340 THE SOLIDS. 



They differ also to a very considerable extent in form as 

 well as magnitude : thus, in a cross section and in a recent 

 state they are seen to be more or less angular and compressed, 

 but still preserving, in most cases, much of the character of 

 cylinders. In the dry condition this angularity is greatly 

 increased, and to this state of the fibres the representations 

 hitherto given chiefly refer. (See Plate XLII. fig. 5.) 



The fibres, both great and small, are, as already observed, 

 arranged in bundles or lacerti, of variable size ; those of the 

 same bundle run parallel to each other, and the different 

 bundles are separated, and yet held together by mixed fibrous 

 tissue. 



Examined with a moderate power of the microscope, each 

 fibre is seen to exhibit numerous transverse striae, which are 

 placed at tolerably regular distances from each other : some 

 fibres, also, and especially such as have been preserved in 

 spirit, present numerous fainter longitudinal striae. 



When viewed with a somewhat higher object glass, and 

 when each fibre has been torn into pieces by needles, its 

 entire bulk will be seen to be made up of a number of slender 

 threads of equal diameter, which present a distinct trans- 

 verse striation. 



It was formerly very generally supposed that the transverse 

 lines on the striped muscular fibre were produced by a fila- 

 ment which wound spirally around it : this notion is, doubt- 

 less, erroneous, as indeed it is now generally allowed to be. 



It has been observed that the fibrillae are themselves 

 marked with transverse striae : now it is not difficult to con- 

 vince oneself that the striation of the fibre is produced by the 

 striae of the fibrillae, the striae of one fibrilla corresponding 

 with that of another, and thus giving rise to a line which 

 extends entirely across the diameter of the fibre. 



The correctness of this explanation might have been easily 

 inferred from a knowledge of the composition of the striated 

 muscular fibre of banded fibrillae, and from the aspect of 

 the transverse line itself, which, when examined with a high 

 power of the microscope, does not present the appearance of 

 an uninterrupted and continuous line, such as would be pro- 



