Other two no less celebrated names must also be mentioned here, on account of the strictly scientific character they have given to the study of the emotions. These are Herbert Spencer and Charles Darwin. Next to these stands Paolo Mantegazza, with his celebrated researches on pain and his book on physiognomy and mimicry, dedicated to 'Charles Darwin, who, by his immortal work on the expression of the emotions, opened up a limitless horizon to the science of the future.’ The homage of the illustrious Italian physiologist is worthy of the great English master and philosopher. Darwin was a man of genius and at the same time one of the greatest masters of the popular style of authorship. His force lies in the caution with which he made statements and drew conclusions, thus avoiding all absolute formulæ, and this will always make him an incomparable model. Dogmatism, that worm which gnaws and sterilises mediocre minds, which corrupts the rationality of the many--dogmatism, that plague of science, had no hold on him, Darwin knew it not. He candidly shows the public the gaps in science, criticises himself unmercifully, and does not hesitate to point out the defects in doctrines he himself propounded. In reading his books one is inclined to think that he was continually haunted by the fear of being misunderstood by readers insufficiently educated for the comprehension of deeper scientific questions. He was so careful, so temperate in his assertions, so cautious in his inductions, that in his book, 'The Expression of the Emotions,’ which, in my opinion, is one of the less excellent of his works, he leaves not one point on which one can conscientiously contradict him, by taxing him with an error. And if we are able now to add to his discoveries and to correct some of the judgments in his works, it is only thus because science marches onward with such giant strides that we, although we were his contemporaries, belong even now to a later age, as the context of this work will more clearly show. The theory of evolution will always remain the foundation-stone of modern science, but certain principles formulated by Spencer and Darwin will be modified as our knowledge of the adaptation of organs to their functions increases. IV Darwin attributed, I think, too much importance to the will considered as the cause of expression. We younger physiologists are more mechanical; we examine the organism more minutely, and it is in the structure of the organs that we seek the reasons of their functions. I shall here give an example of this different way in which I have explained a few phenomena.