generally ruled out because they fail to explain relief of bends pain (type 1) by recompression. Much experimental evidence is quoted and arguments are elaborated which indicate that the critical site of activity by gas during bends is in connective tissue, probably within tendons. Available data lead the author to conclude that, although arterial gas emboli are rare, they may account for the cerebral symptoms (type 2) seen with decompression . The possible methods of gas formation and the manner of producing decompression symptoms are discussed in detail. Correlation is made between these factors and the methods of prevention, which include use of protecting materials such as diving bells, different types of clothing, programming slow decompression , computing parameters of decompression, or employing pharmacological methods. Liberation of gas from tissues sufficient in form to produce symptoms is dealt with at length. The indication that formation of bubbles is a random process makes mathematical treatment (formation of tables to permit safe decompression at the fastest speed possible) predictably difficult. Use of oxygen, helium, and mixtures of gases is considered, as well as oxygen toxicity which might arise from continued use of high concentrations of oxygen. Development of models has previously been either empirical or mathematical, based on some function such as average diffusion of gas in tissues. These have been helpful but have been inadequate or incomplete in predicting values for new situations (increased depth). The author suggests use ofa "thermodynamic" approach which utilizes concepts that are based on the "worst possible case." This refers to some type of tissue from which nuclei of gas can be rapidly activated, then changed to form symptomatic bubbles, which can then coalesce to distort nerve endings. This book would appear to be a must for anyone involved in sea diving or caisson work. It is valuable for those concerned with flights at high altitude. It is very informative for any physiologist. The material is complete and sound, inasmuch as it presents arguments for and against all the theories mentioned, and the author freely states his own opinions and the reasons why he accepts one theory or another. Tables and illustrations are numerous and well considered. The index is well done. The style is such that, except where mathematics is involved, it reads like a storybook. Robert W. Virtue 727 Birch Street Denver, Colorado 80220 Membrane Fusion. Cell Surface Reviews ser., vol. 5. Edited by George Poste and Garth L. Nicolson. New York: Elsevier North-Holland Publishing Co., 1978. Pp. xxii+862. $120.00. Biological membranes are the barriers which delimit the cell and the subcellular organelles. The fundamental organizational unit of these membranes is a Perspectives in Biology and Meditine · Summer 1979 | 625 bimolecular lipid leaflet. It is this layer that confers on membranes both their great impermeability to most water-soluble biomolecules and their capacity to form closed, self-sealing sacs. A myriad of proteins in association with the lipid bilayer confer the specific functional attributes which distinguish one membrane from another. While it is a vital necessity that the cell surface and organelle membranes retain their integrity and selective permeability, there are times at which one membrane-bound compartment may become pinched in two (fission) or, conversely , when two compartments merge into one (fusion). These processes involve unknown rearrangements in the architecture of the membrane at the transition site. Fission leads to cell division, phagocytosis and pinocytosis (endocytosis ), and the shedding of vesicles, as in the release of enveloped viruses. Fusion permits the union of cells, as in fertilization and the formation of muscle syncytia, fungal plasmodia, and the multinucleated giant cells found in inflammation . Fusion also provides a mechanism by which cells release their vesiclebound products into the extracellular space (exocytosis), as seen in the secretion of hormones, neurotransmitters, and digestive enzymes. These processes are the subject of the present volume. This book is the fifth in a series, entitled Cell Surface Reviews, edited by George Poste and Garth Nicolson. Its 15 chapters treat membrane fusion in a broad and authoritative manner. The tone is scholarly and critical, clearly addressed to researchers in these areas. There are four chapters which consider the basic mechanisms of cell fusion, one from a theoretical viewpoint (D...