THE BLOOD AND ITS CIRCULATION 



373 



oxidized to release energy, and is stored for that purpose. The sugar 

 that becomes glycogen is carried to the liver directly from the walls of 

 the stomach and intestine, where it has been absorbed from the food 

 there contained. From the liver, blood passes directly to the right 

 auricle. The portal circulation, as it is called, is the only part of the 

 circulation where the blood passes through two sets of capillaries. 



Problem XLIX. A study of the circulation of the blood. 

 (Laboratory Manual, Prob. XLIX.} 



Circulation in the Web of a Frog's Foot. If the web of the foot 

 of a live frog or the tail of a tadpole is examined under the com- 

 pound microscope, a network of blood vessels will be seen. In 

 some of these the corpuscles are moving rapidly and in spurts; these 

 are arteries. The arteries lead into smaller vessels hardly greater 

 in diameter than the width of a single corpuscle. This network of 

 capillaries may be followed into larger veins in which the blood 

 moves regularly. This illustrates the condition in any tissue of 



ft. 





Capillary circulation in the web of a frog's foot, as seen under the compound 

 microscope, a, 6, small veins; c, pigment cells in the skin; d, capillaries in 

 which the oval corpuscles are seen to follow one another in single series. 



