126 REPORT— 1864. 



there follo'ws a decided narro\\dng of the vessel at its minutest part, ■which 

 continues until at last the vessel becomes indistinct, and all motion of blood 

 is lost, except a faint oscillation in vessels which are running transversely 

 into a main current. These experiments were confirmed by observations 

 made by my friends Dr. Henry and Mr. Yeats. 



Observations. — Series 9. On the Hood. The blood of animals destroyed 

 by the nitrite may always be smelt as charged with the substance. On a 

 large animal that had been killed by the injection of forty minims, I drew off 

 an ounce of blood from the right side of the heart into a flask, and on inha- 

 ling from the flask, absorbed suiRcient of the nitrite vapour to induce the 

 specific signs of its action. The fluid, however, in no way interferes with 

 coagulation, but, as I have said before, it arrests oxidation and decomposition. 

 On the corpuscles it exerts a powerful osmotic action. It has no effect on 

 them in the way of dissolution, nor does it, when added to them, destroy their 

 form or modify the central depression, but it reduces them to half their ordi- 

 nary size, leaving them well defined and capable of running together in the 

 ordinary and natural way. 



From these narrations of experiments we may learn, in brief, the following 

 facts in reference to the physiological action of the nitrite of amyl. 



1. It is absorbed by the bodies of animals however introduced into the 

 organism — by the skin, by the stomach, by the lungs, by the cellular tissue. 



2. After its absorption its effects are seen immediately on the heart and 

 circulation ; there is in the first instance violent action of the heart with 

 dilatation of the capillaries, followed by diminished but not extingiiished 

 power of the heart, and contraction of the extreme vessels. As an excitant 

 of vascular action, the nitrite of amyl may be considered the most powerful 

 agent as yet physiologically discovered. 



3. On animals, such as frogs, whose bodies admit of its removal sponta- 

 neously, and whose circulatory and respiratory systems are simple, the nitrite 

 suspends animation, and when the animals are placed under favourable con- 

 ditions for the process of recovery, they may recover after considerable periods 

 of time. There is no other known substance that suspends animation in 

 these animals for so long a period. On warm-blooded animals, which are 

 clothed in thick and less penetrable skin, and in whose bodies the circulatory 

 and respiratory systems are more complicated, the nitiite cannot actually 

 stop the movements of respiration and circidation without destroying life. 

 Eut even in these animals it can without destroying life reduce the forces of 

 respiration and circulation so extremely, that a condition precisely analogous 

 to what is known as trance or catalepsy in the human subject, can be brought 

 on and sustained for many hoiu's. 



4. The nitrite of amyl is not an ana>sthetic. By it consciousness is 

 never destroyed, unless a condition approaching to death be produced. 



5. The effects of the nitrite on the organism are directed to the motive 

 force, which it first ■wdldly excites and then subdues. 



6. The modus operandi of the nitrite appears to be by arresting the pro- 

 cess of oxidation in the tissues. 



7. Physically the nitrite holds a place between the volatile bodies, such 

 as chloroform, and the soUd bodies, such as opium and woorali. Hence its 

 effects are less evanescent than those of the very volatile substances, and less 

 certainly destructive than the solid substances. In this lies the secret of its 

 prolonged action. 



