File:A text-book of physiology for medical students and physicians (1911) (14778349102).jpg

Identifier: textbookofphysio1911howe (find matches)
Title: A text-book of physiology for medical students and physicians
Year: 1911 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology
Publisher: Philadelphia, London, W.B. Saunders company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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ipolar method of stimulation in man. The anode,-f, is represented as the stimulating pole, applied over the median nerve. The cathode,—, is the indifferent pole. with the skin each is covered with cotton or chamois skin keptmoistened with a dilute saline solution. Motor Points.—By means of the unipolar method nearly everyvoluntary muscle of the body may be stimulated separately. Allthat is necessary, when the induced current is used, is to bring theactive electrode as nearly as possible over the spot at which themuscle receives its motor branch. A diagram showing these motorpoints for the arm is given in Fig. 35. In the same way the THE PHENOMENON OF CONDUCTION. 93 nerves of the brachial plexus and other nerve trunks may bestimulated very readily through the skin. When the inductioncurrent is used no distinction is made between the cathodic andanodic effects. When, however, the battery current is employed M. dcltoideus — Verv. fnuscrtloculaneuMM* biceps brachiiM. br.tch Internuj
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Fig. 35.—Motor points in upper extremity. one may make the stimulating electrode either anode or cathode,and under these circumstances a marked difference is observedin the strength of the current that it is necessary to use toget a response. With the battery or galvanic current, in fact,one may distinguish four stimuli, the closing and the open-ing shock when the stimulating electrode is cathode and theclosing and the opening shock when it is anode. The con-tractions resulting from these four stimuli are designated usuallyas follows: The cathoclol closing contraction, C C C; the cathodalopening contraction, C 0 C; the anodal closing contraction,A C C; and the anodal opening contraction, A O C. If the minimalamount of current necessary to give each of these contractionsis measured in milliamperes by means of a suitable ammeter, 94 THE PHYSIOLOGY OF MUSCLE AND NERVE. it will be found that the four stimuli are of different efficiencies.The usual relationship is expressed by the sequen

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