Source:  Snow, John. Med. Times and Gazette, n. s. vol. 14, Jan. 17, 1857, pp. 60-62 (Part 1), Jan. 24, 1857, pp. 82-84 (Part 2).

On the vapour of amylene

By John Snow, M.D.

Part 1

We are indebted for the agents which have hitherto been inhaled for the prevention of pain rather to a number of accidental circumstances, than to any systematic and well-regulated investigation. In the course of his experiments on nitrous oxide gas, Sir Humphrey Davy found that severe pain arising from inflammation of his gums was relieved by breathing it, and he published the following opinion in the first year of the present century:--"As nitrous oxide in its extensive operation seems capable of destroying physical pain, it may, probably, be used with advantage during surgical operations in which no great effusion of blood takes place."* (*Researches concerning Nitrous Oxide, p. 556.) This sentence was read by hundreds, and listened to at public lectures by thousands, for the period of forty-four years, without any result, when the late Mr. Horace Wells, a dentist of Hartford, Connecticut, being present at a lecture by a Mr. Colston, was induced to request the lecturer to accompany him to his office, and to exhibit the gas to him, while another dentist, named Dr. Riggs, extracted a tooth which was troublesome. The tooth was extracted without pain, and Mr. Wells, after the effect of the gas had subsided, exclaimed, "A new era in tooth-pulling!" Mr. Wells administered the nitrous oxide in thirteen or fourteen cases of tooth-drawing, in Hartford, with a success more or less complete; and before the end of the year he repaired to Boston, to introduce his discovery to the Professors at the Massachusetts General Hospital. For want of a more important operation, the gas was tried in a case of tooth-drawing. The patient felt some pain, and the application was considered to be a failure. Mr. Wells returned to Hartford in disappointment. He expressed his opinion to his friends that nitrous oxide gas was uncertain in its effects, and not to be relied on; and he altogether abandoned the use of it until some time after Dr. Morton's discovery of the effects of sulphuric ether in preventing pain.

Ever since 1818 the vapour of ether had been known to produce exhilarating effects, similar to those of the laughing gas. The circumstance was mentioned in nearly all the standard works on Chemistry; and it was the practice for the Medical Students in many of the Colleges, both in England and America, to inhale ether on the day of the lecture on that medicine. Dr. Morton, a dentist of Boston, had been formerly in partnership with Mr. Horace Wells, and had been [60/61] present at his unsuccessful attempt to apply the nitrous oxide in the Hospital. On September 30, 1846, Dr. Morton administered the vapour of sulphuric ether successfully in a case of tooth-drawing, and shortly afterwards he administered it with success in some Surgical operations in the Massachusetts General Hospital. He thus established the power of sulphuric ether to prevent pain in the very institution where Mr. Horace Wells had failed in his attempt to introduce the nitrous oxide. Dr. Morton had apparently received some information respecting ether from Dr. Charles Jackson, Professor of Chemistry, but to Morton the merit is entirely due of introducing the practice of preventing the pain of Surgical operations. This is certainly true of modern times, and, probably, of all times to which history extends; for I believe that the use of mandrake by the Greeks and Romans, and of Indian hemp by the Chinese, must have been attended only with slight success in Surgical operations. I need hardly remind the Society that the inhalation of ether was soon extended to the prevention of pain in obstetric cases and a number of diseases, as well as in Surgical operations.

A medicine called chloric ether has been in use since 1831. It was first applied by inhalation with success in preventing pain by Mr. Jacob Bell, of London, early in 1847; and it was exhibited afterwards with occasional success in St. Bartholomew's and the Middlesex Hospitals, and in the private practice of Mr. Lawrence. This miscalled chloric ether is a solution of chloroform in spirit, and the insensibility it occasions when inhaled is entirely due to the chloroform, of which it contains about twelve per cent. Mr. Waldic, of Liverpool, being in Edinburgh in the autumn of 1847, explained these circumstances to Dr. Simpson, who had been the first to apply inhalation in the practice of midwifery, and was at the time paying great attention to the subject of anæsthesia. Dr. Simpson procured the chloroform in its undiluted state, and was the first to exhibit it in this condition, and the public and the Profession are indebted to him for its introduction to general use. Chloroform was immediately adopted, to the almost entire exclusion of ether, and has continued to keep its place, with a few exceptions, to the present time. At the Massachusetts General Hospital the use of chloroform was prohibited by the governors three or four years ago, on account of two accidents; and sulphuric ether has since been used, to the entire exclusion of chloroform. Ether is the agent employed in private practice in the town of Boston; and I have been informed that this is the case at Philadelphia, and in Europe, at Naples and Lyons.

