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should be put to the test of experiment. This has alreadybeen done in a few cases by Dr. Hale White. He has treatedcases of chlorosis with hydrochloric acid, a substance whichundoubtedly lessens putrefactive processes ; but although thepatients improved somewhat they did not mend any morerapidly than others who were simply treated with rest inbed and wholesome food. Dr. Mott suggested to me thatattempts should be made with bismuth ; this, like iron, formsan insoluble sulphide and, if Bunge’s theory is true, ought tobe as beneficial in ansemia as iron itself. I am not aware thatthis has yet been done.But I must now leave the question of iron and pass on to

the other element with the micro-chemical detection ofwhich we have to deal-namely, phosphorus. As has beenalready mentioned, it is in the nucleus that the most impor-tant of these phosphorised proteid-like substances chieflyoccur.

[The lecturer then gave details of the histology of thenucleus, and continued :]Histology teaches us the complicated nature of the nuclear

structures ; the various names of the materials found wereoriginally given from their microscopic appearances ratherthan from their chemical properties. The method of gastricdigestion enables us to obtain nuclein in large quantitiesbecause the rest of the cell is dissolved. Nuclein is, in fact,a substance of which there is a considerable amount ofaccurate chemical knowledge. But there is another micro-chemical method which promises to be of as great value asthat of gastric digestion, and it is to this that I have beenleading up. It has only been quite recently introduced, andits object is the microscopic localisation of phosphorus.Lilienfeld and Montil are the workers to whom we owe themethod, and it consists in taking sections or teased portionsof fresh tissues and organs and soaking them in a solution ofammonium molybdate. If phosphorus is abundant and presentin the form of simple compounds like phosphates, the yellowcolour of the preparations is visible to the naked eye within afew minutes; whereas, if the phosphorus is present in amore complex union the time required is longer and themicroscope may be necessary to detect the yellow colouration.After this the sections are transferred to a 20 per cent. solutionof pyrogallol dissolved either in water, or. which is better, inether. The sections are dehydrated, clarified, and mounted inCanada balsam. The action of the pyrogallol is to reduce thephospho-molybdate, and the resulting colouration is brown orblack according’ to its-intensitv.

[Lilienfeld and Monti’s chief results were then summarised.Amongst other instances, the lecturer remarked :]

In nervous tissues, as one would expect from the richlyphosphorised nature of their constituents, the staining wasvery intense, and in nerve cells the cell protoplasm wasstained even more deeply than their nuclei. In conclusion,let me, in a few general terms, sum up what I have beensaying. We have followed a number of divergent lines,all, however, starting with the cell, and all further con-nected by the link of micro-chemical investigation ; but theyhave led us here and there into digression in which the cell,as such, has been left far behind. Let me now proceed togather up these scattered strands. We have seen that, inorder to obtain a chemical knowledge of the cell, it is neces-

sary to have, in the first place, an accurate knowledge of itsanatomy, but that the histological methods of staining andso forth depend on a chemical basis. The main substance ofthe cell is proteid, and this proteid when in the living cell isintra-molecularly different from that in non-living protoplasm.In addition, there are smaller quantities of lecithin, choles-terin and inorganic salts. As the result of their vital activity,cells form various products ; some of these, like carbonicacid and urea, are the result of oxidation, and these pro-ducts of destructive metabolism leave the cell and are

ultimately got rid of by the excretory organs. Others, likeglycogen and fat, may be for a time stored up in the proto-plasm, and it has long been known that these can be detectedby the use of iodine and osmic acid respectively. Morerecent micro-chemical methods have taught us that the

important elements iron and phosphorus can be alsolocalised in the cell or in its nucleus, and on account of thenewness of these investigations I have dealt with them atconsiderable length, pointing out, on the way, what I con-ceive to be some of the practical bearings of the results ofsuch inquiries. But in addition to such facts there are othersconcerning which the present state of our knowledge doee

1 Zeitschrift der Physiologischen Chemie, and xvii.

not allow us to pronounce positive chemical opinions, andhere I would again allude to the important work of Ehrlichon the behaviour of protoplasmic granules to the aniline dyes.The fact that these dyes are, some acid, some alkaline, andsome neutral, would seem to indicate corresponding differencesin the reaction of the granules themselves. The reaction ofliving protoplasm as a whole is alkaline, but there are variousacid products formed as the result of protoplasmic activity,such as carbonic acid, lactic acid, uric acid, and in one well-marked case that of the gastric cell, hydrochloric acid. It

.

