1C - fll-E FRAMEWORK OF THE BODY. 



holding rhe softer parts in their proper places. They 

 assist in movement, by affording points of attachment to 

 those organs which have power of motion the muscles. 



3. The Form and Composition of the Bones. 

 Their shape and size vary greatly in different parts of the 

 body, but generally they are arranged in pairs, one bone for 

 each side of the body. They are composed of both mineral 

 and animal substances, united in the proportion of two 

 parts of the former to one of the latter ; and we may sep- 

 arate each of these substances from the other for examina- 

 tion. First, if we expose a bone to the action of fire, 

 the animal substance is driven off, or " burned out." We 

 now find that, though the shape of the bone is perfectly 

 retained, what is left is no longer tough, and does not sus- 

 tain weight as before. Again, we may remove the mineral 

 portion, which is a form of lime, by placing a bone into a 

 dilute acid. The lime will be dissolved out, and the shape 

 of the bone remain as before; but now its firmness has 

 disappeared, and it may be bent without breaking. 



4. If, for any reason, either of these ingredients is dis- 

 proportionate in the bone during life, the body is in 

 danger. The lime is useful in giving rigidity of form, 

 while the animal substance insures toughness and elas- 

 ticity. By their union, we are able to withstand greater 

 shocks and heavier falls than would be possible with 

 either alone. In youth, the period of greatest activity, 

 the animal constituent is in excess: a bone then does 

 not break so readily, but, when broken, unites with great 

 rapidity and strength. On the other hand, the bones of 

 old persons are more easily broken, and in some cases fail 

 to unite. The mineral matter being then in excess, indi- 

 cates that the period of active exertion is drawing to a 

 close. 



3. Their shape and size * Of what composed? Possibility of being separated ? 

 Effect of fire ? Of dilute acid ? 



4. Effect of deficiency of ingredient ? Usefulness of the lime ? Of the animal 

 substance? Effect of their union ? Condition, in youth? Old age? 



