372 SEA SIDE STUDIES. 



braiie behind.* Unimportant as this observation was, it 

 •was the starting-point of a long series of investigations. 

 Finding the contents of the ganglion were coloured, I in- 

 ferred that the coloured spots, irregularly distributed over 

 the upper portion of the nerve-trunks, and throughout the 

 bands connecting the ganglia into a collar, were also due to 

 ganglionic cells ; this being proved, it followed that the cells 

 and granules of the ganglion were not anatomically separable 

 from the cells and granules of the nerves ; instead of the 

 ganglion being a distinct structure from that of the nerve, 

 the two were identical, the only difference being that the 

 cells, both large and small, which predominated in the gan- 

 glion, became scarcer as the nerve was prolonged, and at 

 last only made their appearance by ones and twos, amid 

 the granular mass. 



Let us pause a moment to consider the theoretical diffi- 

 culty which is raised by such a fact. Hitherto all physi- 

 ologists have agreed in crediting the ganglion ■with the sole 

 production, and the nerve with the sole conduction of nerv- 

 ous force (whatever that may be). The ganglion has been 

 likened to a galvanic battery, the nerve to a conducting wire. 

 But if, as I affirm, the structure of the two be thus identical, 

 their function cannot be so different. In those animals pos- 

 sessing nerves and oranglia of a marked structural differ- 



* The error is jirobably owing to a goncralisatiou from tlie fact that in 

 many animals the pigment is distributed over the membrane. Leydiq {Ilisto- 

 lof/ie d. Mensch. u. d. Thiere, 1856, p. 50) confirms what I have said in the text : 

 " Dieso Pigmentirung ist diffuser Art, sie riihrt her von einer rothen Fllissig- 

 kcit, welcho das ganzo Ganglion durchtriinkt, uud nachdem des Nourilem 

 oiugcrisson ist, in Tropfeu heraus<iuillt." 



