THE ADMINISTRATION OF 
 
 NITROUS OXIDE & OXYGEN 
 
 FOR DENTAL OPERATIONS. 
 
 Frederic W. Hewitt, 
 
 M.D.
 
 THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 
 OF CALIFORNIA 
 
 LOS ANGELES 
 
 "'■ HENRY KIMPTON, 
 Medical Bookseller & Publisher/ 
 261 Hif»h Holborn London W.fT.r
 
 r ^u^ ^ < 

 
 THE 
 
 ADMINISTRATION OF NITROUS OXIDE 
 
 AND 
 
 OXYGEN FOR DENTAL OPERATIONS.
 
 THE ADMINISTRATION OF 
 
 Nitrous Oxide and Oxygen 
 
 DENTAL OPERATIONS 
 
 FREDERIC W. HEWITT, M.A., M.D. Cantab. 
 
 Anasthetist at the London Hospital, Charing Cross Hospital, the Dental 
 Hospital of London, and the A T ational Orthopiedic Hospital 
 
 Xon&on 
 
 CLAUDIUS ASH cV SONS, Limited 
 5, 6, 7, 8 and 9, BROAD STREET, C.OLDEN SQUARE 
 
 I'HILADKI.NIIA 
 
 THE S. S. WHITE DENTAL MANUFACTURING CO. 
 Chestxut Street, Corner Twelfth
 
 / 
 
 TO 
 THOSE OF THE PAST AND PRESENT 
 
 SURGEONS AND ASSISTANT SURGEONS 
 
 OF THE 
 
 DENTAL HOSPITAL OF LONDON 
 
 WITH WHOM I HAVE BEEN ASSOCIATED WHILST MAKING 
 
 THE OBSERVATIONS HEREIN CONTAINED, 
 
 I VENTURE TO 
 
 DEDICATE 
 
 I HIS LITTLE BOOK, 
 
 IN GRATEFUL RECOGNITION OF THE PATIENCE AND COURTES\ 
 
 WHICH IHi:\ HAVE INVARIABLY DISPLAYED DURING 
 
 THE PROGRESS OF THE INVESTIGATION.
 
 PRE FACE. 
 
 Eleven years have elapsed since I commenced 
 working at this subject. The first eight years 
 were mainly devoted to conducting prelimin- 
 ary experimental administrations of various 
 mixtures of nitrous oxide and oxygen, and to 
 devising and perfecting apparatus. The last 
 three years have been occupied in ascer- 
 taining the precise influences exerted by this 
 or that percentage of air or of oxygen upon 
 the usual asphyxia! phenomena of pure nitrous 
 oxide. 
 
 My original intention was to incorporate in 
 one volume the results of both parts of the 
 research, but I have since decided to adopt 
 a different course, and to first place in the 
 hands of the medical and dental professions 
 this small treatise dealing more particularly 
 with the practical aspects of the subject, and 
 subsequently to bring forward the large mass 
 of evidence which I now possess concerning
 
 viii. Preface. 
 
 the physiological effects of different mixtures 
 of nitrous oxide with air or oxygen. 
 
 Safe and thoroughly, efficient anaesthesia 
 for dental operations is of such importance 
 that it behoves every dental practitioner to 
 carefully consider whether he should not 
 abandon the prevalent but comparatively 
 crude and unscientific method of producing 
 insensibility from nitrous oxide, and avail 
 himself of the new system. 
 
 It is true that there are at present some 
 difficulties in the way of this advance, but it 
 is to be hoped that they may soon be sur- 
 mounted. The principal of these undoubtedly 
 is the difficulty of obtaining proficient anaes- 
 thetists. Increased facilities, however, are 
 now being afforded at most hospitals for 
 acquiring experience in administering anaes- 
 thetics, so that there is every reason to believe 
 that, in course of time, there will not be that 
 dearth, which now exists, of medical men 
 capable of administering nitrous oxide in 
 dental practice. 
 
 Moreover, I hope to see the da)" when the 
 immense amount of clinical material which is 
 now being wasted, so to speak, at our dental 
 hospitals, will be utilised, not only for the 
 systematic instruction of dental students who 
 are intending to qualify in medicine, but tor 
 that of extraneous students and practitioners.
 
 Preface. ix. 
 
 In this way it would be possible to efficiently 
 train medical men in dental anaesthetics, and 
 to keep the dental profession supplied, as it 
 were, with proficient anaesthetists throughout 
 the country. 
 
 FREDERIC \Y. HEWITT. 
 
 10, George Street, 
 
 Hanover Square, W. 
 May, 1897.
 
 CONTENTS. 
 
 I' AGE 
 
 Chapter I. — Introduction ... ... ... i 
 
 Early History of nitrous oxide ; its discovery 
 by Priestley ; recognition of its anaesthetic 
 properties by Davy ... ... ... ... i 
 
 Colton's lectures ; Horace Wells the first to 
 inhale nitrous oxide for a surgical opera- 
 tion ; " Laughing Gas" ... ... ... 2 
 
 Early administrations of nitrous oxide ; Air 
 mixed with the nitrous oxide ; Symptoms 
 due to this admixture ; Smith's and Colton's 
 administrations ... ... ... ... 4 
 
 Rymer's administrations; Evans's Demonstra- 
 tion ; Clover's improvements ... ... 5 
 
 Nitrous Oxide now administered free from all 
 air ; Asphyxial phenomena ; only suitable 
 for brief operations ... ... ... . . 6 
 
 Paul Bert's researches ; his attempts to obtain 
 anaesthetic effects without asphyxial mani- 
 festations, by using nitrous oxide and air, 
 under increased barometric pressure ... 7 
 
 Oxygen used instead of air ; Bert's experiments 
 
 continued ... ... ... ... ... 8 
 
 Bert's method applied to practice ; the 
 phenomena observed ... .. ... ... 9 
 
 Khkowitsch's, Winckel's, Doderlein's, and 
 
 Zweifel's administrations ... ... ... 10 
 
 Martin (of Lyons land his trial of Perl's method 1 r
 
 xii. Contents. 
 
 I' AGE 
 
 Bert's attempts to obtain good effects without 
 employing increased pressure ... ... 12 
 
 Hillischer's work ; " Schlafgas " ; 15,000 
 administrations ; his regulating apparatus 13 
 
 Witzel's administrations ; Wood's conclusions 14 
 
 The Author's work ; Early administrations ; 
 
 13 forms of apparatus devised ... ... 15 
 
 Sudden transitions in composition of mixture 
 not desirable ; Experiments with different 
 percentages of oxygen ... ... ... 16 
 
 Necessity of absolutely excluding air : the 
 effect of administering the gases from a dis- 
 tended bag ... ... ... ... ... 17 
 
 10 per cent, of oxygen found to be preferable 
 to 1 2.7 per cent. : but no definite percentage 
 answered in all cases... ... ... ... 18 
 
 Difficulties in obtaining a suitable apparatus ; 
 objections to Hillischer's apparatus; a 
 satisfactory apparatus eventually devised ... 18 
 
 Chapter II. — Apparatus ... ... ... ... 21 
 
 1. Gasometer methods ; the best percentages 
 
 of oxygen ... ... ... ... ... 21 
 
 Keeping the two gases together before use 22 
 
 2. The Author's Regulating Apparatus ; 
 Requirements that must be fulfilled by a 
 regulating apparatus ... ... ... ... 23 
 
 Cylinders for the two gases ; combined stand 
 
 and union ... ... ... ... ... 26 
 
 Tubes for transmitting gases from cylinders 
 to bags ... ... ... ... ... 28 
 
 Regulating Stopcock and Mixing Chamber ; 
 its various parts ; its flange with figures ; 
 its oxygen inlets ... ... .. ... 29 
 
 Its valves . . ... ... ... ... 31 
 
 Eace-pieces ... ... ... ... ... 32 
 
 Necessity for carefully handling and examin- 
 ing the apparatus ; the relative proportions 
 of the two gases passing through the 
 apparatus ^3
 
 Contents. xiii. 
 
 I' AGE 
 
 Slight differences in action in different 
 
 models; Makers of the apparatus ... 34 
 
 Chapter III. — Preparations ... ... ... $5 
 
 Precauticns as to diet ... ... ... ... 35 
 
 Stimulants ... ... ... ... ... 36 
 
 Everything should be in readiness before 
 patient enters room ; Appliances which 
 
 should be at hand in case of emergency 36 
 
 Necessity for the presence of a third person 37 
 
 Importance of loose clothing ... .. ... 37 
 
 Influence of posture ; Use of inflated air- 
 cushion ... ... ... ... ... 38 
 
 Mouth-props and their insertion ; Treatment 
 of retching movements excited by inserting 
 
 mouth-prop ... ... ... ... ... 40 
 
 Chapter IV. — The Administration ... . . 42 
 
 All disturbing influences to be avoided ... 42 
 
 Application of face-piece ... ,. ... 43 
 How the patient should breathe ; Air first of 
 
 all inhaled through the apparatus ... ... 44 
 
 Then a small percentage of oxygen ... ... 45 
 
 Initial sensations ... ... ... ... 46 
 
 The fitting of the face-piece ... . 46 
 
 The fulness and relative sizes of the bags ... 47 
 
 The admission of oxygen ... ... ... 4S 
 
 Proper adjustment of the proportions; too 
 
 much oxygen; too little oxygen ... ... 50 
 
 Characteristics of nitrous oxide and oxygen 
 
 anaesthesia ... ... ... ... ... 51 
 
 Signs of the anaesthesia... ... ... ... 52 
 
 il Inspiratory calm "... ... ... 52 
 
 The pulse and circulation ... .. ... 52 
 
 The eyes and eyelids ... ... .., ... 53 
 
 The delayed effects of admitting more or less 
 
 oxygen 54 
 
 The length of inhalation ... ... ... 54 
 
 Quantity of mixture required ... ... ... 55
 
 Contents. 
 
 Chapter V. — The Patient 
 
 Different types of patients 
 
 Influence of Sex and Age 
 
 General condition of patient 
 
 Physique ... 
 
 The presence of a Beard or Moustache 
 
 Temperament 
 
 Complexion; Colour 
 
 Alcoholic indulgence 
 
 The excessive use of Tobacco and other Nar 
 
 cotics 
 Affections of the Respiratory System... 
 Affections of the Circulatory System ... 
 Affections of the Nervous System 
 Pregnancy 
 
 56 
 
 56 
 57 
 58 
 
 59 
 60 
 60 
 62 
 63 
 
 64 
 64 
 
 65 
 67 
 68 
 
 Chapter VI.— The Ax.esthesia ... ... ... 69 
 
 The Available Anaesthesia for a Dental 
 
 Operation ... . . ... . . 69 
 
 The duties of the Anaesthetist during the 
 
 Operation . . ... ... ... ... 70 
 
 Duration of the Available Anaesthesia ... 70 
 
 State of the Patient during the Operation ... 72 
 
 Reflex movement ; Phonation... ... ... 72 
 
 Termination of the Anaesthesia ... ... 73 
 
 Re-administrations; Difficult Operations ... 74 
 Drilling into Pulp-cavities ; Opening up the 
 
 antrum ... .. ... ... ... ... 75 
 
 Chapter VII. — Exceptioxal Cases ... ... 76 
 
 Laughter ; Singing; Shouting; Phonation ... 76 
 Muscular Phenomena during Inhalation ; 
 Strictly voluntary movements; Uncontrol- 
 lable nervous movements ; Intoxication 
 
 movements; Tonic Spasm ... ... ... 77 
 
 Clonic Spasm; '•Jactitation''; Pine Tremor 78 
 
 Tonic movements of Deep Anaesthesia ... 79 
 
 Cyanosis ... ... ... ... ... ... 79
 
 Contents. xv. 
 
 L'AGE 
 
 Shallow, imperceptible, or arrested Breathing, 
 
 with good pulse and colour ... ... ... bo 
 
 Violent Respiration ... ... ... ... 80 
 
 Coughing; Crying ... ... ... ... £1 
 
 Retching and Vomiting during Inhalation ... 81 
 
 Dangerous Symptoms ... ... ... ... 81 
 
 Highly Exceptional Cases ... ... ... 82 
 
 Chapter VIII. — After-Effects ... ... 84 
 
 Important to regulate Diet ... ... ... 84 
 
 Recovery usually very satisfactory : often 
 
 better than after nitrous oxide per sc ... 84 
 
 Protracted Inhalations liable to be followed by 
 
 Giddiness, Torpor. Headache, &c. ... ... 85 
 
 Nausea. Retching, and Vomiting ... ... 86 
 
 Pallor, Faintness, and Feebleness of Pulse 87 
 
 Treatment of After-effects ... ... ... 87 
 
 Hysteria ; Temporary Maniacal Seizures : 
 
 Cataleptic States 88 
 
 Dreams ... ... ... ... ... ... 88 
 
 Bibliography 
 
 89
 
 LIST OF ILLUSTRATIONS. 
 
 i'.u;i; 
 
 Fig. i. The Author's Apparatus ... ... 24 
 
 ,, 2. Diagrammatic Section of Cylinders 
 
 and of Combined Stand and Union 26 
 
 3. Diagrammatic Section of rhe India- 
 rubber Transmitting Tubes and 
 Bags 27 
 
 .. 4. Regulating Stopcock and Mixing 
 
 Chamber 29 
 
 ,, 5. The Administration ... ... ... 44
 
 THE ADMINISTRATION OF 
 
 NITROUS OXIDE AND OXYGEN 
 
 FOR 
 
 DENTAL OPERATIONS. 
 
 CHAPTER I. 
 INTRODUCTION. 
 
 In reviewing the past history of nitrous 
 oxide as an anaesthetic one cannot help being 
 struck by the singular vicissitudes which this 
 agent has experienced. That a quarter of a 
 century should have passed between its dis- 
 covery by Priestley and the recognition of its 
 pain-relieving properties by Davy is sufficiently 
 remarkable. But more curious still is the fact 
 that nearly double this length of time elapsed 
 between Davy's observations and the first ad- 
 ministration of the gas for a surgical operation. 
 It was during this latter interval that nitrons 
 oxide received the name of "laughing gas" 
 from the power it possessed, when small quan- 
 i
 
 2 Introduction. 
 
 titles were breathed backwards and forwards, 
 of producing hilarious excitement. 
 
 In December, 1844, Dr. Colton, " an 
 
 itinerant lecturer on chemistry " (to use a 
 description given of him by one of his own 
 countrymen),' demonstrated these effects at 
 Hartford, Conn., U.S.A. At this entertain- 
 ment Horace Wells, a dentist, was present, 
 and noticing that one of the audience who had 
 inhaled the gas had unconsciously bruised him- 
 self whilst under its influence, he shrewdly sus- 
 pected that the so-called ''laughing gas" might 
 prove to be of valuable service in dentistry. 
 This brilliant idea was quickly put to the test : 
 Colton administered the gas to Wells : and a 
 friend of the latter extracted a tooth during 
 the anaesthesia thus produced. This adminis- 
 tration of nitrous oxide, although conducted 
 in the crudest manner, will ever deservedly 
 remain a memorable one ; for it laid the 
 foundation stone, so to speak, of our present 
 system of surgical anaesthesia. 
 
 The realisation of the hopes which Wells had 
 entertained was so complete that he naturally 
 enough looked forward to an uninterrupted 
 and glorious reign for the new anaesthetic 
 whose services in surgery he had been the first 
 to requisition. His first public demonstration, 
 however, unfortunately proved a fiasco ; and 
 this circumstance, coupled with the fact that
 
 Introduction. 3 
 
 intense interest soon became universally felt 
 at the discovery, by Morton, of the anaesthetic 
 properties of ether, rapidly placed nitrous oxide 
 again upon the shelf, where it remained, more 
 or less forgotten, for a further term of nearly 
 twenty years. A little reflection will at once 
 show that Wells's anaesthetic was heavily handi- 
 capped in its struggle for existence. Its phy- 
 sical characters were against it. Being gaseous 
 at ordinary temperatures and pressures, it was, 
 as compared to its liquid rivals, ether and 
 chloroform, more or less unmanageable. It 
 was, moreover, a difficult matter to obtain 
 the gas in a state of purity, and in sufficiently 
 large quantities for administration. 
 
 But the chief cause of the discredit into 
 which the gas fell was the want of knowledge 
 which necessarily prevailed as to the principles 
 which should be followed in its administration. 
 The methods employed by Wells and his fol- 
 lowers were such as to render success or failure 
 merely a matter of chance. The administra- 
 tion was very simply conducted. Some of the 
 gas was placed in a bag or bladder to which 
 was attached a tube, and the patient breathed 
 backwards and forwards. The results which 
 followed were necessarily exceedingly irregular, 
 as the chronicled accounts of Wells's demon- 
 stration and of subsequent attempts to produce 
 anaesthesia amply testify. In addition to the
 
 4 Introduction. 
 
 fact that much of the nitrous oxide which 
 was employed itself contained air, it must be 
 remembered that the re-breathing of a small 
 quantity of the gas necessarily led to its dilu- 
 tion by the air already present in the respira- 
 tory passages. The early administrations of 
 nitrous oxide were, indeed, administrations of 
 nitrous oxide mixed with considerable propor- 
 tions of nitrogen, oxygen, and carbonic acid 
 gas, to say nothing of the impurities other than 
 air which may or may not have been present 
 in the anaesthetic employed for inhalation. 
 Loud and prolonged lauohter, crvin<>', shout- 
 ing, praying, semi-maniacal excitement, and 
 many grotesque and amusing phenomena 
 manifested themselves — phenomena which we 
 now know to have been produced by the too 
 free dilution of the gas with the oxygen of 
 atmospheric air. In some of the cases in 
 which teeth were removed no pain was ex- 
 perienced ; in others the pain was only partly 
 abrogated ; in many the pain was felt with 
 the usual or even with more than the usual 
 acuteness. 
 
