380 SPECIAL PHYSIOLOGY. 



The Organs and Sense of Taste in Animals. 



Amongst the Vertebrata, the sense of taste is probably well developed in all 

 Mammalia, most of which masticate their food, and so retain it long enough 

 in the mouth to enable it to act as a sapid body. The chief organ of taste is 

 the tongue, but the soft palate, as in Man, may be supposed to be likewise 

 concerned in this sense. The dorsum of the tongue is generally very rough, 

 and frequently presents horny papillae, or, as in the Carnivora, horny recurved 

 spines, which aid in grasping the food in mastication, or even in rasping flesh 

 from bones, and in cleaning the coat of the animal itself; but the surface at 

 the root and edges is softer and is probably more actively gustatory. The 

 shape of this organ presents many and striking varieties. In some of the suc- 

 torial bats it is singularly modified, presenting a circular series of elevations, 

 provided with proper muscles and forming a sucking organ. In the ant-eater 

 it is long, slender, and worm-like, and can be protruded with great swiftness 

 for a distance of sixteen or eighteen inches. The tongue of the Cetacea gener- 

 ally, is broad, and only slightly movable ; in the herbivorous species, Sirenia, 

 it has a complicated papillary surface ; but in the zoophagous kinds, or true 

 Cetacea, it has neither circumvallate nor conical papillae, but merely minute 

 tactile papillae ; it has been doubted whether these animals possess the sense of 

 taste. Some Mammalia have a second, or even a third accessory tongue, as, 

 for example, the bears. 



The organ and sense of taste appear to be incompletely developed in Birds, 

 which, for the most part, swallow their food quickly, and indeed, seem to be 

 rather guided in their choice of it by the sense of sight. The tongue usually 

 has a horny covering at its tip, and is destitute of papillae, except near its base. 

 In the parrots, however, the tongue is roundish, large, and fleshy, and is cov- 

 ered with papillae ; in the flamingo it is also large, soft, and papillated. In a 

 few species it is cleft at the point, as in the ravens. This organ often presents 

 peculiarities connected with its use in the taking of food ; thus, in the humming- 

 bird it is rolled into a sucking tube, and terminates in hair-like filaments for 

 retaining the nectar of flowers ; in the toucan it is fringed with bristly processes 

 for trying the ripeness of fruit ; and, in the woodpeckers it is barbed with in- 

 verted processes for seizing insects. 



In Reptiles the tongue also appears to be rather a tactile than a gustatory 

 organ, for they almost all swallow their food immediately it has been seized ; 

 so that the sense of taste is probably quite subordinate. The chameleon has a 

 very large tongue, which, when protruded, is worm-like in shape ; it possesses 

 a central canal, and terminates anteriorly in a club-shaped extremity, smeared 

 over with a viscid secretion ; when darted out after prey, it appears longer than 

 the whole body of the animal. In the crocodiles the tongue is closely attached 

 to the floor of the mouth ; but in the chelonian reptiles it is free. The turtles 

 have a small and hard tongue ; in the land tortoises it is soft and papillated, 

 and is undoubtedly endowed with gustatory sensibility. In the Ophidia, and 

 in the small lizards, the tongue is bifid, and is lodged in a sheath, from which 

 it can be protruded with a darting quivering motion. 



Amongst the Amphibia the tongue is soft ; it lies inverted in the mouth, 

 both in the frog and toad, and is used as a prehensile organ. The structure 

 of the lingual papillae, and especially the mode of termination of their nerves, 

 have been closely studied in the frog. By some it is held that, in the large 

 fungiform papillae, the nerves end in fine fibres, which are attached to the bases 

 of the large terminal nonciliated epithelial cells, whilst the ramified muscular 

 fibres join the ciliated epithelium at the base of the papillae. (Stilling, Waller.) 

 It has also been stated that the nerves end in narrow cells, or rods, which pass 

 up to the surface between the true epithelial cells. (Axel Key.) We shall find 

 a similar structure, and this is an interesting fact, in the olfactory mucous 

 membrane of the nose. The less perfect Amphibia, such as the proteus and 

 siren, appear to be destitute of a tongue. 



In Fishes generally, the sense of taste is probably but imperfectly developed, 

 even if it exist. Some, indeed, have no tongue at all ; for they bolt their food 

 instantaneously, as it is taken, so that the gustatory sensibility, if present, 



