290 SPECIAL ANATOMY. 



rounded lateral edges point out the direction of the heart from 

 right to left. e. Sulcus longitudinalis, that is, a shallow groove 

 which passes downwards from the basis as far as the apex in a 

 curved course and indicates the septum between the right and left 

 half of the heart, f. Sulcus circularis, a deep transverse groove 

 which marks out the boundary between the auricles and ven- 

 tricles. 



Measurements. Length =4| inches, 

 Breadth =3^ inches, 

 Thickness =2 1 inches, 

 Capacity =32 cub. inches. 



Weight. In male =9 ounces, 



In female =8 ounces, 5 drachms. 

 After the thirtieth year it always rather increases. 



1. The auricles, atria, are to be regarded as dilatations of the large veins, 

 the blood from which they receive, and pour it (through ostia venosa) into the 

 ventricles. They are situated at the most external portion of the basis cordis, 

 are nearly quadrangular, two inches high and broad, provided with thin walls, 

 and a blind, pocket-like appendage, auricle, auricula cordis, and separated 

 from one another by a partition (septum atriorum). 



The anterior surface is concave, without a longitudinal groove, covered 

 by Aorta and Art. pulmonalis. 



The posterior surface is convex, presents a longitudinal groove (near 

 it, to the right, the opening of the ven. cava infer., underneath, that of 

 the ven. magn. cordis [coronary vein] , and is separated by the aorta and 

 oesophagus only from the vertebral column. 



The superior extremity looks backwards and to the right, lies under 

 the bifurcatio trachea, presents a longitudinal groove, to the right side of 

 which lies the opening of Ven. cava superior, to the left are seen the four 

 openings of the four pulmonary veins. 



2. The ventricles, ventriculi cordis, give origin to their arteries, and force 

 the blood which they have received from the auricles into them. They are 

 situated below the sulcus transversus, form the middle and the apex of the 

 heart, and are provided with thick external walls, and a partition (septum 

 cordis), which separates the one from the other. Their anterior surface, par- 

 ticularly the part which lies to the right of the longitudinal groove, looks to- 

 wards the sternum, and lies, in large hearts, immediately behind it. 



528. The Cavities. 



1. Atrium dextrum, right auricle, caval dilatation, lies behind the third to 

 the sixth costal cartilage and the body of the sternum, rather covered by the 

 anterior border of the right lung. From its superior angle the right appendix 

 passes inwards and upwards, covering the commencement of the aorta. Its 



