METHODS OF EXAMINING MILK 



283 



and if streptococci are present. In fresh cows, the sedi- 

 ment is usually of a grayish-white or white color and or- 

 dinarily does not exceed 0.08 per cent; sometimes the 

 sediment is red, which is an indication of the presence of 

 red blood cells. 



In all of these tests the kind of leucocytes should re- 

 ceive attention as well as the number. 

 A preponderance of polymorphonu- 

 clear leucocytes is very significant, 

 since in mastitis three-fourths and 

 more of the cells are of this type. The 

 clumping or grouping of the cells is 

 also characteristic of milk containing 

 mastitis secretion. There is an in- 

 creased number of epithelial cells in 

 the milk of cows affected with mas- 

 titis; in catarrh of the milk cistern, 

 nests of elongated epithelial cells may 

 be observed in the sediment. 



When an excessive number of leu- 

 cocytes is found in market milk, with 

 a preponderance of polymorphonu- 

 clear cells showing the characteristic 

 clumping or grouping, an examination 

 of the herd from which the milk came 



FIG. 3 9.-sediment tube 



.,, -IT T i .1 /> * n the capillary extension 



will usually disclose the presence of * the bottom. 

 mastitis or other suppurative condition. In such cases, 

 however, it must be remembered that leucocytes are in- 

 creased in number in the milk at the beginning and near 

 the end of lactation and following incomplete or delayed 

 milking. Heating milk to 60 C. (140 F.) or above 

 also increases the number of leucocytes in the sediment. 

 When the number of leucocytes in market milk falls 



