4o: 



NA TURE 



[August 15, 1907 



SKCTIOX I. 



PHYSIOLOGY. 



Opening Address by Augustus D. Waller, M.D., LL.D., 

 F.R.S., Pkesident of the Section. 



On the Action of Anaesthetics. 



The duly laid upon me by the Chair which I have the 

 honour to occupy to-day is in the first place to copy the 

 example of my predecessors by submitting to the Section 

 some distinct and definite contribution to the advance- 

 ment of science. 



And inasmuch as the subject has firmly held my atten- 

 tion during the last fifteen years, I am naturally led to 

 name .An.tslhesia as the title of my Presidential .Address 

 to the Section of Physiology. 



With due regard paid to the fact that the audience to 

 which the British .Association addresses itself is not prin- 

 cipally medical nor exclusively scientific, I shall deal with 

 the subject in a manner that may, I hope, justify my 

 opinion that it is a subject capable of being usefully con- 

 sidered by all educated minds. 



And surely, quite apart from its value as an illustra- 

 tion of the method of physiological inquiry, the subject is 

 one with which any educated man may well desire to 

 possess some rational acquaintance, since every one of us 

 may some day require the saving boon of ansesthesia. 



Most people have some idea of what is meant by an 

 aniEsthetic, and will recognise by name at least one 

 anxsthetic drug — chloroform. It is even probable that the 

 first stranger whom you should meet in the street might 

 also name ether and " gas " as being anesthetics. And 

 pretty surely he would also know that the use of an 

 anassthetic is to abolish pain. But if you were to tell 

 him that a plant can be anaesthetised — that seeds can be 

 chloroformed or etherised — he might very possibly express 

 surprise. 



The popular notion of an anajsthetic, in conformity with 

 the literal meaning of the word, is that it is something 

 that abolishes sensibility and takes away pain. But how, 

 then, can a plant be chloroformed? Does that mean that 

 a plant is sensitive and can feel pain as we do? Well, 

 probably not ; nevertheless it is very certain that a plant 

 can be anssthctised, and when you have properly appre- 

 ciated what this means I think you will admit that our 

 notions of vital processes and of their ancesthesia by ether, 

 or by chloroform, or by a host of other reagents have 

 been considerably widened. For we shall then have 

 realised that the state of a person or of an animal rendered 

 insensitive of pain by an ana'sthetic is a particular instance 

 of the general principle that all protoplasm — vegetable as 

 well as animal — is liable to be immobilised — put to sleep — 

 more or less completely — temporarily or permanently — bv 

 the action of substances which we therefore designate as 

 anaesthetics or narcotics. A volatile narcotic, like ether 

 or chloroform, gets to the living cells of a plant by direct 

 diffusion ; in the case of ourselves and of the higher 

 animals it gets to the living cells by the channels of 

 respiration and of circulation. The molecule of chloro- 

 form (or of ether) is drawn into the lungs with the inspired 

 air, passes from the pulmonary air to the pulmonary blood, 

 combines with its corpuscles, is thus carried first to the 

 heart and then distributed with the blood to all parts of 

 the body ; in the capillaries the molecule of chloroform 

 parts company from hiemoglobin, passes from the blood 

 to the tissues and tissue fluids, and enters into combin- 

 ation with the living cells which it immobilises more or 

 less profoundly, temporarily or permanently. The various 

 kinds of living cells that constitute our organs are un- 

 equally susceptible as regards the immobilising effect of 

 this general invasion of the system by the narcotising 

 molecules. 



Of all the cells of the body, the most labile, and there- 

 fore the first immobilised, are the master cells of the bodv 

 — the cells of the grey matter of the brain, that is, the 

 seat of sensation and the organ of voluntary motion. The 

 most stable, and therefore the last immobilised, are the 

 executive cells of the body that constitute muscle and 

 nerve. The order of lability from greatest to least is as 

 follows : — Brain ; spinal bulb and cord ; terminal nerve 

 cells, cardiac muscle ; skeletal muscle ; nerve fibres. And 



NO. 1972, VOL. 76] 



while all living cells and tissues of the body are subject 

 to the immobilising action of narcotic substances, their 

 individual differences of susceptibility are such that, 

 whereas one part of chloroform in 5000 ol blood is sufficient 

 to immobilise cortical nerve cells, a nerve fibre requires 

 a more than tenfold effective mass of chloroform before 

 exhibiting 'any falling-off of its normal excitability. 



