2. Endocrines and Populations 199 



by Biillough ( 19o2) (Ratcliffe, unpublished; J. J. Christian, unpubUshed) . 

 These conditions which resulted in which medullary hypertrophy all 

 constituted prolonged, chronic stimuli. Medullary hypertrophy due to 

 hyperplasia probably occurs simultaneously with cortical hypertrophy in 

 many species but perhaps requires a more sustained stimulus and develops 

 at a much slower rate. There also seems to be some suggestion that emo- 

 tional stimuli may be important in this effect. Finally, it has been shown 

 that treatment with pituitary growth hormone will produce a marked 

 hypertrophy of the adrenal medulla (Moon et at., 1951; Lostroh and Li, 

 1958) , and may eventually result in medullary tumors (Moon et at., 1950) . 

 The role of sympathicomedullary function in physiologic adaptation re- 

 quires more investigation, especially in regard to chronic stimulation, such 

 as is produced by sociopsychologic pressures, and for a variety of species. 



2. Hormones Secreted by the Adrenal Cortex: Their Actions and 

 THE Regulation of Their Secretion. 



a. The zona glomerulosa. (1) The hormones. The adrenal cortex secretes 

 two steroid hormones, aldosterone (18-aldocorticosterone) and deoxycorti- 

 costerone (11-deoxycorticosterone), which have their primary effects on 

 salt-electrolyte and water metabolism. However, aldosterone is the only bio- 

 logically important sodium-retaining corticoid secreted by the adrenal cor- 

 tex and it is many times more powerful than deoxycorticosterone in its 

 effects on electrolyte metabolism (Farrell et al., 1955; Gaunt et at., 1955; 

 Gross and Lichtlen, 1958) . Also aldosterone is an important secretory pro- 

 duct of the adrenal cortex, whereas deoxycorticosterone is secreted only in 

 trace amounts (Farrell et at., 1955; Jones, 1957) and is probably a precursor 

 in the formation of aldosterone (Giroud et al., 1958). The actions of these 

 two hormones are very similar within the physiological range of dosages for 

 each, but their actions with overdosage differ considerably: overdosage 

 with aldosterone does not lead to the excessive sodium retention and the 

 diabetes insipidus-like state which are seen after overdosage with deoxy- 

 corticosterone (Gross and Lichtlen, 1958). 



It is appropriate at this point to comment on the general classification of 

 the adrenal corticoids into the two broad categories which are used in the 

 present account. The hormones of the adrenal cortex have been loosely 

 grouped as "sodium-retaining" or ''carbohydrate-active" according to 

 whether their prunary actions are on salt-electrolyte metabolism or if they 

 are among those steroids having marked effects on carbohydrate meta- 

 bolism. The sodium-retaining steroids include aldosterone, deoxycorti- 

 costerone, and, to a much lesser extent, 17-hydroxy-ll-deoxycorticosterone 

 (Reichstein's compound S) . The principal carbohydrate-active steroids are 



