This volume is the third in the series devoted to Antibiotics initiated by Springer Verlag in 1967. The first two volumes were devoted to the Mode of Action of Antibiotics and Biogenesis, respectively and were received graciously. During the intervening years these two works have been used often by research workers and students alike and have been quoted extensively. Although a number of other excellent treatises on antibiotics have appeared, the Springer series has set a standard for thoroughness and quality that meets the need of the scientific community. It is against this background that the present Editors set about the preparation of a third volume in the Series on Antibiotics. Since the appearance of Volume I, also dealing with Mechanism of Action, tremendous strides have been made in the depth and breadth of our knowledge of molecular biology, microbial chemistry and molecular pharmacology and of their direct application to studies on the mode of action of drugs. The field of molecular biology itself was in its relative infancy during the preceding decade and the unique role played by many anti biotics in the development of our understanding of nucleic acid synthesis and function and its relationship to protein synthesis and cell physiology has led rapidly to a very precise, understanding of how many of these same antibiotics inhibit susceptible cells."

The concept of chemotherapy as originated by Paul Ehrlich is based on the premise that antiparasitic drugs must have two properties: they must first bind to specific structures of the parasite which Ehrlich called chemoreceptors. Subsequent to their attachment to the chemoreceptor and by virtue of this binding they must possess the capacity to kill the parasite. Since the host which is to be cured of an invading parasite also contains a large number of chemoreceptors, that have the potential to bind toxic compounds, the task of the chemo therapist is to identify chemoreceptors of the parasite which are . not represented in the host and to design drugs which bind selectively to them In this context, Ehrlich called. for "the complete and exhaustive knowledge of all the different chemoreceptors of a certain parasite" as a "sine qua non for success in chemotherapy." Paradoxically and in spite of the fact that chemotherapy has become a very advanced and successful therapeutic discipline, few of its tri umphs have been achieved by following Ehrlich's original precepts. On the contrary, in the overwhelming majority of cases, effective drugs have been discovered without any knowledge of their chemoreceptors, and these drugs themselves have conversely been used as tools to study the nature of the chemoreceptors involved. In other words: chemother apy, notably antibacterial chemotherapy, has been successful without ever living up to the fundamental standards put forward by Paul Ehr lich."