ON CONTINUOUS MOLECULAR CHANGES (continued)

Whether the unknown cause of ague has been produced in the system of a previous patient, like the pus of smallpox and the eggs of tape-worm, or whether it has been produced externally, there is, at present, no sufficient evidence to show. In the case first supposed, the disease would be a communicable one, in the second it would not.

There is one circumstance which seems to indicate that the specific cause of intermittent fevers undergoes a development or multiplication within the system of the patient, -- it is, that a period of dormancy, or incubation, has been observed, in many cases, between the visit to the unhealthy locality and the illness which followed; for, as I have already remarked, every poisonous or injurious substance causes symptoms as soon as it has been absorbed in sufficient quantity.

The communication of ague from person to person has not been observed, neither has that of tapeworm, although in this latter disease there is proof of communication that hardly any one disputes, viz, the evidence that the creature is only found in the bowels, and the general principle, "omne vivum ex ovo." Supposing ague to be communicable, it may be so only indirectly, for the materies morbi eliminated from one patient may require to undergo a process of development or procreation out of the body before it enters another patient, like certain flukes infesting some of the lower animals, and procreating by alternate generations.

But, to return to those diseases which are known to be communicable, there are certain spots, more limited than the districts or localities previously mentioned, in which they find easy means of communication: -- I allude to the courts and allies crowded with the poor. It happens that there is generally no lack of offensive gases or disagreeable smells in these spots. Now it is well known that the gases arising from decomposition cause no fevers or other epidemic diseases, when they are made artificially in the laboratory. The same is true when they occur more naturally in the dissecting room; and it has also been proved that persons who get their living by working amongst decaying animal and vegetable matters are not more liable to these diseases than other persons.[17] Still there are some medical men, and a benevolent section of the general public, who attribute the excess of epidemic disease, found in crowded and poor localities, to what are called noxious effluvia. They cannot say that these effluvia predispose to the diseases, for persons from the country are often attacked too soon after their arrival in such places to allow of this mode of action, and they do not inquire whether peculiar facilities may not exist for the conveyance of specific virus from one person to another, but they hold that the noxious effluvia, together, perhaps, with an undefined something in the general atmosphere, may cause or increase any epidemic disease whatever; and, when a nuisance is discovered, the prevalence of any kind of disease at the place is said to be explained, although we are not told how. The gentlemen who hold these popular opinions do not seem to recognize specific causes of disease. They are, with respect to diseases, in the position that some of our ancestors were in with respect to plants and animals, when they believed in spontaneous or equivocal generation, and thought that dirt engendered vermin, and that mushrooms arose from horse-dung.

Nothing assists the communication of disease more than the want of personal cleanliness. This has been particularly observed in regard to plague, cholera, yellow fever, and continued fevers. There is one class of people who have no provision for cleanliness whatever -- namely, the vagrants,-- and they are notorious for contracting fevers, and carrying them about from place to place. It is the same with regard to cholera, when that disease prevails; and these people nearly always have the itch. Amongst the poor, who are less unfortunately situated, there is often very little cleanliness, and, when a number of persons reside, sleep, and eat in a small room, in which also the cooking is conducted, it is extremely difficult, when an individual is confined to bed by illness, to prevent his excretions being partaken of by all the inmates; indeed, with the uncleanly habits of many of the poor, this is altogether impossible. Under these circumstances we find that, when typhoid fever or cholera enters such a dwelling, it is very apt to go through the house, as the phrase is. It often attacks the friends also, who visit and eat and drink with the inmates, whilst the medical and clerical visitors escape. But when cholera or typhoid fever occurs in cleanly families, where the nursing, the cooking, the sleeping, and the eating go on in separate apartments, it is hardly ever found to spread.

It is not improbable that the specific cause of influenza and measles is drawn in with the breath, as these diseases affect chiefly the respiratory organs, and spread almost equally amongst all classes of the community; but the great aid that want of personal cleanliness lends to the extension of many communicable diseases points to another mode of communication; namely, that by swallowing the morbid material. It has been said that animal poisons do not act when taken into the stomach; but this is incorrect, for cantharides, the sausage and bacon poisons, and others, act when taken in this manner; and it should also be remembered that the virus of a specific disease is not strictly a poison, in the sense of that of the viper, for it is capable and requires to be multiplied in the system, before its effects appear.

