OF VITAL MOTION. 101 



force save one, and in every case we have found con- 

 traction to mark the abstraction of a stimulus. The 

 remaining question, however, opens out, or seems to 

 do so, a serious objection to this view ; for on studying 

 the motion^ which is the effect of the operation of 

 force, and at the same time a correlated expression of 

 force, it appears that the law of vital contraction in 

 muscular tissues, is altogether different from that of 

 ordinary contraction in inorganic bodies. 



This objection is chiefly founded upon some experi- 

 ments of M. Schwann, which were instituted for the 

 purpose of testing the force of muscular contraction in 

 different degrees of this state. In these researches, 

 the experimenter employed a frog, and an apparatus 

 consisting of three parts a stage or platform, a 

 balance, with one arm free and the other connected 

 with an ordinary scale, and a moveable pin, which 

 might be placed over the balance-beam in such a 

 manner as to prevent the ascending movements with- 

 out interfering with those in a downward direction. 

 The frog was prepared by dividing one of the ischiatic 

 nerves, and the principal tendon of the same leg close 

 by its attachment to the heel ; and when this was done, 

 the animal was secured upon the stage, with the divided 

 tendon attached to the empty arm of the balance by a 

 piece of string, and with the nerve drawn out and 

 placed in such a manner that it could readily be 