Ever since the introduction of chloroform I have been of opinion that other agents would be met with more eligible for causing anæsthesia by inhalation. It seemed improbable that this one, which happened to be standing on the shelf of the Pharmaceutical Chemist for another purpose, should be better than all the very numerous volatile compounds which organic chemistry is daily bringing to light; and the continued use of chloroform is probably due to the circumstance, that hardly any one has made anæsthesia by inhalation a subject of constant and protracted investigation. I have from time to time made experiments on animals with a variety of substances, and I find that the agents which might be inhaled for the prevention of pain, in the absence of others which are more eligible, are extremely numerous. They include, among other things, carbonic acid and carbonic oxide gas, olefiant gas, the vapour of hydrocyanic acid and cyanogen gas, which last is contained, as I found, in the fumes of the puff-ball, which Dr. Richardson brought before the notice of this Society. The agents which I have exhibited as anæsthetics to the human subject, in addition to ether and chloroform, have as yet been but few. They are nitric ether, Dutch liquid, benzin or benzole, a bichloride of carbon, made by decomposing chloroform with chlorine gas, the monochlorinetted chloride of ethyle, and amylene, the subject of this paper. Nitric ether was exhibited also by Dr. Simpson, and Dutch liquid by him and Mr. Nenneley. These substances possess no advantage over chloroform, unless it be their slower action, while in other respects they are scarcely so agreeable. With regard to benzin, I discontinued the use it on account of convulsive tremors which it occasioned in a case of amputation in St. George's Hospital. I found that these tremors are a constant result when its effects reach a certain stage. I administered the chlorinetted muriatic ether in twenty surgical operations, in the summer of 1851, chiefly in King's College Hospital. Its sensible and physical properties and its effects are nearly the same as those of chloroform, but I thought that it might possess some advantage in the circumstance that, being less volatile, while its other properties are the same, it would be less liable to cause accident, even if incautiously used. I was, however, prevented from using it further, owing to the great difficulty of procuring it in a state of purity.

Amylene was discovered and described in 1844 by M. Balard, Professor of Chemistry to the Faculty of Science of Paris.* (*Annales de Chimie et de Physiqueem, 3me Serie, tom. xii. p. 320.) It is made by distilling fusel oil with chloride of zinc. M. Auguste Cahours had given this name five years previously to a product which is isomeric with amylene, and is made in nearly the same manner, but is now termed paramylene. Amylene itself is a colourless and very mobile liquid, of extremely low specific gravity. M. Balard has not stated the specific gravity in his essay, but I found that of the amylene made for me by Mr. Bullock,† (†[of] 15, Hanover-street, Hanover-square) and which is extremely pure, to be 0.659 at 56°. It is very volatile, boiling at 102º Fahr., and the specific gravity of its vapour is 2.45. It is composed of ten atoms carbon, and ten atoms hydrogen, and it bears the same relation to fusel oil, or amylic alcohol, that olefiant gas, or ethylene, bears to common alcohol. It burns with a brilliant white flame. It is soluble in alcohol and ether in all proportions, but is very sparingly soluble in water, being in fact a hundred times less soluble than many substances which are usually said to be insoluble in water. I have not yet been able to determine its solubility so exactly as I could wish, but as nearly as I can ascertain, 100 volumes of water dissolve two volumes of the vapour, at which rate one part of liquid amylene would require 10,220 parts of water for its solution. It has an odour somewhat resembling that of naphtha; some persons think the odour rather agreeable, and others think it somewhat unpleasant; the odour is not so strong or permanent as that of sulphuric ether, and does not remain long in the patients' breath. The vapour of amylene is much less pungent than those of ether and chloroform. It is therefore easier to breathe, and does not cause the choking feeling which sensitive and nervous patients often complain of in breathing chloroform. It has not caused any coughing to signify, except in two patients who were suffering from cattarrh, and in these cases the cough subsided in a minute or two.

I was not aware of the existence of amylene till a few months ago, or I should have tried it sooner; for I made inquiry in 1848 for a substance named eupion by Reichenbach, its discoverer, but was unable to obtain it. Eupion is a carbo-hydrogen, described as having all the physical characters which belong to amylene, though obtained in a different way; and I believe it is the same substance. Reichenbach obtained it from coal tar, but other chemists have not been able to make it.

