Animals. 89 



bones, burnt ones, and some which have been buried all 

 are of use in teaching this subject. 



Preparation. Procure a chicken leg-bone and three soup- 

 bones ; the best are ordinary marrow-bones. One of the 

 latter should be fresh from the market, with marrow in it, 

 and sawn open by the butcher ; the other may be obtained 

 from the kitchen after soup has been made. Boil this sec- 

 ond bone in strong suds to remove fat. Scrape off the 

 specks of muscle, etc., and remove the remains of marrow 

 with a soft cloth on a stick ; then get the butcher to saw 

 this bone also. The third marrow-bone should also be an 

 old one, and should be put in the fire for half an hour to 

 burn out the animal matter. The chicken bone should be 



FIG. 22. SECTION OF BONE. 

 s, s, s, Articulating surfaces. 



immersed in diluted hydrochloric acid, and left overnight 

 to remove mineral matter. When the above articles are 

 ready, they may be placed in a box and taken to school for 

 use. 



The Lesson. I. Pass the raw bone around the class. 

 Point out bone, marrow, smooth covering of bone (perios- 

 teum), very smooth moist end of bone (synovial membrane); 

 notice where ligaments and tendons join the bone. Bring 

 out the fact that the marrow is merely fat stored away in 

 the bones for use. 



II. Give them the boiled bone to examine. Note its 

 form, size, structure ; that it is larger at ends. Why ? That 

 it is softer at ends. Why ? That it is harder and more 



