158 NUTRIENT MEDIA 



When opened out the filter assumes the shape repre- 

 sented in figure 100, c. 



The folded filter is next placed inside a glass funnel 

 supported on a retort stand, and moistened with hot 

 distilled water before the filtration of the medium is 

 commenced. 



Liquef iable solid media are filtered through a specially 

 made filter paper "papier Chardin" which is sold 

 in boxes of twenty-five ready-folded filters. 



Gelatine, when properly made, filters through this 



FIG. 101. Hot- water filter funnel and ring burner. 



paper as quickly as bouillon does through the Swedish 

 filter paper, and does not require the use of the hot- 

 water funnel. 



Agar, likewise, if properly made, filters readily, 

 although not at so rapid a rate as gelatine. If badly 

 "egged," and also during the winter months, it is 

 necessary to surround the glass funnel, in which the 

 filtration of the agar is carried on, by a hot- water 

 jacket. This is done by placing the glass funnel inside 

 a double-walled copper funnel the space between the 



