It is partly a desire of keeping up to date which is responsible for the copious extracts or abstracts from treatises on the anatomy and functions of the nerve-system, which, accompanied perhaps by a diagram of the brain, often form the opening chapter of a work on psychology. Even if these researches had achieved a larger number of authenticated results than they as yet have, they would only form an appendix and an illustration to the proper subject(42). As they stand, and so long as they remain largely hypothetical, the use of them in psychology only fosters the common delusion that, when we can picture out in material outlines a theory otherwise unsupported, it has gained some further witness in its favour. It is quite arguable indeed that it may be useful to cut out a section from general human biology which should include the parts of it that were specially interesting in connexion with the expression or generation of thought, emotion, and desire. But in that case, there is a blunder in singling out the brain alone, and especially the organs of sense and voluntary motion,—except for the reason that this province of psycho-physics alone has been fairly mapped out. The preponderant half of the soul’s life is linked to other parts of the physical system. Emotion and volition, and the general tone of the train of ideas, if they are to be connected with their expression and physical accompaniment (or aspect), would require a sketch of the heart and lungs, as well as the digestive system in general. Nor these alone. Nerve analysis (especially confined to the larger system), though most modern, is not alone important, as Plato and Aristotle well saw. So that if biology is to be adapted for psychological use (and if psychology deals with more than cognitive processes), a liberal amount of physiological information seems required.