418 MESSRS. P. GOTCH AND V. HORSLEY 



complete. The essential link, that of connection with the posterior roots, the fibres of 

 which convey afferent impulses, is, however, wanting. It is, notwithstanding, highly 

 probable that these paths (direct cerebellar and antero-lateral), are to be classed as 

 afferent from the resemblance in extension of the degeneration to that present in the 

 fibres of the posterior columns. 



There are many considerations connected with growth, development, &c., which 

 suggest that ascending degeneration is the characteristic of afferent, and descending 

 degeneration of efferent tracts in the spinal cord ; in other words, that the centres of 

 growth and nutrition are also the centres of functional activity, and, therefore, in 

 consequence of an interruption, that loss of functional activity and loss of nutrition 

 both occur in the part on the distal side of the breakdown. The fact, however, that 

 the cells in the ganglion on the posterior root exercise this nutritive function on the 

 nerve fibres on both sides, although explicable in consequence of developmental rela 

 tions (His) must cause some hesitation as to the propriety of accepting, without 

 reserve, the principle that the direction of the degeneration coincides with the direc 

 tion of the function. What has happened in the development of the posterior root 

 fibres may possibly have also occurred in the case of some fibres in the cord. More 

 over, it is conceivable that even with this relation between nutrition and function, 

 ascending degenerative changes might occur in fibres which ought to be classed as 

 outgoing, since they would lie as much on the efferent side of the central nervous 

 system as do those of the pyramidal tract. Such fibres would be long internuncial 

 fibres, connecting the kinaBsthetic system of the lower (lumbar) centres with the 

 efferent side of a similar system of the upper (or cervical) region. It is conceivable 

 that such long internuncial fibres exist, and, if so, then impulses which subsequently 

 become motor are conveyed by them. These impulses, although afferent in the sense 

 that they are actually travelling up the cord, are analogous in character with all the 

 motor or outgoing impulses, since they occupy that relation to the centres from which 

 they started. 



Without insisting on these hypothetical fibres, we may again point out that the 

 anatomical evidence becomes vague when some of the links in the chain are wanting, 

 hence all conclusions founded upon it must be used with the greatest caution. The 

 facts which it surely evidences are 



1. That there are continuous fibres in the cord. 



2 That these fibres do nok cross from one side of the cord to the other. 



3. That a small proportion of those situated in the posterior column are in direct 

 connection with those entering the cord by the posterior roots. 



II. Physiological,. 



If we turn now to the method of physiological experiment, there is hardly any 

 subject in the whole realm of physiology upon which such divergence of experimental 



