826 PATHOLOGICAL COMPARATIVE HISTORICAL. 



persistent " aftertaste." 4. The delicacy of the sense of taste is partly congenital, 

 but it can be greatly improved by practice. If a person continues to taste the 

 same sapid substance, or a nearly related one, or even any very intensely sapid 

 substance, the gustatory sense is soon affected, and it becomes impossible to give a 

 correct judgment as to the taste of the sapid body. 5. Taste is greatly aided by the 

 Bense of smell, and in fact we often confound taste with smell ; thus, ether, chloro- 

 form, musk, and assafoetida only affect the organ of smell. [The combined action 

 of taste and smell in some cases gives rise to flavour (p. 823)7] The eye even may 

 aid the determination, as in the experiment where in rapidly tasting red and white 

 wine one after the other, when the eyes are covered, we soon become unable to 

 distinguish between the one and the other. 6. The most advantageous temperature 

 for taste is between 10 to 35 C. ; hot and cold water temporarily paralyse taste. 



Ice placed on the tongue suppresses, sometimes entirely, the whole gustatory apparatus ; 

 cocain alone, bitter tastes, and water containing 2 per cent, of H 2 S0 4 , excite afterwards a 

 sweet taste (Aducco a>id Mosso). 



Electrical Current. The constant current, when applied to the tongue, excites, both 

 during its passage and when it is opened or closed, a sensation of acidity at the + pole, and at 

 the - pole an alkaline taste, or, more correctly, a harsh burning sensation (Sulzer, 1752). This 

 is not due to the action of the electrolytes of the fluid in the mouth, for even when the tongue 

 is moistened with an acid fluid the alkaline sensation is experienced at the - pole ( Volta). We 

 cannot, however, set aside the supposition that perhaps electrolytes, or decomposition -products, 

 may be formed in the deeper parts and excite the gustatory fibres. Rapidly interrupted 

 currents do not excite taste (Griinhagcn). V. Vintschgau, who has only incomplete taste on 

 the tip of the tongue, finds that when the tip of the tongue is traversed by an electrical current, 

 there is never a gustatory sensation, but always a distinct tactile one. In experiments on 

 Hbnigschmied, who is possessed of normal taste in the tip of the tongue, there was often 

 a metallic or acid taste at the + pole on the tip of the tongue, while at the - pole taste was often 

 absent, and when it was present it was almost always alkaline, and acid only exceptionally. After 

 interrupting the current there was a metallic after-taste with both directions of the current. 



[Testing Taste. Direct the person to put out his tongue and close his eyes, and 

 after drying the tongue apply the sapid substance by means of a glass rod or a 

 small brush. Try to confine the stimulus as much as possible to one place, and 

 after each experiment rinse the mouth with water. A wine-taster chews an olive 

 to "clean the palate," as he says. For testing bitter taste use a solution of quinine 

 or quassia ; for siveet, sugar, [or the intensely sweet substance "saccharine " obtained 

 from coal tar] ; saline, common salt ; and acid, dilute citric or acetic acid. The 

 galvanic current may also be used.] 



Pathological. Diseases of the tongue, as well as dryness of the mouth caused by interference 

 with the salivary secretion, interfere with the sense of taste. Subjective gustatory impressions 

 are common amongst the insane, and are due to some central cause, perhaps to irritation of the 

 centre for taste ( 378, IV., 3). After poisoning with santonin, a bitter taste is experienced, 

 while after the subcutaneous injection of morphia, there is a bitter and acid taste. The terms 

 hypergeusia, hypogeusia, and ageusia are applied to the increase, diminution, and abolition 

 of the sense of taste. Many tactile impressions on the tongue are frequently confounded with 

 gustatory sensations, e.g., the so-called biting, cooling, prickling, sandy, mealy, astringent, 

 and harsh tastes. 



Comparative. About 1760 taste-bulbs occur on the circumvallate papillte of the ox. The 

 term papilla foliata is applied to a large folded gustatory organ placed laterally on the side of the 

 J^f^li!!?' 607 ^especially of the rabbit (Rapp, 1832), which in man is represented by analo- 



ra each side of the 



reptiles and birds. 



*..o tongue of the frog 



covered with epithelium resembling gustatory cells (Billroth, Axel Key). The goblet-shaped 

 organs in the skin of fishes and tadpoles have a structure similar to the taste-bulbs, and may 

 perhaps have the same function. There are taste-bulbs in the mouth of the carp and ray. 



historical Bellini regarded the papillae as the organs of taste (1711). Richerand, Mavo, 

 ana r-oaera thought that the lingual was the only nerve of taste, but Majendie proved that, 

 atter it was- divided, the posterior part of the tongue was still endowed with taste. Panizza 



i Zu i C , i g lo8so i )har yngeai as the nerve of taste, the gustatory as the nerve of touch, 

 and the hypoglossal as the motor nerve of the tongue. 



IS 



