Experiment 39. Another linnet was placed in the same jar, with four grains of ether to each 100 cubic inches of air. In two minutes it was unable to stand, and in a minute more, voluntary motion had ceased. It lay breathing quietly till taken out, at the end of a quarter of an hour. It moved its foot slightly when it was pinched. In three minutes it began to recover voluntary motion, and was soon well. The temperature was 110° under the wing, when put into the jar, and 105° when taken out.
Experiment 40. A green linnet was put into the same jar with 55·2 grains of ether, being six grains to 100 cubic inches. It was insensible in a minute and a half, and lay motionless, breathing naturally, till taken out at the end of a quarter of an hour. It moved its toes very slightly when they were pinched with the forceps, and it began to recover voluntary motion in two or three minutes. Temperature 110° before the experiment, and 102° at the end.
Experiment 41. A linnet was placed in the same jar, containing eight grains of ether to each 100 cubic inches. Voluntary motion ceased at the end of a minute. The breathing was natural for some time, but afterwards became feeble, and at the end of four minutes appeared to have ceased; and the bird was taken out, when it was found to be breathing very gently. It was totally insensible to pinching. The breathing improved, and it recovered in four minutes.
Experiment 42. 9·2 grains of ether, being one grain to each 100 cubic inches of air, were diffused through the jar, holding 920 cubic inches of air, and a frog was introduced. At the end of a quarter of an hour, it had ceased to move spontaneously, but could be made to move its limbs, by inclining the jar so as to turn it over. At the end of half an hour, voluntary motion could no longer be excited, and the breathing was slow. It was removed, at the end of three-quarters of an hour, quite insensible, and the respiratory movements being performed only at long intervals, but the heart beating naturally; and it recovered in the course of half an hour. The temperature of the room was 55° at the time of this experiment.
We find from the 32nd experiment, that a grain and a half of ether for each 100 cubic inches of air, is sufficient to induce the second degree of narcotism in the mouse; and a grain and a half of ether make 1·9 cubic inch of vapour, of specific gravity 2·586. Now the ether I employed boiled at 96°. At this temperature, consequently, its vapour would exclude the air entirely; and ether vapour, in contact with the liquid giving it off, could only be raised to 100° by such a pressure as would cause the boiling point of the ether to rise to that temperature. That pressure would be equal to 32·4 inches of mercury, or 2·4 inches above the usual barometrical pressure; and the vapour would be condensed somewhat, so that the space of 100 cubic inches would contain what would be equivalent to 108 cubic inches at the usual pressure. This is the quantity, then, with which we have to compare 1·9 cubic inch, in order to ascertain the degree of saturation of the space in the air-cells of the lungs, and also of the blood; and by calculation, as when treating of chloroform,
1·9 is to 108 as 0·0175 is to 1.
So that we find 0·0175, or 1–57th to be the amount of saturation of the blood by ether necessary to produce the second degree of narcotism; and as by Experiment 35, three grains in 100 cubic inches produced the fourth degree of narcotism, we get 0·035, or 1–28th, as the amount of saturation of the blood in this degree. Now this is within the smallest fraction of what was found to be the extent of saturation of the blood by chloroform, requisite to produce narcotism to the same degrees. But the respective amount of the two medicines in the blood differs widely; for whilst chloroform required about 288 parts of serum to dissolve it, I find that 100 parts of serum dissolve five parts of ether at 100°; consequently 0·05 × 0·0175 gives 0·000875, or one part in 1142, as the proportion in the blood in the second degree of narcotism; and 0·05 × 0·035 gives 0·00175, or one part in 572, as the proportion in the fourth degree.
In Experiment 42 the frog was rendered completely insensible by vapour of a strength which was not sufficient to produce any appreciable effect on the mouse in Experiment 31. This is in accordance with what was met with in the experiments with chloroform. Air, when saturated with ether at 55°, contains 32 grains in each 100 cubic inches; so that the blood of the frog might contain 1–32nd part as much as it would dissolve, which, although not quite so great a proportion as was considered the average for the fourth degree of narcotism in the mice, yet was more than sufficient to render insensible the mouse in Experiment 34.
There is a remarkable difference between the birds and the mice, in respect to the proportions of ether and air required to render them insensible, a difference that was not observed with respect to chloroform. In some experiments with ether on guineapigs, which are not adduced, they were found to agree with mice in the effects of various quantities.
The birds were found to require nearly twice as much; five grains to 100 cubic inches, the quantity used in an experiment between the thirty-ninth and fortieth, which is not related, may be taken as the average for the fourth degree of narcotism in these birds, with a temperature of 110°. By the kind of calculation made before, we should get a higher amount of saturation of the blood than for the same degree in mice. But as serum at 110° dissolves much less ether than at 100°, the quantity of this medicine in the blood of birds is not greater than in that of other animals; and, considered in relation to what the blood would dissolve at 100°, the degree of saturation is the same.