154 BIOLOGY AND TECHNIQUE 



complete a bluish purple shade, that it is incomplete. If test is satisfactory, 

 slightly acidify the broth with glacial acetic acid and bring slowly to boiling 

 point and boil gently for ten minutes and filter through paper. Add 2 per 

 cent agar and 0.5 per cent salt, autoclave to dissolve agar, and proceed from 

 this point as usual, clearing with egg and setting to P H 7.5, or any desired 

 reaction. 



Vedder Starch Agar. Beef infusion agar is prepared without salt and 

 pepton. This is adjusted to P^ 6.8, 10 grams of corn starch is added to 

 each liter, and the mixture is heated in the autoclave for 20 minutes at 15 

 pounds. It is tubed and sterilized. This medium has been recommended by 

 Vedder for the cultivation of gooococcus. 



Welch's Modification of Guarnieri's Medium. This medium is made on 

 a meat infusion basis, according to the directions given for the preparation 

 of meat-infusion agar. It contains 5 grams of agar, 80 grams of gelatin, 

 5 grams of NaCl, and 10 grams of pepton to one liter. It should be adjusted 

 to a neutral reaction. It is used for stab cultures and is designed chiefly 

 for pneumococcus cultivation and storage. 



Dorsett Egg Medium. This medium is chiefly useful for the cultivation 

 of tubercle bacilli. 



1. Carefully break eggs and drop the contents into a wide-mouthed flask. 

 Break up the yolk with a sterile platinum wire, and shake up the flask until 

 the whites and yolks are thoroughly mixed. 



2. Add 25 c.c. of distilled water to every four eggs; strain through sterile 

 cloth. 



3. Pour 10 c.c. each into sterile test tubes and slant in an inspissator 

 and expose to 73 C. for four to five hours on two days. 



4. On the third day, raise the temperature to 76 C. 



5. The sterilization may be finished by a single exposure to 100 C. in 

 the Arnold sterilizer for fifteen minutes. Before inoculation, add two or 

 three drops of sterile water to each tube. 



LUBENAU'S GLYCERIN- EGG. To 1 liter of veal broth containing 2 per 

 cent pepton, 5 per cent of glycerin is added. Neutralize this to litmus, 

 and to every 200 c.c. add 10 fresh eggs. The mixture is thoroughly stirred, 

 and when homogeneous, is tubed, slanted and inspissated, as in the case of 

 other egg media. 



PETROFIF'S MEDIUM. I. Meat Juice. 500 grams of beef or veal are 

 infused in 500 c.c. of a 15 per cent solution of glycerin in water, in a cool 

 place. After 24 hours the meat is squeezed in a sterile press and the infusion 

 collected in a sterile beaker. 



II. Eggs. The shells of the eggs are sterilized by 10 minute immersion 

 in 70 per cent alcohol. They are broken into a sterile beaker, well mixed 



" Welch, Bull. Johns Hopkins Hosp., 1892, vol. 3, p. 127. 



