196 | Tue Microscope. 
cerned solely in the production of the dentinal matrix, while the 
deeper cells, as seen at “C,” send processes toward the dentine, 
whose canals they enter as the dentinal fibres. 
Fig. 6, represents a section ob- 
tained from a tooth of a young kit- 
ten. At “A” there is a layer of den- 
tine quite hard from the deposition 
of lime salts. At “ B” the matrix is 
much softer and but little calcareous 
matter is present. At “C” the layer 
of odontoblasts is well shown. Their 
processes extend into the newly- 
formed dentine, some reaching into the formed matrix. These pro- 
cesses remain in the dentine as it is forming, for the purpose, evi- 
dently, of making the dentinal tubes. At “D” are the cells of the 
deeper layer mentioned above. They are on the surface of the 
pulp as a distinct layer, although they do not differ from the num- 
erous, branched cells found all through the pulp. Processes from 
these cells will extend into the tubes formed from the processes of 
the odontoblasts, as just mentioned. 
Most of us are already sufficiently well posted in the histology 
of the teeth to know that nerves are always present. They form 
plexuses of non-medullated fibres on the surface of the pulp, and 
probably ascend into the dentinal canals with the processes re 
the deeper layer of celis. 
Although apparently so easy to Ende yet it is a fact that 
there are many questions concerning the structure of teeth very 
imperfectly understood. There is plenty of room and need for 
hard and faithful work in this line. 
STAINING HUMAN SPERMATOZOU. 
R. N. REYNOLDS. 
ISHING to clean, stain and mount some slides of this 
most interesting material, I first sought something which 
would cause the fluid to mix with water; out of a large number of 
drugs tried, a weak aqueous solution of bichromate of potash was 
found to be the only one which, without destroying the objects, 
cause the fresh spermatic fluid to mix with water; but when the 