appears to me more than probable that during life thereaction of the protoplasm or of parts of the protoplasm is achanging one ; the reaction may be in as unstable a conditionof equilibrium as the other factors of cell life are. We knowthat when the circulation ceases and the cells can no longerbuild themselves up from new material, but are still suffi-ciently living to continue their retrogressive or katabolicchanges, they become acid from the accumulation of suchsubstances as lactic acid or from the formation of acidphosphates. This tendency to become acid is being constantlycorrected by anabolic or assimilative changes during healthycell life, and it seems quite possible that in Ehrlich’s stainingprocesses we have an actual proof of this condition ofunstable chemical reaction ; this appears to be very strikinglyconfirmed by a recent experiment of Hardy and Kanthack,2who found that eosinophile cells after feeding on bacteriabecome amphophile. But, leaving such speculative proposi-tions and coming to our positive knowledge, none can denythe enormous impetus that has been given to chemicalphysiology by the combination of the use of the microscopewith that of chemical reactions. Valuable as micro-chemistryis, however, as a means of research, it cannot go very deeplyinto the matter, and happily we can supplement the know-ledge so obtained by the methods of macro-chemistry. Wehave already made the acquaintance of nuclein, the chiefmaterial in the nucleus, and of the various proteids containedin the cell protoplasm, and it will be my duty in my nextlecture to develop this aspect of the subject more fully.

The Milroy LecturesON

CHANGES OF TYPE IN EPIDEMIC DISEASES.LECTURE III.

Delivered at the Examination Hall, Victoria Embank-ment, on Feb. 28th, 1893,

BY B. A. WHITELEGGE, M.D., B.Sc. LOND.

Prevalence detc1’luined by External Conditions. - Notaccornpanied by C7ia?zge of :7ype.-Milk Epidernics.- TVatc’rEpidemics.-Seasonal Prevalence. -AccU’tnulation of Suscep-tible Persons.

MR. PRESIDENT AND G-ENTLBMEN,—Although change oftype is an important factor in determining the fluctuationsin prevalence of epidemic diseases, it is not the only factor.Wide diffusion may take place without increased severity,and, indeed, it is not an uncommon experience to find thatsudden epidemic extension is accompanied by apparentlessening of average severity and lowering of the case

mortality. This involves no real exception to the general rulethat the tendency to epidemic diffusion is greatest when theintensity is at its maximum. There are obviously three prin-cipal classes of conditions 111 on which epidemic prevalencedepends : (1) The energy of the contagium itself, its power ofwithstanding hostile influences and of overcoming resistance ;(2) the facilities for transmission of infection to susceptiblepersons ; (3) the susceptibility of the individuals upon whomthe contagium is to be grafted. The conditions which comeunder the second bead include the varying degrees of

proximity, from the closest contact to complete isolation,atmospheric states favourable or unfavourable to diffusion,and transmission by other media, such as water or milk.These are constantly changing, and, however orderly the riseand fall of intensity may be, the prevalence will be modified

2 Proceedings of the Royal Society, vol. lii., p. 270.

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3i,t- every phase by a multitude of extraneous conditions.’Without any change in the real infectiveness of a disease, anepidemic, or, at all events, prevalence, may be brought abouthy sudden increase in the facilities for infection of susceptiblepersons ; or, conversely, the conditions may become unfavour-able, and the prevalence thereby be lessened without any lossof intensity in the type of the few attacks which occur. Suchmechanical outbursts or interruptions, due to causes which? re, in a sense, accidental and usually temporary in character,"have one important feature in common which presents a con-veniently sharp contrast to the broader cycles determinedby altered quality of the contagium. They are attendedby a lowered case mortality. If during the course of anepidemic, or in an inter-epidemic interval, a sudden in-crease of prevalence be brought about by accidental cir-sumstances of weather, or food infection, or the like, the

proportion of fatal attacks during that exceptional prevaleneewill be less than in the more normal periods which precede,nd follow it. Such a relation is antecedently probable andjs ir harmony with actual statistical observations. It seemsreasonable to assume that those persons who are most sus-septible to attack will be most readily singled out for it ;and, moreover, that amongst such persons the attacks will onthe whole be more severe than amongst the less susceptible.