 It was not until 1863 that nitrous oxide 
 again began to emerge from the seclusion into 
 which it had been forced by reverses of fortune. 
 In this year a dentist named Smith, of New 
 Haven, Conn., took upon himself the responsi- 
 bility of submitting one of his patients to its
 
 Introduction. 5 
 
 influence, and the results were this time so 
 satisfactory that Colton, who was again the 
 administrator, forthwith proceeded to New 
 York where, with several influential dentists, 
 he established an association bearing his name, 
 for the painless extraction of teeth. Writing 
 in March, 1881, Dr. Colton stated that no less 
 than 121,709 administrations of nitrous oxide 
 had been conducted by the Colton Dental 
 Association since July, 1863, when the Asso- 
 ciation was founded, and that no accident had 
 occurred. 
 
 The news of Colton's success soon crossed 
 the Atlantic, and in January, 1864, Mr. Rymer, 
 a London dentist, reported 2 some experi- 
 mental administrations of nitrous oxide which 
 he had undertaken at the National Dental 
 Hospital. In these experiments either a 
 bladder or an india-rubber bag was used, and 
 the patient breathed the gas backwards and 
 forwards through a tube of large calibre. 
 According to the interesting paper published 
 by Mr. Rymer, the results were very satisfac- 
 tory. 
 
 So far as 1 am able to ascertain, the first 
 apparatus which possessed valves to prevent 
 re-breathing, was that used by Dr. Evans of 
 Paris, at a very successful demonstration which 
 he gave at the Dental Hospital ol London in 
 1868. The introduction oi this improved
 
 6 Introduction. 
 
 method of administration was quickly followed 
 by the manufacture of liquefied nitrous oxide ; 
 and, for the first time since Horace Wells's ex- 
 periment, nitrous oxide began to occupy an 
 unassailable position amongst its rivals in the 
 great field of therapeutics. Clover, whose in- 
 genuity in devising other anaesthetic apparatus 
 had already become conspicuous, quickly im- 
 proved upon the still rough nitrous oxide 
 inhalers, and laid down rules to be observed 
 in administration. 
 
 The complications which had attended the 
 earlier administrations of nitrous oxide, if such 
 they can be called, had been due to the pre- 
 sence of atmospheric air in too large quantities ; 
 those which now began to appear, with the 
 more perfected apparatus, were of an exactly 
 opposite nature. The recognition of the effects 
 produced by the admission of air now led to 
 its most stringent exclusion. The pendulum, 
 in fact, began to swing just as far in this direc- 
 tion as it had swung in the other. It was 
 thought that because air produced excitement 
 it should necessarily be wholly excluded — a 
 view which subsequent experience has taught 
 us to modify. With this new system of ad- 
 ministration, it soon became clear that a more 
 or less continuous inhalation was impossible. 
 Given that the gas was mixed with no air or 
 oxygen, that no re-breathing was possible, and
 
 Introduction . 7 
 
 that the inhaling" apparatus fitted and worked 
 accurately, nitrous oxide could not be given for 
 more than a very brief space of time. After 
 the inhalation had lasted a minute or so, certain 
 phenomena arose which necessitated the with- 
 drawal of the anaesthetic and the admission of 
 air. It therefore became clear that nitrous 
 oxide was par excellence the anaesthetic for very- 
 brief operations. Prolonged operations could 
 only be accomplished under its influence, and 
 these not very satisfactorily, by intermittently 
 allowing air to be respired. 
 
 The next step in the development of nitrous 
 oxide anaesthesia was taken by the late Prof. 
 Paul Bert, whilst engaged with his researches 
 upon barometric pressure. In a communica- 
 tion which he made to the Societe de Biologic, 
 on Feb. 9, 1878, he stated' 1 that he found 
 the effects of toxic gases upon living organisms 
 to be dependent upon their tension when 
 breathed. Nitrous oxide was a gas which, at 
 the ordinary atmospheric pressure, would only 
 produce anaesthesia when administered pure, 
 i.e., free from air. Unfortunately, however, in 
 administering nitrous oxide free from all air, 
 asphyxial phenomena soon became developed. 
 Hut if a mixture of one half nitrous oxide and 
 one half air were administered in a closed 
 chamber in which the ordinary barometric 
 pressure could be doubled, then the blood
 
 8 Introduction. 
 
 would receive just as much nitrous oxide 
 as when the gas was administered pure at 
 ordinary pressures, and just as much air as 
 would be breathed under natural circum- 
 stances. In this way prolonged anaesthesia 
 would be possible and asphyxia would be 
 avoided. As we shall subsequently see, Bert's 
 original proposition as to the necessity of em- 
 ploying perfectly pure nitrous oxide for the 
 production of anaesthesia was not true. His 
 idea was nevertheless as brilliant as it was 
 ingenious. Bert soon saw that by employing 
 oxygen instead of air it would be unnecessary 
 to dilute the nitrous oxide to anything like 
 the extent above indicated, so that a com- 
 paratively small increase in barometric pressure 
 would be needed. 
 
 On the nth May, 1878, Bert stated 4 that 
 he had successfully anaesthetised a dog with 
 a mixture of 80 per cent, of nitrous oxide and 
 20 per cent, of oxygen, under an additional 
 barometric pressure of 20 cm. There was no 
 excitement, and no material disturbance of the 
 normal functions of respiration and circulation. 
 The anaesthesia was everything that could be 
 desired. 
 
 On the 13th of July following he announced' 
 that, by his method, he had kept a dog 
 anaesthetised, and free from asphyxial symp- 
 toms, for half an hour ; that a manometer
 
 Introduction. 9 
 
 placed in an artery had not shown any percep- 
 tible variations in tension ; that the blood 
 pressure had been raised by irritating- exposed 
 nerves ; that irritation of the pheripheral end 
 of the vagus had stopped the heart ; and that 
 irritation of its central end had stopped the 
 respiration. 
 
 On Nov. 11th of the same year Bert made 6 
 a preliminary report of his results to the 
 Academic des Sciences. 
 
 On Feb. 15th, 1879, he announced 7 to the 
 Societe de Biologie that two days previously 
 his method of producing anaesthesia had been 
 for the first time tried upon the human subject. 
 A large air-tight metal chamber in which, by 
 means of pumps, the barometric pressure could 
 be raised, had been employed, and a mixture 
 of 85 per cent, of nitrous oxide and 15 per 
 cent, of oxygen had been administered from a 
 bag by means of a face-piece with two valves, 
 the barometric pressure in the chamber being 
 92 cm. (= an increase ol 17 cm.). The 
 operation, which was the avulsion of a toe 
 nail, had been a complete success. There had 
 been no pain, very little movement, no excite- 
 ment, a quiet pulse, and no loss of colour. 
 The tension of the nitrous oxide had been 
 85 x ''- = 104; and that of the oxygen 
 15 x y - = 1 8*4 ; in other words, that of the 
 nitrous oxide had been a little higher than
 
 io Introduction. 
 
 when the pure gas was given at ordinary 
 pressures, and that of the oxygen a little 
 lower than that of the air (20"q). Inciden- 
 tally Bert remarked that such a mixture as 
 that which he employed would not produce 
 anaesthesia at ordinary pressures — a point to 
 which I shall have to refer later on. 
 
 Bert's next communication 8 is dated Feb. 
 2 1 st, 1880. On this occasion he advocated a 
 total barometric pressure of 89*5 cm. and a 
 mixture ol similar proportions to those before 
 described. 
 
 The almost ideal type of anaesthesia pro- 
 duced by Bert's method attracted such atten- 
 tion, especially on the Continent, that attempts 
 were soon made to obtain similar results with- 
 out the employment of the costly and cum- 
 brous apparatus which Bert had devised. 
 Thus, Klikowitsch, 9 Winckel, 10 Ddderlein, and 
 Zweifel employed a mixture of 80 per cent, 
 of nitrous oxide and 20 per cent, of oxygen 
 in obstetric practice, administering the gases 
 as nitrous oxide itself is customarily adminis- 
 tered. In most of the cases in which records 
 are available an analgesic effect seems only 
 to have been produced, the patient's con- 
 sciousness having remained more or less intact 
 whilst her pains were relieved. 
 
 The first systematic application of Bert's 
 method to dental practice was made by Dr.
 
 Introduction . 1 1 
 
 C. Martin of Lyons, whose monographs 11 
 upon the subject are of great interest. Hav- 
 ing provided himself with an air-tight metal 
 chamber, and with the necessary machinery 
 for raising the barometric pressure, he pro- 
 ceeded to carry out Bert's directions. He 
 found, however, that by carrying them out 
 to the letter he met with considerable excite- 
 ment, and a " disturbed sleep, barely anaes- 
 thetic." The results were, in fact, inferior to 
 those obtainable with nitrous oxide as ordin- 
 arily given. He therefore tried an increase of 
 barometric pressure, raising it to 95 cm., 100 
 cm., and even to 125 cm., but without success. 
 He next tried 1 2 per cent, of oxygen instead 
 of 15 per cent., as recommended by Bert. 
 Anaesthesia now more rapidly ensued ; there 
 was less excitement ; there was no cyanosis ; 
 and recovery was satisfactory. These results 
 were obtained with a pressure of 105 cm. He 
 next raised the pressure to 1 10 cm., and for 
 the first time he obtained results comparable 
 to those described by Bert. When any excite- 
 ment began to manifest itself an increase in 
 the barometric pressure quickly arrested it. 
 Martin found it best to wait from 2 to 3 
 minutes before operating, and in the event of 
 a long anaesthesia being necessary he admin- 
 istered the mixture for 4 or even 5 minutes 
 before beginning the extraction. It is interest-
 
 12 Introduction. 
 
 ing that he found that if the pressure were 
 only ioo cm., or 105 cm., the patient reco- 
 vered more quickly than with a pressure of 
 i 1 5 or 1 20 cm. After-nausea was more fre- 
 quent in the prolonged administrations than in 
 the others. 
 
 I have elsewhere 12 described an interest- 
 ing experiment which M. Martin made upon a 
 dog. He kept the animal breathing a mixture 
 of 85 per cent, of nitrous oxide and 15 per cent, 
 of oxygen under a pressure of from 1 10 to 120 
 cm., for three consecutive days, without any 
 untoward effects during or after the insensibility. 
 Nothing could more forcibly demonstrate the 
 harmlessness of the mixture than such an ex- 
 periment. 
 
 On April 30th, 1883, Bert read his final 
 paper on the subject. 13 Having reviewed his 
 previous work, he stated that he had been 
 endeavouring to produce prolonged nitrous 
 oxide anaesthesia without the employment of 
 increased atmospheric pressure, and that he 
 had been successful in the case of the lower 
 animals. He regarded the alternate adminis- 
 tration of nitrous oxide and air as objectionable. 
 He first tried administering nitrous oxide and 
 oxygen alternately ; but the rapid elimination 
 of the former gas in the presence of the latter 
 led to a too sudden recovery. He next adminis- 
 tered, alternately, pure nitrous oxide and a
 
 Introduction. 13 
 
 mixture of nitrous oxide and oxygen similar to 
 that which he used in his pressure cases. He- 
 was thus able to keep a dog unconscious for 
 half an hour. At the time of his paper he had 
 not tried this method in human beings, nor can 
 I find any record of his having subsequently 
 done so. He urged surgeons, however, to give 
 it a trial, and stated that he intended to make 
 further experiments as to the best percentages 
 for the mixture. 
 
 Dr. Hillischer of Vienna, a well-known den- 
 tist, was the first to successfully employ nitrous 
 oxide and oxygen, at ordinary atmospheric 
 pressures, in dental surgery. His first paper 
 appeared 14 in 1886 ; his second' 5 and third' 6 
 in 1887; and his fourth 17 and fifth' 8 in 1890. 
 He suggested that the gaseous mixture 
 should be termed " Schlafgas " from the 
 sleep-like state into which patients pass under 
 its influence. Dr. Hillischer has adminis- 
 tered nitrous oxide and oxygen in upwards 
 of 15,000 cases; and the facts which he has 
 brought forward fully justify him in entertaining 
 such high opinions of the mixture he employs. 
 In his earlier cases he used gasometers, but 
 in latter years he has employed a regulating 
 apparatus by which the proportion of oxygen 
 can be increased or diminished during the 
 administration. He very properly directs atten- 
 tion to the necessity of this plan ; for patients
 
 14 Introduction. 
 
 vary very considerably in the percentage of 
 oxygen needed to secure a good type of 
 anaesthesia. 
 
 Dr. Hillischer states that he has administered 
 " Schlafgas " to patients of all ages; to those 
 suffering from advanced affections of the heart ; 
 to those with diseases of the lungs ; and to the 
 subjects of epilepsy and other nervous diseases. 
 He further states that he looks upon the 
 gaseous mixture as absolutely without contra- 
 indication — that he administers it to every 
 patient irrespective of any morbid state which 
 may be present. He admits that far more ex- 
 perience is needed in administering ''Schlafgas" 
 than in giving any other anaesthetic with which 
 we are acquainted ; and there can be no doubt 
 that, here again, he is perfectly correct. As to 
 the percentage of oxygen, he finds it best, in 
 most cases, to commence with 10 per cent, and 
 to gradually increase this to 15 or even 20 per 
 cent. With regard to alcoholic subjects and 
 others who are rebellious to the influence of 
 nitrous oxide with 10 per cent, of oxygen, he 
 reduces the proportion to 5 per cent, or even 
 less. On the other hand, if he finds that the 
 breathing becomes laboured, or that the features 
 assume a cyanotic appearance, he increases the 
 percentage of oxygen. 
 
 Dr. Witzel, of Essen-on-the-Ruhr, has also 
 administered nitrous oxide and oxygen for a
 
 Introduction. 15 
 
 large number of dental operations, and in some 
 interesting lectures which he published' 9 in 
 1889, he strongly urges the advantages of the 
 mixture and the correctness of Hillischer's 
 views. 
 
 Dr. H. C. Wood, 20 of Philadelphia, has 
 been unable to satisfy himself as to the anaes- 
 thetic effects of nitrous oxide and oxygen in the 
 lower animals. He states, for example, that 
 in the dog, nitrous oxide mixed with 8 per cent, 
 of oxygen indefinitely postpones anaesthesia. 
 The tests upon which he relies, in estimating 
 anaesthesia, are however, open to considerable 
 criticism. But, apart from this, we now pos- 
 sess such a mass of incontrovertible clinical 
 evidence that in the human being safe and 
 thoroughly satisfactory anaesthesia can be pro- 
 duced with nitrous oxide and oxygen, that it 
 is difficult to understand the views put forward 
 by this eminent authority. 
 
 In 1886 I commenced, at the Dental Hos- 
 pital of London, a series of experimental ad- 
 ministrations of nitrous oxide and oxygen, at 
 ordinary atmospheric pressures, with the object 
 of ascertaining the best method for general 
 use. It would serve no useful purpose to 
 describe, on the present occasion, the numerous 
 procedures which were adopted. No less than 
 [3 distinct plans were tried, each of which 
 necessitated a different form of apparatus.
 
 1 6 Introduction. 
 
 Those who are specially interested in the 
 matter, however, will find, in another publi- 
 cation,'" a full description of the stages by 
 which I arrived at the apparatus which I 
 brought out in 1 894 — the apparatus which is 
 fully described in the following chapter. That 
 it should have taken so long to devise a work- 
 able method may appear remarkable. But the 
 fact is, that, as the experiments proceeded, so 
 it became more and more clear that attention 
 had to be paid to the minutest possible details. 
 
 One of the first points that became obvious 
 was that sudden transitions in the composition 
 of the gases breathed were to be avoided. 
 For example, no good results could be obtained 
 by suddenly changing from ordinary nitrous 
 oxide to a mixture containing a considerable 
 percentage of oxygen ; or from one containing 
 a small to one containing a large percentage ; 
 or vice versa. 
 
 I then endeavoured to ascertain whether any 
 definite percentage of oxygen with nitrous 
 oxide would answer in every case. I found 
 that in most cases a mixture containing 1 2^ 
 per cent, of oxygen answered admirably. By 
 its use all asphyxial phenomena were avoided ; 
 there was no stertor, jactitation, or lividity ; 
 breathing continued without the slightest 
 embarrassment ; the natural colour was pre- 
 served ; and in most cases the anaesthesia
 
 Introduction. 17 
 
 was perfect and tranquil. In a certain number 
 of cases, however, excitement and screaming 
 arose, and it was necessary to let some pure 
 nitrous oxide into the mixture in order to 
 terminate the case satisfactorily. My results 
 with this mixture were published in the 
 Lancet.™ 
 
 The next point that proved to be of import- 
 ance was the necessity of absolutely excluding 
 ai r during the inhalation. There can be no 
 doubt that in administering nitrous oxide in 
 the usual manner a small quantity of air is 
 very likely to gain access to the lungs, either 
 under the face-piece, or at the expiratory 
 valve. If nitrous oxide, with or without 
 oxygen, be administered in such a way that 
 the inhaling bag is kept distended, it is 
 obvious that no such admixture of air can 
 occur. I was at a loss for some time to 
 account for the better results obtained in 
 administering nitrous oxide and oxygen (the 
 oxygen being present to the extent of 12- or 
 
 10 per cent.) when the gases issued from the 
 gasometer under slight pressure ; but there is 
 little doubt that the explanation given is the 
 true one, and that when the gases were given 
 with a half-distended bag small quantities of 
 air gained access and disturbed the anaesthesia. 
 
