This table shows that the often repeated opinion, that the causes of yellow fever could not exist unless where the mean summer temperature reached 80°, is erroneous, the disease having prevailed, as an epidemic, at Newcastle, with a mean temperature 10° lower, and continued until the mean temperature had fallen 5° more.

Mere heat did not seem sufficient to call the causes of the disease into operation; for in July and August there was none, and, though a few cases occurred in September, it did not attain its greatest force until October and November, when the temperature was diminishing. It ultimately disappeared about December 21st, when cool weather came on, accompanied with strong northerly winds and some rain. It will be remembered that the disease stopped about November 10th, that a few cases occurred in the latter part of that month, and that early in December they were more numerous, but that the last was on the 21st of that month. Taking the mean temperature for periods of ten days in each month, they are

The periods of aggravation of the disease were thus coincident with increased temperature during the day; such increase, however, was accompanied by a clearer sky and stiller state of the air than when the mid-day temperature was less. There were unfortunately no observations of the absolute maximum temperature of the day, or of the amount of the sun's radiation.

The dew point was not observed during the course of the epidemic, but the quantity of rain collected was as follows:

pretty closely with those for 1856 as to temperature and distribution of rain, while in 1858 there was no serious disease:

From this table it appears that the occurrence of the disease was preceded by a moderate quantity of rain; and its cessation, in November, soon took place under the influence of the heavy rains which commenced on the 4th. The causes of the fever, however, do not seem to have been altogether removed by the rain, but their action merely suspended, or rendered less intense for a period, but soon resuming their force with a return to dry and warm weather. Thus, after the cessation on November 10th, the rains went on to the 14th, and on the 15th there was fine weather, which was terminated by heavy rain on the 18th, continuing to the 21st inclusive. A case of yellow fever occurred on the 21st, which proved fatal. A man died in the hospital with black vomit on the 26th; and other cases appeared in the officers' quarters above the hospital, though it was not before December 3rd they again showed themselves in barracks.

This fact of the suspension of yellow fever under the influence of heavy rain is one of much importance; it has been observed in every epidemic of yellow fever at Sierra Leone; and while cases of the yellow form of the disease, in its most malignant character, have shown themselves in the breaks of the rains, or at their termination, the disease which appeared during the continued heavy rain was always pure remittent fever, and of that there was generally no scarcity. Can this he explained on the assumption of yellow fever being propagated by specific contagion? It seems much more in accordance with fact to conclude, that the origin of yellow fever is intimately connected with (though not altogether dependent on) some local emanation, the production of which is either suspended or modified by heavy rain, but which, on a return to dry weather, may again be produced with its former properties.

The above facts with reference to Newcastle seem to leave open no other conclusion, than that the yellow fever there in 1856 arose from local causes. Whether similar causes were in operation there in other years, and if so, why they did not lead to a similar result, are questions that the present information on the subject does not admit of being answered. It would seem, however, that in addition to the ordinary local causes of disease, an epidemic constitution is necessary to account for the prevalence of fever.

Much difference of opinion seems to exist as to the nature of an epidemic constitution; some limiting its influence to a comparatively circumscribed locality; others claim for it a more extended operation, but assert at the same time that its effects should be manifested by the same form of disease in all places within its sphere of action. Both views seem the result of overstrained deductions from too limited observations; as there is reason to believe that a more extended investigation would show that an epidemic constitution influences mortality from all forms of disease, and that its operation may be traced nearly contemporaneously from Hindostan to Mexico, and from Lapland to the Cape of Good Hope.

It will be sufficient, to prove the existence of an epidemic constitution in the present instance, to state that during the summer of

1856 yellow fever prevailed pretty extensively in the West Indies and around the Gulf of Mexico; and was therefore sufficiently general to warrant the conclusion of there having been something in operation beyond mere local influences.

While engaged on this paper I learned that some of the medical officers at Newcastle were of opinion that yellow fever was imported there from Stony Hill. With the view of getting every information on this point, I called for the opinions of Staff-Surgeon Foss, Surgeon Jopp, and Assistant-Surgeon Tobin, 36th Regiment. The first and last have expressed their belief that it arose from local causes, and was not imported. Dr. Jopp thought it had been imported, and his reasons for that opinion are contained in his official Report of the Newcastle Epidemic of 1856.'

[We are indebted for Mr. Lawson's able and interesting account of this epidemic to the courtesy of Mr. Alexander, Director-General of the Medical Department of the Army. Independently of the merits of the communication, a record of an outbreak of yellow fever at a station about 4000 feet above the sea level-an elevation considered, until of late years, to bestow an immunity from this scourge of hot climates must be extremely interesting, more especially to those engaged in the investigation of climatological pathology. We are sorry that we cannot afford space for much valuable matter contained in the appendices to Mr. Lawson's paper. Among other subjects of interest, we more particularly allude to the Reports on the Epidemic by Staff-Surgeon Foss, Assistant-Surgeon Tobin, and Dr. Jopp, Surgeon to the 36th Regiment. The two former gentlemen briefly state their opinion that the disease at Newcastle in 1856 was of local origin, and not imported into that station; while Dr. Jopp, in a lengthened communication, adopts the view that the fever first appeared in the low lands, and was subsequently propagated to Newcastle by contagion.]

ART. II.

Remarks on Anaesthesia, and the Agents employed to produce it. By GEORGE HAYWARD, M.D., late Professor of Surgery in the Massachusetts Medical College, Boston, U.S.A.

