ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
529 
ration of microscopical sections of tooth and bone, in which he gives an 
account of some new and important discoveries in the structure of these 
tissues, for it was from this Journal,* he tells us, that he obtained an 
account of Dr. L. A Weil’s method of carrying out the balsam process. 
“ I prepared,” says Mr. Mummery, “ some sections according to these 
directions, and was so pleased with the results that I have since cut 
nearly two hundred specimens in this way.” It should not be forgotten 
that this portion of the Journal is of great assistance to those who, like 
Mr. Mummery, have little time for searching the literature of micro- 
scopical technique. 
Preparing Sections of Teeth. f — Mr. W. A. Hopewell - Smith 
remarks : — 
“ (1) The most satisfactory method, in my opinion, of preparing 
sections showing odontoblasts in situ is as follows : — The jaw, preferably 
the lower, of an embryonic mammal, such as kitten or pup, taken while 
still in a fresh condition, is carefully stripped of all the tissues covering 
it, except the oral epithelium and flange of gum, and is placed in the 
usual standardized solution of Muller’s fluid, in order to harden its soft 
structures, the volume of fluid being about twenty or thirty times the 
bulk of the immersed tissue. The fluid must be changed every day for 
four or five days, and then every third or fourth day. The hardening 
process is to be completed by removing the specimen — which has 
remained in the Muller’s for a fortnight — to alcohol or rectified spirit ; 
and this is to be renewed occasionally until all the colouring matter has 
disappeared from the specimen and fluid. Vertical sections are then 
cut by means of a thin sharp knife, and these placed longitudinally on 
the stage of a Cathcart or Williams freezing microtome, and cut in the 
ordinary way. Best results are obtained from sections in the canine and 
bicuspid regions, as here the parts are less likely to be disturbed in the 
manipulations with the microtome. Imbedding in paraffin and wax, or 
celluloilin, is of little service. The advantages claimed for this method 
are: — (a) The simplicity of its performance. It will be seen that the 
hard tissues are not softened by any decalcifying agent, which would 
materially affect the delicate soft tissues. The knife cuts quite easily 
the thin cap of semi-calcified dentine and bone, and the elements of the 
pulp are in no way disturbed in their relation to each other. ( b ) The 
odontoblasts are of large size, and easily observable at this period, as 
their formation of dentinal fibrils is at its highest stage of development. 
They can be isolated, if thought necessary, by separating with the point 
of a needle from the surface of the dentine papilla the cap of dentine to 
which in places they adhere, (c) This method affects little, if at all, 
the relative positions of dentine, odontoblasts and pulp ; and I have 
found it to be extremely successful. 
(2) I should advise your correspondent not to grind down sections 
of teeth of fishes in situ ; but to decalcify the jaw and teeth with a 5 per 
cent, solution of chromic acid or 10 per cent, solution of HC1. After 
sections have been cut and stained they should be washed well in 
distilled water, dehydrated for three minutes in absolute alcohol, 
“ cleared ” in oil of cloves or xanthol, and mounted in Canada balsam. 
* 1888, p. 1042. 
t Journ. Brit. Dental. Assoc., xi. (1890) pp. 310-2. 
