156 MUSCULAR SYSTEM. [sect. 85. 



like that of the blood, becomes bright red on exposure to the air, 

 and still more in oxygen. It is readily extracted by water, but 

 not by salts, and this fact, viz., the effect of altered concentration 

 of the liquid with which the muscles are saturated, may seem to ex- 

 plain the readiness with which muscles change colour in disease. 



The muscles, although softer and more easily torn than the 

 tendons, have, nevertheless, a considerable degree of tenacity, 

 especially during life, and a certain degree of elasticity. During 

 life, as E. Weber justly observes, they are, even when not acted on 

 by the nerves, for the most part not in their natural form, but in a 

 state of tension, and exert an elastic force, like stretched cords. This 

 is most convincingly demonstrated by the experiment of bringing 

 the limb of an animal into a state of extreme flexion, and after 

 section of the nerves dividing the tendons of the extensor muscles, 

 on which they retract to a considerable degree. This tension of 

 the muscles is very various, according to the position of the 

 limbs. It is slight when the body reposes with the limbs in a 

 semi-flexed position; less or =0 when a muscle rests after it has 

 powerfully acted upon a limb ; greater and greatest when its 

 antagonists exert their utmost possible action. According to E. 

 Weber, the living but inactive muscles may be compared to 

 caoutchouc, in as much as like that substance they possess a 

 high degree of elastic extensibility, or in other words, a weak but 

 very perfect elasticity, as may be easily observed in the muscles 

 even of dead animals, when they are. alternately stretched and 

 allowed to retract. The elasticity of the muscles being so small 

 in amount, they oppose no obstacle to the motion of the limb; 

 and because it is so perfect, they shrink again to their previous 

 form and length after the greatest extension. This is also shown 

 when the abdominal muscles have been extended in pregnancy 

 and in pathological conditions. When the muscles are in action, 

 their condition as to elasticity becomes altered in a very remark- 

 able manner; 1, the muscles, during their contraction, become 

 more extensible or less elastic ; on which account they exert a 

 much less force in contracting, than would be the case if their 

 elasticity remained the same as when in a state of inaction ; 2, 

 the condition of elasticity during muscular action, is very various 

 in one and the same muscle ; it becomes progressively less during 

 the continuance of action, which is the cause of the apparent 

 exhaustion and loss of power which result. In dead muscles, 

 according to E. Weber, the elasticity is not so perfect, i.e., the 

 dead muscle does not entirely reassume its former condition 