 The admixture of a small quantity of air 
 during an ordinary administration of nitrous
 
 1 8 Introduction. 
 
 oxide is, if anything, an advantage, at all 
 events in most cases ; but it is not so with 
 nitrous oxide and oxygen. 
 
 I next came to the conclusion that 10 per 
 cent, of oxygen was preferable to 12^ per 
 cent., and when this mixture was adminis- 
 tered from a distended bai>" very trood results 
 occurred in most cases. 
 
 It soon became clear, however, that there 
 w r as no definite percentage of oxygen which in 
 every case would prevent all traces of asphyxia, 
 and yet would in no way interfere with anaes- 
 thesia. Patients varied too widely for the 
 employment of any method of this nature. It 
 was obviously necessary to have control over 
 the percentage of oxygen, so that it could be 
 increased or diminished during the administra- 
 tion, in accordance with the needs of the case. 
 I therefore tried various kinds of regulating 
 apparatus which I devised. I also tried Hillis- 
 cher's apparatus ; but the results which I 
 obtained with it were not satisfactory. Its 
 chief fault seemed to be that it did not allow of 
 fine enough adjustment in its oxygen inlet. 
 The channels through it, moreover, were of 
 very small calibre, the bags were too far from 
 the mouthpiece, and the valves did not work 
 with that perfect freedom which is essential. 
 
 The first apparatus with which I obtained 
 reliable results was described bv me before
 
 Introduction. 19 
 
 the Odontological Society in 1892 ; 21 and I 
 demonstrated 23 the results which could be 
 obtained with it, at the meeting of the British 
 Dental Association at Manchester in the same 
 year. I need not refer to its mechanism here, 
 as the apparatus was similar in its main prin- 
 ciples to that which is fully described in the 
 following- chapter. There were two separate 
 bags ; one for nitrous oxide, the other for 
 oxygen. The oxygen was admitted to the 
 nitrous oxide through thirteen small circular 
 holes, any number of which could be opened. 
 I found four flap valves necessary : two pre- 
 vented re-breathing, and two prevented any 
 diffusion of the gases before they were mixed. 
 The expiratory valve was found to be much 
 more efficient in preventing air gaining access 
 during its closure when a chimney was fitted to 
 its orifice. If the valve was not thus guarded. 
 a small quantity of atmospheric air was very 
 liable to be drawn in during its closure. 
 
 The apparatus which I now use was brought 
 before the notice of the British Dental Asso- 
 ciation at Newcastle-on-Tyne in 1894. 24 I 
 propose, however, to fully describe it again 
 here, and when this has been done, to consider 
 in detail the effects which it produces. By 
 this plan we shall, I think, be in a favourable 
 position to realise the immense advantages oi 
 obtaining an anasth( sia which, when proper!)
 
 2o Introduction. 
 
 established, may be regarded as absolutely safe, 
 and certainly far more satisfactory, from the 
 operator's point of view, than that which we 
 have been accustomed to meet with when 
 employing nitrous oxide gas in the usual 
 manner.
 
 CHAPTER II. 
 APPARATUS. 
 
 i. Gasometer Methods. 
 
 Whilst it is true, as already stated, that 
 there is no definite percentage of oxygen which 
 will answer satisfactorily in every case, and 
 that, to obtain the best results, a regulating 
 apparatus is essential, it is equally true that 
 a continuous administration, by means of a 
 gasometer, of certain known mixtures of the 
 two gases, will produce better results than can 
 be obtained by nitrous oxide alone. 
 
 The question hence arises : What percent- 
 age of oxygen should be used in gasometer 
 administrations ? 
 
 In reply to this question I may say that, 
 during the course of the investigation referred 
 to in the Preface;, I have found that of all the 
 mixtures which I have tried for continuous 
 administration, the best results have been 
 secured with those containing 5, 6, 7 or 8 
 per cent, of oxygen, according to the type of
 
 22 Apparatus. 
 
 patient. I hope soon to be in a position to 
 speak more definitely upon this interesting 
 point, for much misconception at present exists 
 as to the effects produced by different per- 
 centages of oxygen. Without going further 
 into detail here, I may say, however, that 
 if the apparatus works accurately, and air 
 is absolutely excluded, percentages of oxygen 
 above those indicated, are, as a general rule 
 unnecessary. That cases arise in which higher 
 or lower percentages should be given is 
 beyond doubt ; but such cases can only be 
 successfully met when a regulating apparatus 
 is used. Given that no such apparatus is 
 at hand, the percentages to which I have 
 referred are certainly preferable to others, and 
 with these percentages good results may be 
 attained in most, if not in all cases. I have 
 found that the chief objection to higher per- 
 centages is the liability to excitement. It 
 must be remembered, too, that with 5 per cent, 
 of oxygen one is very near the asphyxial 
 borderland. Indeed, when administering a 
 mixture containing this percentage of oxygen, 
 cases will occasionally be met with in which 
 minor degrees of stertor, jactitation, and 
 lividity, are present. Such cases would neces- 
 sarily follow a different and more satisfactory 
 course w"ere a regulating apparatus employed. 
 A word of caution is perhaps necessary with
 
 Apparatus. 23 
 
 regard to keeping nitrous oxide and oxygen 
 together, in gasometers, for any length of time. 
 Hillischer states that traces of the higher 
 oxides of nitrogen were detected, at the end of 
 a week, in a mixture which had been kept in 
 Ludwig's laboratory. The two gases should 
 therefore be mixed as required. 
 
 2. The Author's Regulating Apparatus. 
 
 Before describing this in detail it may be 
 well to briefly enumerate the various require- 
 ments which must be fulfilled by any regula- 
 ting apparatus for the administration of nitrous 
 oxide and oxygen. They are as follows : — 
 
 (1) There must be a plentiful supply of the 
 two gases from easily and quietly working 
 cylinders : 
 
 (2) The bags into which the gases pass must 
 be capable of being kept partly and equally 
 distended during the administration : 
 
 (3) The bags must be as close as possible 
 to the face-piece : 
 
 (4) The channels throughout the apparatus 
 must be sufficiently large to avoid any stress 
 whatever being thrown upon respiration : 
 
 (5) The regulating portion of the apparatus 
 must allow of very small increments and decre- 
 ments in the proportion of oxygen breathed 
 with the nitrous oxide :
 
 24 
 
 Apparatus. 
 
 (6) There must be accurately working 
 valves : (a) for preventing- all re-breathing, 
 
 A/r 
 
 H& +• Gj'i /.< /0 
 
 HI. 
 
 
 Fig. i. — The Author's apparatus. 
 
 and (b) for preventing diffusion between the 
 contents of one bag and the contents of the 
 other :
 
 Apparatus. 25 
 
 (7) The expiratory valve must not allow of 
 any air being sucked back during its closure 
 in the inspiratory phase : 
 
 (8) The apparatus must be so constructed 
 that, when first applied to the face, air will be 
 breathed freely through it, and through the 
 same valves that will be subsequently used 
 when the mixture is turned on : 
 
 (9) The apparatus must admit of being 
 readily taken to pieces without the use of 
 tools, so that its various parts may be inspected 
 from time to time : 
 
 (10) The inhaling portion of the apparatus 
 must admit of being thoroughly cleansed, 
 and of being treated with antiseptic solutions 
 should occasion require. 
 
 (11) The whole apparatus must be suffi- 
 ciently portable to be carried in a hand bag. 
 (See Fig. 5.) 
 
 Fig. 1 represents the complete apparatus. 
 It consists of two nitrous oxide cylinders, one 
 oxygen cylinder, a combined stand and 
 union, double india-rubber tubes (one run 
 ning inside the other) for conducting the two 
 gases from the cylinders to the bags, two 
 india-rubber bags joined together by a sep- 
 tum common to both, a combined regulating 
 stopcock and mixing chamber, and a face- 
 piece. 
 
 The two nitrous oxide cylinders, the single
 
 26 
 
 Apparatus. 
 
 oxygen cylinder resting upon them, and the 
 combined stand and union, are shown in 
 diagrammatic section in Fig. 2. 
 
 Each nitrous oxide cylinder will furnish 50 
 gallons of nitrous oxide gas ; and each oxygen 
 cylinder about 15 gallons of oxvgen. 
 
 Fig. 2. — Diagrammatic section of cylinders, and of combined stand and 
 
 union. 
 
 The combined stand and union is so made 
 that the cylinders can be connected together 
 or disconnected without the aid of spanners 
 or other appliances. In order to prevent 
 undue strain to the union when the foot-key 
 is being used upon the oxygen cylinder, an 
 adjustable screw pillar, fixed to the stand 
 below, is made to engage that part of the 
 under surface of the oxygen cylinder upon 
 which foot-pressure directly tells. In this way 
 all foot-pressure is transmitted to the stand.
 
 Apparatus. 
 
 27 
 
 When the foot-key is placed upon one of 
 the nitrous oxide cylinders, and is turned, the 
 liberated nitrous oxide passes to its bag- 
 through brass and india-rubber tubes of com- 
 
 Fig. 3. — Diagrammatic section of the india-rubber transmitting tubes 
 and bags through which the two gases pass on their way to the 
 regulating stopcock and mixing chamber. 
 
 paratively large calibre. When oxygen is 
 similarly released from its cylinder it passes 
 to its ba<f through brass and india-rubber
 
 28 Apparatus. 
 
 tubes which are so much smaller than the 
 nitrons oxide tubes that they are made to 
 travel inside the latter. Thus, in Fig. 2, it 
 will be seen that, in the combined stand and 
 union, the metal transmitting tube for the 
 oxygen is inside that for the nitrous oxide. 
 
 Fig. 3 shows, in diagrammatic section, the 
 two india-rubber transmitting tubes, one in- 
 side the other, conveying their respective gases 
 to the two india-rubber bags. These bags are 
 of about equal capacity, and are so made that 
 a rather thick india-rubber septum is common 
 to both. When full they have the out- 
 ward appearance of a single bag. Care is 
 needed to prevent the india-rubber from be- 
 coming punctured or otherwise injured. Even 
 if only one or two minute punctures exist, 
 they may be quite sufficient to allow of an 
 admixture of atmospheric air. The bags, 
 moreover, must not be too small ; otherwise 
 it may be difficult or impossible, during the 
 administration, to keep the nitrous oxide bag 
 equal in size to the oxygen, especially if the 
 patient should breathe very deeply. 
 
 The regulating stopcock and mixing cham 
 ber is shown in detail in Fig. 4. The nitrous 
 oxide bag (see big. 3) is attached to the tube 
 NOT, the orifice of which, NOO, is shown, 
 The oxveen bag is attached to OT, which 
 communicates above with a little oxygen cham-
 
 Apparatus. 
 
 29 
 
 ber OC. There are ten minute holes between 
 the oxygen chamber OC and the mixing- 
 chamber. Only three of these ten holes, OO, 
 
 Fig. 4. — Regulating stopcock and mixing chamber. 
 
 appear in the figure. The tubes, OT and 
 
 NOT are furnished with removable valves, iv,
 
 30 Apparatus. 
 
 and w', which act during inspiration, and which 
 prevent diffusion between the gases of the two 
 bags. AH is the air-hole. IV is the main 
 inspiratory valve. EV is the expiratory valve, 
 with its chimney C. 
 
 PD. shown in dotted outline, is a partial 
 diaphragm, mounted upon a removable inner 
 tube, which serves to direct the expirations 
 towards the expiratory valve EV. In the 
 absence of this partial diaphragm there is a 
 tendency for the expirations to pass back again 
 beneath IV, and so to throw the valve-action 
 completely out of gear. 
 
 The chimney C is essential in preventing air 
 being drawn back through EV during its 
 closure at each inspiration. 
 
 The inner drum, ID, which is made to 
 revolve by means of the handle H, has a large 
 portion of its circumference cut away to form a 
 long slot S. The handle H is prolonged into 
 an indicating point or indicator. 
 
 To the circumference of the stopcock and 
 mixing chamber is fixed a flange with "AIR," 
 " N 2 0," and " N 2 () + O," engraved upon it. 
 There are also figures, from " i " to " 10" in- 
 clusive, belonging to the " N 2 + O " part of 
 the flange. When the indicator of the handle 
 H points to " AIR," as in Fig. i, the slot S of 
 the drum ID allows air to pass through AH 
 and IV during the act of inspiration ; but by
 
 Apparatus. 31 
 
 reason of the other part of the drum covering 
 the orifices NOO and OO, nothing but air is 
 breathed. When the indicator is moved to 
 " N 2 0," the drum closes AH, and opens NOO, 
 the oxygen orifices still remaining covered. 
 Pure nitrous oxide is therefore inhaled. When 
 the indicator reaches " 1 " on the " N 2 + O " 
 part of the flange, the nitrous oxide orifice 
 NOO still remains open, but, in addition, one 
 of the oxygen orifices OO, becomes uncovered 
 by the revolution of the inner drum. When 
 " 2 " is reached, two oxygen holes are open, 
 and so on up to " 10," the nitrous oxide orifice 
 remaining patent throughout. 
 
 It may thus be said that directly the in- 
 dicator is made to point to " N 2 0," there passes 
 through the stopcock a continuous and large 
 stream of nitrous oxide, and that any number 
 of small streams of oxygen, from one to ten 
 inclusive may, at will, be added to this con- 
 tinuous stream of nitrous oxide. As the in- 
 dicator reaches the various points on the 
 flange an audible click is produced by means 
 of a spring attached to the handle. 
 
 All the valves are made of thin sheet india- 
 rubber, and it is important that they should 
 be in good order. Should they become in- 
 elastic from age, or should they in any way 
 fail to act, as they are intended to act, with 
 perfect accuracy, the apparatus will not pro-
 
 32 Apparatus. 
 
 duce good results. For example, an apparatus 
 may let through much larger proportions 
 of oxygen than usual if the nitrous oxide 
 valve iv should happen to adhere, along a part 
 of its circumference, to the rim upon which 
 it rests ; the explanation being that the 
 suction exerted by the inspirations of the 
 patient would have a greater influence than 
 usual in drawing oxygen from the oxygen bag 
 owing to the abnormal resistance at the nitrous 
 oxide valve. The valves of the apparatus 
 are so arranged as to act most efficiently when 
 the main expiratory valve is kept as horizontal 
 as possible. If the whole apparatus be much 
 tilted during use, as would be the case if the 
 patient's head should be thrown very far back, 
 the valves may not act efficiently. 
 
 The apparatus may be taken to pieces with 
 the utmost readiness by simply removing, with 
 the finder, the screws which connect the handle 
 H to the inner drum ID. In this way the 
 drum may be removed and the valves and 
 oxygen orifices inspected. The latter may 
 occasionally require to be freed from dust. 
 
 Three or four face-pieces of different sizes 
 should be at hand. The air cushion of the face- 
 piece employed should be only moderately in- 
 flated, otherwise it may not fit as well as is 
 desirable. 
 
 In order that good and reliable results may
 
 Apparatus. 33 
 
 be obtained, it is important that the whole 
 apparatus should be carefully handled. The 
 process of anaesthetising with nitrous oxide and 
 oxygen is a more delicate process than that 
 involved in the ordinary administration of 
 nitrous oxide alone ; and trifling defects in the 
 apparatus are liable to interfere with results. 
 The connections must be tested ; the bags in- 
 spected frequently ; the stopcock taken to pieces 
 occasionally — in fact, the anaesthetist must take 
 a personal interest in his apparatus if he wishes 
 to succeed with it. 
 
 A word may here be said as to the relative 
 proportions of nitrous oxide and oxygen 
 which the apparatus is capable of furnishing. 
 As will be pointed out in the following chapter, 
 much will depend upon the state of the bags 
 during the inhalation, and especially upon 
 whether they are kept of equal size throughout. 
 But it is necessary to mention, in the present 
 connection, that each apparatus possesses slight 
 peculiarities of its own. It is a difficult matter 
 to produce two models which will act in pre- 
 cisely the same way. The result is that the 
 anaesthetist must observe what his particular 
 apparatus is capable of doing. With one model 
 it may not be possible to reach "8" upon the 
 flange without excitement arising ; whilst with 
 another model "9" or " 10" may be reached in
 
 34 Apparatus. 
 
 nearly every case without any such symptoms 
 occurring. 
 
 But when once the anaesthetist has found out 
 how far he can go with his particular apparatus 
 he will always be able to depend upon it work- 
 ing in the same way, provided, of course, that 
 he keeps its valves, oxygen holes, bags and 
 other parts in good order. 
 
 The apparatus is manufactured by Messrs. 
 Barth & Co., of Poland Street, Oxford Street, 
 to whom I am much indebted for the patience 
 and skill they have shown in carrying out my 
 designs. It may either he obtained from them 
 or from Messrs. Ash & Sons, Broad Street, 
 Golden Square.
 
 35 
 
 CHAPTER III. 
 
 PREP A RATIONS. 
 
