1899] MICROSCOPICAL JOURNAL. 331 



General Directions. — Prepare for culture media, 5 

 tubes of potatoes, 5 tubes of milk, 5 tubes of litmus milk, 

 5 tubes of glucose agar, 5 tubes of glycerin agar, 4 fer- 

 mentation tubes of bouillon containing glucose, 4 con- 

 taining lactose, and 4 containing saccharose. 



Preparatin of Potato for a Culture Medium. — Se- 

 lect medium sized potatoes, thoroughly wash and cut out 

 with a cutter made for this purpose, a cylinder 3 to 4 cm. 

 long (oblong pieces cut with a knife will do quite as well). 

 Ordinarily 2 cylinders can be cut from each potato. The 

 inclined surface is obtained by cutting out the potato 

 projecting above the frame of the cylindrical knife. All 

 of the skin must be removed. Wash the potato cylinders 

 in cold, running water for some 5 minutes (a longer time 

 is preferable) and place them in test tubes of the proper 

 site (large or small according to size of cutter used), and 

 add about 1 c.c. of water to each tube. Sterilize them by 

 discontinuous boiling or steaming for 20 minutes each day 

 for three consecutive days. Wipe, label, and store. 



Preparation of Milk for a Culture Medium. — Place 

 about 100 c.c. of fresh milk in a beaker in the ice box 

 and allow it to stand for from 10 to 15 hours. Then care- 

 fully remove all the cream. It is well to filter the milk 

 through a thin layer of absorbent cotton to remove any 

 masses of cream. The reaction should be tested and if 

 strongly acid it should be rejected or made 1.5 per cent acid 

 to phenolphthaleni by the addition of n 1 sodium hydrate. 

 Distribute the skimmed milk in small test tubes (7 c.c. in 

 each) and sterilize by discontinuous steaming in the same 

 manner and for the same length of time as the potatoes. 

 Label and store in locker. 



Preparation of Litmus Milk for a Culture Medium 

 — This is prepared the same as the milk medium with the 

 addition of enough of an aqueous solution of litmus to 

 impart a decidedly blue color to the milk. Sterilize, label 

 and store the same as the milk. 



