1372 



SUKFACE AND SUKGICAL ANATOMY. 



or the posterior wall. The muco-periosteal lining, which readily strips from the 

 bone, is thin and pale, and provided with mucus- secreting glands. 



In many individuals, by the aid of trans-illumination, the extent of the sinuses and the 

 position of the intervening septum may be mapped out upon the forehead. For this 



Septum of frontal sinuses Crista galli 

 Right frontal sinus 



Left frontal sinus 



Floor of anterior fossa of skull 



Anterior part of roof of orbit 



Anterior extremity of middle 

 concha 



Cartilage of nasal septum 



Anterior extremity of inferior 

 concha' 



Frontal process of 

 maxilla 



Ala nasi 



FIG. 1078. VERTICAL FRONTAL SECTION THROUGH THE NOSE AND FRONTAL SINUSES. 



purpose a small electric lamp is placed against the floor of the sinus, beneath the medial 

 third of the supra-orbital margin. 



The skiagraphic appearances of the frontal sinuses are of importance clinically and 

 give more information than trans -illumination. Antero- posterior skiagrams show the 

 vertical extent of the sinus, the degree of asymmetry, and the presence or absence o 

 recesses, with their intervening septum. An orbital expansion is indicated by a well- 

 defined shadow with a sharply-defined upper margin, extending laterally parallel to and 

 immediately above the medial half or more of the supra-orbital margin. A profile 

 skiagram shows not only the height of the sinuses but also their antero-posterior diameter, 

 as well as the degree to which they extend backwards between the roof of the orbit and the 

 floor of the anterior fossa of the skull. While it is exceptional to meet with frontal sinuses 

 before the age of five years, they are almost invariably present by the seventh or eighth year. 



In exploring the sinus, the opening in the bone should be made close to the median 

 plane, immediately above the root of the nose. In marked cases of deviation of the 

 septum one sinus may extend so far across the median plane of the forehead as to reduce 

 the other to a mere slit ; in such cases the surgeon may fail to open the diseased sinus 

 when the operation is performed through the anterior wall. The sinus frequently contains 

 incomplete partitions, which give rise to the formation of pockets and recesses usually 

 found towards the lateral angle of the sinus ; when dealing with chronic suppuration of 

 the sinuses, special attention should be paid to these recesses as well as to the backward 

 extension of the cavity along the orbital roof. The anterior ethmoidal cells are closely 

 related to the thin medial or nasal portion of the floor of the sinus and its duct of exit ; 

 hence suppuration very frequently co-exists in both cavities. In some cases pus flows 

 directly from the frontal sinus and infundibulum along the hiatus semilunaris into the 

 maxillary sinus, which opens into the back part of the hiatus. Killian's operation for 

 the cure of chronic suppuration in the sinus consists in the removal of its anterior and 

 inferior walls, the supra-orbital margin being left to prevent the falling in of the eyebrow. 

 By removing the frontal process of the maxilla good access may at the same time be 

 obtained to the ethmoidal cells and free drainage established between the frontal sinus 

 and the nasal cavity. (Skiagraphs of Frontal Sinuses, see Plates I. and II.) 



