THE SINUSES OF THE SKULL 



99 



irregular, and intercommunicating, loculi. Between it and the corre- 

 sponding portion of the opposite sphenoidal sinus there is placed a 

 vertical septum which, however, is perforated, and consequently the 

 two sphenoidal sinuses are here placed in free communication with 

 one another. 



The other division of the sphenoidal sinus is the palatine, which is 

 bounded by the vomer, the palatine, and the lateral mass of the ethmoid. 

 This portion communicates above with the sphenoidal portion, and 

 inferiorly it is in free communication with the inner division of the 

 superior maxillary sinus. 



From what has already been stated, it will be seen that all the sinuses 

 communicate with the exterior. The superior maxillary sinus com- 

 municates directly with the middle meatus. The sphenoidal and 

 frontal sinuses communicate with the superior maxillary, and the 

 inferior maxillary sinus communicates directly with the middle meatus. 

 Moreover, since the two sphenoidal sinuses communicate with one 

 another through the perforations in the septum between them, the 

 sinuses of one side of the head are therefore in communication with 

 those of the other. 



Operations on the Sinuses. — The frontal, superior maxillary, and inferior 

 maxillary sinuses are frequently opened into, which operation is known 

 as " trephining." The operation is performed in the treatment of 

 empyema of the facial sinuses, in cases of growths such as tumours 

 in the cavities, or the presence of foreign bodies or fractured pieces 

 of bone, and also, as already referred to, in the repulsion of certain 

 molar teeth. 



The superior maxillary sinus, otherwise the antrum of Highmore, 

 was at one time trephined in the treatment of glanders, but for obvious 

 reasons, in the present state of our knowledge of this disease, such a 

 method of treatment is not now adopted. 



On account of the communication which exists between the sinuses 

 it will be understood that, as purulent matter is formed in the sphenoidal 



