AN EARLY ETHER VAPORIZER DESIGNED BY JOHN SNOW A Treasure of the Wood Library-Museum of Anesthesiology

ROD K. CALVERLEY University of Califarnia, San Diego, California, USA

he achievements offohn Snow (1813- offer no impediment to the most rapid inspira- 1858) are respected by anesthesiologists tion; and to meet this requirement it must be of all countries. His publications, panicularly wider than the trachea. . . ."r Although recent the 88-page monograph "On the Inhalation of teconstnrctions of this device are on display in the Vapour of Ether in Surgical Operations," British museums, originals are not. A fortuitous first published in September 1847, are regularly discovery was recently made in the United reprinted and are now more widely read than are States at the American Society of Anesthesiolo' the works of any other l9th-century pioneer of gists' Wood Library-Museum (WLM), Park anesthcsiology. Scholars are deeply impressed Ridge, Illinois. A previously unappreciated by the broad scope and rapid development of his instrument has been identified as an authentic scientific observations. Clinicians admire inhaler of lohn Snow's design. It now ranks Snow's ability to relate his research to clinical among the most prized objecs of the WLM practice. Distinguished investigators believe that collection. John Snow's underslanding of the scientific Visitors to the WLM marvel that a proto- foundations of anesthesia were unequaled for type of Snow's inhaler could have been de- almost a century. signed, introduced in the medical literature and An example of Snow's skill in intermin- marketed commercially within a month of gling practical concern and scientific observa- Snow's first having witnessed ether anesthesia- tion is his ether inhaler, shown on page 17 of his From the moment when the inhaler was identi- 1847 monograph (Figure l). As the accompany- fied, I have been curious to leam the history of ing text reveals, he selected its components its development. How could Snow have carefully. For example, he chose a breathing prepared it so quickly? Did he create an original tube which ". . . ought to be so capacious as to design or did he re-assemble components

9l Fig" 1. t*hrr S**r'i* Fisral ${*difrr:*tis* *f hi$ fith€r lnhalcr" devined fbr*ther appllei*tions? If xco vrhat was re*r:*tty pr*h*s*d f*r th* library"As he their original puryase?These qnesNicns reflerted surveyetl the shelves. he saw ths bsx aild my ignorance of l9th-century technologr, a e*sually pl**erl it en *tabte wirh the comrneilr defieieffiycwFqunde.d by alack*f nrcs*s tF that it was bcliEved m be an early nitrous oxide .loumatrs of thst period. Recent $pportunitiss tCI inhaler. correspond with British schr:lim and ta visit While the group moved $n t$ in$pect slher historicd libraries ia Britain, have given me a objects, I opened thc box. The largest obje*s better {rndsrstending af thc origins of ths within it we{e a csiled tube and a black rncni vap*ril*r'r {sffip*{ts,ftt$. For readers who, tike tin, A cursary exanrination showed that the m*,enjlry r***lving historical pu;*les. I rvculd rimall, circular and ruther shallow tin. about 5 tike lc',***crih* my "p*th of discsvery" *hronc- inshcs in,,*i*r*ct*r aad ?-1n inches deep. could togicdly kom when I frrst saw this intriguing not hsve been constructed tB contain a ga*; it devieq. h*d t*r hav* bseftd&signed t* r*qe-iv* x:li,#lid, whiqh from thevelumee$nt*inod w*nlik*ly to trdentificction of tfu Anesthcsia Inhnler be ethcr. Although slightly rust€d, the metal tin In l9?9 the Trustess of the WLM pur- *herrsd $$ rnarks uf usa Wittr * rdini*i*n's shaxnd aH.*A*acst*esis lfihsler"- frsm $ims* curi**ily, I ass*mhled the components; a rourrd Kay, s Lcrd*,n ffr*iqs€ d**I*r fsrf,54$, lt* metfll vaporizing chamber, s hras$ quadrant provelrance was, gnd still rcmains, unknown. vslve which *ould bd turn*d to allow the For nn*ny years thereafter it rested undisturbed in*pire.d vspor to be dilutcd with room air, a ?8- in its fincly er*fted wqd{:*n bsx oc}a *helf in the inch-long floxibls rube with En inwmal diameter 'IYLM mrc book rcom.It cnn:e t**llsntion sf $/8 af tn inoh, a wsodcn T-pierx connector again when Dr. f,rsrth &u*[pg sfuolltcd the WLht and a glass rnoutlrpiec*. Wirhout deliberate Trust*es somc valuable books that h*d bfen thought, I reflexively te*t*d rny ncwly as-

