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cylinder, and the reader in ordering would do well to give the dimensions, about 1: by 1$ inches, and to see that the handles are hollowed out as in the figure. It is astonishing how difficult it is to get
an instrument maker to do this, and to have it properly done makes a material difference in the ease with which they can be used, lying comfortably between the fingers, as in fig. 30, which shows the most convenient method of holding two rheophores in the same hand. Fig. 29 is a disk rheophore, a metallic button covered with washleather. This is by far the most generally useful rheophore; and by using the edge it may be made to answer in the majority of cases for fig. 32. It also has the advantage over the sponge of allowing firm pressure to be made without the inconvenience of water being squeezed out. a, fig. 29,
Fig. 31. Olivary metallic rheophore. Fig. 32. Conical metallic rheophore.
shows the usual method of connecting the conducting cord with the rheophore, which is seen in situ, received into the screw socket of the rheophore in a'. The cord is very apt to get frayed where it passes through the eyelet hole, which spoils it at
That the wire which has been previously recommended is not open to this objection is not the least of its advantages. Figs. 31 and 32 are other varieties of rheophore, fitted chiefly for application to very small muscles, such as the interossei, and some of those of the face. Fig. 33 shows Duchenne's
Method of holding the Sponge-holders in a single hand. method of holding two rheophores. The application is being made to the muscles of the hypothenar eminence with one hand, while the other hand is employed about the instrument. In fig. 34 the conical rheophores are in like manner applied to the face. As it is requisite to administer to a muscle a dose of electricity proportionate to its degree of excitability, the operator should whenever possible have
one hand at liberty. In direct electrization the rheophores must always be applied over the fleshy body of the muscle and not over its tendons, and in order to electrize it completely they should cover the whole of its surface, and when they are not large enough to do this, they must be applied in succession to all points of its surface. The thicker the substance of the muscle the more intense must be the current, because a weak current will only produce excitation of the superficial layers. It is very necessary in practice not to lose sight for a moment of this fundamental axiom, which one is very apt to do, and so unequally to electrize the muscle ; and it is a good rule to promenade, as it were, the two rheophores, held as in fig. 31 or fig. 33, in lines along and across the muscle or Duchenne's method of holding
conical rheophores. group of muscles; keeping them stationary on every point of the muscle for about thirty seconds, and letting the entire application vary from five to fifteen minutes, according to therapeutic requirements. In direct electrization with the interrupted voltaic current it is more usual to maintain one rheophore stationary, and to glide the other in lines from the first. As a rule the positive electrode is the stationary, and the negative the movable one, but this order can be reversed if necessary.
INDIRECT MUSCULAR ELECTRIZATION. When muscular contraction is produced by acting upon the special nerve trunk and branches instead of by placing the rheophores upon the muscle itself, the procedure is termed indirect muscular electrization. For its successful practice a detailed knowledge of anatomical relations is necessary, especially of the position of the muscles and of their nerves with regard to one another, to the sensitive nerves and to the surface of the body. It is common to find variations in the course of the nerves, and in the mode of their distribution among the muscles, so that the points most suitable for their excitation can only be pointed out approximately.
It is convenient to place a broad conductor, such as a sponge contained in a cylinder (fig. 28), upon some little sensitive part of the body, such as the sternum, and to apply a fine-pointed conductor, such as the conical rheophore (fig. 32) to the most superficial point of the nerve it is desired to act upon.
The Head. The trunk of the facial nerve may be excited from the external auditory meatus by pressing a