246 TEMPORARY AND PERMANENT TEETH. 



the permanent, though we are not informed what pushes 

 forward these last. 



Others again attribute it to the prolongation of the 

 pulp, &c., while Delabarre and Harris think a much more 

 philosophical explanation is to be found in the sac of the 

 tooth itself, which, they think, possesses the power of con- 

 traction ; and as the uterus expels the child, so it extrudes 

 the tooth. This is a very ingenious and satisfactory theory, 

 provided this contractile power and its efficiency can be 

 established. 



An equally great diversity of opinion is entertained in 

 reference to the shedding of the teeth. 



Absorption of the partitions between the two sets of 

 teeth, and subsequently of the roots of the temporary, from 

 the pressure of the advancing permanent teeth, is regarded 

 by Mr. Fox as the prime agent. Others think the process 

 entirely mechanical, a sort of abrasion by the rising tooth. 

 Others again believe that the vessels cease to carry fluids, and 

 that the teeth consequently die, and drop out for the want 

 of the necessary nutrition ; while others give the operation 

 a chemical solution : among the latter are Delabarre and 

 Harris. A "fungiform or carneous substance" is spoken of 

 as existing behind the roots of the temporary teeth, called 

 "absorbing apparel," whose office it is to exhale a chemical 

 fluid which has the power of dissolving the roots, and thus 

 removing them.* 



DIFFERENCE BETWEEN THE TEMPORARY AND PERMANENT TEETH. 



We will quote the language of Mr. Bell on this head. 

 " The temporary teeth are, generally speaking, much 

 smaller than the permanent of a less firm and solid tex- 

 ture, and their characteristic forms and prominences much 

 less strongly marked. The incisors and cuspidati of the 

 lower jaw are of the same general form as in the adult, 

 though much smaller ; the edges are more rounded, and 

 they are not much more than half the length of the latter. 



* For further information on this point, see flarris's Principles and Practice 

 of Dental Surgery. 



