It must be admitted that it is still impossible to give a definite answer to the question, “What is the function, or what are the functions, of the adrenal bodies?” Several important facts have been made out and some theories have been put forward. The facts are: I. A definite chemical substance of known composition and possessing well marked pharmacodynainical activities can be extracted from the chromaphil tissues. II. This substance, adrenin, can be obtained from adrenal medulla as well as from chromaphil tissues in other situations. III. There is considerable evidence that adrenin is actually poured out into the circulation. IV. The true adrenal body or cortex is related in some way to the development and growth of the sex organs.