1 8 CLEAN MILK 



i 



air through the opening in the teat and find their way into the cavity 

 or milk-cistern in the lower part of the udder. Among the more 

 common germs found in the first or fore milk are the streptococci. 

 Streptococci are those germs which are frequently responsible for 

 various forms of inflammation in man and animals, and are also 

 found in milk withdrawn from inflamed udders of cows affected 

 with garget. That the streptococci ordinarily present in the teats 

 of healthy cows are identical in appearance with the disease-pro- 

 ducing streptococci is now known, but they are present in the 

 cleanest milk, as they naturally enter the teats and milk cistern 

 from the outer air. For this reason the fore milk is rejected by 

 those producing clean milk. 



Disease-producing streptococci are perhaps among the most im- 

 portant of the germs causing serious forms of infantile diarrhoeas. 

 Therefore when streptococci (with leucocytes) are present in ex- 

 cess the milk should be condemned for food (see p. 250). As 

 the milking proceeds the germs in the milk-cistern and teat are 

 washed away so that the latter part of the milk withdrawn is 

 often absolutely free from germs until contaminated with the out- 

 side air. Occasionally germs may persist in milk throughout milk- 

 ing, and the strippings may contain as many as 500 germs to the 

 cubic centimeter. If the latter part of the milk is withdrawn 

 through an absolutely clean milking tube into an absolutely clean 

 bottle, it will often be wholly without germs, and may keep sweet 

 for months or years if it does not come in contact with the 

 air. Such painstaking cleanliness as is necessary to make this ex- 

 periment successful, is not of course practicable in actual dairy 

 work, since it is not economically possible to throw away a larger 

 part of the milk nor to withdraw milk so that it will not come in 

 contact with air.* Therefore, under any ordinary conditions a cer- 

 tain number of germs must inevitably be present in the cleanest 

 milk — perhaps 200 to 4,000 as the least number to the cubic centi- 

 meter.f 



* Since writing the above the use of the milking machine (see Appendix) 

 makes withdrawal of milk without exposure to air practicable. 



f The average contamination of milk within the udder amounts to 500 bac- 

 teria per c.c. for all the milk from one milking; while there are, according to 

 Conn, 6,900 bacteria on the average in the foremilk. 



