BY DR. MICHAEL FOSTER. 379 



careful that the amount of contact between the electrodes and 

 muscle is as nearly as possible the same in all cases: 



One electrode on the mid-longitudinal point, the other at 

 the other transverse section. The current will be, as before, 

 from the longitudinal surface to the transverse section. 



06s. VI. One electrode on or near the mid-longitudinal 

 surface, the other at a point nearer either transverse section. 

 The current will be slight, and its direction will be from the 

 point on or near the mid-longitudinal point to the one farther 

 off. 



06s. VII. The two electrodes on the longitudinal surface 

 on either side at unequal distances from the middle point or 

 equator. The current will be slight, and from the point nearer 

 the middle to the point farther off. 



06s. VIII. The two electrodes on the longitudinal surface 

 at equal distances from the middle point on either side; there 

 will be little or no current at all. 



06s. IX. By using very pointed electrodes, evidence of a 

 current may be obtained on the transverse section from the 

 electrode farther from the centre to that nearer to the centre. 



06s. X. The student may repeat these observations on a 

 muscle to which an artificial longitudinal surface has been 

 given by a clean section, and also on a muscle, the tendons of 

 origin and insertion of which have been divided without injury 

 to the muscular fibres, i. e., on a muscle with natural trans- 

 verse surfaces as well as a natural longitudinal surface. 



In all cases the following result will come out more or less 

 clearly: 



In any muscle, or piece of muscle, with natural or artificial 

 longitudinal and transverse surfaces evidence may be obtained 

 of a current passing through the electrodes from the middle of 

 the longitudinal surface (from the equator} to the centre of 

 either transverse section, and from any point nearer the equa- 

 tor to any point nearer the centre of either transverse section ; 

 the current is stronger the farther apart these tivo point* lie 

 (see fig. 288, where the direction of the currents obtainable 

 from a piece of muscle of rectangular form is indicated by the 

 arrows, and the intensity by the sweep of the curves. The 

 points a a, equidistant from the equator, give no current). 



06s. XI. Immerse the muscle, on which you have been 

 experimenting, in water at 40, in order to kill it. As soon 

 as it is cool, repeat the above observations. No currents at 

 all, or very trifling ones, will be obtained, if the muscle be 

 perfectly and completely "rigid.'' 



The currents obtainable from a living muscle disappear 

 when rigor mortis is complete. 



In all cases examine the electrodes by themselves, after any 

 series of observations, as well as before, in order to be sure 



