NORMAL AND PATHOLOGICAL GROWTH 157 



of blood. The hormone produced by the parathyroids influences 

 growth and activity by controlling the amount of available cal- 

 cium in the blood. Calcium in turn is absolutely necessary to 

 numerous protoplasmic reactions, including the development of 

 normal nerve reflexes, normal muscular contractions, heart 

 beats, etc. This hormone is necessary for the control and regu- 

 lation of very special chemical reactions of vital necessity to 

 metabolic processes of growth and energy transformation. 



IV. The Hormones of the Suprarenal Glands 



The pair of small glands in the abdominal cavity lying some- 

 what above the kidney, like the thyroid gland, produce internal 

 secretions that seem necessary for continued life. Whenever the 

 entire suprarenal is removed surgically, definite functional 

 changes take place that terminate in death in from one to five 

 or six days. Addison's disease, first described in 1849, 1S known 

 to be due to disease and impaired function of these structures. 



The suprarenal is derived from two embryologically distinct 

 sources. The cortex comes from the embryonic mesoblastic tis- 

 sue in close relation to the reproductive ridge, while the medulla 

 arises from neuro-epithelium and is related in origin to the 

 sympathetic ganglia. An active substance swprarenin has been 

 isolated from the medulla, but not from the cortex. This med- 

 ullary hormone has been identified chemically by Abel, 9 Al- 

 drich, 10 and Takamine. 11 It has the following structural for- 

 mula: 



CH 2 CH(OH)NHCH< 



This amino derivative has been produced synthetically and the 

 synthetic product influences the organs of the body in a way 

 comparable to the natural product. Epinephrin and thyroxin are 

 the only hormones whose chemical identity is now known. 



No active hormone has been derived from the cortex, though 

 it is believed that such exists. Further, it is the loss of the cor- 



