BLOOD ; LEUCOCYTES ; PUS-CELLS 303 



" Pus-cells " cannot be distinguished at all times with 

 certainty from normal leucocytes unconnected with 

 inflammatory or diseased conditions. While it is certain 

 that in the case of mastitis and other diseases of the 

 udder, the number of leucocytes in the milk increases 

 very considerably, it is not possible to fix upon a 

 standard based upon number per cubic centimetre which 

 shall be indicative of pus, since in milk from normal 

 healthy animals the quantity is found to be subject to 

 great fluctuation. 



' Usually the presence of many leucocytes accompanied 

 by streptococci has been taken to denote suppuration 

 or unhealthy inflammatory state of the udder, and milk 

 in which both are found in abundance should be con- 

 demned as unfit for domestic use. The nuclei stain 

 easily with methylene blue and are readily observed in 

 stained cover-glass " films " prepared from sediment or 

 centrifuge deposit obtained from milk containing them. 



Ex. 144. Examine microscopically the deposit obtained in 

 the preceding Experiment. 



First pipette off the sodium car- 

 bonate solution : then fill up with 

 distilled water and centrifuge. 

 Pipette off the water to near the 

 top of the deposit. Stir up the 

 latter with a platinum wire ; remove 

 a drop with a platinum loop and 

 spread it as evenly as possible over 

 a j inch square cover slip. 



Allow it to dry in a place free 

 from dust and theft immerse the 

 cover in ether for three minutes : transfer' to absolute alcohol for 

 a minute, and after drying stain for ten seconds with Loffler's 

 methylene blue. 



