OSSEOYS SYSTEM. (Comp. Anat.) 
Fig. 434. 
Skull of the Perch ( Perca fluviatilis ), after Cuvier. 
an association of several osseous pieces, certain 
elements of a vertebra may be modified in 
Position and proportions so as to perform the 
ordinary functions of others which may be 
atrophied or absent : thus in Fishes the inferior 
transverse processes are gradually bent down- 
wards until in the dorsal region their extremities 
meet and perform the functions of the hema- 
pophyses. 
From the vertebral elements named above 
every possible variety is presented by these bones 
throughout all the races of animals possessing 
them. The body alone (fig. 433, d) may be de- 
veloped without the addition of any of the other 
parts, as in the terminal bones of a Mammal’s 
Fig. 
Ran nee ae 
ase of skull and opercular bones of Perch. 
825 
tail or of the human os coccygis, or the neura- 
pophyses may exist without an ossified body, as 
in some cartilaginous Fishes. The vertebre of 
the human skeleton present body, neurapophy- 
ses, neural spine, and transverse processes, as do 
the rib-bearing vertebre of the Fish. The 
caudal vertebre of the Fish, in order to give the 
great vertical expansion required in this region 
of their skeleton, have the centre, the neura- 
pophyses, and neural spine as well as the 
hemapophyses and hemal spine to the ex-. 
clusion of the transverse, while in the earlier 
caudal vertebre of the tail of the Crocodile 
(fig. 433, g ) all the elements enumerated exist 
in a medium state of developement. 
From these data, therefore, the osteologist 
is enabled to explain the composition of any 
vertebra that may be offered to his inspection ; 
nevertheless there are. numerous apparent ex- 
ceptions which are well calculated to puzzle the 
student, met with, especially in the vertebra of 
Serpents or of the neck of some Birds, where the 
processes are so complicated by the bifurcation of 
their extremities, or by foramina passing through 
their roots, or the great size of the articulating 
processes, or lastly, by the exuberant deposition 
of osseous matter in particular parts of the 
bone, that the greatest possible distortion may 
easily be h gem without at all violating the 
prescribed laws in accordance with which the 
osseous system is organized. Not unfrequently 
indeed stunted ribs, or even derivations from 
the exoskeleton, may become consolidated with 
the proper vertebral elements in such a manner 
as not to be readily distinguishable from them, 
producing additional complications which are 
sometimes very embarrassing. 
Skull—The osseous framework of the head 
appended to the anterior termination of the 
spinal column is by far the most complex part 
of the skeleton, being composed of very nume- 
rous bones connected together by suture or 
otherwise, but differing marvellously in their 
435. 
