OUTGROWTH OF THE NERVE FIBER 
829 
they would after a time degenerate as do those which develop 
sporadically in the ventricular fluid. It is quite true that the 
nerves which grow out into the lymph-clot do ultimately shrink 
and disintegrate, but it is purely gratuitous to assert that this is 
in consequence of their original mode of growth, when it is in all 
likelihood due to the effect of continued unfavorable surroundings 
upon their subsequent development. Held also intimates that 
the nerves grown in lymph are incapable of functioning, though no 
sufficient ground for this statement is offered. But when he 
says ''Die Beobachtungen Harrisons zeigen . . . mitwelcher 
Energie die neurofibrilldre Zellsubstanz aus der fihrillogenen Zone 
des Hisschen Neurohlasten hervorwdchst/^ and when he says further 
on ''Dass die fraglichen Experimente . . . die elementare 
Bedeutung der Hisschen Neurohlasten fiir die von ihnen herausge- 
hende und vorschreitende Bildung der spezifischen Substanz 
des Nervengewebes illustrieren, " then I can only express my 
cordial agreement, since in these sentences Held practically ad- 
mits all that I have ever claimed for the experiments, viz : that 
they show the nerve fibers to be the product of the neuroblasts, 
and to be capable of being formed without the aid of protoplasmic 
bridges. 
It would seem from the above that Held and myself were 
in pretty fair agreement regarding the question at issue, and 
I shall endeavor to show below just how our views are related, 
but it will be necessary first to consider the important difference 
that appears in the next following paragraph of Held's work, in 
which he maintains that the histogenetic study of the embryo shows 
more than the experiments, since it reveals the presence of a con- 
nective substance betw^een the individual cells and organs of the 
body, which is used in the formation of the definitive nerve paths. 
Held's sections are of exquisite beauty and show beyond doubt 
the structures he has described, but they fail on the other hand to 
prove that the same have any essential connection with the for- 
mation of the nerve paths. While it is true that the developing 
nerves seem to be very intimately joined with the protoplasmic 
bridges which Held describes, the very ubiquity of the latter in 
the embryonic body precludes the possibility of proving, b}^ the 
