THE NERVOUS SYSTEM. 



177 



FIG. 147. Autennae of Various Insects. 



the " feelers" (tentacles, horns, and antennge) ; 89 in the Oys- 

 ter, the edge of the mantle is most sensitive ; in Fishes, the 

 lips; in Snakes, the tongue; 

 in Birds, the beak and under 

 side of the toes ; in Quadru- 

 peds, the lips and tongue ; 

 and in Monkeys and Man, 

 the lips and the tips of the 

 tongue and fingers. In the 

 most sensitive parts of Birds 

 and Mammals, the true skin 

 is raised up into multitudes 

 of minute elevations, called 

 papillae, containing loops of capillaries and nerve-filaments. 

 At the ends of the latter are the essential organs of touch, 

 the tactile corpuscles and the touch-cells. There is a corre- 

 spondence between the delicacy of touch and the develop- 

 ment of intelligence. The Cat and Dog are more sagacious 

 than hoofed animals. The Elephant and Parrot are remark- 

 ably intelligent, and are as celebrated for their tactual power. 

 Taste is more refined than touch, since it gives a knowl- 

 edge of properties which cannot be felt. It is always 

 placed at the entrance to the digestive canal, as its chief 

 purpose is to guide animals in their choice of food. Special 

 organs of taste have been detected in 

 only afew of the In vertebrates, though 

 all seem to exercise a faculty in se- 

 lecting their food. Even in Fishes, 

 Amphibians, Reptiles, and Birds this 



FIG. 148. Papillae of Human . ., , 



Palm, x 35, the cuticle be- sense is very obtuse, tor they bolt 

 their food. But the higher Verte- 

 brates have it well developed. It is confined to the tongue, 

 and is most delicate at the root. 90 A state of solution and 

 an actual contact of the fluid are necessary conditions. 

 Smell is the perception of odors, i. <?., certain substances 



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