646 A. Ff. Goldfarb 
problem in mind. ‘Their conclusion, though based on very incom- 
plete data, as will be later shown, is however correct. 
It is the purpose of this paper to bring together a number of 
experiments bearing on the relation of the nervous system in the 
regeneration of adult animals, to find out whether it exerts any 
direct or indirect influence upon the regenerated organ or upon 
the process of regeneration, and to determine whether its absence 
is any more potent a factor in disturbing the normal develop- 
mental processes than any one other tissue, such as muscle, bone, 
etc. The following animals were studied: (1) Diemyctylus viri- 
descens (newt), (2) Frog tadpoles (advanced stage), (3) Lum- 
bricus, (4) Asterias vulgaris, (5) Dendroccelum lacteum. 
REGENERATION IN THE NEWT (DIEMYCTYLUS VIRIDESCENS) 
Newts and salamanders of various kinds have furnished the | 
most common material for experiments intended to show the 
relation of the central nervous system to morphogenesis. Unfor- 
tunately these experiments, with possibly one or two exceptions, 
fail to make clear the exact nature and extent of the injury to the 
nervous system. We do not know whether some or all of the 
nerve cells or fibers supplying the amputated region were destroyed, 
or whether subsequent changes may not have permitted innerva- 
tion of this region. Any conclusions based upon such insufh- 
cient data are of doubtful character. 
Diemyctylus shows a remarkably well-developed power of 
regeneration. Legs, tail and lens of the eye are replaced readily. 
In these studies the regeneration of the limbs and tail only will 
be dealt with, and, for the sake of clearness, will be treated sepa- 
rately. 
Regeneration of the Leg after Different Injuries to its Nerve 
Supply 
The hind legs are supplied by three pairs of nerves that take 
their origin in the lumbo-sacral plexus, Fig. 1. The anterior two 
pairs are considerably thicker than any of the adjoining spinal 