*? - Txx Tkrno trxrEnr*nos,u" Sy?i$r}*i!*r tr${ ?*rs **txxt *r Axerrxffita sembled circuit by placing the mouthpiece Faulconer and Keys expressed the opinion that against my lips and inhaling. To my chagrin, I Wood's complete apparatus was manufactured immediately drew the dust of decades deep into by Ferguson.3 The WLM inhaler was produced my lungs provoking a violent cough. As the by a leading British manufacturer of the period, exhaled dust flew from the distal arm of the T- but the identity of its designer remained a piece, I heard the lick of a valve closing, a mystery. sound which excited greater curiosity. I disas- This problem resolved unexpectedly when sembled the T-piece and found that it contained Dr. Samuel Tirer sent me a manuscript to two wooden spheres of 5/8-inch in diameter review along with photocopies of pages from positioned as caged inspiratory and expiratory the Lancet of 1847. Fortuitously, even though it valves. Until that moment I had not appneciated was not the topic of his research, my friend that valves very similar in concept to the non- included an illustration which riveted my rebreathing valves of mid-2OOth-century attention because it depicted an inhaler almost construction had been used many decades identical to that in the WLM collection. The earlier. accompanying text reported the January 23, As I continued my examination, I was 1847, meeting of the Westminster Medical caught up in admiration for the utility of the Society. The first sentence began, "Dr. Snow vaporizer's design and searched for any placed on the table an apparatus for the inhaling information that would identify its gifted of the vapour of ether.a The WLM Trustees designer. The wooden box was unlabeled, but a were soon delighted to leam that the vaporizer, small brass plate on the vaporizer read: which had rested in obscurity in our museum, "Ferguson was a product of John Snow's genius! 221, Giltspur Street" Tlte Inncet diagram included details of The WLM librarian, Patrick Sim, and I the vaporizer's construction. Although the were unable to find a reference to Ferguson in device Snow demonstrated in January 1847 K. Bryn Thomas' "The Development of lacked the quadrant valve to permit the mixing Anaesthetic Apparatus" or other British and of ether with room air, it was otherwise very American historical texts. We did, however, similar to the WLM vaporizer. The article find Ferguson of Giltspur Street, London, included a schematic internal view which among the manufacturers listed in a copy of revealed a spiral plate within the vaporizing Elisabeth Bennion' s catalog, "Antique Medical chamber similar to that shown in Snow's Instruments," but did not find a vaporizer monograph. The accompanying description among her illustrations of Ferguson's equip- revealed Snow's awareness of the advantages ment. From Bennion's history of the Ferguson provided by the water bath. He stated: company, we were able to derive the period of When used, the inhaler was to be put its manufacture as follows: Ferguson had in a hand-basin of water, mixed to a relocated to Giltspur Street in 1828; the firm's particulu temperature, conesponding to the propofiion of vapour name changed to Ferguson & Son in 1851; that the operator might desire to give; and the caps being therefore, our vaporizer must have been removed, and the mouth-tube attached, manufactured before l85l and after December when the patient began to inhale, the air 1846 when the news of ether anesthesia crossed would gain the desired temperature in the Atlantic to Britain. passing though the metal pipe; it would Some time later I unexpectedly found an then come upon the surface of the ether, appreciation of Ferguson's work when re.ading where it would have to wind round three or the papers of Dr. Alexander Wood, the four times before entering the tube going to Edinburgh pioneer of subcutaneous injection. the mouth-piece, thus ensuring its full Wood incorporated into his ingenious develop- saturation, and preserving it at the desired ment of the syringe and hollow needle.2 In 1965 temperature. There was no valve, or any

