Chap. 15 



CHEMICAL REGULATION ENDOCRINE GLANDS 



265 



Fig. 15.9. The common spotted newt (Triturus viridescens), blackened by the 

 layers of skin that accumulated because a part of its pituitary gland had been 

 removed. Layers of skin began to slip from the head after a duplicate of the miss- 

 ing part of the pituitary had been engrafted into the animal and had activated the 

 thyroid gland to stimulate the molting process. (Photo courtesy A. E. Adams 

 from Adams et al., "The Endocrine Glands and Molting in Triturus viridescens," 

 J. Exp. ZooL, Aug. 1932.) 



system and the cortex from cells near to those that form the sex organs. 

 Epinephrine (or adrenalin) (CgHiaOsN), the hormone of the medulla, is 

 very useful but not essential to life. It has been isolated in pure crystalline 

 form and was the first hormone to be synthesized. Its injection causes a rise 

 in blood pressure and quickened heart rate; more glucose is turned into the 

 blood from the liver and muscles, accompanied by increased muscular 

 power and resistance to fatigue. After making a long series of experiments, 

 an American physiologist, W. B. Cannon, concluded that adrenalin acts as 

 an emergency stimulant in the body, especially for the muscles. It is secreted 

 into the blood in excitement such as fear, pain, or intense effort. Facing the 

 peril of fire a person breaks a window glass with the bare fist; run down by 

 a dog, a cat turns about with hairs up and claws ready. Analysis of the blood 

 of such animals in emotional crises has shown that it contains many times 

 the minute amount of adrenalin (1 part in 1 or 2 billion parts of blood) 

 ordinarily present. At such times the muscles demand more food and more 

 oxygen to combine with it and set energy free. These are provided by glucose, 

 by the increased pumping of the heart, by more rapid breathing, and the 

 higher arterial blood pressure. 



