144 ANATOMY OF VERTEBRATES. 



scapula to the pelvis, we give up our search in that direction ; 

 and in the opposite direction we find no vertebra without its ribs, 

 until we reach the occiput ; there we have centrum and neural 

 arch, with connate parapophyses, but without the haemal arch, 

 which arch can only be supplied by a restoration of the bones 

 50-52 to the place which they naturally occupy in the skeleton of 

 the fish. And since the bones 50-52 in the Crocodile, fig. 57, are 

 specially homologous with those so numbered in the Fish, fig. 34, 

 we must conclude that they are likewise homologous in a 

 higher sense ; that in the Fish the scapula-coracoid arch is in its 

 natural or typical position, whereas in the Crocodile it has been 

 displaced for a special purpose. Thus, agreeably with a general 

 principle, we perceive that, as the lower vertebrate animal illus- 

 trates the closer adhesion to the archetype 1 by the natural articu- 

 lation of the scapulo-coracoid arch to the occiput, so the higher 

 vertebrate manifests the superior influence of the antagonizing 

 power of adaptive modification by the removal of that arch from 

 its proper segment. 



The anthropotomist, by his mode of counting and defining the 

 dorsal vertebra? and ribs, admits, unconsciously perhaps, the 

 important principle in general homology which is here exemplified ; 

 and which, pursued to its legitimate consequences, and further 

 applied, demonstrates that the suprascapula and scapula are the 

 modified rib of that centrum and neural arch, which he calls the 

 * occipital bone ; ' and that the change of place which chiefly masks 

 that relation (for a very elementary acquaintance with Compara- 

 tive Anatomy shows how T little mere form and proportion affect 

 the homological characters of bones), differs only in extent, and 

 not in kind, from the modification which makes a minor amount 

 of comparative observation requisite, in order to determine the 

 relation of the shifted dorsal rib to its proper centrum in the 

 human skeleton. 



With reference, therefore, to the occipital vertebra of the Cro- 

 codile, if the comparatively well-developed and permanently 

 distinct ribs of all the cervical vertebra? prove the scapular arch 

 to belong to none of those segments, 2 and if that hamial arch be 

 required to complete the occipital segment, which it actually does 

 complete in fishes, then the same conclusion must apply to the 

 same arch in other animals, up to man himself. 



1 The term ' simple primary form ' appears to Dr. Humphrey, clxxi, p. 34, to 

 be more correct than the word ' archetype.' 



2 Close the eyes to the fact of the suprascapular element in the Crocodile, and you 

 then may, with Dr. Humphrey, see its representative in one of the cervical pleur- 

 apophyses. Comp. ib. p. 28, and note, p. 144, of the present work. 