93 -Roo K. CelvmI"ev other obstruction to the air, till it reached vaporizer was the second prototype of the well- the mouth-piece, which was of the kind known Snow ether vaporizer which we find used in other inhalers, and contained the illustrated within its rectangular metal water prevent valves necessary to ttre return of the bath.I could now follow the evolution of his expired air into the apparatus.r vaporizer from is original version as illustrated A rcview of theLondonMedical Gazette of in January, 1847 inlancet through the interme- 1847 revealed an article of March 19, 1847 in diary modification in the WLM collection and which Snow described a vaporizer which then to its final form in the Snow September featured a quadrant valve that had been de- lM7 monograph. The text of the monograph signed for Snow by Ferguson to permit the served as a guide to the factors which had introduction of air without the requirement of motivated Snow's responses to deficierrcies in removing the mouthpiece.6 This was the WLM his early vaporizers. The most striking of these vaporizer (Figure 2). Two weeks later on April were the addition of the metal waterbath to 3, L847, Snow described a portable ether house the vaporizer and the substitution ofa vaporizer for which no illustration was pro- face mask incorporating inspiratory and vided.T The final version was the model expiratory flap valves for the mouthpiece. incorporating the rcctangular metal tin described Snow explained his motivation for design- in the monograph. I have recently leamed that ing a malleable facemask as follows: Dr. Richard Ellis has catalogued Snow's ether "For the frst threc months I used a - vaporizers chronologically as Mark I Ianuary mouth-piece which did not include the 23, Mark II - March 19, Mark Itr - April 3, nostrils; consequently they had to be Mark IV - September, 1847.t The WLM is, in closed, and the patient was obliged to Dr. Ellis' classification, a Mark II device. breathe entirely by the mouth. This plan At the first opportunity, I compared the always suiceeded (except, perhaps, in one WLM vaporizer with the text and illustrations of instance), and generally very well, but Snow's September 1847 monograph. The WLM sometimes not without difficulty; for some

Fig. 2. Snow's Modified Ether Vaporizer (as illusrated in the London Medical Gazene p 501, March 19, 1847).

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94 - THE THRD INTSRNATIoNAI SYMFosluM ox nre HpronY or AnBsnresrr of the adult patients, after they lost their then vary enatically with the potential of an consciousness, made such strong instinctive even greater hazard liquid ether flowing efforts to breathe by the nostrils, that the air along the breathing tube- to the patient. Snow not was forced through the lachrymal ducts, only pioneered the use of water bath to ensure and occasionally they held the breath that the anesthetic vaporpressure was constant altogether for a short time, and were getting but, by fixing the vaporizer in a horizontal purple in the face, when the nosrils had to be liberated, for a short time, to allow position, also overcame the risk of erratic respiration of the extemal ur, and thus a variations in anesthetic concentration precipi- delay was occasioned. I was therefore ready tated by movement of the vaporizer. to adopt a face-piece invented by Mr. The monograph also provided a point of Sibson, of the General Hospital, information which may explain why the WLM's Nottingham, which permitted inhalation by unused vaporizer may be the only existing the nostrils as well as by the mouth. This representative of its type. snow commented, face-piece. . . was the foundation of that I "This part of the apparatus (the vaporizer) was now use, which has been altered. . . to at made tinned iron, it was allow of the introduction of valves into first of but found it.. .'a occasionally to beeome rusty by use."r2 Be- Snow explained his preference for the low cause even the better grades of ether available in resistance flap valves over the brass quadrant 1847 were contaminated by water, it is probable . valve of the WLM model by stating: that every Snow vaporizer put in service to "[ have conEived the expiratory valve deliver anesthetics was destroyed by corrosion. to tum on a pivot, so as to allow of the Our WLM model may have survived only admission of extemal air, and to supersede because it had never been used for anesthesia. the use of a femrle or two-way tap. . . Snow also described the origins ofthe graduated '$l/hen a stop-cock with openings components of the vaporizer. In January I 847 is used. . air passes through the . the he had commented only that, "In the interior (of external opening in preference to the more tire inhaler) was a spiral plate of tin, soldered to circuitous route over the ether; and when the top, and reaching almost to touch the the respiration is gentle, the whole of the air the patient breathes may enter by an bottom. . . When the patient began to inhale, the outward opening that would only admit a air. . . would have to wind round three or four third part of what he inspires when the times before entering the tube going to the respiration is forcible."ro mouth-piece, thus insuring full saturation (with In a remarkably short time Snow had achieved ether vapor)."r3 In September he reported in the several very practical improvements. monograph that, "This spiral arrangement is Snow stated that the rectangular metal box adopted from the inhaler of Mr. Julius Jeffrcys was added to serve ". . .as a waterbath when the for aquerous vapour."la Because no footnote or apparatus is in use, and at other times containing reference was provided, a new element was the elastic tube and face-pieces."rt I performed added to the mystery. Who was Jeffreys? a simulated trial which revealed another Snow's acknowledgment did make clear, important, but unstated, advantage of the however, that the spiral plate was not of his own covered rectangular water bath; the lid held the design. vaporizer in a stable position. My test showed that earlier models, designed to float The Jeffreys Inhaler unrestrained in a basin of water, could tip I learned no more about Jeffreys until I unexpectedly if the patient should turn his head studied medical joumals of 1840-1850 in or the anesthetist shift position. A tug along the Britain. The first entry that caught my eye was a flexible tube might overtum the vaporizer which February 1847 illusration of aJeffreys inhaler brought the risk of liquid anesthetic entering the with an unsigned commentary posing the tube. The concentration of anesthetic would question: "By a reinarkable coincidence we find

