layer of the dentine, immediately beneath the enamel, which was
more decomposed hy the acid, could only he resolved ihto 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 interhlended 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 slightly acute angle. These longitudinally
drawn out globules are plainly cylindrical cells. In recent teeth they
very distinctly contain the characteristic nucleus and its nucleolar corpuscles
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 he drawn out of the cavity of a young tooth, and the
dentine he 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 möchte mich zu der älteren Ansicht hinneigen, _das die Zahnsuhstanz die verknöcherte
Pulpa ist,” loc. cit. p. 124. Compare the Library Gazette, September 21st, 1839,
p. 598, and Medical Gazette, January 3d, 1840, p p. 540, 541.
are only the earlier stage of the dentinal fibres, since these cells
are filled with organized substance become solid and osseous. Sometimes
these cylindricules are not found on the dentine, hut then we
see in their place a number of cel]-nuclei; these are very pale and
ultimately united with the dentine so that they may he easily overlooked.
When once attentively observed, they are not easily mistaken,
and are separated by extremely minute intervals. Against
the opinion that the dentine is the ossified part of the pulp, the
facility with which the one is separated from the other has been
objected, and I allow the force of that objection. But it is at least
weakened by the fact that a part of the pulp remains attached to
the dentine, and that in half-ossified ribs, the cartilage can he easily
detached from the ossified portion, and that in teeth the separation
must he so much the easier as. the difference is greater between the
dentine and the pulp.
There are at least sufficient grounds for going more closely
into the detail of this view. The pulp agrees with all the
other tissues of the foetus, and more especially with cartilage,
inasmuch as it consists of cells; it differs in consistence from mammalian
cartilage, inasmuch as whilst the quantity of cytohlasts
(nucleated cells), on which the hardness of mammalian cartilage
depends, is very small, the cylindrical cells, at least on the surface
of the pulp, are closely aggregated together. In this respect the pulp
more nearly resembles certain cartilages in the lower animals, in which
the cytohlasts are present in smaller quantity and the consistence
of the cartilage depends upon the thickening of the walls of the cells.
Whether, in the presumed transition of the cells of the pulp
into the dentinal fibres, the obliteration of the cavity is effected
by the thickening of the walls of the cells, I know not, since
c 2