750 SPECIAL SOMATIC AND VISCERAL RECEPTORS 



investigators also claim to have produced sweet and bitter sensations. 1 

 Much diversity of opinion, however, prevails regarding the central 

 distribution of these fibers. Thus, Krause 2 states that the total 

 extirpation of the Gasserian ganglion is followed by a loss of taste in 

 the corresponding anterior region of the tongue. Gushing, 3 moreover, 

 has found that this operation never impairs the taste sensations from 

 the posterior part of the tongue. It may be concluded, therefore, 

 that the fibers from this region traverse the petrosal ganglion and enter 

 the sensory nucleus of the glossopharyngeus in the medulla. The 

 fibers from the taste buds of the larynx must necessarily follow the high- 

 way of the vagus, while those from the anterior two-thirds of the tongue 

 must for the present be assumed to enter by way of the trigeminus 

 and facial nuclei. 



The Activation of the Taste Buds. When food is taken into the 

 mouth, it is subjected to a mechanical as well as chemical reduction, 

 with the result that it is brought into intimate relation with the largest 

 possible number of taste buds. Substances to be tasted must, of course, 

 be in a fluid state. This end is generally attained with the aid of the 

 sali va which not only acts as a solvent, but also tends to carry the par- 

 ticles into the crevices between the base of the tongue and the fauces, 

 and facilitates their entrance into the furrows around the papillae 

 in which the taste buds are situated. Clearly, the movements of the 

 tongue are not essential to taste, but materially facilitate the reduction 

 and distribution of the food. It may be concluded, therefore, that 

 the sensation of taste arises in consequence of a reaction between the 

 sapid substance and the protoplasm of the gustatory cells, through the 

 intervention of their hair processes. 4 It must also be evident that 

 this reaction can only take place if the sapid agent possesses definite 

 chemical properties. It is true, however, that chemically allied bodies 

 need not exhibit identical characteristics in this regard. Thus, 

 sugar, saccharin and lead acetate all give rise to a sweet taste, while the 

 starches do not. In addition, it should also be remembered that sensa- 

 tions of taste may be evoked by substances contained in the blood. 

 Thus, the j aundiced person frequently experiences a bitter taste, while the 

 diabetic perceives sweet. It has also been claimed that sensations of taste 

 may be evoked by electrical means, but not by mechanical or thermal 

 stimuli. Thus, it is usually stated that the anode gives rise to a sour 

 and the cathode to a bitter sensation. This phenomenon has been 

 referred by some experimenters to a direct excitation of the taste buds, 5 

 while others contend that it arises only in consequence of electrolytic 

 dissociations at the seat of the electrodes. 6 At the present time no 



1 Blau, Berliner klin. Wochenschr., xlv, 1879. 



2 Miinchener med. Wochenschr., xlii, 1895. 



3 Bull, of the Johns Hopkins Hospital, Baltimore, xiv, 1903, 77. 



4 Zwaardemaker, Ergebn. der Physiol., Wiesbaden, 1903. 



B Ohrwall, Skand. Archiv fur Physiol., ii, 1891, and Zeynek, Zentralbl. fur 

 Physiol., xiii, 1898. 



8 Hermann, Grundrisse der Physiol., 1872, 337. 



