106 SKELETON. 



not more than three lines. The double row of foramina in the 

 cribriform plate is very well seen, also the foramen at its ante- 

 rior part for transmitting the nasal branch of the ophthalmic 

 nerve; the groove formed by the latter on the posterior face of 

 the os nasi is also very distinct. 



The bottom of either nostril, called its floor, is formed by the 

 palate process of the superior maxillary and palate bones; it is 

 somewhat concave, and about half an inch wide; its width, how- 

 ever, is not uniform, as it is sometimes wider or narrower in 

 front than it is in the middle. In it is seen the upper orifice of 

 the foramen incisivum at the anterior point of the vomer. 



The external or orbitar surface of the nasal cavity is very ir- 

 regular, presenting a number of projections and fossoe 3 over 

 which the Schneiderian membrane is displayed. It is formed 

 by the upper maxillary, the ethmoid, the unguiform, the palate, 

 the nasal, the lower spongy, and the sphenoid bones. In the 

 middle of the posterior part of the ethmoid is the upper meatus 

 of the nose, a deep fossa, bounded above by the cornet of Mor- 

 gagni, and receiving the contents of the posterior ethmoidal 

 cells, by one or more orifices. At the posterior termination of 

 this fossa is the spheno-palatine foramen. The middle spongy 

 bone forms the lower boundary of the ethmoid ; between it and 

 the lower spongy or turbinated bone, is the middle meatus of 

 the nose, a fossa of considerable size, but of unequal surface. 

 At the fore part of the middle meatus is a vertical projection, 

 formed by the ductus ad nasum and lachrymal fossa. Just 

 behind this ridge, is an interval between it and the anterior 

 part of the ethmoid, through which the os uriguis may be seen. 

 When the middle spongy bone is broken off, immediately be- 

 neath its anterior part a channel obliquely vertical, is seen in 

 the ethmoid, which leads to the frontal sinus, through the an- 

 terior ethmoidal cell. This cell, from its peculiar shape and 

 function, is called infundibulum. Behind this oblique channel 

 is another oblique channel, parallel, but smaller; in which seve- 

 ral orifices may be found of the anterior ethmoidal cells. The 

 anterior channel has, indeed, for the ethmoidal cells other ori- 

 fices besides the infundibulum, which are smaller, and below 

 the latter. It is bounded, in front, by a sharp, thin ridge of the 

 ethmoid, the lower extremity of which contributes to close the 

 large opening into the sinus maxillare. 



