262 ON POSITIVE VARIATION OF THE NEEVE CURRENT 



while the galvanometer-circuit is closed by the switch, to join to- 

 gether the four wires of the switch at both points of interruption of 

 the stimulating current, so as to convert them into two continuous 

 wires. Moreover, as it is desirable not to let the individual stimu- 

 lations of the nerve follow each other too rapidly, there is ample 

 time to use each arrangement alternately, and thus to observe first 

 the positive variation alone, then the negative with the positive 

 following. 



With the last-mentioned method of observation (' without switch') 

 I found without exception a smaller positive variation than with 

 the other. 



A few examples will make this clear. 



Cold frog. Excitation with rotation apparatus. Galvanometer tract 8 mm. 

 Intermediate tract 37-5 mm. Duration of stimulation 20 sees. 

 Current of electrodes 38. Nerve .current +188. 

 I. Stimulation with switch + 21 III. Stimulation with switch +13 



II. without switch j ~ 38 IV ' " + 12 



The positive variation of 2,1 which appeared with the first stimu- 

 lation is the greatest I have ever seen. It was also very lasting, for 

 20" after reaching the maximum, a deflection of + 10 was still 

 shown. I did not await the complete return of the magnet in order 

 to verify the zero point. 



Warm frog. Stimulation with rotation apparatus. Galvanometer tract 7-5 mm. 

 Intermediate tract 33 mm. Duration of stimulation 20 sees. 

 Current of electrodes 46. Nerve current + 167. 



I. Without switch |~ 26 III. Without switch 



H. With switch +13 IV. With switch + 6 



Cold frog. Stimulation with du Bois induction-coil. Galvanometer tract 9 mm. 

 Intermediate region about 30 mm. Duration of stimulation I o sees. 



Current of electrodes +17. Nerve current + 104. 



I. With switch +8 II. Without switch |~ 13 



III. With switch +5-5 



Cold frog. Stimulation with du Bois induction-coil. Galvanometer tract 8 mm. 

 Intermediate tract 25 mm. Duration of stimulation 12 sees. 

 Current of electrodes 43. Nerve current +85. 



I. With switch + 10 III. With switch + 7-5 



II. Without switch j ~ 1 9 IV. Without switch { ~ I > 



V. With switch + 3-5 



