TASTE 



29 



relation to swimming, but it sometimes happens that they have 

 been transformed into tactile organs, as in the deep-sea form 

 (Eretmophorus] represented in fig. 1034. Snakes employ their 

 tongues as tactile organs, as 

 also do Woodpeckers and Ant- 

 eaters. This, however, is pro- 

 bably only an extension of the 

 original duties, for the primary 

 use of the tongue seems to be 

 that of a tactile organ in re- 

 lation to the mouth-cavity. 



TASTE 



Sensations of Taste are pri- 

 marily important because they 

 assist in the selection of suit- 

 able food. The Stimulus is a Fig. io 3 5.-Taste-Organs of a Wasp. A, Under side of 

 , . . . r kft max il' a > enlarged, showing group of taste-cups (T.C.). 

 ChemiCal One, and COnSlStS OI B , A single taste-cup, greatly enlarged. 



substances in solution. We 



know but little about the gustatory organs of lower forms, but 

 as these show a preference for certain kinds of food it is pro- 

 bably correct to assume that such organs are present. In the 

 Earth -Worm, for example, groups of modified epidermal cells 

 in the neighbourhood of the mouth are very 

 likely related to taste. 



Certain regions of the mouth-parts of some 

 Insects are studded with minute pits, beneath 

 each of which is a sense-cell, drawn out ex- 

 ternally into a short bristle, and continuous with 

 a nerve-fibre internally. They are present, for 

 example, in Bees and Wasps, and are almost 

 certainly of a gustatory nature (fig. 1035). 



Cuttle- Fishes and many Snails possess a 

 sense-organ on the floor of the pharynx, below 

 the front end of the rasping-ribbon. It pro- 

 bably has to do with taste. 



In Lung-Fishes, Amphibians, Reptiles, Birds, and Mammals 

 the organs of taste consist of groups of sense-cells in the lining 

 of the mouth-cavity, and since this cavity is developed as an 



Fig. 1036. Taste- Bud from 

 the Tongue of a Rabbit, in 

 longitudinal section, greatly 

 enlarged. The bud contains 

 slender taste-cells, the exter- 

 nal ends of which project into 

 a little pit continuous with the 

 mouth-cavity. 



