4 2 THE FROG 



The hepatic portal vein receives branches which bring 

 blood from the stomach, intestine, spleen and pancreas. 



F. Review of the Blood-vascular System. Write in 

 your notebook answers to the following questions : 



Through what arteries must blood pass from the heart to 

 reach the lungs, the skin of the sides of the body, the liver, 

 the small intestine, the kidneys, the hind limbs ? 



Mention the veins (and other organs if any) through 

 which the blood must pass on its way to the heart from the 

 following parts : the lungs, the ikin of the sides of the body, 

 the small intestine, the hind limbs (two routes). 



How does the blood entering the sinus venosus from the 

 anterior venae cavse compare with that entering from the 

 posterior vena cava as regards: (i) oxygenation, (2) nutri- 

 tive material, (3) waste products? State reasons for your 

 answers. 



Before leaving the study of the blood- vascular system be 

 sure you have gained clear ideas concerning the following 

 points : The mode of action of the heart, the function of all 

 the valves, the mode by which oxygenated blood and 

 non-oxygenated blood are kept separate (consult Holmes' 

 Biology of the Frog, pp. 277 to 279), the general course of 

 the circulation, and the changes that occur in the blood in 

 the different parts of the body. Observe the general con- 

 formity of the venous system to the arterial and account for 

 the similarity. 



G. The Lymphatic System.- -Instead of a system of 

 tubes, as in the human body, the lymphatic system of the 

 frog consists of communicating spaces or sinuses, some of 

 which have been noticed. The lymph is kept in circulation 

 by the action of certain lymph hearts (see Holmes' Biology 



