252 INTERNAL SECRETION 



Seeing that the morphology of the adrenal system is every- 

 where the same, what is known of the secretory processes of the 

 suprarenal medulla may be taken as typical of the entire suprarenal 

 system. Whether forming the medullary portion of the supra- 

 renal capsules, or present in the form of isolated bodies, either 

 unattached or associated with the sympathetic nervous system, 

 adrenal tissue is invariably composed of rows and spheroid 

 agglomerations of cells, held together by a delicate structure of 

 connective tissue, and forming a large-meshed net. The 

 parenchymatous cells are always placed close against the blood- 

 vessels, and are, as a rule, separated by the endothelium only, 

 though occasionally- also by a delicate connective-tissue sheath, 

 from the lumen of the capillaries and the enlarged sinus-like veins. 

 The cytoplasm of the living chrome-brown cell contains extremely 

 minute granules, which are, however, coarser in certain animal 

 species. Some of these granules cluster closely together, while 

 others are arranged more loosely ; they are not so highly refractive 

 as fat-granules ; they dissolve in water and in alcohol, but are not 

 soluble in ether, acetic acid, the etherial oils, or in xylol. In 

 fresh unhardened and unstained preparations, these granules are 

 scarcely visible ; they do not stain satisfactorily by any known 

 method, the best, however, being iron-haematoxylin with which 

 they colour a pale grey. When unstained, they are most easily 

 recognizable by means of a mixture consisting of Miiller's fluid 

 and formaline or by the various osmium solutions. By using 

 Zenker's fixing fluid, it is sometimes possible to obtain a good 

 eosin coloration. According to Poll, these granules have a cer- 

 tain relationship to the nuclear colouring substances. They colour 

 pale pink with Ziehl's solution, lake by van Gieson's method, 

 mauve with methylene-blue eosin, and greenish with Unna- 

 Pappenheim's methylene-green pyronin mixture. 



It is principally these fine granules which respond to the 

 ferric chloride and chromium tests, and give the reaction which 

 is characteristic of adrenalin. It is true that microscopic prepar- 

 ations with ferric chloride are not entirely free from objection. 

 But with fixing fluids containing chromium (chrome formol), 

 these granules take on a characteristic coloration varying from 

 yellow to brown, which does not, however, equally affect either 

 all the cells or all the granules in the cells. 



Ciaccio suggests that the granules are of two kinds; that 

 they at first stain brown with chromium and afterwards pass into 

 the iron-green stage, which represents the end product of secretion. 

 The evidence in favour of this theory is, however, wholly 

 insufficient, and particularly so in face of the fact that adrenalin 

 itself reacts to both tests. 



In addition to the fine granules, other cell-contents, such as 

 pigment granules, lipoid granules, etc., have been described. 

 Stoerk and v. Haberer have described the occurrence of large rods 



