iv ELECTROMOTIVE ACTION IN MUSCLE 435 



to be discussed more fully later on, but which showed that in 

 this case also, each of the two antagonistic muscles is, like the 

 heart, subject to the influence of two functionally different kinds 

 of fibres (inhibitory and excitatory), which run in the same nerve- 

 trunk, and are capable of eliciting opposite mechanical effects. 

 It was natural to suppose that opposite electromotive effects, 

 in correspondence with this antagonism, would obtain in the 

 form of negative, or positive, variations of the muscle current. 

 But there were considerable difficulties in the way of experi- 

 mental investigation ; in the cray-fish, at any rate, it is not 

 possible to isolate the nerve in a state of excitability, while the 

 muscle must be left within the shell ; this, if for no other reason, 

 is imperative from the mode of origin of the component fibres, 

 which spring from a large portion of the inner surface of the last 

 segment of the claw, and for the most part converge to the 

 tendon. The disposition is thus very similar to that of the 

 tendinous expansion of the frog's gastrocnemius. At whatever 

 part of the base of the claw the shell is -opened, an artificial 

 transverse section of the muscle is inevitable, and it is nowhere 

 possible to expose the uninjured surface (natural longitudinal 

 surface) alone. Under these circumstances the most advisable 

 proceeding is to lead off from an injured part within that area 

 of the claw at which fibres of the adductor muscle take origin 

 (the particular position of this led-off point is in general of no 

 consequence), using as a second lead-off from the uninjured 

 muscle some portion of the electrically indifferent tissue that 

 occupies the interior of the hollow limbs of the claw, and may 

 to some extent be regarded as a prolongation of the tendon. To 

 this end a small piece of the shell, preferably near the base of 

 the claw, is broken off from the outer edge, towards either the 

 outer or inner surface, by bone-forceps. A second smaller opening 

 is made at about the middle of the outer edge of the fixed limb 

 of the claw; the small adductor muscle having previously been 

 completely removed to serve as the second lead-off of the 

 demarcation current, while the free limb of the claw serves to 

 indicate any movement due to altered action of the adductor. 

 The exciting electrodes (platinum points) transfixed the longest 

 segment of the claw extremity near its outer border. With this 

 disposition the lead-off nearer to the base of the claw is of course 

 negative to the distal lead-off. 



