THORAX. 141 



vessels on its surface. The blood vessels of the lungs 

 are functional branches of the pulmonary artery and 

 nutritive divisions of the bronchial arteries and veins ; 

 the nerves come from the sympathetic and pneumo- 

 gastric; the lymphatics are arranged in superficial and 

 deep layers. 



Heart. — General view: Hollow muscle divided by 

 a longitudinal septum in two masses, and each of these 

 by a transverse groove in two others, forming four cav- 

 ities, two superior, the auricles, two inferior, the ven- 

 tricles. Situation : opposite the third and sixth ribs, 

 in front of the diaphragm. Form: conoid. Direction: 

 obliquely, backwards, downwards, and slightly from 

 right to left. Size and weight : ten and one quarter 

 inches long, seven and a lialf at its base from back- 

 wards forwards, and five to five and a half from side 

 to side ; the average weight is six and three-quarter 

 pounds. 



External aspect. — Yentricular mass: has two faces, 

 right and left, both divided by a super o-inferior fissure 

 in two portions, the posterior of which forms the left 

 ventricle. Connected through the pericardium to the 

 pleura and hmgs, this mass has two borders, one ante- 

 rior, obliquely backwards ; one posterior, almost verti- 

 cal. Its apex is formed by tlie left ventricle. Its base 

 has two arterial and two auriculo-ventricular openings. 



