Sauropsida: Class Aves 



521 



Fig. 409. Air-sacs and canals of pigeon, (cl, c 3 ) Intertransverse canals; (da 1 — da 2 ) 

 axillary sac and its ventral diverticulum; (dc) canal for ribs; (dfa, dfp) anterior 

 and posterior femoral ducts; (dot) infraclavicular canal; (ds) subscapular sac; (dst) 

 sternal canal; (pc) preacetabular canal; (sac?, sas) right and left abdominal sacs; 

 (sc) cervical sac; {sia, sip) anterior and posterior intermediate sacs. (After Miiller. 

 Courtesy, Kingsley: "Comparative Anatomy of Vertebrates," Philadelphia, The 

 Blakiston Company.) 



410) : cervical, lying on either side of the base of the neck (but single 

 and median in the common chicken) ; interclavicular, commonly 

 fused into a single median sac, in front of the sternum and between the 

 two prongs (clavicles) of the furcula; anterior thoracic and posterior 

 thoracic, situated as the names indicate, and ventral to the lungs; 

 abdominal, the largest of all, lying dorsally in the abdominal cavity. 

 Each cervical sac usually connects with a smaller axillary sac lying 

 just beneath the skin under the base of the wing. All of the sacs are 



