6o2 



LABORATORY EXERCISES 



2800 c.c. 

 38 grams 

 14 grams 



Water extract beef 



Peptone 



Salt 



(Bouillon alone) 



[40 c.c. 



Glycerin 



After boiling, to this is to be added enough of 10 per cent. NaOH to neutralize 

 the acidity of the meat extract. It must be neutralized until it is alkaline to blue 

 litmus and acid to phenolpthalein. It is again filtered and is ready for use. Tu- 

 bercle bacilli grow exceptionally well in this second solution. 



Fresh Bouillon (Another formula). — Standard peptonized beef bouillon is made 

 as follows: To 500 grams of finely minced lean beef add 1000 c.c. of distilled water. 



-Diagram illustrating construction and action of Arnold steam sterilizer. 

 (Fig. 15, p. 39, Schneider, Pharmaceutical Bacteriology, 1912.) 



The soluble parts may be removed from the meat by allowing the water to stand 

 on it for twenty-four hours in the ice chest or for one hour in the water bath at 55°C. 

 The second method is perhaps preferable. Then boil for sixty minutes either in the 

 steamer, or in a covered dish. Filter through clean cloth, using pressure (meat press) , 

 cool, and remove fat by filtering through filter paper; make up to 1000 c.c. by addi- 

 tion of more water; then add i per cent. Witte's peptonum siccum and 0.5 per cent, 

 c.p. sodium chloride. Steam one-half hour, filter, cool, titrate, add required alkali, 

 steam again for one-half hour, filter pipette into test-tubes or flasks, and autoclave or 

 heat for a minimum time in the Arnold sterilizer (Fig. 212). Plugs should be well 

 made and fit tightly; glassware should be scrupulously clean. For some purposes 

 both the peptone and the salt should be omitted. A greenish bouillon indicates 

 insufficient boiling, and will usually throw down some additional vexatious pre- 



