THE OSSEOUS SYSTEM. 299 



solidified deposits from the synovia, which latter supposition is supported 

 by the frequent occurrence of curdy, more or less consistent, structure- 

 less masses, evidently inspissated synovia, in the tendinous sheaths of 

 the hand. Portions of bone, also, detached from outgrowths at the cir- 

 cumference of the articular ends of the bones, may find their way into 

 the interior of the articulation. The plicce adiposce have perhaps less 

 to do with the formation of the synovia than with the mechanism of the 

 joint, serving the purpose of filling up hollows. 



97. Physical and chemical properties of the Bones, and their acces- 

 sory Organs. The bones are composed, besides a small quantity of 

 water (3-78, according to Stark in the compact substance), and fat (2-3g 

 Bibra), principally of a substance affording gelatine, and of inorganic 

 elements. The latter, in the adult, constitute two-thirds (68-82 Bibra) 

 of dry bone, and are nearly all left when the bone is calcined ; in which 

 case, if due care be taken, the bone completely retains its external 

 aspect, although it may be readily reduced to a white, opaque, friable, 

 heavy powder, the so-termed u bone earth." This consists chiefly of 

 57-59J basic phosphate of lime (according to Heintz, 3 atoms base, 1 

 atom acid), of carbonate of lime (7-8 g) and traces of fluate of lime, 

 phosphate of magnesia, silex (traces), arid alkaline salts. A small part 

 of the salts of bone is also contained in the walls of the vessels and in 

 the lacunae, and this part is dissolved in water. The collagenous sub- 

 stance is the so-termed bone, formative, or ossifying cartilage. It is 

 obtained when bone is treated at a low temperature with dilute hydro- 

 chloric, or nitric acid, in the form of a soft, flexible, elastic, light-yel- 

 lowish, cartilaginous, transparent substance, retaining accurately the 

 shape of the bone. This bone-cartilage constitutes about J of the dry 

 bone, putrefies when moist, and when dried, may be burnt away, leaving 

 a small quantity of ash. It is dissolved by boiling, and from its com- 

 bination with water is produced the gelatine, usually to the amount of 

 3 or 4 times its volume, and which may also be obtained directly by 

 long boiling of the bone in a Papin's digester. 



With regard to the mode in which the principal constituent elements 

 of the osseous tissue are combined, it is certain that the bone earth does 

 not exist as a distinct deposit in any of the constituent parts of healthy, 

 fully formed bone, but rather, although in a solid form, only in a very 

 intimate union with the tissue. Since both the cartilage and the cal- 

 cined bone retain the figure of the bone, in all its particulars, indepen- 

 dently of each other, there can be no doubt, but that the most intimate 

 union of the two substances exists throughout the entire bone, which, 

 however, cannot be regarded as a chemical combination, principally for 

 the reason, that the proportional relations between the collagenous sub- 

 stance and the phosphate of lime are very variable ; and that, by simple 



