Before dismissing the question of adequate stimuli one other set of phenomena ought to be mentioned. There are cases in which sapid substances dissolved in the blood produce taste sensations. In cases of diabetes, where sugar is present in the blood, a sweet taste is experienced in the absence of stimuli upon the tongue surface. Also, in cases of jaundice, where there is an excess of bile, a bitter sensation may be experienced. Here the stimuli affect either the taste nerves or the taste buds directly. There is no reason to think that the stimulation process differs in any other respect from the normal, except in the mode of access to the taste buds. _Inadequate Taste Stimuli_ Our second question concerns the possibility of other stimuli to taste, or of inadequate stimuli. Among these forms of stimulation three will be considered, namely, mechanical, thermal, and electrical. Are taste sensations produced by mechanical stimulation of the sense organ? Some of the older experimenters reported that tapping the tongue lightly or putting it under slight pressure aroused taste sensations of sour and bitter. But there does not seem to be good ground for such a conclusion. No doubt under poorly controlled conditions such mechanical stimuli might serve to force sapid substances already upon the tongue into the taste pores and thus stimulate the taste nerves. This, however, would be only an indirect effect of mechanical stimulation and not at all analogous to the visual sensations produced by mechanical stimulation of the eyeball. It is rather interesting to note in this connection that mechanical stimulation of the chorda tympani nerve, which carries the impulses from the anterior two-thirds of the tongue, is said to produce taste sensations. In cases in which the eardrum has been removed, stimulation of the nerve in the middle ear is said by some authorities to produce sweet and bitter sensations, and by others nothing but pricking sensations.