Volume XV "Urology in Childhood" was written in 1956/57 and was the first in the series of the Encyclopedia of Urology to appear. This present volume has been constructed as a supplement and the original intention was to deal only with those subjects in which there have been significant advances during the intervening sixteen years. As the work has proceeded, however, it has become evident that there is no aspect of paediatric urology which has not been developed, and no topic which has not been illuminated by many contributions to the literature. Indeed, there has been such a copious flow of publications devoted to children's urinary tract disease that a full review is no longer possible within the compass of a volume of this size: the decision as to what should be left out has therefore been a matter of the greatest difficulty. The choice has been inevit ably arbitrary and many omissions are regretted. The attempt has been made, however, to report the most notable developments of the subject, and perhaps the greatest change in the practice of paediatric urology has been the full integra tion with paediatric nephrology. The team approach to infant disease in particular has led to greatly improved results. I have been fortunate to have Dr. T. M."

Stone in the urinary tract has fascinated the medical profession from the earliest times and has played an important part in the development of surgery. The earliest major planned operations were for the removal of vesical calculus; renal and ureteric calculi provided the first stimulus for the radiological investigation of the viscera, and the biochemical investigation of the causes of calculus formation has been the training ground for surgeons interested in metabolic disorders. It is therefore no surprise that stone has been the subject of a number of monographs by eminent urologists, but the rapid development of knowledge has made it possible for each one of these authors to produce something new. There is still a technical challenge to the surgeon in the removal of renal calculi, and on this topic we are always glad to have the advice of a master craftsman; but inevitably much of the interest centres on the elucidation of the causes of stone formation and its prevention. Professor Pyrah has had a long and wide experience of the surgery of calculous disease and gives us in this volume something of the wisdom that he has gained thereby, but he has also been a pioneer in the setting up of a research department largely concerned with the investigation of this complex group of disorders, so that he is able to present in terms readily intelligible to the general medical reader the results of extensive biochemical investigation in this area.