The relation of serum proteins to antibodies has been the subject of much investigation in the past, and yet there are a number of points which we do not fully understand. The earliest research published in the literature on the subject is by Widal and Sicard (15) in 1897, who concluded that agglutinin is precipitated together with globulin when the immunized serum is treated with magnesium sulphate. In 1899 Winterberg (16) investigated the action of various protein precipitants and found that agglutinin is almost completely precipitated by sodium sulphate and less completely by magnesium sulphate, ammonium sulphate, sodium acetate and sodium nitrate, while only slightly affected by sodium chloride and potassium chloride. He further stated that animal membranes are impermeable to agglutinin, and that when agglutinin is subjected to dialysis lasting more than a month, its loss seldom exceeds 10 per cent.

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