34 



NORMAL HISTOLOGY. 



The glands of the respiratory region are very numerous, although 

 varying in size, tubo-alveolar in form and, for the most part, mixed mucous 

 in type. The chief ducts open on the free surface by minute orifices barely 



Mucous 

 membrane 



Vomerine 



FIG. 431. Section of mucous membrane lining FIG. 432. Section of mucous membrane lining 



frontal sinus. X 280. (Preparation by Dr. J. P. sphenoidal sinus. X 280. (Preparation by Dr. J. P. 

 Tunis.) Tunis.) 



distinguishable with the unaided eye. Their deeper ends branch irregularly 

 into tubes that bear the ovoid terminal alveoli. The latter are lined with 

 mucus-secreting cells, between which lie the crescentic groups of serous cells 

 that stamp the glands as mixed (Stohr). In exceptional cases exclusively 

 serous glands are also encountered. 



The nasal fossae communicate with a number of remarkable cavities, the 

 accessory air-spaces, hollowed out within the surrounding bones, which 



are filled with air and lined by 

 mucous membrane directly 

 continuous with that of the 

 meatuses. These pneumatic 

 spaces include the maxil- 

 lary, the frontal and the 

 sphenoidal sinuses and the 

 ethmoidal air-cells , all paired 

 and within the corresponding 

 bones. The mucous mem- 

 brane lining these spaces 

 resembles in general that of 

 the adjoining nasal fossae, 

 but is very much thinner. 

 It includes a stratified cili- 

 ated columnar epithelium, 

 invaded by numerous lymph- 

 oid cells, a delicate basement 

 membrane and a tunica pro- 

 pria, poor in elastic fibres 

 and inseparably blended with 

 the periosteum, of which, in 

 fact, it is part. Small scat- 

 tered mucous glands occur 

 in meagre numbers in the 

 maxillary sinus, being most 

 plentiful in the vicinity of the opening into the nasal fossa. 



Jacobson's Organ. Mention should be made of the rudimentary 

 structure (organon vomeronasale} found in man, almost constantly in the 

 new-born child and frequently in the adult, as a representative of the organ of 



FIG. 433. Part of frontal section through nasal fossae of kitten, 

 showing organs of Jacobson. X 20. 