, Jf, therefore, a wide extension of prevalence occurs it will bemainly at the expense of persons whose susceptibility is notof the highest order and whose chance of recovery is greaterfor that reason. The aggregate case mortality will hence belowered, if the energy of the contagium remains unaltered.Perhaps the converse proposition is even more self-evident.If an epidemic, instead of being widely diffused, is narroweddown to a small fraction of the population, it is probablethat the few who are still subjected to attack owe theirselection partly to a higher average susceptibility, andthat amongst these specially susceptible persons the attackswill be more severe. In a mixed community small-poxattacks the unvaccinated in far larger proportion thant.he vaccinated, and with far greater case mortality. If,therefore, the disease, instead of being limited to theiormer class, extends in some degree to the latter, thegross case mortality will be lowered by this change, whichinvolves an increased average resistance in the personsattacked.. Another simple illustration is afforded by milk epi-demics of scarlet fever, such as that which occurred atWimbledon in 1886-87. The disease was not left to follow itsusual course and pick out the more susceptible portion of thepopulation for attack. Infection was imparted to the milktnd by that means forced, as it were, upon a large number ofpersons selected, at random. Some of them resisted attack

altogether ; others suffered slightly, a few more severely.There were only three fatal cases amongst 600— case

- Mortality of 0’5 per cent. That milk epidemics of scarletfever are rarely severe in type was pointed out several yearsago by Sir George Buchanan and Mr. Power, and the obser-vation has been amply confirmed by later experience, although1n exceptional instances (at Halifax in 1881, for example)the fatality has been high. Milk epidemics of enteric feveralso seem to be attended as a rule with low average casemortality, although there are notable exceptions. It wasi-’tily about ten or twelve per cent. in the Armley, Moseley,4,larylebo-ie and other well-known outbreaks, and little morehalf of this at Eagley and Bolton in 1876 and at

Glasgow in 1875. As regards diphtheria it is scarcely possibleto fix upon a standard for comparison, but the recorded caseMortality in milk diphtheria epidemics on the whole seems to3e somewhat lower than that observed in diphtheria epidemicsJue to other causes.The question is not always a simple one. Now that bovine

scarlet fever, diphtheria and perhaps enteric fever have comef the front, we have to bear in mind the possibility ofattenuation (or the reverse) of the disease by passage throughthe cow, as well as the suspicion that the character of theattack may be modified by the magnitude of the dose ofpoison. Then, again, Mr. Power has given reasons for be-3 ikying that the diphtheria poison may multiply in milk if leftT.ndmg for some hours, possibly increasing in virulence as- v.eM as quantity. But these elements of uncertainty leavelmtouched the general proposition that, if compared upon equal.’Mrm&, the average case mortality is lowered by this as byMhe:’ mechanical facilities for the diffusion of infection, so<.r ay it is merely mechanical. Milk epidemics, as a rule,3tre of very brief duration, dying out speedily without light-ing up any lasting prevalence ; and from a theoretical stand-yo.R’: it is to be anticipated that such would be the case.

Their occurrence (unlike the beginnings of an ordinary out-break) does not presuppose the existence of other externalconditions favourable to wide extension. It seems, too,.that the infectiousness of individual cases of this kind isnot great.

Similar considerations apply to water epidemics. Theyare usually attended with low case mortality, although theuncertainty as to the dose of poison is a disturbing influence,and indeed it may be open to question whether the mildnessof attack which characterises great water epidemics may notbe due in part to the minuteness of the dose forced upon thepersons consuming the water. When the volume of water

polluted is limited, the concentration may be supposed to beexcessive and the dose large. Dr. Barry has found that whenenteric fever arises from pollution of a well the attacksare often severe, but that in water epidemics on a largerscale, as at Bangor and more recently in the Tees Valley,a low average case mortality has prevailed. In the Caterhamepidemic of 1879, investigated by Dr.. Thorne Thorne,fourteen died out of the 305 attacked, the percentage beingtherefore 4 ’6 only. At Mountain Ash in 1887 an epidemicof enteric fever occurred which Mr. Spear found to affectvery unequally the persons living respectively inside andoutside a certain small area supplied by a particular watermain. Within this special area 179 per 1000 were attacked,outside it 6 per 1000 only. Only six per cent. of the caseswere fatal.A third and still more important kind of prevalence is that

which from its constant relation to season is assumed to beconnected with weather and climate. So far as scarlet fever,enteric fever and small-pox are concerned, these seasonalchanges prove upon investigation to be simply changes inprevalence, without any real alteration in intensity ; on thecontrary, the maxima are attended with a somewhat lowercase mortality than the minima. They are, in short, "super-added waves, " like milk epidemics and water epidemics.

