INTRODUCTION. XXXIX 



Dr. Schwann was the first to express his leaning to the ancient 

 doctrine that ' the dentine is the ossified pulp.' But the nature of 

 the subjects selected by him for his observations left him in a state 

 of doubt and indecision on this point : and the author by whom 

 Dr. Schwann's observations were communicated to the British Asso- 

 ciation in August, 1839, although he adopted the doctrine of the 

 formation of ivory by the ossific transition of cells, rejected the idea 

 that the dental substance was the ossified pulp, and declared ' the cells 

 of the ivory to be altogether a distinct formation. '(1) 



In fact, the subjects chosen by both Dr. Schwann and his con- 

 tradictor, for the examination of the development of the dentine, were 

 inadequate to the exhibition of the relations of that substance to the 

 formative pulp during any part of the process of its formation. 

 The shape of the teeth of the mammalia selected by them for examina- 

 tion will not yield a view of the cap of new-formed ivory and the sub- 

 jacent pulp, in undisturbed connection, by transmitted light with the 

 requisite magnifying power ; and, if placed under the microscope as 

 an opake object, the light is reflected from the cap of ivory, and dis- 

 plays only the characters of its surface and not its relations to the 

 surface of the pulp in contact with it. To examine this surface micro- 

 scopically in either a human tooth or that of any of our domestic 

 quadrupeds the cap of dentine must be removed, and the exposed sur- 

 face of the pulp and the corresponding surface of the dentine be 

 examined as opake objects by reflected Hght. Or, if the layer of the 

 dentine be thin enough to allow the transmission of sufficient light, it 

 must be removed from the subjacent pulp before it can be so examined. 



(1) Report of the Papers read at the Medical Section of the British Association at Bir- 

 mingham, Literary Gazette, Sept. 21, 1839, p. 59S. 



