176 CELLS, DIRT AND DEBRIS 



elements to settle to the bottom of the cell while the few fat 

 globules in the Hquid rise to the surface. This method permits 

 of the differentiation of the cells from the small fat globules in 

 the liquid so that a distinct microscopic observation can be 

 made. 



Examination of Material. The preparation is examined 

 in an unstained condition. The count is made with a 1-inch 

 eyepiece and i-inch objective. Where the number of cell ele- 

 ments exceed 12 or 15 per microscopic field, one-fourth of the 

 entire ruled area of the counter, equivalent to 100 of the smaller 

 squares of the cell, is counted. Where the cell elements are 

 less abundant, one-half of the entire area (two to four hundred 

 squares) is examined. The average number of cells per smallest 

 square is then obtained, which when multiphed by 200,000 gives 

 the number of cells per cubic centimeter in the original milk: 

 multiplication by four million gives the number of cells per cubic 

 centimetre in the sediment examined. As the sediment repre- 

 sents the concentration of cells into one-twentieth of the orig- 

 inal volume of milk taken (10 c.c. to one-half c.c.) this number 

 should be divided by twenty to give the number of cells per 

 cubic centimetre in the original milk. 



Expression of Results. All results should be expressed in 

 number of cells per cubic centimetre of the original milk, and, 

 in order to avoid fictitious accuracy and yet to express the 

 numerical results by a method consistent with the precision of 

 the work, the rules given below should be followed : 



Numbers of Cells per c.cm. 



From 



1,000,001 10,000,000 100,000 



Savage, in 1905, independently worked out a volumetric 

 method based upon the same principle as the Doane-Buckley 



