24 



On the Brachial Plexus of the D^g. [Mar. 3, 



in their action in one root, those producing extension predominate in 

 another. 



10. It is possible, by stimulation of a single bundle of fibres in a 

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



11. The same muscle is always represented in more than one nerve 

 root, usually two, and to an unequal extent in these. 



12. When the same muscle is represented in two nerve roots, the 

 muscle fibres innervated by one root are not innervated by the other. 



II. Ablation Experiments. 



1. Division of any given nerve root produces paresis of the group 

 of muscles supplied by it. 



2. This paresis is only temporary, and soon passes off almost com- 

 pletely. 



3. Such division of a nerve root does not result in incoordination 

 of the remaining muscular combinations represented in other nerve 

 roots. 



III. Exclusion of a certain Root or Roots during an Epileptic Spasm in 

 the Limb (the root being divided at the time, and not some time 

 previously), 



1. Division of one or more nerve roots produces alteration of the 

 position of a limb during an epileptic spasm, which altered position 

 depends on the particular muscular combinations that have been thus 

 thrown out of action. 



2. No incoordination is produced in the action of the remaining 

 muscular combinations. 



3. There is no evidence of overflow of the impulses which ought to 

 travel down the divided root into other channels through the spinal 

 centres, so as to reach the muscles by new paths. 



IV. Degeneration Method. 



1. These experiments confirm the anatomical facts that had been 

 previously ascertained by dissection, as to which nerve roots supply 

 any given nerve with fibres. 



2. The degeneration which results in the nerves is not a scattered 

 one, but is localised to distinct bundles of nerve fibres occupying a 

 certain position in the transverse section of the nerve. 



3. The Wallerian law of degeneration is found to be erroneous with 

 regard to the degenerations which result on division of a nerve root 

 on the distal side of the intervertebral ganglion ; for not only is de- 

 generation found in the peripheral end of such a root, but also in that 

 portion of the sensory root between the ganglion and the spinal cord ; 



