THE WORLD INCIDENCE OF DISEASE.

five boys. Again, four temporary visitors to thedistrict, all staying in different houses, but consumingdealer A’s milk, sickened away from the district at orabout the same time. Apart from their milk-supplyno common link could be discovered, and the factthat the period during which they were all residingin the district covered three days about a fortnightearlier accords with Dr. AYCOCK’s view that theincubation period is long rather than short. On theother hand, the Ministry’s report appears to acceptthe view that the incubation period of poliomyelitisis usually short, and their theory of case-to-case, orcarrier-to-case, infection hangs partly on this view.

t

Here, then, is another crucial question that requiressettling.

There are weaknesses in Dr. AYCOCK’s chain evidence, of which the most important is his failurEto trace the infection back to any particular producer;either by means of circumstantial evidence or bythe discovery of an infective case among any farmhousehold or staff. We understand that his visitwas a brief one, and it is rather unfortunate that moretime was not given to this important part of theinvestigation. It may take weeks to elicit all theinformation relevant to a milk-borne epidemic.The details given of dealer A’s operations are some-what conflicting ; it is suggested that his Grade Asupply may have been implicated, but it is notshown that dealer F had contracted for a supply ofGrade A milk from him, and it appears unlikely thatdealer A would sell his best milk to a rival as ordinarycommercial milk. More use might have been madeof some of these facts, and such other phenomenaas the complete immunity from the disease of alarge school receiving milk only from dealer A, tonarrow down the number of farms possibly involved.Yet those who have frequent dealings with themilk trade are well aware of the difficulty in threadingits ramifications. The report of the Chief MedicalUtticer exhibits a striking difference in the age-dis-tribution of the epidemic in question, as comparedwith other outbreaks in 1926, or, indeed, with thegenerality of epidemics. Only 25 per cent. of thepatients were under 10 years of age, against the usualpercentage of 80 or 90. It is natural to explain thisby the fact that the schools affected contained childrenwhose ages were mainly over 10, but Dr. AYCOCKclaims that the proportion of cases under 10 amongpersons outside boarding schools was just over

50 per cent., which is still very low.Examining Dr. AYCOCK’S views in relation to our

criteria, we find his contentions to be that theepidemic tallied with a milk outbreak in its sudden-ness, in an incidence which was mainly on the con-sumers of a single milk-supply, in its unusual age-distribution, and in the somewhat equivocal andremote character of the other connexions betweenmany of the cases occurring almost contemporaneously.The controls, according to Dr. AYCOCK, were sufficientin volume to remove any suspicion of coincidence ; Iaccording to the Ministry they were not, and this is a point which should easily enough be cleared upWhether there was an infecting case at any farnsupplying the suspected milk will probably neve]be decided, but the fact that none was found mus1not be regarded as conclusive evidence against thEtheory of milk conveyance ; failure to do so has beera common enough experience in milk-borne epidemicsof all the infectious diseases. On the general questiorof probability it should be noted that the frequencyof reputed instances of milk-borne poliomyelitis not of a lower order than that in the commoneizymotics when allowance is made for their muchgreater prevalence. To sum up, we should say thatDr. AYCOCK appears to dismiss the evidence ofperson-to-person infection rather lightly, but hasjustice been done to the evidence of transmissionby milk ? It may be presumed that the facts withwhich he was dealing were equally known to, andprobably in the first instance ascertained by, thepublic health officials who made the inquiry and whodid not come to the same conclusion.

Annotations.

THE WORLD INCIDENCE OF DISEASE.

