This essay on the trophic function of the lymphoid elements serves to place "on the record" the author's view that lymphoid cells, in addition to their immune functions, play a major role in the "feeding" of the body, through the production of components of plasma as breakdown products or secretion products of lymphocytes. Thus, whether 1 or 1,000 copies are sold, the author's purpose is served; he is placing before the scientific community his many years of study on this hypothesis. It is always refreshing to see someone take a new look at a much studied area. And, in reading this book, one recognizes the great expenditure of time and thought. The book needs critical reading by those closely involved in research immunology. One only hopes that they will read it objectively, without rejecting the thesis before they begin. Some (or all) of it might be correct.