 The old adage " Everything that is worth 
 doing is worth doing well " forcibly applies to 
 the use of anaesthetics in dental practice. It 
 is only by attention to detail that success can 
 be achieved in everv case. The dentist who 
 
 J 
 
 regards preparations and precautions as un- 
 necessary, and who expects his colleague to 
 entertain similar views, has only himself to 
 thank when difficulties arise. There is no 
 known method of anaesthetising which will 
 succeed when the corsets are tightly laced, 
 the stomach full, or the posture faulty. It is, 
 I think, a mistake to suppose that patients are 
 made nervous by the few preparations which 
 are essential to success. I would rather say 
 that most patients gain assurance when they 
 see that pains are being taken to obtain the 
 best results. 
 
 When practicable, an interval of about 
 four hours should have elapsed between the
 
 36 Preparations. 
 
 last meal and the administration. The middle 
 of the day (from 1 2 to 2 o'clock) is a very 
 convenient time for the extraction of teeth 
 under anaesthetics. Precautions as to diet are 
 especially important in the case of children, 
 and when a long anaesthesia is needed (see 
 p. 86). 
 
 Stimulants should, as a rule, be avoided. 
 In very feeble subjects, however, and in those 
 inclined to faint, an exception may be made 
 if desired. I have notes of a child who was 
 given by his parents some brandy and water 
 before starting- for the dentist's. A very 
 unsatisfactory anaesthesia followed, and the 
 little patient retched violently. 
 
 In the case of children, and even in that 
 of adults, when circumstances permit, it is 
 well that the bladder should be empty. 
 Micturition during the administration is, how- 
 ever, exceedingly rare. 
 
 Whenever circumstances are favourable, it 
 is a good plan to have everything in readi- 
 ness before the patient enters the room. The 
 anaesthetist should see that his apparatus is 
 in working order ; he should fill the ba«-s 
 with their respective gases to the extent of 
 about two-thirds, so that they are equally and 
 moderately distended ; and he should leave 
 the foot-key on one of the nitrous oxide 
 cvlinders readv for use.
 
 Preparations. 37 
 
 The following appliances should always be 
 in readiness : — Mouth props of various sizes, 
 a Mason's gag, a pair of tongue forceps, some 
 nitrite of amyl capsules, and instruments for 
 performing tracheotomy. Although I have 
 never had occasion to use tongue forceps, 
 nitrite of amyl, or tracheotomy instruments in 
 connection with this form of anaesthesia, it is 
 nevertheless important to be fully prepared 
 for all contingencies. 
 
 A third person should always be present 
 in the room from the time the inhalation is 
 begun till the patient's consciousness is fully 
 restored. 
 
 The administration should not be under- 
 taken by the same person who performs the 
 operation. 
 
 The importance of loose clothing cannot be 
 too strongly insisted upon. In order that the 
 induction of anaesthesia may be successfully 
 accomplished, it is necessary that the air in 
 the lungs should be exchanged as quickly as 
 possible for the anaesthetic gas. In order 
 that this may be effected, the bases of the lungs 
 must expand by diaphragmatic action. If there 
 be tightly-fitting corsets or waist bands, the 
 diaphragm cannot descend fully; the breath- 
 ing will be restricted and to a great extent, or 
 entirely, thoracic ; interchange between the air 
 in the lungs and the anaesthetic will only
 
 38 Preparations. 
 
 take place freely in the upper parts of the 
 lungs ; and the onset of anaesthesia will there- 
 fore be delayed. Patients who are tightly 
 laced may do their best to quickly fill their 
 lungs with the anaesthetic gas, but they will 
 fail. All constricting clothing about the upper 
 part of the chest and neck should also be 
 loosened with the object of allowing respira- 
 tion to proceed perfectly freely. It is not a 
 bad plan for ladies to come to the dentist's 
 loosely attired, so that no further preparation 
 in this direction need be made. 
 
 The posture of the patient has a very 
 decided influence in modifying the phenomena 
 of anaesthesia. I have so recently entered at 
 length into this subject that I must refer the 
 reader to my paper 25 specially dealing with it. 
 I may, however, say on the present occasion, 
 that whenever circumstances permit, the patient 
 should be allowed to assume a comfortable and 
 unrestrained posture, and that his head should 
 be permitted to retain its natural position in 
 regard to the body, being neither flexed upon 
 the chest nor extended toward the spine (see 
 fig. 5, p. 44). Good results cannot be expected 
 if the administration be begun when the 
 patient's head is thrown back upon the spine. 
 Should the operator wish to have the head 
 thrown more backwards than is represented in 
 the figure, the best plan is to anaesthetise the
 
 Preparations. 39 
 
 patient in the posture depicted, and to tilt the 
 whole chair backwards just before the face-piece 
 is removed for the commencement of the opera- 
 tion. In this way the proper angle for the 
 operation will be obtained without disturbing 
 the normal relations of the head to the trunk. 
 Should the chair not admit of this movement, 
 an inflated air pillow should be placed under 
 the head before commencing the administration, 
 and, just before the face-piece is removed, the 
 air may be allowed to escape. In this way the 
 head will fall into the extended position ready 
 for the operation, and the comfort of the patient, 
 as well as the convenience of the operator and 
 of the anaesthetist will have been provided for. 
 If any relatives or friends of the patient be 
 present they should be requested to remain in 
 an adjacent room during the administration and 
 operation. Should they express a desire, 
 however, to be present, they should not be 
 permitted to stand near the chair, or to hold 
 the patient's hand, as such attentions will 
 almost certainly have an opposite effect to that 
 which is intended, and will introduce a dis- 
 turbing element into the anaesthesia. In many 
 cases friends wish only to be present during 
 the induction of anaesthesia, and there is little 
 to be said against this : directly consciousness 
 has been lost, a signal should be given them 
 in order that they may retire during the actual
 
 40 Preparations. 
 
 operation. Owing to the fact that by the use 
 of oxygen with nitrous oxide, a far more tran- 
 quil and sleep-like anaesthesia is produced than 
 with nitrous oxide alone, there is less objection 
 to friends being present than under other 
 circumstances. 
 
 A suitable mouth-prop should be inserted 
 immediately before the administration is be<join. 
 The prop which I employ is fully described 
 elsewhere. 12 It is made of aluminium, and is 
 so shaped that it rarely if ever slips when once 
 put into position. It is important in fixing the 
 prop that the mouth should be opened as widely 
 as possible, except when stretching the lips 
 would inconvenience the operator, or when 
 widely opening the mouth would give the 
 patient great discomfort, or excite retching 
 movements. In the extraction of wisdom 
 teeth it is usually a good plan not to open the 
 mouth to its fullest extent. Should the in- 
 sertion of the prop excite retching movements, 
 the remedy which usually answers is an ex- 
 ceedingly simple and efficient one. The 
 patient should first be requested to breathe 
 deeply through the open mouth, to count his 
 respirations to himself, and to concentrate his 
 whole attention on these points. The prop is 
 then put in whilst he is thus breathing and 
 counting ; the face-piece is quickly applied ; 
 the gases are admitted ; and if the patient
 
 Preparations. 4 1 
 
 continue to fix his attention on the points 
 suggested, he will pass into anaesthesia with- 
 out the recurrence of any retching move- 
 ments.
 
 4 2 
 
 CHAPTER IV. 
 THE ADMINISTRATION. 
 
 With the object of making this part of the 
 subject as clear as possible, it will be well to 
 confine our attention in the present chapter 
 to the details of an ordinary or average ad- 
 ministration, and to the effects which such 
 an administration produces in an ordinary or 
 average patient. As the majority of those 
 who require anaesthetics in dental practice are 
 women, it will be advisable to take as our 
 normal type a young woman, of medium height 
 and build, of medium complexion, and not 
 markedly nervous. When we have fully con- 
 sidered the method which should be adopted 
 in anaesthetising such a patient we shall be in 
 a position to discuss, in a subsequent chapter, 
 the slight modifications in procedure which are 
 essential in dealing with other types of patients. 
 
 An endeavour should be made to avoid all 
 disturbing influences during the administration. 
 The room should be kept quiet. Friends should
 
 77/i? Administration. 43 
 
 not be permitted to hold the patient's hand. 
 There is no objection to the operator holding 
 the hand of a nervous patient if confidence is 
 likely to be gained in this way. The anaes- 
 thetist should say a few words to the patient 
 during the first moments of the inhalation, but 
 not a word should be uttered after this, until 
 the operation has been completed. With 
 nervous subjects it is often a good plan for 
 the anaesthetist to count aloud, as the patient 
 breathes. Under any circumstances the anaes- 
 thetist should instruct the patient how to 
 breathe. The anaesthesia is likely to be dis- 
 turbed by any conversation, loud noises, the 
 comments or questions of anxious friends, &c. 
 Even feeling the pulse at the wrist is likely 
 to induce nervousness, and should be avoided. 
 In a word, the patient should be left as much 
 as possible to herself. 
 
 When considering, in Chapter III., the pre- 
 parations which are necessary before an ad- 
 ministration is commenced, it was stated that 
 the bags containing the nitrous oxide and 
 oxygen should, if possible, be charged with 
 their respective gases, and that the foot-key 
 should be placed upon one of the nitrous oxide 
 cylinders, before the patient enters the room. 
 
 The patient having assumed a perfectly com- 
 fortable posture, and a mouth-prop having been 
 adjusted, the face-piece should be applied.
 
 44 
 
 The Administration. 
 
 Air will now be breathed through the ap- 
 paratus, each expiration escaping at the ex- 
 piratory valve. 
 
 Fio. 5. — The administration. 
 
 The anaesthetist should request his patient 
 to take long- deep breaths, backwards and 
 forwards, through the mouth. Nasal breathing
 
 The Administration. 45 
 
 should be avoided. If there is any "holding 
 the breath " or hesitation in breathing", this 
 must be corrected before proceeding further. 
 The most absolute co-aptation of the face- 
 piece is essential. The sound made by the 
 flapping of the valves is the best proof that 
 the face-piece is fitting well ; and this sound 
 should always be heard before the mixture is 
 turned on. 
 
 When it is clear that the face-piece fits 
 accurately, the indicator, which has hitherto 
 been pointing to " AIR," should be turned to 
 " 2." At the same moment the foot should 
 slightly turn the foot-key in order to quickly 
 replace the nitrous oxide which the patient is 
 breathing. 
 
 It is impossible to state, with precision, what 
 percentage of oxygen will come through when 
 the indicator is thus turned to "2,'* for one 
 apparatus will be found to differ slightly from 
 another, and much will depend upon the 
 relative sizes of the bags at the moment. It is 
 sufficient for our purpose that quite a small 
 percentage — roughly about 2, 3, or 4 per cent. 
 — will be first breathed. The percentage is so 
 small, indeed, that the oxygen bag hardly 
 appears to alter in size throughout, and no 
 further addition to it from the oxygen cylinder 
 is necessary in dental administrations, even in 
 the case of lon<>' inhalations.
 
 46 The Administration. 
 
 The initial sensations of the patient are 
 very similar to those experienced under nitrous 
 oxide itself, and are by no means unpleasant. 
 I am still unable to decide whether the almost 
 invariable absence of suffocative sensations is 
 referable to the presence of the small propor- 
 tion of oxygen, or whether it is due to the 
 very free channels of the apparatus. It is, 
 however, certain that patients hardly ever 
 experience the slightest discomfort in breath- 
 ing the mixed gases, provided, of course, that 
 the clothing is perfectly loose. Consciousness 
 is not lost quite so quickly as with nitrous 
 oxide alone ; but in other- respects the early 
 sensations are identical, and need not therefore 
 be described. 
 
 The anaesthetist has now to pay attention to 
 three points at the same time. He has (i).to 
 keep the face-piece very accurately applied ; 
 (2) to keep the two bags equally and only partly 
 distended ; and (3) to increase or diminish the 
 proportion of oxygen according to the symp- 
 toms of the patient. It will therefore be advis- 
 able to consider the remaining part of the 
 administration under these three heads. 
 
 (1) The fitting of the face-piece. Whilst 
 there is much to be said in favour of the face- 
 piece, as opposed to the mouth-tube, lor nitrous 
 oxide inhalation, there can be no doubt that it 
 is more difficult, when employing the former, to
 
 The Administration. 47 
 
 completely exclude atmospheric air than when 
 using the latter. There are, however, several 
 objections to mouth-tubes. The idea of holding 
 between one's lips a tube that has just been 
 used by another patient is not a pleasant one, 
 even though the most scrupulous cleanliness 
 may have been enforced. Moreover, it is 
 essential, in using a mouth-tube, that the nose 
 should be clipped or held, in order to prevent 
 any air entering the nasal passages. And, 
 lastly, breathing is liable to be impeded by the 
 tube necessarily being of small calibre. Taking 
 everything into consideration, therefore, the 
 face-piece has distinct advantages. But con- 
 siderable practice is required before perfect 
 coaptation can be secured in all cases. Un- 
 fortunately, when employing the mixed gases, 
 any want of coaptation cannot be met by 
 increasing the pressure at which the gases 
 enter the face-piece, for distension of the bags 
 would at once throw the regulating mechanism 
 out of gear. 
 
 (2) The fulness and relative sizes of the 
 bags. In order that the regulating mechanism 
 may work properly it is necessary that the two 
 bags should be kept as nearly as possible of 
 equal size throughout, and only partly dis- 
 tended. The anaesthetist has, in fact, to use 
 his loot as much as his hand, and to let in 
 nitrous oxide; to its bag in such quantities that
 
 48 The Administration. 
 
 the bag remains the same size as the oxygen 
 bag. The latter necessarily grows gradually 
 smaller, and the anaesthetist, therefore, has to 
 keep the nitrous oxide bag less and less full. 
 
 (3) The Admission of Oxygen. Given that 
 the apparatus works satisfactorily and in the 
 usual manner, the anaesthetist must regulate the 
 admission of oxygen in accordance with the 
 type of his patient, and with the symptoms that 
 the patient displays. There is, unfortunately, 
 no rule which will apply to every case. After 
 some experience the administrator will recog- 
 nise that he has at his disposal an apparatus by 
 which he can, if he wishes, obtain two totally 
 different groups of symptoms. 
 
 If very little or no oxygen be given, the 
 ordinary phenomena of nitrous oxide narcosis 
 will present themselves, viz., blueness, lividity, 
 or duskiness of the features, epileptiform 
 muscular twitchings of the trunk, extremities 
 and face, and obstructive stertor. 
 
 If too much oxygen be admitted, there 
 will be no alteration in coiour, no epilepti- 
 form convulsive movements, and no stertor, 
 but violent mental and muscular excitement 
 (laughter, shouting, kicking, stamping and 
 struggling) will attend the administration, and 
 will be ail most as objectionable as the asphyxial 
 phenomena produced by pure nitrous oxide. 
 
 There are thus two extremes — two ends of
 
 The Administration. 49 
 
 the scale — and each extreme must be avoided. 
 The anaesthetist has, in fact, to steer a middle 
 course, and to keep a sharp look-out. A little 
 practice will enable him to avoid the Scylla of 
 asphyxia on the one hand, and the Charybdis 
 of excitement on the other. He will find, after 
 a time, that he is able to detect even slight 
 deviations from the proper course, almost 
 before such deviations have taken place. 
 
 Generally speaking, a gradual and progres- 
 sive increase in the percentage of oxygen is 
 advisable. In such a case, for example, as 
 that which we have pictured to ourselves, the 
 best results will be obtained by starting the 
 inhalation, as already mentioned, with from 2 
 to 4 per cent, of oxygen, and then progressively 
 increasing this proportion to 8 or 9 per cent. 
 It seems to mc that it is a mistake to adopt 
 the plan which is customary in Germany, and 
 to begin with as much as 10 per cent, of 
 oxygen. It is surely more rational to make an 
 allowance; for the oxygen present in the lungs 
 when the administration begins, and we should 
 therefore commence with a very small per- 
 centage of this gas. As the lungs lose the air 
 they contained, so the percentage of oxygen 
 in the mixture may be increased, provided that 
 no symptoms of excitement arise. II a 10 per 
 cent, mixture be used from the commencement, 
 excitement is liable to ensue from the undue 
 4
 
 50 The Administration. 
 
 proportion of oxygen. Witzel, 19 for example, 
 who follows this course in his administrations, 
 finds it necessary to employ arm-rings, foot- 
 straps, and other appliances to restrain the 
 patient's movements, and to have at hand, on 
 all occasions, strong- and trained assistants. 
 Such precautions are unnecessary when the 
 method here advocated is followed. 
 
 I find it best, as a general rule, to allow two 
 or three inspirations of the mixture to take 
 place with the indicator at "2"; two or three 
 more with it at " 3 " ; two or three more with 
 it at "4"; and so on till "6" or "7" is reached. 
 Usually, by the time the indicator has reached 
 this point the anaesthetist will be able to 
 recognise the existence of one of three condi- 
 tions. There will either be evidence to show 
 
 (a) that the proportions of the two gases 
 are properly adjusted ; 
 
 (/3) that the proportion of oxygen is rather 
 in excess of that which is needed, and should 
 therefore be diminished ; 
 
 or (y) that this proportion is rather less than 
 that required, and should therefore be in- 
 creased. 
 
