TEETH. CLASSIFICATION. 63 



rior and middle turbinated bones being processes of the ethmoid, and 

 the inferior a distinct bone of the face. The superior meatus occupies 

 the superior and posterior part of each fossa ; it is situated between the 

 superior and middle turbinated bones, and has opening into it three 

 foramina, viz, the opening of the posterior ethmoid cells, the opening 

 of the sphenoid cells, and the spheno-palatine foramen. The middle 

 meatus is the space between the middle and inferior turbinated bones ; 

 it also presents three foramina, the opening of the frontal sinuses, of 

 the anterior ethmoid cells, and of the antrum. The largest of the 

 three passages is the inferior meatus, which is the space between the 

 inferior turbinated bone and the floor of the fossa ; in it there are two 

 foramina, the termination of the nasal duct, and one opening of the 

 anterior palatine canal. The nasal fossae commence upon the face by 

 a large irregular opening, the anterior nares, and terminate posteriorly 

 in the two posterior nares. 



Man is provided with two successions of teeth ; the first are the 

 teeth of childhood, they are called temporary, deciduous, or milk teeth ; 

 the second continue until old age, and are named permanent. 



The permanent teeth are thirty-two in number, sixteen in each jaw ; 

 they are divisible into four classes, incisors, of which there are four 

 in each jaw, two central and two lateral ; canine, two above and two 

 below ; bicuspid, four above and four below ; and molars, six above 

 and six below. 



The temporary teeth are twenty in number ; eight incisors, four ca- 



galli process of the ethmoid. The groove between 1 and 3 is the lateral bound- 

 ary of the foramen csecum. 4. The cribriform plate of the ethmoid. 5. Part 

 of the sphenoidal cells. 6. The basilar portion of the sphenoid bone. Bones 

 2, 4, and 5, form the superior boundary of the nasal fossa. 7, /. The articula- 

 ting surface of the palatine process of the superior maxillary bone. The 

 groove between 7, 7, is the lateral half of the incisive canal, and the dark aper- 

 ture in the groove the inferior termination of the left naso-palatine canal. 

 8. The nasal spine. 9. The palatine process of the palate bone. a. The su- 

 perior turbinated bone, marked by grooves and apertures for filaments of the 

 olfactory nerve, b. The superior meatus. c, A probe passed into the posterior 

 ethmoidal cells, d. The opening of the sphenoidal cells into the superior 

 meatus. e. The spheno-palatine foramen. /. The middle turbinated bone. 

 g, g. The middle meatus. h. A probe passed into the infundibular canal, 

 leading from the frontal sinuses and anterior ethmoid cells; the triangular 

 aperture immediately above the letter is the opening of the maxillary sinus, 

 i. The inferior turbinated bone, k, k. The inferior meatus. /, I. A probe 

 passed up the nasal duct, shewing the direction of that canal. The anterior 

 letters g, k, are placed on the superior maxillary bone, the posterior on the 

 palate bone, TO. The internal pterygoid plate, n. Its hamular process. 

 o. The external pterygoid plate, p. The situation of the opening of the Eus- 

 tachian tube. q. The posterior palatine foramina, the letter is placed on the 

 hard palate, r. The roof of the left orbit, s. The optic foramen, t. The 

 groove for the last turn of the internal carotid artery converted into a foramen 

 by the development of an osseous communication between the anterior and 

 middle clinoid processes, v. The sella turcica. z. The posterior clinoid 

 process. 



