During the summer after his first year at Dartmouth, Lilly returned to Pasadena to participate in an experiment with his former Caltech biochemistry professor Henry Borsook. The purpose of the experiment was to study the creation of glycocyamine, a major source of muscle power in the human body. The experiment involved putting Lilly on a completely protein-free diet while administering measured doses of glycine and arginine, the two amino acids that Borsook hypothesized were involved in the creation of glycocyamine. The experiments pushed Lilly to extreme physical and mental limits; he became increasingly weak and delirious as the weeks went on. The results of the experiment confirmed Borsook's hypothesis and Lilly's name was included among the authors, making it the first published research paper of his career. It was also one of the first instances of a lifelong pattern of experimenting on his own body to the point of endangering his health.