138 Tue Microscope. 
cause the disease. To determine this question, Dr. Vignal 
(Deutsche Mediz. Zeitung, 1884, No. 1) has collected sputa, as 
they had been expectorated by phthisical persons in the streets. 
He mixed them with the common street dirt, moistened them, 
put them on a porcelain plate, suffered them to dry, again 
moistened them, again let them dry, and continued these exper- 
iments for a very long period of time. Then he made inocula- 
tion from these sputa in two Guinea pigs; one died a few days 
later from a different, accidental complaint, the other first be- 
came fat—a proof of the experimenter’s good feeding—then 
slowly emaciated, and finally, three months later, died. The 
post mortem showed a large number of tubercles, many in the 
state of caseous degeneration, and a great number of bacilli. 
This experiment proves that the sputa collecting in the 
streets and on the floors of dwellings, are by no means innocu- 
ous, but serve as pathogenic elements in persons predisposed to 
this disease. 
PREPARING AND Mountine SEcTIONS OF TEETH AND BonE.—J. 
E. Ady explains as follows what he terms the ‘ laccic ”’ method 
of occlusion. 
1st. Saw a piece off the tooth or bone, rub it flat on an 
engineer’s file, polish the flat surface on a fine hone, Water-of- 
Ayr stone being preferable. 
2d. Fasten the section to a piece of plate glass, one inch 
square, with a cement made by melting six parts of “ button ” 
lac with one part Venice turpentine. 
3d. File the section down moderately thin, and then reduce 
further on the Water-of-Ayr stone, examining from time to time 
with the microscope. 
4th. Soak the section off with strong methylated spirit, 
wash thoroughly in clean spirit, and dry between tissue paper. 
5th. Make a thin solution of white shellac in methylated 
spirit, filter, and keep in a stoppered bottle. 
The section is to be dipped in this solution, drained, and 
laid on a cold plate under a bell-glass. In about half an 
hour it will be dry. 
6th. Mount in cold balsam and benzo] in preference, in 
