Sequential Medical Trials

of the Ciba Foundation and this volume is an account of their deliberations. Fourteen major contributions and two short contributions were read and discussed. Not one of these was either simple or straightforward, and even after repeated reading the reviewer is certain that he has failed to grasp many of the ideas put forward. Indeed, it seems unlikely that more than 50 or Ioo men in the whole world are really at home in this field. However, it does not follow that this book is of interest only to this narrow circle. The studies on lymphocytes show that little is yet known certainly about their production or survival, yet a few bold spirits have produced models for lymphocyte, plasmocyte and erythrocyte production. There is still doubt whether the lymphoid cells of the thymus are, in fact, the same physiologically as the morphologically indistinguishable cells in the lymph nodes. Great advances have been made in the knowledge of the erythropoietic hormone and it seems possible that before long it will have been isolated in sufficient purity to enable chemical studies to commence. Those working in heematology will find the book fascinating though difficult reading, and it should interest others concerned with cell proliferation, but those working outside this field will probably have great difficulty in understanding some of it. Those of us who are interested and have attempted to understand the work analysed here owe a debt to the editors and publishers who brought the volume out less than a year from the meeting.