440 MESSRS. F. GOTCH AND V. HORSLEY 



cord when the sciatic nerve is excited. This is shown by the fact that the cord effect 

 is in no way modified by an interruption in the anterior columns which involves their 

 complete severance, caused by a section between the entering nerve and the observed 

 region. Such a section is most easily made in the isolated fragment of cord near 

 its central attachment, since this portion is raised from its bed. This is in strict 

 accordance with the fact alluded to in Chapter VIII., that excitation of the one end 

 of the anterior column evokes no electrical effects in a distant portion of the cord. 



It is otherwise with the lateral columns which have distinct relations with 

 electrical effects in the cord, since, as shown in Chapter VIII., their stimulation 

 evokes marked cord effects. It does not follow, however, that this relation is one 

 which comprises the afferent nerves, for we know that the lateral column contains the 

 main path for the efferent cord tracts, as is shown by the results of cortical excitation, 

 as set forth in Chapter V., &c. The conclusion at which so many observers have 

 arrived, that the main afferent path, whether crossed or uncrossed, is situated in the 

 lateral column, is clearly not substantiated by any evidence offered by the employment 

 of the present method, since the integrity of the two posterior columns is evidently 

 essential for the production of at least 70 per cent, of the total effect. We shall see 

 that the extent to which the two lateral columns are related to the afferent effect is 

 small, being approximately only a fourth part of this amount, and that this is almost 

 entirely confined to the lateral column on the same side as the afferent nerves excited. 

 The results may be best displayed as follows : - 



A. Effect of Section of the Lateral Column on the same side as the Nerve Excited. 



\ 



The following experiments ma,de upon four Cats show that the lateral column of 

 the same side as the excited nerve, if divided, reduces the cord electrical effect evoked 

 by excitation of the nerve to an extent the average of which is 20 per cent., that is, 

 from 100 to 80. 



