IV 



ELECTROMOTIVE ACTION IX MUSCLE 



325 



aspect is covered in its lower two-thirds by tendon-substance, 

 continued below into the tendo achilles" (Fig. 104). 



The gastrocnemius is therefore provided by nature with an 

 oblique transverse, and a natural longitudinal section, which 



Fio. 104. Schema of Gastrocnemius structure. (Du Bois-Reymond.) 



include the whole of the flat, and a small part of the bulging 

 surface. This is in correspondence with the characteristic dis- 

 tribution of potential on the surface of the muscle. If a regular 

 muscle cylinder is twisted obliquely (Fig. 105) so that the 

 terminal cross-sections run parallel with each other, but obliquely 

 with the axis, the curve of greatest positive potential corresponds, 

 not with the equally oblique, centrally placed, elliptical equator, 

 but with a winding curve drawn towards the blunt corners. 

 Conversely, the negative potential is greater at the sharp, than at 



FIG. 105. Distribution of potential in oblique muscle cylinder. (Rosenthal.) 



the blunt, corners of the cross-section. When there is no current 

 through the regular muscle cylinder, so that the contacts of the 

 leading-off circuit are equidistant from the geometrical equator, 

 it is evident that a current will be obtained, flowing in the muscle 

 from sharp to blunt edge (du Bois' " Neigungstrom "). Such 



