LABORATORY AND TEACHING METHODS 603 



cipitate when heated in the test-tubes. Other meats may be substituted for beef, 

 and other peptones for Witte. 

 Glycerin Bouillon. 



1. Measure out nutrient bouillon, looo c.c. 



2. Measure out glycerin, 60 c.c. ( = 6 per cent.) and add to the bouillon. 



3. Tube and sterilize as for bouillon. 

 Sugar Bouillon. 



1. Measure out nutrient bouillon, 1000 c.c. 



2. Weigh out glucose, 20 grams ( = 2 per cent.) and dissolve in the fluid. 



3. Tube and sterilize as for bouillon. Ordinary commercial glucose serves the 

 purpose equally well, but it is not recommended, as during the process of steriliza- 

 tion the medium gradually deepens in color. In certain cases a corresponding per- 

 centage of lactose, maltose, or saccharose, is substituted for glucose. 



LESSON 10 



Egg Albumen. — Absolutely fresh eggs should be used. The end of the egg from 

 which the albumen is poured must be thoroughly flamed before it is broken, and care 

 must be used in the transfer to test-tubes, so as to exclude air-borne germs; other- 

 wise, the sterilization will be diiificult. By being placed in a steam sterilizer and 

 sterilized by intermittent sterilization for three days, care being taken to leave off the 

 cover of the sterilizer (Fig. 211), the albumen will be found to be white, quite hard 

 and ready for use. If the lid of the sterilizer is kept on and the heat becomes too 

 great, bubbles will form in the albumen and thus spoil its usefulness. The albumen 

 of eggs may be cut with sterile scissors. 



Egg Albumen (After Eyre, The Elements of Bacteriological Technique, 1902: 

 160). 



1. Break several fresh eggs (hens', ducks', or turkeys' eggs) and collect the 

 "whites" in a graduated cylinder, taking care to avoid admi.xture with 3'olks. 



2. Add 40 per cent, distilled water, and incorporate the mixture thoroughly by 

 aid of an egg whisk. 



3. Weigh out 0.15 per cent, sodium hydrate and dissolve it in the fluid (or add 

 the amount of decanormal caustic soda solution (see infra) calculated to yield the 

 required percentage of soda in the total bulk of the fluid — i.e., 0.375 c.c. of deca- 

 normal NaOH solution per 100 c.c. of the mixture. 



3a. Glucose to the extent of i or 2 per cent, may now be aaded, if desired. 



4. Strain the mixture through butter muslin and filter through a porcelain 

 filter candle into a sterile filter flask. 



5. Tube, and stiffen at ioo°C. in the serum inspissator, or in the steam sterilizer 

 with the lid off. 



• 6. Incubate at 37°C. for forty-eight hours and eliminate any contaminated tubes; 

 store the remainder for future use. 



Egg Yolk. — This is poured into test-tubes and solidified in a slanting position bj' 

 8o°C. heat, or the egg may be boiled hard and the yolk cut with a sharp knife and 

 transferred to sterile petri dishes. If desired the yolk and white may be mixed 

 before solidifying, i.e. by shaking the egg vigorously before breaking the shell. 



