SECTION OF THE INTERNAL ANATOMY OF THE HEAD. 197 
this expansion of the olfactory nerves is to supply the place 
of touch, and what is acquired by experience by man. It is 
by this exquisite sense of smell that the horse selects such 
food as is best calculated for his nutriment, and is enabled 
to reject what is poisonous. By smell he judges of the 
quality of his food in a domestic state, and examines a 
stranger. The horse will recognise his master or favourite 
groom by the sense of smell, and frequently expresses such 
recognition by a neigh. These cavities are also the organs 
of voice; the sound reverberates through them, and in¬ 
creases in loudness as through the windings of a French- 
horn. All the air which passes to and returns from the 
lungs must go through the nostrils, as he can breathe 
through the nose only. The nostrils ought therefore to be 
large and expanded. The skin also which covers them 
should be thin and elastic, that they may the more readily 
yield when the animal requires a greater supply of air while 
trotting hard or galloping. In the race-horse the nostril? 
are wide and flexible, while in the cart-horse they are con¬ 
fined, and surrounded by a quantity of cellular substance 
and thick skin. 
There are besides four distinct cartilages attached to the 
nostrils, which are exceedingly elastic, and bring them 
back to their ordinary dimensions whenever the muscles 
cease to act. The bones also of the nose, n, plate viii. fig. 2, 
and n n , fig. 3, are tapered off to a point, to give a wider 
range for the action of the muscles ; while the cartilages 
are so constructed as not only to discharge the office above 
referred to, but also to prevent this tapering point of bone 
from injury. 
u. The palate. 
v. The inferior raaxillary-bone, containing the incisor teeth, or 
nippers. 
