AMYL NITRIS. 163 



increased frequency and force, that is, palpitation, of the heart; 

 visible pulsation of the carotids ; restlessness and anxiety of 

 mind. These symptoms quickly disappear, leaving possibly 

 slight headache. Larger doses aggravate all the phenomena, 

 but never produce unconsciousness ; mental confusion, intense 

 bodily depression, coldness of the extremities, and sweats being 

 the result, followed by severe headache which may last for 

 hours. Very rarely convulsions occur in man as in some of 

 the lower animals. 



The specific action of nitrite of amyl proves on analysis to 

 be almost confined to the circulatory system, the other parts 

 being chiefly involvetl secondarily. Two distinct effects are 

 produced on the circulation ; the heart is greatly accelerated, 

 with but little, if any, increase of its force ; the peripheral 

 vessels are dilated by relaxation of their muscular coat. 

 Some authorities hold that the cardiac acceleration is due 

 to depression of the cardiac centre, others to depression of the 

 vagus in the heart ; some refer the vascular relaxation to the 

 action of the nitrite on the vasor centre in the medulla, others 

 to its action on the vaso-motor nerves and muscular walls. 

 Be this as it may, the fact remains that the blood pressure 

 falls to a remarkable degree, that is, the resistance to the 

 discharge of the left ventricle is correspondingly diminished ; 

 whilst this discharge is accomplished much more frequently 

 within a given time. In other words, the left ventricle, 

 under the influence of nitrite of amyl, has at once less work to 

 accomplish, and more force wherewith to accomplish it ; that 

 is, is greatly relieved. These considerations led Dr. Lander 

 Brunton to the employment of the drug in those cases of 

 the complex class of disease known as angina pectoris, in 

 which agonising pain in the breast and neighbourhood 

 is due to distension of the left ventricle, from its inability to 

 empty itself against the pressure in the aorta, and in which 

 fatal paralysis of the heart, or even rupture of its walls, is the 

 result of the unequal effort. Clinical experience has fully con- 

 firmed the value of amyl nitrite, in cases where spasm of the 

 arteries is damming the blood back upon the ventricle, tho 

 channels being instantly opened and the ventricle rapidly 

 emptied by the double effect of the drug. The pain of 

 the aneurism of the aorta, and of other forms of cardi;u 

 and disorder, can often be relieved by amyl, but caution must 

 be exercised in the first trial. Threatening death from cardiac 

 paralysis in chloroform anaesthesia, and sea-sickness in which 

 the blood pressure is greatly disturbed, are sometimes success- 

 fully treated with amyl. Some cases of epilopsy, accompanied 

 by spasm of the cerebral vessels and facial pallor, and of 



