... bones of the skeleton are considered in three divisions: the _head_, the _trunk_, and the _limbs_. 1. THE HEAD. THE BONES OF THE SKULL AND THE FACE form a cavity for the protection of the brain ... between the brain and the rest of the body. FIG. 6. [Illustration: _The Spine; the seven vertebræ of the neck, cervical; the twelve of the back, dorsal; the five of the loins, lumbar;_ a, _the ... above. 3. THE LIMBS. TWO SETS OF LIMBS branch from the trunk, viz.: the upper, and the lower. They closely resemble each other. The arm corresponds to the thigh; the forearm, to the leg; the wrist,...