It is unnecessary to mention the symptoms of ague, as they are familiarly known. Convalescents are very liable to relapses, and many of those who have recovered from the more violent symptoms, are frequently affected, throughout the whole term of life, with very troublesome complaints, which arise from what is vulgarly known as ague cake, which is an enlargement of the spleen, an organ which lies near the stomach. Ague is very prevalent in the West Indies, America, Holland, and other countries which are much covered with wood, are ill drained, and liable to be periodically inundated. This disease displays none of the virulence of the malignant remittent fever already noticed, yet affects vast numbers in its peculiar localities, and not unfrequently leads to mortal results. The whole population of those fens and swamps in which ague is endemic, is generally affected at some period of existence, scarcely one person escaping. The effluvia which produce that disease are sometimes carried to a considerable distance, and there induce their peculiar distemper; and instances are well known, where effluvia have been conveyed to high grounds, where they have attacked the inhabitants, while those in the immediate neighbourhood of the source of these vapours, have escaped for the time. Ague is a much milder disease than the remittent fever, which springs from the same general source, viz. terrestrial effluvia, and which prevails in the East and West Indies, and on the coast of Africa. When and where intermittent fever only is produced, it would appear that the effluvia from the soil are less virulent and concentrated, and perhaps their activity is modified or tempered by a proportionately great quantity of watery vapour combined with them in the atmosphere, by the climate of the country, and by the constitution of the people. In this country, even so lately as half a century ago, ague or intermittent fever prevailed to a considerable extent, but is now almost unknown. In East Lothian many of the old inhabitants remember ague as being a common disease in that county. At present it is there unknown. In respect to this disease particularly, the health of the population of England has greatly improved, and it is well ascertained that the gratifying fact is chiefly owing to the country having been cleared of its superabundant wood, which prevented the land being readily dried, and which interfered with the due action of the winds, and to the speedy removal of water from the surface of the earth by draining, which is now so universally adopted. By draining, the water which formerly formed a receptacle for the decomposition of animal and vegetable remains, is now carried off, and with it the opportunity it afforded for the extrication of unwholesome vapours. CHAPTER IX. OTHER CASES OF PESTILENCE—FAMINE—UNWHOLESOME FOOD AND DRINK.