52 LABORATORY GUIDE IN PHYSIOLOGY. 



(r) If one has not the zinc rods at hand he may readily 

 prepare an efficient N-P electrode as follows: 1st. 

 Take 5 cm. of No. 16 copper wire, make one end 

 perfectly clean and bright. 2d. Dip the bright end 

 into molten c. p. zinc. The zinc adheres to the 

 wire, and if the dipping be repeated two or three 

 times the lower 1 centimeter of wire will have a 



FIG. 9. 



FIG. 9. Nonparizable electrodes, hand electrode. 



The Du Bois-Reymond N-P electrodes, shown in the two middle 

 cuts, are described in the text V11I-2 (a), (c). 



The Fleischl brush electrode, mentioned in the text [2 (b)], may be 

 prepared by setting the brush in stiff k?olin paste, or if a more perma- 

 nent electrode is desired, in plaster of Paris. 



A plaster of Paris pencil, as shown in the lower left hand cut, may 

 be used for ordinary work with the constant current. 



The hand electrode shown at the right, is used with an induced 

 current. 



thick coating of zinc. 3d. Take a glass tube 10 cm. 

 long, and with a 4 mm. lumen, draw it in the 



