This is the introductory volume of a new series to be issued under our general editorship. With the development of an unpre cedented increase in interest in comparative pathobiology, we are of the opinion and intent that Comparative PathobioZogy should become the focal point for the publication of definitive reviews and the proceedings of significant symposia in this area of modern biomedical science. Although the term is now in common use, the question is still sometimes raised as to what "pathobiology" includes. This broad area of modern biology includes but extends beyond traditional pathology. It also encompasses studies directed at understanding the biology, chemistry, and physics of infectious agents, in cluding how they contact and invade the effected organism; the reactions of hosts to such agents, as well as to abiotic invaders; the ecologic parameters which facilitate infection; and the development of tools essential for the understanding of hast pathogen interactions. In other words, pathobiology is inter disciplinary and incorporates all of those aspects of biology, chemistry, and physics which directly or indirectly permit greater understanding of the nature of infectious and noninfectious diseases and the possible implications of such in biomedicine, agriculture, and environmental science. By "comparative" is meant an analytical and critical evaluation of comparable processes as they apply to all categories of animals, invertebrates as well as poikilothermic and homeothermic verte brates."

This represents the third volume of the series entitled Comparative PathobioZogy. The chapters included represent the proceedings of a symposium held at Oregon State University, Corvallis, on August 16-22, 1975. The symposium was co-sponsored by the Society for Invertebrate Pathology (SIP) and the American Society of Zoologists (ASZ). In recent years there has been an impressive increase in interest in comparative immunology, i. e., a comparative approach to understanding how animals, both vertebrates and invertebrates, defend themselves against nonself materials. Ever since Metchnikoff's pioneering studies during the late l800s on the role of phagocytes of invertebrates, which led to his theory of cellular immunity, invertebrates have been employed with increasing fre quency for studying cellular defense. Consequently, it is not surprising that included in the memberships of SIP and ASZ are a large number of individuals with an active interest in this area of research. As indicated by the chapters included in this volume, the animal models employed have been primarily molluscs and insects, although crustaceans and annelids have also been popular."