Judging from experiments which I had made on analogous substances, there could be no doubt of amylene causing insensibility when inhaled; but I could not tell, without actual trial, whether it might not be too powerful, or otherwise unpleasant in its action. I made a number of experiments in 1848,‡ from which it appeared that each definite degree of narcotism was occasioned by an amount of the narcotic agent, bearing a certain relation to the whole amount which the blood is capable of dissolving, and that this relation was nearly the same in regard to ether, chloroform, and several allied substances. For instance, a very complete state of insensibility, which I named the fourth degree of narcotism, was caused by the presence in the blood of 1-28th part as much chloroform as it was capable of dissolving; and that the same state of insensibility was also occasioned by 1-28th part as much ether as the serum of the blood was capable of dissolving. The same relative amount of nitric ether produced the same degree of narcotism. In the case of bromoform and of bromide of ethyle, it was 1-27th part, with Dutch liquid it was 1-25th part, and with bisulphuret of carbon it required one part in 31 of what the blood was capable of dissolving, to induce the fourth degree of narcotism. Benzin was the only agent among those which I examined at that time which offered any great deviation from the others in the relative amount of its vapour which was required to be absorbed, in order to induce a definite degree of narcotism. To [61/62] induce the fourth degree of narcotism by benzin it required 1-17th part as much as the blood is capable of dissolving. Now, benzin bears a great resemblance to amylene, being, like it, a carbo-hydrogen, the composition, however, being different. (‡See Medical Gazette, Vol. II., 1848, "On Narcotism by the Inhalation of Vapours.")

The amount of amylene which requires to be absorbed is far greater in relation to the quantity which the blood would dissolve than in the case of benzin. I found, from some experiments which I made on guinea-pigs, mice, and linnets, that to cause the fourth degree of narcotism requires about 1-5th part as much amylene as the blood would absorb, to cause the second degree 1-10th part as much, and to cause the third degree, which is as far as I have carried its effect in the human subject, it requires an intermediate portion, or about 15 per cent. I found, for instance, that to induce the fourth degree of narcotism in a guinea-pig, it required that the air in the jar in which it was enclosed must contain 20 per cent, or a fifth part of its volume of the vapour of amylene. The temperature of the guinea-pig is, however, just that of the boiling point of amylene, when the tension of its vapour balances the weight of the atmosphere; and, consequently, the blood passing through the lungs could not take up, in the above experiment, more than 1-5th as much as the whole quantity which it could dissolve. This is a point capable of direct proof. The entire quantity of amylene which is absorbed during inhalation must, however, be extremely small, owing to its very sparing solubility. Taking the solubility of amylene in watery fluids to be what I have state above, viz., 1 part in 10,220, and taking the quantity of serum of the blood in the human adult to average 410 fluid ounces, as estimated by Valentin, then the amount of amylene circulating in the body in the third degree of narcotism would be not quite 3 minims. The above calculation of the small quantity absorbed into the blood is confirmed by some other experiments which I made. I introduced 14 minims of it into a bladder with 200 cubic inches of air, and after breathing it backward and forward a few times I became very nearly unconscious, and experienced, in fact, more effect from these 14 minims than from 45 minims breathed to and from a large bladder, holding 670 cubic inches.

Viewed in the light of the small quantity which requires to be absorbed into the system to cause insensibility, amylene is a very powerful agent; but when considered in relation to the quantity which is consumed during inhalation in the ordinary way, it is far from being powerful. This arises from the great tension and the small solubility of the vapour, in consequence of which it is, with the exception of a small fraction, expelled from the lungs again without being absorbed. In this respect it resembles, to a great extent, the nitrogen gas of the atmosphere, with which the lungs are always four-fifths filled, while the blood contains but a few cubic inches. It takes from three to four fluid drachms of amylene to cause insensibility in the adult, while less than a drachm of chloroform is usually sufficient. The quantity of sulphuric ether required to cause insensibility in the adult is eight to ten fluid drachms, one-half of which is absorbed into the blood. In a protracted operation of half-an-hour or upwards, the quantity of amylene used is greater even than that of sulphuric ether; the small quantity of the former which is absorbed is quickly exhaled again from the lungs, and has to be constantly replaced; while the large amount of sulphuric ether, when once absorbed, takes a much longer time to exhale in the breath. This constitutes some objection to the use of amylene in protracted operations, as it adds to the expense.

