In primitive systems, such as the Egyptian, Sumerian, Chinese, Maya-Quiche and Mexican, one or more of the various transitional steps may be developed and used simultaneously, with a constant tendency to advance on the lines above indicated, by gradual substitution of the later for the earlier stages. A comparison of the Sumerian cuneiform and Egyptian hieroglyphic systems brings out some curious results. Thus at an extremely remote epoch, some millenniums ago, the Sumerians had already got rid of the pictorial, and to a great extent of the ideographic, but had barely reached the alphabetic phase. Consequently their cuneiform groups, although possessing phonetic value, mainly express full syllables, scarcely ever letters, and rarely complete words. Ideographs had given place first to phonograms and then to mere syllables, "complex syllables in which several consonants may be distinguished, or simple syllables composed of only one consonant and one vowel or _vice versa_[113]." The Egyptians, on the other hand, carried the system right through the whole gamut from pictures to letters, but retained all the intermediate phases, the initial tending to fall away, the final to expand, while the bulk of the hieroglyphs represented in various degrees the several transitional states. In many cases they "had kept only one part of the syllable, namely a mute consonant; they detached, for instance, the final _u_ from _bu_ and _pu_, and gave only the values _b_ and _p_ to the human leg [Hieroglyph Symbol] and to the mat [Hieroglyph Symbol]. The peoples of the Euphrates stopped half way, and admitted actual letters for the vowel sounds _a_, _i_ and _u_ only[114]." In the process of evolution, metaphor and analogy of course played a large part, as in the evolution of language itself. Thus a lion might stand both for the animal and for courage, and so on. The first essays in phonetics took somewhat the form of a modern rebus, thus: [Hieroglyph Symbol] = _khau_ = sieve, [Hieroglyph Symbol] = _pu_ = mat; [Hieroglyph Symbol] = _ru_ = mouth, whence [Hieroglyph Symbol] = _kho-pi-ru_ = to be, where the sounds and not the meaning of the several components are alone attended to[115].