124 



THE LUNGS AND RESPIRATION. 



coid, just above the sternal notch, incision being made 

 through the cartilage. 



Extending up on either side of the upper trachea in 

 the neck are the two lobes of the thyroid gland, the 

 isthmus, which connects the lobes, covering the trachea 

 below anteriorly. The function of the gland is ob- 

 scure, but it has an internal secretion of great im- 

 portance in the metabolic processes. Its removal or 



Thyreoict cartilage 



Thyreoliyoiileus 

 Right common carotid artery 



Right internal jugular vei, 



Scalentti anterior 



Cricothyreoideus 



Fio. 48. The upper thorax of a child eight years old, 'showing the thyroid and 

 thymus glands. (Sobotta.) 



disease is followed by general disturbances of mind and 

 body. The injection of thyroid extract has proved 

 effective as treatment. In goiter the gland becomes 

 enlarged. The thymus gland lies below the thyroid 

 gland at birth, in front of and at the sides of the trachea, 

 and runs down behind the sternum. It is largest at 

 the end of the second year, after which it atrophies, 

 being almost absent at puberty. It, too, is ductless and 

 its function is not well understood. 



