198 



STUDIES IN PHYSIOLOGY 



FIG. 91. A Portion of Two Striped 

 Muscle Fibers, highly magnified. 

 n = nucleus. 

 s = covering of fiber. 



If this bit of muscle is put on a glass slide in a drop of 

 water, teased apart with needles, and examined with the 



compound microscope, it is 

 found to be composed of tiny 

 threads lying side by side, and 

 held together by the thin sheet 

 of perimysium. Each of these 

 threads is a muscle fiber. Close 

 examination shows that each 

 fiber is marked by very minute 

 lines that run across it, and 

 give it an appearance resem- 

 bling that of a very fine file. 

 Because of this appearance, 

 voluntary muscle is also called 

 striped muscle. If the fibers 

 are properly stained, nuclei 

 appear here and there, showing that muscle, like all other 

 kinds of tissue, is made 

 up of cells. When a 

 muscle is made to con- 

 tract, each one of the 

 fibers, like the whole 

 muscle, becomes shorter, 

 thicker, and harder. 



Blood Supply of Mus- 

 cles. Fresh muscle is 

 deep red in color, and 

 this is due to the pres- 

 ence of a great quantity 

 of blood. If one finds 

 in the muscle the open- FlG> 92. Blood Vessels in a Piece of 

 ing of a large blood Striped Muscle, magnified 150 times. 



vessel and forces into it, ' cope ' 



by means of a syringe, a mixture of hot gelatin stained with 

 some coloring matter, each minute blood vessel is distended, 



