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HANDBOOK OF PHYSIOLOGY. 



meshed 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 

 corpuscles undergoing disintegration. 



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

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

 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 

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

 In certain animals its removal appears to produce a peculiar condition in 

 which mucin is deposited in its tissues. A similar condition, known as 

 Myxoedema, and Cretinism are closely associated with disease or removal 

 of the thyroid gland in the human subject. 



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 kid- 

 neys. 



FIG. 269. Vertical section through part of the cortical portion of supra-renal of guinea-pig, a, 

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

 cells of the latter, and also indicating the position of the blood-vessels, x (S. K. Alcock.) 



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

 tive tissue, which sometimes consists of two layers, sending in exceed- 

 ingly fine prolongations forming the framework of the gland. The 