If the average seasonal curve of attacks, or even of cases

admitted to hospital, be compared with the seasonal mor-tality curve of the same disease, it will be found that theformer, whilst closely parallel with the latter, is somewhat inadvance of it at every phase. The attack curve, moreover,has a wider range than the other ; it rises higher and fallslower. Since the seasonal maximum of attacks does notcarry with it a proportionate excess of deaths, it follows thatthe attacks at that phase are on the average less fatal; and,conversely, as the falling off in number Qf attacks at the lowestphase is not attended by a proportionate reduction in mor-tality, the comparatively few attacks then occurring must besomewhat more fatal in character. In the Annual Summaryfor 1890 the Registrar-General gives charts which illustratethese points very clearly, especially as regards enteric feverand small-pox. In making the comparison, two curves arenecessary. The Registrar-General has pointed out that themortality curve will naturally be somewhat flatter and lessacute than the other, since the deaths arising out of a groupof cases admitted or notified in a given week may be spreadover several successive weeks, especially in diseases of longaverage duration. Dr. Longstaff calls attention to the pos-sibility that limits of hospital accommodation may at timesof maximum prevent the admission curve from rising as highas it otherwise would. But after making due allowance forthese sources of error-which tend in opposite directions sofar as the present comparison is concerned-the contrast ismarked. In the charts referred to, the Registrar-Generalcompares in respect of each disease the average seasonalcurve of mortality in London with that of admissions to thevarious isolation hospitals. The admission curve of entericfever rises 100 per cent. above and falls 50 per cent. belowthe mean, while the death curve has a range little morethan half of this ( + 50 per cent. and - 30 per cent.). 2As regards small-pox, , too, the difference is stronglymarked, the admission curve reaching +70 per cent. and- 60 per cent, and the death curve + 30 per cent. and- 40 per cent. It should be noted, however, that owing to

1 Studies in Statistics, p. 403.2 In the Annual Summary for 1880 the Registrar-General states

that "It appears from the records of tne London Fever Hospital,1848-57, that out of an equal number of cases of enteric fever about asmany die in one quarter of the year as another, the spring quarter,however, showing a slightly greater fatality amongst its cases than anyone of the other three." It is not to be anticipated that hospital caseswould include a full proportion of the slighter attacks, but it seemsfrom the above observation that even amongst those of sufficient severityto bring them into hospital there is some indication of higher casemortality at the period of spring minimum.

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the periods of record being different the two curves are notaltogether parallel, the winter maximum being far moremarked in the death curve, based upon fifty years’ statistics,than in the hospital curve, which relates only to the fifteenyears 1876-90. But in an earlier chart of similar character3the concurrence is closer ; and in both instances the contrastin range is very striking and confirms the relation betweenmaximum seasonal prevalence and lessened average fatalityof attack. We may conclude, from the difference betweenthe two admission curves referred to, that small-pox since1880 has somewhat altered its seasonal curve, the springmaximum having become much more prominent and thewinter maximum less so. The differences between the deathcurve and admission curve for scarlet fever are slight, andnotification statistics afford a clearer contrast. Still theattacks, measured in either way, rise higher above their meanin autumn, and fall further below it in spring, than do thedeaths ; and the same inference of lessened case mortalityin time of seasonal prevalence may be drawn. As regardsmeasles there are few data for comparison, but Dr.

Harvey Littlejobn5 has given us the seasonal curves ofdeaths and notified attacks for the ten years 1880-89in Edinburgh. They are closely parallel, and, so faras the principal maximum in spring is concerned, there is noindication of altered case mortality, the crests being of equalheight; but the attack curve falls rather lower than the otherat the minimum, and the smaller maximum in December ismore marked in the attack curve than in the other. At allevents there is no evidence of increased case mortalityaccompanying the seasonal prevalence. The epidemiologicalcharacter of measles is such as to render it unlikely that anystrong contrast would appear. The epidemics are brief andwidespread and the attacks which bridge over the intervalsare few. Hence the data, including the monthly means ofattacks and deaths, are made up almost exclusively of therecords of epidemics, the attacks and deaths during theintervals being too few to materially affect the averages or toafford a basis for comparison.Amongst certain diseases of mobile type, and particularly

those which are dependent upon changes in the soil, theseasonal curve has a different meaning. The seasonalmaximum of prevalence is dependent upon increased virulence,and the severity of attack is greatest at that time. Thelowered case mortality of enteric fever during the autumnalprevalence divides it sharply from the purely telluric group inthis respect. Diphtheria, again, is liable to rapid change oftype, and it may be that seasonal conditions bring aboutintensification as well as wider diffusion of the contagium.The notification figures quoted by Dr. Thorne Thorne6lend some support to the idea that the case mortality indiphtheria is, on the whole, increased during the autumnmaximum ; but further evidence is wanted. It would seemthat, in small-pox at all events, the seasonal curve isof wider range during periods of greater epidemic in-

tensity than at other times. Buchan and Mitche1l7 foundthat this was the case in 1870-71-72 to a very marked degreeas compared with the other years for which records wereavailable. Indeed, the figures given by them show a gradationin this respect in successive quinquennia, from the point ofminimum mortality in the fifties to the great epidemic of theearly seventies, a gradation which is in keeping with otherindications of progressive change in the character of small-pox during that period. In the following table the range ofthe mean seasonal curve for each group of years is measuredroughly by the percentage excess of the January maximumover the September minimum :-

Table of Small-pox Deaths in London.

