> > Latin
> > muscus
>>Proto-Germanic *waskan
> > 'wash',
> I take it then that these are indeed the
> only forms for *m-sk and *w-sk.
Roots of the form C-sC are not common in PIE (about 25-30 examples,
depending how you count), and normally we would see them as root C-s plus an
extension. For example, Latin muscus is taken as *meus- with a guttural
extension The same thing applies to Latin musca "fly, midge" (<
*mu:s -k-).