349 



Now Dr. Rousseau shows that the order of contraction set down 

 in the second Table is due to the action of this derived current. He 

 shows, also, that by excluding the derived current (which he does 

 by means of an ingenious triple arrangement of poles called the 

 " rheophore bifurque "), the order of contraction becomes one and 

 the same in the case where the nerve is divided and lifted up at its 

 end, and in the case where the nerve is arranged in a loop, the order 

 being that which is set down in the first Table. 



On inquiring into these matters experimentally, the author finds 

 reason to believe that Professor Bernard has wandered into some 

 degree of error, and that the path of inquiry opened out by Dr. 

 Rousseau is not only a right path, so far as its discoverer has traced 

 it out, but that it leads to the explanation of some very curious 

 alternating movements which have not hitherto been described. He 

 has been led, also, to form certain conjectures respecting the modus 

 operandi of electricity in muscular motion which he trusts may serve 

 to simplify this very difficult and complex subject. 



1. When nerve is in its normal, unexhausted, undivided state, 

 there is, as Professor Bernard points out, contraction at the begin- 

 ning of both currents, inverse as well as direct, and at the beginning 

 only, if a feeble current be used. This, for example, will be the result 

 of the application of the feeble current produced by partially 

 moistening the small galvanic forceps of Bernard with saliva. But it 

 is also a fact, that a stronger current the current for example of a 

 Pulvermacher's chain of ordinary length moistened with vinegar 

 will produce contraction at the end as well as at the beginning of 

 both currents (as in the period of double contraction), if applied 

 to a nerve similarly circumstanced. Nay, it is a fact, that the feeble 

 current of the forceps will give contraction at the beginning of both 



arranged in a loop across the poles P N of a galvanic apparatus ; the primitive 

 current, indicated by the black arrow, passes by the shortest route from the 

 positive pole P to the negative pole N ; the derived current, indicated by the dotted 

 arrows, passes by the longest route between these poles, and as it also proceeds 

 from the positive pole P to the negative pole N, it passes in the contrary direc- 

 tion to that of the primitive current. In fig. 4, the sciatic nerve is divided 

 between P and the thigh, as is meant where the nerve is spoken of as divided 

 and lifted up at its end ; and being divided, the only current passing is the primi- 

 tive current ; for the circuit of the derived current being broken, there can be no 

 derived current in this case. 



