CULTURE MEDIA. 45 
metres thick is placed at the bottom of this cylinder and hot water 
is poured upon it while the stopcock of the outlet tube is open. This 
washes out the cotton and prepares the filter for the agar solution. 
The apparatus is supported upon a tripod, not shown in the figure. 
Filtration is said to occur rapidly when the air in the central cylinder 
is compressed by means of the hand bellows attached to the tube b. 
4--- SSS 
roy 
= 
Fie. 18. 
Schultz’ Rapid Method of Preparing Nutrient Agar-Agar.— 
Place one thousand five hundred cubic centimetres of water in an en- 
amelled iron pot; add eighteen grammes of agar-agar, broken in small 
pieces, and place upon a gas stove; boil for half an hour; add while 
boiling two grammes of Liebig’s extract of beef; remove from fire and 
cool to 60° C.; then add ten grammes of dry peptone, five grammes 
of sodium chloride, and the contents.of one egg beaten up in a 
sufficient quantity of water to supply that lost by evaporation; neut- 
ralize the mixture by the addition of dilute hydrochloric acid; boil 
again for five or ten minutes; filter through white filter paper. If 
the filtrate is not entirely clear add to it the albumen of a second 
egg and boil until thisis coagulated; then filter again. Always mots- 
ten the filter with water before filtering solutions containing 
gelatin or agar-agar. When the process is completed the amount 
of filtered culture medium should be about one thousand cubic centi- 
metres. 
