330 SPECIAL HISTOLOGY. 



traces of filiate of lime, phosphate of magnesia, silex (traces), 

 and 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 substance 

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

 obtained when bone is treated at a low temperature with 

 dilute hydrochloric, or nitric acid, in the form of a soft, 

 flexible, elastic, light-yellowish, cartilaginous, transparent sub- 

 stance, retaining accurately the shape of the bone. This 

 bone-cartilage constitutes about \ 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 

 combination Avith 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 calcined 

 bone retain the figure of the bone, in all its particulars, inde- 

 pendently 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 pro- 

 portional relations between the collagenous substance and the 

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

 boiling under an increased pressure, the gelatine is separated 

 from the calcareous salts. 



The physical properties of the bones correspond with their 

 composition. Their hardness, density, and rigidity are due to 

 the earthy, whilst their elasticity and flexibility depend upon 

 the organic constituents. In the normal bone of the adult, 

 the two principal constituents are united in such proportions, 

 that the bones, together with considerable hardness and 

 rigidity, have a certain degree of elasticity, though slight, so that 

 they possess a considerable resisting power, and are broken, 

 though not very readily, by the application of greater mechanical 



