AND PHYSIOLOGY. 



V5 



ments and cartilage exist wherever two opposite extremities 

 need strength and support to keep them in their places. In 

 the railway locomotive immense strength is required, and at 

 the same time perfect freedom of motion in certain positions, 

 all of which is effected by the ponderous bars, levers and 

 wheels, perfectly secured by bolts, keys and screws. But in 

 the human frame by how much more simple means is the 

 same end secured. No angular or cylindrical couplings 

 secure the human joints, though beautifully adapted to pro- 

 duce movement in every direction, and no attention or care is 

 necessary to lubricate and preserve in good condition the 

 working parts of this machine, but a few tough fibers and 

 membranes, secure at once in a most perfect manner every 

 portion of the frame, and provide at the same time means for 

 its lubrication. 



166. Use of the Anomalous Forms of Bones. — The bones 

 are fitted for the attachment of muscles and ligaments. 

 Hence it is that they are of such anomalous and curi- 

 ous forms, apparently constructed without design or pur- 

 pose. But as we study them, and understand the various 

 motions which they must perform, as well as the organs 

 which many of them must protect, or provide space for, we 

 find that it is impossible to improve in the slightest degree on 

 the construction of the skeleton. The size, the form, the 

 quality of material, the exact position of every process, curve 

 and foramen of the bones, and the manner in which all are 

 arranged, are most wisely adapted to their functions and to 

 the happiness of the vertebrated race. 



167. Reason why the Long Bones are Tubes. — In thia 

 connection should be mentioned the reason why the long 

 bones are hollow. It is for the same cause that the stems of 

 grasses, grains, and many other vegetables are hollow cylin- 

 ders, instead of solid rods : to secure great strength with as 



166. Why are the bones of such peculiar shapes ? 167. Give the reasoD why many of 

 the bones are hollow. 



