Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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current is opened, the contraction of the iris as instantly ceases. If the small sponge tipped ivory electrodes are now applied to the opposite edges of the cornea of one eye, or a little farther hack on the sclerotica of the eye, then the radiar fibres of the iris are extended, as is an extensor muscle, and thus the pupil is enlarged. If these little electrodes are applied to the right and left of the eyeball, the pupil then assumes the form of an egg standing upon end; if the electrodes touch the eyeball above and below, then the oval pupil is horizontal. Thus we can act on the iris of the eye by the electric current so as to contract or dilate the pupil according as we direct the electrodes to the sphincter pupillw, or to the dilator pupillm. The pupil of the eye in man can thus be constricted simply by means of a single voltaic pair, as by my local silver battery, if the one metal is placed in the nostril, while the other is upon the tongue; and then — the patient sitting in the mildest light of the room, where there is only just light enough to see the oscillations of the pupil, — upon making and breaking contact between the two metals by the clasp of the insulated conductor, the pupil is seen to dilate and contract; or, rather, to contract with the contact, and to dilate with the breaking of the circuit. l.i The External Opening into the Ear at the bottom of the Concha. 2. The Meatus Auditorius Externus, or car- tilaginous canal. 3. The Membrana Tympani, stretched upon its ring. 4. The Malleus. 5. The Stapes. 6. The Labyrinth, where is also the loop fringe of the Auditory Nerve. Fig. 57. An Anterior View of the Left Ear, showing the External Ear, the Meatus Auditorius, the Labyrinth, &c. 20'