A YEAE IN SCIENCE 127 



formed by their union for the upper limb. The upper 

 limb consists of the upper arm bone, the humerus; two 

 bones in the forearm, the ulna and radius; eight irregu- 

 lar wrist bones, the carpals; five bones in the palm of 

 the hand, the metacarpals; and fourteen bones in the 

 fingers, the phalanges. 



The hip consists of one large bone on each side. 

 Notice the size and strength of the hip as compared 

 with the shoulder. Why this difference ? 



The lower limb consists of the upper leg bone, the 

 femur; the two lower leg bones, the tibia and fibula; the 

 knee cap or patella; seven ankle or tar sal bones; five 

 metatarsals; and fourteen toe bones or phalanges. 



Compare each of these parts with the corresponding 

 parts in the arm. 



Exercise 85. Structure and Composition of Bone. 

 Object: To study the structure and chemical com- 

 position of bone. 



Apparatus 



Section of a long bone Hydrochloric acid 20% 



(femur) Glass cylinder 



Beef rib 



Directions: A. Structure. Examine a long bone. 

 Note the long central shaft with enlarged ends. Of 

 what advantage are the enlarged ends ? Note the pink- 

 ish colored covering surrounding the bone. What is 

 its function? This covering is the periosteum. Make 

 a longitudinal section through the bone. Beneath the 

 periosteum note the hard bone; inside of this the spongy 



