io6 



Scientific Proceedings (8i). 



tions over a period of a month with the substances and in the 

 manner and dosage as follows: 



"Racemized" casein, No. 869 — One 100 mg. dose intraperitoneally and seven 

 100 mg. doses intravenously. 

 No. 670 — Five 100 mg. doses intraperitoneally and three 100 mg. doses 

 intravenously. 



Nos. 849 and 850 — Five 100 mg. doses intraperitoneally and four 100 mg. 



doses intravenously. 

 No. 871 — Previously immunized with casein and high titer serum obtained. 



Eight days after the last injection the animals were bled and 

 fixation experiments carried out in the usual manner, using one 

 fourth of the minimum inhibiting dose of antigen and 1.5 units of 

 alexin. The serum of animals immunized with casein gave positive 

 tests with quantities of serum less than 0.02 cc. (titration not 

 carried to limit) ; the sera of animals injected with racemized 

 casein were negative in doses which themselves were not inhibitive 

 on omission of the antigen. Similar tests using the heterologous 

 antigen showed no fixation, showing that "racemized" casein is 

 not identical with casein. 



The observation made by Robertson 1 that when a current is 

 passed through a solution of casein a precipitation of casein occurs 

 on the anode, was found to be also true for the racemized product. 

 It must therefore be dissociated. But, as pointed out to me by 

 Dr. Robertson, if Dakin's theory of the ketol-enol conversion 

 be true, we would be compelled to assume that the "racemic" 

 protein dissociates in a different manner than the now generally 

 accepted theory proposed some years ago by Robertson. 2 Accord- 

 ing to his theory the dissociation of the protein salts with inorganic 

 bases and acids is accomplished in the manner 



H" 



— COH = N— + Na OH — CONa + N— . 



I 



OH 



If the " racemization " of casein is due to the oscillation of a labile 

 hydrogen atom attached to the carbon atom, we must either as- 

 sume, if the substance dissociates in the usual manner, that hydro- 



1 Robertson, T. B., J. Phys. Chem., 1911, 15, 179. 



2 Robertson, T. B., /. Phys. Chem., 191 1, 15, 521. 



