THE NERVES OF SENSATION. 
187 
a certain extent in every quadruped. In the quadrumana the sense 
of touch is chiefly resident there ; but it is much impaired by 
the inability to use the fingers to any considerable extent sepa- 
rately, or readily to bring the thumb in opposition to the fingers, 
and the consequent difficulty or impossibility of becoming so 
readily acquainted with the properties of bodies. This alone would 
form an insuperable barrier between the bimana and the quadru- 
mana, so far as intellect is concerned. The sense of smell is often 
summoned by the latter to the aid of the defective sense of touch. 
Digitigrades. — The tribe of the Digitigrades obtain some import- 
ant information from the expansion of nervous fibrils on the foot, 
and particularly from the flexibility of the toes and the insertion 
of the nails. Although the nails are hard and insensible bodies, 
they are useful auxiliaries. The part of the true skin on which 
they are placed, or into which they are inserted, is highly 
vascular; and the nervous papillae are numerous and prominent, 
and the least pressure on the nail is immediately and fully recog- 
nized. You may often see with what pleasure the young dog, 
or the carnivorous animal of any kind, is employed in thrusting 
about, and playing with every little moveable object within his 
reach. In addition to this, the deficiency of sensibility in the 
foot is, for the wants and the usefulness of these animals, abun- 
dantly supplied by the sense of smell. 
The Solipede and the Ruminant . — The hoofs of these animals 
are attached to the feet by means of duplicatures of membrane 
covered, or in a manner composed, of bloodvessels and nervous 
papillae, and by means of these a sufficient degree of feeling is 
conveyed for the purposes of progression, and too often a great 
degree of torture when the foot is diseased. For other purposes 
the lips are employed or the faculty of smelling, and that quite 
as far as the well-being of the animal demands. 
Birds. — Here we trace the principal residence of the sense of 
touch to the foot ; but it is most imperfectly developed. There 
cannot be much sensibility, where the laminae or the scales are so 
hard and so thick as they are generally found to be at the base of 
the foot. The villous projections are, nevertheless, evident enough 
when the cuticle is peeled off. In birds that use their feet as 
hands, as in most of the parrot tribe, the cuticle is thinner, and 
the whole of the inside or lower part of the foot softer and more 
elastic. 
In other birds who search for food under the water and 
among the mud, the extremities of the mandibles are usually 
of a softer texture than the base, and possess a considerable 
degree of sensibility. 
Other Situations of the Sense of Touch. — In many quadrupeds, 
the sense of touch seems to be nearly or altogether removed from 
