SUPRARENAL CAPSULES 377 



cortical substance is of a reddish brown color and is composed either of 

 closed tubes containing cells or of columns of cells surrounded with 

 delicate fibrous trabeculae. On making thin sections through the corti- 

 cal substance previously hardened in chromic acid and rendered clear 

 by glycerin, rows of cells are seen, arranged with great regularity, and 

 extending, apparently, from the investing membrane to the medullary 

 substance. The cells appear to be enclosed in tubes measuring y^ 1 ^ to 

 glfl- of an inch (25 to 80 /-t) in diameter. They are granular, with a 

 distinct nucleus and nucleolus and a variable number of oil-globules. 

 They measure TT ^ to T ^Q of an inch (14 to 25 /i) in diameter. Be- 

 tween the rows of cells of the cortical substance are bands of fibrous 

 tissue connected with the investing membrane of the capsule. 



Medullary Substance. The medullary substance is much paler and 

 more transparent than the cortex. In its centre are openings that mark 

 the passage of its venous sinuses. It is penetrated in every direction 

 by delicate bands of fibrous tissue, which enclose bloodvessels, nerves 

 and elongated closed vesicles containing cells, nuclei and granular mat- 

 ter. These vesicles, which are -^ of an inch (0.32 millimeters) long 

 and about ^^ of an inch (64 ^} broad, have been demonstrated in the 

 ox and in the human subject. The cells in the human subject are yrfcTF 

 to -y^Vo f an m h ( 1 5 to 2O /*) i n diameter. They are isolated with 

 difficulty and are irregular in form. The nuclei measure about g-g^F ^ 

 an inch (10 //.). The medullary substance is peculiarly rich in vessels 

 and nerves (see Plate IX, Fig. i). 



Vessels and Nerves. The bloodvessels going to the suprarenal 

 capsules are very abundant and are derived from the aorta, the phrenic 

 artery, the cceliac axis and the renal artery. Sometimes as many as 

 twenty distinct vessels penetrate each capsule. In the cortical substance 

 the capillaries are arranged in elongated meshes, anastomosing freely 

 and surrounding but not penetrating the tubes. In the medullary sub- 

 stance the meshes are more rounded, and here the vessels form a rich 

 capillary plexus. Two large veins pass out, to. empty on the right 

 side into the vena cava, and on the left, into the renal vein. Other 

 smaller veins empty into the vena cava, the renal and the phrenic 

 veins. 



The nerves are abundant and are derived from the semilunar 

 ganglia, the renal plexus, the pneumogastric and the phrenic. The 

 nerves probably pass directly to the medullary substance, but here their 

 mode of distribution is unknown. In the medullary substance, however, 

 there are two ganglia situated close to the central vein. 



Nothing is known of lymphatics in the suprarenal capsules, and the 

 existence of such vessels is doubtful. 



