The word jagdhi is the substitute of ad 'to eat', when the affix lyap -- samāse'nañpūrve ktvo lyap [[7.1.37]] or an ārdhadhātuka kit affix beginning with a ta follows.,
प्रजग्ध्य 'Having eaten.' (प्र + अद् + ल्यप् = प्र + जग्ध् + य). So also जग्ध 'eaten' (अद् + क्त =जग्ध् + त).
The इ in जग्धि is merely for the sake of articulation and is not an anubandha, otherwise there would have been the insertion of the nasal न (नुम्). So also the इ in वचि &c, is merely for the sake of articulation. But अद् + क्त = अन्नः 'food' is an irregularity.
The employment of ल्यप् in this sutra indicates the existence of this Paribhasha. 'A bahiranga substitution of ल्यप् supersedes even antaranga rules.' Because in case this maxim did not exist, the substitution of जग्ध् for अद् before ल्यप् which is taught in this sutra, would follow already from the word किति (before that which is distinguished by an indicatory क) in this rule, i. e., जग्ध् would (by maxim 'that which is bahiranga is regarded as not having taken effect, or as not existing, when that which is antaranga has taken effect') first be substituted for अद् before क्त and ल्यप् afterwards for क्त.
Why do we say 'before affixes beginning with त'? Observe अद्यते 'is eaten.'
Why do we say 'before affixes having indicatory क'? Observe अत्तव्यम्.,