الفهرس 
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Abstract
Eleven mature birds of both sexes from each of chickens (Gallus domesticus), ducks (Saudanese ducks) and Japanese quails (Coturnix Coturnix japonica) were used for the present study. All the selected birds were mature and apparently healthy. The samples were collected and obtained from some commercial farms on Cairo-Alex. desert road, where all birds were kept and managed under the same condition of feeding , water supply and temperature . T he tongue of each bird was taken directly after sacrification and cutting the head, then immediately fixed in 2.5% gluteraldehyde for scanning electron microscope study. The tongue of chicken was appeared missile-shape. In the ducks it was elongated flat, while in the quail it was triangular in shape. The tongue was appeared formed from three parts: the apex, the body and the root, which is the fixed part of the tongue. The dorsal surface of the tongue of ducks and quails characterized by presence of longitudinal median groove along its length which divides the tongue into two symmetrical halves, while it was absent in the tongue of chickens The body and the root of the tongue from its dorsal surface was demarcated by a row of conical shaped papillae which were different in their distribution in each of chickens , ducks and quails . The tongue of the ducks was characterized by presence of another row of conical papillae in each marginal region of the tongue .Scanning electron microscopic examination of the dorsal surface of the tongue of chicken revealed that many filliform papillae are distributed all over the anterior part of the tongue , while in ducks , the dorsal surface appeared smooth, but the filliform papillae appeared as thread –like papillae distributed between and around the conical macroscopical papillae on the lateral side of the tongue. In the tongue of quail the examination revealed that large number of irregular scales ( leaf –like ) appeared on the apex of the tongue. They were shovel like with irregular borders in the body, and lamellar shape with regular borders in the middle part of the tongue. The dorsal surface of the root of the tongue is highly folded formed deep pellicae, while in the quail it was smooth but in ducks characterized by small microridges . The results revealed that these folds and microridges increase the adhesion of mucous to the epithelium. The light microscopical examination revealed that the lining epithelium covering the tongue consisted of stratified squamous epithelium and the dorsal surface of the tongue was thicker than that of the ventral one. The dorsal surface and the lingual papillae of the tongue of ducks covered by thick layer of keratin that they feed on grasses while the dorsal surface of the tongue of quails and chicken less keratinized that they feed on grains The connective tissue layer under the epithelium of the tongue in each birds consisted of connective tissue containing blood and lymph vessels, nerves and lingual salivary glands. The tongue of ducks was characterized by containing more adipose tissue than that in the tongue of chicken and quails ,also there were large number of lamellated nerve endings. The tongue of chickens, contained large aggregations of lymph nodules in the connective tissue under the epithelium. The tongue of quails characterized by presence of longitudinal blood space engorged by different blood cells. The entoglossal cartilage was formed of elastic type in the ducks and hyaline type in both of chickens and quails. T he results showed two types of salivary glands in the tongue of chickens, anterior lingual salivary glands consisted of seromucoid glands and typical mucous glands and posterior salivary glands consisted only of mucous glands. In the tongue of ducks , the anterior and posterior glands were of only mucous glands. While in the quails , the lingual salivary glands were anterior serous salivary glands and posterior mucous salivary glands . The lingual salivary glands were highly developed and more in the tongue of quail and chicken while less developed in the ducks, that the quails and chickens feed on hard grains while ducks feed on soft diet. The acid mucopolysaccharides appeared as strong alcianophilic substances in the cytoplasm of the secretory cells of mucous lingual salivary glands The neutral mucopolysaccharides appeared as PAS - positive substances in the cytoplasm of the secretory cells of mucous lingual salivary glands. In the chickens, the lateral groups of the anterior lingual glands showed weak positive reaction to alcian blue and with periodic acid Schiff techniques, respectively. While the posterior glands showing strong positive reaction to them. In the ducks, the lingual glands showing strong positive reaction to alcian blue and periodic acid Schiff respectively. In the quails, the anterior lingual glands showed negative reaction to alcian blue and periodic acid Schiff respectively, while the posterior glands showed positive reaction to them. These results have been discussed with those of the available