INTRODUCTION. Vll 



laminated, and the ivory was described as being formed layer within 

 layer, deposited by, and moulded upon the formative superficies of 

 the vascular pulp. The illustrations and supposed proofs of this 

 structure and mode of growth were derived from the apparently 

 detached condition of the newly-formed particles of dentine on the 

 pulp's surface when exposed by the removal of the calcified part 

 of the tooth ; from the appearances observed in the teeth of animals 

 fed alternately with madder and ordinary food, which undoubtedly 

 illustrate the true progress of dental development ; from the illusory 

 traces of laminated structure observed in vertical sections of teeth 

 when viewed by the naked eye, or with a low magnifying power ; and 

 lastly, and chiefly, from the successive hollow cones into which 

 a tooth is commonly resolved in the process of decomposition. 



With regard, however, to the appearances presented by the teeth 

 of animals under the influence of madder, and to the separation of the 

 dentine into superimposed lamellae during decomposition, the same 

 conclusions as to intimate structure and mode of development might 

 be drawn respecting true bone, which also commonly resolves itself 

 into concentric lamellae during decomposition, and presents the 

 same appearance of alternate white and red layers in animals fed 

 alternately with madder and ordinary food during the progress of its 

 growth. 



The Unes running parallel to each other and to the contour of 

 the crown presented by the cut surfaces of vertical sections of teeth, 

 especially of the elephant's tusk, or of the tooth of the cachalot, are 

 due to a totally different structure from that to which they have been 

 ascribed. The lamellated arrangement, thus seemingly demonstrated, 

 is, moreover, far from being a constant appearance ; on the contrary, 

 the superficies of vertically cut or fractured surfaces of the human 



