268 MILK AND ITS HYGIENIC RELATIONS 



dealing with the general milk supply, is too frequently overlooked 

 when the milk for infants is under consideration. A rnilk of the 

 greatest purity introduced into a dirty home or placed in the hands 

 of careless persons may become seriously contaminated before it 

 reaches the child for whom it was intended. Perhaps one of the 

 most serious difficulties encountered in the preservation of milk 

 in the poorer class of homes arises from the absence of any satis- 

 factory place for storage of milk. In this country there are no 

 regulations requiring the delivery of milk at a low temperature, 

 and it is probable that the bulk of the milk supplied by dairymen 

 in this country is delivered at a temperature at which bacterial 

 growth is proceeding with considerable rapidity. In many homes the 

 only safe storage place is in a cupboard adjacent to the fire, separated 

 only from the chimney by one layer of bricks. Here the milk, 

 already warm, becomes still warmer, and the bacteria grow at an 

 increasing rate of speed. A small degree of contamination in the 

 original milk may therefore produce a highly contaminated milk 

 before such milk is taken as food. Further, contamination may 

 arise from the use of dirty vessels and from manipulation with 

 dirty hands, or from leaving the milk uncovered and exposed to 

 aerial contamination. It is hardly necessary to elaborate these 

 sources of contamination any further, as everyone will be able to 

 supply additional personal data. 



The bacterial content of raw milk, when it reaches the 

 consumer in the course of the daily milk round, will usually have 

 reached at least one million organisms per c.c. (a cubic centimetre 

 is about eighteen minims), and will often be many times that figure. 

 The high degree of bacterial contamination is not realised owing 

 to the opacity of milk. 



Houston, summing up the results of his investigations upon 

 bacterial examinations of milk, says : ' The whole history of milk 

 from start to finish, from secretion by the cow to ingestion by the 

 human being, is fraught with " potential " risk to the consumer. 

 The influence of time and temperature on the microbial qualities 

 of milk is most important. Milk is not generally consumed fresh, 

 and commonly many hours elapse between the time of milking 

 and the time when the milk reaches the consumer. During this 

 period bacteria multiply in the milk at a rate which is governed 

 chiefly by the temperature. It follows that a comparatively clean 

 milk to start with, after a lapse of some time and under the influence 

 of a high temperature, will yield worse results as judged by the 

 ordinary bacteriological tests than a milk containing initially an 

 excess of filth but which is maintained at a low temperature or 

 which has been examined shortly after milking.' 



