1893.] the Lumbosacral Plexus of Macacus rhesus. 



461 



for the regulation of all the movements represented in the compound 

 root, the author finds that each separate bundle of nerve fibres in a 

 nerve root represents a single simple movement, and not all the 

 movements of the compound root in lessened degree. The explana- 

 tion offered for this difference in the results is that possibly Sherring- 

 ton did not separate the bundles of nerve fibres from each other for a 

 sufficient distance in their course, and thus did not effectually exclude 

 the possibility of diffusion of the current to other bundles of nerve 

 fibres contained in the same nerve root. 



The single simple movements thus eliminated are found to bear 

 an almost constant relation to the nerve roots, the same movements 

 being as a rule found in any given root, and such movements always 

 bear the same relation to the spinal level. Further, each bundle of 

 nerve fibres representing a single simple movement in a nerve root 

 remains distinct in its course to the muscle or muscles producing 

 such, a movement, without inosculating with other motor nerve 

 fibres. 



The group of muscles supplied by any given nerve root occupy 

 both the anterior and posterior surfaces of the limb ; in other words, 

 muscles whose unimpeded action would produce one movement are 

 represented in the same nerve root as others whose action would 

 produce a movement diametrically opposite. 



When a certain group of muscles are found to predominate in 

 their action in one root, they as a rule predominate in that root. If 

 those producing flexion at a certain joint predominate in their 

 action in one nerve root, those producing extension predominate in 

 another. 



In those instances in which two opposed movements are repre- 

 sented in three consecutive nerve roots, the middle. root of the series 

 is that in which both movements are represented, while the root 

 above contains the one movement, and that below contains the 

 other. 



As regards the order of representation of the movements of flexion 

 and extension from above down, they are found to alternate, flexion 

 being at a higher level than extension in the highest segment of the 

 limb, while extension is above flexion in the next segment, and so on. 

 And these results are found to agree with those obtained in connexion 

 with the anterior extremity of the Dog, except in the case of the elbow 

 joint in its relation to the knee. 



It is found possible by stimulation of a single bundle of fibres in 

 a nerve root to produce contraction of a single muscle, and of it 

 alone ; but this effect is not nearly so easy to obtain as in the case of 

 the cervico- dorsal roots, owing to the. distance between the points of 

 exit of the roots from the neural canal and those where they unite to 

 form the plexus being too short to allow of sufficient separation of 



