OSSEOUS SYSTEM. (Comp. Anat.) 
Fig. 437. \ 
827 
Wt iy 
Wi Mit? 42 
Hyoid apparatus and branchiostegous rays of Perch ( after Cuvier ). 
‘proper to examine how far it is entitled to be 
ooked upon as we have already stated it to be, 
as forming a continuation of the spinal column, 
and if so, to define the vertebree of which it 
consists. In the human cranium indeed this 
would be no easy task, partly in consequence 
of the extreme exaggeration of every element 
composing it, and partly from the manner in 
which some bones, distinct in the lower animals, 
are here consolidated into single masses ; more- 
over in consequence of the prodigious develope- 
ment of the cerebral hemispheres every partis dis- 
torted and pushed aside as it were out of its pro- 
per situation relative to the neighbouring bones. 
In the cranium of the Reptile, however, and 
even of the less intelligent Mammalia, these 
difficulties are to a great extent done away with, 
and the vertebral form is preserved, while, in 
addition, the elements composing them fre- 
quently remain permanently disunited. 
The first cranial vertebra (commencing from 
behind) is the occipital, and this can present 
no difficulty. In Fishes, indeed, and in many 
Reptiles, the occipital bone, of which this ver- 
tebra is entirely made up, has not only the 
exact shape of one of the spinal bones, but the 
elements composing it remaining often perma- 
nently disunited, they are most easily and 
Satisfactorily identified. Inferiorly there is the 
body (or basilar bone, 5) connected with the 
body of the first spinal vertebra in the same 
Manner as the corresponding portion of the 
other vertebra are connected with each other. 
On each side the neurapophyses (or extra-occi- 
pital bones, 10.) arching over the commence- 
ment of the spinal cord, and lastly, the neuro- 
Spine (or supra-occipital bone, 8) oceupying its 
normal situation, and in many of the lower 
Vertebrata forming a real spinous process, 
although in the human subject, owing to the 
prodigious size of the hinder part of the ence- 
phalon, it is enormously spread out in propor- 
tion to the dimensions of the parts it protects. 
The second or parietal vertebra of the cra- 
nium is slightly more distorted, and its real 
nature masked, particularly in the higher Ver- 
tebrata, by the interposition of the petro-tem- 
poral bone, which does not normally belong 
to the cranium, between it and the preceding. 
Its body is the sphenoid bone, represented in 
the human subject by the posterior part of the 
sella Turcica, but which in Reptiles is a dis- 
tinct element of the skull; its arches are 
formed by the ale majores of the sphenoid, 
(likewise separate pieces of the cranium in the 
lower animals, although in man they are con- 
solidated with the former,) while the spine is 
converted into the expanded parietal bone or 
bones spread out over the central regions of 
the brain. 
The anterior cranial vertebra is called the 
Jrontal, receding still more from the normal 
appearance of a vertebra than the parietal, the 
preponderance of magnitude in the different 
elements that form it being completely in- 
verted; the body being quite rudimentary, 
while the enormously developed spinous ele- 
ments are now converted into frontal bones. 
In man its body and its arches are represented 
by the ale minores of the sphenoid or ingrassial 
bones, and the os frontis constitutes its dispro- 
portionately expanded spine. These three 
vertebrae, therefore, are the essential consti- 
tuents of the skull; and, although in the hu- 
man cranium the most aberrant of any met 
with in creation, their nature is not at once 
