214 



GENERAL ZOOLOGY 



many years. Its chemical structure is known and it has been 

 prepared synthetically. Its formula is C 6 H 3 (OH)2CHOHCH2- 

 NHCH 3 . The principal action of epinephrine is on tissues 

 innervated by the sympathetic nervous system. Its frequent 

 use as a styptic (astringent) in minor surgery to control hemor- 

 rhage depends on its capacity to constrict arterioles. The vaso- 

 constriction is, however, followed by a vasodilation, which makes 

 the use of epinephrine as a styptic of questionable value. Sub- 

 cutaneous injection of epinephrine also produces an increase of 



Fig. 134. — Adrenal gland of frog in Fig. 135. — Human adrenal gland 



position on ventral face of kidney. and kidney, somewhat diagrammatic. 



a, adrenal; ao, aorta; p, postcava; k, a, adrenal; b, adrenal blood vessels; k, 



kidney. kidney. 



sugar in the blood (hyperglycemia) and loss of sugar through the 

 kidneys (glycosuria), indicating that it stimulates glycogenolysis 

 (conversion of glycogen into sugar) in the liver and elsewhere. 

 It has been shown that in emotional excitement, such as is pro- 

 duced by fear or anger, there is an increased secretion of adrenalin 

 which likewise increases the sugar in the blood. This has an 

 adaptive significance since increased sugar means a ready source 

 of energy. Secretion of epinephrine may be produced in an 

 experimental animal by stimulating the splanchnic nerves to the 

 adrenal glands. Injection of epinephrine in frogs causes con- 

 traction of chromatophores, an effect opposite to that produced 

 by the hormone of the intermediate lobe of the pituitary gland. 



