Helically symmetry is an exact generalisation of two-dimensionality and axisymmetry. The flow down a helical pipe is investigated under the assumption of helical symmetry. The implications for blood flow in the body are discussed. It is shown that the observed torsion of arteries may have fluid dynamical benefits. The blood is then replaced by a liquid metal, and it is found that the same flow can give rise to the spontaneous generation of magnetic field, known as a dynamo. Animations, but no experiments will be shown, in the absence of a volunteer for this surgical procedure.