OSSEOUS SYSTEM. (Comp. Anat.) 
in Man to a most rudimentary condition, 
being represented merely by the common 
cuticular 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 oftice 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 
phigher Vertebrata, examine that of a fish, 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 
Eeeiaber 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 
berrant in its composition from what is seen in 
‘any other class of Vertebrate animals. In the 
irst place there are numerous bones forming 
a chain of osseous plates surrounding the 
ferior margin of the orbital cavity, which have 
been named by Cuvier “ suborbital bones,” and 
by Geoffroy “ jugal bones,” although, having 
ready seen that the jugal are represented 
elsewhere by an important element easily iden- 
fied, it is surely anomalous, to say the least of 1%, 
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 
eir very office are evidently peculiar to the 
skeleton of a fish, and could scarcely have been 
Spected to have any analogue in animals 
tally destitute of gill openings, as are all other 
Vertebrata in their adult condition. These 
‘bones are four in number, and have received 
from writers onichthyology the following names: 
St, the preoperculum,* (fig. 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 
hike a door on its hinge. Beneath the last- 
ed bone is a third, named the sub- 
* 
4 
Tympanal bone (Geotfroy). Malleus (Spix). 
Stapeal (Geoffroy). Incus (Spix). 
6 ¥. « 
A Oe 
845 
operculum,* (fig. 436) 32) and still lower down 
placed immediately behind the articulation of 
the lower jaw, a fourth, to which the name of 
interoperculum+ (fig. 436, 33) has been ap- 
lied. 
i 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. Hilaire, that these opercular 
bones are the ossicula audités 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 Lepidusterus, 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 sub-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- 
preryeiis or many-jointed, as in the fin rays of 
alacopterygious fishes. These moreover are 
individually articulated with other pieces of a 
more decidedly osseous character, called 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 vertebra. 
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 vertebra of the fish when they have become 
largely developed ‘themselves, give origin to 
new bones and afford us an illustration of a 
* Malleal ( Geoffroy). 
t Inceal (Geoffroy). Stapes (Spix). 
