Bones

Hard ti ues which form the framework or skeleton of nearly all the vertebrates, and consist of ab. 33 per cent of gelatin and other organic matter, 57 of phosphate of lime, and 10 of other salts of lime and magnesium, all of the inorganic matter being uniformly distributed throughout the gelatin, so that when the former are di olved out the latter retains the natural form of the bone. On their exterior is a tough membrane, periosteum, which supplies them with nourishment; within they are divided up into a number of cavities containing marrow. In many of them, especially those of considerable length, there is a large central cavity, also containing marrow. A familiar illustration of this form of bone is the shinbone of an ox. The bones in the human body, excluding the teeth, number 208.