68 THE MILK QUESTION 



crucible. This is attached to a filtering-flask which is con- 

 nected with a vacuum pump. In this way a pint of milk 

 may quickly be drawn through. 



The Lorenz apparatus is made of copper with a jacket for 

 circulating warm water, as it has been found that cold milk 

 filters very slowly. 



These dirt tests may be made "while you wait," and the 

 dirt shown to the farmer; or they may be appUed at the 

 dairy where the milk is received, or in the city laboratory. 

 A very good plan is to mail the Kttle disks of cotton, con- 

 taining the dirt, back to the farmer with a letter from the 

 health officer. 



The microscopic examination of milk 



The following report gives a concise and satisfactory 

 summary of the methods used for the microscopic examina- 

 tion of milk and the determination of the dirt in milk. 

 This report was recently presented by Professor Conn to 

 the Commission on Milk Standards of the New York Milk 

 Committee: — 



The microscopic examination of raw milk has been somewhat 

 widely adopted, but apparently only in a few places has it been 

 extensively used. In at least two laboratories where it has been 

 tried, it has been given up as unreliable; but in general those who 

 have used the method most are most enthusiastic as to its value. 



There are two different methods of making a microscopic exam- 

 ination of milk: — 



(a) The use of a centrifugal machine by the Stewart-Slack 

 method. This method involves the centrifugalization of one or 

 two cubic centimetres of milk and smearing of the sediment upon 

 a slide, subsequently staining the same, and is so well known that 

 it is unnecessary to describe it in detail here. It is the method 

 that has been most commonly used. The results of this method 

 vary considerably with details of individual manipulation, with 

 the speed of the centrifugal machine, with the time allowed 

 for centrifugalization, and with other individual factors. As a 

 result, findings of one laboratory cannot be commonly compared 



