MORPHOLOGICAL STUDIES. 
199 
Y. The Neural Ridge. 
The reader may have remarked in the preceding pages that 
the terms neural ridge and neural crest have been banished 
from my account of the development of the ganglia, both 
cranial and spinal. The reasons for this may now be explained, 
and hand in hand with this explanation one may compare the 
origin of the ganglionic Anlagen as described here with the 
accounts of previous observers. 
Considering for a moment the neural ridge without prejudice 
as to its origin, most authors, following Marshall (No. 46, p. 15), 
regard the neural ridge as a continuous structure passing for- 
wards from the mid-brain right away backwards through the 
head and along the whole spinal cord as a continuous struc- 
ture ; and from its continuity in all parts, of which in a certain 
sense there can be no doubt, Balfour and Marshall were in- 
clined to attach great morphological importance to it. The 
continuity of the neural ridge is originally most marked in the 
head, in which the ganglia show tendencies to concentration and 
fusion, and where also the ganglionic Anlagen are very large. 
In the spinal cord, on the other hand, where the ganglionic 
Anlagen are not so massive, the continuity of the neural ridge 
is by no means so evident as in the brain. Indeed, from the 
neural-ridge stage onwards, aud even from the very first forma- 
tion of the spinal ganglia Anlagen, the segmental nature of 
the latter is one about which a careful investigator can make 
no mistake. For this reason, and the additional one that all 
the cell elements of the neural ridge in both head and trunk 
undoubtedly, as His insists (No. 34, p. 393), pass over into the 
ganglia, I can sec no particular advantage in the use of the 
term. And when one comes to consider, as we shall presently 
do, the origin of the neural crest, my objections to the term 
as at present used are intensified. Marshall, from the ap- 
parent fusion of the neural ridges of the two sides, gave to 
the single structure thus formed the name of neural crest. 
Ilcre, again, as the structure is certainly a bilateral one and 
not unpaired, and as in many cases its bilateral structure is 
