186 



DETAILED SYNTHESIS. 



bles easily, showing that the substance that gave tenacity 

 has been burned out. 



181. IF A BONE IS EXPOSED TO THE ACTION OF DI- 

 LUTED NITRIC OR MURIATIC ACID for a time, an earthy 

 substance is taken from it, and a flexible gristly sub- 

 stance of the form and size of the original bone is left. 



FIG. 148. 



Fig. 148 repre- 

 sents the animal or 

 gristly portion of a 

 bone tied in a knot. 



182. THESE EXPERIMENTS SHOW that bones are con- 

 stituted of two classes of substance, one called the 

 earthy, and the other the animal part it is about one 

 third the whole. 



183. THE ANIMAL PART is ALSO CALLED gristle, but 

 not properly, for it is found to be composed of gelatine, 

 like white sinewy tissue ; but it has not a fibrous ar- 

 rangement. Another name is Osteine. 



184. BONES THEN ARE COMPOSED of gelatine, with a 

 large but variable proportion of earthy substance, phos- 

 phate of lime and magnesia, and carbonate of lime, inti- 

 mately combined throughout, so that both the gelatine 

 and the earths have the entire size and form of the bone. 



185. BONE is FORMED by having cartilage or fibrous 

 membrane, first constituted in the position which the bone 

 is to occupy ; then the cartilaginous matter is exchanged 

 for the gelatinous, or the fibrous arrangement of it is 

 changed, and the earthy matter is deposited in increased 



181. What ? Describe Fig. 148. 1S2. What do - ? 183. What - ? 184 Of 

 what-? 185. Howls? 



