518 MESSRS. F. GOTCH AND V. HORSLEY 



the entering root, both by direct and indirect paths, a small minority ascend by the 

 posterior column of the opposite side, and a mere fraction by the lateral column of the 

 opposite side. 



(6.) The direct path of afferent impulses is localised in the posterior column of the 

 same side as that of the nerve or root excited. 



(c. ) The indirect paths of afferent impulses are localised in the posterior columns of 

 both sides, and in the lateral column of the same side as that of the excited nerve. 



(d.) The proportionate development of both systems of nerve paths in the two 

 sides of the cord may be inferred from the percentages of the total transmission of 

 excitatory electrical changes from the afferent nerve to the cord. 



Of the electrical changes there are transmitted by : 



Same side. 



Posterior column of same side as excited nerve . . 60 per cent.] 



^80 per cent. 

 Lateral . . 20 J 



Opposite side. 



Posterior column of opposite side to ..15 "l 



, ^20 per cent. 



Lateral . . 5 J 



(See Chapter IX.) 



B. The descending electrical effects, as far as the relationship of the cord and nerves 

 is concerned, were investigated in the mixed nerve, the spinal cord being severed from 

 the encephalon and excited. 



The results of these experiments, obtained with both minimal and maximal 

 stimuli, and controlled by the exclusion method of intervening sections, were as 

 follows : 



(a.) On minimal excitation of the posterior column, impulses are directly trans- 

 mitted into the posterior roots of the same side, and so into the mixed nerve ; with 

 maximal excitation some impulses are similarly transmitted through indirect paths. 



(b.) On maximal excitation of the posterior column, impulses are transmitted by 

 indirect paths across to the posterior roots of the opposite side, and so to the mixed 

 nerve of that side. 



(c.) On excitation of the lateral column, impulses are indirectly transmitted to the 

 mixed nerve of the same side as that of the excited column. 



(d.) The proportionate percentage of the total transmission of excitatory electrical 

 states from the various excited columns of the dorsal cord into the mixed nerves is as 



follows : 



per cent. per cent. 



Excitation of posterior column of same side as observed nerve 73 1 . , 



, > Same side 82 



lateral 9J 



posteri 



lateral 



posterior opposite 15~l 



of lb 



3J 



