GLANDULAR STRUCTURES. 



the heart, it presents a marked notch, so that the recess is not 

 filled and the pericardium is uncovered. [983] 



Fissures and Lobes. The left lung is divided into two lobes, 

 upper and lower, by a deep fissure which penetrates nearly to 

 the hilus. This fissure begins at the posterior border, two 

 and a half inches below the apex, and runs, on the outer suf- 

 face, to just behind the anterior end of the base. The right 

 lung is divided into three lobes, upper, middle, and lower, by a 

 similar fissure which ends inferiorly somewhat farther out- 

 ward ; and by a second cleft which begins in the main fissure 

 at the posterior border, and runs horizontally over the outer 

 surface to the anterior border opposite the fourth costal 

 cartilage. [988] 



Root. This consists of the structures entering the hilus and 

 is enclosed by pleura ; it lies behind the superior vena cava on 

 the right side, and in front of the descending aorta on the left. 

 The chief structures of each root are the pulmonary vessels, 

 nerves, and lymphatics, bronchus, and the bronchial vessels 

 and glands. The bronchus lies behind the pulmonary vessels. 

 The pulmonary artery runs below the undivided part of the 

 bronchus on the right side, but crosses it to a higher level on 

 the left. The pulmonary veins lie at a lower level than the 

 artery and bronchus, but the upper vein is in front of the 

 artery. The right bronchus gives off two branches (of which 

 the upper is eparterial) to the upper and middle lobes, while the 

 main stem enters the lower lobe. The left bronchus sends a 

 large branch to the upper lobe, and then enters the lower lobe. 

 The right upper branch is eparterial, all the other branches are 

 hyparterial. [989] 



THE GLANDULAR STRUCTURES. 



Mammary Glands. One lies on each side of the front of 

 the thorax in the superficial fascia, over the Pectoralis major 

 and (slightly) Serratus magnus, and usually extending from 

 the second to sixth rib. At the summit is a projection (nipple) 



[139] 



