504 



MESSRS. F. GOTCH AND V. HORSLEY 



Since it was desirable to ascertain the relationship between the periodicity of the 

 electrical changes in the cord and that of the muscular twitches, the capillary electro 

 meter was used. 



The spinal cord of the Cat being divided in the mid-dorsal region, the upper end 

 of the dorso-lumbar portion was prepared for connection with the electrometer, whilst 

 the lower tendon of the rectus femoris muscle was cut and attached to one of FICK S 

 spring recording levers (isometric method). The cord was then exposed over the 

 dorso-lumbar junction and the lateral column excited with stimuli of varying degrees 

 of intensity. It is obvious that electrical changes thus produced in the cord are due 

 () to the excitation of continuous fibres joining the excited portion of the lateral 

 column with the observed region, (b) to the excitation of indirect fibres in the 

 lateral column, internuncial or otherwise, (c) to the discharge of nerve impulses 

 up the cord from the aroused centres. 



The main interest of the experiment lies in the fact that with a weak stimulus no 

 muscular effects were observed, although distinct electrical effects were produced ; 

 whilst with a strong stimulus the centres in the cord were so aroused that they 

 continued to discharge after the stimulus had ceased, these discharges being evidenced 

 both by muscular contractions and by effects in the electrometer. 



The following Table indicates this result : 



EXPERIMENT. Cat (104). Afferent Effect in Cord compared with Contraction of 

 the Muscle, simultaneously evoked by Intermediate Excitation of the Cord. 



It is thus seen that when a lumbar spinal centre is aroused to discharge, a flow of 

 nerve energy takes place up the cord as well as out by the efferent roots, and, in 

 all probability, impulses thus pass upwards to various groups of centres both in the 

 upper regions of the cord and in the encephalon. 



As to the spinal channels by which these impulses travel, whether internuncial, 

 direct efferent fibres (pyramidal tract) or direct afferent fibres (posterior column) the 

 experiment gives no information, and we have not had an opportunity of repeating it 

 on an animal in which, by previous operations, the two latter have been more or less 

 eliminated. Some evidence is afforded by the following experiment, in which the left 



