CIRCULATION OF THE BLOOD. 



29 



What are its cavities? 



It is divided by a septum into 

 two cavities, not connected, the 

 right and left (Fig. 2). Each 

 of these in turn is subdivided 

 into two parts, the auricle and 

 the ventricle. The auricles are 

 thin-walled cavities, whose func- 

 tion is to receive the blood from 

 the veins and pour it into the 

 ventricles. The ventricles are 

 the most powerful portions of 



tVio TiPnrt miKsolp thp Ipff- hpino- Transverse Section of the Bullock's Heart in 



' le > tj em S the State of Cadaveric Rigidity : a, cavity 



much Stronger and thicker than of the left ventricle; b, cavity of the right 



the right ventricle. 



What is the capacity of these cavities ? 

 Auricles, about 4 oz. ; ventricles, about 6 oz. 



FIG. 3. 



\J 



Course of Blood through the Heart : a, a, vena cava, superior and inferior ; b, right ven- 

 tricle ; c, pulmonary artery ; d, pulmonary vein ; e, left ventricle ; /, aorta. 



What is the use of the valves? 



To allow the blood to pass in one direction only through the 

 heart (Fig. 4). 



