X.] SUMMARY. 301 



Che blood of the upper (anterior) end of the body 

 somes entirely from the left ventricle. 



The blood of the dorsal aorta passes to the yolk- 

 ac and allantois, and to all the hinder parts of the 

 )ody. It is brought back from the yolk-sac, from the 

 illantois, and to a certain extent from the intestines, by 

 he portal vein, part of the blood from which passes to 

 he inferior vena cava by the direct course (ductus 

 ^enosus), and part indirectly by the more circuitous 

 ourse of the capillaries of the liver and hepatic veins. 



The blood from the generative and urinary organs, 

 tnd from the hinder extremities, is brought back to the 

 leart by the vena cava inferior ; that from the upper 

 xtremities and head by the jugular, vertebral and 

 ving veins into the two venae cavse of the right and 

 eft side, and so to the heart. Of these three vense 

 avse, the right superior and the inferior join the 

 Luricle by a common entrance, but the left superior 

 las an entrance of its own. All of these open into 

 he cavity of the right auricle, but the opening of 

 he inferior vena cava is so directed (vide Chap. viii. 



263) that the blood carried by this vessel flows 

 ihiefly through the foramen ovale into the left auricle, 

 ^'he blood from the two superior vense cavse enters the 

 ight auricle only. Now the blood of the inferior 

 ena cava has been partly aerated by the allantois; 

 ,nd, since it is this blood which passing through the 

 eft auricle and ventricle is distributed to the third 

 Lortic arch, unmixed by any blood from the right ven- 

 ricle (the mixture with the blood from the fifth arch 

 eaching only as far as the fourth arch), it happens 

 jhat the blood which flows to the anterior extremities 



