OF VITAL MOTION. 85 



an adequate idea of its existence and reality. In 

 this there is no difficulty. We must take a number 

 of the hind legs of the frog, amputated at the pelvis, 

 and stripped of their skin, and arrange them in a 

 series of wine-glasses half filled with water, each leg 

 being bent over the edge of the two contiguous glasses 

 in such a manner that the foot is immersed in one 

 glass and the thigh in the other. A foot and thigh 

 of difierent limbs are thus in every glass, except the 

 terminal ones, in the one of which there is (as must 

 needs be) only a foot, and in the other a thigh. On 

 plunging the poles of a galvanometer into the water 

 contained in the glasses which hold the extremities of 

 this muscular pile, there is a contraction of all the 

 limbs, and a divergence of the needle of the instru- 

 ment in such a direction as to show that a current of 

 electricity has passed from the feet towards the thigh. 

 By adding or diminishing the number of limbs, the 

 divergence of the needle may be increased or lessened, 

 and thus it is found that the intensity of the current 

 is proportionate to the size of the pile. It is found 

 also that the muscular contractions cease after a time, 

 and with them the divergence of the needle ; and in this 

 way we may satisfy ourselves that the development 

 of the electricity is dependent upon the conditions 

 which preserve the muscular irritability, and not upon 

 the mere contact of the limbs as masses of inorganic 

 matter. The nerves would seem to have little to do 



