THE SANITARY FACTORS 113 



We have as yet, and in spite of ample knowledge, failed 

 to make our American milk supplies what they should be. 

 This is partly because we have been too timid to insist that 

 good milk not only costs more to make but is worth more and 

 must therefore be paid for, and partly because we have not 

 yet taught the public as we should that the only safe milk 

 is cooked milk, and for infants, milk that is pasteurized 

 preferably in the final container. I have myself lived through 

 the last year of the period now happily remote when no 

 milk was pasteurized by anybody; through the next in which 

 only pioneers like Nathan Straus preached or practiced pas- 

 teurization, while many, if not most, physicians deprecated 

 the practice; through the one following, in which the scales 

 began to turn in favor of pasteurization; and into the present 

 when almost no one fully informed on the subject actively 

 opposes pasteurization. And yet, even to-day, some phy- 

 sicians are shortsighted enough to tolerate if not to recom- 

 mend the general use of raw milk, which still constitutes 

 the great bulk of the milk used by infants and adults all 

 over the land. Such use of raw milk we must count as long 

 as it lasts one of our worst public health failures. 30 



CLARIFICATION AND OTHER PROCESSES 

 Ordinary farm milk contains more or less dirt, as well 

 as natural waste from the udder of the cow, and often 

 pus and bacteria from udder inflammations unnoticed 

 or unnoticeable. By passing the milk through a centrif- 

 ugal machine, or "clarifier," these matters are largely 

 thrown out in a residuum which consists partly of sub- 

 stances normally present in milk and partly of those 

 which are adventitious or abnormal. 31 (Plate 5.) The 

 quantity of this is stated by North to be ordinarily 

 about one pound to every six thousand quarts. The 

 process has come into wide use in milk plants as a trade 



