The surgical diseases of the ear / by Prof. von Troltsch. The mechanism of the ossicles and the membrana tympani / by Prof. Helmholtz ; translated from the German by James Hinton.

  • Tröltsch, Anton Friedrich, Freiherr von, 1829-1890.
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: The surgical diseases of the ear / by Prof. von Troltsch. The mechanism of the ossicles and the membrana tympani / by Prof. Helmholtz ; translated from the German by James Hinton. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    13» strong vibration, which betrays itself by a tickling, buzzing sensa- tion in the depth of the ear. The apparatus of which fig. lo (see p. 147) is a sketch is very suited to the production of such tones. I may here mention, also, that in order to put the completeness and accuracy of this explanation of the mechanical construction of the ear to the test, I have constructed a model of the tympanic apparatus on a large scale. The ossicles are made of wood, the membrane cut out of glove leather, so that a seam fastened to the malleus holds it along the malleus-handle; by this means its con- cave conical form cau be given. An opening of suitable form, cut in a small board with oblique edges, on to vi^hich the edge of the artificial membrane is glued, represents the inner end of the meatus. Externally a cylinder of tin is fastened to the board, encircling this opening, and over it is fixed a cover of tin with a caoutchouc border, as is now done to keep preserved fruits air-tight. If we apply this cover so that a movable portion of the caoutchouc border remains between it and the ring of tin, it is possible to compress the air on the outer side of this artificial membrane, and allow it to act on the ossicles. Inside, near the anterior superior border of the opening, is fixed a strip of wood with a projecting point to represent the spina tympanica major. The axis-band is represented by a hempen thread, which starts from this point and passes through and round the malleus, and then proceeds to the posterior superior edge of the opening, pierces the board, and is made fast by an iron screw, which regulates its tension. Other suitably fixed threads, with their screws, represent the strands of the ligamentum externum, and those strands of the ligamentum anterius mallei that run upwards from the spina, finally, a thread of silk that passes through an iron ring, fastened to a small pillar of wood, and then is fastened to a stretched elastic band, represents the tensor tympani. My method of forming the articular surfaces of the malleus and- incus was as follows : first, I spread warm sealing wax over the surface of the malleus, and attempted to give it, while soft, the required form as well as I could. Then the articular surface of the incus was also covered with hot sealing-wax and pressed upon the articular surface of the malleus, which had been covered with tinfoil. The- tinfoil attached itself to the incus. Then, before the sealing-wax was quite cool, I made such rotating movements with the incus, as occur in the natural connection of the bones, in order to give the