For the i and u of the stems called ghi -- yū stryākhyau nadī [[1.4.3]], guṇa is substituted in the Dative -4th Case, Ablative -5th case and Genitive 6th-Case singular.,
As अग्नये, वायवे, आग्नेः, वायोः, (VI. I. 110). Why of घि stems? Observe सख्ये, पत्ये ॥ Why in the Singulars of the Dative, Ablative and Locative only? Observe अग्निः-भ्याम् ॥ The word case ending (सुपि) is understood here also, as the counter-examples are पट्वी, कुरुतः ॥
The word पट्वी is formed by adding ङीष् to पटु 4.1.44. ङीष् is not a case-affix, though it is ङित् and is added to पटु which is घि ॥ कुरुतः is no proper example: for though तस् which is added to कुरु is ङित्, it is only so by atidesa (सार्वधातुकमपित्), and moreover कुरु is not घि ॥,