The geographical distribution of the disease is largely influenced by soil and climate. On dense, impermeable clays and hardpan subsoils, on river bottom lands, dried lake basins and deltas, rich in organic matter, and with the air driven out by water or gaseous fermentation products, the germ is preserved and propagated if once introduced. Thus it is common around the mouth of the Nile, and along the occasionally inundated banks of the Vistula and Danube, the Spree, Oder, Elbe, Rhine, Eure, Loire, Seine and Marne, and in England in the Fen district. On the rich, undrained, black soils of Siberia it is extremely prevalent and fatal. In the rich Genesee Valley, N. Y., the writer has seen 200 cattle in one herd and three human attendants attacked in the course of a fortnight, and in different meadows receiving the drainage of tanneries, the affection prevails every summer and autumn. It is much more prevalent in the rich lands of the Southern States and a widespread and deadly epizoötic prevailed in Louisiana in 1896. Where the soil is favorable, the germ may be preserved indefinitely, even in mountainous districts, and near Los Angeles, Cal., where the disease was introduced in imported sheep some years ago it has become permanently domiciled, on the dry ranges which have moist lands (Cienegas). When an outbreak occurs, the herds or flocks are usually moved to higher soil, and the carcasses being left unburned and unburied the infection is spreading year by year (McGowan, Morrison). _Etiology._ Nothing is more certain than that the disease is due to the introduction into the blood or tissues of the bacillus anthracis or its spores. These microbes are always found in the anthrax lesions and in the blood of the victim in the advanced stages. When grown in bouillon cultures to the hundredth generation they retain their virulence unabridged and determine the same lesions in the animals inoculated. When the infecting culture has been passed through a Pasteur filter the virulence is lost with the removal of the bacilli. The fresh anthrax blood containing bacilli but no spores when subjected to compressed oxygen (50 atmospheres) becomes noninfecting. The same liquid when boiled proves non-virulent. Certain conditions, however, contribute to the propagation and reception of the bacillus and these may be considered as accessory causes.