the Lumbo-Sacral Plexus of Macacus rhesus. 253 



Combine to form the plexus is in most instances too small to allow of 

 the minute bundles of nerve fibres being separated from each other 

 for a sufficient length of their course. I was always able to differ- 

 entiate several of the movements in each root, but was never able to 

 differentiate all in any given root at the same operation. Another 

 factor which contributes to make this process of minute differentia- 

 tion so difficult is the delicacy of the nerve roots in the monkey as 

 compared with those of the dog, as injury of the nerve fibres is more 

 difficult to prevent in consequence, in the process of their separation 

 from each other. With these difficulties to contend with, the pro- 

 cess of differentiation of the various movements was aided by the 

 division of muscles and tendons. That is, after it had been ascer- 

 tained that a certain movement at a given joint resulted on excita- 

 tion of a certain bundle of fibres, these muscles or their tendons 

 were divided, and the same bundle of nerve fibres again excited in 

 order to ascertain whether any other movement could be produced 

 at the same joint, e.g., after flexion at a joint had been produced, the 

 flexor muscles acting on that joint were divided, in order to ascertain 

 whether any fibres representing extension existed in the bundle of 

 nerve fibres under investigation. 



This minute differentiation forms therefore the second part of the 

 investigation. 



Thus far the investigation dealt with movements ; it was obviously 

 necessary to pursue the matter further, and to see upon dissection 

 what individual muscles were innervated by the various roots, or 

 their parts when successively excited. This forms the third part of 

 the work. As a corollary to this latter question, I have attempted 

 to determine to what degree any given root supplies a muscle 

 when the latter is innervated from more than one root, and whether 

 any given muscle fibre is possibly supplied from more than one 

 root. 



The necessity of instituting new experiments in control of the 

 results obtained by the foregoing methods led to the institution of 

 the following procedures. 



Of these, the first, constituting the fourth part of the investiga- 

 tion, consisted in dividing one or more roots, and then observing 

 what effect was produced thereby in the direction of alteration 

 of the natural gait or movement of the limb in progression and 

 climbing. 



Another control method, the results of which are embodied in the 

 fifth part, was devised as follows : A nerve root was divided (in 

 some cases more than one), general epilepsy was then induced by 

 intravenous injection of the essential oil of absinthe, and the resulting 

 deficient participation in the fit of the limb in relation with the divided 

 root or roots carefully observed. 



