BACTERIA PATHOGENIC TO MAN', 



1. The number of bacteria present at the time of milking and twenty-four, forty- 

 eight, and seventy-two hours afterward in milk obtained and kept under correct con- 

 ditions. 



No preservatives were present in any of the following specimens: 



Number of Bacteria in Pure Commercial Milk. 



TABLE III. Milk obtained where every reasonable means was taken to ensure clean- 

 liness. The long hairs on the udder were clipped ; the cows roughly cleaned and 

 placed in clean barns before milking ; the udders were wiped off just previous to milk- 

 ing ; the hands of the men were washed and dried ; the pails used had small (six-inch ) 

 openings, and were thoroughly cleaned and sterilized by steam before use. Milk cooled 

 within one hour after milking to 45 R, and subsequently kept at that temperature. 

 The first six specimens were obtained from individual cows ; the last six from mixed 

 milk as it flowed at different times from the cooler. Temperature of barns 55 F. 



Number of Bacteria in 1 c.c. of Milk. 1 



From six individual cows. 

 5 hrs 

 after milking. After 24 hrs. After 48 hrs. After 72 hrs. 



500 700 12,500 Not counted. 



700 700 29,400 



19,900 5200 24,200 " 



400 200 8,600 " " 



900 1600 12,700 " " 



13,600 3200 19,500 



Average 6000 1933 17,816 



From mixed milk of entire herd. 



6900 12,000 19,800 494,000 



6100 2,200 20,200 550,000 



4100 700 7,900 361,000 



1200 400 7,100 355,000 



6000 900 9,800 445,000 



1700 400 8,700 389,000 



Average 4333 2766 10,583 329,000 



Twenty-five samples taken separately from individual cows on another day and tested 

 immediately averaged 4550 bacteria per c.c. and 4500 after twenty-four hours. These 

 twenty -five specimens were kept at between 45 and 50 F. 



2. Milk taken during winter in well-ventilated, fairly clean, but dusty barns. 

 Visible dirt was cleaned off the hair about the udder before milking. Milkers' hands 

 were wiped off, but not washed. Milk pails and cans were clean, but the straining cloths 

 dusty. Milk cooled within two hours after milking to 45 F. 



1 Number of bacteria obtained from development ot colonies in nutrient agar in Petri plates. The 

 nutrient medium contained 2 percent, peptone and 1.2 per cent, agar, and was faintly alkaline to 

 litmus. One set of plates were usually left four days at about 20 C., and one set twenty-four hours 

 at 37 C., and then twenty-four hours at 20 C. From 5 to 30 per cent, more colonies developed as a 

 rule in the plates kept at room temperature than in those kept for twenty-four hours at 37 C. The 

 milk was diluted as desired with 100 or 10,000 parts of sterile water, and 1 c.c. of the diluted milk 

 was added to 8 c.c. of melted nutrient agar. Plates containing over 1000 colonies were found to be 

 inaccurate, in that they gave too low totals. Apparently a considerable number of bacteria failed 

 to develop colonies when too many were added to the nutrient agar. Nutrient gelatin was found to 

 be more troublesome and not to yield more accurate results than nutrient agar. 



