REGULATORS 



591 



the cortex with it. But recently Vincent has attempted com- 

 pletely to destroy the medulla in dogs by thermocautery, and 

 he has found that the animals remain apparently normal. 



(2) The discovery that the iiijection of extracts of the 

 medulla suprarenalis gives rise to marked symptoms was the 

 first step to the explanation of its functions. The demonstra- 

 tion that the active constituent is a definite chemical substance, 

 Adrenalin, has enabled physiologists to carry out investigation 

 with great precision. Adrenalin is — 



Ortho-dioxy-phenyl. 



H H 



I I 

 _C — C — 



I I 

 OH H 



ethanol. 



H H 



I I 

 _N— C— H 



I 

 H 



methyl-amine. 



It has been prepared synthetically. 



It may be recognised by its reaction with chrome salts, and 

 by the ease with which it is oxidised, especially in alkaline 

 solutions. On account of this it strikes a green colour with 

 ferric chloride. With phosphotungstates along with phosphoric 

 acid it gives a blue colour, and by this test 1 part in 3 million 

 may be detected. 



That it is a product of the chromaffin tissue is shown by the 

 fact that the staining of the medulla is proportionate to its 

 physiological activity, and by the great amount of adrenalin 

 in the blood coming from the suprarenals. By pressing on the 

 suprarenals its amount in the blood may be increased. Section 

 of the branches of the splanchnic nerve going to the suprarenals 

 checks its liberation, while stimulation increases it. 



It acts — 



(1) On the Blood-vessels. When injected into a vein or 

 perfused in Ringer's Solution through the vessels, it causes 

 constriction of the peripheral arterioles, and thus raises the 

 arterial blood pressure (Practical Physiology). Its action is 

 most powerful on the abdominal vessels, and hence blood is 

 forced to the muscles of the limbs. The vessels of the skin, 

 however, are contracted. On the pulmonary vessels, and on 

 the intracranial vessels its action is slight, while it causes 



