THE COMPOSITION AND STRUCTURE OF BONE 41 



jelly. The animal matter of the bone has been partially separated by pro- 

 longed boiling, and has been converted into gelatine. 



While studying the skeleton the student will have noticed that 

 the different bones of the body vary considerably in shape. They 

 are generally classified as 



1 . Long bones, as the femur and humerus. 



2. Short bones, as those of the wrist and 

 ankle. 



3. Flat bones, as those of the top of the 

 skull. 



4. Irregular bones, as the vertebrae. 



Fig. 45. Longitu- 

 dinal Section of 

 the Femur, show- 

 ing the Compact 

 and Cancellous 

 Tissues, and the 

 Medullary Cavity. 



Fig. 46. Section of the head of the Femur. 



a, compact tissue ; b, cancellous tissue. 



The long bones, like the femur, tibia, 

 &c., consist of a long shaft, terminating at 

 each end in a head. 



Take a long bone, such as the femur 

 (which should be from an animal recently 

 killed), and saw it longitudinally into halves. 

 Now look at the section and examine the structure of the bone, 

 comparing it with the accompanying diagrams. It will be seen 



