314 A MANUAL OF DENTAL ANATOMY. 



still be found to be divided into periods, under the names 

 of " papillary," " follicular," and " eruptive " stages. 



These stages are based upon a false conception, upon 

 theories now known to be incorrect, and may advantageously 

 be absolutely abandoned. The account of the development 

 of the teeth given in the following pages (based in the 

 case of man and mammals upon the researches of Kolliker, 

 Thiersch, and Waldeyer ; in the case of reptiles and fishes, 

 upon those of Huxley and Santi Sirena, and upon Hertwig's 

 and my own), will be found to conflict with the accounts, 

 published by a deservedly great authority, Professor Owen. 

 I cannot reconcile these discrepancies, except upon the as- 

 sumption that modern methods of research have disclosed 

 facts heretofore not demonstrable ; yet twenty years ago 

 Professor Huxley demonstrated in a remarkable paper the 

 incorrectness of certain of the theories then promulgated. 

 Of the general accuracy of the following description I am 

 however fully satisfied, and most of the facts may be easily 

 verified by any one desirous of so doing. 



True tooth germs are never formed quite upon the surface (% 

 but are always situated at a little distance beneath it, lying in 

 some creatures at a considerable depth. Every known tooth 

 germ consists in the first instance of two portions, and two- 

 only, the enamel germ and the dentine germ ; and these are 

 derived from distinct sources, the former being a special 

 development from the epithelium of the mouth, the latter 

 from the more deeply lying parts of the mucous membrane. 

 Other things, such as a tooth capsule, may be subsequently 

 and secondarily formed, but in the first instance, every 

 tooth germ consists of an enamel germ and a dentine germ- 

 only, and the simplest tooth germs never develop any addi- 

 tional parts. The existence of an enamel organ in an early 

 stage is therefore perfectly independent of any subsequent 



0) The placoid scales of embryonic sharks are, however, formed on the 

 surface, and the "germs " covered in by epithelium only (Hertwig). 



