1032 TASTE SENSATIONS. [Book hi. 



may learn that by concomitant general sensations arising in the 

 buccal mucous membrane. And it must be remembered that 

 all our gustatory sensations are always accompanied by tactile 

 or other sensations ; we do not, as in the case of smell, experi- 

 ence the specific sensation alone and apart by itself. And not 

 infrequently, as when substances at once sapid and pungent are 

 placed in the mouth, the general sensation of pungency over- 

 comes 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 

 § 639. 



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 (§ 502) : 

 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. 



§ 642. Sensations of taste are not originated, either by 

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

 membrane 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 papillae, 

 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 considered as the normal one ; but individual varia- 