Part 2

It follows from the experiments above alluded to that the patient must breathe air containing not less than fifteen per cent of vapour of amylene, in order to reach the third degree of narcotism, or that condition in which the pupils are usually contracted and inclined upwards, consciousness and voluntary motion being entirely suspended, but the muscular system not necessarily relaxed. As 100 minims of amylene produce 86.7 cubic inches of air a minute, and frequently more, the amylene is consumed at the rate of rather more than a fluid drachm in the minute, and in this way insensibility is caused in three minutes, or rather less. If the vapour is not inhaled in a sufficient volume the patient will not become insensible by continuing the inhalation for however long a time, consequently the quantity of vapour must be increased, or it will not succeed. [82/83]

The amount of vapour of amylene that the air will take up at ordinary temperature is far more than enough to cause insensibility, even when but partially saturated. When fully saturated the quantity of vapour at different temperatures is nearly the same as in the case of sulphuric ether, a table of which I laid before the Society in 1847. At the following temperatures I find that air, when saturated with vapour of amylene, contains the subjoined quantities in each 100 cubic inches, when the barometric pressure is 30 inches:--

53° Fahr. . . .

38.6 cubic inches













In the ordinary process of inhalation, however, it is not easy to get the air even half saturated with vapour, owing chiefly to the cold produced by the evaporation of the amylene. When a piece of blotting-paper is wetted with amylene it usually happens that the absorption of caloric by the evaporation causes, first, a deposition of the moisture of the atmosphere, and then the freezing of the water, so as to occasion the appearance of hoar frost on the paper. This extreme cold would, of course, limit the evaporation very much, but it is counteracted in a great measure by the bath of cold water which surrounds my ordinary chloroform inhaler, the water supplying the caloric which is abstracted by the vapour of amylene; and since using this latter agent I have had the apparatus somewhat enlarged, in order to afford a larger surface of bibulous paper, and a somewhat greater quantity of water; by this means I find that I have the power to exhibit a sufficient volume of vapour, even in this weather, when the temperature of the water, although kept in a dwelling-room, is often as low as 50?.* (*The inhaler is made by Matthews, Portugal-street.)

After making several experiments on small animals with amylene, and inhaling small quantities of it myself, I first administered it in King's College Hospital, on the 10th of November last, to two boys about 14 years old, previous to Mr. Samuel Cartwright extracting some teeth. I had but a few drachms, and being very sparing of its use, it did not entirely remove consciousness in either case, and the pain was not altogether prevented; the effects, however, as far as they extended, were so favourable as to encourage a further trial, which was made in the same institution on December 4.

On this occasion I exhibited the amylene to four patients--two men, a young women, and a girl of 10 years old; it occasioned complete unconsciousness and absence of pain in each case. Each of the men inhaled for three minutes, and used half a fluid ounce of amylene; they each had a tooth extracted by Mr. Cartwright, and awoke and left feeling quite well, just six minutes after entering the room. The two females inhaled for four minutes; the elder one, who was not in good health, complained of dizziness afterwards, which, however, passed off in about ten minutes. On December 11, I exhibited the amylene again in five more cases of tooth-drawing in King's College Hospital, with very similar results to those obtained in the previous cases; and on December 13, I administered it in some more important operations.

In one case Mr. Fergusson performed an operation for fungus of the testicle; Mr. Bowman removed some diseased glands from the groin; and there were two cases of tenotomy, in one of which forcible extension of the knee was made.† (†See Med. Times and Gazette, Dec. 20, p. 624.)

On December 27, I exhibited the amylene again to a girl three years and a half old, a patient of Mr. Fergusson, who had inhaled it on the 13th; the effects were the same; she inhaled for two minutes before the operation was commenced; there was no sign of pain, and she awoke almost the moment the operation, which consisted in the division of some additional tendons near the foot, was concluded. On January 3rd, I administered amylene again in three operations performed by Mr. Fergusson. One of these was an operation for the completion of a new nose. There was a little delay, owing to the difficulty of fitting the face-piece to the new organ; and the man inhaled for six minutes before the operation was commenced, but half this time he was making no progress towards anæsthesia. There was much less rigidity and struggling than when he inhaled chloroform a few weeks previously. After the operation was commenced the vapour was exhibited on a sponge as well as circumstances would permit, and, although the patient flinched a little once or twice, the anæsthesia was as complete as is usual in such cases; for there is generally some difficulty in keeping up the insensibility during operations on the face. At one part of the operation the man entered into a rambling conversation, which had no connexion with the use of the knife, of which he seemed entirely unconscious.

