STRIATED MUSCULAR FIBRE. 

 Fig. 250. 



393 



Fragments of striated muscular fibres, showing a cleavage in opposite directions. (Magnified 300 

 diameters.) 1. Longitudinal cleavage. The longitudinal and transverse lines are both seen. Some 

 longitudinal lines are darker and wider than the rest, and are not continuous from end to end ; this 

 results from partial separation of the fibrillae. 6. Fibrillje separated from one another by violence 

 at the broken end of the fibre, and marked by transverse lines equal in width to those on the fibre. 

 7, 8, represent two appearances commonly presented by the separated single fibrillae (more highly 

 magnified). At 7, the borders and transverse lines are all perfectly rectilinear, and the included 

 spaces perfectly rectangular. At 8, the borders are scalloped, the spaces bead-like. When most 

 distinct and definite, the fibrilla presents the former of these appearances. 2. Transverse cleavage. 

 The longitudinal lines are scarcely visible. 3. Incomplete fracture following the opposite surfaces 

 of a disk, which stretches across the interval and retains the fragments in connection. The edge 

 and surface of the disk are minutely granular, the granules corresponding in size to the thickness of 

 the disk, and to the distance between the faint longitudinal lines. 4. Another disk nearly detached. 

 5. Detached disk more highly magnified, showing the "sarcous elements." 



nomenon. The largest and the smallest fibres are sometimes found 

 side by side. 



Each striated fibre consists of two, distinct por- 

 tions : first, the my olemma ; and, secondly, the my- 

 oline. 



1. The myolemma 1 is the envelop containing 

 the myoline. It is merely a tube, closed at both 

 ends, of simple membrane (Fig. 251); in or un- 

 derneath which (for this point is not yet settled) 

 nuclei are brought into view by acetic acid. (Fig. 

 254.) Kolliker maintains that it is not an albu- 

 minous compound, but is at least similar to elastic 

 tissue. Certainly it may be proved to be elastic, 

 and to fit closely upon its contents, in the normal 

 state. 2 



Fig. 251, 



Myolemma of a torn 

 muscular fibre of the 

 skate. 



1 From /uD? , muscle, and xl^a, coat or sheath. It is also, less accurately, named 

 sarcqlemma, by Kolliker and others. &* &&********* ^S^ 



2 It should be here remarked that Drs. Busk and Huxley deny the existence 

 the myolemma as a distinct structure ; affirming that it is merely the outer portion 

 of the matrix containing the fibrillae. 



