100 POLAKtZBD CONDITION OF THE CHAP. IX. 



nutrition, being the same means by which it is pro- 

 duced and maintained. 



Before acceding to these conclusions, it may be 

 reasonably asked, Have we not other evidence, 

 besides that afforded by means of the galvanometer, 

 to indicate an increase in the polarized condition of 

 the nerve? Do not the tetanic contractions, which 

 are observed in a limb whose nerve has been sub- 

 jected to the action of an electric current [inverse), 

 indicate an increased action of the nerve ? 



A current from six of Grove's cells was passed 

 through the limb of a galvanoscopic frog in the 

 inverse direction, and as soon as tetanic contractions 

 were produced, the nerve was divided at the junction 

 of the nerve with the muscles of the limb; the 

 tetanic contractions ceased. The two ends of the 

 divided nerve were now placed in apposition, but no 

 tetanic contractions ensued. This inverse current 

 was again allowed to pass for some time through the 

 nerve thus united, but no tetanic contractions oc- 

 curred upon the breaking of the circuit Great care, 

 however, is required in this experiment to divide the 

 nerve at the exact point where it emerges from the 

 ' muscles, as pointed out by Matteucci, otherwise the 

 tetanic contractions take place. 



The results of this experiment only tend to con- 

 firm what has been already satisfactorily proved by 

 others, that the continuity of- the nerve fibre in the 

 nerve leading to the muscle is necessary for the 

 conduction of the impression excited at the distal 



