THE PARATHYROID BODIES. 



1795 



cent, of cases) being normally one of the most vascular structures of the body. 

 They are most common in the exophthalmic form. (7) The tremor^ tachycardia, 

 ?in<^ protrusion of the eyeballs seen in Graves's disease in association with thyroid 

 enlargement have no satisfactory anatomical explanation, although the close relation 

 of the sympathetic nerve and middle cervical sympathetic ganglion to the inferior 

 thyroid artery, the distribution of their vasomotor fibres to the thyroid vessels, and 

 of other associated fibres to the ocular apparatus, and their possible central connec- 

 tion — "probably in the medulla" (Treves) — have been invoked to explain the phe- 

 nomena of this form of goitre. 



Operations on thyroid enlargements vary with the character of the latter. 



In the adenomatous and cystic varieties, after division of the capsule of the 

 gland, the tumor or the cyst may generally be shelled out with the finger or by blunt 

 dissection (enucleation). Under these circumstances only some superficial veins 

 may require ligation, although free bleeding may occur from the intrinsic vessels of 

 the gland. In most of the other varieties of goitre the greater part of the growth 

 should be removed (excision, thyroidectomy). This should always be partial, — 

 i.e., a portion of the gland should be left in place with sufiicient vascular connection 

 to insure its vitality. 



In excision the skin platysma and cervical fascia should be freely divided and 

 the sterno-hyoids and thyroids retracted or divided ; after its anterior surface has 

 been well exposed the growth is first loosened externally, — as it will be found fixed 

 above by the superior thyroid vessels, below by the inferior thyroids, and internally 

 by the isthmijs, — the vessels separately ligated, great care being taken to avoid the 

 recurrent laryngeal nerve when the ligature is applied to the inferior thyroid artery, 

 the posterior surface dissected from the larynx, trachea, and other underlying 

 structures, and the growth removed. 



Fig. 1514. 



THE PARATHYROID BODIES. ' 



These organs, the epithelial bodies of many authors, are small elliptical masses 

 situated near the thyroid, which formerly were mistaken either for accessory thyroids 

 or for lymphatic nodules. They arise from the posterior wall 

 of the third and fourth pharyngeal pouches, and thus differ 

 from the thyroid body in origin as well as in structure. They 

 are 6 or 7 mm. long, 3 or 4 mm. broad, and i. 5 or 2 mm. thick. 

 The length may be as much as 15 mm. They arc always 

 separated from the thyroid by the capsule. Most frequently 

 the parathyroids exist as two pairs on each side; their disposi- 

 tion, however, may be asymmetrical, in some cases as many 

 as four, in others none, lying on one side. The position of the 

 superior pair is the more constant and, according to Welsh,' 

 corresponds about with the level of the lower edge of the 

 cricoid cartilage. They usually lie against the posterior surface 

 of the lateral thyroid lobes, between the middle and the inner 

 border of this surface. The inferior pair is lower and more 

 anterior than the superior, their position being less constant. 

 Sometimes they lie against the side of the trachea near the 

 ends of the rings, under cover of the lower part of the thyroid 

 lobes; sometimes they are found in a corresponding relation to 

 the windpipe, but much lower, so as to have no relation with 

 the thyroid; occasionally they lie on the front of the trachea 

 below the thyroid. The surest means of locating the little 

 bodies are the minute parathyroid arteries, small twigs chiefly 

 from the inferior thyroids, to each one of which a parathyroid 

 body is attached. It is evident, therefore, that these organs 

 may be found on almost any aspect of the thyroid gland. 



Structure. — Each organ is invested by a thin fibrous capsule and subdivided 

 into ill-defined lobules by a few delicate septa which support the blood-vessels. 



'Journal of Anatomy and Physiology, vol. x.xxii., 1898. 



Thyroid and parathyroid 

 bodies viewed from behind ; 

 p^-,p-, right superior and in- 

 ferior parathyroids ; st, supe- 

 rior thyroid artery ; a, anasto- 

 mosis ; «, recurrent laryngeal 

 nerve. (Ginsburg.) 