3 Registrar-General’s Annual Summary, 1880.4 Epidemiological Society’s Transactions, 1887-88, p. 176.

5 Ten Years’ Compulsory Notification of Infectious Diseases in Edin-burgh.

6 Diphtheria: its Natural History &c., p. 32.Journal of the Scottish Meteorological Society, 1875.

From this it appears that, as the destructiveness of small-pox increased in the sixties, so did the range of its averageseasonal curve. If, however, the quinquennia are tracedbackwards from the time of least mortality in the direetiouof the previous great epidemic of 1838, the otherwiseaccordant indications are interrupted by a conspicuous lessen-.ing in intensity of the seasonal curve in the years 1840-44.Another point of some interest in connexion with the seasonalcurves of infectious diseases is that they are often bolderwhere climatic changes are more intense and more orderly.This is seen, for example, upon comparing the curves ofsmall-pox, measles, diphtheria, or enteric fever (not, however,of scarlet fever or whooping-cough) for London and NewYork respectively. SThe varying incidence of infectious diseases at different

seasons is no doubt dependent, directly or indirectly.upon climatic conditions. It has been suggested thatsocial relations have much to do with it, there beingcloser aggregation in-doors in the colder months, but this

explanation is negatived by the want of uniformity amongstthe diseases in question. Some infectious diseases aremost prevalent at the beginning of the winter, othersat the end. Scarlet fever reaches its maximum in England inOctober, in Germany and Scandinavia in January, in NewYork in May. Further than this : the rise begins long befcrethe maximum is reached, so that if it be alleged that thecommencement of winter-conditions causes the maximum ofscarlet fever prevalence to be reached in October it would.still be necessary to explain why the rise begins as far backas May. Perhaps the most unequivocal instances of a seasonalprevalence of disease dependent upon social conditions arethose which arise from the difference in risk of exposure toinfection on Sundays as compared with other days of theweek. Thus the rash of small-pox has been stated to appearmore often on Sunday than on any other day of the weekamongst domestic servants, the usual interval between infectionand rash being fourteen days and the chance of eaat-doorinfection being often limited to Sunday. The notificationrecords at Nottingham show a very decided minimum in thenumber of onsets of scarlet fever on Wednesdays, correspond-ing, as it. would seem, to a maximum risk of infection orSundays.

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THE CHOLERA EPIDEMIC IN RUSSIA.BY FRANK CLEMOW, M.D. EDIN. &c.

No. I.IN CEXTRAL ASIA AND SIBERIA.

SINOO 1872-73 no epidemic of cholera has occurred ir,

Russia that can compare in violence and extent with therecent outbreak. The disease still lingers in some parts of &pound;

that empire, but these bear but a small proportion to those inwhich it is extinct, and it is now possible to gather from thecompleted returns some impression as to the severity of theepidemic of 1892. Daily reports have been received fromevery part of the country by the authorities at the MedicalDepartment of the Ministry of the Interior in St. Petersburg,but these have in many instances been supplemented by laterand fuller reports, so that the final totals are considerablygreater than the sum of the daily ones would be. With

regard to the authenticity of the figures given in this and thefollowing articles, it should be stated that they have been inevery case obtained directly from the authorities just named.The liability to error, particularly where the figures are derivedfrom such distant and sparsely inhabited regions as thosewhich form the subject of the present article, is obvious, butthe Russian Government has spared no effort to obtain ascomplete returns as possible, and I am assured by theDirector of the Medical Department that in no case does theerror exceed 10 per cent. It is proposed hereto trace brieflythe course of the epidemic throughout the Russian empire.The cholera reached Russia direct from Persia. It threatened

her frontiers as soon as it appeared in Meshed, which is littlemore than 100 versts from the line which separates thetwo countries. As Meshed may be looked upon as the nidusfrom which the disease spread to Russia, it may be worthwhile to look a little closer at the nature of this town. Meshed

8 Buchan and Mitchell, Journal of the Scottish MeteorologicalSociety, 1878.