218 



THE ANATOMY OF THE HORSE. 



The Inferior Extremities of the nasal fossae are termed the inferior nares 

 or, in common hmguage, the nostrils. They have already been 

 described (page 176). 



Fig. 2.5. 

 Transverse Section through the Nasal Chambers. 

 1. Anterior turbinated bone; 2. Posterior turbinated bone; 3. Anterior meatus; 4. Middle 

 meatus; 5. Posterior meatus ; 6. Septum nasi. 



The Superior Extremities are separated from the cranial cavity by the 

 cribriform plate of the ethmoid bone, and are occnpied by the lateral 

 masses of the same bone. Below and behind these are the superior 

 nares — the large patent orifices by which the nasal fossae communicate 

 with the pharynx, the right and left openings being separated by the 

 vomer bone. 



The following openings into the nasal fossa should be found : — 

 1. The Opening of the Lachrymal Duct {ductus ad nasum). — Look for 

 this on the floor of the nasal fossa, a few inches within the nostril. It 

 is easily seen in the living animal, and has already been referred to in 

 connection with the nostril (page 176). It is a small opening (about the 

 same diameter as a goose quill) with a circular outline, having an appear- 

 ance as if a small circle of skin had been punched out. The opening, it 

 is to be observed, is on the skin, and not the mucous membrane, taking 

 the presence of hair as distinguishing the former from the latter. The 

 duct passes upwards beneath the mucous lining of the middle meatus 

 until it enters the osseous tube that conducts it to join the lachrymal 



