ON THE DEVELOPMENT OP TEETH. 43 



the oral epitheliums, but bud out from the necks of the 

 enamel organs of the corresponding temporary tooth-sacs 

 (see fig. 1). Thus the only connection which the permanent 

 tooth-germ as with that of the temporary tooth is through 

 the medium of its enamel germ ; its dentine papilla and sac 

 originate perfectly independently, at a spot which a2)pears 

 to be determined by the position attained to by the enamel 

 germ. 



In this manner the enamel organ of each successional tooth- 

 sac is derived from a part of that of its deciduous prede- 

 cessor; while those teeth which have no such predecessors — 

 i. e. the true molars — originate in the follo-wang manner : — 

 The enamel organ of the first true molar is derived from the 

 back end of that same epithelial inflection whence sprang all 

 the temporary tooth-germs ; in its origin it, therefore, ranks 

 to some extent with the deciduous teeth, being, like them, 

 derived from a primary ingrowth of epithelium. 



The enamel organ for the second permanent molar buds out 

 from the neck of that of the first ; that for the third or 

 wisdom tooth from the neck of that of the second (Legros 

 and Magitot). 



The development of mammalian teeth had thus been fairly 

 well worked out, and the subject was placed on a satisfac- 

 tory basis of observation, but little had been done towards 

 the elucidation of the process as exemplified in reptiles and 

 fish. 



Professor Huxley, as early as 185S (^Micros. Journal'), 

 had arrived at some conclusions very far in advance of the 

 knowledge of the time, and uttered a protest against the 

 universality of the papilla theory ; Dr. Lionel Beale (' Ar- 

 chives of Dentistry,' 1863) had arrived at a similar conclusion 

 with regard to the teeth of the newt, and, although I cannot 

 Avholly agree with his views, had described several points 

 of great importance with entire accuracy. With the excep- 

 tion of these, and a more recent paper by Santi Sirena, the 

 writings of Professor Owen practically held sole possession 

 of the field. 



The following may, I think, be taken as a fair summary 

 of Prof. Owen's views (his own words I have quoted in my 

 papers before referred to). 



The whole process of development of the teeth in 

 certain fish might be taken to represent an early stage only 

 of the development of mammalian teeth ; thus the teeth of 

 sharks are said to be developed from germs which never 

 become encapsulated: in fact, never pass beyond the papillary 

 stage. 



