30 M. L. Shorey 
‘The neural tube exhibits but little differentiation; no definite 
cell areas are marked off within it, and only a thin layer of nerve 
fibers or axones has formed at the periphery. There is a small 
ventral root, but the cells from which these axones arise have not 
yet become localized as the ventral horn. 
By operating at this stage of development it was possible to 
remove the greater part of the wing without any direct injury to 
the nervous system. As stated above, some structures, or parts of 
them, belonging to the wing may still develop, and the intrinsic 
muscles of the vertebral column are entirely uninjured; still the 
peripheral area, both sensory and motor, is much decreased, and 
as the greater part of the peripheral nervous system is still to be 
developed, and most of the differentiation of the spinal cord still 
to occur, it is possible to study the effect of the loss of the end organ 
on the size and distribution of the peripheral nerves, as well as its 
effect on the cells of the central system with which they are con- 
nected, either directly or indirectly. 
C Methods 
During the period of incubation preceding the operation the 
eggs were turned every 12 or 24 hours to prevent the blastoderm 
from adhering to the shell membrane, but to insure the accurate 
location of the embryo a number of hours must elapse between 
the last turning and the operation. The method of opening and 
closing the egg was essentially the same as that described by Lillie 
(703) and earlier by Miss Peebles (’98), but instead of placing 
strips of egg membrane about the edge of the shell used as a cover 
for the opening in the operated egg I found it more effective to 
leave a margin of membrane attached to this cover. If then the 
curvature of the cover is the same as that of the egg to which it is 
applied, and there 1s no break in the membrane, a perfect closure 
is effected. 
Since the embryo lies on the left side (I found only two or 
three exceptions to this in the fifteen hundred or two thousand 
eggs used in these experiments) the right wing was always the one 
removed. For this purpose small spear-headed scalpels were first 
used and this method may be used with success if the wing bud 
