MUSCULAR TISSUE 



45 



Fig. 16 — Striated 

 mxxscle fiber ; u, ter- 

 mination of muscle 

 substance; 71, nuclei. 



muscular tissue to consist of long fibers covered with a 

 transparent covering or sarcolemma, within which may be 

 made out several nuclei and two kinds 

 of bands or stricB. These striae appear 

 as alternate broad, dim stripes and 

 narrow, light stripes. Both these bands 

 are made of protoplasm called sarco- 

 plasm or muscle protoplasm. The 

 numerous nuclei indicate that a fiber 

 is a collection of several cells fused 

 together with a common wall or sarco- 

 lemma. 



Nonstriated muscular tissue. The 

 muscle layers of the 

 intestine (see Ex. 

 XXVII. and Fig. 17) 

 show us that this tissue consists of a mass 

 of spindle-shaped cells each containing a 

 single large nucleus surrounded by a mass 

 of protoplasm which is striated longi- 

 tudinally but not transversely. Around 

 each cell is a thin wall or membrane 

 similar to the sarcolemma. 



Muscle cells then may be described as 

 cells containing protoplasm, which is so 

 arranged that when it expands and con- 

 tracts the whole cell is shortened or ex- 

 tended. By massing cells of this nature 

 together this shortening and extension 

 is made to cause movement of the parts 

 attached. Evidently the extent of mo- 

 tion is also increased by this massing, the total short- 



FiG. 17 — Muscle 

 layer uf the in- 

 testine (unstria- 

 ted muscle cells) ; 

 n, nucleus of a 

 single cell. 



