244 Mr. J. S. R. Russell. On the Nerve Roots of 



not alluded to, as they were mere conjectures, unsupported by any 

 substantial evidence. The works of Krause, Schwalbe, Herringham, 

 and Paterson were quoted as evidence of how far the problems -con- 

 nected with this subject have been elucidated by anatomical investi- 

 gation, and the observations of Erb, Knie, and Thorburn alluded 

 to as showing what advance had been made in the subject by the 

 study of diseased processes in man. 



Our knowledge of this subject has been greatly increased by 

 numerous experimental researches, the latest of which is that by 

 Sherrington. As his work is of such recent date and contains a 

 historical account of all previous experimental researches that have 

 been carried out in connexion with the lumbo-sacral plexus, it would 

 be superfluous for me to do more than give a list of references to the 

 various communications on the subject, including that of Sherrington, 

 which list will be found at the end of this paper. 



ANATOMICAL INTRODUCTION. 

 The Lumbo-sacral Plexus in the Monkey. 



Forgue, who does not mention what class of monkey he is dealing 

 with, represents in diagrammatic form the nerves with the roots from 

 which they are derived as follows : The anterior crural from the 

 4th, 5th, and 6th lumbar nerve roots ; the obturator from the same 

 roots ; and the sciatic from the 5th, 6th, and 7th lumbar and the 1st 

 sacral nerve roots. The 2nd sacral root is also figured as sending 

 a branch to the 1st sacral root before the latter enters the sciatic. 



Sherrington describes two chief types of plexus in the monkey 

 (Macacus rhesus) ; what he calls a " postfixed " and a " prefixed." 

 The former is figured as having the following arrangement. The 

 external cutaneous takes its origin from the 3rd and 4th lumbar ; the 

 3rd lumbar also sending a branch to the 4th before the latter enters 

 the anterior crural and obturator nerves, which it does in conjuga- 

 tion with the 5th lumbar root, both nerves also obtaining a filament 

 from the 6th lumbar, while the sciatic is represented as springing 

 from the 6th and 7th lumbar and 1st and 2nd sacral roots. 



The representation of the "prefixed" plexus shows the origin of 

 the external cutaneous nerve to be the same as in the " postfixed " 

 type, while the branch from the 3rd to the 4th lumbar root is repre- 

 sented as joining the latter after it has given its branch to the external 

 cutaneous nerve. This branch from the 3rd to the 4th lumbar ap- 

 parently is supposed to send fibres to both the anterior crural and 

 obturator nerves ; these nerves also receiving branches from the 4th 

 and 5th lumbar roots. The sciatic is figured as formed from the 5th, 

 6th, and 7th lumbar and 1st sacral nerve roots. 



That Forgue's representation of the arrangement of the plexus does 



