320 REPORT—1846. 
nevertheless still retain their essential characters as divisions of a single ver- 
tebral element: just as does the vomer in the salamanders, salamandroid 
fishes and serpents, which begins to be developed from two lateral points, 
like the body of the human atlas occasionally, without the development end- 
ing, as it always does in such atlas, by confluence of the resulting halves. It 
would be more reasonable to repudiate the general homology of the body of 
a whale’s dorsal vertebra with the centrum of the typical vertebra, because 
it consists of three pieces set end to end, than to deny the general homology 
of the vomer because it may consist of two pieces set side by side, or that 
of the anterior trunk-vertebrz of the silurus because they consist of two 
pieces set one upon the other. These are examples of a principle of varia- 
tion which Cuvier never permitted to blind his perception of the special ho- 
mology of certain bones, the mandibular ramus, for example ; though vege- 
tative or teleological subdivision is carried out to a much greater extreme 
there than in any vertebral centrum; unless, indeed, the number of points 
from which the whale’s vomer be ossified may equal those in the crocodile’s 
lower jaw. But if the differences in this developmental character, viz. of ossi- 
fication from a single ossifie point as in the vomer of the cod, or from two 
points as in that of the lepidosteus, or from three or more points as in the 
human vomer, interpose no obstacle to the determination of the special homo- 
logy of the bone 13 from man to fish, it can as little avail as an argument 
against its general homology, which is determined not by the development of 
the vomer but by its relations to the other constituents of the segment of the 
skeleton to which it naturally belongs. ‘ 
The great difficulty which the anthropotomist may naturally experience in 
forming an idea of the vomer as the body of a vertebra, will arise from ‘its 
extremely modified form in the human subject: but he must bear in mind 
that it is an extreme part, the last of its series counted forwards; and if he 
should desire some higher and better established authority than the present 
Report before yielding assent to the vertebral character of the bone, under 
its characteristic ‘ ploughshare’ mask in man, I know no name more influen- 
tial than that of Cuvier himself, in regard to the equally and similarly modi- 
fied centrum at the opposite end of the vertebral series in the bird. For 
although the mask of coalescence is superadded to that of strangeness of 
shape in the bone which Cuvier there compares to a ploughshare [ vomer, or 
‘soe de charrue’ ], the great anatomist and cautious generalizer does not hesi- 
tate to affirm that it is “ composed of many vertebre ” (see ante, p. 263). 
It may, perhaps, be said that the coccygeal vomer must be vertebral in its 
nature because it is situated in the tail; but the ‘ petitio principii’ in this 
argument will be transparent, if we transpose the locality, and say that ‘the 
cranial vomer must be vertebral in its nature because it is placed in the 
head.’ For what are ‘head,’ ‘tail,’ ‘ thorax,’ or ‘ pelvis,’ but so many di- 
versely modified portions of a great segmental whole? These localities do not 
determine the nature of the segments composing them ; such knowledge can 
only be acquired by a study of the composition of the segments ; andit is the 
modifications of the segments that determine the nature of the localities or 
divisions of the endoskeleton, to which such special names as ‘ head,’ ‘ tho- 
rax,’ &c. are applied. 
Yet Cuvier himself, perhaps, little suspected how much his ideas of the 
essential nature of a segment of the endoskeleton were governed by the part 
of the body in which it happened to be placed. Whenever the young ana- 
tomist finds a difficulty from the peculiar form or development, division 
or coalescence, of a cranial bone, in recognising or admitting its vertebral 
ce a 
