70 CONTRACTILE ELEMENTS. 



economy, especially the faculty of passing from the first to 

 the second form ; and, in seeking for the reason of this phe- 

 nomenon, we shall study, in the muscle, as we have already 

 done in regard to the cells in general, that most essential 

 property of all living elements, excitability or irritability. 



A. The Muscle, under Form No. 1. 



Elasticity. One of the most remarkable properties of the 

 muscle is its elasticity. 1 



By elasticity we mean that property of bodies by which 

 they are diverted from their primitive form, and return to it 

 as soon as the extending cause ceases to act. Different bodies 

 present great differences in this respect, and the elastic prop- 

 erties vary, according to whether the change is made with 

 more or less facility, and the return to the original form is 

 more or less complete. We say that the elasticity is perfect 

 when this return is perfect (an ivory ball, for instance) ; that 

 it is imperfect when the return is not complete (example, a 

 lump of dough) ; that the elasticity is great when the change 

 is made with difficulty, and the return is sudden (as with a 

 steel blade), and that it is slight when the change is easy, 

 and there is slight tendency to return to the original form 

 (example, a willow twig). 



The muscle, under form No. 1, may be said to be slightly 

 and perfectly elastic. In this example muscles are flabby, 

 and may be easily stretched, so that the arm, deprived of its 

 muscular envelope (directly after death), is no more readily 

 moved than when the muscles were in place; this proves 

 that in this state the muscles readily distend (slight elasticity), 

 and afterwards assume their original condition (perfect elas- 

 ticity). In the same way, the muscular bags (auricles, ven- 

 tricles, stomach) are so easily distended by any thing which 

 has a tendency to dilate their cavities, that their elasticity 

 can be compared only to that of a soap-bubble. 



This slight and perfect elasticity is not & purely physical 

 property of the muscle ; for it depends on the life and nutri- 

 tion, or at least on the chemical composition, of the muscle, 

 and this composition is directly under the influence of the 

 life of this element (circulation and innervation). When 

 the muscles have remained long in a state of inactivity, and 

 are, consequently, ill-nourished, they lose a portion of their 



1 See Hitter. " Des Proprietes Physiques du Muscle." These 

 de concours. Strasbourg, 1863. 



