during Muscular Contraction. 195 



made to overcome that arising from either of the two former 

 actions. 



We have not yet alluded to the difference which appears to 

 exist between the results obtained by Du Bois-Reymond and 

 ourselves, viz. the direction of the current. Du Bois-Reymond's 

 experiments indicate that the current is inverse, i. e. from the 

 hand to the shoulder during muscular contraction ; our results, 

 on the other hand, point out that the current is direct, i. e.from 

 the shoulder to the hand. We do not think that our results 

 differ much from those of Du Bois-Reymond ; but as the discus- 

 sion of this question will involve certain theoretical views, what- 

 ever observations we shall have to make will be deferred to our 

 concluding remarks*. 



With the assistance of three friends an attempt was made to 

 increase the effect upon the needle by forming a pile, as it were ; 

 we could obtain the effect, but there was no decided increase. 



Several experiments were undertaken with the rheoscopic frog-\ 

 in lieu of the galvanometer ; the results were not so satisfactory 

 as could be desired, to justify their being recorded in the pre- 

 sent paper. 



The posterior limbs of a frog, separated at the pelvis, but 



* Since this paper was presented to the Royal Society, we have had the 

 opportunity of attending the interesting lectures of Du Bois-Reymond at the 

 Royal Institution. Du Bois-Reymond considers, as far as we could under- 

 stand, that when the whole of the hands are immersed in the solution, and 

 the muscles of the arm are made to contract, then the current is due to 

 the swollen state of the sldn, and perhaps to other circumstances ; but 

 should we be justified in concluding, that when the fingers alone are in the 

 vessel, then the effect is due to their swollen state ? If Du Bois-Rev- 

 mond maintains that the cmi-ent due to muscular contraction is inverse, 

 i. e. from the hand to the shoulder, we can only add that we have never 

 been able to obtain that constant effect. We cannot deny that it frequently 

 happens, upon the first repetition of the experiment, that the current may 

 appear in favour of this opinion. Despretz has remarked, that the current 

 may appear first in one direction and then in another. We cannot insist 

 too strongly upon the necessity of having the hands perfectly clean, and we 

 are convinced that the failures and contradictory results vvhich arise are 

 due more to the want of attention on this point than to anything else. The 

 direction of tiie current is a fact of the utmost importance ; and as we shall 

 refer to this subject again in the concluding remarks, and as no reasons 

 have occurred to ieaii us to alter our views, we prefer leaving tlie paper in 

 its original state. (June 19.) 



t The term rheoscopic has been recommended in the Report of the 

 Committee of the Academy of Paris, in preference to that of (/alvcmoscopic. 

 We have em])loyed both terms. When it is used for the detection of the 

 current, the former term is most applicable ; but the frog may be a test of 

 a force in which the current' force, in accordance with our present notions 

 of force, cannot be shown to exist. If the dynamic condition and the cur-^ 

 rent condition of force be considered as equivalent terms, then rheoscopic 

 would be unobjectionable. 



