54 SOLID MEDIA 



C. Boil an egg hard. Remove the shell, cut up the egg into pieces, and 

 place in small Petri, or other covered glass, dishes. Sterilize the watch-glasses 

 or dishes at 115 C. 



D. Lubenau recommends yolk of egg media for growing tubercle and 

 diphtheria bacilli. The procedure is as follows : 



1. Prepare a neutral broth (p. 30) containing 1 per cent, of glucose (for 

 the diphtheria bacillus) or 3 per cent, of glycerin (for the tubercle bacillus). 

 Distribute in quantities of 100 c.c. in 2J-litre flasks. Sterilize. 



2. Wash an egg with warm water and soap. Lay the egg in a Petri dish, 

 pour a little alcohol over it, and set light to the alcohol. 



Make a hole in the shell with a sterile instrument, and pour the yolk into 

 one of the flasks of broth. Add the yolks of five eggs to each flask. Shake 

 the flasks well. 



3. Distribute the medium into tubes. Slope the tubes in a serum 

 coagulator (p. 51). Heat for 2 or 3 hours at 90 C. on three successive 

 days. 



[E. Dorset's egg medium. " The eggs are thoroughly cleansed with water 

 of any adherent dirt, and then washed with 5 per cent, carbolic solution, 

 and allowed to partially dry. The ends of the eggs are then gently dried in 

 the flame, and pierced with a burned sharp forceps. The hole at one end 

 should be about f in. in diameter, and the membrane broken ; the other 

 end which is to be blown into should be smaller, and the membrane left 

 unbroken if possible. The eggs are then blown into a sterile Erlenmeyer 

 flask, the blowing being done from the cheeks, which will help to avoid 

 spilling saliva and leakage of air around the outside of the egg. To the egg 

 is then added 10 per cent, of water by volume of the weight of the eggs. 

 The mixing is done by a twirling motion of the flask or by gently stirring with 

 a glass rod. Bubbling is to be sedulously avoided. The mixture is then 

 strained through cheese-cloth by gravity and tubed. The tubes are then 

 inspissated at 70 C. for 2-2 J hours in a moist chamber " (Park and Krum- 

 weide).] 



Meat. 



Into a litre flask put 500-600 grams of finely chopped lean beef. Add 

 sufficient normal soda solution to make the reaction neutral or slightly 

 alkaline. Plug the flask with wool. Sterilize at 115 C. 



Internal organs. 



The placenta, liver, spleen, kidneys, etc., can be used as culture media. 

 The organs must be removed with the usual aseptic precautions from healthy 

 animals which have been recently killed. 



The technique recommended by Gueniot for the preparation of placenta 

 will serve as an example of the method of preparing these culture 

 media. 



1. Lay the placenta (if possible receive it) in a sterile basin with the 

 uterine surface uppermost. Scorch this surface with a large heated metal 

 plate. 



2. Cut off a number of pieces with a sterile forceps and scalpel, and place 

 them with the scorched surface downwards in sterile Petri dishes, or better 

 in large sterile tubes. 



Place the dishes and tubes in the incubator at 37 C. for a day or two to 

 control the technique. Thos that remain sterile (at least 60 per cent.) can 

 then be used as culture media. 



