In line with the fact that taste and odor are easily confused, and contributing perhaps to this confusion, is the fact that tastes and odors are related to each other through their antagonism, almost if not quite as definitely as are the qualities within each of the separate modes. Thus, the sickening odor of many medicines is somewhat palliated if they are taken in fermented juices or with the sour acids of fresh fruits. “Quinine, which tastes bitter and has no smell, is corrected by essence of orange peel, which has an aromatic smell and no taste.” Titchener pertinently remarks that these results may in part arise from the simple process of distracting attention from an unpleasant item to a more agreeable part of the experience. On the other hand, the special effectiveness of the introduction of odors into the complex rather than pleasant sights and sounds suggests that the results in the case of taste and smell are not solely a matter of attention, but are in part, at least, dependent on the essential relationships between the qualities of these two modes of sensation. In the chapter on “The Evolution of Taste” certain light is thrown on the closeness of these relationships by our knowledge of the intimate biological connection between taste and smell. In certain lower forms of animal life it is indeed quite impossible to draw any clear line between these two features of “the chemical sense.” In general, then, although the facts of compensation, antagonism, and complementariness are to be observed within the field of the taste qualities, the relations disclosed are by no means as definite nor as systematic as they are in the case of vision. For a given primary color quality there exists only one other elementary quality which stands to it in the relation of antagonist. But we have seen that in the cases of both sour and bitter there is at least some degree of antagonism with all three of the other qualities, while both sweet and salt antagonize in some degree both sour and bitter. Moreover, at least the sour, the bitter, and the sweet appear to show antagonistic relations to certain qualities of smell.