days again and again in a vacant way, with and without the
tone of interrogation (which he did not understand). From this we see
again plainly that the imitation of sounds is independent of the
understanding of them, but is dependent on the functions of
articulation.

These functions are discussed by themselves in the work of Prof. Fritz
Schultze, of Dresden, "Die Sprache des Kindes" ("The Language of the
Child," Leipsic, 1880, 44 pp.). The author defends in this the
"principle of the least effort." He thinks the child begins with the
sounds that are made with the least physiological effort, and proceeds
gradually to the more difficult sounds, i. e., those which require more
"labor of nerve and muscle." This "law" is nothing else than the "loi du
moindre effort" which is to be traced back to Maupertuis, and which was
long ago applied to the beginnings of articulation in children: e. g.,
by Buffon in 1749 ("Oeuvres completes," Paris, 1844, iv, pp. 68, 69),
and, in spite of Littre, again quite recently by B. Perez[F] ("Les trois
premieres Annees de l'Enfant," Paris, 1878, pp. 228-230, _seq._) But
this supposed "law" is opposed by many facts which have been presented
in this chapter and the preceding one. The impossibility of determining
the degree of "physiological effort" required for each separate sound in
the child, moreover, is well known. Besides, every sound may be produced
with very unequal expenditure of force; but the facts referred to are
enough for refutation of the theory. According to Schultze, e. g., the
vowels ought, in the process of development of the child's speech, to
appear in the following order, separated in time by long intervals: 1.
Ae; 2. A; 3. U; 4. O; 5. E; 6. I; 7. Oe; 8. Ue. It is correct that _ae_ is
one of the vowels that may be first plainly distinguished; but neither
is it the first vowel audible--on the contrary, the first audible vowel
is indistinct, and imperfectly articulated vowels are the first--nor can
we admit that _ae_ is produced with less of effort than is _a_. The
reverse is the case. Further, _oe_ is said to present "enormous
difficulties," and hence has the place next to the last; but I have
often heard the _oe_, short and long, perfectly pure in the second month,
long before the _i_, and that not in my child alone. From the
observations upon the latter, the order of succession appears to be the
following: Indeterminate vowels, _u_, _ae_, _a_, _oe_, _o_, _ai_, _ao_,
_i_, _e_,