The auditory ossicles of American rodents / by T.D.A. Cockerell, Lewis I. Miller and Morris Printz.

  • Theodore Dru Alison Cockerell
Date:
1914
Catalogue details

Licence: In copyright

Credit: The auditory ossicles of American rodents / by T.D.A. Cockerell, Lewis I. Miller and Morris Printz. 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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    Muring. Epimys norvegicus (Erxleben). Boulder, Colorado (Printz and Miller); Bloomington, Indiana (Max M. Ellis). Malleus. Lamina well developed, with sub triangular outline; processus gracilis thin; cephalic peduncle scarcely curved, gradually passing into the head, which has a short articular surface as in Neotomime (thus quite different from Arvicolidffi); arti- cular surface deep, its margins presenting two conspicuous projections; cephalic process heavy, gradually tapering, its base much broader than in Neotoma; orbicular apophysis well developed, but much smaller in proportion to the rest of the ossicle than that of Mus. Manubrium bimarginate, its distal end flattened, spatulate, heel or processus brevis distinct. The processus muscularis exists as a tubercle near the upper side of the base of the orbicular apophysis, evidently corresponding to a simi- larly placed tubercle in Neotoma. Incus. Heavy and compact, with the stapedial process very stout, with a narrow curved concavity running down its inner surface; articulating surface double, very broad; processus brevis short, pointed. Sylvian apophysis developed. Stapes. Strongly asymmetrical, one crus being much shorter and straighter than the other; stapedial process small but distinct, at the junction of the head with the crus; foot-plate flat. No intercrural bony canal was found, but a blood-vessel passes between the crura. Mus musculus L. Boulder, Colorado. Malleus. Readily distinguished from that of Epimys norvegicus; lamina with a subquadrate outline; processus gracilis quite heavy; cephalic peduncle with an angular bend (compare Neotoma orolestes); articular surface low and rather wide; orbicular apophysis large and prominent; processus brevis distinct; manubrium bimarginate, the inner margin very thin. Incus. Difficult to separate from the malleus. Processus brevis prominent, and much thicker than the stapedial process, which it nearly equals in length. Sylvian apophysis present. Stapes. Even more asymmetrical than that of Epimys] one crus practically straight, the other strongly arched; stapedial process obtuse but distinct; head large, foot-plate distinctly convex. A blood vessel, but no bony canal, passes between the crura. Doran figures and describes the ossicles of the Australian Conilurus mitchelli, and it is evident that they differ only a little from those of Epimys. The incus has the same very thick stapedial process; the stapes seems to be more symmetrical; the orbicular apophysis is less robust. Doran says that the manubrium is rather shorter than in Mus, but his figure represents it as longer.