102 STUDIES IN ADVANCED PHYSIOLOGY. 



bone in and around this membrane the fully formed parietal 

 comes to be. While not strictly analagous, the primitive 

 membrane might be compared with the periosteum, next to 

 which, as in the long bone, occurs the mineral deposit. 



CHEMICAL COMPOSITION OF BONE. 



The chemical composition of bone has been referred to. 

 Human bone consists of sixty-five per cent, inorganic mat- 

 ter and thirty- five per cent, organic matter. This organic 

 matter consists of a matrix called osseine, with which the 

 inorganic constituents so combine that even under a micro- 

 scope it looks homogeneous. This osseine is easily changed 

 by boiling it, into the familiar gelatine. In fact, much of 

 the gelatine of commerce is derived from the bones of 

 slaughtered animals, and an integral ingredient of the soup 

 made by boiling a soup bone is gelatine. It figures further 

 in a variety of roles in the preparation of foods and desserts 

 familiar to every household cook. The mineral salts are 

 mainly calcium phosphate and calcium carbonate, and from 

 this mineral part of bone-earth much of the phosphorus of 

 commerce is derived. By placing a bone in weak hydro- 

 chloric acid it is possible to dissolve out the mineral salts 

 and leave nothing but the organic portions. Such a bone 

 is soft and flexible. On the other hand, it is possible to re- 

 move the organic portion by what is known as calcining the 

 bone in a hot fire, which burns up all the organic matter. 

 In this way the bone-dust of commerce is made. When 

 the organic matter of a bone is not completely burned up, 

 but charred, it forms the familiar bone-black used in many 

 ways in the arts and in commerce, especially in the purifi- 

 cation of sugar. 



HISTORICAL. 



As early as 1736 Nesbitt showed that some flat bones 

 were formed perfectly independently of cartilage, and even 

 insisted that the cartilage was often destroyed in cases 

 where it did precede the real bone structure. The primi- 



