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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![except in Ceredon, in which a small adductor secundi digiti was found, but no adductor minimi digiti. General Summary. The amount of facts at my disposal does not, of course, justify anything like an attempt at a definite and complete summary of the muscles of the llystricomorpha and Sciuromorpha. The following generalizations are merely suggested for future investigation. A. Differences between the llystricomorpha and Sciuromorpha. 1. In the llystricomorpha the anterior deep part of themasseter passes through the infraorbital foramen. In the Sciuromorpha it does not. 2. In the llystricomorpha, with the exception of the Dipodidae, the digastric has no complete division into two bellies, and the muscles of opposite sides do not communicate. In the Sciuro- morpha, as well as in the Dipodidae, a tendon completely divides the two bellies, and the muscles are connected across the middle line by a tendinous arcade. 3. The transverse mandibular muscle is absent in the llystrico- morpha, with the exception of the Dipodidae. It is present in the Sciuromorpha, with the exception of Castor. 4. The genio-hyoid muscles of opposite sides coalesce posteriorly in the Sciuromorpha, but not in the llystricomorpha. 5. The omo-hyoid is present or absent in the llystricomorpha. It is always present in the Sciuromorpha. 6. The levator claviculae rises either from the atlas or the basi- occipital in the llystricomorpha. Always from the atlas in the Sciuromorpha. 7. The scalenus anticus is present in the llystricomorpha, except in the Hystricidae. It is absent in the Sciuromorpha. 8. The trapezius is often divided into an anterior and posterior part in the llystricomorpha. Never in the Sciuromorpha. 9. The sterno-scapular muscle is composed of the subclavius and the scapulo-clavicularis in the llystricomorpha. In the Sciuro- morpha, as well as in the Dipodidae, only the subclavius is present. 10. The first part of the coraco-brachialis (rotator humeri) is always present in the Sciuromorpha. In the llystricomorpha it is present or absent. 11. The pronator quadratus is always attached to more than a third of the bones of the forearm in the llystricomorpha. In the Sciuromorpha it is attached to a third. 12. The supinator longus is present in all the Sciuromorpha except Castor. It is absent in the llystricomorpha except in JErethizon and the Dipodidae. 13. The scansorius is always wanting in the Sciuromorpha. It is often distinct in the llystricomorpha. 14. The quadratus femoris usually has a tendinous insertion in the llystricomorpha. It is fleshy in the Sciuromorpha. [44]](https://iiif.wellcomecollection.org/image/b2238635x_0048.jp2/full/800%2C/0/default.jpg)
