450 THE DUCTLESS GLANDS 



with the epithelial cells, and reach the zona fasciculata. Here 

 the capillaries are collected into thin-walled venules or sinusoids. 

 These vessels, after some anastomoses, form venous stems which 

 are continued, without further anastomosis, through the medulla 

 to the central veins. 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 abrrptly 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 impinge upon the 

 lumen of the capillary vessel (see Fig. 93, page 93). The capil- 

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

 there collected into small venules 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 fibres, which occur in 

 considerable abundance, but are nearly all disposed in the axis of 

 the vessel ; the circular muscle fibres are confined to a very thin 

 coat beneath the endothelium, or are often entirely absent. Fre- 

 quently, and especially in the central veins of the adrenal, the 

 coarse bundles of longitudinal muscle fibres project into the lumen 

 of the vessel in a somewhat rugose manner. Whenever two veins 

 unite to form a larger vessel, and at the junction of a central vein 

 with any of its branches, these protuberant muscular bundles are 

 especially prominent. Moreover, the author has frequently ob- 

 served anomalous vessels of a venous nature which arise in the 

 medulla, penetrate the cortex, and enter the venous plexus of 

 the capsule; and in these instances the same peculiar distribu- 

 tion of the muscle has been observed in the veins of the capsular 

 plexus. 



LYMPHATICS. The lymphatics of the suprarenal gland, 

 according to Stilling,* form rich plexuses in ttfe zona glomeru- 

 losa and in the medulla ; elsewhere they are less abundant. They 

 follow the course of the blood vessels and are especially well devel- 

 oped in the vicinity of the central veins. 



* Arch. f. path. Anat., 1887. 



