590 



PHYSIOLOGY. 



with a low-power microscope the mercury will move in a direction 

 showing a higher potential at the positive electrode on the longi- 

 tudinal surface. 



Instead of a transverse section of a muscle its tendon may he 

 taken, which is also negative and has been called the natural trans- 



Fig. 225. Direction of Current of Daniell Cell. 



Through the galvanometer the current is from copper to zinc. Through the cell 

 the current is from zinc to copper. 



verse surface. The cut surface of a longitudinal section of muscle 

 presents positive electrization. The laws of electrical currents of 

 muscle have been fully determined by DuBois-Reymond: 



1. When the conductor unites the longitudinal to the transverse 

 surface there is a well-marked deviation of the needle, and the great- 



Fig. 226. Direction of Current of Injured Muscle. (WALLER.) 

 Through the galvanometer the current is from normal to injured part, or 



from resting to active part. Through the muscle the current is from injured to 



normal part or from active to resting part. 



est deviation occurs when the middle of the longitudinal surface is 

 connected with the middle of the transverse. 



2. When two points are connected on a longitudinal or trans- 

 verse surface which are unequally distant from the middle, or two 

 points unequally distant on opposed surfaces, then there is a slight 

 deflection of the needle. In the case of the longitudinal surfaces the 



