On the structure of the membrana tympani of the human ear / by Joseph Toynbee.

  • Joseph Toynbee
Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: On the structure of the membrana tympani of the human ear / by Joseph Toynbee. 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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    In the Croonian Lecture, published in the nineteenth volume of the Philosophical Transactions, Sir Everard Home advanced the opinion that the membrana tympani in the human subject was muscular. His words are, “ When viewed in a microscope magnifying twenty-three times, the muscular fibres are beautifully conspicuous, and appear uniformly the same throughout the whole surface. There being no central tendon as in the diaphragm, the muscular fibres appear only to form the internal layer of the membrane, and are most distinctly seen when viewed on that side*.” The use of this radiated muscle, Sir Everard Home states, is “ to give those different degrees of tension to the membrane, which empower it to correspond with the variety of external tremors-j~.” Since the first publication of this opinion as to the muscularity of the membrana tympani, anatomists have generally conceded that it is fibrous, but they have widely differed as to its composition. According to Mr. Quain and Dr. Sharpey, “ it is made up of fine closely arranged fibres, the greater number of which radiate from near the centre to the circumference; but within these are circular fibres which are more scattered and indistinct, except close to the margin of the membrane, where they form a dense, almost cartilaginous ring^.” Mr. Wharton Jones writes, “The proper membrane can be divided into two layers, an outer thin one, consisting of radiating fibres, and an inner thicker layer, which is less distinctly fibrous, though when torn it does indicate a fibrous disposition, and that in a direction opposite to the former The fibres which cross the radiating ones are also more aggregated at the centre. They run parallel with the handle of the malleus and turn round its extremity. At the circumference of the proper membrane there is a thick firm liga- mentous or cartilaginous ring, which is fixed in the groove of the bone. The liga- mentous ring appears to be formed by an aggregation of the circular fibres interwoven with the peripheral extremities of the radiating ones§.” By careful dissection the fibrous layers of the membrana tympani may be separated into two distinct laminae, the fibres of which have no communication with each other. The external layer may be called the radiate fibrous lamina, on account of its fibres radiating from the malleus to be attached to the cartilaginous ring, and the internal the circular fibrous lamina. The radiate layer is the thicker and stronger. So readily may the two layers be separated from each other, that they are detached with greater facility than that with which the circular layer can be removed from the mucous membrane. a. The Radiate Fibrous Lamina. If the whole of the membrana tympani be carefully removed, there will be observed at its circumference a white dense ring, apparently cartilaginous, which is received into the osseous groove of the temporal bone appropriated to it. It will be remem- bered however that this groove occupies only about five-sixths of the circumference of the inner extremity of the meatus, the upper sixth being smooth instead of grooved. * Loc. cit., p. 5. f P. 11. + Elements of Anatomy, fifth edition, 1848, vol. ii. p. 932. § Cyclopaedia of Anatomy and Physiology, vol. ii. p. 545.
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