Another early example of an emotional expression passing into a germinal sign is that called forth at the sight of moving creatures. This acts as a strong stimulus to the baby brain, and vigorous muscular reactions, vocal and other, are wont to appear. One little boy of twelve and three-quarter months usually expressed his excitement by the sound “Dō-boo-boo,” which was used regularly for about ten days on the appearance of a dog, a horse, a bird, and so forth. Here we have a protoplasmic condition of the lingual organism which we call a name, a condition destined never to pass into another and higher. Sometimes, however, these explosives at the sight of animal life grow into comparatively fixed signs of recognition. In this spontaneous invention of quasi-linguistic sounds imitation plays a considerable part. It is evident, indeed, that gestures are largely imitative. Thus the sniff and the mimic kiss referred to just now are plainly imitations of movements. The pointing gesture, too, may be said to be a kind of imitation of the reaching and appropriating movement of the arm. The sound ‘dō-boo-boo’ used on seeing an animal was probably imitative. According to Preyer the sounds called forth by the sight of moving objects, _e.g._, rolling balls and wheels, are imitative.[68] Whether the signs of hunger, ‘mum,’ ‘numby,’ are due to modifications of the movements carried out in sucking, seems to be more problematic.[69] ----- Footnote 68: _Op. cit._, p. 358. Footnote 69: A fact that appears to tell against imitation here is that one little boy of seventeen months used the sound ‘did’n’ for anything to eat. ----- In certain cases imitation is the one sufficient source of the sound. In what are called onomatopoetic sounds the child seeks to mimic some natural sound, and such imitation is capable of becoming a fruitful source of original linguistic invention. A boy between nine and ten months imitated the sound of young roosters by drawing in his breath, and this noise became for a time a kind of name for any feathered creature, including small birds. More commonly such onomatopoetic sounds come to be distinctive recognition-signs of particular classes of animals, such as ‘oua-oua’ or ‘bow-wow’ for the dog, ‘moo-moo’ for the cow, ‘ouack-ouack’ or ‘kuack’ for the duck, and so forth.