CIRCULATION OF THE BLOOD. 



53 



blood goes to the muscles of the legs when we walk, more to the brain 

 when we are studying, to the digestive organs after eating, etc. The 



Walls of Capillaries 



Tissues of Web 



Fig. 23. Part of Frog's Web (highly magnified). 



plain muscle fibers shorten at a much slower rate than the striated 

 fibers. They are also slower in relaxing. Since the plain muscles are 

 usually found in the walls of hollow organs such as the heart, blood 



