SECRETION. 



315 



ulata (c), and separated from each other by fibrous septa. The third 

 layer, that next the medulla, is called from its arrangement the zona 

 reticularis (not shown in fig. 225). The individual cells are polyhedral 

 in shape, each possessing a well-defined nucleus. In man the proto- 

 plasm of the cells is especially rich in fat globules, and oftentimes con- 

 tains in addition larger or smaller granules of a yellowish pigment. The 

 blood-vessels are confined to the septa, and do not penetrate into the cell 

 groups. 



(2.) The medullary substance consists of a coarse rounded or irregular 

 mesh work of fibrous tissue, in the alveoli of which are masses of multi- 

 nucleated protoplasm (fig. 226); numerous blood-vessels; and an abun- 

 dance of nervous elements. The cells are very irregular in shape and 

 size, poor in fat, and occasionally branched ; the nerves run through the 

 cortical substance, and anastomose over the medullary portion. 



Nerves. The adrenals are very abundantly supplied with nerves, 

 chiefly composed of mednllated fibres. These fibres are derived from 

 the solar and renal plexuses, vagi and phrenics. Nerve-cells are also 

 numerous in connection with these fibres. The fibres enter the hilum of 

 the gland, but the method of their termination is unknown. 



Fig. 225. Vertical section through part of the cortical portion of supra-renal of guinea-pig, 

 a, Capsule; 6. zona glomerulosa; c, zona fasciculata; d, connective tissue supporting the columns 

 of the cells o2 the latter, and also indicating the positions of the blood-vessels, x (S. K. Alcock.) 



Composition. In addition to the ordinary extractives, benzoio acid, 

 hippuric acid, and taurin have been found, and also inosite, as well as a 

 peculiar pigmentary substance, soluble in water, becoming red on ex- 



