SECT. 85.] MUSCULAR SYSTEM. 1 57 



after being stretched, and, consequently, also tears more readily, 

 although the gracilis muscle can still support a weight of eighty 

 pounds without tearing. At the same time, the muscle is less ex- 

 tensible, more rigid, and less flexible ; or its elasticity is greater. 

 The phenomena of fatigue in the muscles are accordingly to be 

 distinguished from those occasioned by death. In the former, the 

 diminution of the elasticity takes place under the influence of the 

 nerves and during the contraction of the muscle itself, probably in 

 consequence of the altered molecular nutrition of the muscle, and 

 is, consequently, a vital phenomenon. In the latter, these influ- 

 ences have ceased, and the increase of the elasticity, which 

 occasions the well-known rigor mortis, is simply a physical phe- 

 nomenon, and is not to be confounded with increased tension 

 of the muscles, which, under vital influences, takes place during 

 their contraction contemporaneously with diminution of their 

 elasticity. 



The tendons are very strong, and but little elastic. They 

 contain, according to Chevreul, only 6203 of water in 100 parts, 

 considerably less, therefore, than the muscles; and consist prin- 

 cipally of a substance yielding gelatine ; yet they are much less 

 easily resolved into gelatine than other parts. 



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

 in their natural form, sometimes even, compressed, and the vital contraction 

 may be superadded in all of these three conditions. If a stretched muscle 

 so contracts that it does not assume its natural form, it will, upon remission 

 of the contraction, still be in a state of tension, and retract on being cut 

 through. If, on the other hand, a muscle contract when in its natural form, 

 it will become extended when the nervous influence ceases ; as, for instance, 

 the contracted heart, or an isolated muscle stimulated by galvanism. Ac- 

 cordingly, when we speak of the elasticity of muscles, not only their tension, 

 when they are extended, but also that in the compressed condition must be 

 taken into account, which latter appears to me of great physiological im- 

 portance, in as much as the extension of contracted muscles, as in the case 

 of the heart, or of muscles whose antagonists are paralysed, then becomes 

 intelligible. I do not admit the existence of the so-called tonus of the 

 muscles, if by that term is understood a long continuing contraction, main- 

 tained without the influence of the will, although originally excited thereby ; 

 and I am of opinion, that what has been designated under this name, is, for 

 the most part, only the elastic tension, which has been confounded with the 

 antecedent contraction which it succeeds (see my Mikr. Anat. II. i.). With 

 reference to the rigor mortis, two important facts have been quite re- 

 cently brought to light, viz., that it may be annulled by the injection of blood 

 {Broirn-Siquurd), and may take place in the living animal, when the supply 

 of blood is cut off from a group of muscles {Stannius). In the latter case, 

 the excitability of the nerves also disappears, and the normal conditions of 

 the muscles and nerves return on re-establishment of the circiUation. Accord- 