 (a) The absence of any indications of ex- 
 citement on the one hand, or of asphyxia on 
 the other, will prove that the proportions of 
 the two gases are properly adjusted. Under 
 such circumstances the indicator may either
 
 The Administration. 51 
 
 be kept at "6" or "7 for several breaths, 
 and then gradually turned to "8," "9," or 
 ,l 10," or it may be allowed to remain at "6" 
 or " 7 " till anaesthesia is fully and satisfactorily 
 established. 
 
 (/3) Should there be an unaltered colour, 
 associated either with slight phonation, hardly 
 perceptible breathing, a tendency to laughter, 
 or slight restless movements of the head, trunk, 
 or extremities, the oxygen indicator should be 
 turned back slightly ; for these symptoms in- 
 dicate that too much oxygen is being inhaled. 
 
 (y) Should the breathing be loudly snoring 
 in character, or the colour rather dusky, or 
 should slight general clonic movement of the 
 body, head, or extremities be evident, the 
 oxygen indicator must be moved on ; for such 
 symptoms indicate a deficiency oi oxygen. 
 
 In one or other of these three ways the 
 patient will pass into deep and satisfactory 
 anaesthesia characterised by certain definite 
 phenomena. I he experience; of recent years 
 has convinced me that in administering nitrous 
 oxide and oxygen we should endeavour to 
 obtain an anaesthesia similar in most of its 
 features to the best types of ether or chloroform 
 anaesthesia. If we aim at inducing a perfectly 
 sleep-like state in which the colour of the 
 features is absolutely unaltered or is even 
 heightened, and the breathing is so tnyiquil
 
 5 z The Administration. 
 
 that it is inaudible, we shall not only be liable 
 to meet with excitement, but the anaesthesia 
 will, at all events in many cases, be less pro- 
 found than is desirable. Moreover, it is not an 
 easy matter, when the breathing" is inaudible, 
 to estimate the depth of anaesthesia. We 
 should therefore, I think, endeavour to bring- 
 about an anaesthesia characterised by softly 
 snoring breathing, a good pulse, a colour as 
 near the normal as possible, an insensitive 
 ocular conjunctiva, relaxed eyelids, a fixed 
 condition of the globes, and the absence of 
 muscular rigidity in the extremities. 
 
 Sometimes, and especially after a phase of 
 rapid breathing, or when a good deal of oxygen 
 has been given, the respiration may come 
 almost or completely to a standstill without 
 there being the slightest need for alarm. The 
 apnteic state is associated with a good pulse 
 and colour, ami will quicklv pass off when the 
 proportion of oxygen is reduced. 
 
 Ihe pulse is always as quick as, or quicker 
 tb.au it was immediatelv before the administra- 
 tion. In most cases the initial acceleration 
 from nervousness graduallv increases to a 
 maximum, and then declines somewhat, though 
 it never falls below its initial acceleration rate, 
 I am unable to agree with Hillischer's observa- 
 tion that the pulse-rate sinks to normal during 
 aniesthesia. l)r. Oliver"' observed, in us ins/
 
 The Administration. 53 
 
 his arteriometer, that the pulse calibre was not 
 reduced as in the case of pure nitrous oxide. 
 The small, feeble, and exceedingly rapid pulse 
 which not unfrequently may be felt at the acme 
 of an ordinary nitrous oxide inhalation, is not 
 met with when oxygen is present with the 
 nitrous oxide in sufficient quantities. I have 
 never, in fact, come across any indications of 
 circulatory failure during the administration of 
 the mixed gases. The tongue and adjacent 
 structures are less engorged than when nitrous 
 oxide is administered free from oxygen. 
 
 The eyes are generally closed throughout. 
 Some patients, however, prefer to keep them 
 open when the inhalation begins, but as it 
 proceeds the globes gradually cease to fix 
 themselves on surrounding objects, and the lids 
 become approximated, During the first minute 
 or so of the inhalation any attempt on the part 
 of the administrator to raise the upper lid will 
 be resisted by the patient. But after the first 
 minute the lid will gradually relax ; and when 
 it can be raised without any resistance, and 
 the conjunctiva can be touched without reflex 
 response, it may generally be assumed that 
 sufficient ana-sthesia is present. Sometimes 
 fine oscillatory movements of the globes may 
 be seen on raising the upper lids. The pupils 
 are generally of medium size or moderately 
 dilated. There is a striking contrast between 
 the closed lids of this form of anaesthesia and
 
 54 The Administration. 
 
 the open and turned-up eyes so often seen in 
 ordinary nitrous oxide narcosis. 
 
 Amongst the numerous points to which 
 attention must be paid in conducting the ad- 
 ministration, there is one which is of consider- 
 able importance. It is that the anaesthetist 
 must allow for what may be termed the 
 delayed effects of admitting more or less 
 oxygen. For example, let us suppose that 
 slight phonation occurs when the indicator 
 points to " /." By turning it to "3" or "4" 
 the phonation will in the course of a few 
 moments subside. But if the indicator be 
 kept at "3" or "4" till the patient is perfectly 
 quiet, the anaesthetist will probably have gone 
 too far in the asphyxial direction. He should 
 turn to "3" or "4" for a few breaths only 
 and return to "5," "6" or '' 7 " before the 
 phonation has ceased. In other words, he 
 must bear in mind that a little interval must 
 necessarily elapse before the effects of an 
 increase or decrease in oxygen admission will 
 become manifest. 
 
 As regards the length of inhalation which 
 is necessary to produce the typical phenomena 
 of the anaesthesia, I have found that it is, on 
 the average, jio seconds, i.e., nearly twice the 
 length of the average nitrous oxide inhalation. 
 The juncture at which the administration 
 should be terminated must, however, depend
 
 The Administration. 55 
 
 upon the circumstances of each case, such, 
 for example, as the susceptibility or insus- 
 ceptibility which the patient has displayed, 
 the nature of the proposed operation, and the 
 length of time that has elapsed since food 
 was taken. 
 
 The quantity of the mixture required to 
 produce anaesthesia will likewise vary con- 
 siderably, being dependent upon the propor- 
 tion of oxygen employed, the depth and rate 
 of respiration, the length of inhalation, the 
 type of patient, and other factors.
 
 56 
 
 CHAPTER V. 
 
 THE PATIENT. 
 
 In studying the effects produced in the 
 human subject by nitrous oxide and oxygen, 
 one of the first facts which becomes apparent is 
 that, although the constitution of the mixture, 
 the method of administration, and other sur- 
 rounding circumstances may remain the same, 
 different individuals display very different phe- 
 nomena. To say, however, that every case 
 has its own special peculiarities is hardly 
 correct. By careful observation it becomes 
 possible to group cases together into classes, 
 and to say that patients of this or that class will 
 display this or that set of symptoms. We are 
 in this way led to speak of different types of 
 patients. It is true that our knowledge of this 
 interesting aspect of the subject is still very 
 meagre ; but it is rapidly increasing. Success 
 in administering anaesthetics is largely depen- 
 dent upon the power the administrator possesses 
 of correctly foretelling what effects this or that 
 method will produce in the patient before him ;
 
 The Patient. 57 
 
 and it is this kind of knowledge which is 
 essential in deciding - upon the particular lines of 
 treatment which should be adopted in anaes- 
 thetising patients by the method now under 
 consideration. 
 
 In the preceding Chapter we discussed the 
 plan which should be followed in dealing with 
 those types of subjects most commonly met 
 with. We have now to consider what modi- 
 fications in that plan are advisable when 
 anaesthetising patients of other types. 
 
 Sex and age. — In anaesthetising small 
 children, more oxygen than usual must be 
 admitted. Should crying take place, the 
 administration should be commenced with the 
 indicator at " 8 " "9 " or " 10 " ; for the crying 
 tends to introduce an asphyxial element. I 
 have anaesthetised two or three children of three 
 years of age, by means of the mixture, but with 
 moderate success only, the anaesthesia being 
 very transient in such small subjects. In older 
 children the indicator may usually be placed at 
 " 3 " or " 4 " to commence with, and moved on 
 rather more quickly than usual to " 5," " 6," 
 etc. By the time " 10" is reached, the 
 breathing will probably have become so tran- 
 quil that some doubt as to the presence of 
 anaesthesia may be felt ; the indicator should 
 therefore now be turned back to " 5," "4 " or 
 even "3," when snoring will be certain to com-
 
 5$ The Patient. 
 
 mence. In this way a more satisfactory anaes- 
 thesia may be induced than if the face-piece 
 be removed during the inaudible breathing. 
 
 Taken as a class, women are better subjects 
 than men. They are more tolerant of con- 
 siderable proportions of oxygen, they are more 
 susceptible to the mixture, and, by reason of 
 their being less muscular, they are less prone to 
 inconvenient rigidity and movement. Middle- 
 aged women, with the rarest exceptions, are 
 always good subjects. I have, for example, 
 notes of several cases in which 60-90 seconds' 
 anaesthesia resulted after an ordinary inhalation 
 cf the mixed gases. 
 
 Old persons of both sexes are always very 
 favourably affected by the mixture. I have 
 anaesthetised, by its means, several patients 
 over 80 years of age. The absence of that 
 temporary respiratory embarrassment which is 
 so often induced by nitrous oxide free from 
 oxygen, and which, in the case of elderly 
 persons with rigid chests, cannot be regarded 
 as free from risk, is a very distinct gain. 
 
 General condition. — The better the patient's 
 state of health the more anaesthetic will he 
 require ; and vice versa. The proportions of 
 oxwen in the mixture, moreover, should be 
 rather smaller in the case of a perfectly healthy 
 subject than in that of a debilitated individual. 
 An exuberance of health and spirits is not
 
 The Patient. 59 
 
 always conducive to the most tranquil form of 
 anaesthesia. It may be said, in fact, that 
 patients of a weakly constitution, and those 
 who have recently been suffering from some 
 depressing malady, more often approach our 
 ideal standard of anaesthesia than patients of 
 opposite types. 
 
 Physique. — Other things being equal, the 
 more powerfully built the patient the greater 
 will be the quantity of the mixture required. 
 Men of an athletic physique, who have led 
 out-door lives, and who are in a state of perfect 
 health, often give slight trouble by becoming 
 rigid during the administration and operation. 
 Speaking in general terms, one may say that 
 rather smaller proportions of oxygen should be 
 used in the case of men than of women. Thus 
 it is best, as a rule, to start the administration 
 with the indicator at " i " and to very gradually 
 move it onwards. If oxygen be admitted at 
 the same rate as in anaesthetising; women, a 
 long inhalation will be necessary before good 
 anaesthesia is established ; and in attaining this 
 anaesthesia excitement will be liable to arise. 
 Men of slim build and rather weakly constitu- 
 tion may be treated in precisely the same wax- 
 as women. Very stout subjects, and especially 
 those with thick, short necks, or double chins, 
 tend to become; unusually stertorous. In such 
 cases the respiratory functions are always
 
 6o The Patient. 
 
 somewhat impaired, so that, even though the 
 patient may be tall and powerfully built, it is 
 best to proceed in the customary manner and 
 not to diminish the usual proportions of 
 oxygen. Very stout elderly women, with 
 feeble heart action, and possibly bronchial 
 symptoms, are remarkably good subjects for 
 nitrous oxide and oxygen administered in this 
 way. 
 
 The presence of a beard or moustache. — 
 When the hair is so distributed about the lips 
 and chin that even a small quantity necessarily 
 intervenes between the cushion of the face- 
 piece and the skin, allowance must be made 
 for the unavoidable ingress of a small propor- 
 tion of air with the mixture. All one can do is 
 to obtain as accurate a coaptation as possible, 
 by moistening the beard : to administer a 
 few breaths of pure nitrous oxide at first ; 
 and then very gradually to turn to " r," "2," 
 and so on. In this way I have been able to 
 obtain very good results. In many cases the 
 long inhalation which has resulted from the 
 unavoidable admission of small proportions of 
 air, has led to remarkably long anaesthesia. It 
 is impossible, however, in these cases, to be as 
 sure of one's results as in others. 
 
 Temperament.— Other factors remaining the 
 same, the best subjects for this as for other 
 anaesthetics are patients with placid, equable
 
 The Patient. 61 
 
 temperaments. Highly excitable and emo- 
 tional persons are liable to give slight trouble. 
 They sometimes voluntarily hold the breath, 
 or scream, before the anaesthetic is actually 
 breathed. They often, moreover, require 
 considerable quantities of the mixed gases 
 before the conjunctival reflex vanishes. In 
 many cases, indeed, this reflex will not dis- 
 appear, and the anaesthetist has to judge by 
 other signs that his patient is ready for the 
 operation. 
 
 Highly neurotic persons usually display a 
 shorter available anaesthesia than others. 
 Thin, pale, dark-complexioned young women, 
 of nervous temperament aire particularly liable 
 to prove difficult of management. With 
 nitrous oxide alone the full effects of the 
 gas are produced in a few respirations; the 
 asphyxial element is conspicuously present ; 
 and the resulting anaesthesia is disturbed and 
 brief. Much better results may be obtained, 
 however, with the mixture if the administra- 
 tion be conducted properly. Oxygen should 
 be rather sparingly admitted at first ; it should 
 then be somewhat more freely given ; and a 
 long inhalation secured. With regard to 
 hysterical women, we may say that, although 
 one cannot always depend upon obtaining 
 perfect results, such patients are, as a rule, 
 remarkably good subjects for the mixture,
 
 62 The Patient. 
 
 provided that oxygen be not too freely ad- 
 mitted. When such subjects are anaesthe- 
 tised by nitrous oxide alone, the anaesthesia 
 is so short that during recovery nio-htmare- 
 dreams and other distressing sensations are 
 likely to arise, and to induce screaming and 
 emotional attacks. The anaesthesia being 
 deeper, when the mixture is used, the result- 
 ing unconsciousness is quieter and longer, and 
 the recovery is usually unattended by any 
 emotional disturbances. The difference be- 
 tween the two methods of anaesthetising dental 
 patients has been very marked during the 
 course of the work I have done at the 
 Dental Hospital. I find that with nitrous 
 oxide and oxygen, patients rarely make any 
 sound at all, either during or after the ad- 
 ministration; whereas with nitrous oxide alone, 
 phonation is exceedingly common. 
 
 Complexion - Colour. — Plethoric, florid 
 patients are more liable than anaemic looking 
 persons to evince some duskiness during the 
 inhalation. Of all subjects, however, those of 
 a congested, bloated aspect are the most prone 
 to become dusky in appearance. It is not 
 advisable to be guided entirely by the patient's 
 colour in deciding whether more or less oxygen 
 should be given ; for if this course be adopted 
 in the case of patients who quickly and readily 
 show slight duskiness, but who are naturally
 
 The Patient. 63 
 
 excitable, imperfect anaesthesia from too much 
 oxygen may arise. In most cases it is possible 
 to retain the patient's normal colour throughout 
 the administration. Curiously enough, I have 
 notes of one or two cases, in which no obvious 
 alteration in colour occurred even though, as 
 was obvious from the presence of "mild 
 oscillation," the oxygen of the mixture was 
 considerably reduced. These cases are very 
 exceptional. Should the patient be pale from 
 nervous apprehension, the pallor will become 
 replaced by the natural colour as the inhala- 
 tion proceeds. Generally speaking, anaemic 
 subjects are very tolerant of oxygen, and in 
 their case this gas should be admitted more 
 freely than usual, the indicator being placed 
 at "3" or "4" at the beginning of the 
 administration . 
 
 Alcoholic indulgence. — Alcoholic subjects 
 generally do well with rather less oxygen than 
 usual, and the administration should be as 
 prolonged as is considered advisable, in order 
 to produce as deep an anaesthesia as possible. 
 As with other anaesthetics, delay in producing 
 anaesthesia is liable to arise, and the anaesthetic 
 state is often short and imperfect in character. 
 Movements of the head, arms, or legs are not 
 uncommon during the inhalation, so that care 
 should be taken not to give more! oxygen than 
 is needed to avoid asphyxial phenomena. In
 
 64 The Patient. 
 
 some cases the hands of the patients will clutch 
 the operator's arm during the operation, even 
 in the complete absence of consciousness. 
 Reflex phonation during the operation is also 
 not uncommon. 
 
 The excessive use of tobacco and other 
 narcotics. — I have found that patients who 
 smoke inordinately are not the best subjects 
 for nitrous oxide, even when given with 
 oxygen. They are inclined to movement, 
 hesitating or suspended breathing, and rigid- 
 ity, during the inhalation, and to a short 
 anaesthesia afterwards. All one can say is 
 that one can obtain, by means of the mixture, 
 a better result than with nitrous oxide alone ; 
 but this is all. Patients who habitually take 
 chloral or morphine also become comparatively 
 insusceptible to this as to other anaesthetics. 
 I have only once met with a temporary 
 maniacal seizure after nitrous oxide and oxygen, 
 and this was in the case of a young man who, 
 for six consecutive nights, had taken sleeping 
 draughts of chloral and of opium. 
 
 Affections of the respiratory system. — 
 Should any affection of the respiratory system 
 exist, care must be taken to allow for this, so 
 to speak, in conducting the administration, 
 otherwise asphyxial phenomena similar to 
 those met with when nitrous oxide is ad- 
 ministered in the customary manner, will be 
 liable to arise.
 
