Galton, in a note entitled “Arithmetic by Smell,” has described an arrangement by means of which he convinced himself that some arithmetical operations can be carried out by the help of olfactory images, as is done by means of visual and auditory representations. He trains himself to regard two whiffs of peppermint as equivalent to one of camphor, and three of peppermint with one of carbolic acid; he performs small additions, and, later on, operates with images only (visual and auditory representations being excluded). For details, see _Psychological Review_, January 1894. ----- As to the recollections of tastes, by themselves, the answers are very vague. One remembers “easily, and at will, the taste of salt, with a very clear visual impression,” but less easily the other three fundamental tastes. Another, who uses for his throat three different kinds of lozenges, “feels the taste of them beforehand, as soon as he needs them, on either seeing or touching them.” In general, the revivability of tastes appears to me especially connected with that of ordinary food, and with the state of the alimentary canal (hunger). 2. _Internal sensations._—My inquiry does not include the whole of these, but only the commonest and most easily observed.[100] ----- Footnote 100: The memory of internal sensations, though distinct from that of states of feeling properly so called, approximates so closely to it that the two subjects appear to me inseparable. ----- As regards hunger, I have received 51 definite answers, 24 persons saying they can distinctly recall it, 27 that they cannot. (The question has always been put at an hour when the real sensation did not exist, and some have told me that in their normal condition they never feel either hunger or thirst.) It is usually described as a tactile sensation in the œsophagus, or a twitching pain in the stomach, etc. One person only affirms that he can, “at will, feel hunger and thirst, even after having eaten and drunk.” Thirst is imagined much more frequently than hunger, and, as it seems, more clearly (36 affirmative to 15 negative answers). It is described as dryness in the throat, heat, etc.