316 REPORT—1846. 
The new functions which the uplifted and independent spines of the pari- 
etal and frontal vertebrae perform in man and many mammals are, with 
respect to the parietal bones, to shield the upper surface of the middle and 
posterior parts of the cerebral hemispheres, whilst the frontal is confined to 
covering the anterior lobes of the same hemispheres. 
Hereupon it may be asked whether such relations and offices are the rule 
or only the exception; and, if the latter, whether it occurs in the lowest or 
the highest of the vertebrate series ; whether in that class where the arche- 
typal arrangement of parts is most, or in that in which it is least departed 
from? All these considerations are felt to be indispensable by the homo- 
logist in quest of the true signification of the parts of the animal frame, 
before drawing his conclusions from the first modification that may present 
itself. They are neglected by Cuvier in the objection to the vertebral cha- 
racter of Oken’s ‘kiefer-wirbel,’ founded upon the relations which the parietal 
bones present to the encephalon in the mammalian class. Yet the more 
normal relations of those bones, both to the encephalon and to the alisphe- 
noids, seem to have been present to the mind of Cuvier, and to have been 
duly appreciated by him when he defined, in 1817, the second cranial cine- 
ture as constituted by the parietals and sphenoid*. 
With regard then to the first of Cuvier’s arguments for viewing the human 
and mammalian parietals as ‘ des piéces particuliéres qui ont une destination 
particuliére,’ viz. that they are separated from the alisphenoids by the tem- 
poral bones. If we commence our consideration of it by the question, whether 
this separation be the rule or the exception, the reply which Nature sane- 
tions will be that they are not so separated in any of the three great classes of 
oviparous vertebrata, nor in the majority of mammalia, nor even, as a general 
rule, in man himself. With regard to the second objection founded on the 
interposition of the enormously and backwardly developed prosencephalon 
between the mesencephalic spines (fig. 25, 7) and the mesencephalic segment 
of the brain, to which the parietal vertebra essentially relates,—-its value will 
depend on the choice made by the homologist between the function of the 
parietals as immediate shields to the optic lobes (mesencephalon) in the cold- 
blooded classes, and their function as mediate ones through the interposed 
mass of the prosencephalon in the warm-blooded classes, as that which best 
manifests adhesion to the ideal archetype. What to me has ever appeared one 
of the most beautiful and marvellous instances of the harmony and simplicity 
of means by which the One great Cause of all organization has effected every 
requisite arrangement under every variety of development, is the fact, that 
the protection of the enormous cerebrum peculiar to the higher mammals 
has not been provided for by new bones: by bones, e. g. developed from 
centres so numerous or so situated as to render any determination of their 
homologies as vague and unsatisfactory as would result from the attempt to 
determine those of the dermal ossifications upon the head of the sturgeon, in 
reference to the endoskeletal epicranial bones in fishes and reptiles. We 
might well have expected, had conformity to type not been a recognizable 
principle in the scheme of organized beings, to have had so many ‘ particular 
bony pieces’ and so situated in the expanded human cranium as would have 
baffled all our endeavours to reduce them to the type of the epicranial bones 
of the reptile or fish. Yet the researches of the great comparative anatomists 
of the present century, and more especially those of Cuvier himself, have 
proved that there is no such difficulty: and a glance at the Table of Special 
Homologies, No. 1, will show that the bones (3, 7, 11) most modified in rela- 
tion to the expanded cerebrum and cerebellum of man and mammals are 
* Reégne Animal, i. p. 73. 
