SOME TOPOGRAPHICAL AND MORPHOLOGICAL STUDIES ON AIR SACS OF DOMESTIC PIGEON (COLUMBA LIVIA DOMESTICA) USING CORROSION CASTS

The work was carried out on fifteen adult pigeons of both sexes. The gross morphological features of the air sacs were thoroughly investigated using Vinyl chloride acetate corrosion casts. It was found that the pigeon as an example of a powerful flying bird had 4 pairs of transparent air sacs ( cervical, cranial thoracic, caudal thoracic  and abdominal ), in addition to an unpaired interclavicular sac. They were symmetrically occupying either side of the body cavity.  The cervical sacs aerated the cervical vertebrae approximately from the 3rd or 4th as well as the first two thoracic vertebrae. The single interclavicular air sac was the most complicated among all air sacs in the pigeons. It occupied the ventral part of the thoracic inlet and overlay the cervical sacs laterally and connected with their cranial ends. Meanwhile, the interclavicular sac gave off extrathoracic humeral and axillary diverticula, which pneumatized the humeri and bones of the  pectoral girdles. It was also observed that the cranial and caudal thoracic air sacs showed no bony communications, and never aerate bones. The paired abdominal sacs were larger tfin the other air sacs. They enclosed between their medial surfaces the intestinal tract, kidneys and the gonads. Also, each of them sent a diverticulum which ventilated the interior of the pelvic bone and the synsacrum. The obtained results of the air sacs in the pigeon were discussed with the findings given by previous authors in other species of birds.