ELASTIC TENSION. 95 



ment of the muscles to the bones is the extension thus 

 effected. If the limb of a dead body is placed in the 

 position which it ordinarily occupied during life, and if 

 one end of a muscle is then separated from its point 

 of attachment, it draws itself back and becomes shorter. 

 The same thing happens during life, as is observable in 

 the operation of cutting the tendons, as practised by 

 surgeons to cure curvatures. The result being the same 

 during life and after death, this phenomenon is evi- 

 dently due to the action of elasticity. It thus appears 

 that the muscles are stretched by reason of their attach- 

 ment to the skeleton, and that, on account of their elas- 

 ticity, they are continually striving to shorten. Now, 

 when several muscles are attached to one bone in such 

 a way that they pull in opposite directions, the bone 

 must assume a position in which the tension of all the 

 muscles is balanced, and all these tensions must com- 

 bine to press together the socketed parts with a certain 

 force, thus evidently contributing to the strength of the 

 socket connection. When one of these muscles con-- 

 tracts, it moves the bone in the direction of its own 

 tension, but in so doing it extends the muscle which 

 acts in an opposite direction, and the latter, because of 

 its elasticity, offers resistance to the tension exerted by 

 the first muscle, so that as soon as the contraction of 

 the latter is relaxed the limb falls back again into its 

 original position. This balanced position of all the 

 limbs, which thus depends on the elasticity of the 

 muscles, may be observed during sleep, for then all ac- 

 tive muscular action ceases. It will be observed that 

 the limbs are then generally slightly bent, so that they 

 form very obtuse angles to each other. 



Not all muscles are, however, extended between 



