An instrument with a first conduit for emitting a first fluid from a first opening of the first conduit in an axial direction into a reacceleration zone and with a second conduit for channeling of a second fluid in the reacceleration zone in axial direction is provided such that active ingredient components, e.g. cells, of the second fluid are reaccelerated in axial direction as a result of the flow in the reacceleration zone by means of the first fluid that enters the reacceleration zone. A coaxial configuration of the first and the second conduit is preferred, because in doing so, around the first opening a shell jet of second fluid can be created that flows downstream in axial direction around the central working jet. In addition, a head for an inventive instrument and an application system with an inventive instrument is provided.
