98 APPENDIX I. 



central, or of the impressions of external objects 

 upon its peripheric end. 



This was illustrated by placing the sciatic nerve 

 of a frog, still attached to the gastrocnemius muscle, 

 on three electrodes, A, B, C A being the remotest 

 from, and C the nearest to, the muscle. A being 

 connected with one end of a self-acting induction 

 apparatus, and either B or C with the other end, a 

 strong tetanus of the muscle ensued, and was ren- 

 dered visible by the raising of a little mica flag ;* but 

 after a ligature had been tightened around the nerve 

 between B and C, which was simply done by pressing 

 down a lever , j the tetanus was observed to arise only 

 on making the connection with C, because only then 

 a portion of the nerve between the ligature and the 

 muscle was stimulated, whereas, on making the con- 

 nection with B, the ligature intercepted the effect 

 produced by the stimulation of the portion A B. 



These facts, the speaker said, are calculated to 

 impress us with a notion of something moving along 

 the nerves in the act of volition and in that of sen- 

 sation, which, to preclude any hypothetical view 

 regarding its nature, we will term the nervous agent. 

 As this agent for its conveyance requires an un- 



* See the description and drawing of the apparatus in 

 Beschreibung einiger Vorrichtungen und Versuchsweisen zu 

 elektrophysiologischen Zwecken. Von E. du Bois-Keymond. 

 Abhandlungen der K. Akademie der Wissenschaften zu Berlin, 

 1862, S. 141. 



t The apparatus used is described and figured in Unter- 

 suclmngen uber thierische ElektridtdL Von E. du Buis- 

 Eeymond. Bd. ii., Abth. i. Berlin, 1849. S. 341 ; Taf. iii., 

 Fig. 109, 110. 



