68 



CONTRACTILE ELEMENTS. 



envelopes of the primitive cells being represented by the 

 covering of the fibre, or sarcolemraa ; the cellular nuclei by 

 corpuscles, placed at intervals upon the inner surface of this 



covering; and the cellular con- 

 tents by the granular contents 

 of the fibre: the latter appear 

 to be formed from a liquid por- 

 tion, and from granulations (sar- 

 cous elements of W. Bowman) 

 which, being grouped in series, 

 either perpendicular, or parallel 

 with the axis of the fibre, give 

 us muscles with longitudinal or 

 transverse striaB, the latter form 

 being the most common (Fig. 17, 

 a and b). It is not unlikely that 

 other effects are due to the artifi- 



Pig. 17. Different appearances of c i a l mode of preparation. 

 striped muscle.* 



the most minutely examined, and we will, therefore, begin 

 our study of the muscles with this form. 



II. STRIATED MUSCLE. 



THESE muscles appear as clusters of fibres, remarkable on 

 account of their transverse striation. Histological analysis 

 shows this fibre not to be the simple element which it ap- 

 pears ; it is itself composed of longitudinal fibrils, exhibiting 

 small nodosities arranged in clusters, one above the other ; 

 the regular arrangement of the nodosities of the adjacent 

 fibrils in transverse series produces the striated aspect of the 

 fibre as a whole. (See Fig. 17, a, 5, c, d). Opinions differ as to 

 the nature of these nodosities. According to Ch. Robin, they 

 are caused simply by the appearance of points which are 

 alternately light and dark, and are themselves caused by a 

 difference in refraction in the different parts of the fibril ; 

 while Rouget supposes them to be produced by the spiral 

 twisting of the fibrillary filament, forming a helix, the coils 

 of which are more or less closely brought together accord- 



* a. Normal appearance of a recent primitive fasciculus, with its transverse 

 striae. 6, Fasciculus treated by dilute acetic acid (the nuclei showing more dis- 

 tinctly the nucleoli). c, Under the action of concentrated acetic acid the contents 

 escape at the extremity of the envelope (sarcolemma). d, Fatty atrophy. 

 (Virchow, "Pathologic Cellulaire.") 



