Lipid droplets in the lining epithelium of the crop of Columba livia.

Presence and distribution of lipid were studied in the lining epithelia of three regions of the pigeon (Columba liva) crop: lateral lobes, median region near the cervical esophagus and median region near the thoracic esophagus. During the resting phase of the 'milk gland', insulated lipid droplets were observed within the lining epithelium of the three regions studied. On the other hand, during the activity of the 'milk gland' (under action of exogenous prolactin and in natural incubation), only the lateral lobes showed a remarkable increase in the amount of lipid, whereas both median regions showed only an inexpressive increase of lipid within their epithelium.