ANIMAL MECHANISM. 



clips, the reality of this movement of the wave 

 may he verified in. the living animal. 



When the wave appears in the muscle, it produces con- 

 traction. During the whole of its passage the contraction 

 continues, and when, having reached the end of the muscular 

 fibre, the wave vanishes, the contraction disappears with it. 



These facts resemble those which the microscope reveals in 

 living muscular fibre. Let a bundle of muscular fibres be 

 taken from an insect, and placed under the objective of the 

 microscope (the feet of coleoptera are well suited for this 

 purpose) ; we first observe the beautiful transverse striation 

 of these fibres, and then we perceive on their surface an uudu- 

 latory movement often alternating, which resembles the motion 

 of waves on the surface of water. Ou examining this 

 phenomenon more closely, we see that the transverse striio 

 of the fibre are, at certain points, very close together, which 

 is shown in the figure by a dilatation of the fibre. This 

 is the wave shown by the microscope ; the longitudinal con- 

 densation of the muscle at this point gives it greater opacity 

 than in the other portions (Fig. 0.) This opaque wave travels 



|.' K; c. Appearance prc'sentcd by a wave in muscular fibre. 



through the length of the fibre. In other words, the points 

 at which the stria> approach each other are not always the 

 same, the longitudinal condensation disappears in one place 

 whilst it is produced in the contiguous parts. 



Since the contraction of the muscle is accompanied by its 

 transverse dilatation, we may study the characteristics of 

 the motion produced in a muscle, according to this expansion. 



We have sncr l'-d in registering these changes in the 



volume of the muscle, as we have registered the changes 

 in its length. Under these conditions we might study 

 muscular action in man himself, because there is no need 

 of mutilation. 



Let us suppose a muscle held between the flattened ends of 



