The outlines of anatomy, physiology, and hygiene Being an edition of The essentials of anatomy, physiology, and hygiene, rev to conform to the legislation making the effects of alcohol and other narcotics upon the human system a mandatory study in public schools . h, are holes, out ofwhich pass nerves supplying themuscles and other organs of thebody, and into which pass theblood-vessels that nourish thespinal cord, 20. The Spine. — The back-bone, being composed of so manypieces, is very movable. Thepower of motion varies, however,in different parts. It is greatestin the neck, and least in that
The outlines of anatomy, physiology, and hygiene Being an edition of The essentials of anatomy, physiology, and hygiene, rev to conform to the legislation making the effects of alcohol and other narcotics upon the human system a mandatory study in public schools . h, are holes, out ofwhich pass nerves supplying themuscles and other organs of thebody, and into which pass theblood-vessels that nourish thespinal cord, 20. The Spine. — The back-bone, being composed of so manypieces, is very movable. Thepower of motion varies, however,in different parts. It is greatestin the neck, and least in that por-tion of the back to which the ribsare attached. In the human be-ing, the neck is not so flexibleas in many animals. Birds, inparticular, can look directly back-ward. Notwithstanding the great Fig. 9.—The spine, sa\vn in two lengthwise, ^ ... , Showing the spinal powcr of motiou m the spme, the canal and the holes different boucs are very strongly between the verte- ^^^^-^^^ ^^^^^ protected bv power- brae, where nerves and ^ - -^ blood-vessels pass out. ful ligaments and muscles, which 20 ORGANS OF MOTION. render it difficult for a vertebra to slip out of place,and such an accident is one of the rarest which asurgeon is ever called upon to Fig. io.—A vertebra. The elastic pads between the vertebrae deaden allshocks of the body and prevent them from injuringthe brain. These pads become compressed duringthe day, especially when a person is much on hisfeet, so that at night-time the body is from onequarter to one half an inch shorter than it is in themorning. During sleep or rest the elasticity of thepads causes them to resume their original shapeand thickness. 21. The Skull.—The skull is the only portion ofthe skeleton whose principal office is the protec-tion of soft parts within it. Accordingly, we find SUTURES OF THE SKULL. 21 that its bones are differently composed and dif-ferently put together from the other bones in thebody. Those forming the outside of
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