[611] Which is that form (rūpa) that is internal (ajjhattika), not the form base (rūpāyatana)?
The eye base (cakkhāyatana) … the body base (kāyāyatana) — this is that form that is internal, not the form base.
Which is that form that is external (bāhira), the form base?
That form which, derived from the four primary elements (mahābhūta), is the appearance of colour (vaṇṇanibhā) … this too is the form element (rūpadhātu) — this is that form that is external, the form base.
Which is that form that is external, not the form base?
The sound base (saddāyatana) … edible nutriment (kabaḷīkāro āhāro) — this is that form that is external, not the form base.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.