Integrative Systems 217 



causes preparation of the uterus for reception of the fertilized egg and 

 induces functional activity of the mammary glands. 



Adrenal (or Suprarenal) Glands 



The terms adrenal, or suprarenal, and interrenal refer to 

 certain endocrinal organs which have no relation to the renal organs 

 except that of proximity. Considering these glands collectively, they 

 involve secretory tissues of two sorts, differing in origin, histologic 

 characteristics, and functional effects. Tissue of one sort is derived 

 from mesoderm; the other, from cells which have common origin with 

 neurons of the autonomic ganglions, being therefore derivatives of the 

 ectodermal neural tube. The ectodermal glandular tissue is histolog- 

 ically distinguished from the mesodermal by its relatively large "chro- 

 maffin cells,'" so called because they have a strong affinity for chromic 

 salts, which stain them brown. In the cyclostome eels the mesodermal 

 glands appear as a paired series of small interrenal bodies which lie 

 throughout the length of the body-cavity near the postcardinal veins. 

 The chromaffin cells are arranged as strands along the dorsal aorta. 

 In the sharklike fishes, the interrenal bodies tend to aggregate in 

 the posterior part of the body-cavity, while the chromaffin cells occur 

 in segmentally arranged groups near the sympathetic ganglions. In 

 terrestrial vertebrates the two secretory tissues tend to become 

 localized in more definite glandular organs in the posterior region of 

 the coelom, and tend also to occur together within the confines of the 

 same glandular mass, but yet retaining their histologic and functional 

 specificity. These tendencies reach their culmination in mammals, in 

 which the two tissues are localized in one pair of adrenal (or supra- 

 renal) glands, situated usually very close to the kidneys (Fig. 185). 

 There may be, however, some small accessory adrenal bodies nearby. 



In the mammalian adrenal there is an outer yellowish cortex 

 consisting of the mesodermal tissue, and a central brownish medulla 

 in which appear the characteristic chromaffin cells of the ectodermal 

 tissue. They are arranged in clusters separated by numerous blood- 

 spaces. A compact connective-tissue capsule encloses the glandular 

 tissues (Fig. 186). 



Functions of Adrenals. The adrenals have a double function 

 corresponding to their two tissues. The cortex secretes an endocrine, 

 cortin, of unknown chemical composition, which is essential to life. 

 Destruction of the cortex is followed by Addison's disease, which is 

 characterized by a deep pigmentation of the skin and great weakness. 

 Death comes rapidly unless cortin is administered. The cortex of the 

 adrenal is, relative to the medulla, largest during fetal life, and there 

 is little doubt that its secretions have a strong influence upon growth. 



