650 CURRENTS OF INJURY IN MUSCLE AND NERVE. 



1. Perfectly fresh, uninjured muscles exhibit no current at all, nor do 

 wholly dead muscles. 



2. Strong electrical currents are observed if, as in Fig. 225, I M, the 

 transverse section of the muscle is connected with one unpolarizable 

 electrode, while the surface, or longitudinal section, is connected with 

 the other. The direction of the current in the connecting wire is from 

 the positive, longitudinal section to the negative, transverse section, 

 therefore in the muscle itself from the transverse to the longitudinal 

 section (Fig. 225, I, and Fig. 228, I). This current is the stronger 

 the more one electrode is approximated to the equator and the other 

 to the center of the transverse section. The strength diminishes the 

 more the electrode applied to the surface approaches the extremity 

 and the more the electrode applied to the transverse section approaches 

 the margin of the section. The demonstration of the strong current 

 may even be made on a single, isolated muscle-fiber. Unstriated muscles 

 also exhibit similar currents between transverse section and surface. 



3. Feeble electrical currents are obtained: (a) If the electrodes 

 are applied at two points on the surface unequally distant from the 

 equator. The current then passes from the positive point nearer the 

 equator to the farther removed negative point, in the muscle naturally 

 in the reversed direction (Fig. 228, II, k e and 1 e). (b) Equally feeble 

 currents develop on applying the electrodes to points on the transverse 

 section unequally distant from the center, the current passing from 

 the point nearer the margin of the section to that nearer the center 

 of the section, in the muscle itself in the opposite direction (Fig. 228, 

 II, i c). 



4. If the application be made to two points on the surface equidis- 

 tant from the equator (I, x, y; v, z; II, r, e) or to two equidistant from 

 the center of the transverse section (I, c) no current appears. 



5. If the transverse sections of a muscle are made obliquely (III), 

 so that the form of the section is rhombic, the conditions present will 

 be. the same as those described in paragraph 3. A point close to the 

 obtuse angle of the transverse section or of the surface is positive with 

 relation to one equally near the acute angle. The equator passes ob- 

 liquely (a, c). These divergent currents are designated inclination- 

 currents and their course is indicated by the lines 1,2, and 3, III. 



The electromotive force of a strong muscle-current, in the frog, is equal to 

 from 0.035 to 0.075 of a Daniell cell, and in the case of the strongest inclination- 

 currents even up as much as o.i. The muscles and nerves of a curarized animal 

 exhibit at first stronger currents. Exhaustion of the muscle diminishes the strength 

 of the current, and it disappears entirely on the death of the muscle. Elevation 

 of the temperature of a muscle increases the current, but a temperature above 40 

 C. again enfeebles it. Reduction of the temperature lessens the electromotive 

 force. A current that has become feebler in the course of a short time can be 

 made stronger by application of the electrodes to a new transverse section. 

 Heated living muscular tissue and nerve-tissue are positive to cooler tissues of the 

 same kind. 



6. The resting nerve exhibits with reference to the conditions de- 

 scribed in paragraphs 1,2, and 3 effects analogous to those of the muscle. 



The electromotive force of the strong nerve-currents, conducted from trans- 

 verse section and surface, equals 0.02 of a Daniell cell. Heating the nerve to 

 between 15 and 25 C. increases the strength of the nerve-current, while higher 

 temperatures enfeeble it. In the development of a strong nerve-current the nega- 

 tivity of the transverse section rapidly diminishes with the death of the nerve. 



