n6 A MANUAL OF VETERINARY PHYSIOLOGY 



turbinated bone, ethmoid cells, and a portion of the middle 

 meatus ; the respiratory channel, on the other hand, lies on the 

 inferior part of the nasal chamber , and comprises the inferior 

 meatus, inferior turbinated bone, part of the superior, and part 

 of the middle meatus. The superior meatus may be said to be 

 for the purpose of smell, the inferior for respiration, while the 

 middle connects the sinuses of the face with the nasal passages. 



The termination of the two turbinated bones and their con- 

 nection with the external nostril is not as a rule fully described 

 in anatomical works. The soft, fleshy appendix of the superior 

 turbinated bone having divided and then reunited, is inserted 

 into the cartilage of the nostril. In Fig. 47 the portion of the 

 nostril marked Ex would have to be lifted upwards and 

 outwards to see the seat of insertion of this bone. The lower 

 turbinated bone also terminates in a fleshy appendix much 

 larger than that of its neighbour. It divides : one branch is 

 inserted into that portion of the nostril indicated Ex in Fig. 47, 

 close, but external to, the appendix of the upper bone ; while the 

 inferior division is inserted into the floor of the nostril. In order 

 to see its insertion, the portion of the nostril In (Fig. 47) 

 would have to be pulled outwards. The opening into the nasal 

 chambers is formed, therefore, between the two fleshy termina- 

 tions of the inferior turbinated bone, and in forced respiration 

 these two divisions separate widely. 



The Glottis.— The air having been warmed by passing over 

 the septum and turbinated bones, enters the glottis, the arytenoid 

 cartilages being separated to a greater or less extent to enlarge 

 the opening. In quiet respiration this enlargement of the 

 glottis is not very marked, but during work the cartilages are 

 drawn powerfully upwards and backwards, and the V-shaped 

 glottis fully opened (Figs. 54 and 56, p. 147). It is a remarkable 

 fact that the laryngeal opening should be so relatively small, 

 considering the diameter of the trachea and the size of the nasal 

 openings. 



During inspiration the larynx and trachea descend slightly, 

 while they ascend during expiration. This is particularly well 

 seen in horses during the hurried respirations of disease, pro- 

 ducing a well-marked rhythmical movement of the laryngeal 

 region and base of the tongue. 



The Facial Sinuses are cavities in the face communicating with 

 the nasal chambers ; they are of considerable size, occupying 

 nearly the entire facial region, and they give the needful bulk 

 to the head without adding to its weight ; they are lined by a mem- 

 brane which is continuous with that of the nose. These sinuses 

 are filled with air which enters them through a foramen at the 

 posterior part of the middle meatus ; during every act of respira- 



