100 GENERAL ANATOMY OF THE TISSUES. 



very frequently lamellated, and hard and brittle from its being inti- 

 mately combined with calcareous salts ; the lacuna? are for the most part 

 lenticular, and are united by very numerous fine processes, the canali- 

 culi ; by which some of them also open upon the outer surface of the 

 bones and into the larger and smaller medullary and vascular spaces in 

 the interior. The lacunce and canaliculi contain a clear substance which 

 may be regarded as the nutritive fluid of the bones, and besides, a cell- 

 nucleus appears in many cases, perhaps constantly, to be enclosed within 

 the lacunae. Besides these two most essential elements, which exist in 

 all bones, numerous vessels and nerves occur in most, as well as, fre- 

 quently, a peculiar substance, the medulla, which supports them, and 

 consists either of common fatty tissue, or of a loose, scanty, connective 

 tissue, with few fat-cells and many peculiar, so-called medulla-cells. 

 These soft parts fill up the larger cavities in the interior of the bones 

 and in the spongy substance ; but are to be found also, at least partially, 

 in narrow canals which penetrate the compact substance, the vascular or 

 Haversian canals, which open in all directions upon the outer and inner 

 surfaces of the bones. 



The matrix of the osseous tissue is composed of an intimate combina- 

 tion of an organic substance, which perfectly agrees with that of the 

 connective tissue, and of inorganic compounds, among which the phos- 

 phate and carbonate of lime are the principal constituents. The fluid 

 contained in the cavities and canals is not thoroughly understood, but it 

 probably presents a preponderance of albumen, fat, and salts, like the 

 serum. The bones, from their solidity and inflexibility, serve as sup- 

 Fig. 32. ports to the softer organs or for their more 

 secure enclosure ; and also perform special func- 

 tions ; as, for example, the auditory ossicles and 

 the parts of the labyrinth which conduct the 

 sonorous vibrations. The development of the 

 bones takes place in two modes : firstly, by the 

 metamorphosis of genuine cartilage, and secondly, 

 by that of a soft blastema composed of indifferent 



FIG. 32. Six developing bone-cells from a rickety bone, as yet sharply defined from the 

 interstitial substance: a, simp le bone-cells ; 6, compound ones running to a parent cell, with 

 two secondary cells; c, such arising from three cells. Magnified 350 diameters. 



bundles of the collagenous substance. But it is their outer portion only, that therefore 

 which corresponds with the matrix of cartilage, which becomes thus changed the elastic 

 element being developed as before, not from separate cells, but by the chemical metamor- 

 phosis of the matrix immediately around the cavity which contains the ;t nucleus," and in 

 various other directions. 



That the pseudo-fibrillated portion of the connective tissue corresponds with the matrix 

 of the cartilages is then, we think, certain. Whether with Remak we are to regard both 

 these as cell- walls, or with Reichert as intercellular substances, must be discussed hereafter. 

 (See General Appendix.) TRS.] 



