. The endocrine organs; an introduction to the study of internal secretion . capsule. The zona reticularis also contains pigment granuleswhich in some animals give it a distinct .brownish colour. The humanfoetus has unusually large suprarenal capsules. It has been shown thatthis is almost entirely due to a great development of an innermost part ofthe cortex lying at the boundary with the medulla (boundary zone ofElliott and Armour (fig. 33)); this is not to be confounded with theintermediate zone of Virchow, a very thin layer, pigmented in old age,lying at the j unction of the cortex and medul
. The endocrine organs; an introduction to the study of internal secretion . capsule. The zona reticularis also contains pigment granuleswhich in some animals give it a distinct .brownish colour. The humanfoetus has unusually large suprarenal capsules. It has been shown thatthis is almost entirely due to a great development of an innermost part ofthe cortex lying at the boundary with the medulla (boundary zone ofElliott and Armour (fig. 33)); this is not to be confounded with theintermediate zone of Virchow, a very thin layer, pigmented in old age,lying at the j unction of the cortex and medulla. The cells of the boundary zone differ from those of the rest of the cortexin having no lipoid granules. After birth they undergo a fatty change 52 The Endocrine Organs and the layer gradually disappears, so that it is no longer distinguishableafter the first year. At birth what will be the cortex of the adult glandconsists only of a thin peripheral layer of cells containing lipoids; thesecells multiply, and the layer enlarges pari passu with the disappearance of :,..-. FIG. 33.—Section of suprarenal of child twelve days old, low power. (Elliott and Armour.) A, outer part of cortex ; B, large cells forming boundary zone of cortex ; C, thin layer ofmedulla : just below is the central vein. the boundary zone. A remarkable fact pointed out by Elliott and Armouris that in the anencephalous foetus the boundary zone is absent and thesuprarenal resembles that of other foatal mammals. FUNCTIONS OF THE CORTEX Little is known regarding the functions of the cortex. Its anatomicalrelation in mammals to the chromaphil part and the fact that its bloodpasses directly into the medulla suggests that its cells may be concernedin the production of materials which are utilised by the medulla; but, ashas been above mentioned, this relation fails in many vertebrates. It hasbeen stated by Abelous and others that the cortex contains a precursor ofthe adrenalin of the medulla, and that if left sta
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