THE SUPRARENAL GLANDS 



551 



At the inner border of the zona fasciculata the connective tissue 

 bundles pass insensibly from the regular columnar arrangement of this 

 layer into a reticular maze. The resulting cell groups are of very irregu- 

 lar form and compose the innermost cortical layer, the zone reticularis. 

 This layer is the 

 thinnest and least 

 distinct of the 

 three zones of the 

 cortex. It can 

 often be more read- 

 ily distinguished by 

 the highly pig- 

 mented condition 

 of its cells, than by 

 the mere form of 

 its cell columns. 

 In man it passes 

 almost insensibly 

 into the medulla : 

 in many animals 

 e.g., the dog, cat, 

 and pig there is. a 

 sharp demarcation 

 between the zona 

 reticularis and the 

 medulla, produced 

 by a thin mem- 

 branous layer of 

 connective tissue 

 which apparently 

 results from the 



FIG. 479. PHOTOMICROGRAPH OF SUPRARENAL GLAND OF 

 DOG. Magnification X 30. 



A, loose areolar connective tissue of outer portion of 

 capsule containing two large (G) and several small gan- 



glia; c, capsule proper; g, zona glomerulosa; F, zona fascic- 

 ulata; R, zona reticularis of cortex; M, medulla, showing 

 the large central vein (V). 



fusion of the cen- 

 tral ends of the 

 fibrous bands in the 

 cortical stroma. Such a membranous septum is usually wanting in the 

 human adrenal. 



The connective tissue stroma of the adrenal consists of a delicate 



vascular network, which in the cortex contains very few if any elastic 



fibers. Flint (1900) has shown that this connective tissue is, in large 



part, at least, a reticular tissue. The capsule consists of dense bundles 



35 



