SEDIMENT. 



389 



putting the rod (which had been sterilised) into a bottle con- 

 taining sterilised milk, the latter acquired the same property 

 in twenty-four hours. The milk was " ropy." 



PROBLEM VIII. To determine the nature of sediment. 



In cases of this description, the milk should be placed in tubes 

 and centrifuged ; as much milk as possible must be decanted, 

 distilled water added, and the tubes again centrifuged ; this 

 procedure should be repeated till the water is clear. The sedi- 

 ment is examined microscopically (Fig. 40). 



Fig. 40. Microscope. 



Vegetable cells, if clear and sharply denned (Fig. 41), are 

 usually due to the bark of hay and the dust of cake given to the 

 cattle during feeding time. If indistinct and stained yellowish 

 or brownish, these usually indicate cow-dung (Fig. 42). 



