nerve gas, any of several poison gases intended for military use, e.g., tabun, sarin, soman, and VX. Nerve gases were first developed by Germany during World War II but were not used at that time. These gases generally cause death by asphyxiation, often preceded by such symptoms as blurred vision, excessive salivation, and convulsions. Physiologically, the toxic effect of nerve gases arises because they inactivate the enzyme cholinesterase, which normally controls the transmission of nerve impulses; the impulses continue without control, causing breakdown of respiration and other body functions. Atropine is an effective antidote against most nerve gases. See also chemical warfare.