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CHAPTER XIII.

Variations in type of measles governed by variations in infection— Epidemics dependent on seasonal conditions-Protection derived from infection an illusion-The fallacy shown by re-infection in recurrent epidemics-Three and four attacks of measles not uncommon-Case of Dr. B.'s son-Relapses or re-infections (?)-Present view of protection entails the assumption that the prophylactic power of an attack increases year by year-Second attacks held to be spuriousThomas deprecates second attacks of true measles-Composite and variable infection reconciles divergences from the recognised types.

FROM the days when straw and rushes were strewn upon floors down to these modern times when the use of straw bedding is universal (except where the steel mattress is in vogue), the nations of Europe and their offshoots in newly discovered lands, as well as the inhabitants of some other countries, have provided their bedrooms with a supply of vegetable fibre affording an ample field for the growth of "straw fungi;” and for the most part this prepared soil has been placed under just such conditions as to ensure, at certain epochs, a continuous inhalation by almost the whole of these peoples during their hours of sleep of an atmosphere heavily charged with the spores of the fungi.

One of the many noxious and deadly results of breathing this atmosphere has been, as I infer, the occurrence of measles. It has been pointed out how variations in the type of the disease may be accounted for by this inference. By it also it may be seen that the differentiation in the symptomatology of the outbreaks correspond to a differentiation in the kinds and proportions and in the quantities and qualities of the forms

in the vegetation imbibed-that all the various and varying elements in the sum of the infection at different places and at different times have been represented in the phenomena of the outbreaks.

Measles disappears from a region for many years, perhaps, but in the low haunts and dark quarters of most large cities, there is generally enough moisture in the air of the sleeping places of the people to keep the straw bedding almost always damp. In such places the intervals between the crops of fungi and between the periods of efficient contamination are much shorter, and from some thickly populated neighbourhoods measles are rarely entirely absent. London and other large cities are never altogether free from the disease, and at some period of every year circumscribed outbreaks occur somewhere amongst the lowest classes. But outside these pest-holes, and among the general population both of town and country, the occurrence of measles on a large scale is controlled by "seasonal" conditions.

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A continuance of warm and rainy, or cloudy and "muggy weather seems more favourable for the outbreaks in some regions, though in others and perhaps in most regions, especially in Europe, they occur oftenest in cold wet weather. The great requirement for extensive epidemics is that continued hygrometric state of the air over a large district which will affect the interior of dwellings and make the straw in the bedding damp, and keep it damp. This long-existing damp state of the straw in paillasses, ticks, &c., throughout a wide tract of country, will obtain in the dormitories of communities at irregular periodsat intervals of from a month to a few months, or from one to two or ten or fifteen years, or longer. Between these periods straw under cover in fairly wholesome houses is mostly dry, or is not kept moist long enough to cause efficient contamination. of the air of bedrooms, except in some instances in which sporadic cases occur.

When the epidemical seasons return after many, or even a few years, they who were affected in the previous epidemic, as a rule, escape. Yet the straw bedding of the families is there,

and is probably in a similar, if not in a worse, state than before. What I take to be the explanation of the exemption of those formerly infected has been given; but the fact that adults are rarely or not often attacked during measles epidemics is set down, alike by the vulgar and the learned, to immunity acquired by a previous attack. This interpretation of the general exemption of the adult population is simple and convenient, but there are cogent reasons for questioning its soundness. Although this form of prophylaxis is said to have been so effective that a clearly cut line of demarcation has been seen to run between the previously infected and the thitherto uninfected in measles epidemics in the Faroe Islands, in Japan, and elsewhere, yet it would seem to require stronger evidence to establish the statements on the point than we have at present. Possibly this ring-fence may have seemed to have been present to an inquirer in a few instances, but I cannot help thinking that a good deal must have been taken for granted, and that a foregone conclusion had something to do with the generalisation. At all events this strict law of protection has not sheltered English-speaking or Continental communities. On the contrary, on them the incidence of measles has fallen without any sign of nice discrimination in this particular during epidemics; and more especially during those which have followed previous epidemics at the same places in a shorter time than usual—which is all the more singular, seeing that the degree of protection should, of course, be the higher in a ratio with the recency of the infection. In point of fact the explanation of exemption by immunity acquired from an attack of measles does not cover the phenomena of the recurrence of the disease. The question of immunity, though it might not, perhaps, affect the validity of my main argument touching causation, involves nevertheless several side issues of some importance.

