292 ELEMENTARY PHYSIOLOGY less. 



fibre is viewed out of the body, appear sharply defined, 

 like those of a glass rod of the same size ; but when the 

 fibre is observed in the living body, bathed in the lymph 

 which surrounds it, the outlines are not so sharply de- 



FlO. 88. — To ILLUSTRATE TllK STRI'fTtlRE OF A STRIATED MuSCULAR 



Fibre. 



A. Part of a muscular fibre (of a frog) seen in a nat\iral condition, d, 

 dim bands ; 6, bright bands, witli the granular line seen in manj' of 

 them ; n, nuclei and the granular protoplasm belonging to them, very 

 dimly seen. 



B. Portion of prepared mammalian muscular fibre teased out, showing 

 longitudinal portions of variable (1, 2, 3, 4) thickness ; 4 represents the 

 finest portion (fibrilla) which could be obtained ; d, dim bands ; 0, bright 

 bands, in the midst of each of which is seen the granular line g. 



fined. In neither case can any distinct line of demarc- 

 ation between a superficial layer and a deeper substance 

 be recognised. The fibre appears transversely striped, as 

 if the clear glassy substance were, at regular intervals 

 (Fig. 88, A, d), converted into ground glass, thus appear- 

 ing dimmer. Each of these "dim bands" is about 2/x 

 wide, and the clear space or "bright band" which 

 separates every two dim bands is of about the same size, 



