TYPES OF MICROORGANISMS IN MILK 



265 



What do the types signify? 



5. Isolate the different types in litmus milk and note 

 their action. To which group of microorganisms does 

 each type belong? (See Marshall's Microbiology, pp. 

 306-313.) Suggest from what source each type may come. 



B. MICROSCOPIC METHOD 



Apparatus. Special capillary pipettes graduated to 

 deliver exactly 0.01 c.c.; clean glass slides; 

 three staining jars; xylol; alcohol, 95%; 

 Loeffler's alkaline methylen blue; stage 

 micrometer; eyepiece micrometer for 

 counting objects in microscopic field; stiff 

 straight needle. 



Culture: Fresh milk same as used 

 in A. 



Method. 1. Draw with ink a figure 

 the size and shape of an ordinary micro- 

 scopic slide and on either side and equi- 

 distant from the center draw a square 

 whose area is one square centimeter, 

 making the homologous sides of all figures 

 parallel. 



2. Place a clean glass slide on the 

 figure. 



3. With the capillary pipette, drop 

 over the center of one of the smaller 



figures exactly 0.01 c.c. of milk directly FIG. 58. Capillary 

 from the well-shaped sample and with a pl P ette usea in 

 stiff straight needle spread this drop of 

 milk exactly over the area (one square 

 centimeter) covered by this figure. 



4. Make a duplicate smear, placing 

 the drop of milk containing 0.01 c.c. on 

 the slide over the remaining small square. 



5. These smears may be dried by the use of gentle 



the Microscopic 

 Method for 

 Counting B a c - 

 teria in Milk. 

 Note the straight 

 narrow bore and 

 the square tip. 



