column and the pelvis; the layer of cartilage that lines the acetabulum and that covers the head of the femur; the layer of cartilage that covers the lower extremity of the femur and the upper extremity of the tibia and fibula and the tarsus; the successive layers of cartilage interposed between the several bones of the tarsus; and finally, the layer of cartilage that covers both the tarsal and the digital extremities of the metatarsal bones; are so many special provisions to prevent the weight of the body from being transmitted to the ground with a shock; and, at the same time, so many barriers established between the ground and the spinal cord, the brain and the soft and tender organs contained in the thoracic and abdominal cavities, to prevent these organs from being injured by the reaction of the ground upon the body. The excellence of this mechanism is seen in its results; in contemplating "from what heights we can leap—to what heights we can spring—to what distances we can bound—how swiftly we can run—how firmly we can stand—how nimbly we can dance—and yet how perfectly we can balance ourselves upon the smallest surfaces of support!" 210. It is necessary, in order to complete this general view of the structure of the human body, and of the combination and arrangement of its various parts, to denote the several regions into which, for the purpose of describing with accuracy the situation and relation of its more important organs, the body is divided. It is not needful to the present purpose to describe the regions of the head, because its internal cavity contains only one organ, the brain, and its external divisions do not differ materially from those which are common and familiar; but the chest, the abdomen, and the upper and lower extremities are mapped out into regions, of which it is very important to have an exact knowledge, which may be acquired by the study of the annexed diagrams. [Illustration: Fig. CV. Anterior view of the regions of the body. 1. Region of the neck; 2. region of the chest or thorax. Abdominal regions: 3. epigastric; 4. umbilical; 5. hypogastric region. Regions of the upper extremities. 6. shoulder; 7. arm; 8. elbow; 9. fore-arm; 10. wrist; 11. ball of thumb; 12. the axilla or armpit. Regions of the lower extremities: 13. thigh; 14. knee; 15. leg; 16. ankle; 17. instep and foot.] [Illustration: Fig. CVI. Posterior view of the regions of the body: 18. region to the scapula; 19. of the back; 20. of the loins; 21. of the hips; 22. of the ham; 23. of the calf of the leg; 24. of the heel and foot.] [Illustration: Fig. CVII. Lateral view of the regions of the body: 25. arch of the foot.] [Illustration: Fig. CVIII. Anterior view of the situation of the more important internal organs: 1. lungs, right and left; 2. heart; 3. line representing the edge of the diaphragm; 4. liver; 5. stomach; 6. small intestines; 7. colon; 8. urinary bladder.] [Illustration: Fig. CIX.