324 



DETAILED SYNTHESIS. 



which, in case of the right auricle, blood can flow back 

 if much force is exerted; but in case of the left auricle, 

 none can flow backward, or the lungs might be endan- 

 gered. 



922. THE VENTRICLES ARE ALSO SIMILAR, the right 

 being a little more capacious, and its walls thinner, than 

 the left. 



923. THE INNER SURFACE OP THE VENTRICLES is 

 smooth ; at the same time it is uneven, many bundles of 

 fibres (columnce carnce) extending across the cavity, 

 some of them connected with the points of valves, as 

 shown at 9, Fig. 213. 



FIG. 213. 



Fig. 213, heart, 

 the front view; 



I, right, 2, left, 

 or systemic ven- 

 tricle, with por- 

 tion removed; 3, 

 R. auricle; 4 L. 

 auricle; 5, artery 

 opening from 2 ; 

 6, 7, 8, tricuspid 

 valves, connect- 

 ed by muscles, 9, 

 to inner surface 

 of heart; 10, bi- 

 cuspid valves ; 



II, semilunar 

 valves opening 

 into 11, artery, 

 leading to lungs 

 (pulmonary). 



922. Are - ? 923. What said of - ? 

 ing into nrtery callwl soinilun:ir ? 



Describe Fig. 213. Why are valves open- 



