42 



EXPERIMENTAL GENERAL PHYSIOLOGY 



into degrees; rheostat or resistance box, representing at least 100 



ohms. 



! ;2. Experiments and Observations. (1) (a) Join up apparatus as 



shown in Fig. 20. With the plugs all fixed in the rheostat i. e., 



with no resistance except that of the wires and battery, and the 



indicator needle at open the key and then observe the angle at 



which the needle comes to rest. 



FIG. 20 



(6) Remove from the rheostat the plug which will throw into the 

 circuit an extra resistance of 10 ohms. Allow the needle to come to 

 rest and note angle. 



I (c) Remove from the rheostat plugs which will represent in the 

 aggregate 100 ohms extra resistance. Note angle of indicator as 

 before. 



(2) Join up two cells in multiple arc, as shown in Fig. 21. That 

 is, join both copper plates to one copper wire and both zinc 

 plates to another. These wires are to be carried to key, rheostat, 

 and galvanoscope, as shown in Fig. 20. 



(a) Note angle of needle with no extra resistance. 



(6) Note angle with 10 ohms extra resistance. 



(c) Note angle with 100 ohms extra resistance. 



FIG. 21 



(3) Join up four cells in multiple arc or "abreast," and repeat 

 the observation of angle at the three resistances as above. 



(4) Join up six cells in multiple arc and repeat observations with 

 ohm, 10 ohms, and 100 ohms resistance. 



(5) Join up two cells in series, as shown in Fig. 22. That 

 is, join the copper of the first cell to the zinc of the second. The 

 first cell will have a zinc uncoupled and the second will have 

 a copper plate uncoupled. These two uncoupled terminal plates 

 of the battery are the ones from which to lead off the wires to the 



