ON THE VERTEBRATE SKELETON. 337 



ligible to Cuvier. When Oken called the ' tympanic ' a ' cranial scapula ' he 

 unduly extended the meaning of the term ' scapula,' and converted it from a 

 specific to a generic one. The tympanic is the homotype of the scapula, 

 both being modified pleurapophyses, but each has an equal claim to its proper 

 or specific name indicative of their respective modifications. 



I am aware that Oken meant more than mere serial homology when he 

 called the tympanic the ' blade-bone of the head ': it is part of the phraseology 

 of the hypothesis of the head being a repetition of the whole body, &c. But 

 at the time when that anatomist wrote it was not known or suspected that 

 the head already possessed the scapula, and that the modified pleurapophysis 

 so called, actually appertained to a segment of the skull (fig. 5, so, 51). In 

 the terms 'femur capitis' ' tibia,' '■fibula! 'pes capitis,' applied by Oken to the 

 parts of the teleologically compound mandibular ramus, and in those of ' ulna ' 

 and ' mantis capitis,' applied to the distal segments (21, 22) of the maxillary 

 arch, we have not only instances of the attempt to express general relations of 

 repetition or homology by special terms, but these modes of expressing the 

 serial homologies of nos. 29, 30, 32, and of 21 and 22, betrays the misappre- 

 ciation of the general homologies of the locomotive extremities, and their 

 relations to the vertebral arches supporting them. 



To gain an insight into whatever proportion of truth may be involved in 

 the ideas signified by the phrases above cited, it is necessary to determine 

 the essential nature of the parts called ' femur,' ' tibia,' ' humerus,' ' ulna,' 

 ' manus,' ' pes,' &e., or the general homology, in short, of locomotive members, 

 and the attempt to master this problem has been not the least difficult part 

 of the present inquiry. Cuvier has offered no opinion, nor does be appear 

 to have ever troubled himself with the attempt to decipher the significa- 

 tion of the locomotive members of the vertebrate animals ; i. e. of what 

 parts of the primordial or pre-existing vertebrate model they are the 

 modifications. 



Oken's idea of the essential nature of the arms and legs is, that they are no 

 other than 'liberated ribs': " Freye Bewegungsorgane konnen nichts anderes 

 als frey gewordene Rippen seyn *." 



Carus, in his ingenious endeavours to gain a view of the primary homologies 

 of the locomotive members, sees in their several joints repetitions of vertebral 

 bodies (tertiar-wirbet) — vertebrae of the third degreef — aresultof an ultimate 

 analysis of a skeleton pushed to the extent of the term ' vertebra' being made 

 to signify little more than what an ordinary anatomist would call a ' bone.' 

 But these transcendental analyses sublimate all differences, and definite 

 knowledge of a part evaporates in such unwarrantable extension of the mean- 

 ing of terms. 



It has been, however, I trust, satisfactorily demonstrated that a vertebra 

 is a natural group of bones, that it may be recognised as a primary division 

 or segment of the endoskeleton, and that the parts of that group are definable 

 and recognizable under all their teleological modifications, their essential 

 relations and characters appearing through every adaptive mask. 



According to the definition of which a vertebra has seemed to me to be sus- 

 ceptible, we recognise the centrum, the neural arch, the haemal arch, and the 

 appendages diverging or radiating from the haemal arch. The centrum, 

 though the basis, is not less a part of a vertebra than are the neurapophyses, 

 hsemapophyses, pleurapophyses, &c. ; and each of these parts is a different 

 part from the other : to call all these parts ' vertebrae ' is in effect to deny 



* Lehrbuch der Natur Philosophic P- 330, 8vo, 1843. 

 f Urtheilen des Knochen und Schalengerilstes, fol. 1828. 



