SPECIAL EXAMINATIONS 367 



soiled and uncleansed skin near the udder, and from the 

 dust of the byre. 



Suggested Bacteriological Standard (Newman). 

 (.) Acidity of 100 c.c. + 2 c.c. phth. (o-i per cent) to 

 be not more than 25 c.c. N/io alkali. 

 (b.) No excess of blood or pus cells. 

 (c.) No B. coli, B. enteritidis sporogenes, nor B. 

 enteritidis (Gaertner) in i c.c. 

 (d.) The milk to be non-virulent. 



The New York Milk Commission specify that certified 

 milk shall contain not more than 30,000 bacteria per c.c., 

 and in Philadelphia, the Commission standard is not more 

 than 10,000 per c.c., and little difficulty has been experienced 

 in conforming to this test. Boston has fixed a limit for 

 ordinary milk of 500,000 per c.c., Milwaukee of 250,000, 

 and Rochester, N.Y., of 100,000 per c.c. The average 

 content in this country is 400,000 per c.c., as sold. 



Microscopic Examination. Shows round oil globules 

 and a little epithelium. Abnormal constituents are : 

 much epithelium, pus cells, conglomerate masses and 

 casts of lacteal tubes, and colostrum. 



Quantitative Examination. Decimal mode of dilution. 

 Add 9 c.c. of water to each of a number of test tubes, plug, 

 and sterilize. 



Add i c.c. of milk sample to No. i tube : 



dilution = i-io, or i c.c. = o-i c.c. milk. 

 Add i c.c. of No. i tube to No. 2 tube : 



dilution = i-ioo, or i c.c. = o-oi c.c. milk. 

 Add i c.c. of No. 2 tube to No. 3 tube : 



dilution = i-iooo, or i c.c. = o-ooi c.c. milk. 

 Add i c.c. of No. 3 tube to No. 4 tube : 



dilution = 1-10,000, or i c.c. = o-oooi c.c. milk. 



And so on for any number of dilutions, mixing well each 

 time, with sterile pipette. 



Plate i c.c. of the various dilutions on gelatin and 

 agar, and count colonies in twenty-four to forty-eight 

 hours. (Begin plating with weakest dilutions, if the 

 same pipette is to be used throughout.) 



