APPENDIX

The Notes refer to the Numbers in parentheses in the Text.

NOTE (1)

THE circulation of the blood continues for a little time in animals after the respiration has been arrested by the influence of ether, and it ceases, apparently, from want of respiration, and not from the direct effects of the ether. This I observed early in the year, but it was first made known by the Parisian physiologists. The reason of this, I believe, is not that ether is incapable of paralyzing the heart and blood-vessels, but that it sooner affects the medulla oblongata, and the nerves connected with it, than the ganglionic nervous system. Indeed, I have ascertained that such is the case, from observations I have made on frogs. If placed in air containing but 20 or 30 per cent of vapour of ether, they very quickly become affected, probably from the rapid absorption of the vapour by the skin: in a minute or two the respiration ceases, and they have every appearance of being dead, except that the heart can be seen pulsating on the under side of the chest. If they are now withdrawn, the circulation continues, the ether gradually evaporates by the skin, and respiration recommences, in a period varying from 5 to 15 minutes, according to the length of the previous exposure to the vapour: whilst, on the other hand, if they are allowed to remain in the air containing vapour, more ether continues to be absorbed, and in about five minutes the heart ceases to beat perceptibly, although its pulsations would continue for hours without the respiration, even in a frog immersed in water that has been deprived of its air by boiling. Some slight vermicular contractions of the heart, that would be visible on dissection, continue for a little time, and if the frogs are withdrawn from the vapour during this interval, and kept moist, they may yet recover, although they sometimes show no signs of life for an hour and a half. Although etherization and asphyxia resemble each other in some respects, yet the rapidity with which frogs are affected with ether, whilst they are so very slowly asphyxiated by privation of air, proves that they differ widely, and shows clearly enough that the effects of the vapour of ether are not due to its excluding part of the oxygen of the air by the space it occupies, as might at first, perhaps, be supposed. That such is not the way in which ether acts I ascertained in a more direct way in the beginning of the year, by supplying artificially the oxygen so displaced, when I found that the peculiar effects of ether were produced in animals just as readily as before. If hydrogen, nitrogen, or any neutral gas which does not support life, were mixed with the air, in even half the quantity that vapour of ether is commonly mixed with it, the oxygen of the air, over-diluted, would fail to be imbibed into the blood in exchange for carbonic acid, and the patient would suffer asphyxia, the blood being arrested in its passage through the pulmonary capillaries. The oxygen is often reduced by the vapour of ether to 10 or 11 per cent of what the patient breathes, whilst if it were reduced but to 16 per cent by a gas which is not absorbed, no increased efforts of respiration would prevent asphyxia from quickly supervening.[a]  That nothing of the kind takes place during the inhalation of ether depends on the circumstance that the vapour is absorbed as fast as it reaches the air-cells of the lungs, leaving the oxygen in its usual proportion per cent.; and to get enough of it the patient usually enlarges his respiratory movements instinctively, as he would do if situated on a high mountain, where the air is much rarefied.

NOTE (2)

When air is admitted to a liquid containing ether, the liquid parts with some of its ether to the air; whilst, if air containing ether is admitted to a liquid containing none, it parts with some of its ether to the liquid; and in either case a balance is established. The interposition of a thin animal membrane between the liquid and air, like that between the blood and the air in the lungs, does not interrupt this interchange. The quantity of ether that a limited portion of air will withdraw in the form of vapour, from a liquid containing it, is determined by the temperature and the quantity in the liquid: for instance, if the liquid is saturated with ether, the air will become saturated also, for that particular temperature; if the liquid is half saturated, the air can only withdraw as much as will half saturate it; and so on, in a direct ratio, as I have ascertained by experiments. It is not improbable that some of the ether inhaled is decomposed in the body; but this does not alter the question of de-etherization in this manner, for assuredly by far the greater proportion of the ether escapes by the breath unaltered.

Ether exists in the blood during etherization as a liquid, not as vapour. Although the temperature of the blood is a little higher than the boiling point of ether, yet it is capable of absorbing the vapour readily, and holding it in solution. 100 parts of water at 60° will hold in solution about 10 parts of ether, or rather more than 23 times their own volume of the vapour: at 100° -- the temperature of the blood -- water will absorb and hold in solution about half the above quantity, and it is capable of absorbing the vapour of ether, and holding it dissolved at all temperatures up to 212° , its own boiling point, but in a constantly diminishing quantity.  Blood, on account of its density, absorbs less ether than water at corresponding temperatures; but it is capable of absorbing more than it has ever the opportunity of doing in the process of etherization.