On the 7th inst., I gave the amylene whilst Mr. Henry Lee performed amputation above the knee in a girl who underwent excision of the knee-joint a few weeks ago. She had suffered from secondary abscess, was extremely week, and had a pulse of 150 in the minute. The vapour was exhibited to the patient in bed, before her removal to the operating table. There was an examination of the knee before the operation, and the anæsthesia was kept up till the dressings were applied, which was twenty-five minutes from its commencement, and nearly three fluid ounces of amylene were used. She went through the operation extremely well. There was no sign of pain, and the pulse remained the same throughout.

I have again given the amylene to-day in three operations performed by Mr. Fergusson in the Hospital. The first was an operation by ligatures on a large nævus of the lip in a young man; the next was lithotomy in a child about three years old; and the third was the removal of a large melanotic tumour from the groin of a middle-aged man. The patients were each brought under the influence of the vapour in from two to three minutes. The prevention of pain was complete in all, and the two men were partially conscious during a great part of the operation, the last patient repeating a number of verses with perfect accuracy while the vessels were being tied. These make twenty-one operations in which I have administered amylene.

In the use of amylene absence of pain has been obtained with less profound coma than usually accompanies the employment of chloroform and ether. There are some cases, indeed, in which the minor parts of an operation, under these latter agents, may be performed without pain while the patient is in a semi-conscious state, or even altogether conscious, but they form an exception; while in the use of amylene the patient has very often been half-conscious during the operation. In operations under chloroform the patients usually indicate the necessity of repeating the inhalation by a tendency to flinch or cry, without showing any signs of consciousness; but in the use of amylene they have more frequently begun to look about and to speak before showing any sign of pain. There are some patients who will not lie still under the Surgeon's knife while chloroform is being used, unless its effects are carried so far that the breathing is on the borders of being stertorous, but I have not yet met with any such case in using amylene.

I made the observation early in the practice of inhalation for the prevention of pain, that the anæsthesia, or loss of common sensibility, does not always keep pace with the amount of narcotism of the nervous centres, as evinced by coma, etc., even in the same case; and I offered an explanation of the circumstance to this Society* in the fact that narcotic vapours act on the nerves throughout the body, as well as on the brain; and there were certain circumstances connected with the circulation, why at one time, or in one case, the brain, and at another time, or in another case, the nerves should be most influenced. (*See Medical Gazette, 1848, Vol. II.) I have not at present, however, arrived at any conclusion as to the reason why amylene prevents pain with apparently a less amount of coma than ether and chloroform.

The pulse is generally increased in frequency and force during the inhalation of amylene to a greater extent than happens with chloroform. There has generally been an increased redness of the face during the first part of the inhalation, and in one case there was profuse sweating, a phenomenon also met with, now and then, under the influence of chloroform.

The respiration is very often accelerated during the inhalation of amylene, about as often, I think, as with ether, and more frequently than with chloroform. Dr. Sibson and I found that the breathing was greatly accelerated by these latter agents in a dog, after he had divided both the pneumo-[83/84] gastric nerves, so that the phenomenon is not occasioned by the local effect of the vapour in the lungs.

There has not been much increase of saliva from the use of amylene, and I have not yet met with the profuse salivation which is often troublesome in the employment of chloroform and ether. What is of most importance of all, however, if it should continue, is, that there has been no sickness in any case, nor any of the depression which so often precedes and accompanies the sickness from chloroform and ether.

There has been hardly any struggling or rigidity in any of the patients, although several of them being robust men, a good deal of both might have been expected before complete insensibility, if chloroform had been the agent employed.

A point of great interest connected with amylene is its probable safety or danger. While I cannot venture to predict for it the absolute safety which seems to attend sulphuric ether under all circumstances, I confidently trust that it will be perfectly safe with careful management. Although the use of ether was commenced when there was no experience in the production of insensibility by inhalation, yet there seems to have been no fatal accident from its effects during its very extensive employment. It has, indeed, been alleged that it has proved fatal in two instances; but in one of these cases, which occurred at the Hôtel Dieu of Auxerre in July, 1847, the patient probably died from want of air, owing to a defective apparatus; the inhalation was persevered in for ten minutes, although there were alarming symptoms the greater part of the time. The other case happened at the Hôtel Dieu of Lyons, on August 26th, 1852. M. Barrier was removing the superior maxilla, affected with osteo-sarcoma, in a woman in a bad state of health, who was seated in an easy chair. She died of sudden syncope in the middle of the operation, a result which occurred in a similar operation by an eminent Surgeon in this metropolis before ether was introduced. From the history of the inhalation and of the symptoms, I feel sure that the loss of blood was the cause of death, and not the ether. There have, however, been several sudden and fatal accidents in the use of chloroform; and although they are extremely few in comparison with the multitude of cases in which this agent has been used, they are, nevertheless, much to be regretted.

