position. It is also important to notice that, unless proper care is taken, we may add the dangers of asphyxia to those of anesthesia. A plentiful supply of air is imperatively necessary with chloroform, and the fact that air can be freely admitted without interfering with the effect is one of the reasons that chloroform is in favor. Ether, on '.the other hand, will not act unless air be pretty wrell excluded. Many operators fail to get good results from ether, and give it up because, as they say, they cannot get the patient quiet. Most of those who use ether successfully are in the habit of keeping the towel or inhaler close to the patient's mouth, and by this means the preliminary intoxicating stage is passed. Other surgeons prefer to use ether first Yery lightly mixed with air, until the sensibility of the laryngeal mucous membrane is obtunded. In this way coughing is prevented. I have been under the influence of ether by both methods, and I must say I prefer the latter. The ether was given to me very successfully, and the recovery from the effect was rapid and perfect. By the* other method I was so completely prostrated that it was several hours before I could leave the operating room, and I am sure (although I could not have believed it if any one else had told me) that the odor of ether was perceptible to me in my own head for more than twenty-four hours after administration.

In relation to the condition of the kidney, especially in ether anesthesia, it appears that in cases of marked kidney disease, particularly in the now too common Bright's disease, anesthetics are more than usually dangerous. It appears that ether is especially obnoxious, and I have heard an experienced obstetrician say that he had abandoned its use in producing anesthesia in labor, using chloroform entirely. I do not know that it is possible to explain the specific danger from ether in these cases, but it is probably connected with the manner in which the ether is excreted. At any rate, it is now considered proper surgery to test the urine before using any of the stronger anesthetics.?

The topics chosen for this paper are too intricate and extended for a single essay. I should like to consider the physiological nature of the analgesic effect of rapid respiration, but I think I have taken up sufficient time, and I would be very glad to hear from those present concerning the questions involved.

Discussion.

Dr. Guilford. I would like to ask you what you consider the physiological action of nitrous oxide, and whether you have made any study of it and of the manner of its action?

Dr. Leffmann. I have never given sufficient attention tp it to be able to give what you might call an expert opinion. 1 think there is some resemblance in it to asphyxia, but I do not think it is asphyxia proper. I would like to know from some of the gentlemen present, who have had experience in the matter, whether the claim made by some parties who have used the gas, that they can prevent the paleness of the face under its operation, is true or not. I remember, from what I have seen in the office of Dr. Thomas, that the faces were quite pale. I have seen some in which the palor was very marked, and I have seen others in which it was not noticeable. It is possible that by an admixture of free oxygen with the gas, say to the extent of five per cent., the asphyxiating effect might be overcome and the anesthetic effect retained. I intended to have alluded to Paul Bert's recent experiment, in which he uses large volumes of air mixed with the anesthetic, giving, as he claims, better results. But wiiether the admixture of five per cent, of free oxygen would make any improvement, I cannot say. It is an anesthesia of partial suffocation, and I have sometimes thought it possible that the anesthesia of rapid respiration was of the same nature, and that a person breathing so quickly was subject to the same influence,—the true anesthesia of course being the special action.

Dr. Guilford. If nitrous oxide produced asphyxia, would it not be more dangerous than it is?

Dr. Leffmann. I think the primary stimulating effect of nitrous oxide would seem to show a physiological activity outside of the asphyxiating action. There seems to be an impression on the nerve centers of the body, such as you see in ether and chloroform, and in any other anesthetic. There is a resemblance in nitrous oxide to other anesthetics in that respect.

Dr. Tees. About ten years since, Dr. George Watt, of Ohio, made a series of experiments with nitrous oxide upon his own person. He reported the result in the Dental Cosmos. He said that he came very near death's door during one of the experiments. He found that, by enlarging the orifice in the inhaler, the patient could breathe easily, and change of color in the countenance as well as asphyxia could be avoided. JSTo doubt many of you have seen in children blowing trumpets the redness of the countenance. The effect of exhaling through a small mouth-piece, I think, is somewhat the same. About this time Dr. Kimmel had an interview with me, and I called his attention to Dr. Watt's article in the Dental Cosmos. Some time after this I accompanied a patient to his office, and noticed while she was under the influence of the gas that there was no change in the color of the countenance, and that she breathed easily, as if in a deep sleep. I spoke of this to Dr. Kimmel, when he told me it was owing to the purity of the gas, and also to the large hole in the mouth-piece, suggested to him by Dr. Watt's communication in the Dental Cosmos.

Dr. Gilbert. The less air you have mixed with nitrous oxide the the better success you have in controlling your patient. I think an inhaler with a large hole is preferable, because it is very difficult to breathe through a small aperture. I have tried one of this kind, and I think I had better results from it; but I noticed no difference in the skin, although it may act differently on different persons. About a year ago I was at Br. Thomas's, and found that he had an inhaler which he had invented with a larger pipe than we can get at the dental depots.

Dr. Guilford. The old plan of administering the gas, breathing in and out of the same bag, was very objectionable. I think the opening in the ordinary inhaler is as large as is necessary. If there is any asphyxia, it is not the fault of the inhaler. In twenty years of experience, in the great majority of cases, I have noticed this peculiar color of the skin, of the eyelids, and of the lips. Did Dr. Thomas explain why he made his large inhaler?

Dr. Darby. The mouth-piece of the inhaler used by Dr. Thomas is very large. He had it made so that the lips could be drawn tightly over it, and held firmly around it, thus preventing the ingress of any atmospheric air.

