Ground waters, including wells, in some lo calities are infested with crenothrix at the num ber of 20,000 per cubic centimeter and with sim ilar organisms, where iron and manganese are found. The crenothrix flourisnes in waters impregnated with iron and erenothrix itself se cretes iron and clogs water pipes. Many other species have been found in ground waters, though they may not all be pathogenic. Some time ago the Massachusetts Board of Health tabulated those found in ground waters. In re cent years, possibly from China, there have been imported with livestock, or by means of their bides, the dread anthrax spores (B. authrocir) discovered by Robert Koch in 1876, which have been discharged from tanneries into rivers. They arc immune to the ordinary agencies used for the sterilization or purifi cation of water supplies. Turneaure and Russell reported in their 'Public Water Sup plies' that in Medford, Wis., a well was con taminated by surface water draining into it from a field, where cattle had died of anthrax or splenic fever.
The bacilli Otani (B. felons) and many other species have been discovered in raw river water. In 1900, George C. Whipple compiled data showing the relative abundance of diatomacerr, chorophycetr. cyouothyretz and Protozoa in 57 lakes, ponds and storage reservoirs of Massa chusetts. Consult Whipple's 'Microscopy of Drinking Water' pp. 139-141. None of such waters were entirely free from some one or more genera of such organisms. They may be considered as fairly representative of all surface waters.
As a result of thesrevalence of pathogenic bacteria in water ies, waterborne diseases are many and inearthose already mentioned and many other intestinal, tubercular and other disturbances. It is the aim of modern research to prevent all such diseases and to that end new processes for the purification of water sup plies have been perfected. New standards of purity and wholesomeness have•been established to which water supplies must conform before they are considered safe for potable uses. Some of these will be considered in this article, which will comprise several subtitles.
Primitive Cossditionsw—In the con ditions of society the water supply of a terri tory received but little attention. The early in habitants of the world were more interested in its availability and abundance than they were in its quality. Accordingly the most populous settlements were those along oceans, seas, gulfs, bays, lakes, rivers and watercourses generally. Early palzolithic remains have been found along the Thames. In the Stone and Bronze ages dwellings for human habitation were built on poles in the lakes of Switzerland, the British Islands and elsewhere and mounds were con structed along the coasts in Scandinavia. Their
occupants were thus abundantly supplied with water as well as protected from the ferocity of wild animals. Primitive peoples, however, knew little or nothing about the animal and vegetative organisms, in surface, running or stored-up water. At first there was little, if any pollution of watercourses by human agen cies. The early inhabitants supplied their needs from nature's inexhaustible reservoirs without fear or even the knowledge that water in any of its manifold forms might be unsafe for do mestic or for general potable uses. That is a matter of recent deduction from the slow dis covery of species of pathogenic bacteria, in sur face and other polluted waters. Some of these develop and propagate readily when taken into the human system as do bacilli coil core muftis.
Prior to the 19th century of our era there are few extant records of the ravages of dis eases and the destruction of human life, attrib uted to the potable uses of unwholesome water. Many wasting fevers„pestilences and plagues are recorded in history pnor to the discovery of the deadly species of microscopic organisms in con taminated water, but their causes were unknown. As the population increased and extended from watercourses inland, tanks, storage reservoirs and canals were constructed as they were in As syria, Babylonia, Egypt and China. The sources of the Tigris and Euphrates and the waters of those ravers themselves were con veyed through a network of canals to water the many cities of Mesopotamia whose water jars have been found at Nippur and elsewhere. Khammurabi provided for the protection of some of such canals in his Code of Laws, pro mulgated 2250 ac. Egypt was watered by the Nile, whose constant flow was maintained by drawing upon the impounded waters of Lake Moeris. Asia Minor had many eurings, notably those in the valley of the Mznander. The Ara bians utilised extinct volcanic craters as reser voirs for the acaimulation of watera: Greece had its rivers, springs and infiltration galleries. Rome had its lakes, springs, aqueducts. reser voirs and rivers. Carthage and Palestine had their wells, cisterns and pools, supplied by mountain streams. India had its riven, canals and reservoirs. All those ancient peoples and also the Chinese had their deeply driven wells, which supplied their best waters. Herod ono. Hippocrates, Strabo, Pliny and others rote tArl the water supply of various countries.