[Illustration: Fig. 12. 1, 1, The innominata, (nameless bones.) 2, The sacrum. 3, The coccyx. 4, 4, The acetabulum. a, a, The pubic portion of the innominata. d, The arch of the pubes; e, The junction of the sacrum and lower lumbar vertebra.] 94. The COCCYX, in infants, consists of several pieces, which, in youth, become united and form one bone. This is the terminal extremity of the spinal column. -=-=-=-=-=-=-=-=-=-=-=-= In the adult? Describe the acetabulum. 93. Describe the sacrum. Explain fig. 12. 94. Describe the coccyx. -=-=-=-=-=-=-=-=-=-=-=-= CHAPTER V. ANATOMY OF THE BONES, CONTINUED 95. The bones of the upper and lower limbs are enlarged at each extremity, and have projections, or processes. To these, the tendons of muscles and ligaments are attached, which connect one bone with another. The shaft of these bones is cylindrical and hollow, and in structure, their exterior surface is hard and compact, while the interior portion is of a reticulated character. The enlarged extremities of the round bones are more porous than the main shaft. 96. The UPPER EXTREMITIES contain sixty-four bones--the _Scap´u-la_, (shoulder-blade;) the _Clav´i-cle_, (collar-bone;) the _Hu´mer-us_, (first bone of the arm;) the _Ul´na_ and _Ra´di-us_, (bones of the fore-arm;) the _Car´pus_, (wrist;) the _Met-a-car´pus_, (palm of the hand;) and the _Pha-lan´ges_, (fingers and thumb.) 97. The CLAVICLE is attached, at one extremity, to the sternum; at the other, it is united to the scapula. It is shaped like the Italic _[s]_. Its use is to keep the arms from sliding toward the breast. 98. The SCAPULA is situated upon the upper and back part of the chest. It is flat, thin, and of a triangular form. This bone lies upon and is retained in its position by muscles. By their contractions it may be moved in different directions. 99. The HUMERUS is cylindrical, and is joined at the elbow with the ulna of the fore-arm; at the scapular extremity, it is lodged in the _glenoid_ cavity, where it is surrounded by a membranous bag, called the _capsular ligament_. -=-=-=-=-=-=-=-=-=-=-=-= 95-104. _Give the anatomy of the bones of the upper extremities._ 95. Give the structure of the bones of the extremities. 96. How many bones in the upper extremities? Name them. 97. Give the attachments of the clavicle. What is its use? 98. Describe the scapula. How is it retained in its position? 99. Describe the humerus. -=-=-=-=-=-=-=-=-=-=-=-= [Illustration: Fig. 13. 1, The shaft of the humerus. 2, The large, round head that is placed in the glenoid cavity. 3, 4, Processes, to which muscles are attached. 5, A process, called the external elbow. 6, A process, called the internal elbow. 7, The articulating surface upon which the ulna rolls.]