i 4 MILK AND THE PUBLIC HEALTH CHAP. 



above three varieties described by the writer. lu addition, 

 they mention as scanty, or often absent, eosiuophile cells, 

 vacuolated cells, and cells of indeterminate nature. 



Their results are very similar to those previously obtained 

 by the writer, the essential difference being that they do not 

 regard any of the cells as of the nature of leucocytes. They 

 adopt the view of Winkler that the cells found in normal milk 

 are chiefly young epithelial cells and cells of the germinal 

 layer which have been thrust into the lumen of the alveolus 

 and so appear in the milk stream, and that none of them are 

 leucocytes. 



Milk Sediments. In addition to cellular elements, the 

 deposits obtained from ordinary milk, either by centrifugal isa- 

 tion, or on standing, contain a number of other substances. 

 In view of the use which has been made in practical milk 

 examinations of the investigation and measurement of such 

 deposits, their character and sources are worth some consideration. 



The amount of sediment obtainable from a given sample 

 will vary with the method of measurement, a larger deposit 

 being obtained with a fast-running centrifuge than by sedi- 

 mentation in a conical glass. 



The terms " dirt " or " filth " are often applied to such 

 sediments, but these are expressions which imply judgment 

 in advance, and are not always applicable, certainly not always 

 to the whole of the deposit. 



The sediment is composed in part of leucocytes, in part 

 of inorganic substances, such as sand, but for the most 

 part of dust particles, cotton fibres, manurial matters, particles 

 of straw, hairs, etc., and bacteria. In milk as vended under 

 ordinary present-day conditions, the greater part of it is 

 manurial in origin. 



The characters of the cellular elements, and the general 

 prevalence of bacteria, can be readily studied by making 

 microscopic preparations from a little of the deposit. 



The relationship of the amount of sediment to the general 

 cleanliness of collection and transmission has been demon- 

 strated by a number of observers. 



For example, Houston 1 with London milks recorded the 

 following : 



1 Report to London County Council, 1905. 



