ON THE VERTEBRATE SKELETON. 321 



character, let him compare the results of his own observations with those 

 summed up in pp. 264-266, and see whether the same kind of modification 

 may not be repeated in the homologous element of a vertebra of the trunk 

 in one or other of the species of vertebrate animals. 



The latest direct objection to the cranio-vertebral system is from the pen 

 of the celebrated ichthyotomist of Neuchatel. M. Agassiz represents the 

 current ideas respecting this system at the period when he published his 

 objections to it, in the following graphic passage of his invaluable and 

 splendid work: — " It was M. Oken who had printed the first programme on 

 the signification of the bones of the skull. The new doctrine which he set forth 

 was received with extreme enthusiasm in Germany by the school of physio- 

 philosophers [Natur-philosopher]. The author at that time required three 

 cranial vertebra?, and the basioccipital, the sphenoid and the ethmoid were 

 viewed as the central parts of these cranial vertebrae. Upon these pretended 

 bodies of vertebra? were raised the arches enveloping the central parts of the 

 nervous system (our 'protective plates') ; whilst to the opposite side were at- 

 tached the inferior pieces which should form the vegetative arch destined to 

 embrace the intestinal canal and the great vessel (the ' facial arches ' of which 

 we shall presently speak). It would be tedious to enumerate here the changes 

 which each author has rung upon this theme in modifying it agreeably with 

 his notions. These contented themselves with the number admitted by Oken; 

 those raised the number of cranial vertebrae to four, six, seven, or even more : 

 some saw nothing but ribs in the branchial arches and jaws ; others took the 

 latter for limbs of the head, analogous to arms and legs. If they could not 

 agree about the number of the vertebrae, still less were they at one in regard 

 to the part assigned to each bone. The most bizarre nomenclatures have 

 been proposed by different authors who thus sought to generalize their 

 ideas. Some have gone so far as to pretend that the vertebrae of the head 

 were as complete as the vertebrae of the trunk, and by means of dismember- 

 ments, with divers separations and combinations they have reduced all the 

 forms of skull to vertebrae, assuming that the number of pieces was in- 

 variable for every form of skull, and that all vertebrate animals, whatever 

 their definitive organization, bore, in their respective crania, the same number 

 of points of ossification *." 



And thus it is that a great truth in nature has been endeavoured, and 



* " C'est M. Oken qui fit imprimer le premier programme sur la signification des os du 

 crane. La nouvelle doctrine qu'il exposait fut accueillie en Allemagne avec un enthousiasme 

 extreme par l'ecole des philosophes de la nature. L'auteur postiilait alors trois vertebres 

 du crane, et l'occipital basilaire, le sphenoide et l'ethmoide etaient envisages comme les 

 parties centrales de ces vertebres craniennes. Sur ces pretendus corps de vertebres s'elevaient 

 des arcs enveloppant les parties centrales du systeme nerveux (nos plaques protectrices) ; 

 tandis que du cote oppose etaient attachees des pieces inferieures qui devaient former l'arc 

 vegetatif destine a. embrasser le canal intestinal et les gros vaisseaux (les arcs de la face dont 

 nous traiterons plus tard). II serait trop long d'enumerer ici les changements que chaque 

 auteur apporta a ce travail en le modifiant a sa maniere. Les uns se contenterent du nombre 

 admis par Oken, les autres eleverent le nombre des vertebres craniennes jusqu'a quatre, six, 

 sept et meme plus ; les uns voulurent voir des cotes dans les arcs branchiaux et les machoires ; 

 les autres prirent ces dernieres pour des membres de la tete, analogues aux bras et aux 

 jambes. Si Ton n'etait pas d'accord sur le nombre des vertebres on l'etait encore moins sur 

 le role qu'on assignait a chaque os. Les nomenclatures les plus bizarres ont ete proposees 

 par les differens auteurs, qui cherchaient ainsi a generaliser leurs idees. On alia jusqu'a 

 pretendre que les vertebres de la tete etaient aussi completes que les vertebres du tronc, et 

 au moyen de demembremens, de separations et de combinaisons diverses, on ramena toutes 

 les formes du crane a des vertebres, en admettant que le nombre des pieces etait invariable- 

 ment fixe pour toutes les tetes ; et que tous les vertebres, quelle que soit d'ailleurs leur 

 organisation definitive, portaient dans leur tete le meme nombre de points d'ossifications." 

 — -Recherches sur les Poissons Fossiles, t. i. (1843), p. 125. 



