THE THYROID GLAND. The thyroid gland is classified with the thymus, suprarenal capsules. and pleen, und" 'h, head of du,t/", g/o"U-i. e., glana, which do not pa",,, an """a,y duct. From its situation in connection with the trachea and larynx, the thyroid body is usually described with those organs, although it takes no part in the func­tion of respiration. It is situated at the front and sides of the neck, and consists of two lateral lobes connected aCl'OSS the middle line by a narrow tran"verse portion, the isthmu8. The weight of the gland is soinewhat variable, but is usually about one ounce. It is somewhat heavier in the female, in whom it becomes enlarged during men­struation and pregnancy. The lobes are conical in shape, the apex of each being directed upward and outward as far as the junction of the middle with the lower third of the thyroid cartilage; the base looks downward, and is on a level with the fifth or sixth tracheal ring. 'I'he external or Superficial 8urface is convex, and covered by the skin, the superficial and deep £'1scia, the Sterno-mastoid, the anterior belly of the Omo­hyoid, the Sterno-hyoid and Sterno-thyroid muscles, and beneath the last muscle by the pre-tracheal layer of the deep fascia, which forms a capsule for the gland. The deep or internal surface is moulded over the underlying structures, viz., the thyroid and cricoid cartilages, the trachea, the inferior constrictor and posterior part of the Crico-thyroid muscles, the reSop}lagus (particularly on the left side of the nook), 'h, '"p";a, and inf,na, ,hy,a;d "''';'', and the "'n''On' laryngoal nerves, Its anterior border is thin, and inclines obliquely from above downward and inward toward the middle line of the neck, while the posterior border is thick and overlaps the common carotid artery. Each lobe is a bout two inches in length, its greatest width is about one inch and a quarter, and its' thickness about' three quarters of all inch.