Let us now briefly consider what happens when a patient 

 is anaisthetiscd by, say, chloroform in the usual manner 

 by inhalation of an unknown mass of vapour. The inhaled 

 vapour, more or less diluted in air, diffuses into, and is 

 distributed to, the entire body by the circulating blood. 

 The lymph bath that surrounds and permeates all the 

 tissues and cells of the body becomes a weak solution 

 of chloroform in water, and gradually within that weak 

 chloroform atmosphere the most labile parts fall under 

 the immobilising effect of the anivsthetic, first the organ 

 of conscious sensation and movement — the cortical grey 

 matter of the brain — then the organ of unconscious re- 

 actions, the medullary grey matter of the spinal bulb and 

 cord. So that the order in which the effects unfold them- 

 selves are (after a brief stage of excitement or mobilisa- 

 tion) first a suppression of sensation and voluntary move- 

 ment, then a suppression of reflex and automatic move- 

 ments, inclusive ol the movements of respiration. Finally 

 — and if this finally is reached the immobilisation can no 

 longer be recovered from — the heart stops beating. The 

 patient is dead. 



From life to death by the way of anjesthesia there are 

 three principal finger-posts dividing the journey into three 

 stages. Of these three finger-posts two are to be care- 

 fully watched for ; the third should never be sighted. 



During the first stage of anaesthesia — commencing, it 

 may be, by some amount of preliminary agitation — sensa- 

 tion and voluntary motion become suppressed, while refle.x 

 and automatic movements are preserved. The finger-post 

 between this first stage and the next is quite clear : if 

 when the conjunctiva is touched the eye winks the 

 anxsthesia is "light"; if the eye does not wink the 

 ana'sthesia is "deep." 



During the second stage of anafslhesia not only voluntary 

 but also reflex movements (of which the conjunctival reflex 

 is the most convenient indicator) are wholly suppressed, 

 while the automatic movements of respiration persist. 

 This is the degree of an.tsthesia required for any major 

 surgical operation, and is therefore frequently spoken of 

 as surgical an;esthesia. The finger-posts to its boundaries 

 are : "on this side the conjunctival reflex, on that side the 

 movements of respiration. 



The third and last finger-post — arrest of the heart's beat 

 — should not be passed. .Arrest of the pulse signifies an 

 almost hopeless state. The time of grace between arrest 

 of respiration and arrest of the pulse from which recovery 

 is almost hopeless is very brief indeed — hardly more than 

 a minute. The doctrine of the Edinburgh school — watch 

 the respiration, not the pulse — is sound doctrine. Stoppage 

 of respiration means danger ; stoppage of the pulse means 

 death. 



I think this sketch, rough as it is, will be suflicient to 

 bring before our minds a clear picture of the process of 

 anaesthesia and of its principal danger — cardiac syncope. 

 I do not wish to blur it with details. I shall therefore 

 not enter into the question of primary cardiac syncope, 

 nor call off your attention to other symptoms, such as the 

 state of the pupil and the character of the pulse and the 

 colour of the face. Nor shall I at present lay any stress 

 upon the fact that chloroform can be of variable quality, 

 and that like alcohol it may act differently upon different 

 people. 



First and foremost, if we are to secure the safe adminis- 

 tration of a powerful poison like chloroform, we require 

 to know how much of the drug is reauircd for the produc- 

 tion of the desired physiological effects, how much is 

 dangerous, how much is necessarily fatal. ConsTdering 

 the fact that chloroform has now been in common use , 

 for sixty years,' and that the uniform experience of physio- J 

 logists is to the effect that it is a dangerous drug as 

 ordinarily used, it is astonishing that its administration 

 should not rest upon any definite scientific basis. 



The fir-ir in?jo 



operaf'on undei 



y 19, 1^47. 



chioroform was performed by Sir Ja 



