In the first experiment, I breathed for near a minute, three quarts of hydrocarbonate mingled with nearly two quarts of atmospheric air.[209] It produced a slight giddiness and pain in the head, and a momentary loss of voluntary power: my pulse was rendered much quicker and feebler. These effects however, went off in five minutes, and I had no return of giddiness.
Emboldened by this trial, in which the feelings were not unlike those I experienced in the first experiments on nitrous oxide, I resolved to breathe pure hydrocarbonate.
For this purpose, I introduced into a silk bag, four quarts of gas nearly pure, which was carefully produced from the decomposition of water by charcoal an hour before, and which had a very strong and disagreeable smell.
My friend, Mr. James Tobin, Junr. being present, after a forced exhaustion of my lungs, the nose being accurately closed, I made three inspirations and expirations of the hydrocarbonate. The first inspiration produced a sort of numbness and loss of feeling in the chest and about the pectoral muscles. After the second inspiration, I lost all power of perceiving external things, and had no distinct sensation except a terrible oppression on the chest. During the third expiration, this feeling disappeared, I seemed sinking into annihilation, and had just power enough to drop the mouth-piece from my unclosed lips. A short interval must have passed during which I respired common air, before the objects about me were distinguishable. On recollecting myself, I faintly articulated, “I do not think I shall die.” Putting my finger on the wrist, I found my pulse thread-like and beating with excessive quickness.
In less than a minute, I was able to walk, and the painful oppression on the chest directed me to the open air.
After making a few steps which carried me to the garden, my head became giddy, my knees trembled, and I had just sufficient voluntary power to throw myself on the grass. Here the painful feeling of the chest increased with such violence as to threaten suffocation. At this moment, I asked for some nitrous oxide. Mr. Dwyer brought me a mixture of oxygene and nitrous oxide. I breathed this for a minute, and believed myself relieved. In five minutes, the painful feelings began gradually to diminish. In an hour they had nearly disappeared, and I felt only excessive weakness and a slight swimming of the head. My voice was very feeble and indistinct. This was at two o’clock in the afternoon.
I afterwards walked slowly for about half an hour, with Mr. Tobin, Junr. and on my return, was so much stronger and better, as to believe that the effects of the gas had disappeared; though my pulse was 120 and very feeble. I continued without pain for near three quarters of an hour; when the giddiness returned with such violence as to oblige me to lie on the bed; it was accompanied with nausea, loss of memory, and deficient sensation. In about an hour and half, the giddiness went off, and was succeeded by an excruciating pain in the forehead and between the eyes, with transient pains in the chest and extremities. Towards night these affections gradually diminished. At ten,[210] no disagreeable feeling except weakness remained. I slept sound, and awoke in the morning very feeble and very hungry. No recurrence of the symptoms took place, and I had nearly recovered my strength by the evening.
I have been minute in the account of this experiment because it proves, that hydrocarbonate acts as a sedative, i. e. that it produces diminution of vital action, and debility, without previously exciting. There is every reason to believe, that if I had taken four or five inspirations instead of three, they would have destroyed life immediately without producing any painful sensation. Perhaps most of the uneasy feelings after the experiment, were connected with the return of the healthy condition of organs.[211]
About a week after this experiment, I attempted to respire Carbonic acid, not being at the time acquainted with the experiments of Rosier.
I introduced into a silk bag four quarts of well washed carbonic acid produced from carbonate of ammoniac[212] by heat, and after a compleat voluntary exhaustion of my lungs, attempted to inspire it. It tasted strongly acid in the mouth and fauces, and produced a sense of burning at the top of the uvula. In vain I made powerful voluntary efforts to draw it into the windpipe; at the moment that the epiglottis was raised a little, a painful stimulation was induced, so as to close it spasmodically on the glottis; and thus in repeated trials I was prevented from taking a single particle of carbonic acid into my lungs.