the Lumbo- Sacral Plexus of Macacus rhesus. 265- 



different degrees in different nerve roots, and that one group pre- 

 dominates in one root while another predominates in another, lend 

 strong argument to the probability that the arrangement is in great 

 measure a functional one. If the arrangement of nerve fibres in the 

 nerve roots is a purely anatomical one, why should all the fibres 

 destined for the supply of a given muscle not be contained in the 

 same nerve root ? What necessity would there be for the division 

 of the fibres so that one set of them should be contained in one 

 root, while another set is contained in another ? These points are 

 strongly opposed to the supposition that such an arrangement has 

 been brought about without any regard for physiological action- 

 Then, also, the fact that muscles which are known to act in consort 

 are represented in the same nerve root is one which it is difficult to 

 interpret by mere anatomical arrangement without regard for physio- 

 logical laws. 



Contrary to the observations of Sherrington, I find that the com- 

 pound effect obtained on electrical excitation of a nerve root may be 

 resolved into its component factors, when it is found that movements 

 diametrically opposed to each other may be represented in the same 

 nerve root, e.gr., flexion and extension. 



It seems to me that some of S her ring-ton's own results point in 

 this direction ; for although he makes the statement that each small 

 bundle of nerve fibres in a nerve root represents a miniature root, as 

 it were, yet he finds that by using minimal currents differentiation 

 was obtained in so far that one simple movement was elicited before 

 another as the current was gradually increased in strength. The 

 explanation I would offer for the different conclusions come to on this 

 point by this observer and myself is that he excited the nerve fibres 

 on the proximal side of the intervertebral foramina while I excited 

 them on the distal side. The latter procedure makes it possible to 

 separate the different bundles of nerve fibres contained in a nerve 

 root for a greater distance of their course, and thus to avoid more 

 effectually the possibility of diffusion of the current from the bundles 

 of fibres actually excited to those juxtaposed. I am aware, from my 

 own experience, that it is almost impossible to get any differentia- 

 tions of movements in a nerve root unless the bundles of fibres of 

 which it is composed be first traced well beyond the intervertebral 

 foramen. That this should be the case is only natural, for what is 

 more likely than that the fibres, packed together so closely as are the 

 bundles of a nerve root in their passage through an intervertebral 

 foramen, should make it very easy for the current applied to one set 

 of fibres to diffuse to others in such close contiguity. That separa- 

 tion of one bundle of nerve fibres from another for a sufficient dis- 

 tance in their course is as important a factor in this differentiation 

 of simple movements as is the use of minimum currents for excita- 



T 2 



