424 MESSRS. F. GOTCH AND V. HORSLEY 



vary between partial accordance and complete opposition to the above. It is not our 

 object to endeavour to reconcile tin s apparently conflicting evidence, but we may 

 point out that great difficulties are involved in the application of the tests necessary 

 to determine the sensibility of animals. In our own experiments, which have been 

 made upon Cats, and which involved hemisection of the cord, the application of the 

 water and other tests to the skin indicated that the afferent stimulus was conveyed 

 from both hind legs up the cord, but with much greater certainty, and, judging by 

 the quickness in the evoked movement, with much greater intensity, on the uninjured 

 side than on that corresponding with the lesion. 



It is evident that the flaw in all these methods is the fact that, owing to the index 

 of the arrival of impulses above the lesion being some movement, the central struc 

 tures of the nervous system must be sufficiently excitable to be capable of responding, 

 and the stimulus used must be intense enough to arouse discharges of sufficient 

 magnitude to evoke definite muscular movements. 



Whilst the same flaw in the classical experiment is also present in the case of 

 efferent tracts, its presence here does not produce such a blurring of the result, since 

 the method can always be checked by a concluding experiment involving division of 

 the cord below the medulla, and excitation of its distal portion, with observation of 

 the amount and character of the movements of the lower limbs. Although acknow 

 ledging to the utmost the value and precision of the experiments carried out in 

 LUDWTG S laboratory, we must express our conviction that, as regards the conduction 

 of afferent impulses, they do not warrant the inference either that the lateral columns 

 contain the fibres of the afferent tract to the exclusion of the grey matter and the 

 other columns, or that the fibres which they do contain form a continuous afferent 

 path, it being quite possible that those fibres which undoubtedly conducted at the 

 point of section were merely acting as internuncial links between distal and proximal 

 portions of the grey matter. This latter was, by the exigencies of the method of 

 observation, often, if not always, thrown into a state of abnormal excitability ; and in 

 the neighbourhood of the section this state was that of hyperexcitability. 



It will be gathered from what has been said that the question of the relations of 

 the fibres in the cord to the posterior roots can, in our opinion, only be arrived at by 

 the use of a method which allows of discrimination between events taking place in 

 the cord itself when, by means of complete anaesthesia, the activity of the reflex 

 mechanisms is subdued. Such a method is that of ascertaining the electromotive 

 changes in a portion of cord following stimulation of the afferent nerves, since the 

 animal may be so profoundly anaesthetised as to give little or no reflex muscular 

 contraction, and yet distinct effects can be detected in the cord. It is because the 

 conclusions to be drawn from our results clash so markedly with those of MIESCBER, 

 WOROSCHILOFF, &c , that we have thought it necessary to preface their introduction 

 into this section by this detailed criticism. This divergence in the conclusions and the 

 importance of the effective application of a method which besides the above advan- 



