ON THE VERTEBRATE SKELETON. 303 



opposites at the symphysis rnenti ; and the whole distal portion of the in\ erted 

 arch of the frontal segment is then formed by a continuous bar of bone, modi- 

 fied in its form and articulation, and by its dental appendages, in subserviency 

 to mastication and other subordinate functions in relation to the human mouth. 



We recognise the centrum of the nasal vertebra in the human skull by the 

 position and connections of the bone, 13, notwithstanding it has undergone 

 as extreme a divergence from the ordinary cylindrical shape of such elements, 

 as its homotype at the opposite extreme of the vertebral column in birds, 

 which Cuvier compares to a 'soc-de-charrue' : it is, in fact, more compressed 

 and vertically developed than in the hog (fig. 24, 13) ; but it is shorter, and 

 commonly retains its original individuality. It directly supports the similarly 

 modified compressed, and also, coalesced neurapophyses, 14, which termi- 

 nating in like manner the series of their vertebral homotypes anteriorly, have 

 undergone the extremest modification. But the arguments which show the 

 coalesced prefrontals of the frog, the bird and the mammal to be the special 

 homologues of the bones so called in the fish, establish, as a corollary, their 

 general homology with those bones, which retain in so much greater a degree, 

 and unmistakeably, their neurapophysial characters in that lowest class of 

 cold-blooded vertebrates. The nature of the additional complication by 

 which those vertebral or archetypal characters are further masked in mam- 

 mals, has been already explained in relation to the nasal neurapophyses of 

 the hog. The olfactory nerves are transmitted in man, as in that and most 

 other inferior mammals, by numerous foramina, 14, ol. The nasal spine, 15, is 

 divided, but much-restricted in its growth, and presents a singular contrast 

 in that respect to its homotypes, ] 1, 7, 3, in the succeeding cranial vertebrae. 

 The development of the neural arch of the nasal vertebra is so modified in 

 man, so contracted as well as retracted, that the orbits, instead of being 

 pushed apart and directed laterally, have approximated by a kind of reci- 

 procal rotation towards the median plane, and have thus gained a directly 

 anterior aspect. 



General homology perhaps best explains the import of the continuation 

 of the small and seemingly insignificant bones (20, pi) from the roof of the 

 mouth " up the back part of the nostrils to the orbit," where they are 

 connected "to the ossa plana and cellulce ethmoidece by the ethmoid suture." 

 That the connection is the best possible for the functions of the bone we 

 may feel assured, without the sentiment being damped by discerning in it, 

 at the same time, the attempt to retain the type, and repeat those constant con- 

 nections of the pleurapophysis in question, not only with its centrum (vomer), 

 but also with the modified neurapophyses of its proper segment (prefron- 

 tals with coalesced olfactory capsules constituting the compound ' ethmoid 

 bone' of anthropotomy). The connections of the pleurapophysis, 20, with its 

 hasmapophysis, 21, in front, and its diverging appendage, 24, behind, are also 

 retained in man ; and in short, all those characters that, depending on the 

 essential nature of the palatine bone as the pleurapophysis of its vertebral 

 segment, have served to indicate its special homology from man to the fish, 

 without doubt or difficulty, to all anatomists (see Table I.). 



The hxmapophysis (20) has the usual mammalian expansion, but is unu- 

 sually short in man, and coalesces unusually early with the corresponding 

 moiety of the hcemal spine (22). Besides the normal and constant connec- 

 tions with 20 and 22, the hsemapophysis, 21, articulates with its fellow, with 

 the centrum (13), neurapophysis (14, os planum), and spine (15), of its 

 own vertebra, with the spine of the frontal vertebra (11), with the detached 

 portion of the olfactory capsule (19), and with the muco-dermal bone (73). 

 It also affords a large surface of attachment to the proximal piece of 