 The Patient. 65 
 
 If the air- way be partly obstructed by large 
 tonsils, adenoid growths, or other conditions ; 
 if the patient be the subject of chronic bron- 
 chitis, emphysema, phthisis, or other allied 
 diseases ; or if breathlessness from some 
 cardiac affection be present ; more oxygen 
 than usual must be given in order to neu- 
 tralise, as it were, the unusual asphyxial ele- 
 ment in the case. If this be done, nitrous 
 oxide anaesthesia may be safely induced in 
 nearly every case. 
 
 There are, however, a few highly exceptional 
 conditions in which some other form of anaes- 
 thesia is perhaps preferable. I refer particularly 
 to patients suffering from such dyspnoea that 
 no tightly-fitting mask can be applied — patients, 
 for example, who are the subjects of aneurysmal 
 or other pressure upon the trachea, very ad- 
 vanced phthisis, hydrothorax, and other grave 
 respiratory conditions. Putting such excep- 
 tional cases on one side, we may safely 
 administer nitrous oxide and oxygen to all 
 other patients. 
 
 Affections of the circulatory system. — It is 
 well known that patients with diseases of the 
 heart are good subjects for anaesthetics, provid- 
 ed that care be taken in selecting appropriate 
 methods. 
 
 I have administered nitrous oxide and 
 oxygen to patients with all the commoner 
 5
 
 66 The Patient. 
 
 forms of morbus cordis. Amongst these have 
 been three cases of aortic regurgitation, one 
 of advanced mitral and aortic disease, and 
 one of congenital valvular disease (? pulmo- 
 nary). In all of these cases excellent results 
 were obtained, and no anxiety was experienced. 
 Although nitrous oxide, as ordinarily adminis- 
 tered, is generally regarded as safe even in 
 advanced heart disease, I must confess that 
 I prefer not to adopt the customary plan of 
 administration in such subjects. The case is 
 quite different when nitrous oxide is given 
 with oxygen, for the temporary impairment of 
 respiration, with its consequent temporary 
 general venous engorgement, is prevented, so 
 that no undue strain is thrown upon the 
 right side of the heart. I have notes of an 
 interesting case which occurred at the Dental 
 Hospital, which is perhaps worth quoting. 
 The patient was a pale, thin, breathless man, 
 who had been an in-patient at Charing Cross 
 Hospital with oedema of the legs and cardiac 
 symptoms following rheumatic fever. He was 
 stated to have double aortic and mitral disease. 
 The heart's action was very tumultuous and 
 irregular. Nitrous oxide, free from oxygen, 
 was administered to him by a skilled anaes- 
 thetist on two occasions. On one of these 
 his pupils became enormously dilated, his 
 breathing very difficult, and his conjunctiva
 
 The Patient. 67 
 
 insensitive. His appearance was so alarming- 
 that no operation was performed. The 
 tongue was drawn forwards, and gradually 
 the threatening symptoms vanished. I sub- 
 sequently administered nitrous oxide and 
 oxygen to this patient. The pupils never 
 became widely dilated, and no trouble what- 
 ever occurred. In the case of a lad with 
 aortic regurgitation, who was pale, probably 
 from fright, before the administration, the 
 pulse markedly improved as the inhalation 
 proceeded, and the pallor lessened ; during - 
 the operation the normal florid colour was 
 completely restored. I have observed exactly 
 the same train of symptoms in a patient who, 
 at the time of the administration, had an ex- 
 ceedingly feeble pulse, and was pale from 
 shock produced by fruitless attempts to ex- 
 tract a tooth without an anaesthetic. One 
 patient to whom I administered the mixture 
 was the subject of a large intra - thoracic 
 aneurysm ; no bad effects followed. In 
 elderly persons with atheromatous vessels, it 
 is probably better to administer nitrous oxide 
 and oxygen than nitrous oxide alone ; but 
 the present state of our knowledge concern- 
 ing the differences in arterial tension in the 
 two cases prevents any positive statement 
 being made. 
 
 Affections of the nervous system. —I have
 
 68 The Patient. 
 
 anaesthetised numerous epileptics, and have 
 not vet met with a case in which an epileptic 
 attack has arisen during or immediately after 
 the inhalation. I have, however, had experi- 
 ence of one case in which a well - marked 
 seizure took place during" the administration 
 of pure nitrous oxide; but as the attack came 
 on very early in the administration it would 
 be wrong, I think, to assume that the absence 
 of oxygen had anv influence in its causation. 
 
 Pregnancy. - Nitrous oxide and oxygen 
 may be safely given to patients during the 
 latter months of pregnancy. Although nitrous 
 oxide, free from oxygen, is generally regarded 
 as admissible, it certainly seems to me that 
 it is wiser to adopt a non - asphyxiating 
 method in these cases. I have administered 
 nitrous oxide and oxygen, for a dental opera- 
 tion, within a week of the expected confine- 
 ment, and without any difficulty or subsequent 
 trouble arising. This plan of obtaining anaes- 
 thesia, indeed, is of great value in such cases, 
 for on the one hand we are able to avoid 
 the asphyxial accompaniments of an ordinary 
 nitrous oxide inhalation, and, on the other, 
 the possible after-vomiting of ether or chloro- 
 form narcosis.
 
 69 
 
 CHAPTER VI. 
 THE ANAESTHESIA. 
 
 The anaesthesia which is available for a 
 dental operation commences at the moment 
 the face-piece is removed, and should be re- 
 garded as terminating at the first indications 
 of returning semi-consciousness. Nothing has 
 contributed more to the unfavourable opinions 
 held by the public concerning " laughing gas," 
 than the practice of continuing the operation 
 whilst the patient is emerging, or after he 
 has emerged from deep anaesthesia. With pure 
 nitrous oxide the available unconsciousness is 
 comparatively short, and the transitional zones 
 between deep anaesthesia, semi-anaesthesia, 
 and normal consciousness are so narrow that 
 errors of judgment as to whether or not the 
 patient is capable of feeling pain at a given 
 moment are co a certain extent excusable. 
 But with nitrous oxide and oxygen the avail- 
 able ana-sthesia is distinctly longer, and the 
 transitional zones are distinctly broader, so that 
 operations which do not admit of being per-
 
 7° The Anasthesia. 
 
 fectly painlessly performed under nitrous oxide 
 as customarily administered, may be conducted 
 with an absolute freedom from pain and dis- 
 comfort under nitrous oxide and oxygen. 
 
 Immediately the anaesthetist has removed 
 the face-piece he should direct his attention to 
 supporting the patient's lower jaw, or steady- 
 ing the head, according to the nature of the 
 operation. He should at the same time keep 
 a sharp look-out for teeth or fragments of 
 teeth falling or shooting backwards towards 
 the fauces. 
 
 It is generally customary for lower teeth to 
 be removed before upper. If both sides of 
 the mouth are to be operated upon, and if the 
 order of events is a matter of indifference to 
 the surgeon and to his patient, it is better for 
 the left side to be first dealt with, for it is 
 easier to introduce the Mason's gag, should 
 one be required, from this, i.e., the side upon 
 which the anaesthetist stands, than from the 
 other. 
 
 The duration of the available anaesthesia 
 varies somewhat in different cases. The 
 average duration is about 44 seconds. Other 
 things being equal, the longer the inhalation, 
 the longer will be the resulting anaesthesia. 
 On many occasions, for example, I have con- 
 tinuously administered the mixed gases for 
 three minutes, and have thus been able to
 
 The Anesthesia. 71 
 
 secure an available anaesthesia of 50, 60, or 
 even yo seconds. But although the duration 
 of the inhalation has a very marked influence 
 in determining the length of the subsequent 
 unconsciousness, there are numerous other 
 factors. The type of subject occupies a pro- 
 minent position amongst these. Children, 
 excitable, neurotic patients, alcoholics, and 
 inveterate smokers, usually remain a shorter 
 time than usual under the influence of the 
 anaesthetic. On the other hand, anaemic, non- 
 excitable young men and young women, 
 middle - aged women of spare build, and 
 persons of both sexes who are in indifferent 
 health may remain tranquilly anaesthetised for 
 a comparatively long time. The amplitude 
 and rate of the breathing immediately after 
 the face-piece is removed is another factor. 
 Should the operation be such that the lower 
 jaw becomes depressed towards the sternum, 
 temporarily obstructed respiration may ensue, 
 and this, by preventing the exit of the 
 imprisoned anaesthetic, and the entrance of 
 atmospheric air, may lead to a prolongation 
 of the anaesthesia. The same result may 
 be brought about by sudden alterations in 
 the posture of the head, by which respira- 
 tion becomes mechanically obstructed. A 
 somewhat similar lengthening of the usual 
 anaesthesia is occasionally observed in stout,
 
 72 The Anesthesia. 
 
 wheezy subjects, and in those with chronic 
 bronchitis and emphysema ; imperfect expan- 
 sion of the bases of the lungs in these subjects 
 being" favourable to the retention of nitrous 
 oxide and oxygen for a longer time than usual. 
 
 Generally speaking, the patient remains 
 perfectly quiet and passive during the opera- 
 tion, provided that a proper limit be placed 
 upon the latter. At the first application of 
 the forceps or elevator, there is, however, in 
 many cases, a very slight and not incon- 
 venient reflex movement of the body. In 
 exceptional cases the movement is greater. 
 
 Should the colour have been slightly dusky 
 or paler than the normal when the face-piece 
 was removed, it will quickly become natural 
 when air is admitted. But if the operator 
 should depress the lower jaw, or in any other 
 way drive the tongue backwards, and thus 
 temporarily arrest the breathing, some duski- 
 ness will necessarily be produced. 
 
 Phonation at the begining of the operation 
 is hardly ever evoked. Should the patient 
 have been making phonated sounds during 
 the inhalation they may increase somewhat 
 during the operation ; but it is not uncommon 
 for the exact reverse of this to take place, 
 and for such sounds to be suddenly arrested 
 when the tooth is grasped by the forceps. 
 The available anaesthesia is far quieter and
 
 The Anesthesia. 73 
 
 of a better type than when nitrous oxide 
 has been given free from oxygen. In excep- 
 tional cases, and more particularly in children 
 and very nervous subjects, reflex phonation 
 may occur, but as is well known, such 
 phonation does not necessarily indicate the 
 perception of pain or, indeed, any knowledge 
 of the operation being performed. It is, 
 moreover, usually not remembered. 
 
 There are unfortunately no systematic rules 
 by which we can invariably tell when the 
 available anaesthesia has come to an end. 
 An endeavour should be made to so adjust 
 the administration and the operation that 
 after the latter has been completed there shall 
 still remain a slight reserve of anaesthesia. In 
 the event, however, of unexpected difficulties 
 arising in the operation, the anaesthetist is 
 rightly expected to give the signal for discon- 
 tinuing the extraction. It is by no means 
 always an easy matter to say whether, at a 
 particular juncture, the operation should be 
 terminated or continued. Nothing but 
 practical experience is of any avail in deciding 
 points of this kind. The general aspect of 
 the patient, the state of the eyes and pupils, 
 the character of any sounds that may be 
 uttered, and the nature of any movements that 
 may take place — these and other indications 
 have to be taken into careful consideration.
 
 74 The Anesthesia. 
 
 The most successful cases are those in which 
 the operation is performed at the acme of 
 anaesthesia, so that not only is there an absence 
 of all pain, but the patient experiences none 
 of those unpleasant sensations which are likely 
 to arise when an operation takes place during 
 semi-consciousness. 
 
 A re-application of the face-piece before 
 consciousness has been regained is not to be 
 recommended, except under certain circum- 
 stances, for such a plan of procedure is almost 
 certain to be followed by inconvenient if not 
 by objectionable asphyxial effects. If, how- 
 ever, the patient's head be nearly vertical, if 
 the attempt to remove a tooth or teeth should 
 have led to no haemorrhage, and if the face- 
 piece be applied before inconvenient movement 
 has taken place, there is but little objection to 
 the re-application. 
 
 Generally speaking it is better, in the event 
 of an extraction proving exceptionally difficult, 
 to desist from the operation, to allow the 
 patient to recover consciousness, to request 
 him to thoroughly wash out his mouth with 
 water, possibly containing a small quantity of 
 sulphate of zinc or some other astringent, and 
 to administer the mixture a second time. The 
 circumstances will in this way be far more 
 favourable than if a hurried attempt to extract 
 a difficult tooth be made during imperfect
 
 The Anesthesia. 75 
 
 anaesthesia. Re-administrations of the mixture 
 during" partial or complete anaesthesia, as well 
 as those conducted after an interval of several 
 minutes' consciousness, are liable to induce 
 nausea and vomiting, so that, whenever 
 possible, they should be avoided. 
 
 In concluding this chapter it may be men- 
 tioned that there is no better anaesthetic than 
 that under consideration for such operations as 
 drilling nto pulp cavities and opening up 
 the antrum. The absence of all jactitation 
 and irregular breathing renders such operations 
 far easier of performance than when nitrous 
 oxide is used free from oxygen.
 
 7 6 
 
 CHAPTER VII. 
 EXCEPTIONAL CASES. 
 
 Although the method of producing anaes- 
 thesia which has been described is the safest of 
 all those at present known to us, it is un- 
 doubtedly the most complex. From this it 
 follows that partial or complete failure to bring- 
 about typical nitrous oxide and oxygen anaes- 
 thesia will be liable to occur to everyone who 
 has not had much experience of the method. 
 As more and more experience is gained, it will 
 be found that difficulties and exceptional cases 
 are less and less frequently met with, and that 
 eventually such a state of proficiency will be 
 gained that cases displaying any unusual 
 departure from the normal type will be ex- 
 ceedingly rare. 
 
 Laughter, Singing and Articulate Shouting. 
 Inarticulate Phonation. — The occurrence of 
 such symptoms during the administration in- 
 dicates either that air is gaining admission 
 with the mixture, or that the oxygen proportion 
 is too high.
 
 Exceptional Cases. 77 
 
 Muscular phenomena during inhalation.— 
 
 These may comprise (1) Strictly voluntary 
 movements at the outset of the administration, 
 as, for example, putting up the hands with 
 the object of removing" the face - piece, etc. 
 Some patients imagine that by moving their 
 fingers, hands, or feet, at the beginning of the 
 administration, they may afford valuable assist- 
 ance to the anaesthetist by providing him with a 
 reliable sign that consciousness is present. Un- 
 fortunately, movements originally voluntary not 
 only tend to become automatic as consciousness 
 becomes lost, but they may even increase to 
 such a degree that the patient's whole body 
 shares in the movement. (2) Uncontrollable 
 nervous movements, also at the outset of the 
 administration, e.g., tremor of the legs, or 
 fidgety movements of arms, hands and fingers. 
 (3) Intoxication-movements, such as move- 
 ment of the head from side to side, stamping, 
 alternate thrusting out of the arms, etc. Such 
 movements as these are often associated with 
 laughter or shouting, and like the latter are due 
 to air or to too lari>"e a percentage of oxvsren in 
 the mixture. (4) Tonic spasm. Some degree 
 of tonic spasm is not uncommon, especially in 
 men, but extreme conditions, such as those to 
 which the terms opisthotonos and emprostho- 
 tonos have been applied are very rare;. Some- 
 times the tonic spasm affects the neck muscles,
 
 7& Exceptional Cases. 
 
 and the head gradually becomes turned to one 
 or other side. It is difficult to say what these 
 movements depend upon. In many cases they 
 occur when the percentage of oxygen is rather 
 less than usual, but this is not always so. 
 Indeed, if the patient be a vigorous, athletic 
 man, and too much oxygen be admitted with 
 the nitrous oxide, excitement will arise, and 
 marked rimditv mav be occasioned. It is on 
 such occasions as these that some degree of 
 respiratory spasm, from contraction of thoracic 
 and abdominal muscles, is prone to occur. In 
 this way a primary excess of oxygen may lead 
 to secondary cyanosis, or even to jactitation. 
 (5) Clonic spasm. Epileptiform twitchings 
 always indicate a diminution in the normal 
 oxygen supply. When the diminution is but 
 slight the clonus may be so mild that it may 
 escape detection. The most marked clonic 
 spasm (jactitation) is met with in children 
 when nitrous oxide free from oxygen is 
 rapidly inhaled. The epileptiform movements 
 may affect all parts of the body. Whenever 
 the anaesthetist detects any such movements 
 commencing during" the use of nitrous oxide 
 and oxygen, he should at once increase the 
 oxygen supply, and the movements will quickly 
 vanish, (6) Fine tremor of arms and legs 
 occurring during unconsciousness. This is 
 rare ; I have only seen it in three or four cases,
 
 Exceptional Cases. 79 
 
 and it came on when anaesthesia was fairly well 
 established. (7) Certain peculiar tonic move- 
 ments of deep anaesthesia. These are very 
 remarkable. After a long inhalation of the 
 gases, and when anaesthesia is well established, 
 as may be seen from the state of the eyes, 
 patients sometimes display peculiar movements 
 of the arms, legs, neck, and body. The arms 
 and legs will slowly move in a certain direction ; 
 the head will slowly turn to one side ; or the 
 whole body may begin to turn gradually in one 
 direction or another. The movements often 
 suo'eest a return of consciousness ; but this is 
 not so. When the face-piece is removed, a 
 long and perfectly tranquil anaesthesia follows. 
 The tonic movements differ from those referred 
 to in (4), for they come on after relaxation of 
 the muscular system has been produced. For 
 want of a better term I have called the con- 
 dition "secondary rigidity." 
 
