212 IVAN E. WALLIN 
methods have been used not only in comparing the mitochondria 
of plants and animals, but also in determining the approximate 
chemical nature of mitochondria, it is necessary in this compara- 
tive study of bacteria and mitochondria to also determine the 
reaction of bacteria to these chemicals. It must also be admitted 
that there is no basis for supposing that all strains of bacteria 
should respond in the same way to a given chemical. It has 
been indicated by Cowdry and others that all mitochondria 
do not respond to a given chemical in the same way. 
The methods employed in this study of the reactions of bacteria 
to chemicals were designed to retain as much as possible of the 
materials resulting from the chemical action. Metal rings coated 
with paraffin were sealed to microscopic slides, smears of the 
bacteria were then made inside of the rings, and after the chemi- 
cals were added cover-glasses were sealed over the rings to 
prevent evaporation. After a given time the cover-glasses were 
removed and the chemical was permitted to evaporate. When 
the smears had thoroughly dried and the paraffin around the 
smears had been removed with xylol, a thin film of celloidin was 
painted over the smear. The smears were then stained, using 
the carbol-fuchsin method for tubercle bacilli preparations and 
Pappenheim’s pyronin-methyl green and Loeffler’s methylene 
blue for the other preparations. With careful handling in the 
staining and washing, the celloidin membrane remains intact 
on the slide. Control preparations were made in connection with 
every chemical preparation. 
For determining the action of ether, chloroform, and heat on 
bacteria it is obvious that the paraffin rings could not be used. 
In these experiments large quantities of bacteria were placed in 
vials and the ether and chloroform added. After four hours 
the ether and chloroform were permitted to evaporate considera- 
bly. The remains in the vials were then withdrawn with a 
pipette, placed on slides and permitted to evaporate to dryness. 
For the heat determinations the organisms were placed in vials 
with normal salt solution. The vials were then kept at a constant 
temperature in an incubator. After half an hour portions of 
the emulsion were withdrawn with a pipette and permitted to 
evaporate on slides. 
