the Lumbo-Sacral Plexus of Macacus rhesus. 261 



this root was also divided no intrinsic movement of the limb could 

 be observed during the cortical discharge. 



On excluding the 1st sacral root alone on one side, no tangible 

 difference in the positions of the limbs on the two sides could be 

 detected during the general convulsions evoked by absinthe. 



Exclusion of the 7th lumbar alone caused an increase of flexion at 

 the hip on that side, owing to the extensors being weakened, while 

 there was more extension and less flexion at the knee, because the 

 hamstrings are represented in this root, marked tibial dorsiflexion at 

 the ankle, as the extensors were enfeebled, and flexion of the digits 

 at the phalangeal joints. When the 1st sacral was divided in con- 

 junction with the 7th lumbar root, the limb assumed exactly the 

 same position as in the last experiment, except that the digits were 

 not so powerfully flexed, and the hallux was not adducted, move- 

 ments which excitation of these roots evoke. The marked feature 

 which was noticeable after division of the 6th lumbar root, in addi- 

 tion to the two last mentioned, was that there was no sign of move- 

 ment of the digits or hallux during the convulsions, because, of 

 course, all the roots excitation of which produced movements of these 

 parts were divided. 



Combined section of the 5th, 6th, and 7th lumbar roots allowed of 

 flexion at the hip, feeble extension at the knee, and flexion at the 

 digits, with adduction at the hallux, during the cortical discharge. 

 The foot remained quite motionless at the ankle joint, as was to be 

 expected, seeing that excitation of no nerve root other than these 

 produced movement at this joint. 



Alternate roots were divided in the following combination, and the 

 position of the limb observed during general convulsions. The 4th 

 and 6th lumbar roots divided together caused flexion at the hip to be 

 less marked, as was flexion at the knee, dorsiflexion at the foot, and 

 flexion of the digits. There was thus a weakening of all the move- 

 ments which predominated when all the roots were intact. 



Section of the 5th and 7th lumbar roots, at the same time, was 

 responsible for more marked flexion at the hip and knee and dorsi- 

 flexion of the foot. So that, although one of the roots which supplies 

 the quadriceps extensor and one of those which supplies the ham- 

 strings was divided, the section of that to the former group of 

 muscles was attended with the greater result, for it allowed the 

 remaining flexor root to predominate, so to speak, over the remaining 

 extensor root to a greater extent than did the two flexors over the 

 two extensors before any of the roots were divided. 



Corollary to Part V. 



It seemed desirable to test carefully the question as to whether 

 section of a root or roots some time previous to that at which the 



