PECULIARITIES OF SKELETON. 45 



3. The pelvis, to the sides of which the lower limbs are 

 attached, is proportionately very broad in man, so that the 

 balance of the trunk on the legs is not easily upset when 

 the body is bent towards one side. 



4. The lower limbs are proportionately very long in 

 man. This makes progression on them more rapid by 

 allowing a longer stride, and also makes it difficult to go 

 on "all fours" except by creeping on the hands and 

 knees. The arms of some apes are as long, and of others 

 longer, than their legs. 



5. The arched instep and broad sole of the human 

 foot are very characteristic. Most beasts, as horses, walk 

 on the tips of their toes, the hoof being really a very big 

 nail ; others, as bears, place the heel also on the ground, 

 but have a much less developed tarsal arch than 

 man. The vaulted human tarsus, made up of a' number 

 of small bones, each of which can glide a little over its 

 neighbors, but none of which can move much, is admira- 

 bly calculated to break any jar which might be trans- 

 mitted to the spinal column by the contact of the sole 

 with the ground at each step.* A well arched instep is 



What feature characterizes the human pelvis? What benefit 

 results from it? Which limbs are longest in man? What ends are 

 gained by the considerable length of the legs? Why do infants crawl 

 on the hands and knees instead of the hands and feet? Which limbs 

 are longest in apes? 



What structural points in the foot are especially human? What 

 part of the foot do horses put on the ground? Name an animal 

 which puts the heel also on the ground when it walks. How does 

 the bear's tarsal arch differ from man's? 



"What benefit results from the form and structure of the human 

 tarsus? How? Why is a well-arched instep beautiful? 



* A carriage spring consists of two curved elastic steel bars fastened together at 

 their ends, and with their concave sides turned towards one another. The axle of 

 the wheel is attached to the middle of the lower bar, and the weight of the carriage 



