268 



THE CIRCULATION". 



apex of the heart is constituted altogether by the point of the left 

 ventricle. 



Fig. 79. 



Fig. 80. 



HUMAN UK ART, anterior view. 

 a. Right ventricle. 6. Left ventricle. 

 c. Right auricle, d. Left auricle, e. 

 Pulmonary artery. /. Aorta. 



II UMAX Hi: ART, posterior view. 

 a. Right ventricle. 6. Left ventricle. 

 c. Right auricle, d. Left auricle. 



The different cavities of the heart and of the adjacent blood- 

 vessels, though continuous with each other, are partially separated 

 by certain constrictions. These constricted orifices, by which the 

 different cavities communicate, are known by the names of the 



Fig. 81. 



RIGHT AURICLE AND VENTRICLE; Auriculo-ventricular Valves open, Arterial Valves closed. 



auricular, auriculo-ventricular, and aortic and pulmonary orifices ; 

 the auricular orifices being the passages from the venas cavoe and 



