282 MICROSCOPIC ANATOMY OF THE TEETH 



work on enamel, ' There is no support for any theory which 

 endeavours to explain the appearances found in formed or 

 forming enamel as being due to intermittent rhythmical 

 secretion from the cells ' (5) . 



Mr. F. J. Bennett, in a paper read before the Odonto- 

 logical Society in 1888, described the appearances produced 

 by the action of glycerine on dentine in which laminae were 

 brought into view, but the structure of the calcospherites 

 was not apparent in these preparations (1). 



From these observations it would appear that the stages 

 in the calcification of dentine are : 



Summary. First, the appearance of the small, clear, circular bodies 

 which form in a colloidal matrix by the coalescence of 

 minute particles, as seen in artificial experiments. 



Secondly, the coalescence of these clear bodies, which 

 becoming incorporated in the basis substance of the dentine 

 are still more completely fusod together, lose their structure- 

 less character, and exhibit concentric lines. 



Thirdly, the coalesced calcospherites undergo disintegra- 

 tion, their concentric elements being spread out into the 

 laminae of the dentine and the lime salts becoming equally 

 diffused in tho calcified matrix. 



Fig. 80 shows calcospherites formed in Harting's albumin 

 experiment referred to on p. 140. It is seen that the 

 concentric markings on the calcified artificially-produced 

 spherite are precisely similar to those in the calcoglobulin 

 substance of the decalcified dentine. It is noticeable that 

 while in the calcification of enamel we meet with spherites 

 having radial striae, these are not seen in dentine, where all 

 the component cpherites are seen to be of the concentrically- 

 arranged variety. 



As to the exact mode and channels of secretion of the 

 lime salts in dentine we have still but little accurate know- 

 ledge. We know that the deposit takes place, not in direct 

 contact with the odontoblasts but gradually advances from 

 above upon the odontogenic zone ; this would suggest 

 that the lime salts pass by dialysis from the tubes of the 

 dentine, containing the protoplasmic prolongation of the 

 secreting odontoblast cell, into the dentinal matrix, and the 

 minute subdivisions of the tubes with their protoplasmic 



