262 TASTE SENSATIONS. [BOOK in. 



alone and apart by itself. And not infrequently, as when sub- 

 stances at once sapid and pungent are placed in the mouth, the 

 general sensation of pungency overcomes and hides the specific 

 gustatory sensation. In the case of acids, it is often difficult to 

 distinguish between the acid taste and the more general effect of 

 the acid on the common sensibility of the buccal membrane of 

 which we spoke above 864. 



Though we possess a gustatory apparatus with separate nerves 

 on each side of the mouth all our sensations are single. Nor can 

 we distinguish a pure gustatory sensation developed on one side 

 only from one developed on both sides, if the two are equally 

 intense. 



As in the case of the senses previously dealt with, we may 

 experience subjective gustatory sensations, sensations of central 

 origin due to changes in the central sensory organs ( 676) ; and 

 these, though originated not by gustatory impulses but by other 

 events, may seem to us identical with those set up in an ordinary 

 way by gustatory impulses reaching the centre along the gustatory 

 fibres. 



867. Sensations of taste are not originated, either by sapid 

 substances or otherwise, equally in all parts of the lining mem- 

 brane of the mouth. The part in which they are best developed, 

 and always developed if developed at all, is the back of the tongue, 

 in the neighbourhood of the circumvallate papillae. They are 

 also developed at the tip and along the sides of the tongue, but to 

 a variable extent in different individuals ; some persons have very 

 acute and distinct taste sensations in these parts, others little or 

 none at all. On the dorsal surface of the middle of the tongue 

 very feeble taste sensations, if any at all, are developed ; they 

 are always wholly absent from the under-surface of the tongue. 

 Some taste sensations are also developed in the soft palate and 

 front surface of the palatine arches ; but these again vary much 

 in distinctness in different individuals. In the cases recorded in 

 which taste remained after the entire extirpation of the tongue 

 including the circumvallate papilla?, the sensations seem to have 

 been chiefly developed in the soft palate. There is also some 

 evidence that taste sensations may be developed on the hinder 

 surface of the epiglottis. 



In individuals who receive sensations from all or several of the 

 various parts above mentioned, it commonly happens that bitter 

 things are most readily appreciated at the back of the tongue and 

 sweet things at the tip ; and this distribution may perhaps be con- 

 sidered as the normal one ; but individual variations in this respect 

 are met with ; many persons taste both bitter and sweet things best 

 at the back of the tongue ; and some persons taste bitter things 

 quite distinctly at the tip. The salt taste is said to prevail at 

 the tip and the acid taste at the sides of the tongue ; but many 

 persons experience acid and salt tastes in those regions and 



