OSSEOUS TISSUE. 
parts of the osseous system, of which we need 
only adduce as instances the fishing filaments 
upon the back of the head of Lophius, and the 
powerful weapons of Silurus and Balistes else- 
where described (vide Art. Pisces), where 
muscles are implanted into the spear-like arms 
here formed entirely from the cuticle, although 
brought into close union with the bones of the 
real skeleton. 
Having arrived thus far and found in the 
cases alluded to that epidermic spines, when 
thus far exaggerated in their dimensions, are 
really converted into fin-rays and moved by 
appropriate muscles, it is impossible to deny 
that such organs may have a similar origin in 
other parts of the skeleton, and that the rays of 
the azygos, dorsal, caudal, and anal fins, as well 
as the interspinous bones, which cannot be re- 
ferred toany known element of the endoskeleton, 
are in reality derivations from the exoskeleton, 
although implanted in the flesh and wielded 
by an appropriate system of cutaneous muscles. 
Even in their internal texture these pieces be- 
come assimilated to real bones, and that to such 
- anextent that it even yet remains for the minute 
_ anatomist and the microscopical observer to 
_ point out satisfactory differences between the 
_ two skeletons when they thus become blended 
_ together, notwithstanding the wide interval 
_ which separates the scale, the hair, or the fea- 
ther, all modifications of the epidermic system, 
from the tooth in its fully developed state, or 
from perfectly organized bone permeated by 
_ vessels and nourished by interstitial deposition. 
_ BrBLIoGRAPHY.—In addition to the authorities 
| quoted in the text the comparative osteologist is re- 
BD firred to the following sources of information. 
| Cuvier, Lecons d’anatomie comparée, 5 tom. 8vo. 
ann. VIII—XIV. - Cuvier, Recherches sur les 
ossemens fossiles, 5 tom. 4to. 1821-24. Cuvier 
et Valenciennes, Hist. nat. des poissons, tom. 1, 
| 1828. Jo. Bapt. Spix, Cephalogenesis sive capitis 
| ossei structura, formatio et significatio per omnes 
_ animalium classes, familias, genera, ac etates, fol. 
onach, 1815. Carl Gustav Carus, Von den Ur- 
theilen des Knochen und Schalengeriistes, fol. 
Leipzig, 1828. 
(T. Rymer Jones.) 
_ OSSEOUS TISSUE. Bone. Bone 
SuBstance.—The tissue of bone has, within 
| the last few years, undergone close examination 
_ by various anatomists of note. These exami- 
a ations have been followed with much success, 
and have led to much increase of knowledge of 
| the nature of bone, both as regards its deve- 
lopement and its minute structure. 
_ The general character, the varieties of exter- 
hal conformation, and the anatomical relation 
‘of bone to the contiguous textures, have been 
ably related in a previous article. Under the 
present head it is proposed to treat only of the 
Minute structure and of the developement of 
_ For the sake of precision in the description, 
the elements which conjointly form bone, or 
which are commonly found connected with 
us formation, will be considered under 
te heads. 
¥ 
847 
But before proceeding to this consideration 
of the separate parts it will be well to give a 
general description of them collectively in their 
natural relations. 
The canals which are found every where 
traversing variously the. substance of bone, 
and giving passage to the bloodvessels for 
the nourishment of the tissue, are known by 
the name of Haversian canals, Clopton Havers 
having been the first to give a full description 
of them. The parietes of these canals have a 
laminate arrangement. The lamine themselves 
are numerous and placed concentrically, the in- 
ternal lamina, that which is in immediate con- 
tact with the vessel or vessels, being the most 
distinctly marked, and each succeeding one, as 
you proceed from the canal, having a less dis- 
tinct outline. 
Besides the concentric laminz there are others 
which surround the exterior of the bone, and 
may be known as the superficial lamine. In 
connection with the latter as well as the former 
system of lamine area third set, which can- 
not be traced to belong to either of the foregoing 
orders, but which are placed between them, and 
form the bond of union between each system. 
Late writers on this subject have said much 
of the corpuscles of bone; these are small 
cells of oval form placed between the lamine, 
and having numerous distinct tubes running 
from them in almost every direction. They 
have not inaptly been compared to a spider 
with many legs. 
The corpuscles, or, as others have called 
them, the culcigerous cells, have a definite rela- 
tion to the Haversian canals and to each other. 
These points, however, will be considered in 
detail in a subsequent page. 
The foregoing are the leading points that are 
spoken of in treating of the structure of bone, 
namely, the Haversian canals, the osseous la- 
ming, and the corpuscles. But, upon a closer 
view, it will be seen that the lamine only are 
bone ; the canals and corpuscles are spaces ex- 
isting in bone, and are not really necessary to 
the existence of osseous tissue, though they are 
necessary to its existence where the amount of 
substance is appreciable to the unaided senses. 
Having given a general sketch of the struc- 
ture as it appears when placed under a low 
magnifying power, it will be well to describe 
particularly each of the points which have been 
noticed. 
The most important and that which will be 
placed first in the division is the bone sub- 
stance of which the laminz are composed. 
Of the substance of bone, or hyalitic sub- 
stance.—Writers have, with one or two excep- 
tions, considered the substance of bone as ho- 
mogeneous and without appreciable structure. 
If, however, it be examined under advantageous 
circumstances, with high magnifying powers, 
there will be no difficulty in detecting a very 
definite though delicate structure. For the 
purpose of examination it is best to take a very 
small portion of a thin plate of bone ; such may 
be found in the ethmoid bone of small ani- 
mals, as of the rat. If the piece be well se- 
