Subsequently, he worked with Martin Freund at Goethe University of Frankfurt and with Franz Hofmeister in Strasbourg. From 1897 to 1898, he served as an assistant to Carl von Noorden, clinician at the City Hospital in Frankfurt. Soon, however, after seeing the high mortality in countless cases of far-advanced tuberculosis and pneumonia, left without any treatment because of lack of therapy, he decided to drop his intention to become a clinician and instead to carry out research in basic medical science, in particular pharmacology. In 1898, he became an assistant of Professor Hans Horst Meyer, the renowned pharmacologist at the University of Marburg. During his first years in Marburg, Loewi's studies were in the field of metabolism. As a result of his work on the action of phlorhizin, a glucoside provoking glycosuria, and another one on nuclein metabolism in man, he was appointed «Privatdozent» (Lecturer) in 1900. Two years later he published his paper «Über Eiweisssynthese im Tierkörper» (On protein synthesis in the animal body), proving that animals are able to rebuild their proteins from their degradation products, the amino acids – an essential discovery with regard to nutrition.