136 



VITAL FUNCTIONS. 



Fig. 86. 



The two hearts separated. The two hearts in the 

 natural state are joined together, but that the student 

 may the more clearly comprehend the two systems, 

 they are here represented separate, Fig. 86. 



In this plan, d repre- 

 sents the right auricle ; e, 

 the right ventricle ; k, the 

 left auricle ; /, the left 

 ventricle ; a, the aorta ; i, 

 the pulmonary veins ; f, 

 the pulmonary arteries ; 

 c, the vena cava ; b, the 

 ^ meeting of the small bran- 

 ches of the aorta, and ve- 

 na cava, and 7^, the meet- 

 ing of the pulmonary 

 veins and arteries. 



The circulation is as fol- 

 lows. The blood is con- 

 veyed by the vena cava, c, 

 to the right auricle, d, and 

 poured into the ventricle, 

 e 9 which contracting, throws it through the pulmonary 

 artery,/, to the lungs, where it is oxygenated, or purifi- 

 ed and made fit for general circulation. The pulmonary 

 veins then receive, and convey it to the left auricle, A, 

 by which it is transmitted to the ventricle, Z, which con- 

 tracting with great power, propels it to all parts of the 

 system through the aorta a. From the small branches 

 of the aorta, it is received into those of the vena cava, 

 by which it is transmitted to the right auricle, the point 

 where we commenced. In all the Mammalia and 

 Birds, this is the routine of the circulation. 



The two Hearts united. It only now remains to show 

 the two hearts of man united, that the pupil may observe 

 how they naturally exist as a single organ in external ap- 

 pearance. Fig. 87 represents the double heart, show- 





What are the two systems of circulation in quadrupsds and man 

 called 1 Describe the circulation in man. 



