A simple illustration will throw light on this conception.  Let us suppose that two neighboring and unrelated languages, A and B, each possess voiceless l-sounds (compare Welsh ll).  We surmise that this is not an accident.  Perhaps comparative study reveals the fact that in language A the voiceless l-sounds correspond to a sibilant series in other related languages, that an old alternation s:  sh has been shifted to the new alternation l (voiceless):  s.[171] Does it follow that the voiceless l of language B has had the same history?  Not in the least.  Perhaps B has a strong tendency toward audible breath release at the end of a word, so that the final l, like a final vowel, was originally followed by a marked aspiration.  Individuals perhaps tended to anticipate a little the voiceless release and to “unvoice” the latter part of the final l-sound (very much as the l of English words like felt tends to be partly voiceless in anticipation of the voicelessness of the t).  Yet this final l with its latent tendency to unvoicing might never have actually developed into a fully voiceless l had not the presence of voiceless l-sounds in A acted as an unconscious stimulus or suggestive push toward a more radical change in the line of B’s own drift.  Once the final voiceless l emerged, its alternation in related words with medial voiced l is very likely to have led to its analogical spread.  The result would be that both A and B have an important phonetic trait in common.  Eventually their phonetic systems, judged as mere assemblages of sounds, might even become completely assimilated to each other, though this is an extreme case hardly ever realized in practice.  The highly significant thing about such phonetic interinfluencings is the strong tendency of each language to keep its phonetic pattern intact.  So long as the respective alignments of the similar sounds is different, so long as they have differing “values” and “weights” in the unrelated languages, these languages cannot be said to have diverged materially from the line of their inherent drift.  In phonetics, as in vocabulary, we must be careful not to exaggerate the importance of interlinguistic influences.

[Footnote 171:  This can actually be demonstrated for one of the Athabaskan dialects of the Yukon.]

I have already pointed out in passing that English has taken over a certain number of morphological elements from French.  English also uses a number of affixes that are derived from Latin and Greek.  Some of these foreign elements, like the _-ize_ of materialize or the _-able_ of breakable, are even productive to-day.  Such examples as these are hardly true evidences of a morphological influence exerted by one language on another.  Setting aside the fact that they belong to the sphere of derivational concepts and do not touch the central morphological problem