THE OSSEOUS SYSTEM. 283 



water, 25'0 solid matters, such as albumen, fibrin, extractive matter, 

 and salts, similar to those of muscle, and merely traces of fat. With 

 respect to its structure, it presents, besides vessels and nerves, connective 

 tissue, fat-cells, free fat, a fluid, together with, lastly, peculiar minute 

 cells, marrow-cells. Connective tissue and fat are universally present, 

 though in very various quantities. The former, on the surface of the 

 larger medullary masses of the difaphyses, is of rather firmer consistence, 

 but cannot properly be described as a medullary membrane (endosteum, 

 periosteum internum), because it does not admit of being separated as 

 a continuous structure. In the interior of the marrow in the spongy 

 bones, scarcely any connective tissue can be detected except in the larger 

 masses of it, whilst in the diaphyses, this tissue can be readily demon- 

 strated as a very lax and delicate, areolated structure, containing the fat 

 and supporting the vessels and nerves. Its elements correspond with 

 those of the lax connective tissue (vide 24) ; although, as far as I have 

 seen, it does not contain any elastic filaments. Fat-cells of O'OlG-0'032 

 of a line, not unfrequently with a distinct nucleus, occur in large quanti- 

 ties in the yellow, more dense marrow, quite as abundantly as in the 

 panniculus adiposus, but for the most part not aggregated into distinct 

 lobules. In the reddish marrow, when expressed, they are more rare ; 

 and in the red pulp of the bodies of the vertebra; and of the flat cranial 

 bones, they occur only in very minute, scanty accumulations, or alto- 

 gether isolated, to which circumstance, according to Berzelius, is owing 

 the small quantity of fat in the diploe. In dropsical marrow these cells 

 are frequently only half filled with fat, or with but one or 

 more globules, containing, besides, a large quantity of 

 serum ; and in hypersemia of the bones, they appear occa- 

 sionally to be diminished in size, and occasionally elongated 

 and fusiform. Free fat-globules, and a clear or yellowish 

 fluid, are often met with in the softer kinds of marrow, 

 and frequently in considerable quantity. That the former 

 have not been set free from cells, in the preparation of the 

 specimen, may be satisfactorily shown, but it must remain uncertain 

 whether or not they are to be referred to cells that have ceased to exist. 

 Lastly, there occur, together with some fluid, in all the red, or even only 

 reddish marrow (never in the yellow), minute roundish, nucleated cells, 

 exactly like those of the young medulla (vid. infra, fig. 132). These me- 

 dulla-cells correspond in every particular with those, which Hasse and 

 I (" Zeitsch. f. ration. Medicin," Bd. V.) found in the hypersemiated red 

 marrow of the articular extremities of the cylindrical bones, but never- 

 theless normally exist in the vertebra?, the true cranial bones, in the 

 sternum, and in the ribs, whilst they are wanting in the long and short 



FIG. 120. Two fat-cells from the marrow of the human femur: a, nucleus; 6, cell-mem- 

 brane ; c, oil ; magnified 350 diameters. 



