DIFFERENTIATION OF THE OLFACTORY EPITHELIUM IN SHEEP IN ONTOGENY USING SCANNING ELECTRON-MICROSCOPY

The method of scanning electron microscopy was used to stud; the diffe rentiation of the olfactory epithelium and the formation of the surfac e of the olfactory epithelium of sheep on the 74th and 79th days of pr enatal period, on the day of birth, 30 days after birth and in an adul t animal of 730 days of age. From the 74th day of i.u. development, th e olfactory endings on the surface of the olfactory epithelium were fo und to be on different levels of development. Their amount gradually i ncreased prior to birth as did the amount of olfactory cilia growing o ut of these olfactory endings. The cilia were formed first, in the ran ge of proximal segments; distal segments of cilia appeared later, in d ependence on the degree of differentiation of the olfactory endings. N o microvilli were yet formed on the apical segments of the sustentacul ar cells of a 74-day old foetus. They began to differentiate after the 79th day of i.u. development and most of them were not formed until t he immediate perinatal period. In the postnatal period the amount of n ewly formed olfactory endings decreased, but the number and length of olfactory cilia continued to increase. Areas of regenerating olfactory epithelium and individual differentiating olfactory endings could als o be observed in an adult animal.