DOUBLE CONDUCTION IN NERVE. 



207 



tator, and on stimulating at B a much stronger contraction 

 is obtained, because the excitability of a nerve is greater 

 further from a muscle. 



4. Double Conduction in Nerve Kiihne's Experiment on the 

 Gracilis. The gracilis is divided into a larger and smaller 

 portion (L) by a tendinous inscription (K) running across it 

 (Fig. 95). The nerve (N) enters at the hilum in the larger 

 half, and bifurcates, giving a branch (k) to the smaller portion, 

 and another to the larger portion of the muscle. 



(a.) Excise the gracilis from a large frog, and cut it as 

 shown in Fig. 96, avoiding injury to the nerves, so that 

 only the nerve twig (k) connects the larger 

 and smaller halves, and in one tongue (Z) 

 terminates a nerve. The gracilis after 

 excision must be laid on a glass plate with 

 a black background, else one does not see 

 clearly the inscription and the course of the 

 nerves. Both are easily seen on the black 

 surface. 



(6.) Stimulate the tongue (Z) with fine 

 electrodes about 1 mm. apart, and con- 

 trnction occurs in both L and K This 

 can be due only to centripetal conduction the Gracilis. 

 in a motor nerve, and this experiment 

 is adduced by Kiihne as the best proof of double conduction 

 in nerve fibres. 



