[624] Which form (rūpa) is internal (ajjhattika) and not the space element (ākāsadhātu)?
The eye sense base (cakkhāyatana) … the body sense base (kāyāyatana) — this is the form that is internal and not the space element.
Which form is external (bāhira) and the space element?
That which is space (ākāsa) and what partakes of space, void (agha) and what partakes of void, gap (vivara) and what partakes of gap, untouched by the four primary elements (mahābhūta) — this is the form that is external and the space element.
Which form is external and not the space element?
The form sense base (rūpāyatana) … nutriment consisting of morsels (kabaḷīkāro āhāro) — this is the form that is external and not the space element.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.