All sorts of taste abnormalities are found in hysteria, but little is known of their underlying causes in the taste mechanism. There may be either hyper- or hypo-sensitivity, although the latter is more common; and both sides of the tongue or only one side may be affected, or even only a small portion of the tongue may be involved. Here, too, the taste abnormalities are accompanied by disturbances of the other senses. Criminals, especially those recognized as degenerate, show taste abnormalities, usually extreme dullness of taste, along with the same sort of defect in the other senses. Attempts have been made to find a positive correlation between keenness of taste and number of stigmata of degeneration, but with no success. Any condition affecting the mucous lining of the mouth cavity may be expected to modify taste sensitivity. For instance, burning the tongue with a hot drink will destroy taste for a time. Tumors and abnormal thickening of the epithelium of the tongue will likewise disturb the taste function. These effects are clearly due to a direct action upon the taste buds or the gustatory pores, and may be local or general in character. Under this head might be mentioned the effects of drugs applied to the tongue surface, but they have been discussed elsewhere. Hallucinations of taste likewise, of which there are a great variety, have been described in another connection. _Racial Differences in the Structure and Function of the Taste Organs_ A number of races, e.g., Negroes, Japanese, Europeans, etc., have been studied to determine differences in the taste mechanism, but little of significance has been found. The number of papillæ upon the tongue is just about the same in every case. The slight differences of size and arrangement of the papillæ, especially the circumvallate type, are not such as to be of much importance from the functional point of view. The variation in these respects is so large within any one racial group that there is little likelihood of finding significant racial differences. ------------------------------------------------------------------------ CHAPTER X EVOLUTION OF TASTE _Sensitivity of the Unicellular Organisms_ THE study of the sense organ of taste in adult human beings consists of an examination of the taste sensations resulting from controlled stimulation of limited parts, supported by the microscopical examination of the structures found in the regions in which these taste sensations can be aroused. The relation of cause and effect is then assumed. Neither method taken alone will suffice, as there always remains the possibility of function in the absence of definitely recognized taste structures and also the possibility of the presence of functionless structures. The difficulties and uncertainties arising in this combined study of structure and function have been discussed in earlier chapters.