CLEANING GLASSWARE 3 
yaper. Sometimes there appears to be a film on the surface 
of the cover glasses which interferes in making hanging-drop 
sreparations. Sometimes this can be overcome, after they are 
wiped out of the alcohol, by placing them in a Petri dish with- 
sut the cover and heating them in the dry-air sterilizer at a 
temperature of 160° to 180° C. for one hour. After they have 
2ooled, replace the cover and allow the cover glasses to remain 
in the Petri dish (a glass jar or other closed dish may be used) 
antil used. (When a drop of water or bouillon is spread upon 
a properly cleansed cover glass it does not roll up in droplets. 
but will remain in a thin, even layer on the surface.) 
Slides can be cleaned very satisfactorily by washing them 
in hot soapsuds, rinsing them in hot water, and wiping them 
with a soft cloth. 
(/) Cleaning used culture apparatus. Place i tubes, flasks, 
or Petri dishes containing old cultures in a w@er bath, cover 
them with water, add a little sal soda (about an ounce to a 
gallon of water), and boil for 20 minutes. Pour off the water 
and empty the tubes, after which again boil them for 5 minutes 
in clean soap and water. Then wash and treat with the clean- 
ing mixture the same as the new tubes. Cultures of spore- 
bearing pathogenic bacteria, such as those of anthrax, should 
be destroyed by heating in the autoclave at a temperature of 
at least 110°C. for half an hour before the tubes are emptied 
and washed. 
4. A method for cleaning cover glasses for flagella stain. 
For this work the ordinary method of cleaning cover glasses is 
not sufficient, although the heating will often give a perfectly 
satisfactory cover glass. The following treatment was first 
highly recommended to me by Dr. Erwin F. Smith, and later 
nodified by Johnston and Mack. First clean the cover glasses 
oy the ordinary method, after which boil them in an agate cup 
or glass beaker in a 5 % solution of caustic soda for 19 minutes. 
After cooling, rinse thoroughly in distilled water, place in a 
oeaker, and cover with a 10% solution of hydrochloric acid 
