138 CLINICAL APPLIED ANATOMY. 



similar sequence of events is noticed when the arm is abducted 

 laterally instead of advanced. But now, instead of becoming 

 winged, the inferior angle of the scapula moves a short distance 

 towards the spine. As soon as the serratus commences to act 

 the bone moves in the opposite direction towards the axilla. 



The serratus magnus is best put in action by causing the 

 patient to push directly forwards against resistance. The part 

 played by the muscle in elevating the arm has already been 

 alluded to. Without the aid of the serratus magnus in tilting 

 the glenoid cavity upwards the deltoid cannot raise the humerus 

 above the horizontal line. 



The rhomboids. When the teres muscles are in action, 

 depressing and adducting the humerus, they at the same time 

 tend to draw the inferior angle of the scapula into the axilla, and 

 this actually happens if the rhomboids are paralysed, since the 

 latter, with the lower part of the trapezius, normally counteract 

 this displacement. 



The glutens maximus is a powerful extensor of the hip. It is 

 not employed in standing or walking on the level, but comes into 

 action in such movements as going upstairs or rising from a seat 

 or stepping up on a chair. Paralysis of this muscle causes the 

 pelvis to remain tilted when standing and so produces a lordosis 

 of the lumbar spine. This lordosis disappears when the patient 

 sits, since the tilting of the pelvis is then counteracted. Weakness 

 of the glutei also gives rise to a peculiar method of extending the 

 trunk by pressure of the hands on the thighs. This is usually 

 known as climbing up the thighs. 



The glutens medius and glutens minimus are important in 

 the act of walking. Their function is to draw the trunk over 

 towards their own side so that the centre of gravity of the 

 body is brought over the head of the femur. The muscles of 

 the two sides act alternately, swaying the pelvis and trunk 

 from one side to the other as the corresponding foot is planted 

 on the ground. 



The ilio-psoas is a flexor of the hip. There is a divergence of 

 opinion as to its rotatory action, but it is perhaps correct to regard 



