2 54 THE VISCERA. 



is broadest at the caudal lobe of each lung. Each pulmonary 

 ligament is double, being formed of two sheets of the pleura. 



The Thyroid Gland. Glandula thyreoidea (Fig. 96, e). — 

 The thyroid gland consists of two lateral lobes (6) and a 

 median lobe or isthmus (7). Each lateral lobe (c) is an 

 elongated, flattened, lobulated mass with round ends. It is 



Fig. 107. — Position of Thymus Gland, kkom Left Side. 



(7, heart; b, aorta; <r, cesoijhagus; d, thymus gland; e, lymphatic gland; f, left 

 subclavian artery; g, internal mammary artery. /, cut ends of first rib; XI, eleventh 

 rib. 



about two centimeters long and about one-fourth as broad. It 

 lies at the side of the trachea (-i), dorsad of the lateral margin 

 of the sternohyoid muscle. Its cranial end is at the level of 

 the caudal border of the cricoid cartilage. The isthmus (7) 

 is a delicate band two millimeters wide which connects the 

 caudal ends of the two lateral lobes. It passes ventrad of the 

 trachea and in close contact with it. The th}'roid has no duct. 

 The Thymus Gland. Glandula thymus (Fig. loy, d). — 

 The thymus gland is best developed in young kittens ; in the 

 adult cat it has partly or almost completely degenerated. It is 

 an elongated, flattened organ, of a pinkish-gray color, which lies 

 in the mediastinal cavity, between the two lungs and against 

 the sternum. It extends caudad as far as the heart («), over- 

 lying the pericardium at its posterior end. At its cranial end 

 it projects, when well developed, a short distance (about one 

 centimeter) outside of the thoracic cavity into the neck region. 

 The caudal end is forked, and the left lobe thus formed is 

 usually larger than the right. The cranial end may also show 

 indication of a division into two lobes, but this is frequently not 

 the case. 