MEDICINE and hygiene were alive to the advantagesof international cooperation long before the Leagueof Nations came into existence, but the HealthSection is doing a great work in promoting a worldview of disease and in focusing the varied activitiesof different countries. Pathogenic bacteria haveno nationalities, and, with the world rapidly shrivel-ling as far as human intercourse is concerned, epidemicdisease is no longer a parochial question. The HealthSection receives information on the prevalence ofnotifiable diseases from practically all countrieswhere such information is collected ; it distributesthe collected facts by weekly and monthly publica-tion, and issues every year a general survey, thefourth of which (for 1926) has recently been received’!The first part reviews the main epidemic diseases,and compares their present prevalence with theirpast history with many maps and diagrams. Plaguedeaths in India fell below 50,000 for the first timesince it reached Bombay in 1898, and the trend ofrecent years hopefully suggests that the pestilenceis now really on the decline, perhaps because vaccina-tion is received more gratefully and abundantly,possibly because man is breeding out a more resistantrace. The article on small-pox gives a summaryview of the curious varieties into which the conditionseems to be separating out; if the case mortality inEngland had been what it was in India there wouldhave been 2427 deaths instead of 18, and perhapsfewer conscientious objectors. An interesting mapshows the progress of a very severe type of relapsingfever, due to the European spirochaete, across Africafrom the Niger in 1921 to the Sudan in 1926. Itwould be interesting to know why the case mortalityof typhoid in Norway and Austria is less than halfwhat it is in England and Japan. Nashville, themost typhoid-ridden big town in the United States,will welcome the new medical school which has beenestablished there. And in this way under each ofthe important diseases the report gives much informa-tion and raises many questions. The second half ofthe volume is taken up with a mass of statisticsarranged under countries. These are doubtless ofuneven value ; some of them are first rate, and eventhe worst are better than none. And we anticipatethat their incorporation and publication will do agood deal to stimulate the countries with imperfectregistrations to raise their standard to the best.The international bands of sanitarians who wanderthrough one another’s countries nowadays to see howthings are done will help this on very much.

DOMESTIC HEATING.

THE need for preventing the pollution of the air ofr

our cities by smoke has been brought prominentlyt before Londoners by the dangers and discomforts of

the ground fogs of Oct. 3rd to 7th and Nov. 7th to10th, and the pitch-darkness of Nov. 23rd. When

s many parts of the Home Counties were bathedin sunshine the metropolis was shrouded in gloom,and vehicular traffic rendered slow and difficult. Itis true that in the London area the deposit from theair diminished from 450 tons per square mile in1915-16 to 284 in 1921-22, but since the latter date

L there has been little improvement, and we still havefar to go before our air is clean. The percentage of

, sulphates in this deposit, which amounted in 1915-16to 17, fell to 8 in 1921-22, showing a greater reductionin sulphur than in total deposit. It is estimated thatin London domestic smoke forms about two-thirdsof the whole, so that a smokeless solid fuel would

’League of Nations Fourth Epidemiological Report of theHealth Section for the year 1926. London : Constable and Co.

1193INSULIN AND TUBERCULOSIS.—OPTIC NEURITIS.

go some way to purify the air. In a paper whichhe read at the recent Public Works, Roads andTransport Congress Mr. F. W. Goodenough drewattention to the contribution which the gas industryis making to the abatement of the smoke nuisance,setting out the case for gas and coke without beingunduly sanguine as to the part which will be playedby low temperature coke. Large scale experimentsare now being made by the gas industry in coöpera-tion with the Government in order to produce a fuelof this kind. At present some 65,000,000 tons ofcoal are burned yearly in the factories of the Kingdom,and 40,000,000 tons in domestic fires, while gas-worksin carbonising another 20,000,000 tons produceabout 10,000,000 tons of coke. This quantity of cokewould not supply our domestic needs for, as Mr.Goodenough points out, the whole output may soonbe absorbed by the increasing use of coke boilers. Inorder to produce enough low temperature coke tosatisfy domestic requirements at least 50,000,000 tonsof coal per year would be needed. Each ton wouldproduce at the same time about 3500 cubic feet ofrich gas having a calorific value of 800 to 1000 units,quite apart from other valuable by-products. Aprofitable outlet for these would have to be found.The 5,000,000 tons of anthracite mined per year inthis country are palpably insufficient to solve thesmoke problem ; and the present type of slow com-bustion stove in which it is burned does not providethe ventilation which is one of the essential functionsof a domestic fire. Electricity is hardly in the run-ning for domestic heating in a country which has nogreat waterfalls or other supplies of cheap naturalenergy. To generate electricity by burning coalimplies an initial heat loss of about 80 per cent.,while the loss in producing gas and coke is of theorder of 25 per cent. Thus when heat is required itis obviously uneconomical of fuel to obtain it byelectricity. What, then, is the solution of the domesticsmoke problem ? It would seem unlikely that lowtemperature, or any form of coke, can be the wayout, if only because the making of coke implies alsomaking gas. The combination of gas with some formof coke for domestic cooking and heating appears,then, to give most promise of success.

INSULIN AND TUBERCULOSIS.

