586 



MOTION. 



round them, in slightly curved or wholly parallel lines. 

 Other, but generally more obscure striae, also pass 

 longitudinally over the tubes, and indicate the direction 

 of the filaments or primitive fibrils of which the substance 

 of each fibre is composed (fig. 153). 



The whole substance of the fibre contained within the 

 sarcolemma may be thus supposed to be constructed of 

 longitudinal fibrils a bundle of fibrils surrounded by the 

 sarcblemma constituting a fibre. 

 Fig. 154.* 



There is still some doubt regarding the nature of the 

 fibrils. Each of them appears to be composed of a single 

 row of minute dark quadrangular particles, called sarcous 



* Fig. 154. A. Portion of a medium-sized human muscular fibre, 

 magnified nearly 800 diameters. B. Separated bundles of fibrils equally 

 magnified ; a, a,- larger, and b, b, smaller collections ; c, still smaller ; 

 d, d, the smallest which could be detached, possibly representing a single 

 series of sarcous elements (after Sharpey). 