95 -Roo K. Cr-vnueY that an instrument identical in principle with trave$e the short distance across the radius of that invented by Dr. Snow, was invented some the vessel but was channeled a longer distance years ago by Mr. Jeffrey (sic) as an inhaler. The to become fully humidified. This concept was circumstance reminds us of the case of the new incorporated later by Snow.rs planet, in which two rival discoverers are in the Although it may appear that Jeffreys' field."r5 (Neptune was first obsewed on device represents only an eccentricity of September 23,1846 in a position which had Victorian medicine, a well-researched biogra- been independently predicted by two mathema- phy of Julius Jeffreys by Dr. David Zuck ticians, John Adams and Urbain Le Venier.) presents a different perspective. Dr. Zuck Although we do not know who challenged recognized that Jeffreys' concept of Snow for failing to credit Jeffreys' prior humidification had a modem application. preparation of a coiled inhaler, an earlier entry Jeffreys marketed a portable humidifier which in the literature revealed that Snow had previ- he called a "Respirator," a term which Dr. Zuck ously recognized Jeffreys' claim. Any contem- points out that the Eclitors of the Oxford porary accusation that Snow plagiarized was Dictionary conclude was coined by Jeffreys. refuted by Snow's first commentary on anaes- Jeffreys' "Respirator" consisted of a plate of thesia in which he identified his inhaler as being finely soldered metal grids which formed a modeled on Jeffreys'. The Inndon Medical latticework within a frame that could be wom Gazette recorded the meeting of the over the lower face in cold weather. Dr. Zuck Westminster Medical Society of January 16, described its function as follows: "During 1847, asession held seven days before Snow exhalation warmth would pass from the breath demonstrated his first vaporizer. The secretary to the lattices, and moisture would condense on reported: "He (Snow) was getting an instrument them. During inspiration the cold air would be made which would enable the surgeon. . . to warmed, and humidified."re A patient's administer an atmosphere (of ether) of any testimonial read that the "Respirator" had the strength he wished. . . The instrument. . . was on property of making all the air that goes down the plan of the inhaler of Mr. Jeffreys, with one's throat as wann as summer air. Jeffrreys some alterations and additions."r6 Atthe first patented the "Respirator" and gained royalties opportunity Snow had acknowledged Jeffreys' from the sale of several thousand. Dr. Zuck was invention. the first to realize that Jeffreys had prepared a Who was leffreys? A review of the London humidifier identical in principle to the heat and Medical Gazette led to a multi-part article, "On moisture exchanger (HME) of Swedish design artificial climates and the r€storation and now often positioned between the endotracheal preservation of health," published in 1842 by tube connector and the Wye-piece of an Mr. Julius Jeffreys ( I 801- I 877).r? Jeffreys' anesthesia circuit. thesis was that, based on his personal experience as a surgeon in India, the humidification and Read's Valves warming of air was of advantage both in the While I now understood the history of the treatment of respiratory disease and in the vaporizer, the origin of the non-rebreathing prevention in cold climates of losses of heat and valves remained a mystery. Snow's phrasing moisture in the exhaled breath. Jeffreys reported that the valves were of the sort "in ordinary use" that the motivation for his invention came from suggested that he had not invented them, but a concem for his sister who was debilitated by other questions remained: When had they been pamxysms of severe coughing. He crcated an first designed and for what purpose? Had Snow instnrment that would warm and humidify the been the first to use the valves in an anesthetic air she inhaled. The Jeffreys inhaler contained circuit? No one with whom I corresponded an internal coil positioned so that, as the patient could answer the questions, but visits to British inhaled, the inspired air could not simply museums brought progress.

