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 nostrils 

 are Avide 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 ofi" 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 inaxillary-bone, containing the incisor teeth, or 

 nippers. 



