Massachusetts Institute of Technology, Cambridge, Massachusetts
*Contribution No. 175 from the Department of Biology and Public Health, Massachusetts Institute of Technology, Cambridge, Massachusetts, and Publication No. 94 from the Research Laboratories of Institutum Divi Thomae, Cincinnati, Ohio. The section on isotopic tracers was prepared in full, and those on x-ray studies and infra-red and Raman spectra in part, while the author was on the staff of Institutum Divi Thomae, Cincinnati, Ohio. The kindness of its Director, Dr. George Speri Sperti, in encouraging the author to undertake this project and in placing all possible facilities at his disposal is gratefully acknowledged.
