GELATIN 23 



10 grams, salt 5 grams, glucose 10 grams and 15 grams of agar in 1000 c.c. of water 

 containing the white of egg (one to two eggs), then boiling in the rice cooker and 

 filtering. 



GLYCERINE AGAR. 



Add the agar to 6% glycerine bouillon instead of nutrient bouillon, or the gly- 

 cerine may be added to nutrient agar which has been melted. Glycerine agar with 

 a reaction of o makes an excellent base for blood and serum media for use in cul- 

 turing delicate pathogens. 



GLYCERINE AGAR EGG MEDIUM. 



Take the white and the yolk of one egg and mix thoroughly in a vessel kept 

 between 45 and 55 C. with an equal amount of glycerine agar. Tube the medium, 

 inspissate in a rice cooker as for serum tubes, and sterilize as for blood-serum tubes. 



This makes an excellent medium for growing tubercle bacilli. As egg medium 

 has a tendency to be dry, it is well to add i c.c. of glycerine bouillon to each slant 

 before autoclaving. 



NUTRIENT GELATIN. 



Place in a mortar 3 grams of Liebig's extract, 10 grams of peptone and 5 grams 

 of sodium chloride. Dissolve the whites of one or two eggs in 1000 c.c. of water. 

 Then add this egg-white water, little by little, to the meat extract, peptone and salt, 

 in the mortar, until a brownish solution is obtained. Pour this into the inner 

 compartment of the rice cooker and bring the temperature up to 45 C. (This 

 preliminary elevation of temperature is better carried out in some heated water in 

 a pan, as the heating by means of the salt solution in the outer compartment of the 

 rice cooker is difficult to control, so that a temperature approximating 70 C. might 

 be obtained and the albumin of the white of egg coagulated. The temperature in 

 the outer compartment might be approaching boiling before the contents of the inner 

 compartment would show 45 C.) Now take about 120 grams of "gold label" or 

 other good quality gelatin (12%) and crush it down in the meat extract egg- water 

 solution in the inner compartment of the rice cooker. 



The gelatin quickly goes into solution at 45 C. Gelatin being quite acid it will 

 probably be found upon titration that the reaction is about +4%. N/i NaOH 

 solution is added to bring the reaction to about +1%. or 3 c.c. N/i NaOH for 

 each 100 c.c., provided the reaction were exactly +4%. The procedure is the 

 same as for bouillon. The color reaction is not quite as distinct with gelatin as with 

 bouillon. 



Having neutralized and allowed to boil for fifteen minutes, we filter through 

 filter-paper in a hot funnel. As it is very important that gelatin should be perfectly 

 clear, it is better to filter through filter-paper than through cotton. The filter-paper 

 should be very thoroughly wetted with very hot water before filtering gelatin or 

 agar. 



