The range of concentration of residual nitrogen in twenty-three specimens of cortical bone that had been extracted with ethylenediamine was found to be 0.0109 to 0.0173 per cent.

The concentration of nitrogen remaining in bone after fifty hours of extraction with ethylenediamine was not greatly reduced by more prolonged extraction; the concentration of the nitrogen does not appear to be a predictable function of extraction after fifty hours.

There was no evidence to indicate that nitrogen-free bone might be prepared by extraction with ethylenediamine without modifying the solvent.

Analyses of the acid hydrolysates of four specimens of ethylenediamine-extracted cortical bone by the Van Slyke method for the determination of amino-acid carbon dioxide indicated that 42 to 50 per cent of the residual nitrogen was present as amino acids. An analysis of the alkaline hydrolysate of one cancellous specimen of the ethylenediamine-extracted bone by an automatic amino-acid analyzer indicated that 39 per cent of the residual nitrogen was present as amino acids. The results of these two methods of analysis indicate that 40 to 50 per cent of the residual nitrogen present in bone after extraction with ethylenediamine is present as protein or protein fragments.