92 PROCEEDINGS OF SOCIETIES. 
of a “cell,” showing the course of afew of the most important of 
these lines which traverse its substance, is given. 
I do not conceive that these lines represent fibres structurally 
distinct from one another, but I consider the appearance is due to 
some difference in composition of the material forming the sub- 
stance of the cell in these particular lines; and it seems to me 
that the course which the lines take permits of but one explana- 
tion of the appearance. Supposing nerve-currents to be passing 
along the fibres through the substance of the cell, they would 
follow the exact lines here represented; and it must be noticed 
that these lines are more distinct and more numerous in fully- 
formed than in young cells. They are, I think, lines which result 
from the frequent passage of nerve-currents in these definite 
directions. 
Now I have already advanced arguments in favour of the 
existence of complete nervous circuits, based upon new facts re- 
sulting from observations upon a, the peripheral arrangements of 
the nerves in various tissues ;* 6, the course of individual fibres in 
compound trunks, and the mode of branching and division of 
nerve-fibres ; + and ¢, the structure of ganglion-cells.t I venture 
Fig. 3. 
~ 
_ Diagram to show the possible relation to one another of the various 
circuits traversing a single caudate nerve-cell. a may be a circuit con- 
necting a peripheral sensitive surface with the cell ; 4 may be the path of a 
motor impulse ; ¢ and d other circuits passing to other ¢ells or other peri- 
pheral parts. A current passing along the fibre a might induce currents 
in the other three fibres, J, c, d, which traverse the same cell. 
* Papers in the ‘Phil. Trans.’ for 1860 and 1862. “Lectures on the 
Structure of the Tissues, at the College of Physicians, 1860.” 
tt “ On very fine Nerve-fibres, and on ‘i'runks composed of very fine 
Fibres alone,” ‘Archives of Medicine,’ vol. iv, p- 19. “On the Branching 
of Nerve-trunks, and of the subdivision of the individual fibres composing 
them,” ‘ Archives,’ vol. iv, p. 127. 
t ‘Lectures at the College of Physicians.’ Papers in ‘ Phil. Trans.’ for 
1862 and 1863. 
