THE NERVOUS SYSTEM. 
177 
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 jpa- 
piUce^ 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. 
]STo 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 x , 
Palm, x 35 , the cuticle be- sense is very obtuse, for they bolt 
mg removed. 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 
12 
Fig. 147.—Antennae of Various Insects. 
