MFL 



A. A striped or striated muscle-fibre, quickly contracting, 

 showing alternate dark and light bands. It is built up of very 

 delicate fibrils (M FL). It is stimulated by a nerve-fibre (\ F). 

 which divides into an end-plate (N E) on the contractile sub- 

 stance. A striped muscle-fibre is due to the great elongation of a 

 cell, with multiplication of nuclei (N), or to a fusion of elongated 

 cells. 



B. Three smooth or unstriped muscle-cells (M C), elongated 

 spindles, dovetailed into one another, each with a nucleus (N). 

 There may be longitudinal fibrillation. Smooth muscle-cells 

 are slowly contracting. They occur in such situations as the 

 wall of the food-canal, the wall of the bladder, the wall of the 

 arteries; and abundantly in sluggish animals, such as sea- 

 squirts. 



