THE PRECIPITINS AND THEIR ANTIBODIES 283 



or egg-albumen to 78 C. during 60-90 minutes, their 

 precipitability was lost. But M tiller found that the pre- 

 cipitation by lacto-serum could be restored by the addition 

 of Ca salts, or even that it would not disappear if the 

 milk contained naturally much calcium. Concentrated 

 solutions of urea or formalin destroy the precipitability of 

 egg-albumen as well as the agglutinability of bacteria. 



The precipitate from a mixture of milk and lacto-serum 

 dissolves in a i per cent solution of NaCl. This solution 

 can be precipitated again by rennet or lacto-serum, just 

 as a solution of casein. The treatment with rennet also 

 yielded serum-albumen. Evidently the precipitate is 

 somewhat soluble, and in solution partly dissociated into 

 the two components. At high temperature the free lacto- 

 serum is decomposed and new quantities of lacto-serum are 

 successively formed by the decomposition of the soluble 

 fraction of the precipitate until this is wholly reconverted 

 into casein. M tiller also isolated the lacto-serum from the 

 precipitate through cautious treatment with acetic acid; 

 the liquid obtained by centrifugation of the precipitate, 

 which had been in contact with the acid solution for two 

 hours, contained a noticeable quantity of precipitin. The 

 compound of lacto-serum and casein may be precipitated 

 by the sudden addition of acetic acid. The precipitate dis- 

 solves completely upon neutralisation, but is precipitated 

 by small quantities of a calcium salt. The compound, 

 therefore, probably exists in the solution, but in a partially 

 dissociated state, and gives an insoluble product with 

 calcium or barium salts. Para-casein, prepared by the 

 action of rennet on milk, does not bind the lacto-serum. 



The lacto-serum heated to 70 C. for thirty minutes 



