548 RESPIRATORY SYSTEM OF THE DOG 
anterior to the fissure represents the apical and cardiac lobes, which are, however, 
separated only by the cardiac notch, not by an interlobar fissure, as is usual in the 
Trachea Dorsal border 
A pical lobe Cardiac 
notch 
Cardiac lobe Intermediate lobe 
Fie. 487.—Ricur Lune or Pic; Meprau View. 
1, Left bronchus (eut off); 2, 2, pulmonary arteries; 3, 3,3, pulmonary veins; 4, posterior vena cava; J, groove for 
‘ & 
anterior vena cava; 6, groove for vena azygos; 7, groove for aorta; § (placed on groove for cesophagus), lines of pleural 
reflection. Arrows indicate interlobar fissures. 
right lung. The lobulation is distinct, but the interlobular septa are thinner than 
in the ox. 
THE THYROID GLAND } 
The thyroid gland is large and is situated usually at a considerable distance 
from the larynx, but may be in contact with it. The lateral lobes are irregularly 
triangular in outline, and are two inches or more (ca. 5-6 em.) in length in a large 
adult. They are united to a considerable extent ventrally, so that an isthmus 
cannot be distinguished. The gland is related deeply to the sides and ventral face 
of the trachea, and is in contact dorsally with the aesophagus. The chief artery 
enters at the posterior extremity. 
THE THYMUS 
The thymus in young subjects is very large, extending to the larynx or even to 
the mandibular space. 
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 the broad 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 & 
median furrow (philtrum), or a deep fissure in some breeds. The cartilaginous 
