132 
ORIGINAL ARTICLES. 
very different senses, the former being that which it tends to encircle, 
and the latter the line from which its efforts to encircle the former 
begin. Thus, where there is least development of the visceral cavity, 
there is most tendency to radiation round the vertebral column. 
Hence the attachment of the lateral intermuscular septum of fishes, 
and the bones contained in it, to the ribs in front, nearer the vertebral 
column further back, and to the sides of the bodies of the vertebrae 
behind; and hence, also, the so frequent connexion-by-series of 
transverse processes in the fore part of the trunk with several sets of 
processes behind. 
When the visceral cavity has entirely disappeared, caudal relations 
become fully established, and then the inferior arches correspond 
more closely to the neural arches of their own vertebrse than to the 
visceral arches of the trunk vertebrae. 
The correspondence which inferior arches exhibit to one another 
in the various classes of vertebrata is greater than the differences 
which they present in respect of attachment, or of the structures 
with which they are in series. 
Transverse processes or ribs tending to surround the visceral 
cavity may be attached to various parts of the vertebra©, but never¬ 
theless have a primary correspondence to one another. 
Structures which surround the visceral cavity, such as ribs and 
the processes supporting their heads and tubercles, are more closely 
allied to one another than to structures projecting into the muscles, 
such as the superior transverse processes and ribs of fishes. 
IX.— Note on an Abnormality in the Ossification of the 
Parietal Bones in the Human Foetus. By Bamsay H. 
Traquair, M.D. 
Some time ago I dissected the head of a human foetus of between 
eight and nine months, in which the parietal bones j^esented a 
condition apparently at variance with the well known rule that these 
bones are two in number, and each developed from a single ossific 
centre. 
In this cranium the parietal bone of the left side is perfectly 
normal, being ossified from one centre which corresponds with the 
well marked parietal eminence. 
On the right side, however, the part which represents the 
parietal bone is divided into two distinct pieces, in a line extending 
from the middle of its posterior margin obliquely forwards to a little 
above its anterior-inferior angle. Of these two pieces, each of 
which is of course ossified from its own centre, the lower is accord¬ 
ingly somewhat triangular, and is equal in size to one-half the upper 
rudely quadrangular part: and the two pieces form together a double 
