66 



PHYSIOLOGY FOR BEGINNERS 



which leave the muscle in the same way. Running near the 

 blood-vessels are also nerves which go to the muscle fibres. 



FIG. 31. Capillaries of striated muscle. 

 A. Seen longitudinally a, small artery ; b, small vein. 

 />. Muscle fibres cut across with capillaries between them a, cut ends of muscle 



fibres ; /, capillaries filled with dark material injected into them ; c, parts of 



capillaries not filled with injection material. 



All muscles attached to bones, the skeletal muscles as they 

 are called, consist of striated muscle fibres. 



Plain Muscular Tissue. The walls of the alimentary 

 canal, of the arteries, of the bladder, and several other organs 

 contain muscle fibres which are not striated, and are therefore 

 called plain muscle fibres. The fibres of plain muscular tissue 

 are not more than T ^th of an inch in length, being very much 

 smaller than striated fibres. Each is a spindle-shaped cell, a 



FIG. 32. A plain muscle fibre. 

 f, cell substance ; , nucleus ; />, granular cell substance near the nucleus. 



fibre-cell, containing a long oval nucleus. The cell substance 

 is granular round the nucleus, and often shows a longitudinal 

 fibrillation, but there is no transverse striation. The fibre 

 has no sarcolemma, but several fibres are dovetailed into one 



