THE DUCTLESS GLANDS 1321 



arranged in columns or in a reticular fashion. The outermost layer of 

 cells often presents an alveolar structure, the lumen, however, being 

 but little marked. According to the arrangement of the cells the 

 cortex is divided into three zones, the zona glomerulosa, zona fascicu- 

 lata, and zona reticulata. The cells themselves are distinguished by 

 the large amount of granules they contain, which give the ordinary 

 reactions for fat, but consist probably of lecithin compounds. In some 

 animals, e.g. the guinea-pig, the cells, especially towards the inner part 

 of the gland, contain many yellow pigment granules. The medulla, 

 much less extensive than the cortex, presents irregularly shaped cells, 

 the outlines of which are but slightly marked. These cells contain 

 granules which stain darkly with chromates and give a green colour 

 with salts of iron. It is, hence, easy to delimit the area of the cortex 

 in any section of a gland which has been hardened in a fluid containing 

 chromates. The substance giving this reaction is known as chromo- 

 phile or chromaffine substance. The suprarenals are richly supplied 

 with blood, especially in the medullary part, the cells of which impinge 

 directly on the endothelial lining of dilated capillaries. They also 

 receive an abundant nerve-supply from the sympathetic system, the 

 nerves forming a thick rneshwork, especially in the medulla, and 

 presenting at intervals ganglion-cells which may be isolated or com- 

 bined to form small ganglia. 



A study of the development of the suprarenal glands shows that we 

 have here to do with two distinct tissues, probably differing in the part 

 they play in the animal economy. Whereas the cortex is derived 

 from that portion of the mesoblast, the ' intermediate cell mass,' from 

 which the mesonephros is also developed, the medulla is produced by 

 an outgrowth from the sympathetic system and may be said indeed 

 to consist of profoundly modified nerve-cells. In many fishes these two 

 elements of the suprarenal gland remain separated throughout life, the 

 cortex being represented by a series of paired interrenal bodies lying 

 on the front of the spinal column, and the medulla by a number of 

 collections of chromaffine cells lying in close juxtaposition to the spinal 

 nerves. In some animals accessory suprarenals are not infrequent 

 in which both cortex and medulla may be represented. In all animals 

 we find masses of tissue, the so-called paraganglia, in close association 

 with the sympathetic system, which present the chromaffine reaction 

 typical of the medulla. Since a watery extract or decoction of these 

 bodies has the same influence on injection into the blood-stream as 

 an infusion of the medulla of the suprarenal body itself, we are 

 probably justified in regarding these bodies as equivalent to accessory 

 medullary portions of the suprarenal. They have the same origin, the 

 same staining reactions, and the same physiological effect as the latter. 



The functions of the suprarenal bodies were a matter of pure 