Dr. Kirk. This is a very interesting subject to me, and one which I have studied from time to time. I think the idea of Dr. Watt incorrect, as it is abundantly proven that the pallor or blueness of the features is due to the replacement of the oxygen in the blood by nitrous oxide. A patient of mine, whom I took to Dr. Kimmel, was very restless while under the influence of the gas. There was no pallor of the countenance, and he said that he felt no pain; but the anesthetic was very slow in taking effect. A slight admixture of air or oxygen greatly lessens this feature of its action, while at the same time its anesthetic property is diminished. A physician of Edinburgh published, some years ago, a series of observations which he had made upon the absorption spectra of blood, and he found that the venous color was due to the absence of oxygen, and not necessarily to the presence of carbonic acid, as is often assumed; such substances as hydrogen and ammonium sulphide, for instance, being capable of deoxidizing the hsemaglobulin, giving it thedark or venous color, and the absorption spectra of blood deoxidized by these means were identical with that of blood charged with nitrous oxide. I have noticed the same discoloration of the features in a somewhat less degree during the inhalation of pure hydrogen gas, which I have administered for experimental purposes, and carried to the point of anesthesia. It is very rapid in its action, and its effects but transient. When a certain amount of air or oxygen is administered with the gas you can avoid the pallor, but it is a difficult matter to decide just how much air can be given with the gas without interfering seriously with its anesthetic quality. I do not doubt that nitrous oxide acts in the main as an asphyxiating agent; life in the lower animals, such as pigeons, rabbits, etc., can be readily extinguished in a few minutes by keeping them in an atmosphere of nitrous oxide. Its inhalation is unattended with any feeling of suffocation, because the lungs are distended with a nonirritating, respirable gas, but one which is at the same time incapable of supporting life. In the same manner, it is said, one can starve to death without experiencing the pangs of hunger by eating clay. With regard to its permanently injurious effect upon the health, I know of a gentleman who was subjected to a somewhat prolonged operation under nitrous oxide, and subsequently died of diabetes. He always attributed his ill health and the kidney disorder to the inhalation of the gas, though it may have been only a coincidence.

Dr. Tees. All the patients I have accompanied to Dr. Kimmell have been thoroughly under the influence of the gas, und have slept quietly with unchanged countenances during the operations.

Dr. Kirk. I cannot see what harm there is simply in the pallor of the features. While I had charge of the mouths of the children at the Deaf and Dumb Institution I administered the gas very frequently, and often pushed the anesthesia to a profound degree. I have noticed that the first inhalation of pure air almost instantly restored the normal color of the countenance. Immediately upon the removal of the tooth from its socket the first few drops of blood that followed would be of the dark venous color, but in a moment the color would be changed to a bright arterial hue. It is simply a physiological fact that nitrous oxide does produce pallor of the countenance. It is therefore self-evident that the more nitrous oxide you administer the more pallor you produce; and more gas can be administered through a large inhaler than a small one. I do not think that a small-sized inhaler has anything to do with the pallor of the countenance.

Dr. Darby. I have been in the habit of administering the gas for many years. Sometimes I have noticed the pallor, and sometimes I have not. I have never felt alarmed when it has been most marked. I think it is the large quantity of gas and the absence of atmosphere that produces it. If the gas be mixed with common air, a much longer time is needed to anesthetize the person, and there is a greater liability of having the patient in an excited state, and often difficult to manage. The best results are obtained when the gas is given pure and rapidly inhaled.

Dr. Noble. I think that pallor is due to an absence of oxygen in the blood, because if blood be placed in a receiver, and the air is exhausted and oxygen introduced, the corpuscles will absorb oxygen, change their form, and become red in color. A want of color in the face indicates the condition of the patient. You can analyze the anesthetic effects by the appearance of the face, particularly of the lips.

Dr. Leffmann. The pallor of the countenance is one of the symptoms of asphyxia, and the point we would like to get at in reference to this question is, is asphyxia a necessary condition of anesthesia, or does nitrous oxide gas have an independent effect, and is the asphyxia only an accompaniment of it? If this be so, then we should so modify the gas as to get the anesthesia without the asphyxia. This is plainly so with chloroform; and Paul Bert claims that he has avoided danger from anesthesia by introducing air. If we can administer anything with this gas which will at all prevent the suffocation, and which will not diminish the insensibility to pain, we of course have an advantage. I had an idea, from some conversation with Dr. Kimmell, that his method consisted in mixing air with the gas.

Dr. Kirk. Prof. Elihu Thomson, of the Philadelphia High School, made a series of experiments some eight or ten years ago on the action of anesthetics, and I think performed the same experiment that Dr. Leffmann has just indicated. He found that a mixture of nitrous oxide and pure oxygen, in which the nitrous oxide was relatively the same as the nitrogen was to the oxygen of the atmosphere, was entirely without anesthetic effect, and apparently did not differ physiologically from ordinary air.

Dr. Chupein. I would like to hear whether Dr. Bonwill has made any further experiments in rapid breathing. Dr. Leffmann's paper touched upon that subject.

Dr. Bonwill. I was rather surprised to hear Dr. Leffmann speak of it at all, since I never claimed anything for it under the head of anesthetics. It does not belong there. I should be very happy to hear anything that he has to say on that subject.

Dr. Leffmann. I would like to say simply a word or two in justification of my position. I am pretty well assured that Dr. Bonwill did not correctly catch the phrase which I used. I used the expression analgesic effect of rapid respiration. I think that is the term which those who agree with him have preferred,—that it is not a condition of unconsciousness, or a suspension of the faculties, as anesthesia is, but a diminution of the sensibility to painful impressions. I have no clearly defined views on the subject, and I am not sure that any extended physiological explanation has been made. I only said that where an unusually rapid change of air occurs in the lungs, without allowing the air time enough to remain in the