 Cyanosis. — This always depends upon want 
 of oxygen. It may either be brought about by 
 the nitrous oxide bag becoming distended, so 
 that little or no oxygen passes from the oxygen 
 bag ; or it may arise from respiratory spasm 
 incidental to laughter, crying, or coughing ; or 
 the so-called "holding the breath" may take 
 place during or immediately after the inhalation 
 of the gases, and thus induce; cyanosis. This 
 " holding the breath " is a misnomer, for the
 
 8o Exceptional Cases. 
 
 patient is not conscious at the time. Certain 
 patients, especially men who are alcoholics, or 
 inveterate smokers, are prone to muscular 
 spasm, and when this spasm affects the chest 
 and abdomen, temporarily arrested breathing 
 necessarily occurs. There is no occasion for 
 alarm in these cases, as the breathing quickly 
 regains its normal rhythm. Cyanosis may also 
 occur in connection with morbid states, such 
 as enlarged tonsils, nasal polypi, post-nasal 
 adenoid growths, bronchitis, etc. And, lastly, 
 a faulty posture of the patient may induce it 
 (see remarks, p. 38). 
 
 Shallow, imperceptible, or arrested breath- 
 ing, associated with a good pulse and colour. 
 This condition, which should not alarm the 
 anaesthetist, is discussed on p. 52. 
 
 Very violent respiration at the outset of 
 the administration may generally be corrected 
 by requesting the patient to breathe more 
 quietly. Should consciousness have been lost 
 when this kind of respiration occurs, an 
 attempt may be made to check it by adminis- 
 tering rather less oxygen. Generally, how- 
 ever, the condition subsides spontaneously, 
 to be followed by " respiratory calm " (see 
 p. 52). In some instances, and especially when 
 patients are very nervous, the whole body may 
 move backwards and forwards synchronously 
 with the exaggerated breathing.
 
 Exceptional Cases. 81 
 
 Coughing, Crying. — Each of these is liable: 
 to be followed by asphyxial manifestations, 
 even if the mixture contain a considerable 
 percentage of oxygen. The former may be 
 dependent upon faulty posture, and is to be 
 treated by tilting the head forwards. 
 
 Retching or vomiting during the adminis- 
 tration. — Retching at the very outset of the 
 administration is to be treated as described on 
 p. 40. Should retching occur towards the end 
 of an administration, the inhalation should be 
 discontinued. Retching movements are most 
 likely to come on in protracted administrations, 
 and when a considerable percentage of oxygen 
 has been used. They are not necessarily 
 followed by vomiting, even though tood be 
 present in the stomach. When the patient 
 has abstained from food for several hours, both 
 retching and vomiting are very exceptional. 
 
 Micturition. — I have only known this to 
 occur twice in the 1 1 years during which I 
 have administered nitrous oxide and oxygen, 
 and in these cases no such accident would have 
 taken place had the usual precautions been 
 adopted. 
 
 Dangerous symptoms. — When sufficient 
 oxygen is administered with nitrous oxide 
 to prevent asphyxial complications there: is 
 every reason to believe that the ana-sthesia 
 produced is free from risk to life. A careful 
 6
 
 82 Exceptional Cases. 
 
 study of every fatality which has been recorded 
 in connection with the use of nitrous oxide gas 
 shows that in most, and probably in all cases 
 in which this agent has caused death, absence 
 of oxygen has been primarily responsible for 
 the occurrence. The same may also be said 
 of those reported cases in which alarming 
 symptoms have taken place during the 
 administration of nitrous oxide by the cus- 
 tomary method. The addition of oxygen to 
 nitrous oxide renders this agent respirable, 
 and robs it of its chief, if not its only risk. 
 There has not yet been recorded a single 
 fatality from nitrous oxide and oxygen, and 
 it is difficult to understand how one could 
 occur. Although I have now used nitrous 
 oxide with oxygen in several thousand cases, 
 I have only met with one case which has given 
 me the slightest anxiety, and the symptoms in 
 this case were only secondarily dependent upon 
 the anaesthesia. The patient was a strongly 
 built, nervous man, and good anaesthesia had 
 been induced ; but on altering the position of 
 the head in order to facilitate the removal of 
 an upper tooth, respiration temporarily ceased 
 and I had to pass my finger to the back of 
 the throat to separate the tongue from the 
 pharynx. With this exception I have not had 
 a single case which has given me any anxiety. 
 Highly exceptional cases. — It is only right
 
 Exceptional Cases. 83 
 
 to state, before concluding this chapter, that 
 although exceptional cases are, in most 
 instances, traceable either to some error in the 
 preparation of the patient, or to some fault in 
 the actual administration, they are not always 
 referable to such causes. Thus, there are 
 some patients who, whatever plans may be 
 adopted in administering the mixed gas, 
 cannot be made to pass into that tranquil state 
 of anaesthesia which it is desired to establish. 
 Under such unusual circumstances, the admin- 
 istrator must be satisfied with an anaesthesia 
 which approaches to, or is identical with that 
 ordinarily obtainable with nitrous oxide alone 
 in other words, he has to cut off the oxygen 
 supply and terminate the case with the usual 
 phenomena of nitrous oxide narcosis. Then 
 there are other patients who, although they 
 can be made to exhibit the usual signs of 
 nitrous oxide and oxygen anaesthesia, remain 
 such a short time under the influence of the 
 anaesthetic that one cannot help feeling dis- 
 satisfied with the result. With regard to such 
 cases as these, all one can say is that with 
 nitrous oxide alone they would certainly have 
 been even less satisfactory. Fortunately, they 
 are extremely exceptional, so that we need not 
 further consider them here.
 
 8+ 
 
 CHAPTER VIII. 
 
 A F TER-E F F E C T S . 
 
 A careful consideration of the circum- 
 stances under which after-effects are likely to 
 arise is of special importance ; for the one 
 weak point, if such it may be termed, in 
 nitrous oxide and oxygen anaesthesia, is that 
 this anaesthesia is associated with a somewhat 
 greater liability to unpleasant after-effects than 
 that resulting" from the administration of 
 nitrous oxide free from oxygen. 
 
 Provided, however, that the diet of the 
 patient has been properly regulated, and that 
 the inhalation has not been protracted, re- 
 covery from the effects of nitrous oxide 
 and oxygen usually takes place without the 
 slightest discomfort. I have notes of several 
 cases, indeed, in which the patient's condition 
 immediately alter the operation was more 
 satisfactory than after , a similar operation 
 previously performed under nitrous oxide free 
 from oxygen. 
 
 Thus, I have known a patient experience 
 severe headache after an ordinary administra-
 
 After-Effects. 85 
 
 tion of pure nitrous oxide, and to suffer trom 
 no such discomfort after the inhalation of this 
 gas with oxygen. In another of the cases 
 ot which I have notes the administration of 
 nitrous oxide per se had been followed by 
 numbness of the arms and legs, and blueness 
 of the hands, the symptoms persisting lor some- 
 time ; recovery was, however, perfect alter 
 nitrous oxide and oxygen. In another case, 
 that of a healthy-looking lad, the boy looked 
 much better after the administration of the 
 gas with oxygen than after an administra- 
 tion which had previously been conducted in 
 the ordinary way. In a fourth case, that of 
 a man ^^ years of age, who had on a previous 
 occasion experienced temporary loss of vision 
 after inhaling pure nitrous oxide, no such 
 symptoms were noted alter the use ol nitrous 
 oxide and oxygen. The infrequency ol dis- 
 tressing dreams when oxygen is used with 
 nitrous oxide is referred to below. 
 
 Should the inhalation have been some- 
 what protracted, recover)' will probably not 
 be quite so satisfactory as alter nitrous oxide 
 alone. On such occasions as these, the 
 patient may remain dazed and torpid for a 
 lew minutes, or he ma)' complain ol sleepi- 
 ness and wish to be left undisturbed. \\\ 
 some cases, giddiness, headache, or feelings 
 of numbness and tingling in the limbs may be
 
 86 After -Effects. 
 
 experienced. Nausea, with or without actual 
 retching movements, may also be induced 
 by prolonged administrations, and if there be 
 food present in the stomach, or if blood has 
 been swallowed, vomiting" may occur. 
 
 As already mentioned (p. 36), it is very 
 important, when a rather difficult dental 
 operation has to be performed, and as long" 
 an anaesthesia as possible is desired, to care- 
 fully regulate the patient's diet. If this be 
 done, inhalations lasting from two to three 
 minutes may generally be conducted without 
 any subsequent nausea occurring. 
 
 I find, on looking through my note books, 
 that, of the cases in which retching or 
 vomiting occurred after inhalation, there are 
 eleven in which the interval between the 
 taking of food and the administration is re- 
 corded. Of the retching cases, one was a 
 female of 43 — interval 2* hours ; another 
 was a female of 45 — interval 3 hours ; the 
 third was a male of 23- interval 3 hours. Of 
 the vomiting" cases, one was a female of 35 — 
 interval 4^ hours; one was a female of 13 
 interval 2] hours ; one was a female of to— 
 interval 2 1 hours. The rest of the vomiting 
 cases were males. Four were aged 15 — in- 
 tervals 2 f hours, 2f hours, 2 hours, and \ an 
 hour respectively ; one was aged .1 2— interval 
 3}- hours. Although these facts are very
 
 After -Effects. 87 
 
 meagre they bring into relief two interesting; 
 clinical points. One of these is that, of the 
 cases in which vomiting occurred the average 
 interval after food was 2], hours. The other 
 is that, of all subjects, boys from 10 16 are 
 most likely to suffer from vomiting after 
 nitrous oxide and oxygen. The lesson to be 
 learnt from these observations is that, if we 
 wish to avoid unpleasant after-effects, a long- 
 interval alter tood must be enforced, parti- 
 cularly in the case of young male subjects. 
 
 Transient feelings of faintness, pallor, and 
 feebleness of pulse are very rare, and are in 
 most, if not in all cases, associated with nausea 
 or impending vomiting. 
 
 A word may be said as to the treatment 
 of nausea, retching, and vomiting. Slight 
 nausea generally subsides spontaneously after 
 a few minutes. The patient should not be 
 permitted to lie back in the chair, otherwise 
 the swallowing of blood and saliva may favour 
 vomiting. He should bend forwards, keep 
 his eyes closed, and frequently wash out his 
 mouth. Should the feeling of nausea be 
 considerable, half a tumbler ol water so hot 
 that the finger can hardly be immersed in it, 
 should be given to the patient to drink. The 
 relief afforded by this simple measure is often 
 remarkable. If retching movements should 
 be present, they will usually quickly subside
 
 ss Aftev-Effects. 
 
 alter this treatment. Even if vomiting has 
 taken place, a draught of very hot water may 
 be given with advantage. Should pallor and 
 taintness attend these gastric disturbances, the 
 patient should be placed horizontally, pre- 
 ferably in the lateral posture. 
 
 Hysterical outbursts, crying, laughing, and 
 similar emotional disturbances are less common 
 than after nitrous oxide free from oxygen. 
 The one case in which I met with a temporary 
 maniacal seizure is referred to on p. 64. I 
 have also once met with curious rigidity of a 
 cataleptic character, after the administration. 
 The patient was a female aged 26. She 
 displayed the typical phenomena of nitrous 
 oxide and oxygen anaesthesia ; but after the 
 operation was over she sat for a few minutes, 
 with outstretched hands, open mouth, and 
 closed eyes. Her colour was unaltered. 
 
 Distressing dreams are less common after 
 nitrous oxide and oxygen than after nitrous 
 oxide alone. The cause of this difference is 
 difficult to define, but it is probably connected 
 with the deeper form of anaesthesia which 
 undoubtedly follows the inhalation of the 
 mixture. Generally speaking, either no dream 
 whatever is experienced, or the dream is of a 
 pleasant description.
 
 8 9 
 
 BIBLIOGRAPHY. 
 
 i. Lyman, Henry M. : "Artificial Anaesthesia and 
 
 Anaesthetics," 1883. 
 
 2. Rymer, Samuel Lee : " Remarks upon the Use of 
 
 Nitrous Oxide in Dental Operations": "The 
 Dental Review : A Quarterly Journal of Dental 
 Science," Jan., 1864. 
 
 3. Bert, Raul : " Comptes Rendus de la Societe de 
 
 Biologic," 1880, Tom. v., 6eme Ser., p. 40. 
 
 4. Bert, Paul : " Anesthesie par le protoxyde d'azote 
 
 employe sous tension" : " Comptes Rendus de la 
 Societe de Biologie," Tom. v., 6eme Ser., 1880, 
 p. 152. 
 
 5. Bert, Paul : " Du protoxyde d'azote sous tension ; son 
 
 action a doses anesthesiques ne s'etend pas sur 
 le systeme nerveux sympathique " : " Comptes 
 Rendus de la Societe de Biologie," 1880, Tom. 
 v., 6eme Ser., p. 233. 
 
 6. Bert, Paul : " Sur la possibility d'obtenir, a l'aide du 
 
 protoxyde d'azote, une insensibilite de longue 
 duree, et sur l'innocuite de cet anesthesique " : 
 " Comptes Rendus de l'Academie des Sciences,"' 
 1878, Tom. 87, p. 728. 
 
 7. Bert, Paul : " Anesthesie par le protoxyde d'azote " : 
 
 " Comptes Rendus de la Societe de Biologie," 
 
 Ser. 7, Tom. 1, Pt. 2, p. 19. 
 6. Bert, Paul: " De l'emploi du protoxyde d'azote" 
 
 dans les operations chirurgicalcs de longue 
 
 duree"' : " Lc Progres Medical," No. 9, Peb. 28, 
 
 i«8o, p. 161. 
 cj. Klikowitsch, Stanislaus : " Leber das Stickstoil" 
 
 oxydul als Ana.'stheticum bei Geburten " :
 
 go Bibliography. 
 
 " Archiv fur Gynackologie," 1881, Band xviii., 
 p. 81. 
 
 10. Winckel, F. : "A text-hook of Obstetrics" (Trans- 
 lated by Edgar), 1890, p. 187. 
 
 n. Martin, Claude: " De I'Anesthesie par le protoxyde 
 d'azote avec 011 sans tension," Lyons, 1883. 
 
 12. Hewitt, Frederic: "Anaesthetics and their Adminis- 
 
 tration," 1883, p. 120. 
 
 13. Bert, Paul : " Anesthesie prolongee obtenue par 
 
 le protoxyde d'azote a la pression normale " : 
 " Comptes Rendus de l'Academie des Sciences," 
 Tom. 96, 1883, p. 1271. 
 
 14. Hillischer, H. T. : " Ueber die allgemeine Yer- 
 
 vvendbarkeit der Lustgas-Sauerstoffnarkosen in 
 der Chirurgie " : (Paper read at the 59th meeting 
 of German Natural Philosophers and Physicians, 
 at Berlin, Sept. 21, 1886). 
 
 15. Hillischer, H. T. : " Ueber Lustgas und Lustgas- 
 
 Sauerstoff (Schlafgas) " : (Paper read before the 
 Royal Society of Physicians in Vienna, May 27, 
 1887). 
 
 16. Hillischer, H. T. : " Ueber die Yerwendung des 
 
 Stickoxydul - Sauerstoffgemenges zu Narkosen " : 
 (Paper read at the Annual Meeting of the Central 
 Union of German Dentists in Berlin, 1887). 
 
 17. Hillischer, H. T. : " Neue Apparate fur Schlafgas" : 
 
 " Correspondenzblatt f. Zahnarzte," Oct., 1890. 
 
 18. Hillischer, H. T. : "Wie soil man mit Schlafgas 
 
 narkotisiren ? " : " Oesterr - ungar. Yierteljahres- 
 schrift fi'ir Zahnheilkunde," Oct., 1890. 
 
 19. Witzel, Adolph : " Deutsche Zahnheilkunde, in 
 
 Vortragen," Wien, 1889. 
 
 20. Wood, H. C. : " On the Action of Nitrous Oxide and 
 
 of the Mixture of Nitrous Oxide and Oxygen " : 
 " Dental Cosmos," May, 1893. 
 
 21. Hewitt, Frederic: " The anaesthetic effects of Nitrous 
 
 Oxide and Oxygen, when administered at ordi- 
 nary atmospheric pressures, with remarks on 800 
 cases": "Trans. Odont. Soc. Gt. Britain," June, 
 1892.
 
 Bibliography. 91 
 
 22. Hewitt, Frederic : "On the Anaesthesia produced by 
 
 the Administration of Mixtures of Nitrous Oxide 
 and Oxygen " : " Lancet/' April 27, 1889. 
 
 23. Hewitt, Frederic : "A new and portable apparatus 
 
 for the Administration of Oxygen with Nitrous 
 Oxide " : " Journ. Brit. Dental Association," 
 Oct. 15, 1892. 
 
 24. Hewitt, Frederic : " Further Observations on the 
 
 use of Oxygen with Nitrous Oxide": "Journ. 
 Brit. Dental Association," June, 1894. 
 
 25. Hewitt, Frederic : " On some essential points in 
 
 Administering Anaesthetics for Dental Operations ; 
 with special reference to the subject of Posture " : 
 "Journ. Brit. Dental Association," Oct., 1896. 
 
 26. Oliver, George : "Pulse-gauging," p. 83.
 
 CJ2 
 
 INDEX. 
 
 Adenoid growths of naso-pharynx, patients with, 65, 
 
 80. 
 Adjustment oe proportions in administering nitrous 
 
 oxide and oxygen, 50. 
 Administration, in ordinary or average cases, 42 ct scq. ; 
 
 duration of, 54. 
 Admission oe oxygen during administration, 45, 48, 
 
 49, 50, 54, 5^> 59, 6i, 65. 
 
