72 THE HUMAN BODY 



as pronation. The elbow end of the humerus (Fig. 40) bears a 

 large articular surface : on the inner two-thirds of this, the ulna fits, 

 and the ridges and grooves of both bones interlocking form a hinge- 

 joint, allowing only of bending or straightening the forearm on the 

 arm. The radius fits on the rounded outer third, and forms there 

 a ball-and-socket joint at which the movement takes place when 

 the hand is turned from the supine to the prone position; the ulna 

 forming a fixed bar around which the lower end of the radius is 

 moved. 



Gliding Joints. These permit as a rule but little movement: 

 examples are found between the closely packed bones of the tarsus 

 and carpus, (Figs. 34 and 35) which slide a little over one another 

 when subjected to pressure. 



Hygiene of the Joints. When a bone is displaced or dislocated 

 the ligaments around the joint are more or less torn and other 

 soft parts injured. This soon leads to inflammation and swelling 

 which make not only the recognition of the injury but, after 

 diagnosis, the replacement of the bone, or the reduction of the dis- 

 location, difficult. Moreover, the muscles attached to it constantly 

 pull on the displaced bone and drag it still farther out of place; so 

 that it is of great importance that a dislocation be reduced as soon 

 as possible. In most cases this can only be attempted with safety 

 by one who knows the form of the bones, and possesses sufficient 

 anatomical knowledge to recognize the direction of the displace- 

 ment. No injury to a joint should be neglected. Inflammation 

 once started there is often difficult to check and runs on, in a 

 chronic way, until the synovial surfaces are destroyed, and the 

 two bones perhaps grow together, rendering the joint permanently 

 stiff. 



Immediate and complete rest has been commonly supposed to 

 be the only proper treatment for sprained joints, but it has been 

 shown recently that massage, properly applied by one expert in its 

 use, has a remarkably beneficial effect upon sprains. Injuries of 

 this sort so severe that under the rest treatment they would re- 

 quire weeks for recovery yield so completely in a few days to 

 massage treatment that the injured individual can participate in 

 athletic contests. It should be borne in mind that massage to be 

 effective must be applied by an expert in its use. 



