Naturally voided body fluids obtained noninvasively include urine, saliva, sweat, pus draining from wounds, serum draining from burns, and, for purposes of continuity, feces (arguably not normally a fluid except in the stomach and part of the small intestine). The chemical composition of these substances provides important information that is used in diagnosis of infections, cancer, hormonal diseases (e.g., diabetes mellitus, thyroid diseases, diseases of the adrenal glands, gastrointestinal disorders, liver cirrhosis, etc.). Much diagnostic information can also be obtained from the blood, but unless it is taken from a hemorrhaging wound, its collection is certainly invasive, and therefore its consideration in this chapter is proscribed.