Note 158 — VIII Language as a Historical Product: Phonetic Law

Footnote 158: Z is to be understood as French or English z, not in its German use. Strictly speaking, this “z” (intervocalic -s-) was not voiced but was a soft voiceless sound, a sibilant intermediate between our s and z. In modern North German it has become voiced to z. It is important not to confound this s—z with the voiceless intervocalic s that soon arose from the older lisped ss. In Modern German (aside from certain dialects), old s and ss are not now differentiated when final (Maus and Fuss have identical sibilants), but can still be distinguished as voiced and voiceless s between vowels (Mäuse and Füsse).