52 TOPOGRAPHIC AND APPLIED ANATOMY. 



FIG. 19. The lateral wall of the left nasal cavity. Almost the entire middle turbinated bone has been excised 

 in order to expose the structures and orifices situated beneath it. A piece has been removed from the anterior portion 

 of the inferior turbinated bone. The original borders of the turbinated bones are indicated by dotted lines. The superior 

 turbinated bone is intact. The orifices of the left sphenoidal and frontal sinuses are shown by arrows. 



FIG. 20. Sublingual region, shown on a median section. The mucous membrane has been divided and the 

 tongue is turned downward. 



Another method of opening the sinus is to go through its inner wall, i: e., through the thin 

 outer wall of the nasal fossas below the inferior turbinated bone (see Figs. 15 and 19). An in- 

 cision may be made through the cheek and the anterior wall of the sinus chiseled open below the 

 infraorbital foramen. The fourth method of attacking the sinus is to chisel through its anterior 

 wall above the alveolus from the vestibulum oris [i. e., through the canine fossa external to the 

 elevation caused by the canine tooth. ED.] (see Fig. 16). The orifice of the maxillary sinus is 

 situated beneath the middle turbinated bone and cannot be distinctly seen until this structure has 

 been removed. Attempts to reach this concealed orifice in the living are usually fruitless. [The 

 normal opening into the maxillary sinus is usually found near the most dependent portion of the 

 hiatus semilunaris and under cover of the middle turbinated bone. ED.] In addition to the main 

 orifice, there is frequently an accessory opening at or beneath the margin of the middle turbinated 

 bone (see Fig. 19). Since the inner wall of the maxillary sinus is formed by only a thin osseous 

 lamina and partly by mucous membrane alone, it will be readily understood that tumors arising 

 within the sinus (carcinomata, for example) grow inward into the nasal fossa. The roof is thin 

 also and may be perforated by tumors originating in the sinus; these tumors may grow into the 

 orbit and dislocate the eyeball. In such cases the infraorbital nerve running in the roof of the 

 sinus may be affected and give rise to neuralgic symptoms. Such symptoms may also be pro- 

 duced by a fracture of the superior maxilla, in which the air from the sinus may gain access to the 

 subcutaneous tissues of the cheek or to the orbital cavity and cause emphysema. Tumors of the 

 maxillary sinus may also displace the anterior wall of the cavity and grow toward the face. If they 

 extend posteriorly, they reach the spheno-maxillary fossa, and from here they may, under certain 

 circumstances, invade the pharynx or grow into the cranial cavity through the base of the skull. 



The frontal sinuses are also of importance to the physician. They have been previously 

 described upon page 19. Fig. 4 shows the right frontal sinus, which has been opened from the 

 forehead and in the depths of which the entrance into the nasal fossa may be seen. In catarrhal 

 inflammations leading to a closure of the communication between the sinus and the nasal cavity 

 (see page 19), the sinus may be opened in this manner and the contracted orifice dilated. In the 

 nasal cavity this orifice is situated below the middle turbinated bone in the middle meatus at the 

 highest portion of the slit-shaped infundibulum (see Fig. 19). During life it is usually impossible 

 to probe this orifice from the nostril. 



[By removing the anterior end of the middle turbinated bone it is possible to pass a probe into 

 the naso-frontal duct or infundibulum. By keeping the end of the probe pressing against the 

 turbinated side we avoid the likelihood of entering into the anterior ethmoidal cells, which form 

 Y-shaped diverticuli leading from the naso-frontal duct. ED.] 



The paired sphenoidal sinuses are situated in the most posterior portion of the roof of the 

 nasal cavity and very close to the base of the skull. The superior wall, situated in the region of 

 the sella turcica, is very thin, and tumors growing from the sinus may consequently easily extend 



3 n> 3 J J G 



