NEUROBIOTAXIS ‘291 
We know, from the researches of Ambronn and Held® that 
myelin formation is greatly affected by the function of the tracts, 
and consequently strongly influenced by the stimuli passing 
through it. 
I have already referred to the fact that the genuine a ueinons 
substance and also the lecithin which forms the chief component 
of the myelin sheath generally exhibit, under normal circum- 
stances, an anodic kataphoresis. 
Concerning the myelin itself this has been experimentally 
shown by Hermann, who described its connection to the anode 
as ‘“‘eine der gewaltigsten microscopischen Erscheinungen,”’ 
he ever witnessed. 
Putting a part of a peripheral nerve of a frog in a constant 
current in the line connecting the electrodes (which, however, 
remained at a distance from its ends), he saw a vigorous outflow 
of the nerve content—especially the myelin—at the anodal 
pole of the nerve, where it collected in a mass. 
Reversing the current, this myelin could again be absorbed 
by the nerve and the myelin flowed out at the other (then, 
anodic) end. 
The tendency of the peripheral nerve constituents—chiefly 
its myelin—to move in the direction of the anode is clearly 
proved by this experiment.*! 
If now we apply this phenomenon to the structure of the axon 
in the central nervous system we may expect that the nerve 
current which has—as pointed out above—an anodal direction, 
will convey the lipoid substance, even that which is produced 
by the cell itself, chiefly in the axis-cylinder; but, since from this 
axis-cylinder an irradiation current of the same character flows 
out, the myelin is necessarily conveyed to the periphery of the 
nerve fiber. 
The difficulty consequently is not why only axis-cylinders 
have myelin and why this myelin is conveyed from the center 
50 Ambronn und Held. Ueber Entwicklung und Bedeutung des Nervenmarks. 
Sitzungsverichte der Kén. Sichsichen Gesellschaft der Wissenschaften, 1895. 
51 T am much indebted to Prof. Héber (Kiel) for calling my attention to Her- 
mann’s paper, which was unknown to me when | started to write this article. 
It is found in Pfliiger’s Archiv, Bd. 67, 1897, p. 240. 
