[…] the distinction of verb and noun in these languages [Scythian] is much less original, fundamental, and sharply drawn than with us. The verbally used forms are, rather, but one step removed from nouns used predicatively, with subjective or possessive pronominal elements appended […] To say this is not to say that these languages have no real verb; since to make a verb it needs only that certain forms be set apart and strictly devoted by usage to the expression of the predicative relation, but it does imply a decided inferiority in the grade of clearness of this most fruitful of formal distinctions, and made shade off into a total absence of it.
- Whitney (1875), a pag.233

[…] the inflectional system of the noun, and less distinctly that of the verb, reached a fullness which has since undergone a gradual reduction. No that there has been generally a diminution of ability to express distinctions, but means of another kind have been more and more resorted to: auxiliaries, form-words, instead of suffixes, formative elements in words […].
- Whitney (1875), a pag.211

[…] we have almost reduced to a nullity […] the concord of the verb and its subject […] the endings were the actual subject-pronouns themselves; and the distinction of person and number in the verb was the necessary concomitant and result of that in the pronouns and nouns.
- Whitney (1875), a pag.218

An early (perhaps the first) and most important act in the history of linguistic development out of […] scanty beginnings was that whereby a separation was made between noun (substantive and adjective) and verb. The essence of a verb is that it predicates or asserts; and the establishment of a distinct form by which predication shall be signified has by no means been reached in all languages.
- Whitney (1875), a pag.202

The making of a verb is nothing more than the establishment of certain combinations of elements in an exclusively predicative use, the supplying of a copula in connection with them and not with others. This was accomplished by adding certain pronominal elements to the verbal element […].
- Whitney (1875), a pag.202