398 



MESSRS. F. GOTCH AND V. HORSLEY 



(c.) No tract of fibres in other columns can have direct and continuous connections 

 with the fibres in one posterior column. 



With maximal intensity of stimulation the interruption is sufficient to lower the 

 posterior effect in the proportion of 164 (that of the uninjured posterior) to 35, that 

 is, 80 per cent. The effect still obtained, in spite of the interruption, must be due to 

 indirect paths which come into relation with cells ; these paths may partly cross or 

 be continuous with fibres contained in the uninterrupted lateral columns on the side 

 of the lesion. The next experiment to be detailed (C) will throw some light upon 

 this point. 



C. Influence of Section of both Posterior Columns and one Lateral. 



By making a hemisection and then dividing the remaining posterior column, a lesion 

 is made (MIESCHER) in which the only intact fibres in the cord are those of one lateral 

 column, one anterior column, and the fibres in one half of the grey matter. 



Such a lesion was made in two animals at the 12th dorsal vertebra, with the 

 following result on the electrical changes in the lumbar cord. 



HEMISECTION on the right side and section of the left posterior column. 



\\, will be seen that with a " minimal " stimulus no electrical effect was evoked 

 except by excitation of that lateral column (left) which remained intact. Hence, the 

 lateral column minimal effect is as strictly localised to its contained fibres as that 

 of the posterior column, and the presumption is that it contains no fibres which 

 are directly continuous with those which form at the level of the 9th dorsal the 

 other lateral and the two posterior columns. 



On the other hand, with a maximal stimulus, excitation of each column evokes an 

 effect, which is, however, much less pronounced than that obtained by the excitation 

 of the uninterrupted lateral. It will be noticed that the posterior column on the 

 side of the uninterrupted lateral gives far the most marked of these effects. If the 

 effects are taken to mean that there exist indirect channels by which nerve impulses 

 may pass from the fibres of any excited interrupted column into those of the uninter- 



