60 THE EXTERIOR OF THE HORSE. 



b. The external wing or ala of the nostril is concave. Its inferior ex- 

 tremity contains a hard and resisting body, which is the termination of the curved 

 portion of the preceding cartilage. In the remainder of its extent it is soft and 

 flexible, formed only by skin and muscles. 



The muscles are all dilators. In some mammiferous aquatic animals, as 

 the hippopotamus and the seal, there are constrictors to prevent the entrance of 

 water into the respiratory apparatus. In terrestrial animals, on the contrary, the 

 closure is prevented by the rigidity of their fibro-cartilage. 



c. The commissures are formed by the junction of the ala3. The inferior 

 is round, concave, and continuous posteriorly with the floor of the nasal fossa ; 

 the superior is smaller, acute, and is continuous, with a dependency of the skin 

 called the false nostril. The latter is a cul-de-sac formed by a reflection of skin 

 on the inside of the nostril, whose bottom lies at the angle of the incisive and 

 nasal bones. It exists only in the domesticated animals, as the horse, ass, and 

 mule, and admits of the introduction of the finger. 1 



Around the margins, as are all the natural openings, it is covered 

 by soft, thin, and adherent skin, continuous with the nasal mucous 

 membrane. It is covered by two kinds of hairs : the one short, fine, 

 and numerous ; the other coarse, long, and scanty. The latter, very 

 deeply implanted and provided at their bulb with a nerve-filament, 

 are organs of tactile sensation to the animal analogous to the moustaches 

 of carnivora. They are more or less abundant, according to the quality 

 of the race. The habit of cutting them with the scissors, singeing, or 

 extracting them entirely, with the view of giving lightness to the head, 

 is to be reprimanded. 



Beauty. The absolute beauty of the nostril resides in its 

 width and in its separation from the lips, because it is proportional to 

 the capacity of the respiratory apparatus. In solipeds, buccal respira- 

 tion is prevented by the development of the soft palate. All the air 

 which enters the lungs must pass through the nostrils, whose amplitude 

 should therefore be in relation with the former. It follows, then, 

 a priori, that the greater these orifices are the greater will be the vol- 

 ume of air which enters the lungs during inspiration ; that conse- 

 quently the development of the lungs will always be correlative to the 

 dimensions of the nostrils, and vice versa. There is no exception to 

 this rule, and the reverse has never been observed in nature. Small 

 nostrils are an absolute defect, and associate themselves with a chest 

 that is narrow and but little spacious. 



Movements. The movements of the nostrils are almost imper- 



1 On the floor of the nostril, anterior to the mucous membrane, is the orifice of the lachrymal 

 canal. It is round, excavated, punched-out, and resembles a glanderous chancre, for which it 

 must not be mistaken. In the mxile and in the ass it is situated on the superior commissure. It 

 is usually single, but may be double or even triple. 



