Cardiac Physiology for the Clinician

authentic picture on the main directions of activities in this field. However, it is the inclusion of the discussions which is most appreciated. These are valuable because they help us to form a more realistic judgment about the hardness of some hard facts and warn us to respect gaps between facts and conclusions, between conclusions and "'generally accepted theories" of the immune response. One major conceptual achievement of this Conference was the recognition that ". . . in terms of molecular mechanisms involved in activation and regulation by extracellular signals there is no compelling reason to suppose that lymphocytes have devised ingenious tricks beyond the scope of other cells"-as M.F. Greaves put it in his Introduction. In other words, it is realized that the initial response of lymphocytes to environmental signals is basically similar to the hormonal stimulation of target cells (e.g., there is an early response in the concentration of Ca++ and cyclic nucleotides). Similarly, the involvement of microtubules and microfilaments in the transduction of signals that activate lymphocytes is accepted. What makes immunobiology different is the enormous diversity of signals that the immune system as a whole can handle and the correspondingly great diversity of lymphocytes. This conference focused on the diversity of lymphocytes in terms of cell surface markers, determined by the "Immune Response" genes and in terms of enhancing and suppressing T-cell factors. It is this last area of investigation which at the present time is the most accessible to the experimental approach and appears to be the most rewarding. The volume will be of value as a source-book especially to immunologists, biochemists, and cell biologists. J. M. VARGA Department of Dermatology Yale University School of Medicine