ART. IX.-1. The Progress of Opinion on the Subject of Contagion. By William Macmichael, M.D. 1825.

2. Report from the Select Committee on the Doctrine of Contagion in the Plague. 1819.

3. Second Report from the Select Committee appointed to consider of the Means of Improving and Maintaining the foreign Trade of the Country. Quarantine. 1824.

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E FOE thought the events of the plague in London, in 1665, so full of fearful interest, that he wove them into a fictitious narrative, which does not however exceed in the distressing nature of its details the representations handed down to us by eye-witnesses. Dr. Hodges, who remained on the spot when Sydenham fled, and who, by appointment of the government, visited the sick from morning to night for many months, was clearly not a man of strong intellect, but he has left us an account of what he saw and heard, which, although rhetorical and affected in style, it is impossible to read without shuddering, and which we will not extract, because we might be accused of desiring to interest the feelings of our readers in the opening of a most important inquiry, when it is and ought to be our intention only to appeal to their judgments. This scourge of the human race has been believed, by the most judicious physicians who have witnessed its ravages, to be communicated from person to person, that is, to be contagious. Quarantine laws were therefore instituted. Before this,' as Lord Holland has remarked, the plague frequently devastated every country in Europe; but since then its returns have been comparatively rare.' Before the year 1665, Sydenham remarked that the plague visited this country only once in forty or fifty years; since that calamitous year this happy land has known nothing of its ravages; and so many generations have lived and died in security, that the clause in the Litany which implores preservation from plague and pestilence,' has lost perhaps some of that intense earnestness with which it must once have pressed on the hearts of the congregation in prayer. In this blessed, yet dangerous ignorance of the public mind, certain persons have started up, who affirm that the wisest of their forefathers, and the most experienced of their contemporaries, have been, and are, all wrong upon the subject-that the plague is not contagious-that quarantine laws ought to be abolished; and the public, and even our legislators, seem inclined to believe them. In these critical circumstances it is a duty, which some one ought to perform, to give a true and faithful account of this momentous matter to state the reasons which have satisfied the most competent judges that the plague is contagious-to expose the

ignorance

ignorance of those who are attempting to mislead the public, and the indiscretion of those who are inclined to believe them.

Some diseases become prevalent because their causes are so diffused as to affect many persons in the same place at the same time; other diseases become prevalent because the bodies of the sick give out a noxious material, which excites them in the bodies of the healthy. The former are called epidemic, the latter contagious diseases. The causes of epidemic diseases may be either deficient food, as in a general scarcity; or heat, or cold, or great vicissitudes from one to the other; or noxious states of the atmosphere, which are not perceptible by our senses, thermometers, or barometers. Some of these are understood, as marsh exhalations; others are involved in great obscurity. The human constitution is a delicate instrument, and can perceive qualities which our philosophical instruments and chemical tests do not enable us to detect.

The noxious matters produced by the bodies of the sick, which propagate contagious diseases from person to person, may be either something visible and substantial, as that formed in the pustules of small-pox, or the vesicles of the cow-pock; or something invisible, the existence of which is known only by its effects, as in the measles, the scarlet-fever, the hooping-cough.

The only way in which we can distinguish those diseases which are prevalent from an extensive cause acting at the same time on a number of people, from those diseases which are prevalent because they are communicated from person to person, is by certain circumstances in the mode of their diffusion. Now the circumstances by which we know that a disease is propagated by contagion, are these; 1st, that those persons are most liable to the disease who approach those affected with it, and that in proportion to the nearness of the approach; 2dly, that those who avoid intercourse with persons affected with the disease, generally or always escape it, and that in proportion to the care with which they avoid them; 3dly, that the disease is communicable from one to another by inoculation. If all these circumstances can be ascertained in the diffusion of a disease, and each with clearness and distinctness, we have all the evidence, which we can have, for believing that the disease is propagated by contagion. The proof is as complete as the nature of the subject admits. But the evidence for the belief that a disease is propagated by contagion, varies very much in degree in different cases; it may amount only to that which creates a strong suspicion-or it may amount to that which creates an absolute certainty. The most decisive single proof that a disease is contagious, is inoculation. Yet there are several diseases the contagiousness

tagiousness of which is undoubted, notwithstanding the absence of this proof; as, for instance, the scarlet-fever and hooping-cough. But there are occasions when it is necessary to act on the supposition that a disease is contagious, though the evidence for this opinion is far short of proof. The question is sometimes so difficult-life and health are so precious-and the precautions necessary to prevent the communication of the disease, if it should be contagious, comparatively such trifling evils; that a prudent physician will take care to be on the safe side, and use measures as if he was certain it was contagious, although to an indifferent person, weighing the evidence in the scales of mere speculation, it would appear only a bare possibility;—and here is the difference between a science, which makes its experiments on retorts and receivers, things of clay and glass, and a science, the subjects of which are flesh and blood, and health and life; that whereas in the former, the onus probandi lies on him who affirms the proposition, because the disbelief of it leads to no injurious consequence; in the latter, the onus probandi sometimes lies with him who denies it, because the disbelief would occasion the neglect of measures, which are harmless even if they be unnecessary, but the neglect of which may be fatal if they be essential.

