436 MANUAL OF HISTOLOGY. 



stroma, and its meshes in man have an oval or rounded form, 

 so that, as a rule, the cell-groups have a similar shape. On the 

 whole, we find a smaller proportion of connective tissue in the 

 medulla than in the cortex. 



The blood-vessels of the suprarenal capsules occupy the 

 stroma, and are found in great abundance. The arterial vessels 

 arise from the aorta, the phrenic and renal arteries, and the 

 cceliac axis. About twenty small branches pierce the capsule, 

 and are distributed mainly to the cortex. The medullary sub- 

 stance is very rich in venous plexuses. Capillary networks 

 are found in both cortical and medullary portions. The veins 

 uniting form one principal branch, which passes out at the hi- 

 lus of the organ. The right suprarenal vein empties its blood 

 into the vena cava inferior, the left one into the vena renalis 

 sinistra. 



Lymphatics were seen by most observers only at the sur- 

 face of the suprarenal capsules. Klein, however, has recently 

 asserted that there exists between the cells "an anastomosing 

 system of narrower and broader clefts, channels, and lacunae, 

 which belong to the lymphatic system." This applies to the 

 zona fasciculata. In the other portions of the organ the same 

 writer also finds lymph-spaces, and lymph-sinuses, occupying 

 the regions "between the septa and trabeculse of the frame- 

 work on the one hand, and the cell -groups on the other." 



The nerves occur in comparatively greater abundance in 

 these organs than in any other glandular structures of the hu- 

 man body. Kolliker was able to count thirty-three branches 

 in a single suprarenal capsule of a man. They are derived 

 from the renal plexus, the pneumogastric and phrenic nerves, 

 and semilunar ganglion. Yery fine or medium-sized, dark-bor- 

 dered fibres are commonly encountered, and they abound espe- 

 cially in the medulla. Ganglion-cells are also frequently seen, 

 and Virchow has traced them into the interior of the organ. In 

 the cortical substances they are of rare occurrence. The terminal 

 distribution of the nerves has not been hitherto ascertained, 

 and it appears to be still a matter of doubt whether they ter- 

 minate in the suprarenal body at all. 



.Development. In mammals the suprarenal capsule has an 

 independent origin in a collection of tissue between the Wolff- 

 ian bodies behind the mesentery and in front of the abdomi- 

 nal aorta. (Kolliker.) The mesoderma at this point assumes 



