THE THYMUS GLAND.

Vessels and Nerves.-The arteries supplying the thyroid are the superior and inferior thyroid, and sometimes an additional branch (thyroidea media or ima) from the innominate artery or the arch of the aorta, which ascends upon the front of the trachea. The arteries are remarkable for their large size and frequent anastomoses. The veins form a plexus on the surface of the gland and on the front of the trachea, from which arise the superior, middle, and inferior thyroid veins, the two former terminating in the internal jugular, the latter in the innom-inate vein. The lymphatics are numerous, of large size, and terminate in the thoracic and right lymphatic. ducts. The nerves are derived from the middle and inferior cervical ganglia of the sympathetic. 

Surgical Anatomy.-The thyroid gland is subject to enlargement, which is called goitre. 

This may be due to hypertrophy of any of the constituents of the gland. The simplest (parenchymatous goitre) is due to an enlargement of the follicles. The fibroid is due to increase of the interstitial connective tissue. The cystic is that form in which one or more large cysts are formed from dilatation and possibly coalescence of adjacent follicles. The pulsating goitre is where the vascular changes predominate over the parenchymatous, and the vessels of the' gland are especially enlarged. Finally, there is exophthalmic goitre (Graves's disease), where there is great vascularity and often pulsation, accompanied by exophthalmos, palpitation, and 

rapid pulse. 

. For the relief of these growths various operations have been resorted to, such as injection 

of tincture of iodine or perchloride of iron, especially applicable to the cystic form of the disease, ligature of the thyroid arteries, excision of the isthmus, and extirpation of the whole or a part of the gland. This latter operation is one of difficulty, and when the entire gland has been removed the operation has been followed by a condition resembling myxredema. In removing the organ great care must, be taken to avoid tearing the capsule, as if this happens the gland-tissue bleeds profusely. The thyroid arteries should be Jig-atured before an attempt is made to remove the mass, and in ligaturing the inferior thyroids the position of the recurrent laryngeal nerve must be borne in mind, so as not to include it in the ligature. A large number of cases of what were formerly supposed to be goitre are now known to be cases of adenomatous enlarge-ment, where an adenoma, starting in one part of the gland, gradually spreads and involves the 

whole organ.