CHAPTER X.

Mode of infection-"Law of efficient air-contamination "-Conditions

for contamination-Contributories-Excreta-disposal system-Contagium vivum may be concerned in causing the disease indirectly— Measles viewed as a 66 straw fever."

THE kind of vegetation which, it is assumed, causes measles having been dealt with as well as the data admit, we come to the consideration of the modes in which the straw fungi cause efficient infection.

As the spores of the moulds have been found to be everpresent in the atmosphere below certain altitudes, and to be present in vast numbers in some localities, and as the straw mildews proper are also largely represented in the air of rural districts at certain times, it has to be shown how these forms may be implicated as the veræ causæ of measles. For that infection should be effected by means of spores of which we daily take in enormous numbers without being infected, has been objected to on the ground of incompatibility. When Hallier announced that Mucor mucedo was the infective agent in measles, but omitted to point out how the species could be an efficient infective agent, he not only had the botanical arguments touching his radical errors in cultivation against him, but it was said that if the Mucor were the specific cause of measles, no one could long be free from measles. But the difficulty of reconciling this universal prevalence of the infection with an entire absence of the disease is not insurmountable.

Every one knows now that the efficiency or otherwise of many of the specific infections is a matter of dose; or rather

perhaps the fact is recognised to the full only where inoculations with infective material are concerned. But if the law obtains with artificial introductions, it must hold good with natural inhalations of a given pathogenic vegetation; and the question therefore is how people get a full dose of the measles poison while living in their usual way.

It will smoothe the future course of the argument to submit here what may be called the law of efficient contamination of the air with infective material. It would be difficult to formulate a general law applicable to all infections, with present materials, and there is no occasion to attempt it. Pro hac vice the law may be put in this wise :-Spores that are innocuous when inhaled by man under ordinary or natural conditions, may become noxious to him when from any cause their numbers are increased to a certain extent within a given volume of air which he is called upon to breathe for a certain length of time. The standard of efficient contamination will vary for individuals according to the degree of their exposure to the air or to the number of hours they may have to inhale it continuously or intermittently during the twenty-four day after day; and according to their age, health, &c. And the efficiency of the contamination will also vary with the quality as well as with the quantity of a given form in the air.

This brief exposition of what will be understood here by efficient contamination will serve. As, however, many authorities believe that measles are (frequently communicated from person to person instantaneously, it is not likely that the view embodied in the law of efficient contamination will be readily assented to; yet, granting the "straw mildew theory," it will be seen that, ex hypothesi, there is nothing strained in the assumption.

Regard being had then to efficient contamination, it may readily be apprehended that although large numbers of the spores of the straw fungi are constantly being carried to the airpassages, their numbers nevertheless are not sufficient to induce efficient infective processes, or to constitute a full dose. Hence efficient contamination, qua measles, does not happen in the

open air. Morbilloid complaints occur from contact with, and from exposure to, the atmosphere surrounding cereals and other grasses during "rusts," "blights," &c.; and complaints still more nearly allied to, or more nearly resembling, ordinary measles, sometimes come of chaff-cutting and handling musty straw. But an efficient contamination of the air by the forms which go to cause the affection known as normal measles is not brought about away from habitations. A full dose is to be had only in the house. And this brings us to the conditions under which straw may be so placed in the house as to ensure that, sooner or later, the residents shall get a full dose.

It is obvious that all kinds of straw (wheaten, oaten, rye, &c.,) all grasses, sedges, rushes, flax, heather, and in short all forms of vegetable fibre slept on by different peoples, are liable to be attacked by the common moulds, and will be more or less overrun by the different species in proportion to the amount of foreign matter added to the bedding, and according as the conditions are conducive or inimical to the growth of the species. (It is no less obvious that hair-mattresses, blankets, &c., may also become converted into matrices for these common forms.) Besides these species, others peculiar to the cereals, &c., it is assumed, will develop under certain conditions. Then again the spores of foreign or adventitious fungi may be in the straw slept on; but these may be left out of consideration now. Not to delay over details, the question before us here is whether the ordinary quantity of straw used in their bedding by Europeans has furnished a sufficiently large field for the growth of such an abundance of the "straw fungi" as to have led, at any time, to efficient contamination of the air of any of their bedrooms. Is it to be supposed that the amount of straw, whether altogether uncovered, whether loosely enclosed in ticks, or whether closely packed in paillasses, will have supported so many forms and given off so many spores as to have created a local malaria of such value that those exposed to it for a given time have become affected with measles?

