xciv BONE. 



account of the growth and development of bone, to which head, indeed, the 

 subject more properly belongs, although it has seemed expedient to intro- 

 duce it here. 



All over the section numerous little dark specks are seen among the 

 lamelhe. These are named the " osseous corpuscles;" but as it is now 

 known that they are in reality minute cavities existing in the bony sub- 

 stance, the name of u lacunae " has since been more fittingly applied to 

 them. To see the lacuuse properly, however, sections of unsoftened bones 

 must be prepared and ground very thin, and a magnifying power of from 

 200 to 300 must be employed. Such a section, viewed with transmitted 

 light, has the appearance represented in fig. XLIV. The openings of the 

 Haversian canals are seen with their encircling lamellae, and among these 

 the corpuscles or lacuuse, which are mostly ranged in a corresponding 

 order, appear as black or dark brown and nearly opaque, oblong spots, with 

 fine dark lines extending from them and causing them to look not unlike 

 little black insects ; but when the same section is seen against a dark 

 ground, with the light falling on it (as we usually view an opaque object), 

 the little bodies and lines appear quite white, like figures drawn with 

 chalk on a slate, and the intermediate substance, being transparent, now 

 appears dark. 



The lacunae, as already stated, are minute recesses in the bone, and the 

 lines extending from them are fine pores or tubes named " canaliculi," 

 which issue from their cavity. They present some variety of figure, but in 

 such a section as that represented they for the most part appear irregularly 

 fusiform, and lie nearly in the same direction as the lamellte between 

 which they are situated ; or, to speak more correctly, the little cavities 

 are flattened and extended conformably with the lamellae ; for when the 

 bone is cut longitudinally, their sections still appear fusiform and length- 

 ened out in the direction of the lamellae. The canaliculi, on the other 

 hand, pass across the lamellae, and they communicate with those proceeding 

 from the next range of lacunae, so as to connect the little cavities with 

 each other ; and thus, since the canaliculi of the most central range open 

 into the Haversiau canal, a system of continuous passages is established by 

 these minute tubes and their lacuuse, along which fluids may be conducted 

 from the Haversian canal through its series of surrounding lamellae ; in- 

 deed, it seems probable that the chief purpose of these minute passages is 

 to convey nutrient fluid from the vascular Haversian canals through the 

 mass of hard bone which lies around and between them. In like manner 

 the canaliculi open into the great medullary canal, and into the cavities 

 of the cancellated texture ; for in the thin bony parietes of these cavities 

 lacunae are contained ; they exist, indeed, in all parts of the bony tissue. 

 As first shown by Virchow, each lacuna is occupied by a nucleated cell, or 

 soft corpuscle, which may be separated from the surrounding substance by 

 prolonged maceration of decalcified bone in hydrochloric acid or in solu- 

 tion of potash or soda ; and later observers (Rouget, Neumann,) state that 

 they are able to detach also the proper osseous wall of the lacuna and its 

 appertaining canaliculi after decalcification, and to obtain it separate with 

 its. included corpuscle. The soft corpuscle or cell has an angular outline 

 corresponding to the shape of the lacuna, but it is not proved that it sends 

 branches along the canaliculi, as Virchow supposed, or that it has a mem- 

 branous envelope. Nevertheless, it can scarcely be doubted that the proto- 

 plasm of the nucleated corpuscle takes an important share in the nutritive 

 process in bone, and very probably serves both to modify the nutritive 



