I.— PHYSIOLOGY. 179 



normal conditions is so limited that it can hardly affect the blood-pressure 

 and it is not apparently essential for life. There can be little doubt, 

 however, that in moments of excitement adrenaline is liberated in large 

 amounts and that it is responsible for some of the expressions of the 

 emotions. The action of adrenaline under such conditions is to raise the 

 blood-pressure by constricting peripheral vessels, to dilate bronchioles, 

 to erect the hair, to increase the blood-sugar, to immobilise the alimentary 

 canal, and to facilitate the clotting of blood. Cannon has shown that 

 cats respond to psychical stimulation, such as may be induced by the 

 presence of a dog, after the entire thoracic sympathetic system has been 

 removed ; the interpretation must be that in these emotional conditions 

 adrenaline is set free in relatively large amounts. 



The expressions of the emotions, such as anger and terror, are to the 

 animals an advantage : the easy breathing, the ready clotting of the 

 blood, the increased circulation may all have their advantages in a fight. 

 The ultimate cause of spasmodic asthma is constriction of the bronchiolar 

 muscle ; if during an asthmatic attack the patient is subjected to some 

 sudden terror or other pronounced emotion the attack sometimes promptly 

 ceases, in a manner exactly simulating the way in which a small injection 

 of adrenaline will abort an attack. 



In parts of West Africa the Calabar Bean, Physostigma, was sometimes 

 used, in trial by ordeal, to determine the innocence or guilt of persons 

 accused of witchcraft or other crimes. A normal person after drinking 

 an infusion of this bean promptly vomits and gets rid of the poison. In 

 states of emotion, which might well occur in a guilty person, the stomach 

 is flaccid and immobile, vomiting does not occur and the poison is absorbed. 

 The adrenaline takes some part in this inhibition of vomiting as it stops 

 the movements of the stomach. The bean ordinarily induces violent 

 contractions of the stomach which cause reflex vomiting. 



Ephedrine is an alkaloid which is obtained from a Chinese plant, 

 Ephreda, and which has been used by the Chinese as a medicine from 

 time immemorial. It will be seen from the two formulae that it is closely 

 related to adrenaline and has an action very similar to it ; but ephedrine 

 acts when taken by the mouth, whilst adrenaline is so easily oxidised that 

 it is destroyed when administered in this manner ; adrenaline causes 

 pulmonary congestion by dilatation of the coronaries : ephedrine has no 

 such effect. These are only some of the differences between these two 

 closely related alkaloids. 



JSTH.CHj 



CH,.NH.CH3 Ch/ 



I ■ 1 ^CH3 



CH,.OH CH.OH 



Adrenaline [ ] | j Ephedrine 



OH 



Ephedrine has proved of great value in the treatment of spasmodic 

 asthma, since oral administration produces prolonged broncho-dilatation. 



n2 



