526 THE CONTROL OF THE MILK SUPPLY 



into the churn through a fine metal gauze screen, covered with 

 a clean white cloth. A company in England lays down as one of 

 its regulations controlling farms contributing milk that each 

 " bucketful of milk shall, as soon as drawn from the cow, be 

 strained through a fine wire strainer covered with a clean woollen 

 cloth." The New York Milk Commission lays down a similar con- 

 dition, the metal screen to have a flannel cloth or layer of cotton. 

 The details are matters of convenience and custom, but the 

 principle oi prompt and careful straining is essential to success.^ A 

 similar advantage is gained by centrifugalising the milk. At the 

 Fabrick voor Gesteriliseerde Maelk, Amsterdam, it is the practice 

 after cooling and screening to centrifugalise the milk. On receipt 

 at the premises in Amsterdam the milk is at once screened, and 

 then raised to a temperature of 30° C. (86° F.) in order to facilitate 

 the centrifugalising process which follows. The milk and cream 

 thus separated are intimately remixed subsequently, by a series of 

 revolving rollers. In the process of centrifugalisation there is left 

 behind on the inside of the separator the usual residue, which 

 consists of a viscous looking mass of slime containing much d6bris, 

 hair, inorganic mud, and other particulate matter which has not 

 been arrested by straining. This separation may rightly be 

 regarded as a cleansing operation. We have frequently made 

 examination of the slime from the separator, and have found it 

 crowded with bacteria. B. tuberculosis has thus been separated, 

 and owing to this fact it is usual in Denmark to burn the slime 

 after centrifugalisation to prevent pigs from being fed upon it.^ 



1 One of the best strainers now on the market is the " Ulax." See Appendix 



S, p. 594- 



2 Though the straining of milk may be of some service in ridding it of any 

 large particles of dirt or other matter which it may contain, it is of but little 

 use in removing the dust, which, after all, constitutes the great bulk of filth 

 which dirty milk contains. The effect of straining, so far as dust is concerned, 

 was well shown in an experiment recently carried out at one of the American 

 agricultural stations. In this experiment it was found that though the straining 

 of milk left it cleaner, so far as the large particles were concerned, it proved of 

 but very little advantage in excluding dust bacteria. It was found that about 

 ■60 per cent, of the dirt from manure and the air was soluble in water, and that 

 no amount of straining would prove of any service in depriving the milk of this 

 soluble material. With the object of testing as to what extent dust and bacteria 

 found their way into the milk, trials were made with milking into covered pails 

 with apertures only 6 inches in width at the top, and into others with from two 

 or three times that extent of opening in the pail. With the 6-inch opening it 

 was found that the number of germs present in a certain quantity of milk was 

 2300, whereas in the milk drawn into the ordinary pail with the wide top the 



