CHAPTER XVI 



LOCOMOTOR SYSTEM 



Section i. 



Muscles, Joints, Tendons, Ligaments. 



Muscles and Joints. — The structure of muscle, its innerva- 

 tion, and the phenomenon of a muscular contraction, have 

 been studied. It is here intended to examine the muscles 

 at work, and ascertain what they are capable of effecting, 

 and how they effect it. Speaking broadly, the skeleton is 

 clothed with muscle ; there are exceptions, such as the 

 face and the limbs below knees and hock, where the frame- 

 work is uncovered, but generally the bones are clothed, the 

 muscular covering of the limbs becoming progressively lighter 

 from above to below. The scapula and humerus, the pelvis and 

 femur, are buried beneath a mass of muscle ; over the radius 

 and tibia the muscular structure is much less in bulk, and 

 immediately at the knee and hock it suddenly ends. The 

 movements of the limbs of quadrupeds are of a simple character. 

 Keeping entirely to solipeds, it consists of a to-and-fro pendulum 

 motion, and a limited movement in an outwards and inwards 

 direction. This is infinitely more simple than in those animals 

 furnished with a paw or hand. The limbs have to be flexed 

 and extended, abducted and adducted, and both in the fore 

 and hind legs these are carried out entirely by the muscles 

 clothing or attached to the scapula and humerus, pelvis, femur, 

 and tibia.* Speaking broadly, no muscles originate below the 



* A definition of the following terms employed in limb and joint move- 

 ments may be desirable : 



Flexion and Extension refers to either joints or limbs. To flex a limb 

 is to bend it ;to extend a limb is to straighten it. Nevertheless this does 

 not cover the entire ground ; the foot, for instance, during the movement 

 of flexion causes the pastern to become extended — viz., straightened. 

 Conversely, when the foot is extended, the pastern is bent or flexed. 



Abduction and Adduction. — These terms only apply to limbs. A limb 

 is abducted when it is carried away from the middle line of the body. 

 Similarly, it is adducted when drawn towards the middle line. The amount 



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