480 SECRETION. 



one to three, and in the adult, as one to twenty-three. It was asserted by some of the 

 older writers, that the capsules are larger in the negro than in the white races, but 

 Meckel states that, although he had observed this in a negress, he saw nothing of it in 

 dissecting a negro. This observation did not have much significance at that time ; but 

 since it has been supposed that the suprarenal capsules have some function in connection 

 with the formation of pigment, authors have quoted it as important. 



The color of the capsules is whitish-yellow. They are completely covered by a thin, 

 fibrous coat, which penetrates their interior, in the form of trabeculaB. Upon section, 

 they present a cortical and a medullary substance. The cortex is yellowish, from ^ to 

 T ^ of an inch in thickness, surrounding the capsule entirely, and constituting about two- 

 thirds of its substance. The medullary substance is whitish, very vascular, and is 

 remarkably prone to decomposition, so that it is desirable to study the anatomy of these 

 bodies in specimens that are perfectly fresh. 



Structure of the Suprarenal Capsules. 



Cortical Substance. The cortical substance is divided into two layers. The external 

 is pale-yellow, and is composed of closed vesicles, rounded or ovoid in form, containing 

 an albuminoid fluid, cells, nuclei, and fatty globules. This layer is very thin. The greater 

 part of the cortical substance is of a reddish-brown color and is composed of closed tubes. 

 On making thin sections through the cortical substance previously hardened in chromic 

 acid and rendered clear by means of glycerine, numerous rows of cells are seen, arranged 

 with great regularity, and extending, apparently, from the investing membrane to the 

 medullary substance. On studying these sections with a high magnify ing-power, it is 

 evident that the cells are enclosed in tubes measuring from ToVfr to ^ir f an * ncn m 

 diameter. The cells are granular, with a distinct nucleus and nucleolus, and a variable 

 number of oil-globules. They measure from yy 1 ^ to T ^ 7 of an inch in diameter. Be- 

 tween the tubes of the cortical substance, are bands of fibrous tissue, connected with the 

 covering of the capsule. 



Medullary Substance. The medullary substance is much paler and more transparent 

 than the cortex. In its centre are numerous openings, marking the passage of its venous 

 sinuses. It is penetrated in every direction by excessively delicate bands of fibrous tis- 

 sue, which enclose blood-vessels, nerves, and numerous elongated, closed vesicles, contain- 

 ing cells, nuclei, and granular matter. These vesicles, -^ of an inch long and about ^^ 

 of an inch broad, have been demonstrated in the ox and in the human subject. The cells 

 in the human subject are from T1 ^ nr .to isW f an men * n diameter. They are isolated 

 with difficulty and are very irregular in their form. The nuclei measure about ygV* f 

 an inch. The medullary substance is peculiarly rich in vessels and nerves. 



Vessels and Nerves. The blood-vessels going to the suprarenal capsules are very 

 numerous and are derived from the aorta, the phrenic artery, the coeliac 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 the tubes, but never penetrating them. In the medullary substance, the 

 meshes are more rounded, and here the vessels form a very 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 very numerous and are derived from the semilunar ganglia, the renal 

 plexus, the pneumogastric, and the phrenic. Kolliker mentions that he has counted, in 

 the human subject, thirty -three nervous trunks entering the right suprarenal capsule. 

 The nerves probably pass directly to the medullary substance, but here their mode of dis- 

 tribution is unknown. In the medullary matter, however, are two ganglia, characterized 

 by nerve-cells of the ordinary form, and situated close to the central vein. 