NOTE (3)

The quantity of water contained in washed ether is more than sufficient to saturate the driest air at any temperature at which it can be breathed; and that it does rise in vapour along with the ether, may be experimentally ascertained, by attaching two tubes containing chloride of calcium to an inhaler, or a Wolf's bottle, in which there is some ether, washed and not deprived of the water, and then passing air over the whole; when it will be found that the air, after parting with all its moisture to the chloride of calcium in the first tube, takes up water again along with the ether, and gives it up to the chloride in the second tube, in quantity increasing with the temperature.

NOTE (4)

The size of the patient is the only circumstance which I have observed constantly to influence the quantity of ether required to produce insensibility, when the inhalation goes on steadily; if the inhalation is interrupted, however, more ether is used, as the process has to commence, in some measure, afresh. The man who was the subject of excision of the elbow-joint by Mr. Liston, in University College Hospital, might seem an exception to this. The ether was finished soon after the operation began, although 3ij. had been put into the inhaler; I found afterwards, however, that it had not been all inhaled, but that a great part of it (owing to an irregularity in the volute of the inhaler I was using, by which the passage for air was much contracted at one place), had been splashed into the elastic tube, whilst the patient was breathing deeply and forcibly. Females generally consume less ether than males, but then they are usually of less stature and weight. Hard drinkers do not appear to require more ether than others, and are not more difficult to render insensible. The time occupied in producing complete insensibility varies with the activity and depth of the respiration; but it seldom exceeds two to three minutes in a child, or four to six minutes in an adult, when the inhalation is not interrupted; unless the vapour gets diluted to a greater extent, by the valve being kept open, or the face-piece not fitting, or by some other means.

NOTE (5)

There is no difficulty in distinguishing voluntary motion from excito-motory movements, or the rhythmic automatic ones, in a patient who is unconscious of what is occurring around. Voluntary motion is recognized as such at once, even in an animalcule under the microscope, but much more readily in one's own species. Both sensation and voluntary motion may exist in the second degree of etherization without consciousness, as in natural sleep, when a person feels the heat or the cold, and pushes off the coverlet, or folds it closer round him, according to circumstances, without waking; consequently, the assertion of the patient that he has had no pain is not to be considered a proof that there has been none, in cases where there have been unequivocal demonstrations of it. On the other hand, every little struggle or moan must not be considered a proof of pain, since it may be independent of the operation, or merely excito-motory, or the result of very obscure sensation. And when cries expressive of pain do occur, they must not be taken as a measure of the pain, for when the patient is unconscious he is not using the slightest self-control. There is no room for an opinion that the patients generally have pain, and are unconscious or oblivious of it; for when the ether is well administered, there is generally no expression of any kind by the features or voice, and a number of patients recover their mental faculties and special senses, whilst the sensibility is still so far blunted that the minor parts of an operation cause no pain.

NOTE (6)

Dr. Pring, of Weston-super-Mare, found (as he stated in the Lancet, May 1st), that ether will render arterial blood dark-coloured, and impair its coagulation out of the body; but a much larger quantity of ether was no doubt introduced than enters the blood during inhalation.

NOTE (7)

The method of giving ether with no other appliance than a sponge placed over the mouth and nostrils, which was introduced by Dr. Smith, of Cheltenham (1856 map: middle left), is one that will succeed in causing insensibility; and this is a happy circumstance that will extend the use of ether to many cases of emergency, in which otherwise the patients might be deprived of its benefits. In the cases of infants it is perhaps the best way of exhibiting ether, but for children of two years of age and upwards I have a small face-piece, and prefer to use the inhaler. The simple sponge is preferable, for all cases, to many of the apparatuses which were in use, and Dr. Morton, of Boston, U.S. (as appears by a communication he sent to the Lancet), uses it in preference to the inhaler he at first employed; but I cannot admit that it is equal to a good apparatus. It is an expensive means, as not one-half of the ether which is dissipated enters either the mouth or nostrils of the patient; and it is a means which does not admit of any kind of regulation as regards the strength of the vapour.

In large operations on the face, like that described in the section before Note (7), the administration of the vapour of ether per rectum-the method of Prof. Pirogoff, of St. Petersburgh -- would certainly be better than inhalation, if it is equally safe and manageable. The Professor, (I think I have read so), has removed the superior maxillary bone, under the influence of ether exhibited in this way. He recommends this plan, indeed, in all cases, as preferable to inhalation, on account of certain disadvantages and discomforts which he considers attend the latter; but, in all probability, he has not seen inhalation practised with a good apparatus, and I have not had sufficient experience of his method to be able to speak of its merits.

THE END

[a] See a paper " On the Pathological Effects of Atmospheres vitiated by Carbonic Acid Gas, and by a Diminution of the due Proportion of Oxygen." -- Edin. Med. Surg. Journ., Jan. 1846.