CHAPTER XVI.

Non-occurrences of measles significant as to causation-The great epidemic in Victoria-Instances of exemption traced to absence of efficient aircontamination with the "straw fungi "-The case of the Abbotsford Nunnery.

PUTTING Sucklings and nurslings on one side, curious instances of exemption from measles are recorded. Children have gone untouched through one or two epidemics that have invaded the house in which they lived, to be overtaken in a third. Infected children have been put to sleep with uninfected children in order that the disease might be communicated; but the healthy children have not taken it. Some families have not had measles for two or three generations, and are set down as being altogether immune-as having permanent or hereditary immunity.

Of all the facts connected with the incidence of a specific infective disease, those which relate to its non-occurrence where its occurrence had seemed imminent, or inevitable, are sometimes the most instructive. They may give a clue to causation not to be had from occurrences of the disease, and they furnish us with the great negative proofs of sound inferences as to causation. Contagionists, however, have contented themselves with trying to reconcile exemptions of all kinds with their doctrine as nearly as may be; and when the instances of exemption. have proved intractable, and could not be brought into unison with the tenets of contagion, they have been regarded as exceptions to, or aberrations from ordinary laws. This way of dealing

with rather a large group of facts has been found more convenient than enlarging the theory so as to take in the facts; though it has left us with a theory of the causation of an infective disease by an infective agent that fails to infect, when, by the theory, it ought to infect.

All vagaries, anomalies, or in-and-out occurrences and nonoccurrences of measles, so far from being irreconcilable with the "straw mildew theory," are thoroughly in accord with it and come well within its purview; and, moreover, they suggest a practical trial of its value. For if it be true that these nonoccurrences are due to an accidental absence of damp straw from particular bedrooms, it is an easy matter to reproduce any number of non-occurrences by keeping damp straw out of bedrooms. And admitting that this unscientific way of getting at the truth, or of trying to get at the truth, is not entirely satisfactory, and that apparently favourable results could be regarded only as negative evidence, still if a few hundreds or thousands of children were subjected to the rough experiment indicated, and were found to remain free from measles during epidemics, the fact would be negative evidence of more or less worth.

Observers as a rule have been more struck by one or two cases of exemption in families than by the escape of whole households, or of a class of persons domiciled together, in the midst of epidemics. They have not been greatly attracted to such exemptions and have not been so much exercised by them, because, perhaps, such exemptions have admitted of being easily and lightly set on one side by assuming that the contagion has not found entrance into, or has not made good its footing in, the habitations of the exempt. There is an air of seeming probability in this assumption; but it has not been so easy to hit off a decent reason, on contagionist principles, why the disease, when established in a family, should fail to attack one or more of the children-as may be gathered from the recourse of the authorities to the queer dictum that it is to be accounted for only by a suspension or an alteration of natural laws. Yet the exemption of an entire family, or of a number of children of different families collected together under one roof, when not

isolated in any way from a community in which measles is raging, nevertheless offers some hard problems to the contagionist -problems that have been overlooked or evaded, and not solved. For when in succeeding epidemics the exemptions of the same children, or of other children in the same dwellings, are found to recur, the question becomes more and more complex. When it is seen that this has occurred in a number of dwellings, the probabilities that the inmates have escaped merely because of a chance distribution of the contagium, are converted into a certainty that chance has had nothing whatever to do with it. A fortuitous dissemination of the unknown contagium with a constant result is not a possible assumption. But there is a still more difficult question for the school to resolve. Of two classes of persons living in close and intimate relations under the same roof, the one shall be largely infected by the measles poison and the other shall be entirely exempt. It is required, therefore, to evolve a scheme of distribution of the contagium vivum to meet such cases. But the point may be left until after the facts are produced.

