THE VERTEBRATE BODY 



341 



We soon reach small capillaries that encircle an alveolus. We can 

 see the sac swell like a huge balloon as the air is inhaled and then par- 

 tially collapse as the air is exhaled. Our erythrocyte contacts the capil- 

 lary wall and, as the oxygen particles enter, it assumes a brilliant scarlet 

 hue. 



'—Renal 

 Abdominal 



External Jugular 



Infernal jugular 

 Subclavian 

 Precaval 

 Brachial 

 Sinus venosus 

 Post cava I 

 Musculocutaneous 

 Hepatic 



Spermatic 



Renal portal 



Sciatic 



Pelvic 



Femoral 



Fig. 23.9. The principal veins of the frog. 



We go back to the heart by way of the pulmonary vein, but this time 

 enter the left auricle. The frog has only one ventricle, so we next enter 

 the ventricle for a second time. This time we are on the opposite side 

 however; we are on the left side of the ventricle and the corpuscles on 

 the right side are all a dull red color, for they have come from the right 

 auricle, while those surrounding us are bright red. The opening to the 



