THE DUCTLESS GLANDS. 



187 



FIG. 162. 



and denser internally, where it is reinforced in some animals by 

 smooth muscular fibres. From 

 this capsule septa of areolar tissue 

 penetrate into the substance of the 

 organ and constitute its interstitial 

 tissue. The parenchyma of the 

 organ consists of columns of epi- 

 thelial cells, which are differently 

 arranged and have a somewhat dif- 

 ferent appearance in different parts. 

 As the result of these differences the 

 organ has been divided into a cor- 

 tical and a medullary portion. 



In the cortical portion the cells 

 are arranged in solid columns hav- 

 ing their long axes perpendicular to 

 the surface of the organ. Toward 

 the capsule these columns lose their 

 parallel arrangement and appear in 

 vertical sections as islets of cells 

 surrounded by areolar tissue, the 

 " zona glomerulosa." In the deep 

 portion of the cortex the cellular 

 columns form a meshwork and com- 

 pletely lose their fascicular arrange- Vertlcal "^" n of hum 7n^enai body. 



ment. This region is Called the (Eberth.) 1, cortex; 2, medulla; a, 



.. T . ,, rrn -,i T i capsule ; 5, zona glomerulosa ; c, zona 



ZOlia retlClllans." The epithelial fasc icul a ta; d, zona reticularis; , 



cells in the cortical portion are poly- ^ OU P S of medullary ceils ; /, partial 



.!.., section of a large vein. 



nedral, and are frequently infiltrated 



with numerous globules of oil or fat, which give that part of the 



organ a yellow color. 



In the medulla the interstitial tissue of the organ encloses groups 

 of epithelial cells, which differ from those of the cortex in being 

 free from fat. They are also larger than those cortical cells which 

 contain no fat (Fig. 163). 



The arteries of the adrenal bodies enter as numerous small twigs 

 at the surface of the organ and divide into capillaries within its 

 fibrous septa. These open into a venous plexus in the medulla, 

 which communicates with a single vein leaving the organ. 



The nervous supply of the adrenal bodies is very abundant. The 



