550 



RESPIRATORY SYSTEM OF THE DOG 



outward from the septal cartilage in the floor of the nostril, and another lamina 

 supports the alar fold of the ventral turbinate bone; these may be termed accessory 

 nasal cartilages (Cartilagines nasi accessoriffi) . 



The length of the nasal cavity varies greatly in different breeds, correspond- 

 ing, of course, to the length of the face. The cavity is roomy, but is very largely 

 occupied by the turbinates and the lateral masses of the ethmoid bone. The 

 middle meatus is short and narrow, and divides posteriorly into two branches : the 

 upper branch leads to the ethmoidal meatuses; the lower branch joins the ventral 



meatus. The ventral meatus is very small in 

 its middle part, owing to the great develop- 

 ment here of the ventral turbinate. The 

 posterior part of the nasal cavity is divided 

 by the lamina transversalis into an upper olfac- 

 tory part and a lower respiratory part. The 

 \K sinuses have been described (vide Osteology). 



THE LARYNX 



The lar j'nx is relatively short. The lamina 

 of the cricoid cartilage is wide; the arch is 

 grooved laterally. The laminae of the th3rroid 

 cartilage are high, but short; they unite ven- 

 trally to form the body, on which there is an- 

 teriorly a marked prominence, and posteriorly 

 a deep notch. The oblique line on the lateral 

 surface of the lamina is prominent. There is 

 a rounded notch (Fissura thyreoidea) below the 

 short anterior cornu for the passage of the an- 

 terior laryngeal nerve. The posterior cornu is 

 strong, and has a rounded surface for articula- 

 tion with the cricoid cartilage. The arjdienoid 

 cartilages are relatively small, and have between 

 them a small interarytenoid cartilage. The 

 epiglottis is quadrilateral; its lower part or 

 stalk (petiolus) is narrow, and fits into the 

 angle of the thyroid cartilage. The cuneiform 

 cartilages (Cartilagines cuneiformes) are large 

 and somewhat crescent shaped; they are not 

 fused with the epiglottis. 



The false vocal cords extend from the 

 cuneiform cartilages to the thyroid. The true 

 vocal cords are large and prominent. The 

 large lateral ventricle is a long slit parallel with 



the anterior margin of the true vocal cord. The laryngeal saccule is extensive and 



lies lateral to both true and false vocal cords. 



The crico-thyroid muscle is thick. The hyo-epiglotticus is well developed, 



and is double at its hyoid attachment. The ventricularis or anterior part of the 



thyro-arytenoideus arises on the cuneiform cartilage. Hence Lesbre has suggested 



the name cuneo-arytenoideus for it. 



Fig. 490. — Aditus Laetngis and Related 



Steuctuhes of Dog, 

 The pharynx and CESophagus have been cut 



along the mid-dorsal line and reflected. 



1, Epiglottis; i?, 2, corniculate cartilages; 

 3, 3, ari'tenoid cartilages; 4, glottis; 0, wall of 

 pharj'nx; &, cesophagus; 7, limen oesophagi; S, 

 posterior pillar of soft palate; 9, median sulcus 

 of tongue; iO, vallate papillse; 11, conical pa- 

 pillee of root of tongue; 12, 1,2, tonsils (shown 

 by opening up tonsillar sinus). 



THE TRACHEA AND BRONCHI 



The trachea is practically circular in cross-section at its ends, but the inter- 

 vening part is very slightly flattened dorsally. It contains about forty to forty- 