There is evidence tending to show that typhoid fever, yellow fever, and plague, as well as cholera, are communicated by accidentally swallowing the morbid excretions of the patients, and that these latter may sometimes be conveyed to a distance with the drinking water, or other articles of diet, without losing their specific properties.[18]  Thus the communication of these diseases may be more or less direct or indirect, even when it takes place virtually in the same manner. The first authenticated case of cholera which occurred in London in the autumn of 1848, was that of John Harnold, a seaman of the steam ship Elbe, newly arrived from Hamburgh, where the disease was prevailing. He died in a lodging at Horsleydown, near the river. The next case was that of a man who came to lodge in the same room; and a few hours afterwards cases occurred in Lower Fore Street, Lambeth, and in White Hart Court, Chelsea, amongst people who had no water for drinking or any other purpose, except what was obtained by dipping a pail into the Thames. Thus the cholera poison from John Harnold appeared to be distributed like the seeds of a riverside plant, some of which germinate and grow up by the side of their parent, whilst others are conveyed some distance by the tide, and take root on another part of the shore.

Those sudden extensions of cholera, which are called outbreaks, were in many cases due to the mixture of the cholera-evacuations with the water used for drinking and preparing food. This was shown to be the case in the Wandsworth Road, in Bermondsey, and in Rotherhithe, during the summer of 1849.[19] It has been often argued that sudden outbreaks of cholera are incompatible with its propagation from person to person, but we know of no circumstances to restrict the number of persons who may receive the disease from one or two patients, under favorable circumstances for the distribution of the morbid matter. There were a few cases of cholera present at Kurrachee, previous to the outbreak of the disease in 1846, which has been often alluded to; so that, like the outbreaks in England, it was in reality but an extension of the malady.[20]

Medical men are naturally apt to form their opinions respecting the communication of diseases from their own experience, rather than from the general history of the maladies, and thus they believe in its contagion, when a disease, such as cholera or typhoid fever, generally spreads directly from person to person in their practice; but in districts or connections in which the indirect and less obvious mode of contracting disease is, from physical causes, the prevailing one, they are apt to become what are called non-contagionists.

It may very fairly be asked whether communicable diseases do not sometimes arise spontaneously -- that is, from other causes than their communication, just as ordinary combustion, putrefaction, and some other continuous molecular changes, very often commence anew, from various causes, without any continuity with previous changes of the same kind, and it is not improbable that some communicable diseases may arise, so to say, spontaneously.  The erysipelatous inflammation, for instance, which attacks the neighborhood of wounds, probably arises now and then without being communicated; otherwise we must suppose the material which causes it to be almost as widely diffused as the spores of some of the fungi. There is, however, great reason to believe that the larger number of communicable diseases never arise from any other cause than the communication of the specific virus from a previous .patient. Dr. Watson has given very strong proofs of this, in regard to smallpox, in his lectures, and proofs almost as strong might be adduced in respect to other diseases. We know very well from history that the plague spreads fearfully in this country, when it is imported, and, if it ever arises spontaneously, why should we have been without a case of it for nearly two centuries? We sometimes hear it asked, "Then how did the first case arise ?" The question might as well be asked with respect to the first tiger or the first upas tree; but our ignorance of the first origin of natural phenomena need be no obstacle to the investigation of their present causes.

I have just said that some communicable diseases, such as erysipelatous inflammation, may possibly arise, now and then, without contagion; but there is an opinion held by some men of eminence to which it is very difficult to assent: -- I allude to the doctrine that a disease caused by malaria, which is supposed to be produced out of doors, without any regard to a previous patient -- that such a disease can, under certain circumstances, take on contagious properties. For instance, many persons believe that yellow fever, as it occurs, for example, on the western coast of Africa, is caused by malaria or marsh miasmata; and when they have been convinced by such facts as those adduced by Dr. M'William respecting Boa Vista, that this fever is communicated from person to person at another place, instead of reviewing their previous opinion, they try to reconcile it with the new conviction, by supposing that the disease has taken on contagious properties which it did not previously possess. Now this amounts to nothing more or less than supposing that some material produced in marshy ground, without any connection with the human body, can be reproduced and grow in the system of the patient. I believe we know nothing in nature analogous to this, and it is therefore an opinion which should not be adopted till there is strong evidence in its support. It is most likely that yellow fever was always a communicable disease.

