148 
ANATOMY OF THE HORSE. 
junction with the lachrymal and sphenoidal, and, by overlap¬ 
ping, with the ethmoidal bone. 
PARIETAL BONE. (oS PARIETALE.) 
Situation- On the superior and middle parts of the cra¬ 
nium. 
Figure. Symmetrical; quadrilateral ; vaulted : convex exter¬ 
nally, concave internally. 
Jjivision. Into two surfaces and four borders. 
The External or Convex Surface is divided longitudinally by a ' 
mesian cm/,which is bifurcated anteriorly and marks the course 
of the suture existing in early life, into two lateral convexities ; 
these are most elevated towards the supero-external angles, and 
their surfaces, though otherwise smooth, exhibit a few scattered 
small foraminse, and are imprinted by the continual action of the 
muscles covering them, the prints growing deeper with age 
and, it appears, the general prominence less. The triangular 
space between the bifurcations of the crest generally rises above 
the level of the surrounding surface. 
The Internal or Concave Surface is divided into two concavities 
by an internal crest which is commonly double, having a longi¬ 
tudinal groove in the middle: it is terminated posteriorly by a 
three-sided process, the parietal protuberance, to which, as w^ell 
as to the crest itself, is attached the falciform process of the 
dura mater. In front of this projection the longitudinal furrow 
ends in the two transverse grooves, which run along the poste¬ 
rior border, between it and the temporal bones : the former 
lodges the longitudinal, the latter the lateral sinuses of the dura 
mater. The cavities themselves are adapted to cover the mid¬ 
dle lobes of the cerebrum, by which they are indented ; they 
also show the traces of the ramifications of the arteries sup¬ 
plying the dura mater. 
Borders, Denticulated and squamous. The anterior is ser¬ 
pentine and unites with the frontal bones ; the posterior lies 
upon the occipital bone; and internally has two short bifid 
crests’growing from it, forming parts of the transverse grooves, 
from which it extends down, on either side, to the wing of the 
sphenoid bone; the lateral borders are irregular, and overlaid 
by the temporal bone. 
Development, In the foal, indeed generally until the second 
or third year, a longitudinal suture is demonstrable dividing 
this bone into two correspondent pieces. 
