LECTURE IX 

 THE RESPIRATORY ORGANS 



476. The Nose, which is divided by a bony and cartilaginous 

 septum {septum nasi) into two chambers — the right and left nasal 

 chambers; the larynx ; the trachea, or windpipe ; and the bronchi 

 and bronchial tubes ; the lungs ; the thorax, or chest ; the 

 pleurae ; and the diaphragm. 



477. Nasal Chambers (Plate XX XV I., No. J).— The right and 

 left nasal chambers of the horse each contains two bones — one above 

 (the superior) and one below (the inferior). They are made up of 

 very fine sheets of bone, covered with mucous membrane, and rolled 

 up like a Turk's turban, and are called turbinated bones. These 

 bones give an extensive surface for the distribution of the nerves 

 concerned in the sense of smell, as well as for the ramification of the 

 bloodvessels which warm the air as it passes over their surface to 

 enter the windpipe. The membrane covering them clears the air 

 from solid particles of dust before it passes to the sinuses of the head 

 or, by way of the windpipe, to the lungs. The cow has three turbinated 

 bones in each chamber, also a canal (called ' Jacobson's canal') in 

 the floor of the nasal chamber, which communicates with the mouth. 

 The cavities in the horn cores of ruminants are also in communica- 

 tion with the nasal chambers. 



478. Larynx (Plate XXX VI., No. 6) is situated at the back of 



the throat, and is composed of five pieces of cartilage, or gristle, of 



different shapes, which are so placed and joined that they are movable 



on one another, thus regulating the inlet and outlet of the air. These 



cartilages are named the thyroid, cricoid, arytenoid (2), and epiglottis. 



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