400 



MESSRS. F. GOTCH AND V. HORSLEY 



SECTION 10. SUMMARY OF RESULTS. 



It will be well now to express the general conclusions founded upon a comparison 

 of all these experiments, especially those involving the influence of intervening sections 

 upon the cord electrical effects. 



I. If a portion of cord be severed by a dorsal and lumbar section from its connec 

 tions above and below, then stimulation of either lateral or posterior column at one 

 end evokes electrical effects at the other, which are dependent for their amount on 

 the uninterrupted structural continuity of fibres in the particular column excited ; 

 and the electrical changes are thus the index of the arrival at one end, of nerve 

 impulses generated at the other, and propagated mainly along the fibres in each 

 column. 



II. If the stimulus used be minimal, then the interruption due to the section is in 

 every case sufficient to practically abolish the effect ; hence, with this stimulus, the 

 nerve impulses aroused by localized stimulation of fibres, which are exposed in the 

 section, are entirely confined to the particular column excited. This is true, whether 

 the stimulus be central or peripheral to the observed region, that is, whether the 

 impulses are ascending or descending. 



III. If the stimulus be maximal, then a greatly reduced effect is still obtained, in 

 spite of the interruption. This effect is due to nerve impulses, which must at some 

 period be conducted along indirect fibres outside the excited column. Its average 

 amount varies in the different columns. These amounts may be arranged in series as 

 shown in the following table, in which the nature of the excitation and of the inter 

 ruption is noted, and the average effect evoked by maximal stimulation is given. 



Character of 

 impulses. 



Column excited. 



Column interrupted. 



Effect. 



Ascending 



Descending . 



Ascending 

 Descending . 



Ascending 



Lumbar end of cut posterior 



tenor 



| Dorsal end of cut posteric 



(^Dorsal end of cut lateral . 



Lumbar end of cut posterior 

 ( Dorsal end of cut posterior 

 ^ Dorsal end of cut lateral . 



Lumbar end of cut lateral . 



Section of same posterior 



Section of both posteriors 



Hemisection same side 



Section of both posteriors and lateral 



of opposite side 



Section of same posterior 



Section of both posteriors and opposite 



lateral 



Hemisection same side 



Hemisection same side 



Section of both posteriors and lateral 



of same side 



Ditto 



Section of both posteriors and lateral of 



same side 



Hemisectiou same side 



Hemisection same side and section of 



posterior of opposite side 



Section of lateral same side 



52 

 46 



44 



40 

 35 



32 

 29 

 23 



19 

 16 



11 









 



