Taste sensations aroused by passing an electric current through the tongue were reported as early as the middle of the eighteenth century by Sulzer. Since that time a great number of experimental researches have accumulated in the attempt to answer the question whether an electric stimulus can directly arouse taste sensations, as it will produce sensations of light when it stimulates the eye. In all of this work there has been rather general agreement as to the character of the taste sensations present during electrical stimulation. Thus, when the anode (positive pole) comes into contact with the tongue the taste is said to be sour, while at the point where the cathode (negative pole) touches the tongue a bitter taste is reported. There is less general agreement upon the character of this cathode taste, however, than upon that of the anode taste, some describing it as burning, some as bitter, sweet, or alkaline. The great differences of opinion do not concern the character of the taste aroused by the electric current so much as the real source of the stimulation of the taste buds. It was suggested by Humboldt about 1800 that the taste sensations were not caused directly by the electrical stimulation of the taste buds, but rather by certain sapid substances which were set free within the mouth by the action of the current on the saliva. It is known that fluid salts can be broken down by electrolysis in such a way that at the anode an acid reaction, and at the cathode an alkaline reaction, can be detected. These facts have lent support to the assumption that the saliva thus acted upon by the electric current produces tastable substances. An interesting experiment attributed to Volta about 1800 seemed for a time to refute the whole electrolysis theory. He used an alkaline fluid for the anode, into which the tip of the tongue was dipped. Even in this case the characteristic sour taste was still experienced. But this experiment, like all of the others which seem to refute the electrolysis theory of electric stimulation, neglects the fact that the electrolysis may occur within the taste bud itself, and hence could not be detected by any test of the tongue surface, nor could the taste sensations thus produced be prevented by immersing the tongue in any kind of a solution, since this need not displace the fluids within the taste bud. The experience of both bitter and sweet tastes at the cathode, if these experiences are genuine, offers some difficulty for the electrolysis theory. The most that can be said is that it is quite likely that electrolysis takes place within the taste bud, but that, in addition to this, there may possibly be a certain direct action of the electrical stimulus upon the taste buds or their nerve endings.