EXPERIMENTS 39 



will lead to a strong and complete growth of the bones 

 and a fine development of the body as a whole. Poor 

 food and bad air have a distinctly stunting effect upon 

 bone as upon other growth. 1 



EXPERIMENTS AND DEMONSTRATIONS 



Materials: Bones of the hind leg of a lamb sawed lengthwise 

 through the joints ; pieces of fresh ivory bone, such as the thin 

 bones found in the legs of fowls; pieces of dry ivory bone; 

 hydrochloric acid; ammonia; piece of sheet iron; weighing 

 balance ; human skeleton such as may be purchased for $25 or 

 $30; microscope. 



1) Structure of a long bone: Demonstrate position and ar- 

 rangement of dense (ivory) and cancellated bone; the medul- 

 lary canal; joint ends with epiphyses; articular cartilage; the 

 periosteum; red and yellow marrow; and the microscopic 

 structure of bone. 



2) Composition of bone: 



a) Boil a piece of fresh bone in water to extract gelatine. 



b) Burn a piece of fresh bone to destroy animal matter. 



c) Put a piece of burned bone and a piece of fresh bone mi;o 

 dilute hydrochloric acid (1 part acid to 3 parts water) and let 

 stand 2 days, in order to remove the earthy matter. 



3) Proportions of water and solid in fresh bone: Break a 

 piece of bone into small fragments, weigh; then dry in a cur- 

 rent of warm air to a constant weight and determine loss. 



4) Proportions of animal and mineral matter in dry bone: 



a) Weigh a piece of dry bone, burn on a piece of sheet iron 

 over live coals or over Bunsen burner, and reweigh. 



b) Second method: Weigh, dissolve in 10 per cent hydro- 

 chloric acid, dry in a warm place for 3 or 4 days to obtain a 

 constant weight, and determine loss. 



c) Demonstrate the presence of mineral matter in the solu- 

 tion of b) by precipitating it with ammonia. 



5) Structure of joint: Demonstrate by dissection the cap- 

 sular and reinforcing ligaments ; the synovial fluid ; the articular 

 cartilage ; the function of ligaments. 



1 If the vitality of the bones is weakened, they seem predisposed 

 to disease. The most common disease of bones in childhood is 

 tuberculosis, which forms destructive abscesses in the bones and 

 joints, and thereby causes marked deformities. 



