Tur Microscope. 195 
found in the interglobular spaces. The parallel lines seen at 2, 
Fig. 1, are due to the simultaneous curving of a series of adjacent 
fibres; they are known as the lines of Schreger. The lower part of 
Fig. 3, shows the dentinal fibres as they appear when mouuted in 
hard balsam. They are seen to give off numerous anastomosing 
branches on their way to the interglobular spaces, represented at 
2; while at 1, of the same figure, is shown the lacunie and con- 
aliculi of the cementum. 
Fig. 4, shows the dentinal 
sheaths lining the tubes, an effect 
that can be produced by macer- 
ating young dentine in a ten per 
cent.solution of hydrochloric acid. 
Dr. Britton, of Detroit, whose 
specimens of teeth have excited the admiration of every appreci- 
ative beholder, has prepared teeth by using a seventy-five per cent. 
solution of caustic potash, with the result of making one believe 
that the dentine has a true laminated structure. 
The cement, (Fig. 1, No. 3 and Fig. 3, No.1,) is true bone matrix 
with lacune and canaliculi in which are the bone corpuscles. 
Haversian canals are not unfrequently found. 
The pulp completely fills the central cavity, (Fig. 1, No. 4,) of 
the tooth. It is very vascular and contains numerous plexuses of 
nerve-fibres in a common matrix of connective tissue, in which is 
a net-work of branched cells. On the outer surface of the pulp, 
next the dentine, are two layers of cells. The 
outer layer is composed of oblong, columnar 
cells, known as the odontoblasts. These cells 
cling to the walls of the pulp cavity when 
the pulp is removed, giving the appearance 
of a distinct membrane, the membrana eboris. 
Between the deeper parts of the odonto- 
blasts, and forming a distinct layer beneath 
them, are peculiar, branched, spindle-shaped, 
nucleated celis. 
Fig. 5, illustrates these two varieties of 
Fig. 5. cells, At “A” are the dentinal fibres; at 
“B” are the odontoblasts; while at ‘‘C” are the branched cells of 
the deeper layer. Itis probable that the odontoblasts are con- 