With respect to preventing the communication of disease, it is worthy of remark that there are two diseases whose mode of propagation is well known to almost everybody, and almost everybody has it in his power to avoid them -- I allude to syphilis and the itch. It will perhaps one day be seen whether other communicable diseases may not be as easily avoided, when their mode of communication is known. In the meantime it is very well ascertained that cleanliness is a great protection against many of them, as are also space, daylight, and ventilation. The cleanliness which, it may be observed, cannot be attained without sufficient space and daylight, should not be a cleanliness for mere appearances; it should be a rational cleanliness, like that by which the chemist keeps his tests pure and distinct, and the farmer his land free from weeds. There should be not only personal cleanliness, but cleanliness in every department of the household -- cleanliness in builders and owners of house property, to deter them from sinking wells so near to cesspools and drains, that their contents may percolate without proper filtration -- cleanliness in water companies, to prevent them from sending water containing sewage to their customers, as was done on the south side of the Thames till very lately -- and cleanliness in sanitary reformers, to deter them, in their fear of offensive effluvia, from abolishing cesspools and having the sewers flushed, and thus sending all the recent excrementitious matters into the rivers, until they have ascertained that people are no longer obliged to drink the water of these rivers.

Some great improvements have been made lately in the way of cleanliness. The model lodging-houses are instances of this kind, and so are the public wash-houses, which enable poor persons to wash the foul linen of a sick person without being obliged to do it amidst the plates and tea-cups, the bread and meat, and other provisions of the family.

The prevention of epidemic or communicable diseases is a subject which deserves increased investigation. These diseases influence the life, the death, and the numbers of the human race, more than all other causes. The very learned physician Dr. Gordon Latham is of opinion that the downfall of the Roman Empire was due as much to several severe epidemics as to any other cause; and although I am far from apprehending any such calamity now, as "a speedy return of the middle ages," there are circumstances occurring which deserve our vigilance. The increased and more rapid traffic between nearly all parts of the world, especially that by means of large steamships, renders it probable that diseases, hitherto confined to particular divisions of the globe, may gain a wider range, and thus increase the number of diseases in nearly every country. For now, when the commercial interest and influence preponderate over every other, the day is gone by for strict quarantine, which, indeed, was ever but a doubtful measure, as it was liable to evasion, and could not be enforced on the smuggler.

The question of contagion in various diseases has often been discussed with a degree of acrimony that is unusual in medical or other scientific inquiries. The cause of the warmth of feeling that has been displayed has, in most cases, probably been unknown to the disputants. It is the great pecuniary interests involved in the question, on account of its connection with quarantine. In the preface to his work on the Plague of Aleppo, Dr. Russell says, -- "But however indisputable the fact of the plague being contagious may be deemed by modern physicians, it may be remarked that it has been strongly opposed, as often as the subject of quarantine has fallen under the deliberation of the legislature; and the public, at such times, have been constantly pestered by an inundation of pamphlets, which, without advancing anything new, merely retailed arguments which had long before been refuted."

Since 1791, when the above was written, the commerce of this country has increased a hundredfold, and for every ten thousand pounds that were jeopardized by quarantine then, a million is in danger now.

The chief arguments against the communication of disease have been shaped according to the belief that, if communicated at all, it must be by contact with the patient, or by effluvia from his person, clothing, or bedding. The communication of disease by accidentally swallowing morbid excretions, to which attention has more particularly been called of late, considerably alters the ground of debate; but if the doctrine of the communication of disease must involve quarantine, it will always be very unpopular, and its advocacy extremely unpleasant to the medical man, however conclusive the proofs of it may be. This of itself is a reason for endeavoring to ascertain how far communicable diseases of all kinds can be prevented by measures of detail which do not interfere with commerce.

The mode of propagation and the means of prevention of epidemic diseases require, as I said, increased investigation; and if any inducements were wanted to stimulate my present audience to that inquiry, it would only be necessary to remind you that, by investigating one of these diseases, a former Fellow of this Society was enabled to make the greatest discovery that has ever been made in the practice of medicine, and to render the greatest benefit to his species which they have probably ever received. I need hardly say that I refer to Jenner.

THE END.