1124 THE ORGANS OF VOICE AND RESPIRATION. 



of the gland. Baber has found in the lymphatics of the thyroid a viscid mate- 

 rial which is morphologically identical with the normal constituent of the vesicle. 

 Vessels and Nerves. The arteries supplying the thyroid are the superior and 

 inferior thyroid, and sometimes an additional branch (thyroidea media or ima) 



Vesicle. 



i ^v *r**~~. it \ i \.Vi:M / ,v 



Lymphatic vessel. 





\ 1. '' 



Vv -v V" 



Wall of gland-vesicle. 



FIG. 713. Minute structure of thyroid. From a transverse section of the thyroid of a dog. (Semi-diagram- 

 matic.) (Baber.) 



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 myxoedema. In removing 

 the organ great care must be taken to avoid tearing the capsule /K if this happens the gland- 

 tissue bleeds profusely. The thyroid arteries should be ligatured 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. 



THE THYMUS GLAND. 



The thymus gland presents much resemblance in structure to other glandular 

 organs, and is another of the organs which are denominated ductless glands. 



The thymus gland is a temporary organ, attaining its full size at the end of the 

 second year, when it ceases to grow, and gradually dwindles, until at puberty it 

 has almost disappeared. If examined when its growth is most active, it will be 



