XXXVlll INTRODUCTION. 



The chief points that remain to be determined are the re- 

 lation of the dentinal pulp to the transitional cells between it 

 and the dentine ; the nature of the transition, and the relation 

 of the cells to the dentinal tubes and the intertubular tissue. 

 From the expression used by Purkinje and Raschkow in the 

 passage already quoted ;— " After a stratum of dental fibres 

 has been deposited between the parenchyme of the pulp and the 

 preformative membrane the same process is continued from the ex- 

 ternal to the internal region, the pulp supplying the material ;" — it 

 may be inferred that they considered the formation of the dentine 

 to be a process of deposition from the formative surface of the 

 pulp, like a secretion from a gland. If such were not the 

 idea of these authors of the relation of the formative pulp to the 

 dentine they nowhere clearly express the contrary opinion, and 

 the formation of the dentine by its deposition in successive strata 

 from the pulp continued to be taught in the best works on physiology 

 subsequently published. ( 1 ) 



(1) Miiller's Physiology, by Baly, part i, 2nd ed. p. 429. 



Mr. Bell who appears to have clearly recognized, long before the publication of the 

 Thesis of Raschkow, the ' preformative ' or external membrane of the pulp, supposed that it was 

 persistent, and that it was the true formative organ of the dentine. (See Anatomy, Physiology and 

 Diseases of the Teeth, 8vo. 1829). In his valuable edition of Hunter's Natural History of the 

 Human Teeth, in reference to Hunter's statement that the teeth are formed from the pulp, Mr. 

 Bell observes : " The statement that the bone of a tooth is produced from the pulp is erroneous. 

 This substance constitutes only the mould upon which the ossification is formed, between which 

 and the pulp is placed a membrane of extreme tenuity, which I have termed the proper mem- 

 brane of the pulp. It is slightly attached to the surface of the pulp, which it completely covers, 

 and it is from the outer surface of this membrane that the bone is secreted. As the pulp recedes 

 on the deposit of the successive laminae of bone, the ossific membrane continues to cover it, 

 and ultimately forms the well-known membrane lining the internal cavity of the perfect tooth." 

 — Bell's ' Hunter on the Teeth,' 8vo. 1835, p. 38. 



