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-vertebrae 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 ossific 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 

 'soc de cliarrue'], the great anatomist and cautious generalizer does not hesi- 

 tate to affirm that it is " composed of many vertebrae " (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 ; and it 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 



