the Lumbo- Sacral Plexus of Macacus rhesus. 263 



lumbar root, while Sherrington and I have found the 6th lumbar 

 root to be the first from above in which the movement is represented. 



Extension at the knee Sherrington places as high as the 3rd 

 lumbar root, while my own observations coincide with those of 

 Ferrier and Yeo, who found the 4th lumbar to be the highest root 

 in which this movement is represented. 



We are all agreed that flexion of the knee is first represented in 

 the 6th lumbar root from above, though Sherrington has also found 

 it represented as high as the 5th lumbar root ; rarely in the " pre- 

 fixed " class of plexus, which resembles most the type of plexus I 

 have most commonly met with. 



Ferrier and Yeo do not mention dorsiflexion at the ankle as pro- 

 duced on excitation of any nerve root, while Sherrington and I are 

 agreed that the 5th lumbar is the highest in the series in which this 

 movement is represented. 



We have all found extension at the ankle to be first represented in 

 the 6th lumbar root from above ; but, while Ferrier and Yeo and I 

 find flexion of the hallux and digits first represented in the 6th 

 lumbar root, Sherrington states that it is first represented in the 

 5th. 



With regard to the inferior limit of supply to the limb, Ferrier and 

 Yeo found this to correspond to the 1st sacral nerve root, and this 

 has been the lowest root of the series from which I have been able to 

 obtain any response in the limb. 



Sherrington found that in the " prefixed" class of plexus which he 

 has described, this is the lowest limit of root supply to the limb ; but 

 that in the " postfixed " class this limit extends as low as the 2nd 

 sacral nerve root (9th post- thoracic root). 



The number of times I have met with the type of plexus most re- 

 sembling that described as " postfixed " by Sherrington has not been 

 sufficiently frequent to justify my expressing any decided opinion as 

 to the inferior limit of root supply to the limb in this class of plexus. 

 All I can say is that I have never succeeded in evoking any in- 

 trinsic movement in the limb by excitation of the 2nd sacral root 

 with currents of such strength as elicited movement when applied 

 to other nerve roots, or even with currents very much stronger than 

 this. Only by using such powerful currents that there could be no 

 doubt as to the diffusion of the current beyond the root to which it 

 was applied, was I ever able to elicit any intrinsic movement in the 

 limb. Further, I have failed, by most careful minute dissections, 

 aided by powerful lenses, to trace any nerve fibres from the 2nd 

 sacral nerve root to the sciatic nerve. Of course the crucial test of 

 this point would be to divide the 2nd sacral nerve root in this class 

 of plexus, and observe whether degeneration in the sciatic nerve 

 follows. This I have attempted, but unfortunately the animals in 



VOL. LIV. T 