In order to convey a clearer notion of the exemptions to which attention will specially be drawn, it may be as well to give some particulars of the Victorian epidemic. In the paper before referred to I wrote :

The Australian summer of 1874-5 was remarkably dull, cloudy and moist. Shortly after this unusual weather set in, thousands of families in and around Melbourne were attacked with measles, and before long the whole colony was involved. The epidemic was more extensive, though not so fatal, as that in Fiji; still, the mortality was such that it was publicly discussed whether national prayers should or should not be offered up for deliverance from the pestilence. I watched the progress of the epidemic, and took especial pains to search into exceptional, strange, or irreconcilable phenomena. . . . The results are shortly as follows:-Every shade and variety of measles were represented, from the mildest morbilli mitiores to the most malignant morbilli graviores. At Richmond, a suburb of Melbourne, three children in one family, who were playing about one day, died the next from black measles. In the Ballarat district a virulent roseolous type prevailed. All classes

were attacked without distinction, but the wealthier and cleanlier orders suffered least. . . . Throughout the epidemic I could not discover any instance of measles in a dwelling from which damp straw had been excluded, but in every house where measles occurred the presence of damp straw in the bedrooms was easily made out.

Numerous instances of part of a family only being affected came to my knowledge. In most of these instances I found either that the escapees had not slept on straw, or that, where they had, their bedrooms admitted the morning or mid-day sun freely. . . Groups of families in remote villages were attacked on the same day.

In some of the instances of exemption the circumstances were peculiar. For example:

CASE I. There was but one exempt in this case. The landlady of an inn in a village in which measles were especially virulent and many deaths had occurred, was greatly concerned about her only child, a daughter whose attack she expected daily, although the girl had escaped for two or three weeks after the first local occurrences of the disease. I took the child's exemption up to that time to be one of the ordinary exemptions, due either to her not sleeping on straw, or to the straw on which she slept having been kept dry by the sun's rays. But on questioning the mother, I was thrown out at first on learning that the child not only slept on a straw bed, but that her bedroom faced the west. Pushing the inquiry further, however, I elicited that the mother, fearing infection from convalescent children taken to the inn, had moved her child out of the main building to a small room over a detached kitchen, the chimney of which passed through the room close. to the girl's bed. It was obvious that as the kitchen fire of an inn has to be kept going, even in summer, the straw on which the girl had lain had thus been kept dry and crisp.

CASE II-A squatter on the Murrumbidgee brought his wife and five children down to a large hotel by the seaside not far from Melbourne. A week or so afterwards he mentioned to me that having been obliged to leave the station, for the children's sake, before shearing was over, because of the fearful amount of typhoid, dysentery, influenza, and diphtheria all

round the homestead and the district, he found he had brought them into the very midst of a horrible epidemic of measles. Other settlers had done the same, and there were no less than seven-and-thirty children in the hotel. They had been playing together, and as some of them had been longer there than his children, and as the disease was everywhere in the neighbourhood, of course they were all in for it; and it certainly looked very likely. Five or six weeks, however, passed without his children being attacked, and not a single case of measles occurred in the hotel during the whole of the epidemic. it was evident that some unusual conditions obtained in the house to account for the exemption of the inmates, I made special inquiries, and found that in place of ticks filled with straw all the beds of the children in this hotel had ticks filled with "flock." As the occupants were of the wealthier class, the rooms were of course well-ordered and cleanly; and as the excreta-disposal system was excellent, there was at once the explanation of this striking exemption of the whole household.

As

CASE III. The Abbotsford Nunnery and Reformatory, containing between 200 and 300 inmates, more than one half of them children, was remarkable on account of its perfect freedom from measles during the epidemic. Having obtained. permission to inspect the dormitories, I found that the principal of these are long rooms, with windows (unshaded by verandahs or Venetian blinds) on three sides. The other minor sleeping apartments (for the older inmates) do not admit such a flood of sunlight, but they are all airy and sweet, and unusually light and bright for this country, where people, unfortunately for themselves and their children, take pains to exclude the sun from their bedrooms. All the beds in the institution were of straw; the blankets, &c., had been neatly folded up, leaving the ticks freely exposed. In every room the straw in these ticks rustled and crackled under the hand as only thoroughly dry straw will. This was no doubt partly due to a wholesome regulation mentioned by the Lady Superior, by which it is ensured that all the bedding is removed periodically and aired in the sun; although, probably, the exceptionally free ingress