THE NASAL FOSS^. 1409 



cribriform plate is also fractured. On the other hand, the rich glandular supply of 

 the mucous membrane, which makes the usual mucous secretion exceptionally free, 

 may, in a post-traumatic coryza, result in a watery discharge of such quantity as to 

 suggest the escape of the cerebro-spinal fluid. Emphysema within the orbit and 

 under the skin may result from the communication of the nose with the ethmoidal or 

 frontal sinuses. In the effort to keep the nose clear of blood by blowing, the air is 

 forced into the subcutaneous tissues. 



In fractures at the lower part, the deformity is frequently lateral, because of 

 the greater exposure to side blows, and the tendency of the cartilaginous al^e and 

 septum to avoid crushing. In the upper part depression is more likely, because of 

 the tendency to escape any but forces from in front, the greater force necessary to 

 produce the fracture, and the presence of a bony septum underneath, which crushes 

 rather than bends. 



When the deformity has been replaced there are no strong muscles to repro- 

 duce it, so that little or no effort is necessary to maintain the fragments in position. 

 The deformity must be reduced early and the reduction maintained, because owing 

 to the free blood supply, union is usually rapid, sometimes occurring in a week. 

 One must bear in mind in reducing the deformity that the roof of each nasal fossa is 

 not more than 2-3 mm. wide, and that, therefore, a narrow rigid instrument is 

 necessary to press the fragments upward into their normal positions. 



THE NASAL FOSS^. 



The cavity of the nose is divided by the median septum into two nasal fossae 

 which extend from the anterior to the posterior nares, or choancz, through which 

 they open into the naso-pharynx. They communicate more or less freely with the 

 accessory air-spaces within the frontal, ethmoid, sphenoid and maxillary bones, into 

 which, as a lining, the mucous membrane of the nasal fossae is directly continued. 



Seen in frontal section (Fig. 1176), each fossa is triangular in its general outline, 

 the apex being above at the narrow roof and the base below on the floor. The 

 smooth median wall is approximately vertical and meets the floor at almost a right 

 angle, while the sloping lateral wall is modelled by the projecting scrolls of the three 

 turbinates, which overhang the corresponding meatuses. In sagittal sections 

 (Fig. 1 174) the contour of the fossa resembles an irregular parallelogram from which 

 the upper front corner has been cut ofT, so that in front the upper border slopes 

 downward to correspond with the profile of the outer nose. The greatest length of 

 the fossa, measured along the floor, is from 7-7.5 cm. (23/^-3 in.) and its greatest 

 height from 4-4.5 cm. The width is least at the roof, where it is less than 3 mm., 

 and greatest in the inferior meatus a short distance above the floor, where it expands 

 to from 15-18 mm. 



The Vestibule. — The anterior part of the fossa, immediately above the open- 

 ing of the nostril and embraced by the outer and inner plates of the lower lateral 

 cartilage and adjoining portion of the septum, is somewhat expanded and constitutes 

 the vestibule (vestibulum nasi), a pocket-like recess prolonged towards the tip being 

 \he ventricle (recessus apicis). These spaces are lined by delicate skin, directly con- 

 tinuous with the external integument and tightly adherent to the underlying cartilage, 

 and, in the lower half of the vestibule, containing numerous sebaceous glands and 

 hairs. In the vicinity of the nostril the hairs, known as vibrissa;, are coarse and 

 long and curved downward to afford protection to the nasal entrance. Over the 

 upper part of the vestibule, the skin is smooth and closely attached to the lower 

 lateral cartilage, the upper margin of the outer plate projecting as a slightly arching 

 ridge, the limen vestibuli, which forms the superior and lateral boundary of the vesti- 

 bule and marks the line of transition of the skin into the mucous membrane that lines 

 the remaining parts of the nasal fossa. 



Above and beyond the vestibule, the nasal fossa rapidly expands into a 

 triangular space, the atrium nasi, that lies in advance of the entrance into the middle 

 nasal meatus. Above and in front the atrium is bounded by a low and variable 

 ridge, the agger nasi, that represents a rudimentary naso-turbinate, which in many 

 mammals attains a large size. The space Iving in front of the agger, extending 



89 



