Further, many substances, in addition to these locally aroused experiences of touch, temperature, pain, and movement, set up strong organic reactions in more or less remote regions as well as strong affective reactions: such as choking, nausea, and vomiting, on the one hand, and extreme unpleasantness, disgust, distress, strain, and shock, on the other. In many cases these immediate reactions seem to be reflex or instinctive in their origin, and in other cases they seem to be conditioned reactions, based on past experiences and associations. Thus in one case the “taste” of ice cream, which was once agreeable enough, has come to be immediately nauseating in character. In spite of all these facts many of the classifications of taste qualities have included the “oily,” the “nauseous,” the “astringent,” etc., as primary taste experiences. Even if the complications we have thus far alluded to were the only ones concerned, it would be clear enough that the “tastes” and “flavors” of everyday conversation represent very complex fusions and compounds, and that an analysis of the true taste qualities, if such there be, must take these factors into account in some very careful experimental way. But we have left until this point a single complicating factor which in itself is sufficiently serious to call for very careful technical procedure in the examination of the sense of taste. This is the fact that a very great number of our so-called tastes are not tastes at all, but really odors. The sense organ of smell is so situated that it may be stimulated not only in the ordinary way, through particles borne into the nostrils by currents of air from the outside, but also by particles and vapors which pass up, from the mouth cavity, behind the soft palate, by way of passages called the “posterior nares.” In this way it happens that tasteless substances, with definite odor, are mistakenly supposed to have taste. In 1824 Chevreul reported a very simple experiment with which his name has since been universally associated. He pointed out that it is impossible to separate the action of a substance on the touch corpuscles of the tongue from its action on the taste buds themselves. He observed, however, that by a very simple expedient it is possible to eliminate to some degree the factor of odor. His classical experiment consisted in excluding the sense of smell in large part by pressing the nostrils with the fingers while the substance to be examined was presented to the tongue. In this manner he observed that a piece of camphor gum which had seemed to have a very distinctive taste had in reality no taste at all. When the nostrils were closed all that could be observed as the result of placing camphor on the tongue was a peculiar pricking sensation of touch, similar to that produced by various other substances. The sensation produced by the camphor was thus not a taste at all, but a fusion of odor and touch.