Laboratory Exercises 369 
One of each kind of milk at the end of 5 minutes 
One of each kind of milk at the end of 10 minutes 
One of each kind of milk at the end of 15 minutes 
One of each kind of milk at the end of 20 minutes 
Cool all samples to a temperature of 70° and leave standing 
at room temperature and note the changes in appearance during 
the next two or three days. This exercise may be repeated, using 
lower and higher temperatures. 
34. Stupy or Mitx Bacteria 
Object. Study of milk bacteria under the microscope. 
Materials. A compound microscope, some microscopic slides, 
some Fuchsin or methyline blue staining solution, and several 
samples of milk at different ages and degrees of cleanliness. 
Directions. With a small wire loop or other instrument smear 
a small drop of milk on a small area of glass slide, being sure to 
spread at least a part of it very thin. Allow this to dry in the air, 
and then cover the smeared milk with a few drops of the staining 
solution. Allow this to act about one minute and then wash off 
till no more stain is removed. Examine under the microscope. 
If the field is too darkly stained, it can be cleaned by putting on 
a few drops of alcohol and washing off immediately. 
35. PREPARATION OF A STARTER CULTURE FOR ButTeR MAKING 
Object. Study of a starter. 
Materials. Six one-quart milk bottles, one kettle or similar 
utensil, 8 to 12 inches deep, one cup, some clean, tough paper, 
some twine, one thermometer, several teaspoons, one culture of 
starter, one quart of good skimmed or whole milk. (Starter cul- 
tures may be obtained from dealers, whose advertisements appear 
in the dairy journals.) 
Directions. 1. Divide the one quart of milk evenly into three 
2B 
