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In the notes added to the second edition he remarks on Max Muller's denial of thought without words, "what a strange definition must here be given to the word thought!" (Op. cit. page 135, footnote 63.) He naturally finds the origin of language in "the imitation and modification of various natural sounds, the voices of other animals, and man's own instinctive cries aided by signs and gestures (op. cit. page 132.)...As the voice was used more and more, the vocal organs would have been strengthened and perfected through the principle of the inherited effects of use; and this would have reacted on the power of speech." (Op. cit. page 133.) On man's own instinctive cries, he has more to say in "The Expression of the Emotions". (Page 93 (Popular Edition, 1904) and elsewhere.) These remarks have been utilised by Prof. Jespersen of Copenhagen in propounding an ingenious theory of his own to the effect that speech develops out of singing. ("Progress in Language", page 361, London, 1894.)For many years and in many books Max Muller argued against Darwin's views on evolution on the one ground that thought is impossible without speech;consequently as speech is confined to the human race, there is a gulf which cannot be bridged between man and all other creatures. (Some interesting comments on the theory will be found in a lecture on "Thought and Language"in Samuel Butler's "Essays on Life, Art and Science", London, 1908.) On the title-page of his "Science of Thought" he put the two sentences "No Reason without Language: No Language without Reason." It may be readily admitted that the second dictum is true, that no language properly so-called can exist without reason. Various birds can learn to repeat words or sentences used by their masters or mistresses. In most cases probably the birds do not attach their proper meaning to the words they have learnt;they repeat them in season and out of season, sometimes apparently for their own amusement, generally in the expectation, raised by past experience, of being rewarded for their proficiency. But even here it is difficult to prove a universal negative, and most possessors of such pets would repudiate indignantly the statement that the bird did not understand what was said to it, and would also contend that in many cases the words which it used were employed in their ordinary meaning. The first dictum seems to be inconsistent with fact. The case of deaf mutes, such as Laura Bridgeman, who became well educated, or the still more extraordinary case of Helen Keller, deaf, dumb, and blind, who in spite of these disadvantages has learnt not only to reason but to reason better than the average of persons possessed of all their senses, goes to show that language and reason are not necessarily always in combination. Reason is but the conscious adaptation of means to ends, and so defined is a faculty which cannot be denied to many of the lower animals. In these days when so many books on Animal Intelligence are issued from the press, it seems unnecessary to labour the point. Yet none of these animals, except by parrot-imitation, makes use of speech, because man alone possesses in a sufficient degree of development the centres of nervous energy which are required for the working of articulation in speech. On this subject much investigation was carried on during the last years of Darwin's life and much more in the period since his death. As early as 1861 Broca, following up observations made by earlier French writers, located the centre of articulate speech in the third left frontal convolution of the brain. In 1876 he more definitely fixed the organ of speech in "the posterior two-fifths of the third frontal convolution" (Macnamara, "Human Speech", page 197, London, 1908.), both sides and not merely the left being concerned in speech production. Owing however to the greater use by most human beings of the right side of the body, the left side of the brain, which is the motor centre for the right side of the body, is more highly developed than its right side, which moves the left side of the body. The investigations of Professors Ferrier, Sherrington and Grunbaum have still more precisely defined the relations between brain areas and certain groups of muscles.