THE discovery by which surgical operations can be rendered painless is one of the greatest connected with our profession, second only to that of vaccination. It is a blessing to the human family that cannot be overrated; and having been among the first to make a successful use of it in surgical practice, I thought that a brief sketch of the history of anesthesia, and some remarks on the comparative value of the agents employed to produce it, would not perhaps be uninteresting.

It was my fortune to perform the first capital operation on a patient rendered insensible by the inhalation of sulphuric ether. This was done on November 7th, 1846, at the Massachusetts General Hospital,

On September 30th preceding, Dr. Morton, a dentist, administered it to a man from whom he extracted a tooth, without causing pain. Almost immediately after, he requested the late Dr. John C. Warren, who was at that time the acting surgeon at the hospital, to use it at that institution. Dr. Warren consented. It was inhaled by a patient, with partial success, on whom Dr. Warren operated on October 16th. The operation was the removal of a nævus from the face. On the day following I extirpated a large fatty tumour from the arm of a female, who was made wholly unconscious and insensible by the inhalation of the ether. The operation lasted seven minutes.

At that time Dr. Morton was, I thought, the only person who knew what the anaesthetic agent was. On November 1st I took charge of the surgical department of the hospital, and in a day or two after Dr. Morton asked me if I were willing to allow him to administer his 66 composition," as he called it, to a female whose limb I was about to remove above the knee. I told him I would not, unless I knew what the article was, and felt confident of the entire safety of its administration. He at once told me that it was rectified sulphuric ether. He allowed me to communicate this to my colleagues, with an understanding that it should not be made known publicly, until he had obtained a patent, for which he had already applied. On the following day the operation was performed, in the presence of more than two hundred spectators.

It rarely falls to the lot of a professional man to be the witness of a scene of more intense interest. The operating room was crowded. Many were obliged to stand. Besides the class of students in attendance on the lectures, numbering more than a hundred, and many of the principal physicians and surgeons of the city and neighbourhood, there were present several clergymen, lawyers, and other individuals from the various callings of life. When I entered the theatre, before the patient was brought in, I found it, to my surprise, filled in every part, except the floor on which the table stood, with persons on whose countenances was depicted the almost painful anxiety with which they awaited the result of the experiment they were about to witness. I simply told them that I had decided, with the advice of my colleagues, to allow the patient, on whom I was to operate, to inhale an article which was said to have the power of annulling pain. The patient was then brought in. She was a delicate-looking girl of about twenty years of age, who had suffered a long time from a scrofulous disease of the knee-joint. It had at length suppurated; there were extensive openings into the cavity of the joint; the cartilages were ulcerated and partly absorbed; the bones carious, and symptoms of hectic fever had already made their appearance. As soon as she was well arranged on the table, I told her that I should let her breathe something which, I hoped, would prevent her from suffering much from the operation, and that she need not be afraid of breathing it freely.

As the ether was at the time administered by means of a large and clumsy instrument, which required to some extent the co-operation

of the patient, it was desirable that the amputation should be done as rapidly as possible. Everything, therefore, was arranged with this I decided to perform the flap operation. One person was to compress the artery, another to withdraw the flaps, a third to hand the instruments, and a fourth to watch the pulse. I grasped the patient's limb with my left hand, and held the amputating knife behind me in my right, carefully concealed from her view. The mouthpiece of the inhaling instrument was then put into her mouth, and she was directed to take long inspirations. After breathing in this way a short time, the nostrils were compressed, so that all the air that went into the lungs must first pass through the machine, and of course be mixed with the vapour of the ether. She breathed with perfect ease and without struggling, and in about three minutes from the time the instrument was put into her mouth, Dr. Morton said, "She is ready." A deathlike silence reigned in the room; no one moved or hardly breathed. I passed the knife directly through the limb, and brought it out as rapidly as I could, and made the upper flap. The patient gave no sign of feeling or consciousness, but looked like one in a deep quiet sleep. Every other person in the room took a full inspiration that was distinctly audible, and seemed to feel that they could now breathe again. The second flap was then made, the bone sawed, five arteries were tied, and as I was tightening the ligature upon the sixth and last, she groaned, being the first indication of sensibility that had been given. Nothing more was done than to bring the flaps together, cover the stump with cloths dipped in cold water, and apply two or three turns of a roller to keep them in place. Her consciousness soon returned; she was wholly ignorant that the operation had been done. For some time she would not believe it, and said that she had felt nothing till I tied the last artery. The operation lasted a minute and threequarters, not including the time required to tie the arteries. I did it rapidly, though it has been done in less time, because I feared that the insensibility might pass off, and we had no means then as we have now, of continuing it as long as is necessary.

Patients who have inhaled ether, when its effects are at first passing off, are usually bewildered, not easily contented, and by no means inclined to do as they are desired. It would be almost impossible to persuade one of them at such a time to breathe through the instrument that was then in use. At present, fortunately, we can keep up the state of anesthesia as long as we wish, by administering the agent employed for this purpose by means of a sponge. This simple contrivance was first used at the Massachusetts Hospital.

The patient whose case I have just spoken of recovered rapidly from the operation, was in good health when I left home eleven years after, and I have no reason to suppose that she is not so at the present time.

It will be readily believed that a result so successful, and witnessed by so many intelligent persons, made it impossible to doubt the anæsthetic power of the agent employed, and what this was very soon became known. In an almost incredibly short space of time, numerous