EELATION BETWEEN STRUCTURE AND FUNCTION. 13 



is a flexor of the hip, although this can, as a fact, be experi- 

 mentally shown; and the mathematical treatment of 

 these problems is far from easy. 



Against the view that any one spinal motor -root 

 represents the motor spinal nerve cells concerned in some 

 particular highly co-ordinate functional synergy, rise a 

 number of facts. These I have detailed elsewhere. 

 Among them are the sudden change which in some 

 motor-roots occurs as the stimulation of the indi- 

 vidual rootlets composing the root is undertaken in 

 serial order ; the upper filaments of the root producing one 

 movement, the lower series another movement ; the upper 

 filaments of the root produce a movement like that 

 produced by the filaments of the root next above, the 

 lower like that of the root next below. Here, then, the 

 collection of the root would contain two functional groups 

 representing two synergies, and the upper one would be 

 simply a replica of that of the functional synergy of the 

 root next above, and the lower that of the root next 

 below. Then the combination of a piece of the diaphragm 

 muscle with supination of the wrist, of flexion of the wrist 

 with extension of the fingers, are bizarre effects unknown 

 in any reflex movement, or movement produced by 

 excitation of the brain. The combination of supination 

 at the wrist with flexion of the hand, is of itself an unusual 

 movement, that usually requires some attention for its 

 execution. 



The degeneration experiments show that in some 

 muscles the number of motor nerve-fibres given by a 

 spinal-root to a muscle is too small to evoke from the 

 muscle any contraction at all obvious to inspection. 

 Cases occur where a limb muscle receive one, two, three, 

 four, or five motor fibres from a particular root ; allow to 

 each of these motor nerve-fibres a dozen muscle-fibres, it 



