STRIATED OR STRIPED MUSCLE. 61 



unbranched,but in occasional situations they branch and anasto- 

 mose. Each cell has many oval nuclei, arranged with their long 

 axis longitudinal to the cell, situated in mammals just under- 

 neath the sarcolemma. The body .of 

 the cell under moderate magnification FIG. 27. 



exhibits characteristic transverse striae 

 or stripes, consisting of delicate alter- 

 nately dark and light lines. 



The fibres are arranged parallel to 

 one another, with overlapping ends. Portiou oi str 

 They are grouped in bundles or fas- 

 ciculi, all of which bound together in fibrous sustentacular 

 tissue make up an entire muscle. The connective tissue 

 surrounding and enclosing the entire muscle is called the epi- 

 mysium; that enveloping the separate fasciculi is called the 

 perimysium ; while the delicate and scanty connective tissue 

 within the fasciculi among the individual muscle-cells is the 

 endomysium. 



The sarcolemma of each fibre is connected with the endo- 

 mysial tissue, and through this with the tendon. Thus each 

 cell when it contracts exerts more or less direct traction on 

 the tendon. The muscle-fibres are richly supplied with blood 

 by a capillary network in the endomysium. On the surface 

 of each fibre is a flattened nerve-terminal. 



The minute structure of striated muscle is very difficult to 

 make out and has not been satisfactorily determined, and 

 authorities are not agreed in their interpretations of the ap- 

 pearances presented. 



The appearance of cross-striation is produced by alternating 

 dark and light discs or segments in the substance of the 

 muscle-cells. By treatment with weak acids these segments 

 can be separated from one another in the form of transverse 

 discs. The individual fibres also exhibit a longitudinal striation 

 as well as transverse, and by treatment with alcohol and teas- 

 ing can be broken up into fine longitudinal fibrillce ; these 

 fibrillse are arranged in bundles, called fields of Cohnheim. 

 The protoplasm of the muscle-cell is made up of two parts, 

 a dark sarcous substance (" anisotropic," or doubly refracting) 

 and a colorless, hyaline, probably semifluid substance (" iso- 

 tropic," or singly refracting), sometimes called sarcoplasm. 



