  We rewrite the standard 4-dimensional Dirac equation in terms of quaternionic
2-component spinors, leading to a formalism which treats both massive and
massless particles on an equal footing. The resulting unified description has
the correct particle spectrum to be a generation of leptons, with the correct
number of spin/helicity states. Furthermore, precisely three such generations
naturally combine into an octonionic description of the 10-dimensional massless
Dirac equation, as discussed in previous work.