 After-effects, 84 ct scq. 
 
 Age, influence of, 14, 57, 71. 
 
 Air, necessity for excluding, in administering nitrous 
 oxide and oxygen, 17, 47 ; mixed with nitrous 
 oxide in early cases, 4, 6 ; total exclusion of, 
 considered necessary, 6. 
 
 Air-cushion, use of, in obtaining proper posture, 39. 
 
 Air-way, obstructive affections of the, 65. 
 
 Alarming symptoms (see Dangerous symptoms). 
 
 Alcoholic subjects, 14, 63, 71, 80. 
 
 An.emic subjects, 63, 71. 
 
 Anaesthesia, available for dental operations, 69 ct scq. ; 
 characteristics of nitrous oxide and oxygen, 51 : 
 duration of, 58, 70, 83 ; termination of, 73. 
 
 Aneurysm, patients suffering from, 65, 67. 
 
 Antiseptics, application of, to regulating apparatus, 
 
 25- 
 
 Antrum, opening up the, 75. 
 
 Aortic disease, patients suffering from, 66, 67. 
 
 Apncea, physiological, 51, 52, 80. 
 
 Apparatus for administering nitrous oxide and oxygen : 
 Bert's, 9 ; Hillischer's, 13, 18; the author's earlier 
 forms, 15, 18 ; the author's present, 19, 23 ct scq. : 
 necessity for examining occasionally, 33.
 
 Index. 93 
 
 Appliances which should be in readiness, 37. 
 
 Arterial tension under nitrous oxide and oxygen, 9, 
 67. 
 
 Asphyxial phenomena, absence of when oxygen is 
 used, 8, 9, 11, 16, 50 ; in patients with respiratory 
 affections, 64 ; induced by nitrous oxide, 7, 48, 
 82; from too little oxygen, 48, 51; in alcoholic 
 subjects, 63 ; induced by coughing or crying, 81. 
 
 Atheromatous vessels, patients with, 67. 
 
 Athletic subjects, 59, 78. 
 
 Available anesthesia for dental operations, 69. 
 
 Average or ordinary cases, the administration in, 42 
 ct seq. 
 
 Bags for administering the gases, 23, 27, 28 ; fulness and 
 relative sizes of, during administration, 47. 
 
 Beards, patients with, 60. 
 
 Bert, early work of, in connection with use of oxygen, 
 7, 8, 9 ; his apparatus, 9 ; his experiments at ordin- 
 ary atmospheric pressures, 12 ; his method used by 
 Martin, 11. 
 
 Bladder, advisability of emptying, 36. 81. 
 
 Blood, Bert's views as to solubility of nitrous oxide in, 8. 
 
 Blood-pressure (see Arterial tension). 
 
 Blueness of the features (see Cyanosis). 
 
 Breathing, amplitude and rate of, 44, 71 ; at outset of 
 administration, 44, 47, 80 ; cessation of, associated 
 with good pulse, 52. So ; diaphragmatic, 37 : em- 
 barrassment of, 58 ; hardly perceptible, 51. 52,57, 
 80 ; of deep anaesthesia. 52 ; patients suffering from 
 difficulty of, 65 : provisions for free, 37 : restricted, 
 37,45 ; snoring, 51, 52, 57; temporarily obstructed, 
 71, 72, 82 ; violent, So. 
 
 Breathlessness, cardiac, 65. 
 
 Bronchial affections, patients with. 60, 65, 72. 
 
 Cardiac affections (sec Heart). 
 Cataleptic state after. inhalation, 88. 
 Characj eristics of nitrous oxide and oxygen anaesthesia, 
 5i-
 
 94 Index. 
 
 Children, suggestions for anaesthetising, 57, 71. 
 
 Chloral, patients addicted to, 64. 
 
 Circulatory system under nitrous oxide and oxygen, 
 g, 52, 67, 87 ; affections of, 65 (see also Heart). 
 
 Clonic muscular movements, 51, 78 (see also Epilep- 
 tiform movements). 
 
 Clothing, importance of loose, 37. 
 
 Clover's improvements in early apparatus for nitrous 
 oxide, 6. 
 
 Coaptation of face-piece, 45, 46. 
 
 Colour of features, 9, 11, 51, 52, 61, 62, 72. 
 
 Colton Dental Association, 5. 
 
 Coltox's administrations of nitrous oxide, 2, 5. 
 
 Combined stand and union for nitrous oxide and 
 oxygen cylinders, 26. 
 
 Complexion, 61, 62. 
 
 coxjuxctiyal reflex, 52, 53. 
 
 Coxtra-ixdicatioxs to nitrous oxide and oxygen, 14, 65. 
 
 Coughing, 79, 81. 
 
 Crying, 4. 57, 79, 81 ; as an after-effect, 88. 
 
 Cushion, use of inflated air, 39. 
 
 Cyanosis, ii, 14, 48, 78, 79 (see also Duskiness and 
 Livid ity). 
 
 Cylinders for nitrous oxide and oxygen, 24, 25, 26. 
 
 Dangerous symptoms, appliances for treatment of, 37 ; 
 
 occurrence of, 81. 
 Davy, discoverer of anaesthetic properties of nitrous 
 
 oxide, 1. 
 Da/ed feelixgs after inhalation, 85. 
 
 Delayed effects of admitting more or less oxygen, 54. 
 Diet, regulation of, 35, 36, 84, 86, 87. 
 Disturbixg influences during administration, 42. 
 Doderlein, 10. 
 Dreams, 88. 
 
 Drilling into pulp-cavities, 75. 
 
 Duration of inhalation, 54; of anaesthesia, ^S, 70, S^,. 
 Duskixess of the features, 48, 51, 62 (see also Lividity 
 
 and Cyanosis). 
 Dyspnoea, patients suffering from, 65.
 
 Index. 95 
 
 Early administration's of nitrous oxide, 2 et scq.\ of 
 
 nitrous oxide and oxygen, 8. 
 Elderly persons, 5$, 67. 
 Emergencies under nitrous oxide and oxygen, appliances 
 
 for treatment of, 37. 
 Emphysema, patients with, 65, 72. 
 Emprosthotonos, 77. 
 Epilepsy, patients suffering from, 14, 68. 
 Epileptiform movements, absence of, when oxygen 
 
 used with nitrous oxide, 16, 48; presence of when 
 
 oxygen supply diminished or cut off, 48 ; consequent 
 
 upon want of oxygen due to respiratory spasm, 78 
 
 (see also Muscular phenomena — clonic). 
 Evans's demonstration, 5 ; his apparatus for nitrous 
 
 oxide, 5. 
 
 Exceptional cases, 76 et seq. ; highly exceptional cases, 
 
 82. 
 Excitable subjects, 61. 
 Excitement, absence of, 50 ; in early nitrous oxide 
 
 administrations, 4 ; under nitrous oxide and oxygen, 
 
 11, 22, 48, 51. 
 Expiratory valve of regulating apparatus, 25, 32. 
 Extension of head upon the spine, objections to, 38. 
 Eyes and eyelids, state of, during anaesthesia, 52, 53. 
 
 Face-pieces, 24, 32 ; fitting of, 45, 46 ; re-application 
 of, 74. 
 
 Faintness, as an after-effect, 87. 
 
 Fitting of face-piece, 45, 46. 
 
 First administration of nitrous oxide, 2 ; of nitrous 
 oxide and oxygen, 9. 
 
 Food, regulations as to, 35, 36, 84, 86, 87. 
 
 Fulness and relative sizes of bags during administra- 
 tion, 47 
 
 Gasometer methods, 17, 21. 
 General condition of the patient, 58. 
 Giddiness as an after effect, 85. 
 
 Hair about face, patients with, ho. 
 Headache, as an after-effect, S4, 85.
 
 9 6 Index. 
 
 Head, adjustment of, 38. 
 
 Health, general state of, 58, 71. 
 
 Heart affections, patients with, 14, 60, 65. 
 
 Hillisciier, Dr., first to employ nitrous oxide and 
 oxygen in dentistry, 13; his apparatus, 13; his 
 method, 14 ; his views as to the pulse, 52 ; objec- 
 tions to bis apparatus, 18. 
 
 History of nitrous oxide, 1 ct scq. ; of nitrous oxide and 
 oxygen, 7 et scq. 
 
 " Holding the breath," 45, 79. 
 
 Hot water, in the treatment of after-nausea and 
 vomiting, 87. 
 
 Hydrothorax, patients suffering from, 65. 
 
 Hysteria as an after-effect, 88. 
 
 Hysterical subjects, 61. 
 
 Inhalation, length of, 54. 
 
 Insusceptibility to nitrous oxide and oxygen, 83. 
 
 Intermittent administrations of nitrous oxide and 
 
 air, 7. 
 Intoxication-movements, 77. 
 
 "Jactitation" (see Muscular phenomena [clonic) and 
 Epileptiform movements). 
 
 Keeping nitrous oxide and oxygen together, 23. 
 Kicking, 48. 
 Klikowitsch, 10. 
 
 Laboured breathing, 14. 
 
 Laughter, 4, 48, 51, 76, 79; as an after-effect, 88. 
 
 Length, of available anaesthesia, 58, 70, 83 ; of inhala- 
 tion, 54. 
 
 Liyidity of the features, 11, 48 (see also Duskiness and 
 Cyanosis). 
 
 Loose clothing, importance of, 37. 
 
 Lungs, diseases of, 14. 
 
 Mania, temporary, as an after-effect, 64, 88. 
 
 Martin, Dr., adminstrations of, 11. 
 
 Men, as subjects for nitrous oxide and oxygen, 58, 71.
 
 Index. 97 
 
 Micturition, 36, 81. 
 
 Morphine, patients addicted to, 64. 
 
 Mouth-props, 40. 
 
 Mouth-tubes for administration, disadvantages, of 47. 
 
 Movements (see Muscular phenomena). 
 
 Muscular phenomena, 52,77; clonic or epileptiform, 
 16, 48, 51, 78 ; in alcoholic subjects, 63 ; in habitual 
 smokers, 64 ; intoxication, 77 ; reflex, 72, 79 ; rest- 
 less, 51 ; tremulous, 77, 78 ; tonic, 52, 64, 77, 79 ; 
 uncontrollable nervous, 77 ; voluntary, 77. 
 
 Narcotics, habitual use of, 64. 
 
 Nausea, as an after-effect, 86 ; treatment of, 87. 
 
 Nervous and neurotic subjects, 61, 63, 71. 
 
 Nervous movements, 77. 
 
 Nervous system, diseases of the. 67. 
 
 Nitrogen, higher oxides of, produced when nitrous 
 
 oxide and oxygen kept together, 23. 
 Numbness of the extremities, as an after-effect. 85. 
 
 Obesity, 59, 71 . 
 
 Obstructed breathing during operation, 71. 
 
 Obstructive respiratory affections, 65, 80. 
 
 Old age, nitrous oxide and oxygen in, 58, 67. 
 
 Oliver, Dr., pulse observations by, 52. 
 
 Operation, the anaesthetist and the, 70, 73. 
 
 Operations, difficult, 74, 86. 
 
 Opisthotonos, 77. 
 
 Ordinary or average cases, the administration in, 42 et 
 
 scq. 
 Oxygen, admission of, during administration, 45, 48, 49, 
 
 50, 54, 58, 59, 61, 65; delayed effects of admitting 
 
 more or less, 54 ; percentage of (see Percentage) ; 
 
 symptoms due to too large a proportion of, 48 ; 
 
 symptoms due to too little, 48. 
 
 P.a.r.oR from nervousness, 63, 67; as an after-effect, 87. 
 Patient, the, 50 et seq. 
 Patients, different types of, 56. 
 
 Percentage of oxygen, in Bert's administrations, 8, 9, 
 10, 12; in Klikow ilsch's, WinckcTs, Dodetiein's, 
 
 7
 
 g8 Index. 
 
 and Zweifel's administrations, 10 ; in Martin's 
 administrations, 1 1 ; in Hillischer's administrations, 
 14 ; in Wood's experiments, 15 ; in the author's 
 administrations, 16, 17, 18 ; in gasometer cases, 21 ; 
 in the author's regulating apparatus, 32, 33, 45. 
 
 Phonation, 51, 62, 64, 72, 76. 
 
 Phthisis, pulmonary, 65. 
 
 Physiological apncea, 51, 52, 80. 
 
 Physique of patient, influence of, 59. 
 
 Posture, influence of, 38, 71, 80, 82. 
 
 Precautions (see Pveparations). 
 
 Pregnancy, nitrous oxide and oxygen in, 68. 
 
 Preparations necessary, 35 et seq. 
 
 Priestley, nitrous oxide discovered by, 1, 
 
 Prolonged administrations of nitrous oxide and oxygen, 
 12, 54, 84, 85, 86. 
 
 Proportions of oxygen (see Percentage of oxygen). 
 
 Props (see Mouth-pvops). 
 
 Pulmonary affections, patients with, 64. 
 
 Pulp-cavities, drilling into, 73. 
 
 Pulse, feeble, after inhalation, 87 ; under nitrous oxide 
 and oxygen, 52. 
 
 Pupils, state of, 53. 
 
 Quantity of mixture required to produce anaesthesia, 35. 
 
 Re- administrations, 74. 
 
 Re-application of face-piece, 74. 
 
 Recovery from nitrous oxide and oxygen anaesthesia, 
 
 62 (see also After-effects). 
 Reflex, conjunctival (see Conjunctival) ; movement 
 
 during operation, 72, 79. 
 Regulating apparatus, necessity for, in administering 
 
 nitrous oxide and oxygen, 13, 18, 22. 
 Regulating stopcock and mixing chamber, the 
 
 author's), 28 et seq. 
 Requirements for a regulating apparatus, 23. 
 Respiration, administration to patients with impaired, 
 
 59. 60, 64 (see also Breathing). 
 " Respiratory calm," 32, >o.
 
 Index. 99 
 
 Respiratory spasm, 78, 79, 80. 
 
 Retching and vomiting, as after-effects, 86, et seq. ; 
 
 treatment of, 87 
 Retching movements, caused by inserting mouth-prop, 
 
 40; occurring during inhalation, 81. 
 Rigidity, muscular, 52, 64, 77 ; of deep anaesthesia 
 
 (" secondary rigidity "), 79. 
 Rymer's administrations of nitrous oxide, 5. 
 
 Safety of nitrous oxide and oxygen, 12, 82. 
 
 " Schlafgas," 13. 
 
 " Secondary rigidity," 79. 
 
 Sensations of the patient, 46. 
 
 Sex, influence of, 57. 
 
 Shouting, 4, 48, 76. 
 
 Signs of nitrous oxide and oxygen anaesthesia, 51. 
 
 Singing, 76. 
 
 Sleep-like state, 51 (see also " Schlafgas "). 
 
 Sleepy feelings after inhalation, 85. 
 
 Smith's early administration of nitrous oxide, 4. 
 
 Snoring breathing, 51, 52, 57. 
 
 Spasm, clonic (see Clonic muscular movements, Epileptiform 
 
 movements, 'Arid Muscular phenomena) ; respiratory, 78, 
 
 79, 80 ; tonic (see Rigidity, and Muscular phenomena). 
 Stamping, 48. 
 
 Stand for nitrous oxide and oxygen cylinders, 26. 
 Stertor, absence of, when oxygen used, 16 ; obstructive 
 
 from too little oxygen, 48 ; moderate, 51 (see also 
 
 Snoring). 
 Stimulants before administration, 36. 
 Stopcock and mixing chamber (the author's) 28, et seq. 
 Stout subjects, 59, 71. 
 Struggling, 48. 
 Suffocative sensations, 46. 
 Supply of nitrous oxide and oxygen, 23, 26, 27. 
 
 Temperament, influence of, 60. 
 
 Tension, arterial, 9, 67. 
 
 Termination of administration, 54; of anaesthesia, 7 3. 
 
 Tight lacing, disadvantages of, 38.
 
 ioo Index. 
 
 Tobacco, excessive use of, 64, 71, 80. 
 
 Tonic spasm (see Rigidity). 
 
 Tonsils, enlarged, 65, 80. 
 
 Trachea, patients suffering from pressure upon, 65. 
 
 Treatment of emergencies under nitrous oxide and 
 
 oxygen, appliances for, 37 ; of nausea, retching, 
 
 and vomiting after inhalation, 87. 
 Tremor, 77, 78. 
 Types of patients, 56, 71. 
 Typical anaesthesia from nitrous oxide and oxygen, 51. 
 
 Valve, expiratory, of regulating apparatus, 25, 29; 
 
 inspiratory, of regulating apparatus. 29. 
 Valves of regulating apparatus, 24, 29, 31. 
 Violent breathing, 80 
 
 Vision, temporary loss of, as an after-effect, 85. 
 Voluntary muscular movements, 77. 
 Vomiting, occurring during the administration, 81 ; as 
 
 an after-effect, 86 et seq. ; treatment of, 87. 
 
 Wells, Horace, the first to use nitrous oxide in 
 surgery, 2. 
 
 WlNCKEL, IO. 
 
 Witzel, 14. 
 
 Women, as subjects for nitrous oxide and oxygen, 42, 
 
 58. 7i- 
 Wood, Dr. H. C, 15. 
 
 Zweifel, 10.
 
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