OSSEOUS TISSUE. 



847 



parts of the osseous system, of which we need 

 only adduce as instances the fishing filaments 

 upon the back of the head of Lop/iius, and the 

 powerful weapons of Silitrus 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 to any 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 

 an extent 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. 



BIBLIOGRAPHY. In addition to the authorities 

 quoted in the text the comparative osteologist is re- 

 ferred to the following sources of information. 

 Cunier, Lemons d'anatomie comnaree, 5 torn. 8vo. 

 ann. VIII XIV. Cuvier, Recherches sur les 

 ossemeiis fossiles, 5 torn. 4to. 1821-24. Cuvier 

 et Valenciennes, Hist. nat. des poissons, torn. 1, 

 1828. Jo. Bapt. Spix, Cephalogenesis sive capitis 

 ossei structura, formatio et signiticatio per omnes 

 animalium classes, familias, genera, ac states, fol. 

 Monach. 1815. Carl Gustav Gurus, Von den Ur- 

 theilen des Knochen und Schalengerlistes, fol. 

 Leipzig, 1828. 



( T. Ruiner 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- 

 nations 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- 

 nal 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 

 bone. 



For the sake of precision in the description, 

 the elements which conjointly form bone, or 

 which are commonly found connected with 

 osseous formation, will be considered under 

 separate heads. 



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 laminae 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 laminae there are others 

 which surround the exterior of the bone, and 

 may be known as the superficial laminae. In 

 connection with the latter as well as the former 

 system of laminae are a 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 laminae, 

 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 calcigerous 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 laminae 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 laminae 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 cethmoid bone of small ani- 

 mals, as of the rat. If the piece be well se- 



