THE NERVOUS SYSTEM. 



177 



Fig. 147.— Antennae of Various Insects. 



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 

 Quadrupeds, the lips and 

 tongue ; and in Monkeys 

 and Man, the lips and the 

 tips of the tongue and fin- 

 gers. In the most sensitive 

 parts of Birds and Mam- 

 mals, the true skin is raised 

 up into multitudes of mi- 

 nute elevations, called pa- 

 pillce, containing loops of 

 capillaries and nerve-filaments. There is a correspondence 

 between the delicacy of touch and the development of in- 

 telligence. 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 

 knowledge of properties which cannot be felt. It is al- 

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

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



No special organ of taste can be de- 

 tected in the Invertebrates, although 

 all seem to exercise a faculty in se- 

 lecting their food. Even in Fishes, 

 Amphibians, Reptiles, and Birds this 



Fig. 148.— Papillae of Human r 1 



Palm, x 35, the cuticle be- sense is very obtuse, for 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. e., certain substances 



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