the Lumbo- Sacral Plexus of Macacns rhesus. 255 



Part II. (1) Extension at the hip. 



(2) Flexion at the knee. 



(3) Dorsiflexion at the ankle. 



(4) Extension at the ankle. 



(5) E version of the foot. 



(6) Extension of the digits. 



(7) Flexion of the digits. 



(8) Flexion of the hallux. 



(9) Extension of the hallux. 



7th Lumbar Root. Part I. The limb extended at the hip, flexed at 

 the knee, extended at the ankle, with the plantar surface of the foot 

 looking inwards, the digits flexed at their metacarpo-phalangeal 

 joints, and the hallux flexed and adducted into the sole of the foot, 

 beneath the flexed digits. 



Part II. (1) Extension at the hip. 



(2) Flexion at the knee. 



(3) Extension at the ankle. 



(4) Flexion of the digits at their metacarpo-phalangeal 



joints. 



(5) Flexion of the hallux. 



(6) Adduction of the hallux. 



1st Sacral Root. Part I. Interosseal flexion of the digits, with 

 flexion and adduction of the hallux. 

 Part II. (1) Flexion of the digits. 



(2) Adduction of the hallux. 



(3) Flexion of the hallux. 



2nd Sacral Root. No movement in the limb. 



Part III. Direct Observation (after Dissection) of Muscles thrown into 

 action by Excitation of the separate Nerve Roots. 



I next attempted to ascertain as far as possible which muscles are 

 thrown into action by stimulation of the several nerve roots. I a 

 exposing the muscles, great care was taken to separate them from 

 each other, so that any communicated movement of one muscle to 

 another should be avoided, as, unless this is done, it is sometimes 

 difficult to be sure whether a particular muscle is contracting, or 

 whether the movement observed in it is only communicated to it by 

 an adjoining muscle which is in action. 



Two plans were followed in this connexion. In one, each root was 

 successively selected, and all the muscles in action on excitation of it 

 were noted, while, in the other, a particular muscle, or group of 

 muscles, was kept under observation while all the roots which con- 

 tributed to the plexus were separately excited. Thus the results 



