Intelligence and Miscellaneous Articles. 399 



of about 2 millims., whilst there is no contraction when the nerve 

 placed crosswise touches the paper for a length of 40 or 50 mil- 

 lims. I need not say that when the galvanoscopic frog is a little 

 weakened, the contraction only takes place at the moment of clos- 

 ing the circuit with the direct current, and that with the inverse 

 current the contraction occurs at the moment when the circuit is 

 broken. 



I must remark here, that in reflecting upon the relation, now well 

 established, between the electro-physiological effects of the current 

 and its direction in the nerve, the difference in the effects found, 

 according as the current traverses a nerve in a direction parallel or 

 transverse to its axis, becomes almost a theoretical consequence of 

 this relation. 



Although the result of the experiment which I have carefully de- 

 scribed is constant and conclusive, I desired to render the experiment 

 still more perfect, and to secure it from a kind of objection which 

 might be raised against it, on the foundation of the theory of derived 

 currents. When the nerve is extended perpendicularly to the cur- 

 rent, the current which traverses it, and which depends, as is always 

 the case, upon the difference in the electrical states of the points 

 touched by the nerve, can only be very weak, in consequence of the 

 thinness of the nerve. We have already said that the experiment 

 succeeds very well when the nerve traversed in the direction of its 

 length touches the paper for scarcely 2 millims., whilst nothing at 

 all occurs even when the nerve traversed crosswise touches the paper 

 for twenty times this length. This mode of operation answers the 

 objection well ; but it may be objected that it does not answer it en- 

 tirely, because it would be necessary that the nerve extended in the 

 direction of its length should only touch the paper for a space equal 

 to that which the nerve occupies with its thickness. 



To remove all doubts, in place of having a continuous paper be- 

 tween the two plates of the pair, I have two pieces of paper, placed 

 on the one hand upon the plates, and on the other nearly in contact, 

 so as to leave a space of 1 or 2 millims. between them. I then 

 make the experiment by filling up the space only with the nerve of 

 the galvanoscopic frog, and having in every case the same length of 

 nerve placed across the space, but arranged in such a way as to 

 have the nerve traversed sometimes longitudinally, sometimes trans- 

 versely by the current. When the experiment is well executed, that 

 is to say, by employing a current which is not too strong, and 

 nerves sufficiently weakened to render them no longer excitable by 

 the passage of the inverse current, the result is the same as that ob- 

 tained in the preceding way. 



If I have been very minute in the description of these experiments, 

 it must be admitted as my excuse, that, as regards the physiological 

 action of the electrical current, it is important to have it rigorously 

 demonstrated that the electric current only acts upon a nerve tuhen it 

 traverses it in the direction of its length. 



The other result at which I have recently arrived, is the consider- 

 able and constant difference in the electromotive power of the muscles 

 of frogs, according as these animals have been killed in the natural 

 state, or after having been poisoned by urari. To malce this com- 



