THE NECK. 165 



carotid just above the bifurcation. It rises almost to the greater horn of the hyoid 

 bone and then descends to the thyroid gland, which reaches to the level of the oblique 

 line on the thyroid cartilage; it supplies the upper portion of the gland, particularly 

 the anterior portion, but also sends a branch down the posterior surface. The 

 vessels crossing the median line, contrary to what is often the case in the arteries of 

 the lip and even the scalp, are very small. The superior thyroid is superficial and 

 presents no special difficulty in ligation. The vein runs beneath it on its course to 

 the internal jugular. The inferior thyroid artery, a branch of the thyroid axis, 

 crosses behind the common carotid artery about the level of the seventh cervical 

 vertebra, about on a line with the lower edge of the isthmus. It enters the gland 

 from the side and not from below and ramifies on its posterior surface often as a 

 single large trunk beneath the capsule giving off branches to the parenchyma. 

 Usually it is in front of the recurrent laryngeal nerve, but the middle cervical gan- 

 glion of the sympathetic lies on it. Sometimes the artery breaks into branches before 

 it enters the gland. In such cases the recurrent laryngeal nerve may run between 

 these branches and so be injured in removing the gland. 



The thyroidea ima artery when present enters the gland from below, coming up 

 on the trachea usually from the innominate, in which case the innominate is apt to 

 come off more to the left side and so bring the common carotid closer to the trachea 

 than usual. It may also spring from the aorta or from the right carotid artery. 



The Veins. There are three sets of veins, a superior, a middle, and an inferior 

 thyroid, and, as Kocher has pointed out, an accessory thyroid between the middle 

 and inferior ones. The veins ramify under the capsule and form a plexus, which 

 in goitre is much enlarged and communicates freely across the median line at the 

 upper and lower portions of the isthmus. The superior and middle thyroids pass 

 outward to empty into the internal jugular. Still lower is the accessory inferior thy- 

 roid, which may empty into the internal jugular, as do the two above it, or it may pass 

 down, as does the inferior thyroid vein, and empty into the innominate. The inferior 

 thyroid vein does not follow the artery of the same name but with its fellow of the 

 opposite side passes directly downward in front of the trachea to empty into the 

 innominate vein. Its importance in operations on the trachea has already been alluded 

 to in speaking of tracheotomy. 



In removing the gland the superior thyroid artery is found at the upper outer 

 angle, the ligature should be placed sufficiently far out to include the branch to the 

 posterior surface of the gland. In ligating the inferior thyroid arteries they are to 

 be sought at the lower portion of the sides of the gland and are to be ligated either 

 close to the gland or isolated by pulling the carotid artery outward, and tied as they 

 make the bend at the edge of the anterior scalene muscle. Between these two 

 points lies the recurrent laryngeal nerve, usually behind the artery. Halsted advises 

 that each separate branch be ligated as it enters the gland to avoid those supplying 

 the parathyroids. The gland is covered by the omohyoid, sternohyoid, and sterno- 

 thyroid muscles. If these cannot be drawn aside they should be divided near their 

 upper ends in the same manner as already advised in the case of division of the 

 sternomastoid in removing tuberculous nodes. The sternomastoid muscle will have 

 to be drawn outward. 



The internal jugular vein often overlaps the common carotid artery, reaching 

 sometimes even to its inner side, so that the position of the artery is not a sure guide 

 to the location of this vein. 



When a goitre dips behind the sternum the presence of the left innominate 

 vein should not be forgotten. 



THE PARATHYROID BODIES. 



The parathyroid bodies are usually four in number, but rarely there may be five 

 or six. They are 6 to 7 mm. long, 3 to 4 mm. broad, and 1.5 to 2 mm. thick. The 

 most constant site of the superior parathyroid is at the middle or junction of the upper 

 and middle thirds of the posterior edge of the thyroid gland opposite the cricoid carti- 

 lage. The lower parathyroid is near the lower pole, but may be below it. They are 

 small brownish bodies in the meshes of the loose connective tissue forming the outer 

 capsule of the gland. Often they are quite distinct from the gland, but sometimes 



