254 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, 6).— 
The thyroid gland consists of two lateral lobes (6) and a 
median lobe or isthmus (7). Each lateral lobe (6) is an 
elongated, flattened, lobulated mass with round ends. It is 
Fic. 107.—PosITION oF THyMUS GLAND, FROM LEFT SIDE. 
a, heart; 4, aorta; ¢, cesophagus; @, thymus gland; ¢, lymphatic gland; /, left 
leas artery; g, internal mammary artery, /, cut ends of first rib; XZ, eleventh 
about two centimeters long and about one-fourth as broad. It 
lies at the side of the trachea (4), 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 thyroid has no duct. 
The Thymus Gland. Glandula thymus (Fig. 107, 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 (a), 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. 
