22 MILK AND THE PUBLIC HEALTH chap. 



The churn which receives the milk is frequently placed 

 in a dusty place, and is very often uncovered. 



The clothes of the milker are usually highly dust-laden, 

 and as the wearing of a clean overall is quite exceptional, 

 many bacteria are added to the milk from this source. 



(c) The hands of the milker add their quota of bacteria 

 to the milk, for even when washed to start with, they soon 

 become filthy from the dirt upon the cows. Most of this dirt, 

 with included bacteria, is washed into the milk. The iniiuence 

 of the milker in adding bacteria to milk is clearly illustrated 

 by the following experiment recorded by Stocking.^ The 

 average of 19 tests with two milkers who had had no 

 training in dairy sanitation, and one milker who was a 

 graduate of the Connecticut Agricultural College, showed 

 17,105 bacteria per c.c. for the untrained men, and 2455 for 

 the trained man. The only difference between the men was 

 the knowledge of what constituted contamination gained by 

 the college graduate, who was a student of bacteriology. 



3. Bacteria introduced from Milh Vessels. — When improperly 

 cleaned, these are a source of great bacterial contamination to 

 the milk. Orr quotes Harrison as carrying out the following 

 series of experiments. He rinsed out the cans with 100 c.c. 

 sterile water, and then estimated the number of organisms 

 per c.c. of this water. 



Series A. Ten samples were examined from cans improperly cleaned, 



and gave from 215,000 to 806,320 organisms per c.c. 

 ,, B. Ten samples, from cans cleaned by washing with tepid water 



and scalding, gave from 13,080 to 93,400 per c.c. 

 „ G. Five samples, from cans cleaned by washing with tepid water 



and then steaming for 5 minutes, gave from 355 to 1792 



organisms per c.c. 



Even if cans are properly scalded, it is a not uncommon 

 practice to wash them out afterwards with cold water. If 

 the water used for this purpose is not from a pure source 

 this may be a further source of bacterial contamination. 



4. From Artificicd or Special Milh A2jparatus. — The com- 

 monest apparatus used, not strictly appertaining to milking, 

 is a milk -strainer. It is an almost universal practice of 

 the cow-keeper to strain the milk, usually immediately after 



' Bulletin No. 43, Storrs Experiment Station. 



