SECT. 138.] T T IE TEETH. 295' 



Molar Tooth of ail Adult Man. 



Phosphate of Lime, with some Fluoride of Calcium . 89-82 



Carbonate of Lime ....... 4*37 



Phosphate of Magnesia i'34 



Salts o-88 



Organic Substance 3"39 



Fa! 0-20 



IOO'OO 



Organic Substance 3'59 



Inorganic parts 9&'4- 1 



The enamel, as is even indicated by its fibrous cleavage, consists 

 throughout of the so-called enamel-fibres or enamel-prisms (fig. 123). 

 These are mostly pentagonal or hexagonal (al- Fig. 123. 



though not quite regular) solid, long prisms, , ms$& 



o - ooi 5'" to o , oo22 w in breadth, which, in general, r (H iJ^raa 

 extend through the entire thickness of the ( ^^/-Vi,T^k 

 enamel, and rest, with one extremity, upon the X^tYu^wxy^i 

 dentine, and with the other, upon the cuticle W^^X^mX^ 1 

 of the enamel. In the teeth of adults, these ®*^ 

 fibres cau be very readily seen in transverse Jaaf «ten«*M ^ 

 and longitudinal views, but can scarcely be iso- 3SS^m" I SSL' ,m 8( 

 lated for any great length ; it is otherwise in tbe calf ' 

 young teeth, or in such as are in the process of development, 

 where the enamel is much softer, and can be cut with a knife. 



Upon isolated prisms thus obtained, whose broken extremities may, 

 perchance, be pointed, whence also called enamel- Fig. 124. 



needles, the surfaces and borders can, in part, be very 

 distinctly recognised, and besides, especially after the 

 addition of somewhat diluted hydrochloric acid, more 

 or less distinct transverse striae, arising from slight 

 varicosities, and disposed in linear series at distances 

 of o'OOi4"' to 0002'", which give the fibres a certain 

 resemblance to muscular fibres, or rather to colossal 

 muscular fibrilhe, and, at any rate, are the expres- 

 sion of their growth through apposition, or are not 

 the expression of their composition of cellules. If the 

 hydrochloric acid be allowed to act more strongly, the 

 fibres soon become quite pale, the transverse stria- niients of en: , 



tiou disappears, and there remains nothing behind ™ er very siignVac- 

 but a delicate framework of the former solid fibres, acm;°magnified 350 

 which also, at length, breaks down. Thus, in teeth times - 0f " ,an - 

 which have been treated with hydrochloric acid, almost nothing 

 of the enamel remains behind ; and the latter docs not, like the 

 decalcified dentine, preserve its form. 



