TISSUES OF SPECIAL FUNCTION. 93 



sents both longitudinal and transverse striations, the latter much coarser 

 and prominent than the former. It must suffice us to consider this con- 

 tractile substance as made up of a number of prismatic bodies, 

 " sarcous elements/ 7 which are arranged end to end to form col- 

 umns, sarcostyles, extending parallel to each other, from one end 

 of the cell to the other. The sarcous elements of all the sarcostyles 

 lie in planes perpendicular to the long axis of the cell. It is, 

 therefore, possible to separate the contractile substance into a 

 number of fibre-like columns (sarcostyles, Fig. 65), made up of sar- 

 cous elements attached at their ends, or to split it transversely into 

 disks composed of sarcous elements lying side by side. Between 

 the sarcous elements is a substance which has received the name 

 " sarcoplasm." 



The contractile substance is enclosed in a thin, homogeneous mem- 

 branous envelope, called the " sarcolemma." The nuclei of the cell lie 

 immediately beneath the sarcolemma, between it and the contractile 

 substance, and are surrounded by a small amount of unmodified 

 cytoplasm. 



The muscle-fibres lie parallel to each other and to the general 

 direction of the muscle which they compose, and are separated by 

 loose areolar tissue, containing their vascular and nervous supplies. 

 When seen in cross-section they are circular or polygonal in form, 

 and the cut surface of the contractile substance appears crowded 

 with small polygonal areas, the sections of the sarcous elements, 

 between which is the sarcoplasm. Where the nuclei are included 

 in the section they appear somewhat flattened and lie at the edge 

 of the contractile substance, where a thin zone of cytoplasm may 

 sometimes be detected around them. The sarcolemma which lies 

 outside of these constituents of the cell is so thin that it can rarely 

 be distinctly seen. 



The muscle-fibres are in close contact at both ends with the dense 

 fibrous tissue of the tendons attached to the muscle. 



