Fig. 39. The Nasal Cavity with the Opening of its Accessory Sinuses. 



The Sagittal Section has been made a little to the right of the Nasal Septum, 

 Sphenoidal and Frontal Septum. Portions have been removed from the 

 Turbinated Bones in order to exhibit the orifices of the accessory Cavities. 

 Into some of these directors have been introduced. The Tongue has been almost 

 completely removed to shew the Tonsil. 



The Accessory Cavities of the Nose may be considered Embryologically 

 as Ethmoidal Cells which have grown be3'ond the area of the Labyrinth. They 

 become formed by the resorption of the bony walls of the Nasal Cavity. The 

 mucous membrane follows this process and grows into the accessory cavities. The 

 Nasal Duct opens, covered by the inferior turbinated bone, into the inferior nasal 

 meatus. This meatus readily allows the introduction of a canula into the opening 

 of the Eustachian Tube which lies in the Outer Wall of the Phar}-nx. At this 

 opening is the EUSTACHIAN Cushion, behind it the Fossa of RoSENMtJLLER. 

 Under the Mucous Membrane covering the roof and back of the Pharynx is a 

 mass of lymphoid tissue (Pharyngeal Tonsil) which in the middle line exhibits a 

 recess of variable shape, grooved, saccular or double (Pharyngeal Bursa). 



Into the middle meatus, at the Anterior part of a ridge, is the opening of 

 the Frontal Sinus (Infundibulum), at the posterior part the aperture of the iVntrum 

 of HiGHMORE. The communication between the Antrum and the Nose is not always 

 single, it may be double. 



We have already stated (in Fig. 2 Text) that the opening of the Antrum is 

 in a most unfavourable position for drainage, because it is situated at the top 

 of the cavit}^ The Anterior Ethmoidal CeUs also open into the Middle Meatus 

 (cf. Fig. 2) directly above the aperture of the Antrum. The Superior Meatus con- 

 tains the opening for the Posterior Ethmoidal Cells. Above the Superior Turbinated 

 Bone is the aperture for the Sphenoidal Sinus into which guided by a mirror one 

 can introduce a canula through the Anterior nares. The aperture of the Sphenoidal 

 Sinus is not situated at the lowest part of the cavity and is consequently not 

 favourable for drainage. All the accessory nasal cavities are Uned with mucous 

 membrane. 



The figure shews the Tonsil situated between the two pillars of the Fauces. 

 About one inch long and composed of Lymphoid Tissue it only becomes distinctly 

 visible when the tongue is depressed. (Cf. Fig. 53.) 



