In conclusion may warm thanks are due to Dr. E. A. Park for his constant support and helpful criticism throughout the course of these experiments; also to my assistant Miss Ruth Teasdale for skilled and conscientious help in tedious routine work. I should like also to thank the anonymous donor of the Gift Fund of Yale University whose generosity has defrayed the cost of this research. My thanks also are due to Dean G. H. Whipple for the hospitality of the laboratories in the Medical School of the Universityof Rochester, where these expeinents have been carried out.