648 BACTERIOLOGY. 



examine such milk for the presence of both streptococci 

 and pus. This is done by centrifuging a cubic centi- 

 metre of the milk and collecting the sediment on a 

 clean cover-slip and staining with Loffler's methylene- 

 blue. In this manner practically all the sediment derived 

 from one cubic centimetre can be obtained on the cover- 

 slip and a fairly satisfactory estimate can be made of 

 the relative number of pus cells in this quantity of 

 milk as well as at the same time an estimation of the 

 relative number of streptococci. 



Milk that shows pus cells along with distinct chains 

 of streptococci, either extra- or intracellular, is usually 

 regarded as dangerous in character, and boards of health 

 usually direct that the cows from which such milk is 

 derived be excluded from the dairy until such time as 

 the milk is free from these elements. 



