The cause of this barbarization was thus, upon the whole, simply the necessary process of corruption which is continuously eating away every language, where its progress is not stemmed by literature and reason; only in this case indications of what has elsewhere passed away without leaving a trace have been preserved in the writing of sounds.

The circumstance that this barbarizing process affected the Etruscans more strongly than any other of the Italian stocks adds to the numerous proofs of their inferior capacity for culture.

The fact on the other hand that, among the Italians, the Umbrians apparently were the most affected by a similar corruption of language, the Romans less so, the southern Sabellians least of all, probably finds its explanation, at least in part, in the more lively intercourse maintained by the former with the Etruscans, and by the latter with the Greeks.
Notes for Book I Chapter XIV 1.

I.II.

Indo-Germanic Culture 2.