ON THE PHYSIOLOGICAL ACTION OF AMYL AND ETHYL COMPOUNDS. 175 



part or chamber, for insertion, by means of a quill or hoUow probe, into the 

 vein to be injected : the upper part of the cylinder is provided with a stopper, 

 through which a tube passes, connected vnth. a small pari- of hand bellows (D). 

 Within the cylinder is a small hollow ball (E), or safety-valve regulator, 

 which floats if there be fluid in the cylinder ujitil the fluid allows it to descend 

 to the constricted lower part of the cylinder, when all fm-ther passage of fluid 

 is prevented. The flow of fluid along the escape-tube can be checked, or set 

 at liberty at pleasure by the clip (C). 



In using this iustiniment, first place the fluid to be injected in the cylinder 

 (A) and let a little run through the escape-tube (B) to displace aU the air ; next 

 close the escape-tube by means of the clip (C) ; then, having opened the vein 

 or artery, whUe it is being pressed upon from above, insert and fix the quill 

 or hollow probe at the end of the escape-tube, and, when all is ready for the 

 fluid to flow, remove the clip and raise the cylinder two or three feet above 

 the subject. The ordinary liuid-pressure will now usually suflice to carry the 

 fluid into the body equably and gently ; but if there be any obstruction, the 

 merest pressure of the lower ball of the hand bellows will remove it. As the 

 fluid descends, the hollow ball goes down with it to within three inches of 

 the bottom of the cylinder, where it is opposed by the constricted neck, and 

 where it effectually closes in all that is below it, so that no air can possibly 

 get into the blood-vessel. 



Eeverting to the experiments related above, they, although negative as 

 regards the particular object in view during their performance, teach an 

 interesting and usefid physiological lesson. They illustrate that when in the 

 living body the nitrite of amyl, after its inhalation, excites the heart to such 

 vigorous action, producing suffusion of the skin and the other extreme 

 symptoms of excitation, the effect is conducted solely through the nervous 

 system. I believe that the action of the nitrite, telling, at the moment of 

 inhalation, tipon the extreme filaments of the olfactory nerves, as well as on 

 the pneumogastric tracts, communicates a peculiar and rapid motion, which 

 traverses them and, without any indirect action on the blood, reaches the 

 heart, giving to it impulse and vehemency of action. 



^ The expciience of every-day life tells us that the heart may be thrown into 

 similar activity by impressions or influences communicated from the external 

 world to the senses, and through them to the heart. The influences of 

 sounds, harsh or melodious, of sights, appalling or fascinating, are well known, 

 from the manner in which they come upon us. From their invisibility of 

 action, if I may be allowed such an expression, we are prone to look on them 

 as immaterial agents: they are not so; thoroughly understood they are 

 as material as a physical blow, or the impress of a liquid or gaseous sub- 

 stance. 



Nitrite of amyl is one of those substances which enable us to realize this 

 connexion between the really material and the seemingly immaterial influences 

 which surroimd us. We take an appreciable quantity of it, say, half a grain, 

 and inhale it from paper, and at once we feel a quickened action of the circula- 

 tion so decisively that we trace the effect immediately to the cause: we could, 

 if we Hked, quicken the heart to absolute silence by pushing the cause far 

 enough. Here there is no mistake, no possibility of mistake. But we can 

 modify the experiment and refine upon it. By admixing the vapour of am- 

 monia with that of amyl, and difiPiising the combined vapours through a large 

 space of air confined by walls and closed windows, we can charge a room 

 with a compound which the olfactory sense, as such, does not detect, but which 

 teUs with active and peculiar force upon the heart. In this way an invisible 



