248 SUMMARY OF CURRENT RESEARCHES RELATING TO 



authors' hands this method has greatly simplified the detection of these 

 parasites. 



Glycerin-agar in Fifty Minutes.* — R. G. Perkins describes the 

 following method for the easy and rapid making of glycerin-agar. 

 The materials used are agar 12 grm., peptone 10 grin., salt 5 grm., 

 and Liebig's extract 1\ grm. Witte's peptone and Liebig's extract 

 appear to be necessary, as the results are less good with others. 



Weigh an enamelled pan, preferably one with a double copper 

 bottom, as this reduces the chances of burning, with 1200 c.cm. of 

 distilled water, and record the weight. Place on the gas stove while 

 weighing the other materials, with about 150 c.cm. of additional water 

 to allow for evaporation. This is an important part of the process, as it 

 makes a greater dilution for the first solution of the materials. Add all 

 the materials at once and boil till the whole is in solution, which should 

 be in less than 15 minutes. Cool to 60° C. by the addition of enough 

 cold distilled water to keep the total weight up to about 150 grm. over 

 the sum of the pan, 1200 c.cm. water and the agar, etc. Make faintly 

 alkaline to litmus, and add the whites only of two absolutely fresh eggs, 

 beaten up in a little water. Boil, not too vigorously, until the medium 

 boils up clear, and the egg is completely coagulated. The weight at 

 this poiut should be the sum of the pan, the 1200 c.cm. of water, and 

 about 50 grm. for the added materials. Skim and pour into wire 

 funnels with filters of Schleicher and Scliull No. 580, which have just 

 had boiling water poured over them. The funnels are of the type 

 which can be bought with a rubber ring at the top for compression, but 

 I have found them more satisfactory when the top ring is of wire with 

 the rays soldered to it. The filter paper need not be creased, nor 

 an outside funnel used, accidents being very rare. If the room is 

 moderately warm, filtration takes place in a few minutes, usually 

 not requiring more than one sheet of paper divided into fourths. As 

 soon as the filtration becomes slow repeat with a fresh piece of paper, 

 the residual medium being reheated to the boiling point, and boiling 

 water being poured into the paper before the introduction of the agar. 

 As soon as the first 500 c.cm. have come through, it is the custom for 

 the students to add the glycerin or dextrose, etc., and to tube the media 

 while the rest is coming through. From the time that the first 

 weighing is begun until the time when the filled tubes are placed in the 

 sterilizer need not be over 50 minutes, and the students, even the first 

 time, accomplish it in an hour and a half. 



The resultant medium is transparent, almost colourless, unless it has 

 been burnt, when it will have a yellow colour. No difficulty has been 

 found in growing the ordinary strains of streptococcus, diphtheria or 

 tuberculosis, and a large proportion of pneumococcus cultures show good 

 development. The medium is firm enough for satisfactory plating, and 

 has adequate water of condensation. 



The use of distilled water is important, as also the special grade of 

 filter paper, but the most essential points are the excess of water during 

 the process, the absolute freshness of the eggs, and the preservation of 

 filter paper and media at the boiling point until they meet. 



* Johns Hopkius Hosp. Bull. xx. pp, 324-5. 



