FUNDAMENTAL PLAN OF VERTEBRATE BRAIN A475 
strengthened by examination of the shark (’77). Apparently 
the entire vertebrate body was thought of as formed by con- 
crescence in the midplane of right and left moieties, although by 
both word and figure he seems to have recognized a primitive 
continuity of material at the anterior end of the body axis. 
Inasmuch as the primitive line of junction established the neural 
plate externally and the chordal plate internally, His designated 
it as the ‘neurochordale Naht.’ This two-fold effect of concres- 
cence His recognized as early as 1874 and comments on in 1877, 
but the designation was not given until he turned his attention 
to the structural plan of the central nervous system. Gorono- 
witsch (’93) was apparently the first to give it technical form as 
the ‘sutura neurochordalis (ventralis),’ although he failed to 
erasp the significance of the term. 
Hertwig (92) gave a new significance to the neurochordal 
suture through his recognition that it marked the line of closure 
of the blastopore. 
The interpretations of His and of Hertwig and their bearing 
have been, I think, adequately discussed in my earlier paper 
(Kingsbury, ’20). It remains to examine more closely than was 
then attempted the value and significance of the term ‘neuro- 
chordal suture’ as applied to the brain. 
The neurochordal suture, according to His, becomes in the 
neural tube marked out by the floor plate and this—in accordance 
with his conception of the origin of the body—extended to the 
anterior end of the neural plate. The distinction of neurochordal 
suture and floor plate should of course be appreciated. The 
neurochordal suture is a structurally negative term; an ideal 
plane of junction. The floor plate is a structural differentiation. 
The term may be used either in a purely descriptive way or as 
a structure of ontogenetic significance. Reference to my earlier 
paper (p. 115) is indicated in this connection. 
The problem of the neurochordal suture may perhaps be stated 
in question form as follows: Does the floor plate mark in the 
neural plate (tube) the line of closure, either actual or potential, 
of the blastopore? Does the notochordal plate likewise coincide 
with the line of closure of the blastopore? If so, these two strue- 
