SIGNIFICANCE 179 



Samples. Cell Count. 



1 . 2 per cent under 10,000 per c.cm. 



7.0 10,000 to 20,000 



61 .0 20,000 to 100,000 



29.0 100,000 to 500,000 



1.8 over 500,000 



Breed and Stidger/^ using the direct method, found varia- 

 tions ranging from 5000 to 20,000,000 cells per c.cm. in milk 

 whcih they regarded as normal. Breed ^^ examined 122 cows 

 which averaged 868,000 cells per cubic centimetre; fifty-nine 

 gave counts under 500,000 per cubic centimetre, 36 between 

 500,000 and 1,000,000 per cubic centimetre, and 27 gave 

 coimts over 1,000,000 per cubic centimetre. 



Hewlett et al.^ found that a change of feed influenced 

 the cell count. As regards physiological influences. Savage ^^ 

 found that the previous number of calves and the age of the 

 cow had apparently little or no effect; just after, calving the 

 leucocytes are increased, but after this condition has subsided 

 the period since parturition has no effect until secretion com- 

 mences to diminish. The cells at this period often show very 

 abnormal values though not invariably so (Breed). Regarding 

 the relative proportion of cells in the fore milk and middle milk 

 the evidence is inconclusive, but it is agreed that there is an 

 increase in the number discharged in the strippings. There 

 are marked daily variations in the number of cells discharged 

 and equally large ones in the product of the four quarters of one 

 cow, for which no adequate explanation has been offered. 

 Pathological conditions may increase the cell content very 

 materially. Savage ^"^ obtained cell counts as high as 368,000,- 

 000 per cubic centimetre in cases of mastitis and in these con- 

 ditions he also found that the relative proportions of the cells 

 approximated to those found in pus. The increased count was 

 particularly due to polymorphonuclear leucocytes which rep- 

 resented 75 to 80 per cent of total number of cells. Even after 

 the clinical evidence of mastitis has disappeared the cell count 

 may continue to be excessive for a considerable period. Some 



