60 LABORATORY EXERCISES. 



D. Drawings. 



1 . Represent in a drawing the longitudinal and 



cross-section of the piece of rib, indicat- 

 ing diagrammatically the different kinds 

 of tissue. 



2. In the same way make drawings of the lon- 



gitudinal and cross-sections of the long 

 bone. 



31. COMPOSITION OF BONES. 



Materials : Two clean ribs ; the two halves of the soup-bone used 

 in 30; diluted hydrochloric acid (6 parts water to 1 part acid) ; weigh- 

 ing balances; a piece of wire. 



A. Action of acid on bone. 



Compare the two ribs as to form and size; 

 place one of them in a bottle of diluted hydro- 

 chloric acid. Allow the bone to remain in the* 

 acid for a few days and then compare the two 

 ribs again. 



1 . Has the acid changed the form of the bone ? 



2. Has it changed the size of the bone? 



3. Try to bend the two rib bones. What 



change do you observe to have taken 

 place in the one which has been in the 

 acid? 



4. Pour some of the liquid in which the bone 



has been soaking into an evaporating- 

 dish and heat over an alcohol- lamp or 

 over a gas-flame until the liquid has dis- 

 appeared. What kind of substance is 



