CHAPTER III. 



Structure of the body. Bones, cartilages, joints Muscles, tendons, 

 aponeuroses. 



Bones. The bones are the framework of the human 

 body. They are formed of a hard and extremely resistant 

 tissue, and they surround more or less completely with 

 solid walls the cavities containing delicate organs; they 

 provide attachments and support for the soft parts, and 

 furnish a fulcrum for the movements of the body; and lastly, 

 by their resistance they permanently maintain the propor- 

 tions between its different parts. 



The osseous substance is composed of calcareous salts 

 phosphate or carbonate of lime intimately combined with 

 organic principles, the decomposition of which produces 

 gelatine. 



If the bone is immersed for a length of time in hydro- 

 chloric acid, the calcareous matter will be dissolved, and the 

 isolated gelatine will retain perfectly the form of the bone; 

 and in the same manner if the gelatine be destroyed by 

 combustion, the lime which remains will show the normal 

 form and dimensions of the bone. In a gelatinous state the 

 bone is soft and flexible; in the calcareous state it is hard, 

 rigid, and brittle ; in a normal condition each of these con- 

 stituent substances serves as a corrective to the other; and 

 their properties united give to bone its solidity and its 

 elastic resistance. 



In the osseous tissues, as in all those of the body, we re- 

 cognize a movement of composition and of decomposition, of 

 molecules assimilated and again rejected after a certain time; 

 but in none of the organs so well as in the bones has it 