96 -Tnr THno lrrrennmor'llr- SYMposruM ox rxe Hsronv or Ar*esrHEstr The rich collections of l9th-century also selected Read's valve. medical devices in the Science Museums in On January 13,1847,23 days after Squire's Oxford and London featured two ether vaporiz- first public anesthetic and only a few days ers, both of which antedated Snow's first before Snow's first vaporizer was marketed, the inhaler. The Science Museum in Oxford had a Pharmaceutical Society of London held an reconstruction of Peter Squire's inhaler, which extraordinary meeting in which models of seven had been employed by his nephew, William, for ether inhalers were displayed by their inventors. the first public demonstration of ether in Five of these featured Read's valves. Mr. Squire England on December2l,1846, when Sir was joined by Messers. Hooper, Clendon, Bell, Robert Liston amputated a coachman's leg. and Gilbertson, all of whom shared in a spirited Squire's inhaler featured a non-rebreathing debate over the merit of their devices. The valve, one closely resembling the valve of Society's secretary noted, "Some discussion Snow's vaporizer. The Science Museum in arose about priority of invention, caveats, London had an original Tracy's inhaler. It was patents, registration, etc. which the Chairman an impractical design, having a narrow and very properly cut short, as being foreign to the elongated glass vaporizing chamber shaped like objects of the meeting.'a Read's valves had the bowl of a large Meerschaum pipe, but Tracy such utility that they had been chosen by five of had precluded rebreathing by incorporating Britain's first anesthetists at least seven days valves of the same type. Since the valve design before Snow's first inhaler was marketed. used by Snow had also been selected by Squire For some time my search was handicapped and Tracy, it was certainly "in ordinary use," by too narrow a focus of interest. Because I had but who had used it first? learned of Read's valve through its medical The published descriptions ofthe vaporiz- application in inhalers,I attempted to find ers on display in Oxford and London gave more references to Read by searching among articles information. In a letter written January 18, 1947, published by physicians of the period to identify for the London Medical Gazette, S. J. Tracy of the disease or diseases which a Doctor Read St. Bartholomew's Hospital reported that his might have attempted to remedy by crcating a Tracy inhaler had been prepared by Mr. non-rebreath ing valve for inhalation therapy. Ferguson of Giltspur Street, soon to be Snow's The search remained unsuccessful even when manufacturer also, and that, by the date of the British friends extended it to include altemate letter, Tracy had already administered 20 spellings of Read. Fortunately, I directed a anesthetics with it. He referred to the non- request to Dr. Ghislaine Lawrence, the Assistant rebreathing mechanism as a "double-valved Keeper of the Science Museum in Iondon, who mouthpiece of the description in ordinary use.'40 initiated a broader search of the technical While two of Ferguson's clients, Tracy and literature. To my good fortune, her associates Snow, failed to identify the designer of the came upon a remarkable document - Read's valves, a witness's account of Squire's first use patent. The patent (#4454) was awarded on July of an inhaler on December 27, 1846, brought the 11, 1820, to a Mr. John Read (1761-1847) for answer. The reporter of the London Medical "An Improvement in Syringes." The accompa- Gazelte commented, "It (Squire's inhaler) nying diagram showed that spherical valves consisted of a Nooth's Apparatus. . . and one of within the chamber of a syringe provided Read's flexible inhaling tubes. . .'4r Once unidirectional flow which permined the syringe again, I had leamed a name, Read, but knew to be used as a pump. Read prepared pamphlets nothing of the original purpose or history of the to describe the sizes of his valved syringes and invention. Certainly, Read's valve must have their applications in activities which ranged been in regular,use because it had been chosen from horticulture (spraying fruit trees) through not only by Snow and Tracy but also by Squire. veterinary medicine (medicating horses and I was soon to leam that other anaesthetists had cattle) to clinical practice (pumping the stomach

