How Did It Happen? *

O N SEVERAL OCCASIONS, I have been asked how I became interested in the biochemical role of the amino acids. The following is an answer to that question, even though I am fully aware that the source of one’s inspiration or motivation may be of very little significance to anyone else. Indeed, as I write I sense an inner feeling of embarrassment lest the reader think that I attach too much importance to this bit of my life experience. In truth, the matter is discussed merely to set the record straight. From time to time, some of my friends have stated or implied that my interest in amino acids stemmed from the contacts I had with Thomas B. Osborne and Lafayette B. Mendel during the years I was a graduate student at Yale University. This would be a simple explanation, but, perhaps unfortunately, it is totally incorrect. It is true that during the period in question (1907-Il), Osborne and Mendel were engaged in their classical investigations of the growth of animals upon diets containing single, purified proteins; but all of their studies were carried out in the laboratories of the Connecticut Agricultural Experiment Station, and did not involve the graduate students in any way. As a matter of fact, we had little knowledge of the progrem until the findings appeared in print. Perhaps a word about these two remarkable men may be in order for the benefit of those who are not acquainted with their early activities. Osborne, Director of the Station, had succeeded in isolating and purifying several vegetable proteins, particularly those that occur in grains and other seed crops. Some of the proteins, notably edestin, the globulin of hemp seed, were obtained in beautifully crystalline condition. There can be little doubt that Osborne’s proteins were the purest that had ever been prepared up to that time. But he was not content merely to isolate and purify the proteins; his curiosity demanded that he establish their composition as well. Available methods for such work were not very