Language, differentiation of, [17];
origin of written, [18];
origin of verbal, [149];
origin of emotional, [220].
La Place's theory of planetary evolution, [263]-[265].
Laughter, common explanations of, [194];
movements in, [200];
groups of muscles successively affected in, [201];
caused by incongruities, [203];
facilitates digestion, [207].
Likeness and unlikeness, recognition of, the basis of classification, [147];
the basis of language, [149];
of reasoning, [150];
of art, [151];
leads to science, [152].