1803.] On the Nerve Roots of the lumbosacral Plexus. 459 



II. "An Experimental Investigation of the Nerve Roots which 

 enter into the Formation of the Lnmbo-sacral Plexus of 

 Macaeus rhesus." By J. S. RlSlEN RUSSELL, M.B., M.R.C.P., 

 Assistant Physician to the Metropolitan Hospital. Com- 

 municated by Professor Victor Horsley, F.R.S. Received 

 March 22, 1893. 



(From the Pathological Laboratory of University College, London.) 

 (Abstract.) 



As the history of this subject was fully detailed in a former paper* 

 by the author on the brachial plexus of the Dog, only such experi- 

 mental work as has been done in connexion with the lumbo- sacral 

 plexus is reviewed in the present communication. 



In dealing with the anatomy of the Monkey it is shown that the 

 class of plexus most commonly met with has many features in 

 common with that described by Sherrington as the " prefixed " class 

 of plexus ; while of the variations met with that which occurred 

 most frequently has many points in common with the class of plexus 

 designated " postfixed " by that observer ; but that there is one very 

 notable difference between the last two, as in no instance was the 

 2nd sacral nerve root found to contribute a branch to the sciatic 

 nerve, a contribution which Sherrington describes in this class of 

 plexus. 



Certain indirect effects brought about by muscles in connexion 

 with joints on which they have no direct action, and the necessity for 

 the exclusion of such indirect effects in the study of the movements at 

 these joints, are discussed. The methods employed in operating are 

 detailed, and the plan on which the results are arranged for descrip- 

 tion given. 



Excitation experiments form the first part of the experimental 

 portion of the paper ; and, for convenience, the compound move- 

 ments obtained by excitation of the whole nerve root are described in 

 conjunction with the minute differentiation obtained by excitation of 

 the individual natural bundles of the nerve roots. Following this is 

 a description of the results of the direct observation (after dissection) 

 of muscles thrown into action by excitation of the separate nerve roots. 

 And as a corollary to this part of the subject, the question as to 

 whether a single bundle of nerve fibres representing a single simple 

 movement ever remains distinct in a nerve root during its course to 

 I the muscles which it supplies without inosculating with other motor 

 nerve fibres is considered. The obvious necessity for control experi- 



* 'Phil. Trans.,'. B, 1893. 



2 K 2 



