200 THE NATURE AND TREATMENT OF 



ULTIMATE CONSTITUENTS OF BONES. 



The ultimate constituents of bones are gelatine, animal mat- 

 ter, carbonate, phosphate, and fluate of lime, phosphates of soda 

 and magnesia. Their growth, like that of shells, is effected by 

 the addition of new tissue to that already formed. Bones which 

 have a central cavity are protected internally by cartilaginous 

 fibres or unions ; hence they expand or burst, so soon as their 

 cartilaginous braces are decomposed by a diseased condition of 

 the parts. 



DILATATION OF THE JAW BONES. 



This disease seems to be more prevalent among horses than 

 cattle. In equine practice it is termed " big-head ; " in bovine 

 practice we call it spina ventosa, * bony tumor, etc. ; but per- 

 haps " dilatation of bone" will give the reader a better idea of 

 the character of the disease than any other term. On inspect- 

 ing the jaw bones of cattle, the subjects of dilatation, we find 

 the greatest enlargement at the angle of the lower jaw. On 

 cutting into the same its cavity is occupied by a preparation 

 resembling soft cheese. On removing this it is discovered that 

 the cartilaginous braces, which hold the sides of the bone to- 

 gether, are decomposed ; hence the dilatation. This foreign 

 material often degenerates into true pus, and burrows through 

 the bones toward the surface. In this condition a fluctuating 

 tumor can be felt at the angle of the jaw. 



Sometimes the bones of the jaw appear to have lost their 

 cohesive firmness and vitality ; they then border on a state 

 known as necrosis. Now if a portion of bone in this condi- 

 tion be macerated, for only a short time, in a weak solution of 

 muriatic acid, it can be rolled up like a piece of paper, show- 

 ing that it is deficient in calcareous matter ; but if it takes 

 a day or more to put the bone in this condition, the experi- 



* Spina ventosa. — A bony tumor, in which the interior of the bone is ab- 

 Borbed, leaving a mere shell of bone, divided into cells, containing purulent, 

 cheesy matter. (See cut of bones, page 245). 



