  Recent operation of LOFAR by Hassall et al has produced severe constraints on
the size and altitude of the 40 MHZ emission region in this pulsar. It is shown
that these limits, given a limited number of unexceptionable assumptions,
demonstrate that an electron-positron plasma cannot be the source of the
emission. A physically-acceptable plasma source composed of protons and ions
arises naturally in pulsars having positive corotational polar-cap charge
density. Acceptance of this would greatly clarify the classification of pulsar
types within the whole.
