122 A MANUAL OF DENTAL ANATOMY. 



Opposite to the apex of the dentine papilla, where the 

 enamel cap is to be, the cells of the enamel organ attain to 

 a very considerable size, measuring about T ^ of an inch in 

 length ; below this the investing cap of enamel organ does 

 not cease, but it is continued in a sort of rudimentary con- 

 dition. Thus, although the enamel organ invests the whole 

 length of the dentine papilla, its cells only attain to any 

 considerable size opposite to the point where the enamel is 

 to be formed. The knowledge of this fact often enables an 

 observer to say, from an inspection of the tooth germ, 

 whether it is probable that the perfected tooth will be coated 

 with enamel or not. In any case an enamel organ will be 

 there, but if no enamel is to be formed, the individual cells 

 do not attain to any considerable degree of differentiation 

 from the epithelium elsewhere ; in other words, the whole 

 enamel organ will partake of the character of the lower 

 portion of that represented in the figure of the tooth germ 

 of the eel. 



Although of course there are many differences of detail 

 arising from the very various situations in w r hich teeth are 

 developed in fish, so great uniformity pervades all which 

 I have examined, that we may at once pass on to the con- 

 sideration of the development of the teeth of reptiles, merely 

 adding that it is not altogether true to say that the teeth of 

 fish in their development exemplify transitory stages in the 

 development of mammalian teeth. 



In Reptiles. So far as the appearances presented by 

 the individual germs go, there are few differences worthy 

 of note to be found in the present class by which they are 

 distinguishable from those of either fish or mammals. The 

 enamel organ is derived from the oral epithelium, the den- 

 tine organ from the submucous tissue in a manner very 

 similar ; nevertheless, there are points in the relation which 

 the successional tooth germs bear to one another, arid to the 

 teeth already in situ, which are of some little interest. The 



