274 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



microscopic organisms in a bouillon culture, but it is safer 

 to exclude a milk from the market when these three tests 

 agree: 



"1. Microscopic examination of the sediment shows 

 streptococci, diplococci, or cocci. 



"2. The plate from the same sample shows colonies 

 resembling streptococci colonies exceeding a count of 

 100,000 to a cubic centimetre. 



"3. The bouillon culture from these colonies shows 

 long-chain streptococci alone or in great excess compared 

 with the other bacteria present. 



"Milk showing in the stained sediment both abund- 

 ance of long-chain streptococci and pus should be con- 

 demned as unsafe." 



The bouillon used in this examination may be pre- 

 pared as follows : 



"Infuse 500 g. finely chopped lean meat 24 hours 

 with 1,000 c.c. distilled water in refrigerator; restore loss 

 by evaporation; strain infusion through cotton flannel." 

 (Or, dissolve 5 g. of beef extract, preferably Liebig's, 

 in 1,000 c.c. distilled water.) 



" Add 1 per cent, peptone. Warm on water bath, 

 stirring until peptone is dissolved. 



" Heat over boiling water or steam bath thirty min- 

 utes. Restore loss by evaporation. 



"Titrate, adjust reaction to + 1 per cent, by adding 

 normal sodium hydrate. 



"Boil two minutes over a free flame, constantly stir- 

 ring. Restore loss by evaporation. 



"Filter through absorbent cotton, passing the liquid 

 through until clear. Titrate and record final reaction. 

 Tube, using 10 c.c. to each tube. Sterilize." 



