304 SECRETION 



circulation, is changed within the gland by some 

 unknown phenomena and secreted by the cells of 

 the ductless glands to be taken into the blood and 

 lymph direct, and thus aid in promoting the metab- 

 olism of the body. They possess no ducts. 



The Thyroid Gland. This is a very vascular organ, 

 situated at the front of the neck, overhanging the 

 upper rings of the trachea and laterally extending as 

 high as the oblique line on the alse of the thyroid 

 cartilage, and as low as 1 inch above the upper border 

 of the sternum, when the head is extended. It weighs 

 about 1 ounce; slightly heavier in the female. It 

 has three lobes two lateral connected by an isthmus ; 

 and one third or middle lobe. It is firmly attached to 

 the cricoid cartilage and posterior fascia of the trachea 

 by two lateral or suspensory ligaments and its lobes 

 and isthmus are enclosed within a fibrous capsule 

 derived from the pretracheal portion of the deep 

 fascia of the neck. 



The isthmus lies on the second and third ring of 

 the trachea, and measures about J inch in breadth 

 and depth. 



The functions of the thyroid are not thoroughly 

 understood. It is an established fact, however, that 

 when the gland is secreting more or less than the 

 normal quantity, changes in development arise as a 

 result of some physiologic disturbance interfering 

 with the general metabolism of the body; as cretinism, 

 a condition occurring in infants and children as a result 

 of a congenital absence or arrested development of the 

 gland; myxedema, a condition (occurring in adults) of 

 the skin in which it becomes thickened, giving rise to a 

 change in the patient's expression, due to the face becom- 

 ing broader, swollen, and flattened. The mind is dull, 

 the subject is almost idiotic as regards the mental 

 condition. Myxedema is due to atrophy or some 

 pathologic change taking place in the gland which 

 interfered with its normal secretion: removal of the 



