252 SPECIAL HISTOLOGY. 



their elasticity alters in a very remarkable manner : 1. During the con- 

 traction they become more extensible or less elastic, on which account 

 they exert a much less force by their contraction than would otherwise 

 be the case, had their elasticity remained unchanged, and the same as 

 in the inactive condition. 2. The elasticity of the active muscle, in one 

 and the same muscle, is extremely variable ; it continues to diminish as 

 long as it is in action, whence arise the phenomena of fatigue and loss 

 of power in the muscles (E. Weber). 



In the dead muscle, according to the same observer, the elasticity is 

 less perfect; that is to say, the dead muscle, when stretched, does not 

 altogether resume its pristine form, and consequently is more readily 

 torn, although such a muscle as the gracilis may still be capable of sup- 

 porting a weight of eighty pounds without breaking. But at the same 

 time it is also less extensible, more rigid, less flexible, or its elasticity 

 is greater. The phenomena of fatigue in the muscles are consequently 

 to be distinguished from those induced by death. In the former state, 

 the diminution of elasticity occurs during the influence of the nerves 

 and the contractions of the muscle itself, probably in consequence of 

 changed conditions in the molecular nutrition of the muscle, and is con- 

 sequently a vital phenomenon ; whilst in the latter case, innervation, 

 nutrition, and contraction have ceased, and the increase of elasticity, 

 which produces what is termed the rigor mortis, is a purely physical 

 phenomenon, and not to be confounded with the increased tension, which, 

 under the influence of life, takes place during the contraction of the 

 muscles, simultaneously with a diminution of the elasticity. 



The tendons are very firm, and but slightly elastic ; and contain, 

 according to Chevreuil, in 100 parts, only 62 03 of water, considerably 

 less therefore than the muscles. They consist principally of a substance 

 affording gelatin, although they are transformed with more difficulty 

 than other parts into that principle. 



In my opinion the muscles are sometimes in a state of tension, some- 

 times in their natural form, sometimes even compressed, and to all these 

 three conditions vital contraction may be superadded. If a muscle in 

 a state of extension contract, so as not to assume its natural form, it 

 will still be in a state of tension after the remission of the contraction, 

 arid if divided will retract. On the other hand, if a muscle in its 

 natural form contract, it will, after the cessation of the nervous influence, 

 immediately become extended ; as, for instance, the contracted heart, 

 or an isolated muscle excited by galvanism. Consequently, when we 

 speak of the elasticity of muscles, their tension, not only when they 

 are extended, but also in the compressed condition, must be considered ; 

 and this appears to me of some physiological importance, as in this way 

 the extension of contracted muscles (heart), and of muscles whose 



