THE THYROID GLAND 557 



bodies composed exclusively of medullary substance and indistinguish- 

 able from paraganglia; and (3) the true accessory (supernumerary) 

 suprarenals consisting of both cortex and medulla. These bodies are 

 widely distributed in the vicinity of the suprarenal, sometimes embedded 

 within its substance, sometimes in the kidney or even in the liver. 

 They vary in size from microscopic bodies to such with a diameter of a 

 centimeter or more. They are frequently found also in connection with 

 the genital system, a rather large representative being almost invariably 

 present in the space between the testis and the epididymis, and in the 

 broad ligament of the female close to the ovary, where it is known as 

 Marcliand's gland or Marchand's adrenal. 



II. THE THYROID GLAND 



The THYROID consists of a mass of glandular tubules or follicles, 

 supported by a connective tissue stroma and supplied with a thin but 

 dense fibrous capsule which closely invests the surface of each of its 

 lobes. 



The Connective Tissue Framework.--The capsule of the thyroid 

 consists of dense fibro-elastic tissue, from which trabeculae, containing 

 the larger blood-vessels, pass inward and produce an indistinct lobular 

 subdivision. A network of delicate fibers, among which are very few 

 if any elastic fibers, passes from the trabeculaB and invests the glandular 

 follicles, forming a delicate basement membrane for their epithelium. 

 Flint (1903) has shown that much of this interfollicular connective tis- 

 sue is of the reticular variety. In it are contained the smaller blood- 

 vessels and lymphatics. It also contains a few lymphocytes,, which are 

 scattered about in a diffuse manner. 



The FOLLICLES of the thyroid are ovoid saccules or short branched tu- 

 bules with frequent diverticula (Streiff, Arch. mikr. Anat., 1897). They 

 vary greatly in diameter and in the caliber of their lumen. Many of 

 them present scarcely any lumen; others, by their extreme size (100 to 

 200 >"), simulate small cysts. All follicles which possess any consider- 

 able lumen contain a peculiar acidophil substance, known as colloid, 

 which is apparently formed by the secretory activity of the glandular 

 epithelium lining the follicles. 



Colloid is a homogeneous or very finely granular substance which 

 stains readily with eosin, taking a very bright tint closely resembling 

 that acquired by the hemoglobin of the red blood cells. Frequently, 



