THE ABOLITION OF ZYMOTIC DISEASE.

THERE is a very remarkable group or family of bodily diseases which a theory respecting their nature has told us to call zymotic, and about which it is of vast importance that the public, no less than the medical profession, should possess the fullest attainable knowledge.

These diseases are distinguished by the following characters. They are all of them febrile diseases. They all run, naturally, a definite course, in definite though different periods of time. They all present, during some (usually definite) portion of that course, certain distinctive spots, markings, or eruptions on the surface of the body. As a rule, broken and proved by rare exceptions, they occur once only in the same person; in other words, one visitation of the same disorder protects the subject of it, for the most part, against the recurrence of that disorder. Lastly, they are communicable from person to person by contagion, and, as I venture to maintain, arise in no other way; and this quality, with their non-recurrence, forms the key to their supreme interest.

It is by the combination of these several features that the group is sharply marked off from other diseases which present some, or one, of them only; from simply contagious febrile diseases therefore, such as erysipelas, puerperal fever, pyæmia, and indeed from all other known human maladies.

There are not

They are not numerous, these zymotic diseases. more than nine or ten of them. Small-pox, chicken-pox, typhus fever, typhoid or enteric fever, scarlet fever, the plague, measles, hoopingcough, mumps-these belong to, and I think constitute, the group of diseases now to be considered. Few in number as they are, the group is fearfully destructive of human life, and to a still much greater extent prolific of human suffering, misery, and want. Several of them are, however, so familiar to almost every home as to be reckoned among the inevitable ills and perils of childhood; and hence, perhaps, the perception of important lessons which are furnished by the attentive study of them collectively has been obscured. Even of those which are mainly incidental to the earlier periods of life, some are justly held in the utmost dread by parents and nurses.

As life springs only from preceding life-as, according to the

verdict of exact scientific experiment, there is no such thing as spontaneous generation-so, under similar testimony, there is, now-a-days at least, no spontaneous origin of any of these specific disorders. It is an axiom not confined to the art of medicine that prevention is better than cure. Only of late years have we fully acknowledged that prevention is more easy also than cure. Let the cause of any disease be clearly discerned, and seized upon, impounded, and destroyed, and its prevention is achieved. In these serious and procreant disorders, happening, if at all, once only in a lifetime, the discovery, combined with the arrest, of their several producing causes, is equivalent to the possibility of their total abolition.

That the diseases of which I am treating are all of them contagious, and have now no other origin than contagion; that they never spring up, in our time, de novo-these are the main points which in this paper I shall endeavour to prove. If I succeed in my endeavour, I shall next insist that, by the enactment and rigid enforcement of judicious sanitary laws, these terrible diseases, with their terrible consequences, may finally be banished from this island.

The steps towards this most desirable issue require the cooperation of an enlightened public intelligence with the dictates and efforts of medical science; and this is my reason and excuse for thus addressing myself, in popular language, to the general reader, and not exclusively to the members of my own profession.

For what I am about to say I can claim no originality, nor shall I scruple to quote, when it serves my purpose, words which I may myself have used on some former occasions. I must premise also that all disorders which are contagious, or 'catching,' are transmitted from person to person by mutual touch; or by particles of matter floating in the air or adhering to clothes, bedding, walls, or furniture, and so brought near to, or in contact with, the body of the recipient of the disease. Such particles, many or few in number, constitute its contagium; more popularly they are called its germs, or, in plain and more accurate English, its seeds; and each disease in the group has its own proper and peculiar seed.

In offering some desultory comments upon certain of these disorders, I shall begin with small-pox, which is not only the most formidable of them all, but also a type or representative of the characteristics of the whole group. It is a malady which could scarcely be mistaken for any other; the very odour of the sick person's body is distinctive of it. Its horrible aspect, disfiguring consequences, and fatal tendency are so strongly marked that its presence has always been watched with affright by mankind in general, and with intense interest by the philosophic physician.

In the acme of the disease, when it is severe, the whole surface of the body is studded with a vast multitude of little pustules. A minute portion of the matter contained in any one of these pustules,

just so much as may suffice to moisten the point of a fine needle, is inserted, we will suppose, beneath the skin of a healthy man who has not been near the sick man. What follows this engrafting? Nothing, apparently, for several days; but then febrile symptoms burst forth, and by-and-by a crop of pimples appears, sprinkled over the skin, and these gradually ripen into pustules precisely like that from which the engrafted matter was taken.

The very same phenomena ensue when a healthy man enters the chamber of a person ill of the small-pox, and breathes for a certain time an atmosphere tainted with the emanations from his body.

The points to be noticed here are, (1) the manifest introduction of the virus into the bodily system; (2) its dormancy for a while— the occurrence, in medical language, of a period of incubation; (3) the breaking out, at length, of a disease identical in its symptoms and in its character with that of the first of the sick persons; and (4)-most surprising of all-the enormous increase and multiplication of the poisonous matter.

The whole process is in striking analogy with the growth of wheat in a field, or of other grain. We have the visible and tangible seed, the manifest sowing, the hidden germination, then the outgrowth and efflorescence, the ripening, the mature seed-time, the reproduction manifold of the original specific seed-every stage in the process of development occupying a definite period of time.

How this dire disease first arose among men it is difficult to conjecture. It has been supposed that it may have been originally derived from some disease in the camel. Its history leads to the settled belief that, while few persons are not readily susceptible of it, it never occurs now except from contagion. It does not appear to have been known in Europe till the beginning of the eighth century. No mention of any such distemper is to be found in the Greek or Roman authors of antiquity. Now, whatever may have been the deficiencies of these ancient physicians, they were excellent observers, and capital describers, of disease; and it seems to me scarcely possible that a disorder so diffusive, and marked by characters so definite and conspicuous, should have escaped their notice, or if known should have been obscurely portrayed in their writings.

