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. 



FIG. 18. 



Schultz* Rapid Method of Preparing Sutrient 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 this is coagulated \ then filter again. Always mois- 

 ten the filter ivitJi 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. 



