This paper reports research undertaken by the Quarterrnaster Food and Container Institute for the Armed Forces and has been assignied No. 631 in the series of papers approved for publication. The views or conclusions conitained in this report are those of the authors. They are not, to be construed as necessarily reflecting the views or indorsement of the Department of Defense. 2 Presented at the 56th General Meeting of the Society of American Bacteriologists held in HIouston, Texas, April 29 to May 3, 1956.