The operation of vitiated air in the production of disease is often very much assisted by the presence of other prejudicial influences. It has been frequently remarked that one stroke of misfortune seldom comes alone, and that observation holds with striking force in reference to the causes of disease. One cause of disease produces another, which in its turn generates another, and so on, till the tendencies to, and the excitants of, pestilence, are so strong and so numerous, that whole communities are affected, one after another. It not unfrequently happens that the predisposing source of some of the most severe visitations of the most virulent distempers, is the want of food, which generally depends on the exorbitant prices of provisions, raised either by the arbitrary regulations of rulers, or by comparative scarcity. The total or almost total want of food is calculated to bring about, very shortly, a mortal result, from exhaustion or from sinking of the powers of the system. When food is not withheld altogether, but is only given in sparing quantity, in an amount insufficient for the maintenance of the body in vigour, a condition of the system is induced, in which the functions are imperfectly performed, in which the blood and the various humours become universally prone to morbid change, and in which there arises a great tendency to disease of a low or asthenic character. If, under such privation, vitiated air be present, whether arising from men in health, but uncleanly or crowded in close apartments; from the clothes, or excretions of the sick; or from terrestrial effluvia; it will give form to disease, will act as a spark amid fuel, and will shortly convert any predisposition to sickness that may exist into reality itself. In those suffering under scarcity of food, there is generally experienced great depression of mind, which is hurtful in itself and injurious by preventing sufficient exertions for the maintenance of cleanliness: there is an inability to procure requisites for the purpose, and when, perchance, they are obtained, there is too often too much apathy or supineness to admit of their being used. That miserable individual who is famishing, who is so unfortunate as to hear his helpless children call for bread, which he, alas, cannot give, who himself is exhausted and sinking with want, is seldom found to be very solicitous about cleanliness. A mother so situated will, in her misery, amid her actual sufferings, and with the dark yet immediate prospect of further hardships, forget the necessity or disregard its call; of removing impurities from her hut, of retaining the persons and clothes of her family clean—and of washing the furniture, the walls and floor of her pestilence-haunted cabin. In such a situation, cleanliness is neglected and impurities of all kinds accumulate which emit effluvia, to add to the number of the causes of gradual death impending over a family thus situated.