The OHOLO Conferences have been convened annually from the Spring of 1956; the wide areas they have covered, from different and overlapping disciplines, can be seen from the following list: 1956 Bacterial Genetics (not published) 1957 Tissue Cultures in Virological Research (not published) 1958 Inborn and Acquired Resistance to Infection in Animals (not published) 1959 Experimental Approach to Mental Diseases (not published) 1960 Cryptobiotic Stages in Biological Systems* 1961 Virus-Cell Relationships** 1962 Biological Synthesis and Function of Nucleic Acids** 1963 Cellular Control Mechanism of Macromolecular Synthesis** 1964 Molecular Aspects of Immunology** 1965 Cell Surfaces** 1966 Chemistry and Biology of Psychotropic Agents (not published) 1967 Structure and Mode of Action of Enzymes** 1968 Growth and Differentiation of Cells In Vitro** 1969 Behaviour of Animal Cells in Culture** 1970 Microbial Toxins** 1971 Interaction of Chemical Agents with Cholinergic Mechanisms** 1972 Immunity in Viral and Rickettsial Diseases*** The participants who attend these Conferences are drawn from dif­ ferent scientific institutions in Israel and from many foreign countries; they are engaged in fields of study which represent widely divergent approaches to biology. Thus a distinguishing feature of the OHOLO meetings has been their multi-disciplinary nature. Published by Elsevier Publishing Co. , Amsterdam (1960). * ** Published by the Israel Institute for Biological Research, Ness Ziona. *** Published by Plenum Press, New York (1972). ix PREFACE x These small international conferences are also characterized by their relaxed atmosphere, with ample time for informal as well as formal discussions.