti from the tips of the transverse processes of the lumbar vertebra ; it is inserted by a narrow tendon into the ventral surface of the 1 P. Z. S. 1866, p. 383. [31]](https://iiif.wellcomecollection.org/image/b2238635x_0035.jp2/full/800%2C/0/default.jpg)