IT is generally recognised that, the introduction ofinsulin has offered a new hope to the diabetic patientwho at the same time suffers from active tubercu-losis, and it was inevitable, therefore, that insulintreatment should, sooner or later, be tried for thenon-diabetic phthisic. The few records so far pub-lished have shown varying results, some favourableand others unfavourable, especially as regardstemperature reactions. Dr. J. Morin and Dr. F.Bouessee, of Leysin, have recently recorded a series 1of favourable results with this group of non-diabeticphthisics. The injections of insulin were given sub-cutaneously half an hour before the meal. For thefirst two days 5 units were given, then two injectionsof 5 units were administered for two days, and after-wards the quantity was increased until 30 units weregiven in two doses daily. The duration of the treat-ment was about one month. Occasionally the limitof 30 units in a day was passed, but as a general rulethis was regarded as a suitable maximum. No seriouseffects from hyperglycaemia were observed; transientdisturbance three or four hours after an injectionreacted immediately to the ingestion of carbohydrates.No local reactions of importance were noted, andthere were no urticarial eruptions such as have beenrecorded by some observers. Furthermore, thepatients, who were all afebrile at the beginning ofthe treatment, developed no rises of temperature asa result of the injections. In most of the cases

appetite improved and the weight markedly increased,as is well shown by the charts accompanying thereport. Cases in which the urinary excretion was

1 Annales de Médecine, October, 1927.

measured showed no marked alteration and no

oedema of tissues was observed. Eight cases in all arerecorded, and Dr. Morin and Dr. Bouessee are satisfiedfrom these preliminary tests that no harm resultsbut that weight may be increased and some patientspermanently benefited. It would be helpful to studya series of cases with metabolic tests carefully con-trolling the treatment at all stages.

OPTIC NEURITIS.

Two different abnormal states of the optic dischave in the past been known as optic neuritis. Oneof them is a swelling which is often very marked andcan be more or less accurately measured by theophthalmoscope in terms of dioptres ; it completelyobliterates the margin of the disc and the veins arevery much swollen. This condition may exist withoutany loss of visual acuity and is not really an inflamma-tion of the nerve at all but an oedema caused by apathological increase of intracranial pressure. Thesign exists in both eyes, though it may be moreadvanced in one than the other. It is always ofgrave import, being one of the typical signs of intra-cranial tumour. So far as sight is concerned thecondition, if unrelieved, passes sooner or later intooptic atrophy, involving blindness, partial or complete.If, however, the intracranial pressure is relievedby a timely trephining operation the swelling ofthe disc in a typical case subsides and optic atrophyis averted. This important fact will always beassociated with the pioneer work of the late SirVictor Horsley. Since there is no inflammation ofthe nerve in these cases, the term " optic neuritis "has been considered inappropriate and the terms" choked disc " or " papilloedema " are now generallyemployed. True cases of optic neuritis are those inwhich there is actual inflammation of the optic nervespreading either from the sheath or from an infectivefocus in the substance of the nerve. Toxins circu-lating in the blood due to general disease or tosyphilis appear to be the most usual cause. In thesecases the ophthalmoscopic picture is much less strikingthan in cases of choked disc. On the other hand, theloss of visual acuity occurs much earlier. Theobliteration of the disc margin is the earliest and themost valuable ophthalmoscopic sign. The swelling ofthe disc and engorgement of the veins may be slight.When a toxin is the cause the condition is usuallybilateral. When there is a localised inflammatoryfocus one eye only may be affected. Sometimes theretina is involved, as in albuminuric retinitis, and thecase is one of " neuroretinitis." In other patients,where the focus of inflammation is some way behindthe disc, the disc itself may appear normal and thecase is said to be one of " retro-ocular " or " retro-bulbar " neuritis. Since it is the macular fibres whichare chiefly affected, the typical symptom of retro-ocular neuritis is a central scotoma. It is stilluncertain whether ordinary tobacco amblyopia is atrue retro-ocular neuritis affecting both nerves or

whether the primary lesion is in the ganglion cells ofthe retinae with secondary changes in the nerves.It is certain that one of the most common causes ofretrobulbar neuritis is disseminated sclerosis. Thecausation of a great many cases remains a mystery,and although it has been usual to suspect infectionfrom one of the nasal sinuses, especially since Onodipublished his work demonstrating the thinness ofthe partition separating the optic nerve from thesphenoidal and ethmoidal sinuses, the actual number-of cases where this causation may be considered tohave been proved is relatively very small. The factis that acute retrobulbar neuritis generally tends to getwell in a few weeks without any treatment at all, andcredit for the recovery is easily misplaced. This

applies even to cases which are caused by dis-seminated sclerosis, although here the retro-ocularneuritis should be regarded as a danger-signal forwhat is in store in future. What has already beenstated is common knowledge to the physician andophthalmic surgeon. How far does it require modifi--