48 



VEBTEBKATA : MAMMALIA. 



heart determines its course in the veins. The veins, in most cases, are 

 provided with valves, permitting the flow of blood towards the heart, 

 but preventing its re-flow in the opposite direction. 



The heart in the Mammals and in the Birds contains 

 four cavities a right auricle and right ventricle, and a left 



FIG. 56. 



Pulmonary artery. Aorta. 

 Vena cava superior. 



. Pulmonary veins. 



Pulmonary artery. 



Pulmonary veins. . =:.._ 



Eight auricle 



Tricuspid valve ... 



Inferior vena cava. 



Eight ventricle... --' 



Left auricle. 



Mitral valve. 



Left ventricle. 



Septum. Aorta. 



Theoretical Section of Heart of the highest Mammal Man. 



Carotid artery. FIG. 57. Carotid artery. 

 Jugular vein.._ \ Trachea. / Jugular vein. 

 Vein of the arm. "> \ 



Eight Lung.. 



Artery of the arm. 



Vein of the arm. 



Left Lung. 



Eight auricle.'"Vena cava'' Eight venV'-Aorta. "~Left ventricle, 

 inferior. tricle. 



Lungs, Heart, etc., of the highest Mammal Man. 



auricle and a left ventricle, the two cavities in the right 

 half being completely separated from the two cavities in 



