THE ADRENAL 110 



which CDiitain the glancluhir ci)ithelmm. This coiuicctivc tissue is 

 reticular in character. 



The CORTEX (Fig 295, B) is subdivided into three layers or 

 zones: (a) A narrow, superficial layer, the glomerular zone; (b) a 

 broad middle layer, the fascicular zone; and (c) a narrow deep layer, 

 the reticular zone. The names of the layers are indicative of the 

 shape of the connective-tissue-enclosed compartments and of the 

 contained groups of gland cells. In the glomerular zone (Fig. 295, a) 

 the high, irregularly columnar epithelium is arranged in spherical or 

 oval groups. The protoplasm of the cells is granular, contains fat 

 droplets, and their nuclei arc rich in chromatin. In the fascicular 

 zone (Fig. 295, b) polyhedral cells are arranged in long columns or 

 fascicles. The cytoplasm is granular and usually contains many 

 large fat droplets. The nuclei contains less chromatin than those in 

 the glomerular zone. The appearance which the protoplasm of the 

 cells richest in fat presents has led to their being called "spongi- 

 oblasts." In the reticular zone (Fig. 295, c) similar though somewhat 

 more darkly staining cells, containing small fat droplets or sometimes 

 no fat droplets, form a coarse reticulum of irregular anastomosing 

 cords. 



This division of the cortex into zones is more distinct in some of the lower 

 animals. It does not indicate any fundamental structural or functional differ- 

 ences. The cells in the different zones show only minor variations in structure, 

 the characteristic appearance of the zone depending upon the arrangement of 

 the cells and the shape of the connective-tissue compartments. According to 

 Gottschau the glomerular zone is the zone in which active formation of new 

 cells takes place, these cells gradually passing toward the medulla, according to 

 some, finally completing their history as medullary cells. Others terminate 

 the life history of these cells with the deepest layer of the cortex. The pigment 

 formation in the cells of the reticular zone is considered by some, a degenerative, 

 by others a secretory process. Still other investigators look upon the deeper cor- 

 tical layers as the site of most active cell proliferation and an indifferent cell here 

 situated as giving rise on the one hand to pigment cells and on the other to 

 fat-producing cells. If the deeper cells are the older, the deeper zone would 

 contain the more mature and probably the more functionally active cells, and 

 it is here that are found cells crowded with fat droplets or with pigment granules. 

 The former begin, according to some investigators, in the superficial cell as 

 droplets of ordinary fat, which becomes changed into lecithin — an easily broken- 

 down, acid, phosphorus-containing fat with which many of the cells of the 

 deeper layers are filled. As already noted, this pigment is regarded by some as 

 the last stage in fat formation, by others as an entirely independent secretion. 

 This interrelation of cortical and medullary cells is not, however, in accord with 

 the findings of embryology or of comparative anatomy (p. 421). 



