. 



THE SENSE OF TASTE 151 



precise localisation in the peripheral taste organs. Such a case 

 would be of the highest interest. 



Partial congenital defects, on the other hand, have been 

 frequently reported, particularly the total or partial absence of 

 taste at the tip of the tongue. Still more common are individual 

 variations in the localisation of sensibility to the four primitive 

 tastes, already discussed (p. 134). Not infrequently the distinc- 

 tion between salt and sour is little marked, but this may possibly 

 depend on the different use of the two terms in the language of 

 different individuals, rather than on their dissimilar capacity of 

 discriminating between the two tastes. 



Loss of the sense of taste under morbid conditions (ageusia) 

 is not uncommon owing either to peripheral lesions or to central 

 lesions on one or both sides of part or of the whole of the gustatory 

 area. Such paralysis may affect the power of perceiving different 

 tastes in different degrees. 



Alteration of the specific qualities of taste (parageusia) is 

 fairly frequent in central diseases as the precursor of a more or 

 less complete paralysis of taste. In a clinical case observed by 

 Nagel unilateral paralysis of taste was preceded by a state in 

 which the patient perceived all tastes on the affected side as salt. 



In hysterical persons partial or total suspension of gustatory 

 sensations is frequent. Kiesow has recently demonstrated that 

 true hallucinations of taste may be present even in persons who 

 are comparatively normal. Eeal gustatory or hallucinatory 

 dreams have also been noted (De-Sanctis, Kiesow, and others). 



The temporary, partial paralysis of taste which can be pro- 

 duced experimentally by the direct application of certain poisons 

 to the gustatory organs is also of great interest. Von Anrep 

 (1880), Knapp (1885), observed that cocaine kept for a certain 

 time in contact with the lingual mucosa abolishes all power of 

 taste. Aducco and U. Mosso (1866), on the contrary, found that 

 solutions of cocaine hydrochlorate, if not too concentrated, inhibit 

 sensibility only to bitter tastes, while for other tastes it is altered 

 little, if at all. Oehrwall, Shore, Kiesow (1894) on repeating 

 the experiment showed -that the action of cocaine affects all 

 qualities of taste. Oehrwall, however, recognised individual 

 differences, and Kiesow discovered by accurate determination of 

 liminal excitation that cocaine acts more strongly on bitter, less 

 on sweet, still less on salt and sour taste. Shore arrived at 

 approximately the same conclusion. 



Von Anrep further showed that puncture by a needle at the 

 edge of the tongue pencilled with cocaine caused no pain. On 

 the other hand, Kiesow brought out the interesting fact that 

 even strong applications of cocaine do not cause the tip of the 

 tongue to lose its sensibility to pain and thermal stimuli. And 

 as cocaine affects gustatory sensibility soon after its application, 



