These cries disclose from the first a germ of articulate sound, _viz._, according to Preyer an approach to the vowel sounds _u_ (oo) and _ä_ (Engl. _a_ in ‘made’). This articulate element becomes better defined and more varied in the later cries, and serves in part to differentiate them one from the other. Thus a difference of shade in the _a_ (in ‘ah’), difficult to describe, has been observed to mark off the cry of pleasure and of pain. Along with this articulate sounds begin to appear in periods of happy contentment under the form of infantile babbling or ‘la-la-ing’. Thus the child will bring out a string of _a_ and other vowel sounds. In this baby-twittering the several vowel sounds of our tongue become better distinguishable, and are strung together in queer ways, as _ai-ā-au-â_. An attempt is made by Preyer and others to give the precise order of the appearance of the several vowel sounds. It is hardly to be expected that observers would agree upon a matter so difficult to seize and to describe; and this is what we find.[60] After allowing, however, for differences in the reading off, it seems probable that there is a considerable diversity in the order of development in the case of different children. This applies still more to the appearance of the consonantal sounds which long before the end of the sixth month become combined with the vowels into syllabic sounds, as _pa_, _ma_, _mam_, and so forth. Thus, though the labials _b_, _p_, _m_, seem to come first in most cases, they may be accompanied, if not preceded, by others, as the back open sound _ch_ (in Scotch ‘loch’), or (according to Preyer and others) by the corresponding voiced sound, the hard _g_. Similarly, sounds as _l_ and _r_, which commonly appear late, are said in some instances to occur quite early.[61] Attempts have been made to show that the order of sounds here corresponds with that of advancing physiological difficulty or amount of muscular effort involved. Yet apart from the fact just touched on, that the order is not uniform, it is very questionable whether the more common order obeys any such simple physiological law. ----- Footnote 60: See Preyer, _op. cit._, Cap. 20; _cf._ the account given by De la Calle, Perez, _First Three Years_, p. 248. Stanley Hall observes that the first vocalisation of the infant could hardly be classified even with the help of Bell’s phonic notation or with a phonograph (_Pedagogical Seminary_, i., p. 132). ----- Footnote 61: Preyer’s boy first used consonants in the combinations _tahu_, _gö_, (_rööö_ = the French _eu_), _op. cit._, p. 366; _cf._ Cap. 21. -----