I have on former occasions explained the reasons why accidents have happened in the use of chloroform, and not in the use of sulphuric ether, and I will now very briefly recapitulate these reasons. The quantity of ether which a patient requires to inhale in order to be made insensible occupies about 400 cubic inches in the form of vapour, and necessarily mixes in the process of inhalation with not less than 800 cubic inches of air, and makes a volume of at least 1200 cubic inches, which can only be inhaled by a number of inspirations; and no great proportion of the whole quantity can ever be in the lungs at one time. The quantity of chloroform, on the other hand, which when inhaled will cause insensibility in the adult is only about 36 minims, which occupies only a little more than a pint in the form of vapour, and this, if precautions be not taken to prevent it, may be mixed in the process of inhalation with less than a gallon of air, which may all be inhaled in a few inspirations, and a great proportion of it might be in the lungs at one time. For the above reasons ether cannot produce its effects except gradually, whilst chloroform is capable of acting almost instantaneously, when the point of safety may easily be overstepped. Chloroform, ether, and similar agents have the power, when pushed to excess, not only of arresting the respiratory movements, but of stopping the action of the heart by their direct physiological effects. It takes, however, a larger quantity to paralyse the heart than to suspend the action of the respiratory muscles; and as ether can only enter the circulation by degrees in the process of inhalation, it is necessary to open the pericardium and blow the vapour on the surface of the heart, or to perform some other manaeuvre in order to show the direct action on the heart. When animals are made to breathe ether till they die, the action of the heart continues after the ordinary breathing has ceased; and, at the moment when the action of the heart is stopping from over distension, there are generally two or three deep gasping inspirations, which set about the recovery of the creatures, unless they are made to breathe more ether during these gasps. These are also the phenomena which occur in killing animals with chloroform, if care be taken to have the vapour so diluted that the air they breathe does not contain more than five per cent of it. But when the air breathed contains eight or ten per cent of vapour of chloroform it acts so quickly, and is absorbed in such quantity into the blood as it passes through the lungs, that not only are the brain and nerves of respiration narcotised, but also the nerves of the heart, and the animal is beyond recovery. The above facts explain, in my opinion, both the great safety of ether, under all ordinary circumstances, and the great care required with chloroform to ensure its safety.

The quantity of amylene which the patient requires to inhale to cause insensibility is intermediate, as stated above, between that of chloroform and that of ether, and so also is the amount of air which must be mixed with it; and it is my opinion that the cold produced during its evaporation would, in all the ordinary methods of inhalation, prevent the air from taking up a quantity of the vapour which would be dangerous.

The relative advantages and disadvantages of amylene may, as nearly as I can judge, be summed up as follow:--In regard to its odour, it is more objectionable than chloroform, but much less so than sulphuric ether. The odour of any volatile substance is, however, no longer perceived after a patient begins to inhale. In respect to its pungency, it has a great advantage over both ether and chloroform, being much less pungent than either of them. Thus, whilst the patient, especially if a female, often complains of a choking feeling and want of breath in commencing to inhale chloroform, and two or thee minutes are lost before the vapour can be inhaled in any useful quantity, she can begin to inhale the amylene of full strength within half a minute from commencing, and the operation may generally be begun within three minutes. In the amount which suffices to induce insensibility it is intermediate between chloroform and ether, chloroform having the advantage. Amylene has the advantage in preventing pain with a less profound stupor than that occasioned by the other agents, and in the ready waking and recovery of the patient it has an advantage over chloroform, and a still greater advantage over ether. Its probable safety I have spoken of; and the greatest advantage of all, if it should continue to be met with in all cases, is the absence of sickness from its use. The almost entire absence of struggling and rigidity may also be mentioned as an advantage of amylene over ether and chloroform.

I do not venture to predict that amylene will supersede the use of other agents, but I trust that the subject in its present stage is sufficiently interesting to warrant me in bringing it before the notice of the Profession, and I consider that the results obtained with the amylene have been so satisfactory as to encourage the further use of it. It would probably become cheap if there should be a demand for it.