OSSEOUS SYSTEM. (Cowi-. ANAT.) 



845 



in Man to a most rudimentary condition, 

 being represented merely by the common 

 culicular covering of the body and its appen- 

 dages, the hair and the nails, we shall find 

 among the lower Vertebrata performing a much 

 more important part in the animal economy, 

 and occasionally entering largely into the 

 construction of the organs of locomotion, re- 

 placing and not unfrequently actually assuming 

 the appearance and office of the endo-skeleton 

 or proper osseous system. Examined in their 

 remotest aspects, few textures indeed appear 

 less allied, the osseous tissue and that of hairs, 

 horns, feathers, and other cutaneous appen- 

 dages ; nevertheless we doubt not that, on taking 

 an enlarged view of the subject, it will not be 

 difficult to prove that the two are absolutely 

 interconvertible, both in use and even com- 

 position, the cuticular skeleton being not unfre- 

 quently had recourse to by nature to eke out 

 and complete organs for the construction of 

 which the elements of the endo-skeleton would 

 have been insufficient. 



Let any one who is only conversant with the 

 composition of the skeleton of Man, or of the 

 higher Vertebrata, examine that of a tish, more 

 especially of one of the osseous Fishes, and he 

 will soon perceive how impossible it is to point 

 out anything analogous to a very considerable 

 number of the parts composing it, in the bony 

 framework even of those Reptiles that are most 

 nearly approximated to Fishes, in their general 

 economy, or from the elements above enu- 

 merated, various as they are, to build up those 

 additional structures that render the osseous 

 support of a fish's body so complicated and so 

 aberrant in its composition from what is seen in 

 any other class of Vertebrate animals. In the 

 first place there are numerous bones forming 

 a chain of osseous plates surrounding the 

 inferior margin of the orbital cavity, which have 

 been named by Cuvier " suborbital bones," and 

 by Geoffrey "jugal bones," although, having 

 already seen that the jugal are represented 

 elsewhere by an important element easily iden- 

 fied, it is surely anomalous, to say the least of it, 

 to find the same element thus multiplied and 

 divided, more especially when in many of the 

 hard-cheeked fishes, such as the Gurnard, these 

 supplementary pieces become the largest bones 

 of the face. 



The opercular bones, which form the gill 

 flaps of the fish, are a set of bones which from 

 their very office are evidently peculiar to the 

 skeleton of a fish, and could scarcely have been 

 suspected to have any analogue in animals 

 totally destitute of gill openings, as are all other 

 Vertebrata in their adult condition. These 

 bones are four in .number, and have received 

 from writers on ichthyology the following names : 

 1st, the preoperculum,* (Jig. 436, 30) which 

 forms the basis supporting the other three ; 

 2nd, the operculum-\ proper, (fig. 436, 28) 

 articulated to the former, on which it moves 

 like a door on its hinge. Beneath the last- 

 mentioned bone is a third, named the sub- 



operadum,* (fig. 436, 32) and still lower down 

 placed immediately behind the articulation of 

 the lower jaw, a fourth, to which the name of 

 interopcrctdiun^ (fg. 436, 33) has been ap- 

 plied. 



In the Chondropterygii this apparatus is 

 entirely wanting. To explain the analogies of 

 these pieces the most desperate theories have 

 been broached by transcendental osteologists, 

 the boldest and most celebrated of which is 

 that of Geoffroy St. ililaire, that these opercular 

 bones are the ossicula auditus reproduced in an 

 altered form after they were no longer required 

 to form part of the auditory organ ; an opinion 

 which has found supporters even in this 

 country notwithstanding the withering criticism 

 of Cuvier, who, remarking upon this theory, 

 very justly observes, that he has seen but little 

 of such sudden reappearances of parts after 

 they had been progressively made to disappear 

 in the scale of animal life. Cuvier was com- 

 pelled to regard the opercular bones as being 

 superadded elements of the skeleton peculiar to 

 Fishes, and having no representatives in other 

 Vertebrata. De Blainville suggested that the 

 pieces in question might be derived from a 

 dismemberment of the lower jaw, by the 

 detachment of the opercular elements from the 

 ramus; but this hypothesis is refuted by the 

 fact that in some Fishes, as the Lepidosterus, all 

 the elements of the inferior maxilla are co- 

 existent with the opercular apparatus. Pro- 

 fessor Owen first suggested that they were 

 mere derivations from the dermal skeleton, an 

 opinion that seems every day to receive con- 

 firmation. 



The supra-temporal bones of Fishes, a chain 

 nearly resembling the nub-orbital, which in 

 many species arches over the temporal fossa, 

 belong to the same category, and cannot be 

 said to resemble any bones found in other 

 creatures. 



But the most anomalous of all the bones 

 found in a fish's skeleton are those large and 

 important ones that support the azygos fins 

 placed along the mesian line of the body, con- 

 stituting the dorsal, caudal, and anal fins. 

 These bones consist of several distinct pieces, 

 and frequently assume a very complex struc- 

 ture : first, there is the fin ray itself, either 

 simple, as in the dorsal fins of the Acantho- 

 pterygii, or many-jointed, as in the fin rays of 

 Malacopterygious fishes. These moreover are 

 individually articulated with other pieces of a 

 more decidedly osseous character, cajled the 

 interspinous bones, which are imbedded in the 

 flesh of the back, and might be, as indeed 

 they have been, mistaken for appendages to the 

 neuro-spines of the vertebrae. 



The hypothesis promulgated by Professor 

 Grant upon this subject is as follows: "The 

 spinous processes in Fishes give rise to other 

 pieces. The spinous processes extending from 

 the vertebrae of the fish when they have become 

 largely developed themselves, give origin to 

 new bones and afford us an illustration of a 



6 Tympanal bone (GeoiFroy). Malleus (Spix). 

 f Stapeal (Geoffroy). Incus (Spix). 



1 Malleal (Geoffvoy). 



t Ineeitl (Geoffroy ). Stapes (Spix). 



