238 THE SKELETON. 



" barrel-shaped chest. " In severe cases of lateral curvature of the spine the thorax becomes 

 much distorted. In consequence of the rotation of the bodies of the vertebrae which takes 

 place in this disease the ribs opposite the convexity of the dorsal curve become extremely con- 

 vex behind, being thrown out and bulging, and at the same time flattened in front, so that the 

 two ends of the same rib are almost parallel. Coincident with this, the ribs on the opposite 

 side, on the concavity of the curve, are sunk and depressed behind and bulging and convex in 

 front. In addition to this the ribs become occasionally welded together by bony material. 



The ribs are frequently the seat of necrosis leading to abscesses and sinuses, which may 

 burrow to a considerable extent over the wall of the chest. The only special anatomical point 

 in connection with these is that care must be taken in dealing with them that the intercostal 

 spaee is not punctured and the pleural cavity opened or the intercostal vessels wounded. 



In cases of empyema the chest requires opening to evacuate the pus. There is consider- 

 able difference of opinion as to the best position to do this. Probably the best place in most 

 cases will be found to be between the fifth and sixth ribs, in or a little in front of the mid- 

 axillary line. This is the last part of the cavity to be closed by the expansion of the lung ; it 

 is not thickly covered by soft parts ; the space between the two ribs is sufficiently great to allow 

 of the introduction of a fair-sized drainage-tube, and the opening is in a dependent position, 

 when the patient is confined to bed, as he usually inclines toward the affected side, so as to 

 allow the sound lung the freest possible play, and so permits of efficient drainage. 



OF THE EXTREMITIES. 



The extremities, or limbs, are those long, jointed appendages of the body 

 which are connected to the trunk by one end and free in the rest of their extent. 

 They are four in number : an upper or thoracic pair, connected with the thorax 

 through the intervention of the shoulder, and subservient mainly to prehension ; 

 and a lower pair, connected with the pelvis, intended for support and locomotion. 

 Both pairs of limbs are constructed after one common type, so that they present 

 numerous analogies, while at the same time certain differences are observed in each, 

 dependent on the peculiar offices they have to perform. 



The bones by which the upper and lower limbs are attached to the trunk are 

 named respectively the shoulder and pelvic girdles, and they are constructed on the 

 same general type, though presenting certain modifications relating to the different 

 uses to which the upper and lower limbs are respectively applied. The shoulder 

 girdle is formed by the scapula and clavicle, and is imperfect in front and behind. 

 In front, however, the girdle is completed by the upper end of the sternum, with 

 which the inner extremities of the clavicle artic.ulate. Behind, the girdle is widely 

 imperfect and the scapula is connected to the trunk by muscles only. The pelvic 

 girdle is formed by the innominate bones, and is completed in front through the 

 symphysis pubis, at which the two innominate bones articulate with each other. 

 It is imperfect behind, but the intervening gap is filled in by the upper part of 

 the sacrum. The pelvic girdle, therefore, presents, with the sacrum, a complete 

 ring, comparatively fixed, and presenting an arched form which confers upon it a 

 solidity manifestly intended for the support of the trunk, and in marked contrast 

 to the lightness and mobility of the shoulder girdle. 



With regard to the morphology of these girdles, the blade of the scapula is 

 generally believed to correspond to the ilium ; but with regard to the clavicles 

 there is some difference of opinion : formerly it was believed that they corre- 

 sponded to the ossa pubis, meeting at the symphysis, but it is now generally taught 

 that the clavicle has no homologue in the pelvic girdle, and that the os pubis and 

 ischium are represented by the small coracoid process in man and most mammals. 



THE UPPER EXTREMITY. 



The bones of the upper extremity consist of those of the shoulder girdle, of 

 the arm, the forearm, and the hand. The shoulder girdle consists of two bones, 

 the clavicle and the scapula. 



THE SHOULDER. 



The Clavicle. 



The Clavicle (clavis, a key), or collar-bone, forms the anterior portion of the 

 shoulder girdle. It is a long bone, curved somewhat like the italic letter /, and 



