80 DAIRY LABORATORY GUIDE 



which forms slimy milk; c represents a common 

 coccus form; s represents a streptococcus (forming 

 chains); T represents bacillus typhosus; 1 represents 

 tetragenococci, and 2, one of the lactic acid group. 



Place a drop of water on a clean cover glass by 

 means of platinum wire, then touch the end of the wire 

 in a sample of milk, mix with water on a cover glass, 

 place on clean slide and examine under microscope. 

 The water dilutes the milk enough to make a clear 

 field. Examine for fat globules, bacteria, and leucocy- 

 tes, if present. The latter are from two to ten times 

 larger than fat globules and an irregular outline. Ex- 

 amine samples of skim-milk for fat globules. Make 

 hang-drop slides and examine in the same manner. 

 To find the correct measurements for microscopic 

 work place a micrometer in the eye piece, or ocular, 

 and a stage micrometer (which equals 1-100 mm.) 

 on the stage of the microscope. Determine the rela- 

 tion of the divisions of the former to those of the 

 latter by making the initial lines coincide and count- 

 ing the number of divisions of the stage micrometer 

 that is required to make one of the ocular micrometer. 

 Example: where a J power ocular is used. When 

 13 divisions of ocular equals 5 divisions of the stage 

 micrometer, let A equal stage division, and 0, ocular 

 division. 



13 equals 5 s. 



1 equals -f% s. 



1 s equals .01 mm. 



f s equals .Ol c equals .003846 m.m. 

 T" 



