>>Instrumental: Sreitberg also notes forms in *-mi and *-bho
>In Germanic?
"Next to the instrumental in -e:/-o: there appears to exist in germanic also
some instrumental forms from -mi, cf Fr Kluge, Pauls Grundriss 1:386 Notes.
One can well see OIce at hofDum, OE aet heafdun, OHG zi houbitum as
representatives of this form. The main area in which this form is found is
outside the -e/o stems.
With the PIE instrumental suffix -bho, a by-form with lengthened vowel
could appear. Then could the Gothic adverbs in -ba eg ubila-b, balTa-ba be
understood as old insturmentals .They cannot be taken as ablatives, because
of the short vowels."
Peter