CHAP. Til.] MUSCULAR SOUND. 183 



parts, are separated from one another by intervals of various lengths, 

 in which the fibre has either entirely given way, or is more or less 

 stretched and disorganized. These appearances are met with after 

 all contractility has departed ; they are the vestiges of the spasm 

 during life. Yet in other muscles, which have been likewise con- 

 vulsed, but not ruptured, they are not found. Their presence is, 

 therefore, the result of the rupture. They admit only of the fol- 

 lowing explanation : the contractile force has operated at the points 

 found contracted, and by its excess, the intermediate portions have 

 been stretched to laceration. Having once given way, the con- 

 tracted parts have become isolated, and can no longer have been 

 extended after the subsidence of contractile force; they conse- 

 quently retain the form and appearances they possessed, when sur- 

 prised, as it were, by the rupture, they have themselves produced, 

 of the intervening parts. 



Supposing, for a moment, that active contraction were an univer- 

 sal and equable act, and that, by the superior power of an antago- 

 nist, a weak muscle had been ruptured, the appearances resulting 

 would manifestly be entirely different from those now detailed. 

 The fibres beyond the ruptured point would have their transverse 

 stripes uniformly approximated. 



It may be concluded from the preceding facts, 1st. That 

 active contraction never occurs in the entire mass of a muscle at 

 once, nor in the whole of any one elementary fibre, but is always 

 partial at any one instant of time : 2nd. That no active con- 

 traction of a muscle, however apparently prolonged, is more than 

 instantaneous in any one of its parts or particles : and therefore, 

 3rd. That the sustained active contraction of a muscle is an act 

 compounded of an infinite number of partial and momentary con- 

 tractions, incessantly changing their place, and engaging new parts 

 in succession ; for every portion of the tissue must take its due 

 share in the act. 



Two phenomena yet remain to be mentioned, which, by admit- 

 ting of a satisfactory explanation on this view of the subject, give 

 strong testimony to its correctness. 



The first is the Muscular Sound, heard on applying the ear to a 

 muscle in action. It resembles, according to the apt simile of Dr. 

 Wollaston,* the distant rumbling of carriage-wheels; or rather, 

 perhaps, an exceedingly rapid and faint tremulous vibration, which 

 when well marked, has a metallic tone. It is the sound of friction, 



* Phil. Trans. 1811. 



