1907.] on Nerve as a blaster of 3fuscle. 615 



is mainly flexion at its joints, the reflex accomplishes along with that 

 some internal rotation of the hip, and some abduction of the thigh. 

 "Why it should do so we shall see presently. Suflice us for the present 

 that, besides the flexor muscles, the nervous system brings into play, 

 at the same time and harmoniously with those, two other great groups 

 of muscles, the internal rotators and the abductors. So perfect is 

 its skill in using the muscles as its instruments that it can deal 

 harmoniously and simultaneously with all these individually complex 

 groups of motor organs as though they were but one. 



Were we to attempt to produce this movement in the limb ex- 

 perimentally without employing its nervous system, we should have to 

 apply I know not how many stimuli simultaneously to more than half 

 the muscles of the limb. Xot only that, but we should have to grade 

 the stimulation of each of these most accurately to a particular 

 strength. AVe should also have to arrange that not only did each 

 stimulus develop its full strength with the right speed, but that each 

 should maintain it for the appropriate time and desist at the right 

 speed and moment, and with proportioned intensity. Moreover, in 

 the real reflex act the contraction of this or that muscle is now 

 stressed, now subdued, with a delicacy and accuracy baffling all 

 experimental imitation. The co-ordination in even the simple reflex 

 we are considering may be likened to that exhibited by a vast 

 assemblage of instruments in very perfect orchestration directed by a 

 supremely capable conductor. 



But it is more subtle and delicate than that, even in the simple 

 reflex we are considering. The co-ordination goes much farther than 

 we have yet assumed. The musculature of the limb is an instance 

 of that kind of musculature which obtains where parts are adapted 

 to move not in one direction only, or one way only, but in many. 

 The limb has to do many different things. It has, according to 

 circumstances, to bend or to straighten, to turn inwards at one time, 

 at another to turn outwards, to move this finger or move that. Its 

 musculature is therefore split up into many different muscles — 

 some doing this, some doing that. Hence it comes that in the limb 

 are muscles which when they contract do with the limb exactly 

 opposite things. Thus we find a set of muscles which bend the 

 knee, and another . which straighten the knee ; so, similarly, at hip 

 and ankle, at elbow, and shoulder, and wrist. These muscles of 

 opposed action are called antagonists. Now in the flexion reflex — 

 the reflex we are considering — when the reflex bends the knee by 

 causing the flexor muscles to contract, what happens with regard 

 to the muscles which straighten the knee ? Do the opponents, the 

 muscles which straighten the knee contract, or does the reflex nervous 

 influence leave these muscles untouched ? It used to be taught that 

 the muscles which straighten the knee, the extensor muscles, contract, 

 and by their contraction exert a moderating influence on the muscles 

 which execute the flexion. That was the anatomical speculation de- 



