Medical hypodermic syringes are used to inject liquid into body tissues, or to remove substances like blood from the body.
Although syringes have been used for medical applications since Roman time, he first true hypodermic syringe with a needle thin enough to pierce the skin was not invented until 1853. This invention, by the Scottish physician Dr Alexander Wood, led to the development of more injectable drugs. At the time, only 2% of drugs at the time were injectable.
Prior to injection, syringes are held upside-down, tapped, and fluid is expelled. This is performed to remove air bubbles within the syringe that could cause an embolism if injected into the bloodstream. Syringes are typically made of plastic and are disposed of following use. Reuse of hypodermic needles can cause the spread of diseases, as has been problematic with HIV and hepatitis.