464 



RESPIRATORY SYSTEM OF THE PIG 



In the sheep the costal attachment of the diaphragm resembles that of the 

 horse, and the basal part of the lung corresponds thereto. The lobation of the 

 lungs resemliles that of the ox, but the lobulation is very indistinct. The pleural 

 sacs extend under the first lumbar vertebra. 



THE THYROID GLAND 



The lobes of the thyroid gland are more extensive and paler in color than in 

 the horse; they extend further forward, overlapping the crico-pharyngeus muscle 

 to a small extent, and come in contact dorsally with the oesophagus. They are 

 flattened, and have an irregular, lobulated surface. In the young subject the isth- 

 mus is well developed, being al)out half an inch (ca. 1 to 1.5 cm.) in width. 



Accessory thyroids may be found, and parathyroids also occur near the pos- 

 terior extremity or inner surface of the lateral lobes of the thyroid. 



Apical lobe 

 \ 



\ 



'-^: 





'^ ^o6. 



oove fur 

 phagus 



(die surface 



Apex \ I 



Cardiac notch 



Fig. 370. — Right Lung of Sheep, Mediastinal Aspect. 

 Hardened in silu. B, Bronchus; P.a., pulmonary artery; P.v., pulmonary vein; V.c, posterior vena cava; 



L.g., bronchial lymph-Rland. 



THE THYMUS GLAND 

 The thymus is pale and distinctly lobulated. It is much larger in the calf 

 than in the foal, weighing at five or six weeks about 15 to 25 ounces (ca. 425 to 600 

 grams). The cervical part is specially large, thick, and compact; it extends 

 to the thyroid gland. It undergoes atrophy slowly and remnants of the 

 thoracic part often remain even in advanced age. 



RESPIRATORY SYSTEM OF THE PIG 

 THE NASAL CAVITY 

 The nostrils are small, and ar(> situatecl on tlie flat anterior surface of the 

 rostrum or snout (Rostrum suis). The latter is a short cylindrical jirojection, 

 with which the upper lip is fused, and is circumscribed l)y a i)roniin(^nt circular 

 margin. The skin on the snout is thin and highly sensitive; it presents small 

 pores, and scattered over it are fine short hairs. In the snout between the nostrils 

 is the OS rostri, which is to be regarded as a special development of the extremity of 



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