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thin electrode against its lower wall. Energetic contractions will be produced in all the muscles that the nerve supplies. With less pain in thin persons it may be found immediately after it leaves the stylo-mastoid foramen. Press the rheophore strongly, just below the concha, between the mastoid and condyloid processes. The branches from the facial to the stylo-hyoid and digastric muscles may be excited in thin men by pressing the electrode deeply behind the condyloid process of the lower jaw. Their contraction is shown by movements of the os hyoides outwards, backwards, and upwards. In the parotid gland the single large branches of the facial are easily found, and produce contraction in definite groups of muscles corresponding to the ordinary divisions of the nerve; those branches which leave the parotid, and rest more or less closely on the bone, are easily excited, but not those that are imbedded in soft parts, especially the buccal branches. The frontal muscle may be thrown into contraction from beyond its own limits, since the branch of the facial by which it is supplied, before dividing for its final distribution, courses for some distance from the temple to the zygoma. The orbicularis palpebrarum may be excited either upon the zygoma or beyond it towards the parotid gland; close to the orbital margin the nerve commonly divides into a superior and inferior branch supplying the upper and lower halves of the muscle. Excitation of the trunk before it divides closes the eye firmly. In the neighborhood of the eye it is necessary to be very circumspect with the strength of the current (especially the voltaic). Duchenne quotes a case of blindness caused by too powerful an application of electricity, but weak faradization may be applied without injury even upon the conjunctiva, although the application is very painful, and causes profuse lachrymation and sometimes conjunctivitis. The nerve of the zygomaticus major may be excited quite close to the origin of the muscle at the inferior and external edge of the zygoma, and the certain bony support afforded for the pressure of the electrode makes its excitation unusually certain—more so than that of any other facial muscle. By its contraction the angle of the mouth and the contiguous portion of the upper lip are drawn upwards and outwards, and the skin of the cheek is thrown into deep folds.
The orbicularis oris : The twigs to this circular muscle enter it at four points, on each side of the face one for the upper and one for the lower lip, and to produce complete contraction, four electrodes would be required. The twigs must be isolated in close vicinity to the external border of the muscle.
The buccinator: Its nerves have a variable course, and are best sought at the inner margin of the masseter. The cheek becomes tightly contracted, and pressed upon the teeth. The masseter and temporal muscles, on account of the deep entrance of their motor nerves, can only be thrown into contraction by direct muscular excitation, since the belly of the muscle intervenes between the electrode and the entrance and course of the nerve. Of the nerves of the cavity of the mouth, those of the tongue are the most accessible. Excited on either side, the tongue becomes contracted and bowed towards that side. If when drawn upwards and backwards, its under surface is excited, it will be forcibly protruded. The velum can be only slightly distorted by lateral excitation, but its contraction and displacement backwards and upwards are easily produced by feeble currents.
The accessory nerve of Willis, external branch, may always be isolated with facility. After passing out behind the sterno-mastoid, and giving its branch to that muscle, its course is superficial to the trapezius. Above the origin of the branch to the sternomastoid, it may be reached without difficulty by pressing the electrode strongly into the middle of the belly of the upper half of that muscle; or if this does not succeed, by placing the electrode behind the belly of the muscle, and pressing it upwards and inwards. Simultaneous contraction of the sterno-mastoid and trapezius result; the cervical spine is bowed, the lower jaw pushed forwards, and the head rotated so as to turn the face away from the side that is irritated; the shoulder is strongly elevated and drawn backwards and inwards. The sternomastoid alone, may be thrown into strong contraction by its branch from the accessorius. Direct the electrode a little below the point for the main trunk of the nerve. Irritation of the accessorius close to the margin of the trapezius will throw this muscle into isolated contraction with either elevation of the shoulder backwards and upwards, with drawing up of scapula, or depression of head backwards and outwards, or both movements, according as the head or scapula is fixed by antagonist muscles. The hypoglossal nerve is accessible close above the great cornu of the hyoid bone in front of the hyoglossus muscle. The usual result is elevation of the whole tongue against the hard palate, with simultaneous action of the hyoglossus, and other muscles.
Rhythmical Electrization of the Phrenic Nerves, and
their accessories. The phrenic nerve may be discovered at the outer margin of the sternomastoid, in front of the scalenus anticus, and above the omohyoid. It must not be sought too deeply, but the electrode must be pressed inwards against the outer margin of the sternomastoid. If the point of the electrode be carried too high, it will encounter the fifth cervical nerve, which forms an acute angle with the phrenic. The electrode must not be carried above the middle of the sternomastoid, but kept near the omohyoid, the exact position of which is very easily found by faradization. The electrodes must be pressed in strongly, and in an oblique direction from without inwards. The proof that the phrenic is reached is afforded by rapid contraction of the diaphragm, arching forwards of the trunk, and forcible rushing of air through the glottis into the trachea, with a noise like the sobbing of a crying child. A powerful current is required, and its strength must be gradually increased until decided action of the diaphragm is obtained. The excitationi whether of one nerve or both, is unattended by danger, and generally produces no pain. In artificial respiration one electrode should be placed over the phrenic at the point where the omohyoid lies at the outer border of the sternomastoid, and the other upon the side of the thorax in the seventh intercostal space, and pressed in as deeply as possible towards the diaphragm. Faradization in this manner should be applied to the right and left sides alternately, and the circuit maintained unbroken for about the period of a deep inspiration. Or the two phrenics may be simultaneously excited. Take the disk rheophores (fig. 29), place them on both sides of the neck over the lower end of the scalenus anticus at the outer