THE PREPARATION OF BOUILLON ; 9 
three quarters of an hour and filtered hot. The filtrate 
iould be perfectly clear. The color will vary according to the 
nount of blood pigment in the meat used, and according to 
ie length of time it is steamed or boiled, i.e. according to the 
nount of material precipitated out. After filtering, distribute 
.e bouillon in tubes and flasks (see above), and stand them in 
wire basket for sterilization. Sterilize them by boiling in a 
osed water bath or steaming in the Arnold’s steam sterilizer for 
> minutes,! the time to be computed from the time the water 
rils or the temperature in the steamer reaches g9°. The 
asks of bouillon should be boiled or steamed for 20 minutes 
1 each of the two succeeding days (certain anaérobic bac- 
ria may not be destroyed by this treatment). When they 
ave cooled the outside of the tubes should be carefully wiped 
ith a moist cloth and placed in the incubator until the next 
boratory day. Then carefully examine them, and if any of 
\e tubes are contaminated, that is, if the liquid is clouded or 
is a membrane on the surface, they must be rejected. Label 
\e others and place them in the locker. 
1 The customary method of sterilizing culture media is to steam or 
xi] them for about 10 minutes on each of 3 consecutive days. This 
ais found very troublesome by the students, and, feeling that it was not 
:cessary, a long series of test experiments was made by Mr. R. C. Reed, 
10 found that 1 boiling or steaming for 30 minutes gave just as good 
sults as the customary 3 boilings. As the media are not used for 2 or 
days after sterilization, during which time they are kept in an incu- 
itor, the method is well suited to student laboratories, not for the 
ason that it saves time in preparing the media, but it relieves the 
ngestion in the sterilizer and appreciably aids the student. When 
wrilized by this method the media must not be inoculated for several 
ys after their preparation or until they have stood in an incubator for 
least 18 hours to test their sterility. 
Media can be quickly sterilized by means of the autoclave when the 
mperature is raised from 110° to,115°C. While this method is quick 
d convenient, the high temperature seems to be detrimental to media 
r certain pathogenic bacteria. The autoclave, however, is quite 
tensively used. 
