262 SPECIAL HISTOLOGY. 



in experiments upon animals, on the average to f ths, or in powerful 

 muscles even to |ths. The contractile force of a muscle does not de- 

 pend, cceteris imribus, upon its length, but solely on its transverse sec- 

 tional area; that is to say, on that of all its primitive fasciculi, so that 

 a longer and a shorter muscle exert the same force, when the sura of the 

 transverse sections of all the fasciculi is the same in both. According 

 to the observations of Schwann and Weber, the elasticity of the muscles 

 diminishes at each contraction, and consequently the molecular motions, 

 called into play in them under the nervous influence, must be connected 

 with a change in their substance of an altogether peculiar kind, which, 

 however, can certainly only be regarded as a secondary effect. The 

 degree of contraction differs according to the amount of antagonism 

 with which it meets ; if the latter be sufficiently powerful, no true move- 

 ment of the limb takes place, that is to say, the points of origin and 

 insertion of a flexor muscle (for instance) do not approximate ; never- 

 theless, the fibres themselves contract to a certain extent, in consequence 

 of which the whole muscle becomes tense. This tension must be care- 

 fully distinguished from that dependent upon the muscular elasticity, 

 which is generally much less considerable. What has been termed the 

 "tone" — tonus — of muscles, does not in most cases depend upon con- 

 traction, but is an elastic tension ; I therefore hold, that the posture of 

 the body and the occlusion of the transversely striated sphincters during 

 sleep, has nothing to do with a contraction of the muscles, although such 

 contraction is indubitably requisite to bring the body into this posture. 

 In my opinion, during sleep, all the muscles (of course, with the excep- 

 tion of the respiratory) are at rest, being held in a state of tension, and 

 of antagonism to their opponents merely by their elastic force, and are 

 consequently in the condition of a muscle Avhen supported, in a person 

 in the waking state. As for instance, a biceps, when the arm is bent, 

 may immediately lose its tension if the arm be supported, so in the same 

 way may all other voluntary muscles ; only it must not be forgotten, 

 that such a condition of muscular rest may ensue upon all conceivable 

 degrees of contraction. Even the orbicularis oris, when contracted, may 

 be at rest and lose its vital tension. The mouth, nevertheless, will re- 

 main closed, for this reason, that although the elastic force, as always 

 after a contraction, will not fail to exert a certain degree of extension 

 upon it, it is unable to open the mouth, owing to its limited amount and 

 inability to overcome the weight of the lips. I do not believe in any 

 muscular "tone," if under that term be understood a long-continued 

 involuntary contraction (though at first excited by the will) ; but am of 

 opinion, that what has been most generally described under this name, 

 is merely an elastic tension, which has been confounded Avith the con- 

 traction upon which it has ensued. From all we know, the nerves are 

 incapable of exciting a long persistent contraction in the striped muscles, 



