482 MESSRS. F. GOTCH AND V. HORSLEY 



A. Spinal ganglion. 



B. Jugular ganglion of vagus. 



C. Spinal cord nerve centres. 



D. Channels of communication. 



A. Owing to the fact that the spinal ganglion has been made the object of some 

 important experimental observations we think it better to state these first, although 

 they are not, in our opinion, to be placed on the same ground as the phenomena 

 relating to the spinal nerve centres. 



This latter position is justified on consideration of the anatomical structure of a 

 spinal ganglion previously given, which shows that it is traversed by " through " 

 protoplasmic channels. 



(a.) Transmission of the Excitatory .Electrical Change. 



Du BOIS-REYMOND observed"" that when excitation was applied on the proximal side 

 of a spinal ganglion the " negative variation " was observable in the nerve trunk on 

 the distal side. 



(b.) Delay in the Transmission of a Nerve Impulse through a Spinal Ganglion. 



ExNERt considered that his observations on a spinal ganglion in the Frog, warranted 

 the opinion that the delay in the transmission of the excitatory condition (negative 

 variation) through a ganglion was the same as would be produced by its passage along 

 a nerve fibre ; that, in short, there was no special delay. As these observations were 

 made with BERNSTEIN'S differential Rheotome, we agree with GAD that they may be 

 possibly conditioned by summation. 



(c.) Trophism. 



As is well known since WALLER'S^ classical experiments, the ganglion exercises a 

 trophic influence on the afferent nerve channels running in the posterior root. 



B. Before passing to the observations on the spinal cord nerve centres, we must 

 specially allude to the valuable work by GAD and JOSEPH|| on the subject of delay in a 

 ganglion. The ganglion they chose was not a spinal ganglion, but its homologue, the 

 jugular ganglion of the vagus in the Rabbit. By recording the instant of change in the 

 respiratory movements when the vagus was excited, respectively on the proximal and 



* ' Untersuchungen Uber thierische Elektricitat,' 1849, vol. 2, 5, 601. 



f ' Archiv fur Anatomie und Physiologie. Phys. Abth.,' 1877, p. 567. 



J ' Comptes Rendns de 1'Academie des Sciences,' 1851, &c. 



Excepting the fibres described by MAX JOSEPH. 



|| ' Archiv fur Anatomie u. Physiologie,' Da Bois-RETMOND, 1888. 



