Two of the most characteristic features of modern psychology are (1) the special attention given to the facts of emotional consciousness, and (2) the persistent endeavour to obtain a quantitative statement of results. In the former respect advance has been due mainly to the adoption of the biological method. By taking the biological problem of instinct and the psychological problem of emotion in conjunction a provisional solution has been obtained of both, much as two nuts may be more easily cracked together than when taken separately. In the latter respect mental measurement has been mainly indirect in character, although the possibility of direct mental measurement is not entirely ruled out. What is measured is some physiological concomitant or other of the mental process, not the mental process itself. Nevertheless, since the mental character of the process prompts the measurement and furnishes its relevance, such measurement rightly belongs to psychology, although of course, it also belongs to physiology. The present work by Mr Whately Smith well illustrates these two features. In it the biological significance of emotion and of affective tone is emphasised, and by means of special methods of experimentation quantitative results are obtained which illuminate the subject in a remarkable way. This edition first published in 1999. Routledge is an imprint of Taylor & Francis, an informa company.