TECHNICAL APPENDIX. 181 



normal soda lye (indicator, phenolphthaleiii).* We 

 then filter, pour into test tubes, and sterilize. 



(b) From meat extract : 10 gm. meat extract are dis- 

 solved in 1,000 gm. water, 5 gm. sodium chloride and 

 10 gm. peptone are added, the solution is neutralized 

 and well sterilized several times. 



7. Potato water for tubercle bacilli : 500 gm. peeled 

 potatoes are rubbed upon a grater, allowed to remain 

 over night in 500 gm. water in the refrigerator, de- 

 canted, filled up to 1000 gm., cooked for an hour in the 

 water-bath, filtered, four per cent glycerin is added, 

 and the mixture sterilized. 



8. Gelatin nutrient media. 



(a) Meat water-peptone gelatin (ordinary "gela- 

 tin" or "nutrient gelatin" of the laboratories). 



To 1,000 gm. bouillon (vide nutrient bouillon) are 

 added 100 gm. gelatin, 10 gm. peptono, 5 gm. sodium 

 chloride, the mixture is heated in the steam chamber 

 until all the ingredients are liquefied, neutralized 

 with normal soda lye, sterilized, and filtered. After 

 the melted gelatin is placed in test tubes it is again 

 sterilized. 



(6) Meat- water gelatin: the same as under (a), but 

 without peptone and sodium chloride. 



(c) Beer-wort gelatin is made by adding ten per 

 cent gelatin to the wort ; it should not be neutralized. 



(d) Plum-decoction gelatin : 500 gm. dried plums 

 are cooked in 500 gm. water, the fluid is poured off, 

 and the plums are again cooked with 500 gm. water. 



* Illustration : Ten cubic centimetres bouillon require for sat- 

 uration 2.2c.c. one-tenth normal soda lye; l,000c.c. bouillon 

 require for saturation 220 c.c. one-tenth normal soda lye, or 22 

 c. c. normal soda lye. 



