ANATOMY OF A 17.8 MM. HUMAN EMBRYO 49 



Each gland has developed in the path of the cephalic part of the 

 subcardinal vein of that side, and the vein has been subdivided 

 to fomi the sinusoidal channels now found within it. Sinusoids 

 in the suprarenal glands of maniinals were demonstrated histo- 

 logically by Minot ('00). 



The cells composing the cortex are arranged in peripheral 

 layers, surrounding a loose reticular core. These comprise what 

 is usually termed the interrenal part of the suprarenal glands, 

 from their resemblance to the interrenal bodies of Selachians. 

 These interrenal bodies are being invaded on their medial sur- 

 faces by numerous scattered clumps of deeply staining cells, 

 derived from the sympathetic ganglia, often termed the sym- 

 patho-chromaffine organs. 



A deeply staining, oval mass of cells is present on either side 

 of the inferior mesenteric artery, ventro-lateral to the aorta. 

 Caudally these bodies reach the level of the proximal part of the 

 common iliac arteries, while cephalad they are continued by scat- 

 tered, smaller groups of cells to the caudal extremities of the 

 suprarenal glands. They have a rich blood supply, and are 

 intimately related to the sympathetic system in their locality. 

 They unquestionably correspond to the aortic bodies discovered 

 by Zuckerkandl ('01)., 



It seems very probable to the author that each of these main 

 groups of cells has been partially isolated from the suprarenal 

 gland of its side by the development of the large dorso-ventral 

 segment of the supra-ureteral venous channel (plate 4) which now 

 intervenes between them. Further evidence of this interpreta- 

 tion is the fact that a closer relation between the two exists on the 

 left side in this em_bryo, where the vein in question is much smaller 

 than its companion on the right. 



Spleen. The spleen {Lien.) is clearly recognizable as a small, 

 protuberance of the mesogastrium, containing dense m.esenchyma. 

 The tissue directly ventral to this protuberance, is permeated by 

 a vascular network, supplied by the splenic artery, and drained 

 by the splenic vein (V.li., plate 4). 



THE AMERICAN JOURXAL OP ANATOMY, VOL. 17, NO. 1 