The remainder of the argument will be an attempt to show that this question must be answered in the affirmative, inasmuch

as there is no other sufficient explanation of the causation of measles. Before going further, however, it will be as well to refer to certain accessories or contributories to the air poison given off from straw bedding; and it will be borne in mind that efficient contamination of the air of a room from any source may turn upon the size of the room, its ventilation, its cleanly or dirty state, upon the length of time the conditions favourable to the growth of fungi last, and indeed upon a host of conditions that have been only remotely glanced at, or have not yet been touched upon.

Taking the bed as the principal source of measles infection, the contributory sources are an insanitary state of the bedroom and of the habitation generally, but above all defects in the excreta-disposal system of a house. All these faults may be acces sories to infection, either before or after the fact, or both. They may hasten the onset and facilitate the spread of an outbreak ; and in some instances the excreta-disposal system may have been instrumental in causing measles in houses where the straw bedding had not been affected by the straw fungi, and possibly, under very exceptional circumstances, in houses in which straw bedding is not used. All animal and vegetable matters left about habitations may be overrun with the fungi at epidemical seasons; and at other seasons, provided the purely local conditions are favourable. General insanitary conditions on a large scale-such extreme degrees of filth in habitations as provide rich and abundant soil for the extension of the straw fungi— are to be met with only in the foulest dens. But defects in sewage may involve both high and low in an epidemic, or may cause sporadic cases of measles among rich and poor.

It is not necessary for my present purpose to enter far into this immense subject. All that need be said is that wherever the excreta-disposal system, of whatsoever kind, allows of, or provides for, a free surface of fæcal matter at any part of it, it is an inference that that surface, kept moist, will give subsistence to the straw fungi, either when their spores are carried to it by the air, or when they are conveyed to it in the dejections of measles patients. It is almost superfluous to say that even assuming an

unusually large surface of this contaminated material to be exposed within a house or its precincts, and further, assuming the vegetation on it to be exceptionally luxuriant, it is not to be supposed that the resultant contamination of the air will practically, per se, cause the efficient infection of residents in the house, unless in extremely rare instances. The chief danger of all insanitary conditions in respect of measles consists in their passing the infection on. The excreta-disposal systems particularly may be the means of spreading the disease by permitting of the establishment of new plantations of the specific vegetation in all directions-as, for example, when boarding-schools are broken up because of measles. Of the "sickening" and convalescent pupils sent home a proportion may infect a closet outside, or the sewage pipes inside, a house. And the introduction of the vegetation in this way may be the turning point. Spores from it may determine a fungus growth on the paillasses which otherwise would not have occurred.

The nasal, bronchial, and other discharges, the branny particles, the clothing of patients, &c., may occasionally be contributories to the spread of measles; but the point need not detain us, for though contagium vivum, either passing directly from person to person or carried indirectly from one to another by way of fomites, is still held to be the one material, the sole agent, by which the disease has been transmitted from remotest times, I apprehend that this venerable belief cannot much longer be sustained. For the part contagion really has in the extension of measles will soon be found to be a very insignificant one. And even in the rare cases in which it is operative, the inference is that it spreads the disease indirectly-not by passing from the sick to the healthy and straightway causing infection, but by the reversion of the parasitic vegetation contained in the discharges of the infected to a more normal course of development, and thus leading to efficient air-contamination. And of all the discharges of the body the most likely to bring about this result are the alvine; and these are the least suspected and least regarded, and, indeed, are not looked at or dealt with as holding contagium vivum. These may, as