CHANGES PRODUCED ON THE FACE. 257 



The infra orbital foramen of the upper jaw presents sim- 

 ilar changes. It is found, at birth, to correspond with the 

 point between the canine and first molar; after this, to 

 become more posterior on the completion of first dentition; 

 and when the first permanent molaris appears, to occupy 

 the usual adult point, namely, on a line between the two 

 bicuspids. 



T he pterygoid process es of the sphenoid are also affected, 

 and undergo changes during the development of the teeth. 

 M. Blandin says these processes are to the superior dental 

 arch, what "the posterior border and angle are to the 

 inferior." Both are alike points of support to the alveolar 

 arches; and both also undergo similar changes in the 

 development of the teeth. At birth these processes, like 

 the posterior of the lower jaw, look very obliquely, for- 

 wards and downwards. In the adult they take the verti- 

 cal position; and in old age they again return to their 

 primitive oblique condition. 



The maxillary tuberosity also undergoes important 

 changes during the development of the teeth. Before the 

 time of their eruption, this tuberosity is large, from lodg- 

 ing the greater molars ; but after their appearance, it in a 

 great measure disappears, and still can be seen to exist, 

 notwithstanding M. Blandin's opinion to the contrary. 



The roots of the superior middle molars of the upper 

 jaw exert a decided influence upon the floor of the max- 

 illary sinus. In the rudimentary state their action is not 

 very great. But in the adult period, when the sinus is 

 large and the roots fully developed, we sometimes find 

 these roots entering this sinus, a fact of great practical 

 importance in the treatment of its diseases ; while, in old 

 age, we are told the sinus, "by a new development, has its 

 floor carried back from the roots of the teeth," whose action 

 upon the sinus is already diminished by the contraction of 

 the alveoli. 



Now all these changes upon the upper and lower jaw, 

 during the development of the teeth, it will be readily 

 perceived, must exert a most powerful influence on the 

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