DIGESTION, CIRCULATION, AND ABSORPTION 283 



irregular pigment cells. If you find the blood moving in reg- 

 ular spurts in any of the tubes, note how often the " spurts " 

 take place. (These tubes lead from the heart, and are called 

 arteries.) 



FIG. 64. Capillary circulation in the web of a frog's foot ; a, b, small veins ; 

 d, capillaries showing corpuscles following one another in single series ; c, 

 pigment cells in the skin. 



2. Do the arteries remain of a uniform size ? If not, what 

 becomes of them as you trace in the direction the blood flows ? 

 (The tubes into which arteries divide are called capillaries, 

 and connect the arteries with tubes called veins that commonly 

 carry impure blood, and lead toward the heart.) 



3. How does the blood flow in a vein differ from that in an 

 artery ? 



4. Do you notice any disklike bodies (red corpuscles) in 

 the blood ? Are they numerous or few ? 



5. Look for minute colorless bodies (white corpuscles). 

 Conclusion. Sum up your conclusions regarding the circula- 



