The taste sense differs from most of the other special senses in a number of respects, some of which have been mentioned in the preceding chapter. Still another striking difference is to be found in the nerve supply for taste as compared with that of the senses of sight, hearing, and smell. In the latter group there is one nerve which carries the impulses from the sense organ to the brain. Thus, we have the optic nerve for vision, the auditory nerve for hearing, and the olfactory nerve for smell. In taste, however, no single cranial nerve can be called the nerve of taste or the gustatory nerve. There has always been a great deal of difference of opinion as to how the taste fibers are carried to the brain, no small part of which has been due to the seeming necessity for finding “a taste nerve.” As early as 1823 evidence began to accumulate to show that more than one nerve must be involved. Other contributing factors to this confusion are, first, the use of experimentation upon animals—the conclusions from which have been considered valid for man as well as animals, an assumption which is not necessarily correct; and, second, the fact that there seem to be rather pronounced individual differences in the course taken by the fibers from taste bud to brain center. Three of the cranial nerves are now generally conceded to carry taste fibers: the lingual, which is a branch of the trigeminus, or fifth, nerve; the glossopharyngeal, or the ninth, nerve, and the vagus, or the tenth, nerve. The first two of these are more important for taste than the third. The lingual carries the fibers from the anterior two-thirds of the tongue, the upper surface, and the sides of that portion of the tongue and the tip; the glossopharyngeal carries the fibers from the posterior third of the tongue, including the base of the tongue, the soft palate, and the papillæ foliatæ; the vagus carries fibers from the epiglottis and the larynx.