The germs of infection are organic microörganisms, vegetable and animal—protozoa and bacteria.
The germs of infection once being lodged within the body cause certain reactions producing specific pathological changes and a variety of groups of symptoms which we know by the specific names of infectious diseases, e. g., typhoid, typhus, etc.
Among the infectious diseases known to be due to specific germs are the following: typhoid, typhus, relapsing fevers, cholera, diphtheria, croup, tuberculosis, pneumonia, malaria, yellow fever, erysipelas, septicæmia, anthrax, tetanus, gonorrhea, etc.; and among the infectious diseases the germs of which have not as yet been discovered are the following: scarlet fever, measles, smallpox, syphilis, varicella, etc.
The part of the body and the organs in which the germs first find their entrance, or which they specifically attack, vary with each disease; thus, the mucous membranes, skin, internal organs, secretions, and excretions are, severally, either portals of infection or the places where the infection shows itself the most.
The agents carrying the germs of infection from one person to the other may be the infected persons themselves, or anything which has come in contact with their bodies and its secretions and excretions; thus, the air, room, furniture, vessels, clothing, food and drink, also insects and vermin, may all be carriers of infection.
Sterilization is the absolute destruction of all organic life, whether infectious or not; it is therefore more than disinfection, which destroys the germs of infection alone.
A Disinfectant is an agent which destroys germs of infection.
A Germicide is the same; an agent destroying germs.
An Insecticide is an agent capable of destroying insects; it is not necessarily a disinfectant, nor is a disinfectant necessarily an insecticide.
An Antiseptic is a substance which inhibits and stops the growth of the bacteria of putrefaction and decomposition. A disinfectant is therefore an antiseptic, but an antiseptic may not be a disinfectant.