VIII. Demonstration : To determine the influence of 

 the kathode and anode poles. 



Many of the phenomena of muscle-nerve physiology 

 were inexplicable until a difference was noted (Von Bezold 

 1860), in the influence of the anode and kathode. This 

 difference in the influence of the two poles may be best 

 observed by use of the sartorius muscle of a frog. 



1. Appliances. A double myograph and support; record- 



ing drum; Daniell cell; Pohl commutator; Du Bois- 

 Reymond Key; nonpolarizable electrodes; 5 wires; 

 electrode clamp and support. 



2. Preparation. 



(a) Nonpolarizable electrodes. The Du Bois-Reymond 

 nonpolarizable [N P] electrode is made as follows: 

 (Fig. 9). T. Glass tube of about 4 mm. lumen. Z. 

 Zinc rod with a binding screw (B). The zinc 

 rod must be amalgamated before use in an electrode. 

 R. Rubber tube clasping both glass tube and zinc 

 rod. S. Saturated solution of sulphate of zinc, in- 

 troduced with a narrow pointed pipette. C. Kaolin 

 plug, made by working china clay powder into a stiff 

 paste with normal salt solution. 



The electrodes should be filled at each time of using, 

 and the parts may be "assembled " in the order and man- 

 ner enumerated in the description. 



(b~] The Fleischl brush electrode differs from the fore- 

 going in substituting the brush of a camel's hair 

 pencil for the kaolin plug. This variation of the 

 N P electrode is somewhat more difficult to pre- 

 pare, but is more convenient for certain uses. 

 61 



