PURKINJE AND MULLER ON THE TEETH. 103 



bringing ink into contact with them, it was drawn into them, 

 as if by capillary attraction. These tubes Miiller believed to 

 be filled, at least partially, with calcareous matter, which was 

 the cause of the whiteness and opacity of the toofh. In 

 the more transparent part of carious teeth, the white sub- 

 stance in these tubes presented more of a granular, and less of 

 a compact appearance, under the microscope, than in a sound 

 tooth. 



The white color and opacity of these tubes were removed 

 by the application of acids. On breaking a thin lamella of a 

 tooth transversely in regard to the fibres, and examining the 

 edge of the fracture, he perceived the tubes, stiff, straight, and 

 inflexible, projecting here and there from the surfaces. If the 

 lamella had previously been acted on by acid, the tubes were 

 flexible, transparent, and often very long. Hence Miiller 

 inferred that the walls of the tubes have a basis of animal tissue, 

 and that besides containing calcareous matter in their cavity, 

 they have this tissue in the natural state impregnated with 

 calcareous salts. The greater part of the earthy matter of the 

 tooth is, however, contained in the transparent homogeneous 

 portion between the fibres, in which it can be rendered visible 

 in a granular state by boiling thin lamina of teeth in a ley of 

 potash. 



Purkinje, by the aid of high magnifying powers, discovered 

 the corpuscles that characterize true bone, in layers taken from 

 the external and internal surface of the root ; he considers the 

 great mass of the tooth, however, as destitute of organization. 

 These fibres which have been still more fully proved by 

 Retzius* to be true canals, having their own walls, are differ- 

 ently arranged in the separate substances of the tooth, but are 

 every where exceedingly minute. In the ivory they are about 

 g^th of a line in diameter: they commence by open orifices 

 at the cavity of the pulp, and extend in an undulating but 

 nearly parallel direction to the surface, dividing and branching 



* Mikroskopiska Undersokningar ofver Tandernes sardeles Tandbenets, 

 struktur : Stockholm, 1837. 



