114 



ANALYSIS OF 



[ 238. The chemical composition of the inorganic consti- 

 tuents of bone in the four classes, is shewn in the following 

 table. 



ANALYSIS OF BONES. 



[ 239. The primitive basis of bone, is a subtransparent 

 glairy fluid, resembling mucus in its chemical composition, 

 and containing a multitude of minute corpuscles. When it 

 passes into the stage of cartilage, a number of elliptical 

 nucleated cells make their appearance ; in proportion as the 

 cells increase in size and number, the cartilage hardens, and 

 at the point where ossification is about to commence, they ar- 

 range themselves in linear rows. In the long bones the cell 

 rows are parallel to the axis of the bone, and in the flat 

 bones, they run in rays from the centre to the periphery. 

 The nucleated cells are the agents by which the earthy parti- 

 cles are arranged in order ; and in bone, as in teeth, there may 

 be discerned in this predetermined arrangement, the same re- 

 lation to the acquisition of power and resistance with the great- 

 est economy in the building material, as in the disposition of 

 the beams and columns of a work of human architecture.* 



[ 240. The intimate structure of bone can only be studied 

 by the aid of the microscope ; for this purpose, very thin 

 sections of the bones of fishes, reptiles, birds, and mammals, 

 should be prepared and mounted on glass slides in Canada 

 balsam, and covered with very thin glass ; by this means a 

 series of comparative observations may be made. If we take 

 a transverse section of one of the long bones of man, the 

 femur, for example, and examine it with a power of about 

 two hundred linear, we observe that it is traversed by a num- 

 ber of canals called Haversian, which transmit blood-vessels 



* Professor Owen's Comparative Anatomy of Fishes contains ample 

 details on this subject. 



