8 



HAND-BOOK OF PHYSIOLOGY, 



capillary plexus and a large number of lymphatics. The nerves adhere 

 closely to the vessels. 



In the vesicles there are in addition to the yellowish glassy colloid 

 material, epithelium cells, colorless blood corpuscles, and also colored cor- 

 puscles undergoing disintegration. 



Function. There is little known definitely about the function of the 

 thyroid body. It, however, produces the colloid material of the vesicles, 

 which is carried off by the lymphatics and discharged into the blood, and 

 so may contribute its share to the elaboration of that fluid. The destruc- 

 tion of red blood-corpuscles is also supposed to go on in the gland. 



SUPRA-RENAL CAPSULES OR ADRENALS. 



These are two flattened, more or less triangular or cocked-hat shaped 

 bodies, resting by their lower border upon the upper border of the 

 kidneys. 



Structure. The gland is surrounded by an outer sheath of connec- 

 tive tissue, which sometimes consists of two layers, sending in exceedingly 



FIG. 258. Vertical section through part of the cortical portion of supra-renal of guinea-pig, a, 

 capsule; 6, zona glomerulosa; c, zona fasciculata; d, connective tissue supporting the columns of the 

 ceDs of the latter, and also indicating the position of the blood-vessels. <J3. K. Alcock.) 



fine prolongations forming the framework of the gland. The gland tissue 

 proper consists of an outside firmer cortical portion, and an inside soft 

 dark medullary portion. (1.) The cortical portion is divided into (Fig. 

 258 b) an external narrow layer of small rounded or oval spaces, the zona 

 glomerulosa, made by the fibrous trabeculse, containing multinucleated 



