466 



RESPIRATORY SYSTEM OF THE DOG 



TRACHEA AND BRONCHI 



The trachea is circular in cross-section, and contains thirty or more rings 

 "which almost meet dorsally. A special bronchus is detached for the apical lobe 

 of the right lung, as in the ox. 



THE LUNGS (Figs. 324, 325) 



The right lung has four or five lobes, according to whether the apical is sub- 

 divided or not. The left lung reseml;)lcs that of the ox in form and lobation. The 

 lobulation is chstinct, l)ut the interlobular septa are thinner than in the ox. 



Groove for nesuphagus 



Dofsa.1 harder 



Trachea 



Apical lobe 



Diaphragmatic lobe 

 - {base) 



Cardiac lobe 



Mediastinal lobe 

 Fig. 371. — Right Lung of Pig, Mediastinal Aspect. 

 Hardened in situ. B, Left bronchus; V., pulmonary veins; ,4., pulmonary artery; /, lymph glands. 



THE THYROID GLAND 



The two lobes of the thyroid are long and flattened; they are situated close 

 together, on the ventral surface of the trachea, extending as far forward as the 

 cricoid cartilage. The gland is dark red in color. 



THE THYMUS 



The thymus is very large, extending to the larynx or even to the submaxillary 

 space in young subjects. 



RESPIRATORY SYSTEM OF THE DOG 



THE NASAL CAVITY 



The nostrils are situated on the muzzle, with which the upper lip blends. They 

 are shaped somewhat like a comma, with ihv broatl part next to the septum and 

 the narrow part directed backward and outward. The skin around the nostrils 

 is bare, usually black, and in health moist and cool. The muzzle is marked by a 

 median' furrow (philtrum) or a deep fissure in some breeds. The cartilaginous 

 framework is formed essentially by the septal cartilage and the parietal cartilages 

 which proceed from it. The septal cartilage projects lieyond the premaxilla, and 

 is much thickened at its extremity; it gives off from its upper and lower margins 



