The suprarenal gland is a small, ductless, glandular organ situated above the kidney. It consists chiefly of an outer yellowish portion or cortex and an inner darker portion or medulla. This inner portion, and extracts made from it, possess remarkable haemostatic properties which are due to a crystalline body, adrenalin or adrenin, which is present in very small proportion. This substance has been prepared synthetically in the form of a pale buff-coloured crystalline powder,

Adrenalin is the most powerful haemostatic known. By subcutaneous injection the blood-vessels are locally constricted so as to render minor surgical operations almost bloodless. It is similarly used to arrest postpartum and other haemorrhages.

Adrenalin is laevo-dihydroxyphenyl-ethanol-methylamine (laevo-methylamino-ethanol-catechol), C6H3(OH)2CHOHCH1NHCH3, very slightly soluble in water, almost insoluble in alcohol, ether and chloroform; a dilute acid solution gives with a trace of ferric chloride an emerald green colour which is changed to purple or carmine by the cautious addition of a dilute solution of sodium hydroxide.