Clio Medica, Vol. 12, No. 1, pp. 33-56, 1977 © B.M. Israel, Amsterdam, The Netherlands Leo Loeb's Role in the Development of Tissue Culture~~ LEWIS PHILLIP RUBIN The cultivation of living tissue outside the organism has had tremendous utility and wide application for the life sciences in the twentieth century. The origins of the technique, and hence of modern tissue culture research, may be traced to Ross G. Harrison's 1907 culture of embryonic frog nerve explants under hanging drops.l His method, once modified as the so-called Harrison-Burrows-Carrel technique, has been adapted for the culture of embryonic, adult and neoplastic tissues of a variety of species and has entered most fields of biological and medical research. The emphasis on Harrison's achievement, which is certainly justified, may, however, obscure the deep-seated nineteenth century concern with explantation and the isolation of parts for studying growth and function. Prior to 1907, there were at least twelve instances of maintenance in vitro or attempted culture of cells or tissues. 2 The work of the German-born American pathologist, Leo Loeb, was one of the more successful of these undertakings. Historical reviews have tended to begin in 1907, or note in passing some of the earlier work. 3 Yet in 1910 Leo Loeb claimed for his own investigations of thirteen years before: To our knowledge ... for the first time the attempt was recorded in the literature to grow tissues of higher animals under artificial environments that differ from those found in the body under natural conditions; to separate experimentally growing epithelium from connective tissue cells. 4 The issue of priority is, I think, a moot one. Loeb, who was always ready to defend the utility of his method, never engaged in a dispute over priority. From the results presented in his papers, one is hard pressed, in fact, to determine whether he achieved merely in vitro tissue survival or true tissue culture. Loeb surely came to the brink of developing a successful method; perhaps he succeeded. But his work was of undeniable significance for defining many of the conditions * I wish to thank Prof. George Rosen for suggesting this topic and providing useful sug­ gestions throughout its writing. I am also grateful to Prof. Merriley Borre! of the University of California, who commented on a draft of this article, and Sally Wilens, Ross Harrison's long-time assistant, who guided me through the Harrison papers at Yale and shared her intimate knowledge of Harrison's career. 33 34 Lewis Phillip Rubin for in vitro growth. His legacy to subsequent researchers in this field was an im­ portant one, and deserves recognition. In addition, Loeb's investigations hold historical interest for the light that they shed on the evolution of experimental techniques during the late nineteenth century. Harrison's explant studies exemplified the incipient "experimental em­ bryology" of the late nineteenth and early twentieth centuries, a trend which ap­ propriately stemmed from the work of Wilhelm His and Wilhelm Roux. An analysis of Leo Loeb's research suggests numerous parallels with the development of experimental pathology in this period and illustrates the relatively high degree of interaction between these two disciplines. It has been long recognized by some investigators that analogies exist among embryonic, regenerative and pathological growth. This has been particularly true in teratology, the natural meeting place between embryology and pathology.5 Importantly, in both fields, the manipulation of tissues by transplantation (in­ cluding grafting) and then explantation were the critical methods for rendering biological growth and differentiation amenable to scientific analysis. It should not be suprising, then, that embryology and pathology were the major avenues to the development and application of tissue culture techniques. BIOGRAPHICAL SKETCH Leo Loeb was born on September 21, 1869 in the small Rhineland town of Mayen, in Germany. Orphaned at the age of six, he was taken by his brother, Jacques, later to become the renowned biologist, to live with his grandfather in Trier. At age ten, he moved to Berlin to board with an aunt and uncle.6 In an autobiographical sketch7, Loeb recalled an early bout with tuberculosis and his generally frail constitution. While in Berlin, his health gradually deteriorated, and he was taken to a resort in Wiesbaden and then to one in Dtirkheim, in the Pala­ tinate, where he remained for several years. After Loeb completed his elementary education in Dtirkheim, he enrolled at the gymnasium in Heidelberg, and spent his summers travelling with his brother. By this time he had become disenchanted with the gymnasium curriculum. He later stated: This emphasis on formal linguistic study with the neglect of literary aspects and the relegation of physics and biology to subordinate positions I found not satisfactory; there­ fore, when I was promoted to the highest class, the Oberprima, I decided to leave the gymnasium and to continue, if possible, my work at the University of Heidelberg, in order to take up studies of my own choice. It was possible for me at the end of one year, to take a state examination, which entitled me to become a regular student at the uni­ versity. I passed this examination successfully in the year 1888 or 1889, so far as I can remember. Then I left Heidelberg to continue my studies at the universities of Berlin, Freiberg, and Basel. In each of these universities I stayed only one semester, in accordance .