97 - Roo K. CrLvERt-EY or applying an enema). The anesthetiss of 1847 papers suggested a cordial interactions between had certainly been correct in describing Read's the two men and, on Snow's part, a respect for valves as being "in ordinary use." Mr. Read, who at 80 years of age, was still I searched the medical literature for actively designing equipment. In December, references to Read's valves and found three. l84l Snow readapaper, "Onparacentesis of The first was written by a distinguished London the thorax" to the Westminster Medical Society, surgeon, Sir Astley Cooper. The latter two were in which he discussed the risk of the uncon- citations by a then little-known but now highly rolled entry of air into the pleural space via a regarded physician of Soho, John Snow. canula during paracentesis. To reduce this My literature search had begun with the hazard, Snow added a stopcock to the canula. first volume of Lancet when the journal was He remarked that the canula he had designed first published in 1823. Fortuitously, Reid's was one which "any membercan get made by (sic) syringe was cited in the Index. The his own instrument maker'l and added "It has relevant account described an experiment since been manufactured" under my dircctions, wittr supervised by Sir Astley Cooper on Friday, great accuracy, by Mr. Read of Regent Circus.'% Novernber 21,1823 in the operating theater of The inffoduction of the stopcock was the Guy's Hospital. That aftemoon, opium in water second collaboration on instrument design had been poured down the throat of a restrained recorded between Snow and Read. The first dog. After an interval of 33 minutes, when the occurred earlier the same year. On October 16, animal showed effects of the narcotic, the 1841, precisely five years beforc Morton stomach was evacuated by Read's pump demonstrated ether's anesthetic action, Snow syringe. The reporter continued, "The instru- read a paper before the Westminster Medical ment succeeded very well in the dog, which Society, "On asphyxia, and on the resuscitation appeared to be little worse for the experiment. of still-born children." In that paper, which may Mr. Reed (sic) was in the theatre during the be Snow's first work relevant to anesthesiology, whole of the time, and superintended the use of Snow recommended thrce actions now consid- the instrument; on quitting he received the ered fundamental elements of resuscitation. unanimous applause of those present.'4 These actions were: using supplemental oxygen, While lecturing at St. Thomas's Hospital suctioning the airway and performing mechani- the following Wednesday, Cooper lauded Read cal ventilation. Snow related that in 1838 John by stating:'This experiment, Gentlemen, Read had prepared a syringe to ventilate adults. delighted me; I do not know that I have ever Quoting Snow, "So the matter rested, until a axperienced greater pleasure in my life than I short time ago, when Mr. Read, knowing I took felt in going home from the Hospital on that an interest in the subject, called to show me an day. With respect to antidotes against the effects improvement in his apparatus. . . . Ithen of poison, it is well known that they are, in a suggested that he should make a little instru- great degree, useless. . . . A few weeks ago, a ment on exactly the same plan, adapted to the nurse in this Hospitai died in consequence of size of new-born children. It consists of two having swallowed opium. No relief was syringes, one of which, by a tube adapted to the administered to her; but can it be said, after mouth, and closing it, withdraws air from the what we saw on Friday; that no rclief could lungs, and the other syringe returns the same have been administered to her?'a Soon quantity of frcsh air through a tube fitted to the thereafter, Read's priority to the invention was nostrils."26 Read's valves were essential to the challenged, but his claim prevailed. action of the syringes. Five years later Snow While John Read's stomach pump was a again selected Read's valves for his ether significant contribution to the general practice vaporizers and, in so doing, designed the first of of medicine, two other applications of his a series of vaporizers that were the most equipment were reported by John Snow. Both functional of that historical period.