Five-and-twenty years ago Dr. Wells published his belief that erysipelas was sometimes contagious. The following is one of several facts which led him to this opinion:-An elderly man died of erysipelas of the face. His nephew, who visited him during his illness, was soon afterwards attacked by, and died of, the same disease. The wife of the old man was seized with the same disease a few days after his death, and died in about a week. The landlady of the same house was next affected with it and then her nurse, who was sent to the workhouse, where she died. Dr. Wells mentioned his suspicion to several medical friends, among whom were Dr. Pitcairn and Dr. Baillie, and they related to him several circumstances which had led them to a similar opinion.

Lying-in women are subject to a disease called puerperal fever. In general it is of unfrequent occurrence, and out of large numbers scarcely one suffers from it. There are times, however, when this disease rages like an epidemic, and is very fatal. At these times circumstances sometimes occur which create a strong suspicion that the disorder may be communicated by a medical attendant or nurse from one lying-in woman to another. We give the following, out of many authentic instances. A surgeon practising midwifery in a populous town, opened the body of a woman who died of puerperal fever, and thereby contracted an offensive smell in his clothes: nevertheless, surgeon-like, he continued to wear them

them, and to visit and deliver his patients in them. The first woman whom he attended after the dissection, was seized with, and died of, the same disease-the same happened to the second and the third. At length he was struck with the suspicion that puerperal fever might be contagious, and that he was carrying it from patient to patient in his offensive clothes;-he burnt them, and not another of his patients was affected.

These are incidents calculated to produce a deep impression on the minds of those who witness them, and to create a strong suspicion that these diseases are, under certain circumstances, contagious. Yet if such evidence as this be contrasted with incidents of an opposite kind, in which free communication has produced no such consequences, and be mixed up with the ordinary history of the diseases, the whole statement would produce little effect no indifferent persons-on cold judges like a committee of the House of Commons.

Few persons believe that consumption of the lungs is contagious; it is a question which requires for its solution long and well-used experience. A physician in early, and even in middle life, is an inadequate judge; but there are English physicians of the greatest experience, the highest eminence, and the least fanciful minds, who are convinced that this disease is sometimes communicated from a wife to a husband, or from a husband to a wife, during the long and close attendance which its lingering nature and strong affection sometimes occasion. It is an opinion, however, which he who entertains can never demonstrate to be true to him who rejects it; yet is it a reason for every precaution which does not interfere with the duties of the healthy to the sick.

In medicine, and all but the demonstrative sciences, there is often light enough to guide our conduct, when there is not enough to gratify our curiosity; and therefore it is that practical men are often compelled to act on evidence, which would sound unsatisfactory in the statement. There is no paradox in saying, that he who can give a striking reason for every measure which he adopts, is, for that very reason, a bad medical adviser; because he must neglect many which are necessary and useful, but the reasons for which at the outset are extremely obscure. We cannot give a stronger instance of the difference between the evidence which is required to satisfy incompetent judges, and that on which physicians are often obliged to act, than that which is detailed in Dr. P. M. Latham's excellent Account of the Disease lately prevalent at the General Penitentiary.'

Having thus considered the signs by which we distinguish a contagious disease-the different degrees of clearness with which these signs show themselves-and the necessity there often is to

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act on the supposition that a disease is contagious, although the evidence for it is far short of demonstration-we may now go on to consider whether these signs are discoverable in the history of the plague in a sufficient degree to make it proper for us to act with respect to it on that supposition. Now whoever will carefully examine the accounts of the plague transmitted to us by those who have witnessed its ravages, will find ample evidence of the following truths:-1st. That it is most liable to affect those persons who approach patients affected with it, and that in proportion to the nearness of the approach: 2dly, that those who avoid all intercourse with persons affected with the plague, generally escape the disease, and that in proportion to the care with which they avoid it. There are few facts indeed in medical history for which there is such a mass of evidence as these; or on which the experience of past and present times is so uniform. The most remarkable examples are afforded by the introduction of the plague into countries which had long been free from it, in consequence of intercourse with places in which it was then raging. The clearness with which this intercourse has been often traced is truly wonderful, considering the many temptations which travellers or mariners coming from countries infected with the plague have to clandestine intercourse. Of such histories there are so many on record, that the difficulty is which to select: we will begin with the plague at Marseilles, in 1720.

For seventy years the plague had never visited this maritime city, when, on the 25th May, 1720, a vessel sailed into the harbour, under the following circumstances: She had left Seyde, in Syria, on the 31st of January, with a clean bill of health, but the plague had broken out a few days after her departure, and she had called at Tripoli, not far from Seyde, where she took in some Turkish passengers. During the passage, one of the Turks died, after an illness of a few days. Two sailors attempted to heave the corpse overboard, but before they had time to do so, the captain called them away, and ordered it to be done by the comrades of the deceased. In the course of a few days the two sailors who had touched the corpse fell sick, and speedily died. Soon after this, two others of the crew, one the surgeon of the vessel, who of course had attended the sick, were attacked with the same symptoms, and died. These occurrences so alarmed the captain, that he shut himself up in the poop during the rest of the voyage. Three other sailors subsequently fell ill in the same way, were put ashore at Leghorn, and died there; the physician and surgeons of the infirmary certifying that their disease had been a pestilential fever. The vessel arrived at Marseilles, and the crew and cargo were landed at the lazzaretto. Soon afterwards, the

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