The acutely accented (udātta) an (anaṅ) is substituted for the finals of 1. asthi 2. dadhi 3. sakthi and 4. akṣi, before the affixes of the Instrumental -3rd case and the cases that follow it, which begin with a vowel.,
Thus अस्थ्ना꣡, अस्थ्ने꣡, दध्ना꣡, दध्ने꣡, सक्थ्ना꣡, सक्थ्ने꣡, अक्ष्णा꣡, अक्ष्णे꣡ ॥ The words अस्थि &c have acute on the first syllable, the substitute अनङ् would have been also anudatta, but for this sutra. The stem getting the designation भ, we elide the अ 6.4.134, the udatta अ being thus elided, the case-ending, which was anudatta before, now becomes udatta 6.1.161. The stems ending with 'asthi &c' and though not neuter, are governed by this rule. As प्रियास्थ्ना ब्राह्मणेन, प्रियदध्ना ॥ Why 'before the affixes of the Instrumental and the rest?' Observe अस्थिनी, दधिनी ॥ Before affixes beginning with a consonant, we have अस्थिभ्याम्, दधिभ्याम् ॥,