THE SUPRARENAL GLANDS 555 



plexus through tho intercellular reticulum of the zona fasciculata, where 

 they arc in intimate relation with the epithelial cells, and reach the zona 

 reticularis. Here the capillaries are collected into thin-walled venules 

 or sinusoids. These vessels, after sonic anastomoses, form venous steins 

 \\hich arc continued, without further anastomosis, throughwfrhe medulla 

 to the central \cins. The venules of the cortex possess no walls other 

 than their endothelium. 



The medullary arteries are also derived from the capsular plexus. 

 They penetrate the cortex, and at the border of the medulla abruptly 



FIG. 481. RECONSTRUCTION OP A DOG'S ADRENAL. 

 a, arteries; v, vein. X 25. (After Flint.) 



terminate in a plexus of capillary vessels which lie in the connective 

 tissue stroma and come into intimate relation with the medullary cells. 

 These vessels possess extremely thin walls, their endothelium often being 

 in direct contact with the adjacent epithelium, whose cells frequently im- 

 pinge upon the lumen of the capillary vessel (see Fig. 481). The capil- 

 lary plexus pervades the entire medulla, its vessels being here and there 

 collected into small veuules which unite to form the central veins. 

 These form two, or sometimes four, main stems (Flint) which make 

 their exit at the hilum and enter the lumbar or renal vein, or, on the 

 right side, enter the inferior vena cava. 



All of the efferent veins of the adrenal are characterized by a peculiar 

 distribution of their smooth muscle fibers, which occur in considerable 

 abundance, but are nearly all disposed in the axis of the vessel; tho 



