It is the presence of these specific microbes in the fluids or solids of the system which constitutes the disease, and for the cure of the same the intelligent physician of to-day looks less to medication, and more for some agent that will destroy the germ, neutralize its effect, or render the body tolerant thereto. Out of the knowledge of disease germs has grown the great era of antiseptic surgery, inaugurated by Sir Joseph Lister, about 1865. Carbolic acid, the bichloride of mercury, and formalin are the most efficient weapons against the dreaded microbe. To-day every surgeon in the civilized world sterilizes his knife, and conducts the treatment of wounds and all operations by antiseptic methods, in accordance with a knowledge of the deadly influence of the ubiquitous microbe, and the result has been to so reduce the risk to life that even capital operations are no longer coupled with the apprehensions of death. Every hospital, board of health, and organized medical and sanitary body predicates its laws and modes of treatment upon the principles of bacteriology. _House Sanitation._--The permanent home of the microbe is the sewer, and sanitary plumbing, designed to exclude from the house the germ-laden and disease-breeding gases from the sewer, constitutes one of the great advances of the century. About 3,500 patents have been granted for water closets and bath appliances, and about 900 patents on sewerage alone, the most of which are directed to improved conditions of sanitation. [Illustration: FIG. 179A.--STREET CONNECTIONS, MODERN SANITARY HOUSE PLUMBING.] [Illustration: FIG. 179.--MODERN SANITARY HOUSE PLUMBING.] An illustration of the plumbing and sewer connections of a modern house is given in Figs. 179 and 179A. The sewer pipes are shown in solid black, the unshaded pipes (in outline only) are air ventilation pipes, the single black lines are cold water pipes, and the dotted lines hot water pipes. The important sanitary feature in modern plumbing is to keep all sewer gas and disease germs out of the house. For this purpose traps have long been used under the wash basins, closet hoppers, and sinks; but the back pressure of sewer gas would sometimes bubble through the trap into the house, and besides the water in passing out from a basin would sometimes, by a siphon effect, pass entirely out of the trap, leaving it unsealed. Both these results are prevented by the air ventilation pipes which connect with the discharge side of every trap in the house and lead to a stack extending out through the roof. This prevents pressure of sewer gas on the water seal of the trap, destroys the siphon action of the trap and allows a circulation of air to be taken in from the sidewalk on the house side of the running trap and through the sewer pipe of the house, and thence through the air vent pipes to the roof.