XXXIV INTRODUCTION. 



layer of the dentine, immediately beneath the enamel, which was 

 more decomposed by the acid, could only be resolved into finer 

 fibres of a different nature, crossing each other in the most various 

 directions, and which I presume to be the remains of the dentinal tubes. 

 " The dentine thus consists of interblended fibres between which 

 run canals with proper parietes. Both the fibres and tubes in human 

 teeth are nearly perpendicular to the pulp-cavity. What relation, then, 

 do the fibres and the tubes bear to cells ? I might incline to the old 

 notion that the dentine is the ossified pulp. According to Purkinje and 

 Raschkow the pulp consists at first of granules nearly similar in size 

 and form without vessels and nerves ; then vessels and lastly nerves 

 penetrate it. At the superficies of the pulp the granules are more 

 regularly arranged and more elongated, and are directed outwards 

 either vertically or at a shghtly acute angle. These longitudinally 

 drawn out globules are plainly cylindrical cells. In recent teeth they 

 very distinctly contain the characteristic nucleus and its nucleolar cor- 

 puscles and closely resemble the prisms of the enamel-membrane 

 (Tab. iii, fig. 4). The interior substance of the pulp consists of 

 round nucleated cells, between which run the vessels and nerves. 

 If the pulp be drawn out of the cavity of a young tooth, and the 

 dentine be observed either recent or after the earth has been removed 

 by acid, there remains on its inner surface, at least where it is yet 

 thin and soft, a layer of the cylindrical cells that constitute the pulp : 

 these are about as thick as the solid fibres of the dentine, and have 

 the same course, and as they cohere more firmly with the dental substance 

 than with the pulp and remain attached to the former, so I presume that 

 here a transition takes place, and that the cylindrical cells of the pulp 



(1) " Ich mochte mich zu der alteren Ansicht hinneigen, das die Zahnsubstanz die ver- 

 knocherte Pulpa ist," loc. cit. p. 124. Compare the Literary Gazette, September 21st, 1839, 

 p. 598, and Medical Gazette, January 3d, 1840, p p. 540, 541. 



