GLANDIFORM BODIES CONNECTED WITH RESPIRATORY APPARATUS. 553 



and the lungs are the bronchi; the right bronchus is the shortest and wiriest, and has an almost 

 horizontal direction, entering the right lung at the fourth dorsal vertebra ; the left is longer 

 and less voluminous, and reaches the corresponding lung at the tifth vertebra. 



4. Lungs.— The lungs weigh about forty ounces. As in all animals, the right is more 

 voluminous than the left, and is divided into three lobes ; the latter has only two. The 

 inferior vena cava is not surrounded by pulmonary tissue : the principal lobes are partitioned 

 into lobules, which are visible on the surface, and on the limits of which are deposited, only in 



Fig. 333. 



LUNG OF THE SHEEP (INFERIOR VIEW). 



1, Right lung; 2, left luDg; 3, trachea; 

 4, heart ; 5, carotid arteries ; (5, posterior 

 vena cava. 



HUMAN LUNGS AND HEART (FRONT VlEW). 



Right ventricle; 2, left ventricle; 3, right auricle; 

 4, left auricle ; 5, pulmonary artery ; 6, right pul- 

 monary artery; 7, left pulmonary nrtery ; 8, liga- 

 ment of ductus arteriosus; 9, arch of aorta; 10, 

 superior vena cava ; 11, arteria innominata ; 12, right 

 subclavian vein, with the artery behind it ; 13, right 

 common carotid artery and vein; 14, left vena in- 

 nominata; 15, left carotid artery and vein; 16, left 

 subclavian vein and artery; 17, trachea; 18, right 

 bronchus ; 19, left bronchus ; 20, 20, pulmonary 

 veins; 21, superior lobe of right lung; 22, middle 

 lobe ; 23, inferior lobe ; 24, superior lobe of left lung ; 

 25, inferior lobe. 



the adult, a notable quantity of pigmentary matter, that gives the lungs the appearance of a 

 chess-board. There is nothing to be said respecting their intemul conformation and structure. 



The Glandiform Bodies connected with the Respiratory 

 Apparatus. 



1. Thyroid Body, or Gland (Fig. 334). 



The thyroid body consists of two oval lobes of a reddish-brown colour, 

 and is situated close to, and behind, the larynx, beside the two first rings of the 

 trachea. 



These two lobes, distinguished as right and left, appear at first sight to be 

 perfectly independent ; but close examination shows them to be united by an 

 intermediate portion (the isthmus), which passes across the anterior face of the 



