Plate XXV. 



Es OF Left Side 



Supra-orbital foramen. 2. Trephined opening into frontal sinus. 3. Trephined opening into superior inaxillary 



us. 4. Elevation caused by levator labii superioris proprius muscle. 5. Trephined opening into inferior maxillary 



us. 6. Direction of fibres of levator labii superioris alseque nasi muscle. 7. Reflected plate of frontal bone. 



8. Frontal sinus. 9. Lateral mass of ethmoid, ic. Course of osseous tube containing ductus ad nasum. 11. Nasal 



turbinated bone. 12. Superior maxillary sinus. 13. Septum separatingthe maxillarysinuses. 14. Inferior maxillary sinus. 



