It is some years since it was shown that when milk is allowed to stand the bacteria are carried upward with the fat globules so that the cream layer contains a far greater number of micro-organisms than the underlying skim milk.
This teaching has been corroborated many times, although it has been frequently forgotten in practice and in experiment. In a study published about one year ago,1 from the Research Laboratory of the New York Board of Health, I went somewhat deeper into this question, in which by chance I had become interested. As some of those present are acquainted with this investigation, I shall not review the experiments which I undertook in this work. Briefly stated, they resulted in establishing a fact which had not, I believe, been previously noted, namely, that the bacteria which the cream is known to harbor, are