Sentence:  The cells were washed three times with saline , anti human serum was added , the cells were resuspended , and the <WSD>mixture</WSD> was centrifuged at 1000 rpm for 1 min and examined for agglutination . 
Meaning of the word marked with <WSD> tags:  (chemistry) a substance consisting of two or more substances mixed together (not in fixed proportions and not with chemical bonding)