190 BONES OF THE CRANIUM. 



The superior surface is the cribriform plate. It is of an 

 oblong shape, and perforated with many foramina for the 

 passage of the first pair or olfactory nerves. Along the 

 central part of this surface there is an eminence, the crista 

 galli, to which the falx major is attached. On either side 

 of this crest is a deep furrow for lodging the bulbs of the 

 olfactory nerves; and at the anterior part of this furrow, 

 close to the crest, is a narrow slit which gives passage to 

 the nasal branch of the ophthalmic nerve. The crista 

 galli, at its anterior portion, projects into two little pro- 

 cesses or alee which connect it with the frontal bone. 



From the under surface of the cribriform plate, along the 

 middle line, descends the nasal lamella or vertical septum. 

 This is a broad plate of bone, thick before where it joins the 

 nasal bones and the nasal process of the frontal bone, thick 

 behind and above where it unites with the sphenoid, and 

 thin below where it joins the vomer and nasal cartilage. 

 Upon the sides of this nasal septum are seen canals ending 

 in grooves, some oblique and others vertical, for transmit- 

 ting the olfactory nerves. Upon each side of this septum 

 is the roof of the nostril; and upon either side are also ob- 

 served two irregular bones, the superior and middle turbi- 

 nated or spongy. Next to these is a range of cells; and 

 upon the outside of this again an external surface, smooth 

 and plane, the os-planum, and forming the internal 

 plate of the orbit of the eye. The superior and middle 

 turbinated bones are very thin and spongy scrolls or curved 

 laminge of bone, the one above the other the upper con- 

 taining the superior meatus, the lower having the middle 

 meatus, and being the more curved and the larger of the 

 two. 



The ethmoid cells lie between the turbinated bones and 

 the os-planum and uriguis, or between the nasal and orbi- 

 tal surfaces, being bounded above by the cribriform plate. 

 They are twelve or fourteen in number, and are divided, by 

 a bony partition, into an anterior and posterior set. The 

 posterior communicate with the superior meatus, and are 

 small, and one of the upper sometimes opens into the sphe- 



