190 ELBCTEIC FOEOE CHAP. X. §.1. 



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 frogf in lieu of the galvanoijaeter ; the 

 results were not so satisfactory as could be desired, 

 to justify their being recorded. 



The posterior limbs of a frog, separated at the 

 pelvis, but connected by means of the lumbar nerves 

 and a portion of the vertebral column, were each 

 placed in separate vessels containing the solution of 

 common salt; the muscles of one limb were then 

 made to contract, and an immediate effect upon the 



be denied that it frequently happens, upon the fiist repetition 

 of the experiment, that the cnrrent may appear in fiayonr of this 

 opinion. Desfeetz has remarked, that the current ma; appear 

 first in one direction and then in another. I cannot insist too 

 strongly upon the necessity of having the hands perfectly clean, 

 and I am convinced that the failures and contradictory results 

 which arise are due more to the want of attention on tliia point 

 than to any thing else. The direction of the current is a fact 

 of the utmost importance, as we shall hereafter see. 



P The term rheoscopic has been recommended in the Report 

 of the Committee of the Academy of Paris, in preference to that 

 of galvanoscopic. I have employed 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 shewn to exist. If the dynamic condition and the 

 current condition of force be considered as equivalent terms, 

 then rheoscopic would be unobjectionable. 



