198 MILK HYGIENE 



cate whether a sample of the milk should be taken for 

 analysis. The transparency of milk is dependent partly 

 on the size and nmnber of the fat globules, and partly on 

 the casein in solution. As milk with fewer, but large, fat 

 globules has not the same transparency as milk with 

 more, but smaller, ones, even if the fat per cent, be the 

 same, it is evident that these methods of examination 

 may give misleading results. 



Feser's lactoscope is the simplest and best instru- 

 ment made for this purpose. As Fig. 18 shows, it con- 

 sists of a glass tube which narrows toward the bottom 

 and is closed with a metal cap which supports a short 

 vertical glass column on which are six black lines ; the 

 upper part of the glass has divisions marked with a 

 double row of figures. Four c.c. of milk to be examined 

 are poured into the tube, then enough water is added 

 so that it will reach figure 40 (that is, 36 c.c. of water) ; 

 the fluid is now mixed by shaking. If it is not possible 

 to see the lines on the glass column inside the tube, a 

 little water is added and the tube is again shaken ; this is 

 continued until the lines become visible. When they can 

 be seen through the diluted milk, the fat per cent, can 

 be read from the scale. For example, if so much water 

 has been added that the fluid reaches figure 60 (60 c.c. 

 water and milk), then the milk has 3 per cent. fat. As 

 already stated, this result cannot be relied upon ; in the 

 examination of skimmed milk, quite too high a per- 

 centage of fat is always indicated and, in regard to 

 whole milk, the test may show from 0.5 per cent, to 1 

 per cent, too much or too little. 



On account of the unreliability of this method in 

 many places this preliminary test is no longer used and 

 the inspectors take samples, without preliminary inspec- 

 tion, for examination in the laboratory. 



[In the use of the lactoscope, the individual coefifi- 



