Fig. 20.
Fig. 20. A side view of the bones of the foot, showing its arched form. The arch rests upon the heel behind, and the ball of the toes in front. 1, The lower part of the tibia. 2, 3, 4, 5, Bones of the tarsus. 6, The metatarsal bone. 7, 8, The bones of the great toe. These bones are so united as to secure a great degree of elasticity, or spring.
Observation. The tarsal and metatarsal bones are united so as to give the foot an arched form, convex above, and concave 45 below. This structure conduces to the elasticity of the step, and the weight of the body is transmitted to the ground by the spring of the arch, in a manner which prevents injury to the numerous organs.
111. Describe the metatarsal bones. Explain fig. 19. What is represented by fig. 20? What is said of the arrangement of the bones of the foot?
112. The PHALANGES (fig. 19) are composed of fourteen bones; each of the small toes has three ranges of bones, while the great toe has but two.
113. The JOINTS form an interesting part of the body. In their construction, every thing shows the regard that has been paid to the security and the facility of motion of the parts thus connected together. They are composed of the extremities of two or more bones, Car´ti-lages, (gristles,) Syn-o´vi-al membrane, and Lig´a-ments.
Fig. 21.
