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together some rather divergent forms, and moreover is, to me at all 

 events, not readily intelligible in all its aspects. 



This is defined as being a hard tissue rich in short dentinal 

 canals but not growing immediately beneath and in dependence upon 

 an epithelial sheath, and as capable of increase in all directions. 



The example given is Myliobates and the semidiagrammatic figures 

 show bands of calcification shooting down through the pulp ; this is 

 embraced over all by an epithelial sheath, which does not dip in 

 towards the areas of calcification but remains smooth and simple. 

 Tlie completed tooth of Myliobates, as is well known, consists of a 

 number of round parallel pulp canals which run vertically upwards 

 but do not reach the surface; from each of these pulp canals dentinal 

 tubes radiate on all sides, thus constituting a number of parallel 

 systems. 



The boundaries of the several systems as seen in cross section 

 are more or less hexagonal; the form which is assumed by a number 

 of plastic bodies originally round which are influenced by mutual press- 

 ure, as can be seen by looking at the impressions made by shot upon 

 a wad or upon the interior of a cartridge which has been fired, 

 where the cardboard has been squeezed up between the shots. 



Now let us attempt to imagine what would happen if the trabeculre 

 which Dr. Rose figures as the commencements of calcification in the 

 dentinal papilla of Myliobates, and which correspond to the outermost 

 portions of each system, did increase on all sides (allseitig). 



They would go on thickening till they began to nearly meet, and 

 then their forms would be modified by mutual influence and more or 

 less regular hexagonal meeting lines would result, but these hexagonal 

 boundaries would intersect the position in which the axial pulp canals 

 really are, and the residual areas of soft pulp would, under such a 

 supposition, lie not in the centres but in the boundary lines of the 

 several areas of calcification. 



It seems impossible to conceive any way by which the ultimate 

 structure of the tooth could be arrived at unless the commencing areas 

 of calcification had the regular arrangement of the partitions of a 

 honeycomb, in Avhich case the term trabecul.T. does not commend itself 

 as appropriate, neither can its onward march be described as "all- 

 seitig" but rather as "einseitig". 



Moreover it seems hard to conceive this regular honeycomb form 

 of the earliest calcification without a prior disposition of soft parts: 

 without in fact there being practically a parallel series of pulps in 

 each of which calcification proceeded after the manner of a true dentine 

 calcification. 