It is by no means uncommon for adults, youths, and children to have three or four attacks of measles within a few years. I published a typical case of the kind which may be given again. "A lad of eighteen, the son of a leading physician, 1 Medical Times and Gazette, April 28, 1877.

who had been twice before, in different years, affected with measles, was attacked for the third time in this epidemic, and very severely. Dr. B., his father, informed me that he had not observed any differentiation in the symptoms of the three attacks. . . . The case of Dr. B.'s son was peculiar. . . . I learned from him that his son not only slept on a paillasse in a room with a southern aspect" (south hemisphere), "but that the paillasse was placed upon, instead of under, the hair mattress, and that this reversal of the usual order of things had obtained for 'years." Such cases are, perhaps, more common in the warmer latitudes, though numbers of cases in colder regions are recorded; and in many of the instances of recurrence two or more of the attacks have occurred between epidemics. These instances of reinfection, though not common, are difficult enough to reconcile perfectly with a prophylactic power given by infection, but another class of cases is still more difficult to reconcile with this endowment of immunity.

An epidemic of measles may be followed within a few weeks, or months, or a year, or two years, by another epidemic of measles, in which the children who were infected in the first epidemic, and have recovered, are attacked a second time, and the children who escaped the first may succumb to the second epidemic. These cases must be distinguished from another class of cases in which a second attack occurs either during convalescence, or before convalescence has begun. Some writers mix these classes of cases up together and call them both relapses. But though neither, perhaps, can legitimately be styled a relapse, it is an evident misnomer so to designate the class of cases in which an interval of months or of a year of perfect health intervenes before the second attack; for the concurrent implication of those previously not infected points most significantly to a reinfection—from without—of the previously infected. If there is the colour of a reason for assuming that the sick, or the convalescents from measles, may have a relapse-that is, from a revived activity of the morbid material within, and not from a further introduction of the specific infection from without, the body-there can be no shadow of a

pretext for supposing that either adults or children who have been well for a year ever get a relapse. Even if an analogy be found between Jungle or Roman fever and measles, still when the ague fits come on years after the first brunt of the infection, we see plainly enough that they are not due to a resubmission to the malaria, when others living with the sufferers are not implicated; and the inference therefore is that in such cases the recurrence is from within. And a simultaneous recurrence of measles among numbers during an outbreak is just as palpably from without. It is, however, obvious that if the plain and simple and, as I conceive, the only interpretation of a recurrence of this kind, namely, that it is a reinfection, were admitted, the theory of protection from infection would have to be greatly modified, if not altogether abandoned.

For if we couple the cases in which children who, having thoroughly recovered from measles, are infected a second time, with the instances in which persons are infected with measles three or four times within a few years; and if we weigh these phenomena with the established fact that the proportionate incidence of measles on those who have not had them diminishes rapidly after a certain age; the conclusion is inevitable that protection thrown over those who have once been infected is not the explanation of their escape from subsequent infection: or else that, conversely to the law in regard of other infective diseases, the protection afforded in respect to measles increases, instead of diminishes, by time. When, therefore, we see young children get recurrences of measles at a time when the older members of the family in the same house do not get recurrences, it is irrational to suppose that the latter escape because of their infection in childhood, unless it be that the degree of protection is higher in proportion to the length of the period from the former attack—that this particular immunity is augmented and intensified, in place of becoming more and more exhausted, year after year. But this reversal of the ordinary law of prophylaxis from infection has not been suggested. The immunity has not been regarded as exceptional. Either, therefore, the authorities have not seen that the nature of the protection claimed for

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