MUSCLE. 347 



a state of contraction : these attempts do not appear to me to 

 be altogether satisfactory and successful. 



The earliest opinion formed in reference to muscular con- 

 traction supposed that, during contraction the fibres and 

 fibrillae of muscle are disposed in a zigzag manner, such 

 a disposition of the fibres of course having the effect of 

 materially shortening the muscle. (Plate XLIII. Jig. 5.) 



The advocates of this view seem to have overlooked 

 the fact that fibres thus disposed, having no fixed or direct 

 points from which to act, would have their power by such an 

 arrangement rather diminished than increased : this idea has 

 therefore been justly discarded, and an account of the nature 

 of muscular contraction, much more closely approximating 

 to the truth, substituted in its place. 



Mr. Bowman, who has written by far the best account of 

 muscular contraction which has yet appeared, discriminates 

 between passive and active contraction of muscle : the former 

 he conceives to be a uniform act, involving and affecting 

 equally the entire mass of the muscle: the latter, on the 

 other hand, he considers to be a partial act, implicating, first, 

 a particular part or parts of a fibre ; subsequently leaving 

 these, and advancing to other and neighbouring parts of the 

 same fibre. 



This view is founded principally upon the experiment de- 

 tailed below, made upon a fibre of the claw of a crab, which 

 still retained its contractility. " In an elementary fibre from 

 the claw, laid out on glass, and then covered with a wet lamina 

 of mica, the following phenomena are always to be observed. 

 The ends become first contracted and fixed. Then con- 

 tractions commence at isolated spots along the margin of 

 the fibre, which they cause to bulge. At first they only 

 engage a very limited amount of the mass, spreading into its 

 interior equally in all directions, and being marked by a 

 close approximation of the transverse stripes. These con- 

 tractions pull upon the remainder of the fibre only in the 

 direction of its length ; so that along its edge the transverse 

 stripes in the intervals are very much widened and dis- 

 torted. These contractions are never stationary, but oscil- 



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