98 - Tne Txno breweuoxrt Svtilpostutrl oN rne Fltstonv or Amsrspsrr The single surviving Snow vaporizpr will incorporated by John Snow in his fint ether be on public display in the new Wood Library- vaporizers. Museum of Anesthesiology. All anesthesiolo- gists who view it as it lies shielded behind walls Acknowledgements of glass will be impressed by its attractive and I wish to express my appreciation to Mr. functional design. For me it has been more than Patrick Sim, Librarian of the Wood Library- a museum-piece, it has been as magical as Museum, Park Ridge, Illinois. Many British Aladdin's lamp for it has led me on a study of historians, particularly Dr. Barbara Duncum, Dr. the technology employed in the era in which Richard Ellis and the late J. Alfred I-ee gave anesthesia was discovered. By touching the invaluable advice. Dr. Ghislaine Lawrence and vaporizer I have been led to a new appreciation hercolleagues at the Science Museurn, London of the skills of John Snow. When I first as- provided generous assistance. I wish to thank sembled and breathed through the inhaler,I the Buroughs Wellcome Fund for the financial could not have anticipated that my dust-driven support provided by a Wellcome Research cough would provoke a study of the components Travel Grant.

References 14. Snow J: On the inhalation of the vapour of ether. p 19. l. Snow, J: On the inhalation of the vapour of 15. Anonymous: Apparatus for inhaling ether. ether, p 20, London, J. Churchill, 1847. Medical Times February 20,1847. Wood A: New method of treating neuralgia by 16. Anonymous: Wesuninstsr Medical Society: the direct application of opiates to the painful report of a meeting of January 1 6, 1 847. Lond points. Edinburgh Medical and Surgical J: Med Gaz: 39: 156. 82:?55,1855. t7. Jeffreys J: On artificial climates for the restora- Faulconer A. Keys, TE: Foundations of tion and preservation of health. Lond Med Gaz: anesthesiology, p 1022. Springfield, Illinois, 29:814-22 et seq. Charles C. Thomas, 1965. 18. Jeffrcys J: On artificial climates forthe restora- 4. Anonymous: Westminster Medical Society: tion and preservation of health, Lond Med Gaz: report ofmeeting on 23 January 1847. Lancet p 821. i:12U21,1847. 19. Zuck D: Julius Jeffreys - pioneer of humidifica- 5. Anonymous: Lancet i:121, 1847 . tion. Proceedings of the History of Anaesthesia 6. Snow J: On the inhalation of the vapour of ether. Sociery. London 8b:70-80, 1990. Lond Med Gaz: 39: 498-502, 1847. 20. Tracy J: Apparatus for the respiration of ether 7. Anonymous: Westrninster Medical Society: vapour. Lond Med Gaz:. 39: 167, 1847 . report of meeting on April 3, 1847, Lond Med 2t. Anonymous: Lond Med Gaz:39: 38. Gaz:39: 64647,1847. i1 Anonymous: Tlansactions of the pharmaceutical 8. Ellis RH: The inhalers of Dr. John Snow: his society meeting of Wednesday, January 13, marks and his scorc. Proceedings of the History lM7. Pharm J 6:353,1847. ofAnaesthesia Society, I-ondon. 8b: 81, 1990. 23. Anonymous: Guy's Hospital Report, Lancet i: 9. Snow J: On the inhalation of the vapour of ether. n5-277,1823. P22. a. Cooper A: Surgical Lecrurc November 26, 1823. 10. Snow J: On the inhalation of the vapour of ether. Lancet i:299,7823. p23. 25. Snow J: On paracentesis of the thorax. Lond 11. Snow J: On the inhalation of the vapour of ether. Med Gaz: 29:7UI ,1842. p 16. 26. Snow J: On asphyxia, and on the resuscitation of 12. Snow J: On thc inhalation of the vapour of ether. still-born children. Lond Med Gaz:29:2?5, p 20. 1841. 13. Anonymous: Lancet i: l2l, 1847,

99 - Roo K. CetvgRuEY