294 ANTAGONISM OF MUSCLES. 



of a tree, they then raise the body upwards towards the arms, 

 and thus become the muscles used in climbing. 

 In violent dyspnoea, arising from spasmodic croup, asthma, or 

 other causes, the arms are frequently drawn upwards so firmly 

 by the muscles at the top of the shoulders, that the pectoralis 

 major and latissimus dorsi cannot pull them down. When they 

 contract, therefore, their extremities are made to approach 

 by raising the ribs to which they are in part attached, and thus 

 they become muscles of forced inspiration. 

 The muscles of animal life are arranged, so that each one has 

 its antagonist, or opposing muscle. Thus, there are flexors to 

 bend the limbs, and extensors to straighten them, supinators and 

 pronators, elevators and depressors. The muscles, which are 

 very numerous, and like the bones, are said to be variously 

 estimated, from 368 by Chaussier, to 400 or more by other 

 writers, and producing by their single action a great variety of 

 movements, are yet combined together in pairs or much larger 

 numbers, so as to extend beyond computation the variety of 

 movements they are capable of producing. Thus the two mus- 

 cles already named, one of which, when acting separately, draws 

 the arm usually downwards and forwards, the other downwards 

 and backwards, when combined together draw it down in the 

 diagonal or middle line. 



The antagonism of the muscles is dependent upon their alter- 

 nate contraction : the shortened or contracted muscle, is re- 

 stored to its former length chiefly by the contraction of its an- 

 tagonist, but partly also by the resiliency of the cellular tissue 

 in its composition. They are also capable of acting to a certain 

 extent in unison, and thus give firmness and steadiness to the 

 limbs or other parts, and hold them in a fixed direction, as 

 occurs habitually in walking or standing, or pointing with the 

 arm. 



The antagonizing muscles do not appear to be equally 

 balanced in regard to power; thus the most usual attitudes, in 

 sleep, palsy or tetanus, where the muscles are uninfluenced by 

 the will, is the extended position for the back, flexion to the 

 arm in general, pronation to the fore arm, flexion to the lower 