On the other hand, Mr. Moore, in his learned and interesting History of Small-pox, has shown that it prevailed in China and Hindostan from a very early period-even more than a thousand years before the advent of our Saviour. That it did not sooner make its way westward into Persia, and thence into Greece, may be attributed partly to the horror which the complaint everywhere inspired, and the attempts which were consequently made to check its progress by prohibiting all communication with the sick, partly to the limited intercourse which then took place among the Fastern nations, but principally to the peculiar position of the regions through which the

infection was distributed, separated as they were from the rest of the world by immense deserts and by the ocean.

The disease is said to have broken out in Arabia at the siege of Mecca in the year in which Mahomet was born, i.e. in the latter half of the sixth century. It was widely propagated by his wars, and by those of the Arabs afterwards; and it is generally believed to have first found entrance into Europe at the time of the overthrow of the Gothic monarchy in Spain by the Moors, when, to avenge the well-known outrage upon his daughter, Count Julian called the Whensoever and wheresoever it came, it spread with fearful rapidity and havoc.

invaders.'

What is worthy of special remark is this: that while almost all men are prone to take the disorder, large portions of the world have remained for centuries entirely free from it, until at length it was imported; and that it then infallibly diffused and established itself in those parts.

Of the more modern history of the disease our knowledge is more precise and sure. It tends uniformly to the same conclusion.

There was no small-pox in the New World before its discovery by Columbus in 1492. In 1517 the disease was imported into St. Domingo. Three years later, in one of the Spanish expeditions from Cuba to Mexico, a negro covered with the pustules of small-pox was landed on the Mexican coast. From him the disease spread with such desolation that within a very short time, according to Robertson, three millions and a half of people were destroyed in that kingdom alone. Small-pox was introduced into Iceland in 1707, when 16,000 persons were carried off by its ravages-more than a fourth part of the whole population of the island. It reached Greenland still later, appearing there for the first time in 1733, and spreading so fatally as almost to depopulate the country.

Evidence to the same effect is furnished by the results of vaccination in some countries. To take one instance; vaccination was adopted in Denmark in 1801, and made compulsory in 1810. From that time small-pox disappeared altogether for fifteen years; whereas, during the twelve years preceding the introduction of the preventive disorder, upwards of 3,000 persons died of the small-pox in Copenhagen alone.

Now it is a very instructive fact respecting this disease thus rankly contagious, and arising from no other source than contagion, that when it is epidemic in any place, many instances of it occur which we can by no means trace to contagion. The late Dr. Gregory declared that of the numerous cases received into the Small-pox Hospital (to which he had long been physician) not one in twenty was capable of being referred to any known source of infection, the disease being ascribed by the patient to cold, fatigue, change of air, or some other innocent circumstance. About fifty years ago a prisoner, who had been for some time in solitary confinement in the

Penitentiary at Millbank, was seized with small-pox. There neither was, nor had been recently, any other case of the disease within or near that building. Here, apparently, was an instance of small-pox occurring de novo, independently of contagion. The mysterious fact was mentioned in some lectures of mine published in 1843. In 1860 I received from Dr. Pratt, a retired physician who had been in practice at Kennington, a letter which solved the mystery. While on a visit to his son in Wales, who was also a medical practitioner, he there fell in with a copy of my lectures, and read the remarkable case therein mentioned, and he wrote to me to explain it. Dr. Pratt's father had been the Resident Medical Officer at the Penitentiary, and was in the occasional habit of visiting his son at Kennington, who on one occasion took him to see, what is rare, a case of confluent small-pox in a man who had previously passed through the same disease. From his sick room the father returned straight to the Penitentiary and to the prisoner's cell, who some days afterwards sickened of the disease. The resident officer was aware that he had been the vehicle of the contagion, but did not dare to confess it, so strict was the Committee of the Penitentiary in enforcing the rule that, on pain of expulsion, he should visit no sick person outside the walls of the prison.

Another case, of like significance, may be quoted from Dr. Gregory's book.

In 1835 a child took small-pox in the country under circumstances which seemed to exclude all suspicion of contagion. She had never left the house for several weeks, the few neighbours who had called were free from sickness, and no small-pox existed in the neighbourhood. During her convalescence, a lookingglass was put into her hands, when she said immediately, 'My face is exactly like that of the child at the door from whom I bought the beads.' On inquiry it was found that some pedlars had passed through the village, and that the child, though she had never left the house, had been to the door.

Dr. Gregory remarks that had this child died, or been an inattentive observer, the origin of this attack of small-pox must, on the principle of contagion, have for ever remained mysterious.

Of the features common to all these disorders the most astonishing is that of their non-recurrence in the same person. Rare exceptions to this rule are common also to them all. Small-pox has even been known to affect the same person thrice. A painful instance of its occurrence for the second time forces itself upon my recollection as I write. My friend, the Reverend Dr. Jelf, Canon of Christ Church, and formerly Principal of King's College, London, died at Oxford of small-pox which he had contracted in Ireland. He had had the disease, by inoculation, in his youth.

Various explanations of this remarkable quality have been attempted. The simplest and most plausible, I think, is that which appeals to the analogy of the corn-field. Farmers have learned, by long experience, that they cannot profitably crop ordinary ground