THE MUSCULAR SYSTEM. 



405 



lution, part of which projects through its drawn-out point; the rest of 

 the cylinder is fitted with a saturated solution of zinc sulphate into which 

 dips a well amalgamated piece of zinc which is connected by means of a 

 wire with the galvanometer. In this way the zinc sulphate forms a 

 homogeneous and non-polarizable conductor between the zinc and the 

 china clay. A second electrode of the same kind is, of course, neces- 

 sary. 



In a regular muscle prism the currents are found to be as follows: 

 If from a point on the surface a line the equator be drawn across 

 the muscle prism equally dividing it, currents pass from this point to 

 points away from it, which are weak if the points are near, and increase 

 in strength as the points are further and further away from the equator; 

 the strongest passing from the equator to a point representing the mid- 

 dle of the cut ends (Fig. 283, 2); currents also pass from points nearer 

 the equator to those more remote (Fig. 283, 1, 3, 4), but not from points 

 equally distant, or iso electric points (Fig. 283, 6, 7, 8). The cut ends 



FIG. 233. Diagram of the currents in a muscle prism. (Du Bois Beymond.) 



are always negative to the equator. These currents are constant for 

 some time after removal of the muscle from the body, and in fact re- 

 main as long as the muscle retains its life. They are in all probability 

 due to chemical changes going on in the muscles. 



The currents are diminished by fatigue and are increased by an in- 

 crease of temperature within natural limits. If the uninjured tendon 

 be used as the end of the muscle, and the muscle be examined without 

 removal from the body, the currents are very feeble, but they are at 

 once much increased by injuring the muscle, as by cutting off its tendon. 

 The last observation appears to show that they are right who believe that 

 the currents do not exist in muscles uninjured in situ, but that injury, 

 either mechanical, chemical or thermal, will render the injured part 

 electrically negative to other points on the muscle. In a frog's heart it 

 has been shown, too, that no currents exist during its inactivity, but 

 that as soon as it is injured in any way they are developed; the injured 

 part being negative to the rest of the muscle. The currents which have 



