ON ABSORPTION. 25 



This is beautifully shown in the Lacertine reptiles, 

 where the succession of teeth is constant with the 

 animals' existence (Fig. 5). 



The new organ is developed on the lingual sur- 

 face of the fang of the old, which is gradually 

 absorbed in a direct proportion to the development 

 of the new tooth. 



That which is so distinctly manifest in the rep- 

 tile, is but the simplification of the process as ex- 

 hibited in the higher types of animals. 



In man, the new teeth are developed within the 

 arc occupied by the deciduous set. Absorption, 

 as a general rule, commences upon the inner sur- 

 face of the extremity of the fangs of the single 

 fanged teeth, and in every case corresponds to the 

 position of the new organ in relation to the old. 



The teeth which are in the progress of develop- 

 ment are formed in alveoli, distinct from those 

 in which the deciduous are implanted. But this 

 only continues for a time. The bony cases in which 

 the former exist are gradually removed by absorp- 

 tion, and then those parts of the fangs of the deci- 

 duous teeth which are first exposed follow in exact 

 proportion with the surrounding osseous tissue. 



This is the case in those animals where the teeth 

 are developed in close approximation with the 

 deciduous set. But when there is a great separation 

 between individual teeth, as in those planted in 

 the intermaxillary bones of the common pig {Sus 

 scro/a), one of the few recent mammals that possess 



