266 MICROSCOPIC ANATOMY OF THE TEETH 



times isolated. He describes these fibrillse as being very 

 fine, scarcely more than 5 \j, thick, and as showing the same 

 characteristics as the glue-giving connective -tissue fibres, 

 but they are not arranged in lamellae as in bone. The fibres 

 cross each other and mostly in planes perpendicular to the 

 dentinal tubules. Von Ebner considered that these fibres 

 were due to a change in the upper and peripheral portion 

 of the odontoblast cell, and according to Rose's explanation 

 of this view, in some cases ' the peripheral ends of the 

 odontoblasts are first of all changed into a homogeneous 

 layer of non-granular protoplasm in which the fibrils 

 become visible only later'. 1 This author also says 'the 

 dentinal fibrils are those remains of the cell bodies which 

 are left when the odontoblasts are changed into gelatine- 

 yielding fibrils, and which retain their protoplasmic struc- 

 ture '. According to this view there would be a gradual 

 using up of the peripheral portion of the odontoblast cell 

 as calcification advances, the layer of uncalcified dentine 

 in the odontogenic zone being formed ' by the change of 

 the peripheral portion of the odontoblasts into gelatine- 

 yielding fibrils. The dentine calcifies by the deposition of 

 salts of lime between the fibrils.' In fig. 167 delicate fibres 

 are seen crossing the odontoblasts and entering the odonto- 

 genic zone which certainly appear to be fine fibres from 

 the pulp, and in fig. 168, from the tooth of a calf treated with 

 chromic acid, fibres can be seen crossing the odontoblasts 

 and entering the odontogenic zone. 



The author has but lately found further corroboration of 

 his view that connective-tissue fibres prolonged from the 

 tissue of the pulp enter the dentine and form its fibrillar 

 basis as explained on p. 268. 



It appears possible that a portion of this fibrillar founda- 

 tion substance, forming the odontogenic zone, may be laid 

 down by the odontoblasts as Von Ebner describes ; but many 



1 Rose, in his paper above referred to, says : ' As Partsch correctly 

 remarks., Mummery has examined pathologically changed human teeth 

 or unfavourably preserved preparations.' This assumption of Professor 

 Partsch endorsed by Rose is made without any evidence, he never 

 having seen the preparations or made any inquiry concerning them. 

 Such a method of criticism needs no further comment. 



