It is a question how far a person who received the contagion, but in whom the disease has made no progress, can communicate it. Notwithstanding some ancient opi nions that have prevailed on this subject, it does not ap pear that the body alone can communicate it, at least if washed and shaved. It appears rather that the contagion is retained in their hair and clothes, as fomites, and that in this way the poison is communicated to others, long be fore the infected person suffers from it, or he escapes its action altogether. An exception, however, seems required respecting the body when suffering from the disease, or when in a febrile state, or in a heated or perspiring one; in which cases there seems no doubt that the contact of the naked skin will communicate the dis ease. All the excretions of the body, as well as the perspira tion and the breath, seem to be impregnated with the poi son at the same time, and to communicate it readily. That some persons have thought otherwise, will scarcely be considered an argument against this doctrine, when we know that this is the case with all other contagions, and when the fact is itself supported by the experience of in numerablc'persons, physicians, and others. Were it even otherwise, it would be a safe error to adopt this belief and to act on it ; nor is it easy to see what advantages those persons have proposed to themselves or the community by circulating doctrines that can only tend to danger ; actu ated apparently by vanity, or by the love of singularity, or opposition.
It has also been a question whether this contagion can be communicated by the dead body. Mons. Desgenettes thinks that it cannot ; but this is also a dangerous doctrine, This may be true enough in particular cases ; but in a dis ease subject to so many varieties, and often so' anomalous, it is better to regulate ourselves on a far wider experience. Whatever might have happened in the French Egyptian army, this opinion is contradicted by all the experience of Marseilles, and indeed by the examples in general that have occurred in Christian Europe. In these cases, it has always been found very difficult to get persons to bury the dead ; and the persons so employed always died speedily afterwards. At Marseilles, in consequence of this, the galley slaves were employed in this service, and they also died. The particular instances of this nature were nu merous ; and that the general principle is true of other contagions, is proved by the same having occurred in cases of typhus and of small-pox. These facts seem to prove two things, namely, that the poison is communicated from dead bodies, and that it is transmitted by the air.
It is unnecessary to inquire by which of these methods the poison is rendered most active in exciting the disease, and by what road it is conveyed into the system. It is sup posed that all contagion is introduced through the lungs or the skin, or both, and that it cannot enter by the sto mach, as it is destroyed by the digestive powers. The
same has been judged true of the plague, because dogs have swallowed the poison in this way without injury, when they received the disease by means of inoculation.
Substances and means of destroying the contagion have been anxiously sought after in all times ; and innumerable substances have been proposed and used. Fumigations and perfumes of all kinds have had their several reputa tions, as in other contagious diseases. These are ineffi cacious, to say the least ; and we have already shown, that, in some cases, they may be injurious. But we have no manner of doubt that this contagion, like all others, is de stroyed by the vapours of the mineral acids, the nitrous, muriatic, and sulphureous, and by oxymuriatic gas. The sulphureous acid, however, is not applicable to living bo dies, on account of its destructive properties to life ; but the nitrous and oxymuriatic have been found both effectual and admissible in all contagious fevers, and would doubt less be equally so in the plague.
These methods are, however, so little known as yet, even to physicians, except in a few places, and so much neglected by ordinary practitioners, even at home, that it is no cause for surprise that they have never been intro duced into the plague countries, as they unquestionably might, with advantage. In the Levant, exposure to a free air is the great expedient, both for things and persons. Water is also found efficacious ; but this cannot be used, except for particular sorts of goods and objects. For these it is usual, in all houses that are insulated in an infected place, to be provided with a vessel of water, or vinegar and water, through which every thing that comes into the house is passed. It is quite agreed, however, that water is as efficacious as vinegar.
This fact proves, that the matter of this contagion is dis solved or decomposed by water. So valuable is this prac tice, that it is proper to keep, in all wards and infected houses, buckets of water ; often changing them for fresh ones, and passing through them every object which has communicated with a patient, and which may be capable of conveying the infection.
It is probable also, since so many persons who are ex posed to the plague escape it, that there are constitutions and particular states of the system unsusceptible of the poison. This condition is the reverse of that which forms the predisposition to disease in this case, as in all others of contagious disorders. To investigate what these con ditions are, is a matter of great importance, as giving con fidence in the midst of danger, and as rendering us capable of availing ourselves of the services of such persons, always wanted in conducting the treatment and prevention of the plague. A few instances of this indisposition to the disease will not be misplaced.