486 ORGANS OF DIGESTION. 



tooth, open on its alveolar surface. This opening is nearer the 

 internal circumference of the alveolar processes, so that the teeth 

 are almost covered, and probably for the reason advanced by 

 Mr. Hunter, that the gums may be firmly supported before the 

 teeth come through. 



The rudiments of the teeth which are earliest in their appear- 

 ance may be found in a fetus of two or two and a half months; 

 and at the expiration of three months, it is said that all the germs 

 of both sets of teeth exist in a manner to be distinguished.* The 

 germs of this period are lodged in. membranous folds belonging 

 to the gum, to which the germs of the first dentition are imme- 

 diately attached, while those of the second are suspended by 

 pedicles of a line or two in length, which circumstance alone 

 permits them to be distinguished. At four months all the germs 

 are contiguous to each other, with the exception of the incisors; 

 shortly afterwards they begin to be separated by the rudiments 

 of the alveolar processes ; and about the fifth month ossification 

 is perceptible in the infant incisors, and goes on in the other teeth 

 very much in the order of their appearance. 



The germs of the deciduous teeth are placed in an arc of a 

 circle, the cuspidati being thrown forwards out of the line of the 

 others and somewhat lower; in consequence of which, the first 

 molar border closely upon the incisors The germs of the per- 

 manent teeth are brought into view by removing the internal 

 face of the jaw, and are at the posterior upper side of the first 

 germs ; being, therefore, nearer to the edges of the alveolar pro- 

 cesses. 



At birth, ossification has taken place in all the infant teeth, 

 though their roots are not yet completed. The rudiments of the 

 permanent teeth, though seen at an early period of fcetal ex- 

 istence, do not be^in to ossify till after birth. Thus, the first 

 adult incisor and molar begin to ossify about the fifth or sixth 

 month of life, the second incisor and cuspidatus about the ninth 

 month, the first bicuspis about the fifth year, the second bicuspis 

 and second molar about the sixth or seventh, and the third mo- 

 lar about the twelfth year.t 



The teeth which have no predecessors are in consequence 

 of their adhesion to the gum brought out in their regular places; 

 * Serres, p. 3. t Hunter. 



