26 MATHILDE M. LANGE 
c. The nervous system. Up to the present no histological 
study of nerve regeneration in Mollusca has been published. 
Techow refrained from doing so on account of technical diffi- 
culties. Hanko states that the nerves which innervate the 
eye of Nassa mutabilis regenerate, but does not state how. 
He refers to a paper by M. Kiipfer which was in preparation 
when his own was published. I tried to obtain this paper, but 
as it has not yet been published, I was unable to see it. Nerve 
regeneration in worms has been studied by Lehnert, Bardeen 
(04), Hescheler, Lang, Flexner (’98), Schultz, and Stevens. The 
two first authors claim that the new nerve fibers simply grow 
out of the old. Lang, Flexner, Schultz, and Stevens found that 
the new brain is formed by parenchym cells. The regeneration 
of the nervous system of vertebrates has often been made the 
subject of histological study. Experiments were made chiefly 
on the spinal cord of tritons and lizards, in some cases on the 
spinal cord and also on the brain of birds (pigeons) and mammals 
(rabbits and dogs). Dentan (73), Eichhorst (’75), Naunyn 
(74), Keresztzsegy (92), and Hanns (’92) could not find any 
regeneration in the central nervous system of vertebrates. 
Strébe (’94) claims that the injured spinal cord of the rabbit 
makes an effort to repair the damage, but that an actual regen- 
eration does not take place. Contrary to this, Walter (753), 
Cattani (85), Brown-Sequard (’50), Miiller (’64—65), Masius (’70), 
and van Lair (’70), Caproso (’88), all claim that the central 
nervous system is able to regenerate. Tedeschi (97) found 
regenerated ganglion cells and nerve fibers in the brain of mam- 
mals. There is quite some diversity of opinion on the manner 
in which the nerve cells multiply. Walter, Cattani, Modino 
(85), Friedmann (’88), Ziegler (95), Coen (’88), Sanarelli (’96), 
Marinescu (’94), and Tedeschi, all claim that the nerve cells 
multiply by means of mitosis. Caproso and Barfurth, on the 
other hand, believe that the new nerve cells are evolved from 
neuroblasts, which originate in the epithelium of the central 
canal. Mihlmann (’08, ’10), who has made the structure and 
growth of the nerve cell an object of special study, is of the 
opinion that already at an early stage of its development certain 
