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 cartilage. 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 they lie in a cleft in the gland and thereby escape recognition. They possess a separate capsule. They are supplied by a separate artery, the parathyroid, a branch of the inferior thyroid. This latter usually gives off two parathyroid arteries, one to each body. Ginsburg (Univ. Penna. Med. Bulletin, Jan., 1908) has demonstrated a free anastomosis with the vessels of the opposite side. In many cases it is practically impossible to avoid wounding or removing the parathyroids in operations - Halsted has suggested three means of avoiding their removal, viz.: (1) slice off and leave the piece of thyroid gland supposed to contain the parathyroids; (2) ligate the superior

Fig. 185.   Showing the parathyroid bodies and inferior thyroids, and a week or two later perform a subcapsular enucleation of the thyroid; (3) search for each parathyroid by following out the ramifications of the inferior thyroid artery   this is the best method of finding them in post mortem examinations.

Fig. 185. - Showing the parathyroid bodies and inferior thyroids, and a week or two later perform a subcapsular enucleation of the thyroid; (3) search for each parathyroid by following out the ramifications of the inferior thyroid artery - this is the best method of finding them in post-mortem examinations.