THE SUPRARENAL GLANDS 549 



also comprising a series of structures, is known throughout, due to its 

 close topographical relationship to the kidney, as the adrenal. The cortex 

 of the mammalian suprarenal gland thus represents the product of fusion 

 of the ichthyoid interrenals. In the groups between fishes and mammals, 

 the association of interrenals (cortical component) and adrenals (medul- 

 lary component) becomes progressively more intimate. 



The suprarenal is absolutely essential to life; removal promptly results 

 in death. -According to Crile (1914) the brain is intimately dependent 

 upon the suprarenals; when both glands are excised in the rabbit death 

 follows in eighteen hours, the brain cells meanwhile exhibiting loss of 

 chromophilic substance. The two portions are believed to have, in part at 

 least, a different function, both inhering however in an internal secretion. 

 The cortex is generally believed to elaborate an antitoxic secretion for 

 neutralization of harmful products of destructive metabolism. The func- 

 tion of the medulla is dependent upon the adrenalin (adrenin; epinephrin) 

 of the pheochrome granules, probably having to do with maintaining the 

 proper tonus of the muscle of the heart and blood-vessels, thus underlying 

 blood pressure. Minute amounts of epinephrin in the blood effect a sensi- 

 tization of the vasoconstrictor nerve endings so that the efferent impulses 

 discharged cause the muscular coats of arterioles to contract vigorously, 

 the result being an increase in blood pressure. The most conspicuous 

 diseases of the suprarenals involve hypersecretion, perhaps inducing to 

 arteriosclerosis; and hyposecretion, frequently the result of tuberculous 

 lesions, producing a clinical complex known as Addison's disease. (Refer- 

 ence should be made to Vincent's "Internal Secretions and the Ductless 

 Glands," Longmans, 1912.) 



The organ is enclosed by a connective tissue capsule of considerable 

 thickness. From the inner surface of the capsule delicate fibrous trabecu- 

 Ise pass inward and subdivide the epithelial parenchyma of the organ 

 into cell groups and columns, which vary in their appearance according to 

 the distribution of the connective tissue trabeculae. The suprarenal paren- 

 chyma is exceptionally prone to post mortem changes. In the medulla 

 the connective tissue presents an irregular areolar arrangement; the 

 more regular, though varying form of the areolae in the cortex, subdi- 

 vides this portion of the organ into three more or less distinct layers, 

 which were first described by Arnold (Arch. f. path. Anat., 1866) as the 

 zona glomerulosa, zona fasciculata, and zotia reticularis. 



In the zona glomerulosa the connective tissue trabeculae subdivide 

 the epithelium into spheroidal groups of cells, many of which are con- 

 tinuous with the cell columns of the adjacent zona fasciculata. The 

 glomerulate layer is relatively thin and lies close beneath the capsule. 



