Human milk negative to Arakawa's reaction is generally milk from a B-avitalninotic body as shown by a number of papers from our Laboratory. Viewed from the chlorine content of human urine, the Arakawa-negative' mother shows an essentially lower content. And it is evident from the above cited literature that a B-avitaminotic body shows lower content of chlorine in urine. It is very probable that, viewed from the chlorine content of mother's urine, the Arakawa-negative human milk will pass for a B-avitaminotic milk even to the exclusion of other possibilities.